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Available online at

ScienceDirect www.sciencedirect.com Chirurgie de la main xxx (2014) xxx–xxx 1

Recent advance

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Carpal tunnel syndrome

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Le syndrome du canal carpien

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M. Chammas

Q1

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Service de chirurgie de la main et du membre supérieur, chirurgie des nerfs périphériques, hôpital Lapeyronie, CHU de Montpellier, avenue Doyen-Gaston-Giraud, 34295 Montpellier cedex 5, France

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Received 27 August 2013; received in revised form 31 October 2013; accepted 11 November 2013

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Abstract

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Carpal tunnel syndrome is the commonest entrapment neuropathy and is due to combined compression and traction on the median nerve at the wrist. It is often idiopathic. Although spontaneous resolution is possible, the usual natural evolution is slow progression. Diagnosis is mainly clinical depending on symptoms and provocative tests. An electromyogram is recommended preoperatively and in cases of work-related disease. Medical treatment is indicated early on or in cases with no deficit and consists of steroid injection in the canal or a night splint in neutral wrist position. Surgical treatment is by section of the flexor retinaculum and is indicated in resistance to medical treatment, in deficit or acute cases. Miniinvasive techniques such as endoscopic and mini-open approaches to carpal tunnel release with higher learning curves are justified by the shorter functional recovery time compared to classical surgery, but with identical long-term results. The choice depends on the surgeon’s preference, patient information, stage of severity, etiology and availability of material. Results are satisfactory in 90% of cases. Nerve recovery depends on the stage of severity as well as general patient factors. Recovery of force takes about 2–3 months after the disappearance of ‘pillar pain’. This operation has a benign reputation with a 0.2–0.5% reported neurovascular complication rate. # 2014 Published by Elsevier Masson SAS.

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Keywords: Carpal tunnel syndrome; Median nerve compression; Surgery; Endoscopy

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Résumé

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Le syndrome du canal carpien, le plus fréquent des syndromes canalaires, est dû à des mécanismes combinés de compression et traction du nerf médian au poignet. Il est le plus souvent idiopathique. Bien que des régressions spontanées soient possibles, une aggravation lente est observée le plus souvent. Le diagnostic est avant tout clinique, reposant sur les symptômes et les tests de provocation. Un examen électroneuromyographique est recommandé en période préopératoire ou en cas de maladie professionnelle. Le traitement médical est indiqué de première intention dans les formes non déficitaires et repose sur l’infiltration intracanalaire de corticoïdes et/ou une orthèse d’immobilisation nocturne en rectitude du poignet. Le traitement chirurgical qui comprend la section du rétinaculum des fléchisseurs, est licite en cas de résistance au traitement médical, dans les formes déficitaires ou dans les formes aiguës. Les techniques mini-invasives (endoscopie, mini-open) aux courbes d’apprentissage plus longues semblent créditées d’une récupération fonctionnelle plus précoce par rapport à la chirurgie classique, mais avec des résultats identiques à long terme. Le choix dépend du chirurgien, de l’information du patient, du stade de gravité, de son étiologie et de la disponibilité du matériel. Les résultats sont satisfaisants dans près de 90 % des cas. Rapidité et importance de la récupération neurologique dépendent du stade de gravité et du terrain. La récupération de force demande deux ou trois mois après régression des douleurs de type pillar pain. Cette chirurgie à la réputation de bénignité a 0,2 à 0,5 % de complications majeures neurovasculaires. # 2014 Publié par Elsevier Masson SAS.

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Mots clés : Syndrome du canal carpien ; Compression du nerf médian ; Chirurgie ; Endoscopie

E-mail address: [email protected]

1. Introduction

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Carpal tunnel syndrome (CTS) is the commonest entrapment neuropathy and is due to combined compression and

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1297-3203/$ – see front matter # 2014 Published by Elsevier Masson SAS. http://dx.doi.org/10.1016/j.main.2013.11.010

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traction on the median nerve at the wrist. It was first described by James Paget in 1853. In 1913, Marie and Foix published the first description of a neuroma proximal to the flexor retinaculum (FR). The first surgical release of the FR is attributed to Galloway in 1924 [1]. The prevalence of CTS is estimated between 4 and 5% of the population especially between ages 40 and 60 [2]. In 2008, 127,269 people over 20 years were operated for CTS in France, i.e. an incidence of 2.7/1000 (women 3.6/1000, men 1.7/1000) [3]. There were two peaks of frequency, the first and highest between ages 45 and 59 including 75% women, and the second between ages 75 and 84 including 64% women. Since 1999, when 101,900 were operated, an annual rise of 2.8% has been reported. The cost of surgery supported by the social security in 2008 was 108 million Euros. For people aged 18 to 85 with primary operation the global cost of time off work was 81 million Euros, 42 of which were for work-related disease. The duration of leave exceeded 56 days for 38.9% of cases after open surgery, and 71.2% exceeded 28 days after endoscopic release (32.8% of which exceeded 56 days).

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2. Anatomy

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2.1. Flexor retinaculum

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The carpal tunnel is an osteofibrous outlet [4], which is not extensible and defined as the space between the FR, which forms its ceiling, and the carpus its floor. It is medially limited by the hook of hamate, triquetrum, pisiform and laterally by the scaphoid, trapezium and the septum of the flexor carpi radialis (FCR) tunnel. The floor is formed by the capsule and the anterior radiocarpal ligaments covering the adjacent parts of the scaphoid, lunate, capitate, hamate and trapezium. The FR is composed mainly of transverse fibers and has three parts [5] (Fig. 1):

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Fig. 1. The three portions of the FR as described by Cobb [5]. 1. Proximal part thickening of the deep layer of the antebrachial fascia at the distal radius. 2. Intermediate part, characterized by its bony insertions: the pisiform and the hook of hamate on the ulnar side, the scaphoid tubercle and the tubercle of the trapezium on the radial side. 3. Distal fascial part extending between thenar and hypothenar muscles. Les trois portions du RF d’après Cobb [5]. 1. Partie proximale, épaississement du feuillet profond du fascia antébrachial en regard de la partie distale du radius. 2. Partie intermédiaire ou LTC, caractérisée par ses insertions osseuses : du côté ulnaire le pisiforme et l’hamulus de l’hamatum ; du côté radial, le tubercule du scaphoïde et le tubercule du trapèze. 3. Partie distale aponévrotique tendue entre muscles thénariens et hypothénariens.

 the proximal part is a thickening of the deep layer of the antebrachial fascia at the distal radius. This leaflet is prolonged deep to the FCR, flexor carpi ulnaris (FCU) and the ulnar bundle to surround only the 9 flexor tendons and the median nerve;  the intermediate part or transverse carpal ligament (TCL) is characterized by its bony insertions: medially to pisiform and hook of hamate and laterally to the tubercles of the scaphoid and the trapezium;  the distal aponeurotic part extends between the thenar and hypothenar muscles. These two last portions represent the ‘classic’ part of the carpal tunnel. The surface landmark of the proximal border of the TCL corresponds to the wrist crease. According to Cobb [5], the TCL starts about 11 mm proximal to the capitolunate interval and the carpal tunnel ends about 10 mm proximal to the 3rd carpometacarpal interval (Fig. 2). The mean width of the carpal tunnel from the TCL is 25  1.5 mm distally. This gives an hourglass shape. The mean thickness of the flexor retinaculum is 0.6 to 2 mm proximally and 1.6 to 3.6 mm at the level of the hamate.

Fig. 2. Radiographic projection of the three areas of FR described by Cobb [5]; its hourglass shape. Projection radiographique des trois zones du RF d’après Cobb [5] ; sa forme en sablier.

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The flexor retinaculum has four functions:  it represents the first pulley of reflection for the flexor tendons. Its section causes palmar displacement of the flexor tendons at 20–308 wrist flexion and an increase in their excursion of 15 to 25% [6];  mechanical protection of the contents;  base for proximal insertion of thenar and hypothenar muscles;  minor role in transverse stabilization of the carpal arch. Superficial to the FR, there are the longitudinal connective fibers of the palmar aponeurosis – a prolongation of the palmaris longus (PL) tendon if present, radial fibers of the FCU and the superficial part of the antebrachial fascia surrounding FCR, FCU and the ulnar neurovascular bundle [5]. Guyon’s canal is superficial on the ulnar side and partially covers the ulnar border of the TCL (Fig. 3). More distally, the ulnar neurovascular bundle is found medial to the hook of hamate. In some cases, it can be more lateral, which can be

Fig. 3. Position of Guyon’s canal in relation to the FR. At the pisiform, the Guyon’s canal partly covers the FR (A). More distally, it lies medial to the hook of hamate (B). Position de la loge de Guyon par rapport au RF. Au niveau du pisiforme, la loge de Guyon recouvre en partie le RF (A). Plus distalement, elle se situe médialement à l’hamulus de l’hamatum (B).

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accentuated by wrist extension risking error of approach in endoscopic surgery or direct injury in open surgery.

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2.2. The contents of the carpal tunnel

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The median nerve is accompanied by the four tendons of the flexor digitorum superficialis muscle (FDS), the four tendons of the flexor digitorum profundus (FDP) and the flexor pollicis longus (FPL) tendon. The FPL tendon is the most radial element, the median nerve most palmar. Proximal to the canal, the median nerve is located either just dorsal to PL or between FCR and PL. In neutral position of the wrist, the median nerve is either superficial to the FDS tendon of the index, or between FPL and FDS of the index or palmar to the FDS tendon of the middle finger. At the distal part of the canal, the median nerve divides into six branches: the thenar (recurrent) motor branch, the three proper palmar digital nerves (radial and ulnar to the thumb and radial to the index) and the common palmar digital nerves to the 2nd and 3rd spaces. The flexor tendons are surrounded by synovial sheaths:

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 a common synovial sheath of the long finger flexor tendons which extends beyond the upper border of the FR and often communicates with the synovial sheath of the little finger flexor;  a radial digito-carpal synovial sheath surrounds the FPL.

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2.3. Anatomical variations

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These may explain variations in symptoms and present a risk of iatrogenic injury during surgery.

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2.3.1. Anatomical variations in nerve 2.3.1.1. Bifid median nerve with high division. Bifid median nerve with high division (1 to 3.3% of cases) may be present alone or associated with a persistent median artery [7].

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2.3.1.2. Thenar (recurrent) motor branch. Lanz has described five types [8] (Fig. 4): the commonest is the extra-ligamentous form (46%), under the ligament (31%), the transligamentous form (23%) and two rare forms: one where the thenar branch arises from the ulnar side of the median nerve and crosses it at the thenar muscles, and the other (9%) where the thenar branch is superficial to the FR. Kozin found in 4% of cases there were multiple motor branches with one of them crossing the FR every time [9]. The fascicles making up the thenar branch are located in the radial portion of the median nerve in 60% of cases, palmar in 20% and central in 18% of cases [10]. The thenar branch passes through a separate tunnel before entering the thenar muscles in 56% of cases. These variations may explain the variable motor deficit in severe compression of the median nerve [10].

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2.3.1.3. Palmar branch of median nerve. Usually the palmar branch arises 4–7 cm proximal to the flexion crease of the wrist and travels for 16 to 25 mm beside the median nerve, then enters a tunnel formed by the fascia on the medial edge of the

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Fig. 4. Variations of thenar (recurrent) motor branch of the median nerve according to Lanz [8]. Extra-ligamentous form (A). Subligamentous form (B). Transligamentous form (C). Origin at the ulnar side of the median nerve and crossing the nerve at the thenar muscles (D). Course superficial to FR (E). Variations du rameau moteur thénarien du nerf médian d’après Lanz [8]. Forme extra-ligamentaire (A). Forme sous-ligamentaire (B). Forme transligamentaire (C). Naissance du côté ulnaire du nerf médian et croisement de celui-ci en regard des muscles thénariens (D). Trajet superficiel par rapport au RF (E).

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FCR to emerge 8 mm proximal to the flexion crease of the wrist and innervate the skin over the thenar eminence. The palmar branch can cross the TCL or travel ulnar to the median nerve.

2.3.2. Vascular anatomical variations: Persistent median artery This embryonic remnant is observed in 1–16% of dissections or operations [14]. A persistent median artery of at least 3 mm in diameter was noted by Doppler in 26% of asymptomatic patients (6% cases were bilateral) [15]. A bifid median nerve may be associated.

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2.3.3. Muscle and tendon variations [16] 2.3.3.1. Palmaris longus muscle variation. The PL may run inside the carpal tunnel to insert on its deep surface, is called palmaris longus profundus, and can cause a constriction of the median nerve. A reversed PL with an intracanalicular muscle body may be present, called palmaris longus inversus.

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2.3.1.5. Communicating branches Sensory and motor communicating branches (CB) with the ulnar nerve exist. 2.3.1.5.1. Palmar communicating branch of Berretini. This sensory CB is found in 67–92% of cases deep to the superficial palmar arch and is responsible for changes in the sensory territory at the ulnar side of the middle and ring fingers and the radial side of the little finger between the median and ulnar nerves [11–13] (Fig. 5). In some cases, this branch is just distal to the FR, where it may be injured in carpal tunnel release. 2.3.1.5.2. Communicating branch of Riché and Cannieu. This CB is very common (77% to 100%) [12] and is responsible for the distribution of thenar muscles between median and ulnar nerves and can take any of various forms:

2.3.3.2. Flexor digitorum superficialis. The extension of the muscle belly within the carpal tunnel is the most common variation, estimated by Holtzhausen to be 46% in women and 7.8% in men [17].

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2.3.3.3. Lumbricals. The insertion can extend inside the carpal tunnel, with no proven incrimination for median nerve compression [7].

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2.4. Cutaneous innervation of the palm of the hand

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Four nerve branches involved in the innervation of the palm at the thenar and hypothenar eminences are considered at risk in carpal tunnel surgery [12] (Fig. 6). Some of their branches may cross the radial border of the ring finger:

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 the commonest form is a communicating branch between thenar branch of the median nerve and deep branch of the ulnar nerve to the FPB;  CB in the adductor pollicis;  CB between thenar branch and deep branch of the ulnar nerve at the first lumbrical;  CB between a palmar digital nerve of the thumb and the deep branch of the ulnar nerve.

 the palmar branch of the median nerve;  the palmar branch of the ulnar nerve which is inconstant, arising 4.6 cm proximal to the pisiform bone;  the nerve of Henle, nervus vasorum of the ulnar artery, which contributes to the innervation of the hypothenar eminence in 40% of cases;  the transverse palmar branches of the ulnar nerve arising in Guyon’s canal and innervating the skin of the hypothenar eminence and the palm of the hand, distal to the territory of the palmar branch of the ulnar nerve and the nerve of Henle.

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2.3.1.4. Median nerve territory in the hand. The median nerve provides sensory innervation to the palmar aspects of the three radial fingers and the radial half of the ring finger. Dorsally, it supplies the last two phalanges of the index and middle fingers and the radial half of the ring finger. The origin of the palmar branch proximal to the FR explains why the thenar area is spared in CTS. The median nerve innervates the muscles of opposition: the abductor pollicis brevis (APB), opponens pollicis, the superficial head of flexor pollicis brevis (FPB) and the first two lumbricals.

Note that the innervation of lumbricals is similar to that of the FDP.

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Fig. 5. Variations of communicating branch between the ulnar and median nerves in the palm of the hand and implications on territories of sensory innervation described by Don Griot [13]. Type 1: ulnar nerve connections to the median nerve (most frequent): radial digital nerve to the ring finger (42–62%) (A), to the radial digital nerve of the ring finger and ulnar digital nerve of the middle (4–10%) (B), to the third common digital nerve (0–5%) (C), to the radial digital nerve to the ring finger and radial digital nerve to middle (0–7%) (F). Type 2: connections of the median nerve to the ulnar nerve: towards the ulnar digital nerve of the ring finger (0– 4%) (D), to the ulnar digital nerve of the ring and the radial digital nerve of the little finger (0–4%) (G). Type 3: perpendicular connections with unknown destination (0–8%) (E). Crossing of fibers (0–4%) (H). Variations du rameau communicant entre nerf médian et nerf ulnaire à la paume de la main et conséquences sur les territoires d’innervation sensitive d’après Don Griot [13]. Type 1 : connexions nerf ulnaire vers nerf médian (les plus fréquentes) : vers le nerf digital radial du 4e doigt (42–62 %) (A) ; vers le nerf digital radial du 4e doigt et le nerf digital ulnaire du 3e (4–10 %) (B) ; vers le nerf 3e nerf digital commun (0–5 %) (C) ; vers le nerf digital radial du 4e doigt et le nerf digital radial du 3e (0–7 %) (F). Type 2 : connexions du nerf médian vers le nerf ulnaire : vers le nerf digital ulnaire du 4e doigt (0–4 %) (D) ; vers le nerf digital ulnaire du 4e doigt et le nerf digital radial du 5e (0–4 %) (G). Type 3 : connexions perpendiculaire, destination non connue (0–8 %) (E). Croisements de fibres (0–4 %) (H).

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2.5. Surface anatomy

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The proximal border of the FR corresponds to the wrist flexion crease and the median nerve is at the middle of the wrist. Distally, there are two methods to mark the surface anatomy of the superficial palmar arch and the thenar branch:

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 the cardinal line of Kaplan (Fig. 7) from the deepest point of the first web and towards the ulnar border of the hand parallel to the proximal palmar crease. The superficial palmar arch is at least 7 mm distal to the line of Kaplan along the axis of the radial border of the ring finger [18]. The point where the thenar branch penetrates the muscle is between 1 and 15 mm proximally, along the radial border of the middle finger;  Cobb’s landmarks [19] (Fig. 7): they better locate the hook of hamate [20] because they are not affected by any trapeziometacarpal thumb stiffness. The hook lies at the intersection of two lines: one from the pisiform to the proximal palmar crease along the axis of the index, the other joining the middle of the base of the ring finger and the junction middle to medial thirds of the wrist flexion crease. The superficial palmar arch is on average 2.7 cm (1.8 to 4.5 cm) distal to the hook of hamate.

3. Pathophysiology and etiology

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3.1. Structural nerve abnormalities and clinical correlations

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The entrapment neuropathy combines phenomena of compression and traction. Anatomically, there are two sites of median nerve compression:

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 at the proximal edge of the carpal tunnel, caused by wrist flexion and due to the change in thickness and rigidity between the antebrachial fascia and the proximal portion of the FR;  at the narrowest portion at the hook of hamate [12] (Figs. 1 and 2).

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The longitudinal movement of the median nerve in the carpal tunnel was found to be 9.6 mm during flexion [21], 0.7 to 1.4 cm in wrist extension [22]. The median nerve tension varies from 8% depending on the position of the shoulder and 19% depending on the position of the fingers. It can vary from 2.5 to 19.6 mm depending on the position of the shoulder, elbow,

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wrist and fingers [23]. In addition to the longitudinal movement, a transverse movement of the median nerve occurs with wrist position or during finger flexion against resistance [24]. In compression and epineural adhesions, mobility is hindered, creating lesions due to repeated traction on the nerve during wrist movements [21]. Nerve compression and traction may cause disorders of the intraneural microcirculation, lesions in the myelin sheath and

the axon, as well as alterations in the supporting connective tissue. Lundborg proposed an anatomo-clinical classification useful in clinic [25] (Table 1). In so-called idiopathic CTS, several factors are behind the nocturnal increase in intracanalicular pressure:

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 redistribution of the upper limb fluids in supine position;  lack of muscle pump mechanism that contributes to the drainage of interstitial fluid in the carpal tunnel;  tendency to place the wrist in flexion thereby increasing intracanalicular pressure;  increased blood pressure in the second half of the night;  fall of cortisol levels.

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This classification, is simple, but lacks sensitivity. After compression, not all nerve fibers within the same nerve are at the same level of damage, the peripheral fibers are affected before the more central ones, large myelinated ones before smaller ones, and sensory fibers before motor fibers. In chronic CTS, degradation occurs over months or years.

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3.2. Associated pathology

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3.2.1. Polyneuropathy Any polyneuropathy, especially diabetes mellitus, can promote CTS by structural and functional alterations of the median nerve, making it more sensitive to any compression [26].

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3.2.2. Staged nerve compression syndrome ‘‘Double crush syndrome’’ The concept of staged nerve compression described by Upton and Mac Comas [27] is based on the fact that proximal compression of a nerve makes it more sensitive to another more

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Fig. 7. Cardinal line of Kaplan and Cobb’s surface landmarks from Cobb [19]. H: hamate; FCR: flexor carpi radialis; FCU: flexor carpi ulnaris; P: pisiform; TB: thenar (recurrent) branch of the median nerve. Ligne cardinale de Kaplan et repères de Cobb d’après Cobb [19]. H : hamatum ; FCR : flexor carpi radialis ; FCU : flexor carpi ulnaris ; P : pisiforme ; RT : rameau thénarien du nerf médian.

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Table 1 Anatomo-clinical classification of Lundborg [25] for staging the severity of CTS. Classification anatomo-clinique de Lundborg [25] pour l’appre´ciation du stade de gravite´ du SCC. Symptoms

Histopathology

Recovery after decompression

Early stage

Nocturnal

Venous stasis, epineural endoneural edema Slowing of axonal transport

Immediate

Intermediate stage

Nocturnal + diurnal

Permanent anomalies of microcirculation Permanent interstitial edema Connective tissue thickening Destruction of myelin sheath and nodes of Ranvier

Rapid symptom relief (microcirculation is re-established) Repair of myelin sheath (weeks or months) ! persistence of intermittent symptoms some weeks  persistent ENMG abnormalities

Advanced stage

Permanent sensory trouble  deficit of thumb opposition

Wallerian degeneration Reactionary fibrous thickening of surrounding connective tissue

Recovery depends on potential of nerve regeneration Several months delay May be incomplete, persistent ENMG abnormalities

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distal compression by cumulative effects on anterograde axonal transport. Likewise, a distal compression, by alterations in retrograde axonal transport, can promote the emergence of a more proximal entrapment syndrome (‘‘Reversed double crush syndrome’’). This can occur in practice in radicular compression or thoracic outlet syndrome (TOS) associated with a CTS distally.

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3.3. Etiology

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In most cases, CTS is said to be idiopathic. Secondary CTS may be related to abnormalities of the container or the contents. Dynamic CTS is frequently encountered in occupational pathology.

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3.3.1. Idiopathic carpal tunnel syndrome It occurs most often in women (65 to 80% of cases) between 40 and 60 years, bilateral in 50% to 60% of cases [28]. Bilaterality increases with the duration of symptoms. It is related to a fibrous hypertrophy of synovial flexor sheath related to connective tissue degeneration with vascular sclerosis, synovial edema and collagen fragmentation [29]. Metaanalyses [30] showed that sex, age, genetic and anthropometric factors (size of the carpal tunnel) are the most important predisposing factors. Repetitive manual work, exposure to vibration, and cold exposure are minor predisposing factors. Other minor predisposing factors have been identified such as obesity and tobacco. 3.3.2. Secondary CTS 3.3.2.1. Abnormalities of the container. Any condition affecting the walls of the carpal tunnel can cause compression of the median nerve:  abnormal shape or position of the carpal bones due to malunion, carpus or radiocarpal subluxation;  abnormal shape of the distal radius due to fracture with translation of more than 35%, or malunion of the distal radius, metalwork on the anterior surface of the radius;  pathology of the wrist joint such as osteoarthritis, inflammatory arthritis (due to synovial hypertrophy, bone deformity

and/or carpal shortening), infection, basal thumb arthritis, villonodular synovitis;  acromegaly. 3.3.2.2. Abnormalities of content. The abnormalities are:

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 synovial hypertrophy: 358  inflammatory tenosynovitis: inflammatory (rheumatoid Q3 360 arthritis, lupus) or infectious arthritis, 361  metabolic tenosynovitis: diabetes mellitus (abnormal 362 collagen turnover), primary or secondary amyloidosis 363 (chronic hemodialysis with Beta 2 microglobulin deposits), 364 gout, chondrocalcinosis; 365  abnormal fluid distribution: 366  during pregnancy [31,32] CTS occurs in 0.34 to 25% of 368 cases, especially in the 3rd trimester, with deficit in 37– 369 52% of cases, with spontaneous resolution before the 3rd 370 postpartum month in 85% of cases, 371  hypothyroidism is a common etiology, 372  an arteriovenous fistula in the context of chronic renal 373 failure, 374  abnormal or supernumerary muscle: palmaris profundus 375 muscle, intracanalicular position of the belly of FDS 376 muscle or a lumbrical, 377  enlargement of a persistent median artery can cause CTS on 378 effort, 379  intracanalicular tumor: lipoma, synovial tumor (cyst, 380 synovial sarcoma), nerve tumor (schwannoma, neurofi381 broma, lipofibroma), 382  obesity. 383 3.3.3. CTS and occupational pathology The French Table 57c of the general social security scheme and Table 39c of the agricultural security scheme for the recognition of CTS and compression of the ulnar nerve at Guyon’s canal state that: ‘‘Work in the usual way, repeated movements or prolonged wrist extension or hand grip, a carpal stress or prolonged or repeated pressure on the pillar of the hand’’. In 2007, with 40,537 cases, Table 57 of the general scheme of occupational diseases accounted for 75% of reported occupational diseases [33]. CTS is responsible for 37% of

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recognized cases under Table 57 and 27% of all recognized occupational diseases. In addition to the criteria in Table 57c, exposure to cold must be considered as another predisposing factor. 3.3.3.1. Dynamic CTS. The pressure within the carpal tunnel increases in extension and flexion of the wrist. Repetitive movements of the wrist in flexion and extension, finger flexion and forearm supination have been implicated [34]. An entrapment of FDS and FDP muscle mass during extension of the wrist and fingers was found in 50% of cases [35]. 3.3.3.2. CTS and computer work. No increased prevalence of CTS was found in case of computer work more than 15 hours per week, an increased tendency has been shown beyond 20 hours per week [36]. 3.3.3.3. Vibration [34]. Exposure to vibration is a minor contributing factor [30] with histological effects similar to those related to compression.

4.1. Diagnosis, associated pathology and differential diagnosis

443

4.1.1. Symptoms [38] The condition may be unilateral or bilateral. Paresthesias in median nerve territory are described as needles and pins, burning sensation, tingling, heaviness, or electric impulses usually accompanied by pain radiating to the forearm, elbow or shoulder. Of insidious onset, these symptoms are predominantly nocturnal or appear on waking up in the morning, they can also be triggered by unusual daytime activity, or by maintaining a prolonged position of the hand or wrist such as holding a newspaper or telephone or driving. Shaking the hand ( flick sign of Pryse-Phillips) [39] or changing the position relieves the symptoms. At the limits of median nerve territory, the little finger is sometimes involved due to median-ulnar CB, after eliminating ulnar nerve compression at the elbow or proximal cause of compression such as TOS, cervical or spinal cord causes. A decrease of force, morning edema and cold intolerance may be noted. As the compression progresses, paresthesias become permanent leading to clumsiness and dropping objects. In severe forms, sensory deficit perturbs fine movements and thenar atrophy can be observed at this stage, sometimes accompanied by weak opposition of the thumb due to substitution by the ulnar nerve.

445 446

467

471

416

3.3.4. Acute CTS 3.3.4.1. Posttraumatic. This is most common with distal radius fractures, especially with anterior displacement or wrist dislocation. Increased intracanalicular pressure causing acute CTS may also be due to immobilization of the wrist in flexion, excessive distraction by external fixator, or due to crush syndrome [37].

417

3.3.4.2. Non-traumatic [37]. These are rarer:

4.1.2. Provocation tests The median nerve is felt just distal to the flexion crease deep to the PL tendon or midpoint of the wrist:

419

427

 infection and tenosynovitis, flexor sheath infection, abscess or septic arthritis;  hemorrhage with hematoma under pressure by anticoagulant overdose, hemophilia, or von Willebrand disease;  arthropathy, microcrystalline synovitis, tophi;  high pressure injection;  acute thrombosis of a persistent median artery;  burn causing increased compartmental and carpal tunnel pressure.

 Tinel’s test is positive if the patient experiences paresthesias with manual percussion of the palmar aspect of the wrist over the median nerve. The sensitivity is 26% to 79% and specificity is 40 to 100% [40];  Phalen’s test (Fig. 8) is positive if paresthesias appear in median nerve territory on maximum flexion of the wrist with elbow extended for a whole minute. The time taken for the symptoms to appear is noted in seconds. Sensitivity is 67% to 83% and specificity is 47 to 100% [40,41];

428

4. Diagnosis

429

Clinical approach of a patient complaining of acroparesthesia of the hand consists of five steps:

411 412 413 414 415

420 421 422 423 424 425 426

430 432 433 434 435 436 437 438 439 440 441 442

 diagnosis by examination, provocative tests, associated pathology and differential diagnosis;  determine the etiology;  assess the severity of the compression by assessing sensory discrimination using the Weber test and the strength of thenar muscles innervated by the median nerve;  additional tests especially electroneuromyographic examination (ENMG);  propose the appropriate treatment according to severity, etiology, general condition and activity. There is no ‘‘gold standard’’ for diagnosis of CTS.

Fig. 8. Phalen’s test. Test de Phalen.

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468 469

472 473 474 475 476 477 478 479

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9

At the end of this diagnosis, differential diagnosis and associated pathology are considered, the possibilities being:

507

 high clinical suspicion of CTS;  CTS is suspected but accompanied by another pathology: associated compression syndrome such as ulnar nerve at the elbow (rarely at the wrist) may be suspected, or multiple nerve compression syndromes with cervical arthritis;  symptoms evoke another cause such as TOS, cervico-brachial neuralgia or neurological disease.

510 511

4.2. Determining severity: anatomo-clinical classification of Lundborg

517 518

508

512 513 514 515 516

This is determined by the timing of symptoms and 519 neurological deficit using the Weber test of static 2-point 520 discrimination for the pulp, and detection of thenar atrophy 521 (Table 1). Q4 522

Fig. 9. McMurthry’s and Paley’s tests. Test de McMurthry et Paley.

480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506

 test of McMurthry and Paley [42] (Fig. 9) is positive if manual pressure on the median nerve 1 to 2 cm distal to the flexor crease causes pain or paresthesia. Sensitivity is 89% and specificity is 45% [40]. Durkan described a variation with compression over the FR [43], which is more difficult to illicit;  test of compression in wrist flexion [44] where pressure is exerted on the median nerve in the carpal tunnel using two fingers with wrist flexed at 608, elbow flexed and forearm supination. The test is positive if paresthesias appear in the median nerve territory. Sensitivity is 82% and specificity is 99% [44]. According to Szabo, nocturnal acroparesthesia is the most sensitive symptom (96%), the most sensitive test is the direct compression test (McMurtry et Paley) (89%) followed by Phalen’s test and the monofilaments of Semmes Weinstein (83%) then the score of Katz and Stirrat (76%) in the typical form with tingling, burning, heaviness or hypoesthesia with or without pain involving at least two of the three radial fingers excluding the palm and back of the hand. Spontaneous wrist pain or radiating in the direction of the wrist can exist. The combination of four abnormal tests: compression, monofilaments, Katz and Stirrat scores and nocturnal symptoms is correlated with the diagnosis of CTS by a probability of 0.86. If the four tests are normal the probability of CTS is 0.0068. The author thus concludes that ENMG is not often useful is diagnosing moderate or severe CTS.

4.3. Determining etiology

523

Despite frequent ‘idiopathic’ forms of CTS, systematic search for etiology is mandatory (Section 3).

524

4.4. When to request investigations?

526

4.4.1. Electroneuromyography (ENMG) The ENMG consists of a stimulation phase and a detection phase. The stimulodetection shows sensory and motor conduction of the median nerve and highlights any slowing down during the passage through the carpal tunnel. It measures amplitude and duration of motor and sensory evoked potentials. Nerve conduction of the ipsilateral ulnar nerve and contralateral median nerve is also measured. The earliest and most sensitive electrical abnormality is a slower sensory conduction (possibly shown by measuring the distance between the palm and/or fingers and wrist). We can consider that a median nerve conduction velocity of less than 45 m/s in the carpal tunnel is pathological, normal velocity being at least 50 m/s [45,46]. At an advanced stage, there is prolonged distal motor latency between wrist and APB; thus the time between nerve stimulation at the wrist and the onset of a motor potential recorded over APB is greater than 4 to 10 ms for a normal of  3.6 ms, and the muscle shows signs of denervation [46]. Motor latency can be altered without abnormal sensory conduction (3.9% of cases [47]). This isolated motor impairment may be due to a motor branch passing through a separate tunnel in the FR. This examination is operator dependent. Skin temperature and age influence the results. The ENMG may be positive in 0– 46% of asymptomatic subjects and negative in 16–24% of patients with a clinical diagnosis of CTS [48]. In an isolated motor distal latency study, Seror [49] found a sensitivity of 54% and a specificity of 97.5%. In an isolated study of sensory conduction velocity, he found a significantly greater sensitivity of 75–92% and a specificity of 97.5%.

527

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525

528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557

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CHIMAI 862 1–20

10 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 584 585 586 587 588 589 590 591 592 593 594 595 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612

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Thus, the false negative rate is not negligible especially in early disease, where only nerve fibers of small caliber are affected. The addition of ENMG study to clinical provocation tests does not provide significant and reliable contribution to the diagnosis to be recommended in practice [50]. In case of dynamic CTS, ENMG is positive only when the compression reaches a certain degree of severity. Again, the ENMG will not detect early forms. However, normal ENMG almost certainly excludes a severe or moderate form. The ENMG does not return to normal in intermediate and severe forms, despite symptom relief. ENMG does not provide any additional evidence to the diagnosis of SCC compared to clinical assessment when the clinical diagnosis is obvious [51]. Anatomical variations like Martin-Gruber and RichéCannieu can interfere with the interpretation of electromyographic studies. However, the ENMG examination remains a reference in the exploration of CTS. In addition to its medicolegal value, ENMG can confirm the diagnosis, eliminate another disease (cervico-brachial neuropathy or TOS), detect associated polyneuropathy, specify single or multiple compression sites and assess the severity of nerve damage thus guiding the treatment plan. The Working Group ANAES [52] concluded that:  ENMG should follow clinical examination;  ENMG is not essential for the diagnosis of a typical form of CTS;  ENMG is not necessary before steroid injection;  it is recommended in cases of doubt, it is an aid in the differential diagnosis;  it is recommended prior to surgery;  it is required to establish occupational disease recognition. 4.4.2. Imaging 4.4.2.1. Wrist X-rays and carpal tunnel view. Radiology is no longer routinely indicated to diagnose etiology of CTS. PA, lateral or carpal tunnel views of the wrist are useful:  when there is wrist pain, limited mobility, deformity or flexor tendon rupture;  when the medical or history of trauma suggests abnormal tunnel or contents. 4.4.2.2. Ultrasonography. This is an operator- and materialdependent study. In early disease, the median nerve maintains normal morphology: a normal aspect of the nerve does not eliminate CTS. A meta-analysis of 28 series published in 2012 [53] showed an increase in cross-sectional area of the median nerve  10 mm2, reflecting that increased volume proximal to stenosis was the best diagnostic test with sensitivity 87.3% and specificity 83.3%. The ratio (index) of flattening of the median nerve facing the hamate is a reliable criterion. Other signs are notching, nerve edema proximal to the stenosis, decreased mobility during flexion-extension, and the FR bulge. Ultrasound can help diagnose etiology by morphological analysis of

the content, e.g. diagnosis of a persistent median artery thrombosis using Doppler US.

613

4.4.2.3. Magnetic resonance imaging. MRI is rarely indicated but may be useful:

615 616

 in secondary tenosynovitis;  in CTS of the child or young adult to detect intracanalicular muscle abnormality, particularly in cases of CTS upon effort, or an intracanalicular tumor.

618

5. Clinical forms

622

5.1. Evolving forms

623

5.1.1. Regression of CTS The natural evolution of CTS has not been studied in detail and is not an always progression. Changes may be intermittent with periods of calm. In one third of patients symptoms regress spontaneously [54]. According to Padua [55], at 1 year, 34% of patients improved, and 45% were unchanged. Recent onset and young age are favorable prognostic factors. Persistent forms evolve to affect quality of life and can cause irreversible nerve damage [56].

624

5.1.2. Acute CTS Acute CTS often presents with a sensory deficit, possibly hyperesthesia. Posttraumatic forms are the most common. A patient with chronic intermittent CTS may develop acute CTS following trauma with further increase in intracanalicular pressure. CTS can also develop de novo. We must distinguish acute compression where treatment is often surgical, from contusion where medical treatment is preferred [37]. In acute compression, the aggravation and deficit are gradual; in case of a fracture or joint displacement, the soft tissue structures increase in volume. In contusion, the neurological deficit is present immediately, there is no or little displacement and no volume increase of soft tissue structures. A pressure recording apparatus may be used [37]. Diagnosis of the rarer non-traumatic acute CTS may be obscured by etiology. Acute thrombosis of a persistent median artery causing CTS is evoked by the absence of etiological context; spontaneous acute CTS in a young or middle-aged adult suggests this diagnosis. Sometimes a bruise, manual exertion or exposure to vibration is present. Spontaneous acute pain on the palmar aspect of the wrist radiating to the radial fingers and sensory deficit in median nerve territory are reported. A Doppler US – if tolerated – shows a persistent median artery thrombosis often associated with a bifid median nerve. The diagnosis is usually made during urgent surgical exploration.

633

5.2. Associated forms

660

Another entrapment syndrome of the upper limb may be associated with CTS. Acroparesthesia of the fifth finger may

661

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614

619 620 621

625 626 627 628 629 630 631 632

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674 675

create confusion. We must distinguish anatomical variation of compression of the ulnar nerve at the elbow, or more rarely in Guyon’s canal, from TOS or cervical neuropathy. It is important to check the cervical spine and TOS for a multiple nerve compression syndrome which may explain persistent postoperative acroparesthesia. Trigger fingers resulting from increased synovial volume must be sought; they can decompensate postoperatively. Basal thumb arthritis – with inconstant symptoms – is fairly common after 60 years. The coexistence of CTS and Raynaud’s phenomenon is not rare. The differential diagnosis may be tricky since sympathetic signs are sometimes associated with CTS.

676

5.3. Age-related forms

677

686

In elderly patients, a sensory deficit is often associated with a thenar atrophy, which usually affects patient autonomy. In the young patient, we must look for microtrauma or intracanalicular muscle abnormality, which gives symptoms only when using the hand. In children, the causes are usually genetic [57] in mucopolysaccharidosis and mucolipidosis. Other non-genetic causes include macrodactyly and tumors. CTS is rare in adolescents and sports are a contributing factor [58].

687

6. Treatment

688

6.1. Prophylaxis

689

It is essential in occupational pathology and includes the modification of the workplace (height) and tools (gloves,

663 664 665 666 667 668 669 670 671 672 673

678 679 680 681 682 683 684 685

690

11

weight, friction, temperature, shape), automation of certain tasks, slowing down the pace, the introduction of rest periods, and diversification of manual activities (job rotation). Prevention in recreational activities such as sports and crafts should also be considered.

691

6.2. Conservative treatment

696

There is currently a sufficient level of evidence regarding the effectiveness of steroid injections, splinting and oral corticosteroids. Other treatment modalities such as ultrasound, laser, diuretics, vitamin B6, weight loss are controversial.

697

6.2.1. Corticosteroid infiltration It acts by reduction of synovial volume and by direct effect on the median nerve. The main risk is injury to the median nerve, with acutely painful sensation of electric shock, risk of neurological deficit and persistent pain. The other complication is tendon rupture. Our injection point is 4 cm proximal to the wrist flexion crease halfway between the PL tendon and the FCU, which corresponds to the axis of the fourth finger (Fig. 10). Prior local anesthesia is not necessary. After topical antisepsis, the needle is slowly pushed obliquely at 458 to the carpal tunnel. There should be no abnormal resistance. The other hand passively mobilizes the fingers to ensure that the needle is not stuck in a tendon then injection is performed slowly after aspiration. A transient painful reaction can occur for some hours after injection. Injection between FCR and PL may cause median nerve injury given the position of the median nerve. Dreano [59] injects ulnar to PL. Dubert [60] reports the measured location of the median nerve in relation to PL, FCR and FCU, 1 cm

701

Fig. 10. Carpal tunnel injection. Infiltration du canal carpien.

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692 693 694 695

698 699 700

702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720

+ Models

CHIMAI 862 1–20

12 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754

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proximal to the wrist flexion crease and identified a risk zone located 1 cm on either side of the PL tendon. He recommends injecting through the FCR 458 medially and 458 distally. There is no difference at 1 year between injections at the wrist flexion crease and one 4 cm proximal to it [61]. Relief occurs within a few days to 2–3 weeks. Local steroid injection is more effective than placebo injection at 1 month and more prolonged than oral corticosteroids at 2 and 3 months [62]. Temporary relief after local corticosteroid injection is a good prognosis for surgery [63]. Two injections are not more efficient than one. More than three injections are not recommended. The minimum recommended time between two injections is one month. Diabetes mellitus is a contraindication especially if uncontrolled. In intermittent CTS with no deficit, Agarwal et al. [64] found 93.7% improvement clinically and on ENMG at 3 months, 79% at 16 months with 50% ENMG normalization. In a series of patients with or without deficit treated by infiltration and splint for three weeks, Gelbermann et al. [65] reported only 22% were asymptomatic at maximum follow-up of 26 months. The criteria for good prognosis are: symptoms for less than one year, no motor or sensory deficit. Otherwise, failure and recurrence were observed. 6.2.2. Night splint in neutral wrist position The tendency to place the wrist in flexion during sleep increasing the intracanalicular pressure has been implicated in the occurrence of nocturnal symptoms. The position of the wrist splint must be in strict neutral position to decrease this pressure. A splint can be tailored to coexisting pathologies (basal thumb osteoarthritis). Results are similar to those of corticosteroid injection [66]. Stutzmann and Foucher [67] found improvement in moderate CTS in 81% of cases at three years. The duration of treatment is three weeks to three months and can be done while awaiting surgery. The splint may be associated with an injection.

761

6.2.3. Modification of mechanical and ergonomic measures Even temporary reduction of activity often provides relief, especially in CTS after manual overuse. Very few studies have analyzed the ergonomic measures. No significant improvement in symptoms and ENMG findings was found with the use of ergonomic computer keyboards compared with conventional keyboards in patients with proved CTS [68].

762

6.3. Surgical treatment

763

The principle of surgical treatment is to obtain a reduction in intracanalicular pressure by increasing the volume of the carpal tunnel due to the section of the FR. This is usually performed as day case surgery using a tourniquet. The operation is usually unilateral. Three techniques are currently used: open; techniques known as ‘‘mini-open’’; and endoscopic techniques. Surgery with ultrasound guidance is under development and evaluation [69]. Whatever the technique, the procedure must be atraumatic and care must be taken not to place the median nerve in the extension of the scar incision to minimize postoperative epineural adhesions.

755 756 757 758 759 760

764 765 766 767 768 769 770 771 772 773

6.3.1. Anesthesia and carpal tunnel surgery Carpal tunnel surgery can be done under local, locoregional or general anesthesia. In distal anesthesia, tourniquet tolerance is the main limiting factor. Regional median, ulnar and musculocutaneous block is poorly tolerated compared to wrist block. Local anesthesia infiltration into the carpal tunnel associated with subcutaneous injection at the incision (Altissimi and Mancini technique [70]) gives more postoperative relief than the subcutaneous infiltration alone [71]. The tourniquet is inflated after injection. Local anesthesia does not cover flexor tendon synovectomy. Local vasoconstriction by epinephrine in the local anesthetic avoids use of a tourniquet. For endoscopic surgery, distal median, ulnar and musculocutaneous nerve blocks when done 6 cm proximal to the wrist flexion crease, avoid soft tissue infiltration, which is a nuisance for endoscopy. According to Delaunay [72], after 10 min, 9% and 32% of patients required additional anesthesia to the median and ulnar nerves respectively. No postoperative neurological deficit was found. If used, local anesthesia should be injected 20 minutes prior to endoscopic surgery to avoid soft tissue infiltration.

774

6.3.2. The open technique 6.3.2.1. Basic procedure. This is the oldest technique. An incision 3 to 4 cm long from the wrist crease is made in the axis of the radial border of the ring finger (Fig. 11) down to the cardinal line of Kaplan. The medial fat pad is retracted and later repositioned [73] to separate the skin from the FR after surgery. The palmar fascia is then either incised or retracted laterally. Subcutaneous dissection to preserve the sensory branches may create postoperative pain and has not been proven superior to a direct incision of the FR [74]. Hemostasis using bipolar coagulation is performed if needed. FR is exposed using retractors. The hook of the hamate is identified. FR is incised in its ulnar middle portion in the axis of the fourth finger thus providing an ulnar border to limit subluxation of the flexor tendons. The section of FR is cautiously continued distally, guided by the separation of the edges up to the fat that protects the superficial palmar arch and the communicating branch of Berretini. Proximally, the FR is dissected from flexor synovium using scissors, and a grooved probe is introduced along the axis of the fourth finger and that of the forearm to protect carpal tunnel contents. Superficially, the FR and the distal forearm fascia are separated from the subcutaneous tissue along the groove. The skin is retracted. Dissecting scissors are pushed slightly open, under vision, guided by the groove to incise the remaining proximal portion of the FR and the adjacent part of the antebrachial fascia. Complete section is checked by pushing the probe up against the skin while withdrawing it. The radial flap of the FR must be carefully lifted with a hook to see the median nerve, which is the most superficial and radial structure. The content of the carpal tunnel is checked for muscle abnormality and aspect of the synovium. The flexor tendons are retracted laterally to check the floor of the tunnel. Skin is closed without drainage, unless necessary. Comfortable dressing is placed.

796

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Fig. 11. Surgical approaches for conventional open surgery (A) and distal mini-open (B). Voies d’abord chirurgie à ciel ouvert classique (A) et mini-open distal (B).

6.3.2.2. Associated procedures Flexor synovectomy is no longer systematic. A biopsy is 832 justified if secondary synovitis is suspected. If extensive 833 synovectomy is needed, the incision is extended proximally to 834 the distal forearm with a hook in the wrist flexion crease. 835 Epineurotomy of the median nerve is no longer recom836 mended even in cases with deficit. It can be a source of 837 postoperative adhesions. A primary endoneurolysis is not 838 recommended because of the risk of adhesions and devascu839 larization. 840 Q5 6.3.2.2.1. Exploration of the thenar branch. In primary 841 surgery this is justified only in extensive synovectomy, looking 842 for anatomical variations, or isolated or predominant motor 843 deficit where rare specific compression of this branch is 844 suspected. 845 Guyon’s canal release in acroparesthesia of the 5th finger is 846 not recommended in the absence of clinical and ENMG proven 847 ulnar nerve compression at the wrist. Sensory median-ulnar 848 branches may be implicated if there is no compression of the 849 ulnar nerve at the elbow or proximal disease (cervical spine, 850 TOS, spinal cord). Carpal tunnel surgery gives relief of 851 symptoms [75]; after open or endoscopic surgery, the pressure 852 in the Guyon’s canal decreases by two-thirds [76]. 853 6.3.2.2.2. Reconstruction of the FR. The objective is to 854 reduce the duration of postoperative loss of strength, the risk of 855 subluxation of the finger flexor tendons and ‘‘pillar pain’’. 856 Various techniques have been proposed [77]: Z- plasty, VY, 857 zigzag incision with suture of the angles, radial border flap with 858 proximal pedicle or the Jakab plasty, preferred by Foucher [78] 859 where the apices of a distal radially based flap and a proximal 860 flap with ulnar pedicle are sutured, double breasting of the FR. 861 Most of these interventions are not used and their superiority 862 has not been proven (series with methodological bias). One 863 methodologically satisfactory publication of patients with 864 bilateral CTS, where one side was operated conventionally and 865 the other with FR prolongation, showed no difference [79]. 866 More recently, a silicone implant and polyethylene tereph867 thalate sutured to the edges of the FR has been proposed; the 868 authors compared two groups of 400 patients, and found faster 869 recovery of force in the implant group [80], with five implants 870 having had to be removed. 830

831

6.3.2.2.3. Transfer of thumb opposition. In atrophic forms with deficit of opposition, the release of the median nerve is associated with opposition transfer. It is rarely indicated because the FPB receives ulnar innervation, which provides sufficient opposition despite an obvious thenar atrophy. If the opposition is weak, the palmaris longus, prolonged by a part of the palmar fascia, can be used as transfer onto the APB using the Camitz technique [81].

871

6.3.3. The ‘‘mini-open’’ technique These techniques employ incision in the safety zone regarding sensory branches of the median nerve and the ulnar nerve. Various techniques have been proposed:

879

 mini-open incision over the FR [82,83]: A 1 to 1.5 cm skin incision is made at the distal part of the FR from the cardinal line of Kaplan in the axis of the radial border of the ring finger (Fig. 11). The FR is then incised from distal to proximal using scissors under retraction. A series published in 2003 reported results that were no better than those with other techniques, with no reported complications [82];  mini-open with a single incision in the wrist flexion crease: FR is not seen and the absence of interposition bears the risk of iatrogenic damage and/or the incomplete section of the FR. Paine [84] uses a ‘‘retinaculotome’’ to protect the contents of the carpal tunnel. Durandeau uses a grooved probe, making this his preferred technique [85];  mini-open with a double approach, with a distal incision to protect the neurovascular elements: again, the FR is not seen during its section. These include the techniques of Chaise [86] and Bowers cited by Beckenbaugh [87], with an additional proximal incision, a distal incision 1 cm downstream of the hook of hamate using a retractor for protection. Lee and Strickland [88] use a special knife with transillumination.

884

6.3.4. Endoscopic carpal tunnel surgery This surgery was introduced in Japan by Okutsu [89] and in the United States by Chow [90]. The Chow technique includes two surgical incisions. Complications inherent to the distal approach have limited its use in favor of the single approach

905

Please cite this article in press as: Chammas M. Carpal tunnel syndrome. Chir Main (2014), http://dx.doi.org/10.1016/j.main.2013.11.010

872 873 874 875 876 877 878

880 881 882

885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904

906 907 908 909

+ Models

CHIMAI 862 1–20

14 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946

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Agee technique [91] (MicroAire), Centerline1 (Arthrex). Furthermore, placing the wrist in hyperextension in the Chow technique increases intraductal pressure, which can cause acute intraoperative compression of the median nerve. Endoscopic techniques require a longer learning curve and meticulous technique compared to open surgery. Technique of Agee: most often under regional anesthesia, a 1 cm incision is made 0.5 to 1 cm proximal to the wrist flexion crease on the ulnar side of the PL or the middle of the wrist (Fig. 12). The subcutaneous dissection toggles between veins to expose the forearm fascia using two skin hooks. Care is taken not to breach the fascia so as not to injure the median nerve. Dissecting scissors are placed under the fascia and the proximal portion of the FR area. The scissors are spread and the distal pedicle of the FR rectangular flap is cut. A skin hook is used to facilitate exposure and show that the approach is not in the Guyon’s canal. The deep surface of FR is rasped to its ulnar half. Care must be taken to be extrabursal. The intraductal projection of the hook of hamate is felt in the tunnel and the transverse striations of FR are identified. The distal edge of the FR is rasped. Increasing dilators are introduced into the carpal tunnel. The disposable knife is mounted. Sterile anti-fog product can be placed on the endoscope. The knife is lubricated on its deep surface to facilitate its entry. During the slow progress under endoscopic control, the knife is pressed against the deep surface of FR characterized by its striations – used to confirm good position. Rasping should be repeated until there is no interposition. If viewing is not good or the introduction of instrument is difficult, the procedure must be converted to open, and the patient must be informed of this possibility before the surgery. Progression stops when the distal adipose tissue is visible. The FR section starts distally close to the adipose tissue. When both edges of FR recede, the proximal FR flap is cut. The knife is withdrawn and a retractor may be used to lift the fat that invaginates between the edges of the FR, which must be parallel. The FR flap is resected. Wash out, and skin is closed using suture or Steristrip1 without drainage. Comfortable dressing is placed.

Fig. 12. Endoscopic surgery through a single incision (Agee technique). Chirurgie endoscopique à une voie d’abord (technique d’Agee).

6.3.5. Postoperative Whatever the technique, digital mobilization is possible immediately postoperatively. The stitches are removed from the 15th day. Strength activities are reintroduced after three weeks and fully resumed at 6 to 8 weeks. Some authors recommend a postoperative splint for two or three weeks to decrease ‘‘pillar pain’’ [92] and improve FR healing. On the other hand, immobilization may promote postoperative epineural adhesions and limit mobility of the median nerve at the wrist. Contrary to Chaise [93], no superiority to splinting has been Q6 demonstrated by Finsen [94] and Bury [95].

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6.3.6. Results of carpal tunnel surgery 6.3.6.1. Good outcome. In most cases, the outcome is good with disappearance of pain crises and nocturnal paresthesias immediately postoperative (early stage of Lundborg). In case of myelin sheath alterations (intermediate stage), intermittent paresthesia may persist a few days during the period of repair of the sheath. If there was a preoperative deficit (advanced stage), the discriminative sensitivity takes a few weeks to a few months to recover depending on the severity, whereas pulp dysesthesia with contact persists throughout this recovery period. Motor and atrophy recovery is random and usually absent in elderly patients. During FR healing, pain and edema in the area facing the FR section regresses over 4 to 8 weeks and force is recovered in two or three months. The discomfort is even more marked when the patient performs manual forceful labor. The time off work varies according to the type of activity and the surgical technique. In 2001, Chaise [86] evaluated the time off work after carpal tunnel surgery using two incisions without endoscopy and postoperative immobilization of 21 days. For non-employed, the average was 17 days, for those in the private sector 35 days, for public sector 56 days. For patients with sick leave, time off work was 32 days and for those diagnosed as occupational diseases 49 days. Manual workers had 29 days off if non-employed, 42 days for the private sector and 63 days for the public sector.

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6.3.6.2. Prognostic factors. From an analysis of the literature, Turner et al. [96] concluded that the worst results were observed in case of:

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Age is not considered a poor prognostic factor but rather associated with slow evolution.

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6.3.6.3. Comparing open, mini-open and endoscopic surgery. Open or endoscopic surgery is widely used. The

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volume increase in the carpal tunnel is noted regardless of the technique used to cut the FR. After open surgery, an increase in volume of 24.2  11.6% was noted with palmar displacement of contents 3.5  1.9 mm [97]. After endoscopic surgery, increased cross-sectional area was measured at 33  15% [98] (Fig. 13). Safety, efficacy, morbidity, cost, and time to return to preoperative activities were compared. The learning curve is longer for endoscopic surgery. No difference was found between the two techniques at one year postoperatively [99]. However, a number of studies have shown that endoscopic surgery allowed earlier functional recovery especially in the first three months [78,100–103]. Local pain was less noted after endoscopy [104,105]. Eight of 14 studies showed a faster return to work after endoscopy with a difference between 6 and 25 days [106]. However, this remains controversial, other studies having shown no superiority for either technique [107]. Few studies compared endoscopy to mini-open surgery; results were either identical or favored endoscopic surgery regarding postoperative pain [106]. To Wong [108], the technique of Lee and Strickland [88] seems to be associated with less postoperative pain than the endoscopic technique of Chow.

Fig. 13. CT view of retraction of the edges of the FR after endoscopic carpal tunnel release. Vue tomodensitométrique de l’augmentation de distance des berges du canal carpien après chirurgie endoscopique.

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Conventional and mini-open surgery also show very little difference in results with occasional short-term differences in favor of mini-open [106]. The risk of incomplete section of FR is higher in the mini-open [109]. The choice of open, mini-open or endoscopic surgery therefore depends on the choices and preferences of the surgeon [110], the information of the patient, the type of CTS, its etiology and availability of equipment.

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6.3.7. Complications of surgical treatment of CTS 6.3.7.1. Minor complications 6.3.7.1.1. Neuropathic scar pain. The four nerve branches involved in the innervation of the palm (palmar branch of the median nerve, palmar branch of the ulnar nerve, nerve of Henle, palmar transverse branches of the ulnar nerve) (Fig. 6) may be adversely affected by the incision, resulting in scar pain or a neuroma formation. This is not observed after endoscopic surgery. For open surgery, even for the classic recommended extension of the incision along the radial side of the 4th finger, there is no zone of absolute safety, given the overlap of nerve territories [12,111]. Ozcanli justifies the mini-open with a distal incision between the superficial palmar arch and the distal territory of the palmar branch of the median nerve, which presents less risk of damage to the superficial nerve branches [112]. However, it has not been demonstrated that the incision for mini-open is free of such complications [82]. 6.3.7.1.2. Pillar pain [92]. Postoperative pain in the hypothenar eminence and thenar is the rule in the initial phase. There is concomitant edema around the FR. Persistent loss of strength is fortunately less common (1% to 36%) [92,113] and may occur regardless of the type of surgery [82,113]. It is related to pain on forced manual activities at the insertions of hypothenar and thenar muscles, the edges of FR and/or at the piso-triquetral joint. Resolution of edema at the cut FR coincides with relief of pillar pain. It has not been demonstrated that postoperative immobilization prevents this complication [94,95]. Treatment includes immobilization, reduced activities and symptomatic treatment or corticosteroid injection. 6.3.7.1.3. Complex regional pain syndrome type 1. It is less common because of progress in anesthetic and analgesic techniques. The severest forms can be seen after contusion or acute intraoperative compression of the median nerve. 6.3.7.1.4. Instability of ulnar flexor tendons through the cut FR. This is manifested by a sharp pain in the ulnar tunnel radiating to the forearm along the ulnar flexor tendons. A tab of the RF may be left on the hook of the hamate to reduce the frequency. Persistence is rare. It is exceptionally observed after endoscopic surgery because of the size of the endoscope which leaves an ulnar edge of the FR. FR reconstruction theoretically avoids this and may be the treatment if confirmed on imaging.

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6.3.7.2. Major complications These are rare but serious, and even more so since this surgery is common and credited with very satisfactory results in the minds of the general public. In a review of the literature from 1966 to 2001 for open surgery and 1989–2001 for

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endoscopic surgery Benson et al. [114] reported 0.49% serious complications for open surgery and 0.19% for endoscopic surgery. Prevention should be emphasized, particularly in endoscopic or mini-open surgery. 6.3.7.2.1. Nerve complications. Transient neurapraxia may occur (1.45% after endoscopy and 0.5% after open), after partial or total median or ulnar nerve section (0.14% for endoscopy and 0.11 for open) or their branches (0.03% for endoscopy and 0.39% for open) [114]. The common palmar digital nerve of the 3rd space and the cutaneous branches of the common palmar digital nerves of the 3rd and 4th spaces may be affected especially in the double approach endoscopic surgery or the mini-open. This cutaneous branch is between 2.3 and 10 mm from the distal edge of the FR [115]. In case of total or partial nerve section, the results of surgical repair – which must be early – are incomplete, sometimes with residual permanent severe pain. 6.3.7.2.2. Injury to the superficial palmar arch. It is reported in 0.02% of cases [114]. The superficial palmar arch is close to the distal edge of the FR. This may be associated with injury of communicating branch of Berretini or common palmar digital nerve of the 3rd space. The Cobb or the Kaplan method may be used for its identification (Fig. 7). 6.3.7.2.3. Section of the flexor tendons of the fingers. These have been reported only after endoscopic surgery (0.008%) [114].

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6.3.8. Information for patients Preoperative information is a legal necessity, even if it is not well registered by the patient. This may be oral, but difficult to verify, so the best is oral and a written form supplying information and informed consent and including even exceptional complications. A summary of the key elements to include was proposed by Goubier in 2006 [116]. Julliard [117], in his expert experience, noted that nearly three quarters of trials were due to unmeditated, passionate or inappropriate comments amongst colleagues or mismanagement of a crisis situation with the patient. A quarter of procedures were barely justified by technical faults: section of the nerve, infection, unnecessary procedure. . .

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6.4. Therapeutic indications in CTS

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6.4.1. Acute CTS

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6.4.1.1. Posttraumatic CTS. A progressive compression following contusion with symptoms at onset and little edema, is not in principle surgical and must be distinguished. In case of compression without deficit the urgent, simple reduction is often enough to relieve symptoms, to be verified by a careful clinical monitoring with limb elevation. In case of compression with deficit or significant edema without deficit, emergency open surgery is necessary. Shorter operating time is associated with faster recovery [37].

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the forearm, and treatment of etiology. In case of acute thrombosis of a persistent median artery, the artery is excised after release of an often bifid median nerve.

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6.4.2. Subacute or chronic CTS Medical treatment is the first line in early forms. It is less effective in intermediate forms with nocturnal and diurnal acroparesthesia with risk of development of a deficit. It can be tried first or immediate surgical treatment can be offered depending on the context. Surgery is indicated for resistant forms and advanced forms with deficit. The contra-indications for endoscopic surgery include [118]:

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6.5. Persistence of symptoms, recurrence or new symptoms

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In a recent analysis of the causes of secondary surgery for 200 cases operated over a period of 26 months, Stütz et al. [119] found incomplete section of FR in 54% of cases and perineural fibrosis in 32% of cases (anterior scar adhesion in 23% and circumferential fibrosis in 9%) and iatrogenic nerve injury in 6% of cases. In the absence of a proximal cause, reoperation is indicated in three clinical pictures with a frequency varying from 0.3 to 12% [120] (Fig. 14):

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 persistence of symptoms. This is the commonest complication after CTS surgery, mainly due to an incomplete section of FR, most often in the distal portion. The absence of a symptom-free interval, the persistence of symptoms and positive provocation tests are suggestive. ENMG abnormalities may persist despite effective release. However, a normal ENMG eliminates persistent compression. Open revision surgery is justified without the need for modification of median nerve surroundings;  recurrence of symptoms. After a free interval of three months, symptoms may recur either during trauma, e.g. wrist or fracture of both bones of the forearm, inflammatory episode, e.g. flexor tenosynovitis, progressive entrapment after FR scarring with fibrous perineural adhesions, causing a ‘‘traction neuropathy’’ syndrome of Hunter [121]. Recurrence of symptoms and a positive clinical examination suggest a syndrome of epineural adhesions. Again ENMG may be faulty. Procedures to restore gliding between the median nerve and its surroundings are often required; examples are synovial flap [122], hypothenar fat flap [123], pedicle flaps [124], biomaterials [80] or anti-adhesions gel [120];

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Fig. 14. Treatment algorithm in cases of recurrence, persistence, or appearance of new symptoms after carpal tunnel surgery. Algorithme décisionnel dans les cas de récidive, persistance ou nouveaux symptômes après chirurgie du canal carpien.

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 appearance of new symptoms. These are mostly secondary to intraoperative iatrogenic lesions of the median nerve trunk, the thenar (recurrent) branch, palmar digital nerves, the superficial palmar branch or tendons. These complications can occur alone or combined with one of the above clinical presentations. Nerve repair of the terminal branches aims to recover sensitivity and reduce neuropathic pain. In case of neuroma of the palmar branch, a desensitization is indicated and, if unsuccessful, burial. Repair of thenar branch is indicated depending on the presence of functional impairment, age and the potential for regeneration and the site of the lesion. Otherwise palliative tendon transfer surgery is proposed.

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Disclosure of interest

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The author declares that he has no conflicts of interest concerning this article.

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1451 [94] Finsen V, Andersen K, Russwurm H. No advantage from splinting the wrist after open carpal tunnel release. A randomized study of 82 wrists. 1452 1453 Acta Orthop Scand 1999;70:288–92. 1454 [95] Bury TF, Akelman E, Weiss AP. Prospective, randomized trial of 1455 splinting after carpal tunnel release. Ann Plast Surg 1995;35:19–22. [96] Turner A, Kimble F, Gulyas K, Ball J. Can the outcome of open carpal 1456 1457 tunnel release be predicted?: a review of the literature. ANZ J Surg 1458 2010;80:50–4. 1459 [97] Richman JA, Gelberman RH, Rydevik BL, Hajek PC, Braun RM, et al. Carpal tunnel syndrome: morphologic changes after release of the 1460 1461 transverse carpal ligament. J Hand Surg Am 1989;14:852–7. 1462 [98] Kato T, Kuroshima N, Okutsu I, Ninomiya S. Effects of endoscopic release of the transverse carpal ligament on carpal canal volume. J Hand 1463 1464 Surg Am 1994;19:416–9. 1465 [99] Atroshi I, Hofer M, Larsson GU, Ornstein E, Johnsson R, et al. Open 1466 compared with 2-portal endoscopic carpal tunnel release: a 5-year follow-up of a randomized controlled trial. J Hand Surg Am 1467 1468 2009;34:266–72. 1469 [100] Trumble TE, Diao E, Abrams RA, Gilbert-Anderson MM. Single-portal 1470 endoscopic carpal tunnel release compared with open release: a prospective, randomized trial. J Bone Joint Surg Am 2002;84-A:1107–15. 1471 1472 [101] Abrams R. Endoscopic versus open carpal tunnel release. J Hand Surg 1473 Am 2009;34:535–9. 1474 [102] Dumontier C, Sokolow C, Leclercq C, Chauvin P. Early results of conventional versus two-portal endoscopic carpal tunnel release. A 1475 1476 prospective study. J Hand Surg Br 1995;20:658–62. 1477 [103] Macdermid JC, Richards RS, Roth JH, Ross DC, King GJ. Endoscopic versus open carpal tunnel release: a randomized trial. J Hand Surg Am 1478 1479 2003;28:475–80. 1480 [104] Atroshi I, Larsson GU, Ornstein E, Hofer M, Johnsson R, et al. Outcomes 1481 of endoscopic surgery compared with open surgery for carpal tunnel syndrome among employed patients: randomised controlled trial. BMJ 1482 1483 2006;332:1473. 1484 [105] Kang HJ, Koh IH, Lee TJ, Choi YR. Endoscopic carpal tunnel release is 1485 preferred over mini-open despite similar outcome: a randomized trial. Clin Orthop Relat Res 2012. Q8 1486 1487 [106] Scholten RJ, Mink van der Molen A, Uitdehaag BM, Bouter LM, de Vet 1488 HC. Surgical treatment options for carpal tunnel syndrome. Cochrane Database Syst Rev 2007;CD003905. 1489 1490 [107] Ferdinand RD, MacLean JG. Endoscopic versus open carpal tunnel 1491 release in bilateral carpal tunnel syndrome. A prospective, randomised, 1492 blinded assessment. J Bone Joint Surg Br 2002;84:375–9. [108] Wong KC, Hung LK, Ho PC, Wong JM. Carpal tunnel release. A 1493 1494 prospective, randomised study of endoscopic versus limited open 1495 methods. J Bone Joint Surg Br 2003;85:863–8. 1496 [109] Cellocco P, Rossi C, Bizzarri F, Patrizio L, Costanzo G. Mini-open blind procedure versus limited open technique for carpal tunnel release: a 301497 1498 month follow-up study. J Hand Surg Am 2005;30:493–9. 1499 [110] Moreel P, Dumontier C. Chirurgie des syndromes canalaires du poignet. 1500 EMC Techniques chirurgicales – Orthopédie-Traumatologie. Paris: Elsevier Masson SAS; 2007: 44–362. 1501 1502 [111] Martin CH, Seiler 3rd JG, Lesesne JS. The cutaneous innervation of the 1503 palm: an anatomic study of the ulnar and median nerves. J Hand Surg Am 1996;21:634–8. 1504 1505 [112] Ozcanli H, Coskun NK, Cengiz M, Oguz N, Sindel M. Definition of a 1506 safe-zone in open carpal tunnel surgery: a cadaver study. Surg Radiol 1507 Anat 2009;32:203–6. [113] Brooks JJ, Schiller JR, Allen SD, Akelman E. Biomechanical and 1508 1509 anatomical consequences of carpal tunnel release. Clin Biomech (Bristol 1510 Avon) 2003;18:685–93. 1511 [114] Benson LS, Bare AA, Nagle DJ, Harder VS, Williams CS, et al. Complications of endoscopic and open carpal tunnel release. Arthros1512 1513 copy 2006;22:919–24 [24 e1–2]. 1514 [115] Olave E, Del Sol M, Gabriellp C, Mandiola E, Rodrigues CF. Biometric study of the relationships between palmar neurovascular structures, the 1515 1516 flexor retinaculum and the distal wrist crease. J Anat 2001;198:737–41. 1517 [116] Goubier JN, Teboul F, Dubert T. Syndrome du canal carpien : informa1518 tion et consentement eclairé. Chir Main 2006;25:286–92.

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[121] Hunter JM. Recurrent carpal tunnel syndrome, epineural fibrous fixation, and traction neuropathy. Hand Clin 1991;7:491–504. [122] Wulle C. The synovial flap as treatment of the recurrent carpal tunnel syndrome. Hand Clin 1996;12:379–88. [123] Strickland JW, Idler RS, Lourie GM, Plancher KD. The hypothenar fat pad flap for management of recalcitrant carpal tunnel syndrome. J Hand Surg Am 1996;21:840–8. [124] Dahlin LB, Lekholm C, Kardum P, Holmberg J. Coverage of the median nerve with free and pedicled flaps for the treatment of recurrent severe carpal tunnel syndrome. Scand J Plast Reconstr Surg Hand Surg 2002;36:172–6.

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Carpal tunnel syndrome.

Carpal tunnel syndrome is the commonest entrapment neuropathy and is due to combined compression and traction on the median nerve at the wrist. It is ...
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