Level V Evidence
Iatrogenic Medial Patellar Instability: An Avoidable Injury Vicente Sanchis-Alfonso, M.D., Ph.D., and Alan C. Merchant, M.D.
Abstract: Iatrogenic medial patellar instability is a specific condition that frequently causes incapacitating anterior knee pain, severe disability, and serious psychological problems. The diagnosis should be suspected in a patient who has undergone previous patellar realignment surgery that has made the pain worse. The diagnosis can be established by physical examination and simple therapeutic tests (e.g., “reverse” McConnell taping) and confirmed by imaging techniques. This iatrogenic condition should no longer exist and could almost be eliminated by avoiding over-release of the lateral retinaculum.
A
nterior knee pain (AKP) is one of the most common symptoms of patients seeking orthopaedic care. The pain can vary from mild to disabling and can arise from a wide variety of causes. Iatrogenic medial patellar instability (IMPI) is an objective condition with its own characteristics that frequently causes incapacitating AKP and should be included in the differential diagnosis of AKP in patients who have undergone any prior extensor mechanism realignment surgery.1 Certainly, IMPI is a rare condition in the totality of orthopaedic problems, but its clinical importance far exceeds its numbers. IMPI frequently causes severe pain and disability that are difficult to treat successfully. It is especially troubling because almost all of these cases have been caused by patellar realignment surgery that was intended to help AKP or patellar instability in the first place.1-13 Despite the initial study by Hughston and Deese2 in 1988 and other studies that followed, all of which warned about IMPI, and despite articles written later about avoiding this injury, the problem still exists
From the Department of Orthopaedic Surgery, Hospital 9 de Octubre (V.SA.), Valencia, Spain; Department of Orthopedic Surgery, Stanford University School of Medicine (A.C.M.), Stanford, California; and Department of Orthopedic Surgery, El Camino Hospital (A.C.M.), Mountain View, California, U.S.A. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received October 10, 2014; accepted January 22, 2015. Address correspondence to Vicente Sanchis-Alfonso, M.D., Ph.D., Department of Orthopaedic Surgery, Hospital 9 de Octubre, C/Valle de la Ballestera 59, 46015 Valencia, Spain. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/14862/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.01.028
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currently.8-13 Almost all IMPI cases have been caused either by improper patient selection or by overzealous and excessive release of the lateral retinaculum (LR).1 All too often, the pain and disability from IMPI are much worse than the preoperative symptoms for which the operation was performed, causing serious psychological side effects. The percentage of patients with catastrophizing ideas, kinesiophobia, anxiety, and depression is much larger in a group of IMPI patients than in the usual group of patients complaining of AKP.14 Comparing our IMPI patients13 with our previous series of more usual AKP patients,14 we found that the former had higher rates of kinesiophobia (100% v 80%), catastrophizing (41% v 37%), anxiety (59% v 37%), and depression (24% v 11%). Frequently, this type of psychological pathology is overlooked by the orthopaedic surgeon. Most of these patients go from one doctor to another until they find a solution to their problem. In our series on IMPI, patients had to visit more than 3 doctors before being given the correct diagnosis and an appropriate treatment plan. Therefore we believe there is a need to publicize not only the diagnostic procedures for recognizing IMPI but also the surgical principles to avoid this iatrogenic injury in the first place. The purposes of this article are to show how to recognize this serious injury and to review the factors causing IMPI and learn how to avoid them.
IMPIdA Rare Condition Of the 168 cases of medial patellar instability reported in the literature, 153 (91%) occurred in patients who had undergone a previous lateral retinacular release (LRR), either isolated or associated with realignment surgery.13 Of the remaining 15 non-iatrogenic cases
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 31, No 8 (August), 2015: pp 1628-1632
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IATROGENIC MEDIAL PATELLAR INSTABILITY Fig 1. Medial subluxation test according to Fulkerson.15 (A) The patella is held medially in extension (arrow) and (B) then released on abrupt knee flexion. It is a provocative test, and therefore reproduction of symptomatology with this maneuver strongly suggests medial patellar instability. Reprinted with kind permission of Springer Scienceþ Business Media.28
(9%), 8 were the result of trauma and 7 occurred spontaneously.13 Because there is little written about IMPI, we sought to learn the extent of this injury. When IMPI is encountered, its disability is so severe and the treatment so challenging that each patient becomes unique and memorable. Therefore we conducted a simple, informal survey of orthopaedic surgeons who have shown a particular interest in patellofemoral problems. Twenty-four surgeons from the United States, Europe, South Africa, and Australia responded, and the number of IMPI patients they recalled having treated in the previous 5 years ranged from 0 to 20. The majority of these surgeons, 16 of 24, treated 3 or fewer cases, and the remaining 8 surgeons recalled 5 to 20 cases each. The median number of IMPI patients treated was 3 per surgeon in the previous 5-year period. It was evident that the number of these patients seen was largely dependent on each surgeon’s referral base,
practice situation, and locality. The fact that this simple and unscientific survey collected 119 patients, when ideally the number should be 0, points to the need for wider publication and more education regarding IMPI.
Diagnosing IMPI IMPI patients usually present with incapacitating, chronic, and disabling AKP along with serious psychological problems.13 Most of our patients had undergone an “extensive” isolated LRR according to the index operative reports.13 Typically, the patient felt a new pain and new instability after that index surgery that were distinct from, and much worse than, those before surgery. In general, IMPI occurs in the first 30 of knee flexion. IMPI is often overlooked as a cause of symptoms because patients will complain of the patella moving laterally with early knee flexion.
Fig 2. Technique for application of reverse McConnell taping on a patient’s right knee. (A) Protective tape. (B, C) Application of Leukotape (Endura Tape Pty Ltd., Clareville, NSW, Australia). (D) Definitive tape in place. (L, lateral; M, medial; P, patella.)
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V. SANCHIS-ALFONSO AND A. C. MERCHANT Fig 3. (A) An axial stress radiograph of the left knee allows us to detect iatrogenic medial subluxation of the patella (medial displacement of 15 mm). (B) Axial stress radiograph of right knee. Arrows represent the force applied to displace the patella medially. Reprinted with kind permission of Springer Scienceþ Business Media.28
The physical findings are crucial for the diagnosis of IMPI. The most important findings are (1) pain and tenderness at the site of the LR defect; (2) increased passive medial patellar mobility, especially when compared with the opposite normal knee; (3) pain and apprehension when medial stress is applied to the patella; (4) a positive gravity subluxation test4; and (5) a positive Fulkerson relocation test15 (Fig 1). Therapeutic diagnostic tests are also important. A “reverse” McConnell taping can be performed to hold the patella laterally and prevent it from subluxating medially (Fig 2). All of our patients experienced significant relief from their pain with this taping.13 Similarly, application of a patellar brace with the buttress pad or strap on the medial side will minimize or eliminate symptoms of IMPI.1 Finally, stress radiographs16 (Fig 3) and stress axial computed tomography scans17 (Fig 4) will document and quantify IMPI objectively. A comparison of the normal side with the abnormal sidedif possibledis more important than the absolute amount of displacement (Figs 3 and 4).
Preventing IMPI It is clear that extensive release, or over-release, of the LR is a major cause of IMPI.13,18,19 This can be a result of
Fig 4. (A) Axial stress radiograph of right knee. (B) An axial stress computed tomography (CT) scan of the left knee allows us to detect iatrogenic medial subluxation of the patella (medial displacement of 13 mm). Arrows represent the force applied to displace the patella medially. Reprinted with kind permission of Springer ScienceþBusiness Media.1
excessive severance of the LR with transection of the vastus lateralis tendon (Fig 5) or can result from releasing an LR that was already lax, showing poor patient selection. An isolated LRR should never be performed in the face of trochlear dysplasia, patella alta, or hyperelasticity. If the LR is not tight, the surgeon should not release it. The goal of a proper LRR is to normalize the medial glide to 1 to 2 fingerbreadths (1 to 2 quadrants) or to a tilt-up endpoint of no more than 60 to 70 19,20 and never to 90 . The vastus lateralis tendon should never be severed. In a recent study by Pagenstert et al.18 in 2012, the authors causeddinadvertentlydmajor quadriceps atrophy in 36% and IMPI in 57% of patients in their “control group” after over-release of the LR by using the 90 tiltup endpoint (rotational elevation of the lateral patella up to 90 in relation to the epicondylar axis) published by Henry et al.21 26 years previously. However, this cause of IMPI has been known at least since 1995, when Marumoto22 published his study. He stated, “A lateral patellar retinacular release that transects the tendon of the vastus lateralis muscle may result in significant complications.” His summary stated, “Complications of lateral releases include medial patellar subluxation, vastus lateralis muscle atrophy and persistent quadriceps muscle weakness. These are likely due to excessive
1631
IATROGENIC MEDIAL PATELLAR INSTABILITY
Fig 5. In patients with iatrogenic medial patellar instability, we frequently find (A) a sectioned vastus lateralis tendon (red arrow). (B) Reconstruction of lateral retinaculum with iliotibial band (black arrow) and reattachment of vastus lateralis (green arrow).
superior extension through the tendon of the vastus lateralis muscle that eliminates its function as a dynamic lateral stabilizer of the patella, and a major extensor of the knee. Maximizing the inferior extent of a lateral release while preserving the tendon of the vastus lateralis muscle may allow an adequate release of the patella while maintaining the physiologic function of the vastus lateralis muscle.” Unfortunately, many orthopaedic surgeons have attributed these severe adverse complications caused by over-release of the LR to all lateral release procedures. LRR, described by Merchant and Mercer23 in 1974, has been one of the most frequently performed procedures in orthopaedic surgery to treat patients with AKP.24-27 However, IMPI is a rare condition. In our experience an isolated LRR that has been performed properly for the correct indications has never caused an IMPI with severe quadriceps atrophy and disabling pain. Therefore IMPI should be considered an avoidable injury. If the LRR is performed for pain, then the surgeon must be convinced that the tight LR is a major contributing factor for that pain. We believe that the role of LRR is limited to the rare patient with clear signs and symptoms of lateral patellar hypercompression syndrome. LRR is discussed in this report with the understanding and assumption that realignment surgery is rarely indicated until all proper physical therapeutic measures have been exhausted. Such measures can successfully treat about 90% of all patients complaining of AKP.28 LR lengthening has been advocated to prevent postoperative IMPI. Indeed, many years ago, in 1978, when all LRRs were performed in an open manner, Larson et al.29 stated that it is better to lengthen the LR than to release it. Our goal as surgeons is to achieve the best results possible for our patients using the least invasive and safest techniques available. By treating all lateral patellar hypercompression syndrome patients who are candidates for surgery with open LR lengthening, surgeons have turned a relatively simple and low-risk arthroscopic procedure into a longer and more complex open procedure for no measurable advantage.
Because of inappropriate over-releases of the LR in the past, fewer releases are being performed. Therefore one might assume that cases of IMPI would decrease, but this is not the case. With the increased use of medial patellofemoral ligament reconstructions, it has been shown that malpositioning or over-tightening of the medial patellofemoral ligament graft, with or without an LRR, may lead to IMPI.30
Conclusions IMPI is an objective condition with its own characteristics that causes incapacitating AKP. It can be readily suspected in a patient who has undergone previous patellar realignment surgery that has made the pain worse. The diagnosis can be established by physical examination and simple therapeutic tests and confirmed by imaging techniques. This iatrogenic condition should no longer exist and could almost be eliminated by avoiding over-release of the LR, only releasing a tight LR, and focusing on normalizing the abnormal anatomy.
References 1. Sanchis-Alfonso V, Ramírez-Fuentes C, Martínez-Soriano F, Monllau JC, Merchant AC. Medial patellar instability. A little-known cause of anterior knee pain. In: Gobbi A, Espregueira-Mendes J, Nakamura N, eds. The patellofemoral joint. State of the art in evaluation and management. Heidelberg: Springer, 2014;79-92. 2. Hughston JC, Deese M. Medial subluxation of the patella as a complication of lateral retinacular release. Am J Sports Med 1988;16:383-388. 3. Biedert RM, Friederich NF. Failed lateral retinacular release: Clinical outcome. J Sports Traumatol 1994;16: 162-173. 4. Nonweiler DE, DeLee JC. The diagnosis and treatment of medial subluxation of the patella after lateral retinacular release. Am J Sports Med 1994;22:680-686. 5. Hughston JC, Flandry F, Brinker MR. Surgical correction of medial subluxation of the patella. Am J Sports Med 1996;24:486-491. 6. Kramers-de Quervain IA, Biedert R, Stüssi E. Quantitative gait analysis in patients with medial patellar instability
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9.
10.
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12.
13.
14.
15. 16.
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following lateral retinacular release. Knee Surg Sports Traumatol Arthrosc 1997;5:95-101. Sanchis-Alfonso V, Torga-Spak R, Cortes A. Gait pattern normalization after lateral retinaculum reconstruction for iatrogenic medial patellar instability. Knee 2007;14:484-488. Heyworth BE, Carroll KM, Dawson CK, Gill TJ. Open lateral retinacular closure surgery for treatment of anterolateral knee pain and disability after arthroscopic lateral retinacular release. Am J Sports Med 2012;40:376-382. Udagawa K, Niki Y, Matsumoto H, et al. Lateral patellar retinaculum reconstruction for medial patellar instability following lateral retinacular release: A case report. Knee 2014;21:336-339. Saper MG, Shneider DA. Lateral patellofemoral ligament reconstruction using a quadriceps tendon graft. Arthrosc Tech 2014;3:e445-e448. Sawyer GA, Cram T, LaPrade RF. Lateral patellotibial ligament reconstruction for medial patellar instability. Arthrosc Tech 2014;3:e547-e550. Borbas P, Koch PP, Fucentese SF. Lateral patellofemoral ligament reconstruction using a free gracilis autograft. Orthopedics 2014;37:e665-e668. Sanchis-Alfonso V, Montesinos-Berry E, Monllau JC, Merchant AC. Results of isolated lateral retinacular reconstruction for iatrogenic medial patellar instability. Arthroscopy 2015;31:422-427. Domenech J, Sanchis-Alfonso V, Espejo B. Changes in catastrophizing and kinesiophobia are predictive of changes in disability and pain after treatment in patients with anterior knee pain. Knee Surg Sports Traumatol Arthrosc 2014;22:2295-2300. Fulkerson JP. A clinical test for medial patella tracking. Tech Orthop 1997;12:165-169. Teitge RA, Faerber WW, Des Madryl P. Stress radiographs of the patellofemoral joint. J Bone Joint Surg Am 1996;78: 193-203. Biedert RM. Computed tomography examination. In: Biedert RM, ed. Patellofemoral disorders. Diagnosis and treatment. West Sussex: Wiley, 2004;101-111. Pagenstert G, Wolf N, Bachmann M, et al. Open lateral patellar retinacular lengthening versus open retinacular release in lateral patellar hypercompression syndrome: A prospective double-blinded comparative study on complications and outcome. Arthroscopy 2012;28:788-797.
19. Merchant AC. Is it lateral retinacular lengthening versus lateral retinacular release or over-release? Arthroscopy 2013;29:403. 20. Ewing JW. Arthroscopic patellar shaving and lateral retinacular release. In: McGinty JB, ed. Operative arthroscopy. New York: Raven, 1991;282-286. 21. Henry JH, Goletz TH, Williamson B. Lateral retinacular release in patellofemoral subluxation. Indications, results, and comparison to open patellofemoral reconstruction. Am J Sports Med 1986;14:121-129. 22. Marumoto JM. A biomechanical comparison of lateral retinacular releases. Am J Sports Med 1995;23:151-155. 23. Merchant AC, Mercer RL. Lateral release of the patella. A preliminary report. Clin Orthop Relat Res 1974;103: 40-45. 24. Vavken P, Wimmer MD, Camathias C, Quidde J, Valderrabano V, Pagenstert G. Treating patella instability in skeletally immature patients. Arthroscopy 2013;29: 1410-1422. 25. Ma LF, Wang F, Chen BC, Wang CH, Zhou JW, Wang HY. Medial retinaculum plasty versus medial patellofemoral ligament reconstruction for recurrent patellar instability in adults: A randomized controlled trial. Arthroscopy 2013;29:891-897. 26. Song GY, Hong L, Zhang H, et al. Trochleoplasty versus nontrochleoplasty procedures in treating patellar instability caused by severe trochlear dysplasia. Arthroscopy 2014;30:523-532. 27. Noyes FR, Barber-Westin SD. Advanced patellofemoral cartilage lesions in patients younger than 50 years of age: Is there an ideal operative option? Arthroscopy 2013;29: 1423-1436. 28. Sanchis-Alfonso V. Patellofemoral malalignment versus tissue homeostasis. Myths and truths about patellofemoral disease & evaluation of the patient with anterior knee pain and patellar instability. In: Anterior knee pain and patellar instability. London: Springer, 2011. 29. Larson RL, Cabaud HE, Slocum DB. The patellar compression syndrome: Surgical treatment by lateral retinacular release. Clin Orthop Relat Res 1978;134: 158-167. 30. Bollier M, Fulkerson J, Cosgarea A, Tanaka M. Technical failure of medial patellofemoral ligament reconstruction. Arthroscopy 2011;27:1153-1159.
Iatrogenic Medial Patellar Instability: An Avoidable Injury Vicente Sanchis-Alfonso, M.D., Ph.D., and Alan C. Merchant, M.D.
Abstract: Iatrogenic medial patellar instability is a specific condition that frequently causes incapacitating anterior knee pain, severe disability, and serious psychological problems. The diagnosis should be suspected in a patient who has undergone previous patellar realignment surgery that has made the pain worse. The diagnosis can be established by physical examination and simple therapeutic tests (e.g., “reverse” McConnell taping) and confirmed by imaging techniques. This iatrogenic condition should no longer exist and could almost be eliminated by avoiding over-release of the lateral retinaculum.
A
nterior knee pain (AKP) is one of the most common symptoms of patients seeking orthopaedic care. The pain can vary from mild to disabling and can arise from a wide variety of causes. Iatrogenic medial patellar instability (IMPI) is an objective condition with its own characteristics that frequently causes incapacitating AKP and should be included in the differential diagnosis of AKP in patients who have undergone any prior extensor mechanism realignment surgery.1 Certainly, IMPI is a rare condition in the totality of orthopaedic problems, but its clinical importance far exceeds its numbers. IMPI frequently causes severe pain and disability that are difficult to treat successfully. It is especially troubling because almost all of these cases have been caused by patellar realignment surgery that was intended to help AKP or patellar instability in the first place.1-13 Despite the initial study by Hughston and Deese2 in 1988 and other studies that followed, all of which warned about IMPI, and despite articles written later about avoiding this injury, the problem still exists
From the Department of Orthopaedic Surgery, Hospital 9 de Octubre (V.SA.), Valencia, Spain; Department of Orthopedic Surgery, Stanford University School of Medicine (A.C.M.), Stanford, California; and Department of Orthopedic Surgery, El Camino Hospital (A.C.M.), Mountain View, California, U.S.A. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received October 10, 2014; accepted January 22, 2015. Address correspondence to Vicente Sanchis-Alfonso, M.D., Ph.D., Department of Orthopaedic Surgery, Hospital 9 de Octubre, C/Valle de la Ballestera 59, 46015 Valencia, Spain. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/14862/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.01.028
1628
currently.8-13 Almost all IMPI cases have been caused either by improper patient selection or by overzealous and excessive release of the lateral retinaculum (LR).1 All too often, the pain and disability from IMPI are much worse than the preoperative symptoms for which the operation was performed, causing serious psychological side effects. The percentage of patients with catastrophizing ideas, kinesiophobia, anxiety, and depression is much larger in a group of IMPI patients than in the usual group of patients complaining of AKP.14 Comparing our IMPI patients13 with our previous series of more usual AKP patients,14 we found that the former had higher rates of kinesiophobia (100% v 80%), catastrophizing (41% v 37%), anxiety (59% v 37%), and depression (24% v 11%). Frequently, this type of psychological pathology is overlooked by the orthopaedic surgeon. Most of these patients go from one doctor to another until they find a solution to their problem. In our series on IMPI, patients had to visit more than 3 doctors before being given the correct diagnosis and an appropriate treatment plan. Therefore we believe there is a need to publicize not only the diagnostic procedures for recognizing IMPI but also the surgical principles to avoid this iatrogenic injury in the first place. The purposes of this article are to show how to recognize this serious injury and to review the factors causing IMPI and learn how to avoid them.
IMPIdA Rare Condition Of the 168 cases of medial patellar instability reported in the literature, 153 (91%) occurred in patients who had undergone a previous lateral retinacular release (LRR), either isolated or associated with realignment surgery.13 Of the remaining 15 non-iatrogenic cases
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 31, No 8 (August), 2015: pp 1628-1632
1629
IATROGENIC MEDIAL PATELLAR INSTABILITY Fig 1. Medial subluxation test according to Fulkerson.15 (A) The patella is held medially in extension (arrow) and (B) then released on abrupt knee flexion. It is a provocative test, and therefore reproduction of symptomatology with this maneuver strongly suggests medial patellar instability. Reprinted with kind permission of Springer Scienceþ Business Media.28
(9%), 8 were the result of trauma and 7 occurred spontaneously.13 Because there is little written about IMPI, we sought to learn the extent of this injury. When IMPI is encountered, its disability is so severe and the treatment so challenging that each patient becomes unique and memorable. Therefore we conducted a simple, informal survey of orthopaedic surgeons who have shown a particular interest in patellofemoral problems. Twenty-four surgeons from the United States, Europe, South Africa, and Australia responded, and the number of IMPI patients they recalled having treated in the previous 5 years ranged from 0 to 20. The majority of these surgeons, 16 of 24, treated 3 or fewer cases, and the remaining 8 surgeons recalled 5 to 20 cases each. The median number of IMPI patients treated was 3 per surgeon in the previous 5-year period. It was evident that the number of these patients seen was largely dependent on each surgeon’s referral base,
practice situation, and locality. The fact that this simple and unscientific survey collected 119 patients, when ideally the number should be 0, points to the need for wider publication and more education regarding IMPI.
Diagnosing IMPI IMPI patients usually present with incapacitating, chronic, and disabling AKP along with serious psychological problems.13 Most of our patients had undergone an “extensive” isolated LRR according to the index operative reports.13 Typically, the patient felt a new pain and new instability after that index surgery that were distinct from, and much worse than, those before surgery. In general, IMPI occurs in the first 30 of knee flexion. IMPI is often overlooked as a cause of symptoms because patients will complain of the patella moving laterally with early knee flexion.
Fig 2. Technique for application of reverse McConnell taping on a patient’s right knee. (A) Protective tape. (B, C) Application of Leukotape (Endura Tape Pty Ltd., Clareville, NSW, Australia). (D) Definitive tape in place. (L, lateral; M, medial; P, patella.)
1630
V. SANCHIS-ALFONSO AND A. C. MERCHANT Fig 3. (A) An axial stress radiograph of the left knee allows us to detect iatrogenic medial subluxation of the patella (medial displacement of 15 mm). (B) Axial stress radiograph of right knee. Arrows represent the force applied to displace the patella medially. Reprinted with kind permission of Springer Scienceþ Business Media.28
The physical findings are crucial for the diagnosis of IMPI. The most important findings are (1) pain and tenderness at the site of the LR defect; (2) increased passive medial patellar mobility, especially when compared with the opposite normal knee; (3) pain and apprehension when medial stress is applied to the patella; (4) a positive gravity subluxation test4; and (5) a positive Fulkerson relocation test15 (Fig 1). Therapeutic diagnostic tests are also important. A “reverse” McConnell taping can be performed to hold the patella laterally and prevent it from subluxating medially (Fig 2). All of our patients experienced significant relief from their pain with this taping.13 Similarly, application of a patellar brace with the buttress pad or strap on the medial side will minimize or eliminate symptoms of IMPI.1 Finally, stress radiographs16 (Fig 3) and stress axial computed tomography scans17 (Fig 4) will document and quantify IMPI objectively. A comparison of the normal side with the abnormal sidedif possibledis more important than the absolute amount of displacement (Figs 3 and 4).
Preventing IMPI It is clear that extensive release, or over-release, of the LR is a major cause of IMPI.13,18,19 This can be a result of
Fig 4. (A) Axial stress radiograph of right knee. (B) An axial stress computed tomography (CT) scan of the left knee allows us to detect iatrogenic medial subluxation of the patella (medial displacement of 13 mm). Arrows represent the force applied to displace the patella medially. Reprinted with kind permission of Springer ScienceþBusiness Media.1
excessive severance of the LR with transection of the vastus lateralis tendon (Fig 5) or can result from releasing an LR that was already lax, showing poor patient selection. An isolated LRR should never be performed in the face of trochlear dysplasia, patella alta, or hyperelasticity. If the LR is not tight, the surgeon should not release it. The goal of a proper LRR is to normalize the medial glide to 1 to 2 fingerbreadths (1 to 2 quadrants) or to a tilt-up endpoint of no more than 60 to 70 19,20 and never to 90 . The vastus lateralis tendon should never be severed. In a recent study by Pagenstert et al.18 in 2012, the authors causeddinadvertentlydmajor quadriceps atrophy in 36% and IMPI in 57% of patients in their “control group” after over-release of the LR by using the 90 tiltup endpoint (rotational elevation of the lateral patella up to 90 in relation to the epicondylar axis) published by Henry et al.21 26 years previously. However, this cause of IMPI has been known at least since 1995, when Marumoto22 published his study. He stated, “A lateral patellar retinacular release that transects the tendon of the vastus lateralis muscle may result in significant complications.” His summary stated, “Complications of lateral releases include medial patellar subluxation, vastus lateralis muscle atrophy and persistent quadriceps muscle weakness. These are likely due to excessive
1631
IATROGENIC MEDIAL PATELLAR INSTABILITY
Fig 5. In patients with iatrogenic medial patellar instability, we frequently find (A) a sectioned vastus lateralis tendon (red arrow). (B) Reconstruction of lateral retinaculum with iliotibial band (black arrow) and reattachment of vastus lateralis (green arrow).
superior extension through the tendon of the vastus lateralis muscle that eliminates its function as a dynamic lateral stabilizer of the patella, and a major extensor of the knee. Maximizing the inferior extent of a lateral release while preserving the tendon of the vastus lateralis muscle may allow an adequate release of the patella while maintaining the physiologic function of the vastus lateralis muscle.” Unfortunately, many orthopaedic surgeons have attributed these severe adverse complications caused by over-release of the LR to all lateral release procedures. LRR, described by Merchant and Mercer23 in 1974, has been one of the most frequently performed procedures in orthopaedic surgery to treat patients with AKP.24-27 However, IMPI is a rare condition. In our experience an isolated LRR that has been performed properly for the correct indications has never caused an IMPI with severe quadriceps atrophy and disabling pain. Therefore IMPI should be considered an avoidable injury. If the LRR is performed for pain, then the surgeon must be convinced that the tight LR is a major contributing factor for that pain. We believe that the role of LRR is limited to the rare patient with clear signs and symptoms of lateral patellar hypercompression syndrome. LRR is discussed in this report with the understanding and assumption that realignment surgery is rarely indicated until all proper physical therapeutic measures have been exhausted. Such measures can successfully treat about 90% of all patients complaining of AKP.28 LR lengthening has been advocated to prevent postoperative IMPI. Indeed, many years ago, in 1978, when all LRRs were performed in an open manner, Larson et al.29 stated that it is better to lengthen the LR than to release it. Our goal as surgeons is to achieve the best results possible for our patients using the least invasive and safest techniques available. By treating all lateral patellar hypercompression syndrome patients who are candidates for surgery with open LR lengthening, surgeons have turned a relatively simple and low-risk arthroscopic procedure into a longer and more complex open procedure for no measurable advantage.
Because of inappropriate over-releases of the LR in the past, fewer releases are being performed. Therefore one might assume that cases of IMPI would decrease, but this is not the case. With the increased use of medial patellofemoral ligament reconstructions, it has been shown that malpositioning or over-tightening of the medial patellofemoral ligament graft, with or without an LRR, may lead to IMPI.30
Conclusions IMPI is an objective condition with its own characteristics that causes incapacitating AKP. It can be readily suspected in a patient who has undergone previous patellar realignment surgery that has made the pain worse. The diagnosis can be established by physical examination and simple therapeutic tests and confirmed by imaging techniques. This iatrogenic condition should no longer exist and could almost be eliminated by avoiding over-release of the LR, only releasing a tight LR, and focusing on normalizing the abnormal anatomy.
References 1. Sanchis-Alfonso V, Ramírez-Fuentes C, Martínez-Soriano F, Monllau JC, Merchant AC. Medial patellar instability. A little-known cause of anterior knee pain. In: Gobbi A, Espregueira-Mendes J, Nakamura N, eds. The patellofemoral joint. State of the art in evaluation and management. Heidelberg: Springer, 2014;79-92. 2. Hughston JC, Deese M. Medial subluxation of the patella as a complication of lateral retinacular release. Am J Sports Med 1988;16:383-388. 3. Biedert RM, Friederich NF. Failed lateral retinacular release: Clinical outcome. J Sports Traumatol 1994;16: 162-173. 4. Nonweiler DE, DeLee JC. The diagnosis and treatment of medial subluxation of the patella after lateral retinacular release. Am J Sports Med 1994;22:680-686. 5. Hughston JC, Flandry F, Brinker MR. Surgical correction of medial subluxation of the patella. Am J Sports Med 1996;24:486-491. 6. Kramers-de Quervain IA, Biedert R, Stüssi E. Quantitative gait analysis in patients with medial patellar instability
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8.
9.
10.
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15. 16.
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