The Spine Journal
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Clinical Study
Anterior or posterior approach of thoracic disc herniation? A comparative cohort of mini-transthoracic versus transpedicular discectomies Mark P. Arts, MD, PhDa,*, Ronald H.M.A. Bartels, MD, PhDb b
a Department of Neurosurgery, Medical Center Haaglanden, PO Box 432, 2501 CK, The Hague, The Netherlands Department of Neurosurgery, Radboud University Medical Center Nijmegen, PO Box 9101, 6500HB, Nijmegen, The Netherlands
Received 29 March 2013; revised 23 September 2013; accepted 27 September 2013
Abstract
BACKGROUND CONTEXT: The optimal surgical treatment of thoracic disc herniations remains controversial and depends on the consistency of the herniation and its location related to the spinal cord. PURPOSE: To compare the outcomes of patients with symptomatic thoracic disc herniations treated with anterolateral mini-transthoracic approach (TTA) versus posterior transpedicular discectomy. STUDY DESIGN: This is a prospective comparative cohort study. PATIENT SAMPLE: One hundred consecutive patients with symptomatic thoracic herniated discs were operated by mini-TTA (56 patients) or transpedicular discectomy (44 patients). OUTCOME MEASURES: Neurologic assessment by American Spinal Injury Association (ASIA) Impairment Scale and patients’ self reported perceived recovery and complications. METHODS: The consistency and location of the herniated disc in relation to the spinal cord was evaluated by preoperative computed tomography and magnetic resonance imaging. Patients were assessed neurologically before surgery and at regular outpatient controls at 2 months or later. Long-term follow-up was achieved by questionnaires sent by mail. RESULTS: In both groups, most patients had symptoms of myelopathy and radicular pain; patients who underwent mini-TTA, more frequently suffered from spasticity. Fifty-eight percent of the herniated discs were calcified and 77% were larger than one-third of the spinal canal. All patients presented with ASIA Grade C or D (64%) or ASIA Grade E (36%). Postoperatively, 50% of the patients treated with mini-TTA and 37% of the transpedicular group improved at least one grade on the ASIA scale (p5.19). The duration of surgery, blood loss, hospital stay, and complication rate were significantly higher in patients treated with mini-TTA and were mainly related to the magnitude and consistency of the herniated disc. At long-term follow-up, 72% of the mini-TTA patients reported good outcome versus 76% of the transpedicular discectomy group (p5.80). CONCLUSIONS: Surgical treatment of a symptomatic herniated disc contributed to a clinical improvement in most cases. The approach is dependent on the location, the magnitude, and the consistency of the herniated thoracic disc. Medially located large calcified discs should be operated through an anterolateral approach, whereas noncalcified or lateral herniated discs can be treated from a posterior approach as well. For optimal treatment of this rare entity, the treatment should be performed in selected centers. Ó 2013 Elsevier Inc. All rights reserved.
Keywords:
Thoracic disc; Herniation; Mini-TTA; Posterolateral; Calcification; Spine; Surgery
Introduction The first case of thoracic disc herniation with spinal cord compression was reported by Key in 1838 [1]. The earliest record of thoracic disc surgery was carried out by Adson FDA device/drug status: Not applicable. Author disclosures: MPA: Grants: Cascade trial (F, Cascade trial sponsored by Amedica Corporation). RHMAB: Grants: NutsOhra Fonds (F, Paid directly to institution/employer). The disclosure key can be found on the Table of Contents and at www. TheSpineJournalOnline.com. 1529-9430/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.spinee.2013.09.053
in 1922, who performed a laminectomy and disc removal [2]. Thoracic disc herniations are relatively rare, and surgical treatment comprises less than 1% of all intervertebral disc surgeries [3–5]. Whenever symptomatic, patients may * Corresponding author. Department of Neurosurgery, Medical Center Haaglanden, PO Box 432, 2501 CK, The Hague, The Netherlands. Tel.: 070-3302054; fax: 070-3809459. E-mail address: [email protected] (M.P. Arts)
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present with progressive myelopathy, localized thoracic pain, and/or radicular pain. Although the entity of thoracic disc herniation is well known, the appropriate indications and choice of surgical strategy are controversial. Formerly, dorsal decompression with laminectomy was the standard procedure in the treatment of thoracic disc herniations. Because of poor outcome and neurologic deterioration, laminectomy was abandoned and alternative approaches were studied [6]. Patterson and Arbit [7] introduced the posterolateral transpedicular discectomy without laminectomy that has been shown as safe and effective. This technique has been modified into a transfacet pedicle-sparing approach [8–10]. However, substantial paravertebral muscle dissection is needed to gain access to centrally located disc herniations, but even then, adequate ventral dura decompression can be challenging [11,12]. Anterior transthoracic discectomy was advocated to improve direct ventral access and avoid spinal cord manipulation, although pulmonary complications and intercostal neuralgia may occur [6,13,14]. In recent years, extensive open thoracotomy was modified into less invasive techniques, such as the mini-transthoracic approach (mini-TTA) and thoracoscopic discectomy [15–18]. A recent comparative study has shown benefits in favor of miniTTA, especially in patients with paramedially located disc herniations [19]. To our knowledge, no comparative study between mini-TTA and posterolateral transpedicular approach of thoracic disc herniations has been performed. In the present cohort, we report the results of 100 consecutive patients with thoracic disc herniations who underwent mini-TTA or transpedicular discectomy. Materials and methods Patient population Between March 2005 and January 2013, 100 consecutive patients with 106 symptomatic thoracic disc herniations were treated in two Dutch neurosurgic centers (66 patients in The Hague and 34 patients in Nijmegen). Preoperative and postoperative neurologic examinations were available of all patients. Symptoms were assessed using the American Spinal Injury Association (ASIA) Impairment Scale. Patients were examined neurologically during the outpatient control 2 months after surgery, or more often when necessary (follow-up moment 1). The long-term results were investigated by means of a questionnaire sent by mail (follow-up moment 2) that included selfreported recovery, visual analog pain score, and neurologic complaints related to thoracic disc herniation. Patients’ self perceived recovery was measured by the seven-point Likert scale; ‘‘complete recovery,’’ ‘‘almost complete recovery,’’ and ‘‘some recovery’’ were determined as good outcome [20]. Radiographic imaging Preoperative magnetic resonance imaging (MRI) was performed in all patients to document the localization of
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the herniated disc, relation of the herniated disc to the spinal cord, and the size of the herniated disc; less than onethird of the spinal canal diameter, one-third to two-thirds of the spinal canal diameter, or larger than two-thirds of the spinal canal diameter (Figs. 1 and 2, A and B). All patients underwent additional computed tomography (CT) for the documentation of calcified (Fig. 1, C and D) or noncalcified herniated discs (Fig. 2, C and D). Postoperative imaging of the spinal cord was not used routinely, but only on indication and when additional fusion was performed. Surgical procedures Mini-TTA Under general anesthesia and two-lumen tube ventilation, the patient is placed in lateral decubitus position with the table tilted. Spinal cord monitoring was not used. In all cases, a right side approach is performed, except for those patients with disc herniation at the thoracolumbar junction where the diaphragm on the right side prevents adequate exposure. The involved thoracic disc and adjacent vertebral bodies are drawn on the skin under fluoroscopic control. A 6 to 8 cm long skin incision is made parallel to the orientation of the rib. After splitting the fibres of the latissimus dorsi and serratus anterior muscles, the underlying rib is exposed and the mini-TTA spreader (Braun-Aesculap, Melsungen, Germany) is positioned between the ribs. When necessary, the rib can be removed partially for extensive exposure of the thoracic spine. After deflating the lung, the visceral pleura is opened and the lung is retracted with an inflatable lung retractor. The affected disc is verified fluoroscopically. Under microscopic magnification, the rib head, cranial part of the pedicle, the inferolateral part of the cranial vertebral body, and the superolateral part of the caudal vertebral body are removed with a high-speed drill. After opening the longitudinal ligament, the herniated disc can be mobilized anteriorly away from the spinal cord (Fig. 3) In case of a large calcified herniated disc, substantial bony removal may be necessary, and additional instrumented fusion is performed in the same procedure when an estimated 25% or more of the craniocaudal extent of the vertebral body has been removed. Finally, a chest tube is placed and the wound is closed in layers [15]. Transpedicular discectomy The patient is placed in a prone position under general anesthesia, and no spinal cord monitoring was used. The involved thoracic disc is verified fluoroscopically and a midline skin incision of approximately 10 cm length is made. The ipsilateral paravertebral muscles are subperiostally dissected and retracted laterally to expose the facet joint and pedicle. After fluoroscopic verification of the affected disc level, the medial part of the inferior and superior facets and the cranial part of the pedicle are drilled off with a highspeed burr. The disc space lateral to the dural sac is incised, and the disc fragments are removed under microscopic
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Fig. 1. Example of a calcified herniated disc. (A) Sagittal and (B) transversal T2 magnetic resonance images of a paramedian herniated disc T9–T10, larger than two-third of the spinal canal diameter. (C and D) The herniated disc is hypointense on T2 imaging. Computed tomography confirms complete calcification of the herniated disc.
magnification (Fig. 4) In case of a calcified herniated disc, a trough is drilled in the underlying vertebral body to mobilize the herniated disc dorsally. When necessary, partial costotranversectomy is performed to gain access ventrally to the dura in case of central disc extrusion. Additional instrumented fusion was not performed. After adequate spinal cord decompression, the wound is closed in layers over a suction drain. Statistical analysis Student paired two-tailed t tests were used to compare parametric data; otherwise Pearson chi-square tests, Fisher exact test, or Mann-Whitney U tests were used. Results are presented as means6standard deviations. A probability value less than .05 was considered statistically significant. Statistical analysis was performed with SPSS software (version 20; SPSS Inc., Chicago, IL, USA).
Results Fifty-six patients underwent mini-TTA and 44 patients were treated with transpedicular discectomy. Baseline characteristics of the patients are presented in Table 1. The level of the herniated disc ranged from T2–T3 to T12–L1, and the most common affected disc levels were in the lower thoracic region. Nearly 80% of the herniated discs were larger than one-third of the spinal canal and almost 60% of the herniated discs showed calcifications on CT. Surgical findings and postoperative course Surgical findings and postoperative course are depicted in Table 2. The mean duration of a mini-TTA procedure was 229 minutes versus 98 minutes for transpedicular discectomy (p!.001), with substantially more blood loss during mini-TTA procedure (1,157 mL vs. 213 mL, p!.001).
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Fig. 2. Example of a noncalcified herniated disc. (A) Sagittal and (B) transversal T2 magnetic resonance images of paramedian noncalcified herniated disc T8–T9, smaller than one-third of the spinal canal diameter. (C and D) The herniated disc is hypointense on T2 imaging. Computed tomography documents no calcification.
In the mini-TTA group, 17 patients presented with calcified herniated disc adherent to dura versus 3 patients treated by transpedicular approach (p5.005). In nine patients treated by mini-TTA, more than 25% of the vertebral body was drilled away to remove the herniated disc safely, and additional instrumented fusion was performed. The mean hospital stay in patients treated with mini-TTA procedure was significantly longer (10.1 days vs. 4.9 days; p5.03). Pulmonary complications, such as pneumonia and pleural effusions (18%), cerebrospinal fluid leakage requiring external drainage and bed rest for a few days (18%), were the main complications. Two patients of the transpedicular group were reoperated; one patient developed paraplegia caused by rebleeding and the other patient was operated on the wrong level. In the mini-TTA group, three patients were reoperated; one patient developed a cerebrospinal fluid fistula to the pleura that needed transthoracic reintervention and closing the duradefect followed by external
cerebrospinal fluid drainage; one patient had insufficient dura decompression requiring repeated mini-TTA; and one patient underwent a mini-TTA for an assumed herniated disc. During surgery an epidural abnormality was not found, and an immediate postoperative MRI showed an intradural mass. At a second operation through a posterolateral approach with intradural inspection, a meningioma was identified and completely removed. Clinical outcome Data was available for 96 patients at follow-up moment 1 and 77 patients returned the long-term questionnaires at follow-up moment 2. The mean (6standard deviation) follow-ups from surgery to moment 1 and moment 2 were 34631 weeks and 4.162.1 years, respectively. In the mini-TTA group, 28 patients (50%) improved one or more grades on the ASIA scale versus 15 patients (37%) in the
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Fig. 3. Intraoperative microscopic view of right-sided mini-transthoracic approach of a large paramedian calcified herniated disc at T9–T10 (same patient as in Fig. 1). Parts of the inferolateral cranial and superolateral caudal vertebral bodies are removed with a high-speed drill. (Top Left) A dissector is placed in the formed cavity. (Top Right) The posterior longitudinal ligament is opened and the calcified herniated disc is mobilized anteriorly away from the spinal cord. (Bottom) After removal of the calcified herniated disc, the dura is adequately decompressed.
transpedicular group (p5.19) (Table 3). After the mini-TTA procedure, three patients worsened one or more grades on the ASIA scale; the calcified thoracic disc appeared to be ossification of the posterior longitudinal ligament in two patients and a meningioma in the other patient. In the transpedicular group, one patient worsened neurologically because of rebleeding. On follow-up moment 2, 72% of the mini-TTA patients reported good outcome versus 76% of the transpedicular discectomy group (p5.80). Visual Analog Score (0–100mm) thoracic back pain in the mini-TTA group and posterolateral
group was 30628 mm versus 36632 mm, respectively (p5.38). Other long-term symptoms are shown in Table 4.
Discussion Initial attempts to decompress the dura via laminectomy were disappointing because of vascular insufficiency and microcontusions secondary to spinal cord manipulation. Therefore, variations in surgical techniques were developed to allow a more direct approach to the intervertebral disc,
Fig. 4. Intraoperative microscopic view of posterior transpedicular discectomy of a right-sided noncalcified mediolateral herniated disc at T10–T11. (Left) The paravertebral muscles are dissected on the right side and the wound spreader is placed. The facet, pedicle, and adjacent laminae are reduced with a highspeed drill to gain access to lateral and ventral of the dura. (Right) The asterisk marks the disc space after removal of the herniated disc.
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Table 1 Demographic data of 100 patients with 106 thoracic disc herniations, who underwent mini-TTA or transpedicular discectomy Baseline characteristics
Mini-TTA (N556)
Transpedicular (N544)
Female gender Mean age in yrs (range) Body Mass Index (range) Comorbidities Diabetes Pulmonary disease Morbid obesitas Symptoms Localised thoracic pain Radicular pain Sensory deficit Motor deficit Spasticity/hyperreflexia Miction disturbance Indications for surgery Radiculopathy Myelopathy Mean duration of symptoms (wks) (range) Level of herniated disc T2T3 T4T5 T5T6 T6T7 T7T8 T8T9 T9T10 T10T11 T11T12 T12L1 Disc calcification Axial localization Paramedian Mediolateral Lateral Size of herniated disc !1/3 of spinal canal 1/3–2/3 of spinal canal O2/3 of spinal canal
33 (59) 52.4 (29–82) 27.8 (20–46)
26 (59) 56.9 (28–86) 26.6 (20–34)
3 (5) 1 (2) 3 (5) 16 14 46 32 42 23
(29) (25) (82) (57) (75) (41)
13 (23) 43 (77) 93.4 (1–520) 0 0 3 7 7 8 14 10 5 2 47
(5) (13) (13)* (14)*,y (25)*,y (18)z (9)z (4) (94)
p Value .99 .08 .23 .38
2 (5) 2 (5) 0 20 17 35 22 24 17
(45) (39) (80) (50) (55) (39)
14 (32) 30 (68) 68.8 (0–312) 1 4 2 2 3 3 6 4 12 7 11
(2) (9) (5) (5) (7)x (7)x (14) (9) (27)x (16) (25)
35 (63) 19 (34) 2 (4)
10 (23) 22 (50) 12 (27)
10 (18) 29 (52) 17 (30)
13 (30) 29 (66) 2 (5)
.10 .20 .80 .55 .04 .84 .34
.25 .02
!.001 !.001
.04
TTA, transthoracic approach. Numbers in parentheses are percentages. * One patient had a herniated disc at three levels. y One patient had a herniated disc at two levels. z One patient had a herniated disc at two levels. x One patient had a herniated disc at three levels.
such as ventral transthoracic and posterolateral transpedicular. The best surgical treatment of thoracic disc herniations remains controversial. Comparative studies on conventional transthoracic access versus posterior decompression have been published previously [10]. However, to our knowledge, our study is the first comparative cohort of patients with symptomatic thoracic disc herniations treated with mini-TTA versus transpedicular discectomy. The clinical outcome of mini-TTA and posterolateral discectomy is favorable in both groups, and more than 70% of the patients reported good outcome on short and long terms. This study confirmed that the choice of approach is dependent on the consistency of the herniated disc, its size, and its location related to the spinal cord. Especially calcified, larger
and medially located herniated discs were approached through a mini-TTA. However, the complication rate is substantial and many of these are directly related to the TTA. The complication rate of 38% in the mini-TTA group in our study is high, but in accordance to other recently reported papers on thoracic disc surgery [8,10,13,17]. Cerebrospinal fluid leakage was the most frequently reported complication in patients treated with mini-TTA that is directly related to the calcifications of the herniated disc adherent to the dura. The significantly less frequent complication rate in the posterolateral group can be explained by smaller and less often calcified disc herniations. Pulmonary related morbidity is the other main complication of the mini-TTA procedure that is related to opening the pleura and retraction on the deflated
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Table 2 Operative characteristics Surgical characteristics
Mini-TTA (N556)
Transpedicular (N544)
p Value
Duration of surgery (min) (range) Blood loss (mL) (range) Instrumented fusion Disc adherent to dura Intradural disc extension Duration of chest tube (d) (range) Duration of stay ICU (d) (range) Hospital stay (d) (range) Total complications Neurologic deterioration Cerebrospinal fluid leakage Pneumonia/pleural effusion Wrong level surgery Repeated surgery Wrong level surgery Insufficient dura decompression Rebleeding Cerebrospinal fluid fistula
229 1,157 9 17 4 2.2 1.0 10.1 21 2 10 10 0 3 0 2 0 1
98 213 0 3 1 NA NA 4.9 2 1 0 0 1 2 1 0 1 0
!.001 !.001 .004 .005 .38 !.001 !.001 .03 !.001
(90–510) (100–12,000) (16) (30) (7) (0–11) (0–5) (3–70) (38)* (4) (18) (18) (5)
(30–220) (10–600) (7) (2)
(2–30) (5) (2)
(2) (5)
.85
ICU, intensive care unit; TTA, transthoracic approach; NA, not applicable; SD, standard deviation. Numbers presented are means (with ranges), means6SD, and percentages (parentheses). * Two patients had multiple complications.
lung. Possibly, this complication could be reduced by an alternative extrapleural approach of the spinal column in which the pleura is dissected from the rib and remains intact, and therefore, no chest tube is required [21]. However, the use of a chest tube in our most recent cases was abandoned, as our pulmonary surgeons convinced us that it was not necessary because the lung tissue was not violated. These patients were also directly transferred to the ward with an intermittent stay at the intensive care unit. The higher complication rate with mini-TTA could explain the longer stay in the hospital for these patients in addition to the preoperatively more severe symptoms in the group. The long-term results of patients with surgically treated disc herniations are favourable. Although most patients presented with spinal cord symptoms, which are often regarded as permanent disability, more than 70% of the patients in both groups reported good outcome, ranging from complete
Table 3 Neurologic status measured by the ASIA classification. Mini-TTA ASIA grade A B C D E
Table 4 Long-term symptoms of 77 patients, reported on the questionnaire sent by mail. Outcome
Transpedicular
Preoperative (%)
Postoperative (%)
Preoperative (%)
Postoperative (%)
0 0 11 (20) 28 (50) 17 (30)
0 2 1 12 41
0 0 11 (25) 14 (32) 19 (43)
0 0 3 (7) 10 (23) 28 (64)
(4) (2) (21) (73)
recovery to some recovery. However, most patients reported persistent sensory and motor deficits with thoracic back pain. These long-term results together with potential complications should be discussed in detail with patients while obtaining consent. The main limitation of the present study is selection bias and lack of randomization. Based on the presence of disc calcification and axial localization, patients were selected for mini-TTA or transpedicular discectomy. Large paramedian calcified discs were nearly always operated through mini-TTA, and patients with smaller lateral herniated discs were mostly operated by a posterior approach. Possibly, two different patient populations were studied. Ideally, future randomized controlled studies seemed to be warranted. However, in our opinion, a golden standard will be difficult
ASIA, American Spinal Injury Association; TTA, transthoracic approach. In the mini-TTA group, 28 patients (50%) improved one or more grades on the ASIA scale versus 15 patients (37%) in the transpedicular group (p5.19).
Mean FU in (mo) (range) VAS thoracic pain (mm) (range) Good outcome Symptoms Local thoracic back pain Radicular pain Sensory deficit legs Motor deficit legs Pulmonary discomfort
Mini-TTA (N544)
Transpedicular (N533)
p Value
29.1 (3–64) 29.9 (0–100)
26.6 (4–64) 36.1 (0–92)
.51 .38
32 (72)
25 (76)
.80
9 18 29 19 6
13 9 16 12
(20) (41) (66) (43) (14)
(39) (27) (48) (36)
0
TTA, transthoracic approach; FU, follow-up; VAS, Visual Analog Score. Likert good recovery is defined as ‘‘complete recovery,’’ ‘‘almost complete recovery,’’ and ‘‘some recovery.’’
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Fig. 5. Postoperative (Left) X-ray, (Middle) computed tomography, and (Right) magnetic resonance image of mini-transthoracic approach removal of a large calcified herniated disc T9–T10, with supplemental instrumentation (same patient as in Figs. 1 and 3). (Left) Whenever more than 25% of the craniocaudal extent of the vertebral body had to be removed, additional anterior bicortical screw and rod fixation was performed to prevent iatrogenic scoliosis. (Middle and Right) The herniated disc was removed completely and the spinal cord was adequately decompressed.
to obtain through randomized controlled trials because the approach will be defined not only by the surgeon’s preference, but, more importantly, by the consistency of the herniated disc and its relation to the spinal cord. We are confident that a randomized trial on posterior approach versus anterolateral approach for large calcified and medially located herniated thoracic discs will not be approved. The optimal approach for laterally located disc herniation on the other hand, is still open for discussion. However, considering the risk of complications and duration of hospital stay, there seems to be a slight preference for a posterolateral approach based on the results of the present study. This is in agreement with the data of Bransford et al. [10]. The surgical treatment of patients with symptomatic thoracic disc herniations can be challenging and may be associated with varying risks. Therefore, these complex spinal procedures should be concentrated in supraregional experienced spine centers with high-volume patient care. The treatment algorithm for the optimal surgical approach should consist of MRI, CT, and conventional radiograph of the lumbar spine. The latter is mandatory for documentation of possible transition spine, which is one of the pitfalls of wrong level surgery. Additional CT focusing on axial localization and presence of calcifications is also essential because MRIs of calcified and noncalcified herniated discs can be similar (Figs. 1 and 2). Based on our experience, patients with large calcified paramedian herniated discs should be treated with mini-TTA. All other patients can be treated by posterolateral approach.
There is no consensus whether routine instrumentation is needed in patients with thoracic herniated discs [10,13,17,18]. We have instrumented 9 of 56 patients of the mini-TTA group and none of the posterior group. Whenever more than 25% of the craniocaudal extent of the adjacent vertebral body was reduced to remove the herniated disc safely, we performed an additional fusion with placement of bicortical screws and rod fixation (Fig. 5). In this way, iatrogenic scoliosis will be prevented. In our opinion, supplemental fusion is not needed in patients with posterior removal of thoracic disc herniation because the unilateral pedicle and facet joints are only partially reduced and instability is not likely. Also, bony removal of the adjacent vertebral bodies is limited in case of noncalcified or lateral herniated discs. In conclusion, the long-term surgical outcome of thoracic disc herniation was favourable in most cases treated with mini-TTA and posterolateral discectomy. The complication rate of transthoracic procedures was higher and mainly related to pulmonary morbidity, and the neurologic complications were not different between both approaches. Patients with calcified herniated discs should be informed about the additional risk of cerebrospinal fluid leakage. Based on this experience, it is our opinion that large calcified paramedian herniated discs are best treated by an anterior approach, whereas noncalcified or lateral herniated discs can be treated from posterior as well. Because the entity is rare, its treatment should be concentrated in experienced centers to optimize the surgical strategy for each specific thoracic herniated disc.
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[12] Le Roux PD, Haglund MM, Harris AB. Thoracic disc disease: experience with the transpedicular approach in twenty consecutive patients. Neurosurgery 1993;33:58–66. [13] Ayhan S, Nelson C, Gok B, et al. Transthoracic surgical treatment for centrally located thoracic disc herniations presenting with myelopathy: a 5-year institutional experience. J Spinal Disord Tech 2010;23: 79–88. [14] Vollmer DG, Simmons NE. Transthoracic approaches to thoracic disc herniations. Neurosurg Focus 2000;9:e8. [15] Mayer HM. Microsurgical anterior approach to T5-T10 (Mini-TTA). Minimally invasive spine surgery. Springer, 2006:129–37. [16] Quint U, Bordon G, Preissl I, et al. Thoracoscopic treatment for single level symptomatic thoracic disc herniation: a prospective followed cohort study in a group of 167 consecutive cases. Eur Spine J 2012;21: 637–45. [17] Russo A, Balamurali G, Nowicki R, Boszczyk BM. Anterior thoracic foraminotomy through mini-thoracotomy for the treatment of giant thoracic disc herniations. Eur Spine J 2012;21:S212–20. [18] Uribe JS, Smith WD, Pimenta L, et al. Minimally invasive lateral approach for symptomatic thoracic disc herniation: initial multicenter clinical experience. J Neurosurg Spine 2012;16:264–79. [19] Bartels RH, Peul WC. Mini-thoracotomy or thoracoscopic treatment for medially located thoracic herniated disc? Spine 2007;32:E581–4. [20] Bombardier C. Outcome assessments in the evaluation of treatment of spinal disorders: summary and general recommendations. Spine 2000;25:3100–3. [21] Moran C, Ali Z, McEvoy L, Bolger C. Mini-open retropleural transthoracic approach for the treatment of giant thoracic disc herniation. Spine 2012;37:E1079–84.
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Clinical Study
Anterior or posterior approach of thoracic disc herniation? A comparative cohort of mini-transthoracic versus transpedicular discectomies Mark P. Arts, MD, PhDa,*, Ronald H.M.A. Bartels, MD, PhDb b
a Department of Neurosurgery, Medical Center Haaglanden, PO Box 432, 2501 CK, The Hague, The Netherlands Department of Neurosurgery, Radboud University Medical Center Nijmegen, PO Box 9101, 6500HB, Nijmegen, The Netherlands
Received 29 March 2013; revised 23 September 2013; accepted 27 September 2013
Abstract
BACKGROUND CONTEXT: The optimal surgical treatment of thoracic disc herniations remains controversial and depends on the consistency of the herniation and its location related to the spinal cord. PURPOSE: To compare the outcomes of patients with symptomatic thoracic disc herniations treated with anterolateral mini-transthoracic approach (TTA) versus posterior transpedicular discectomy. STUDY DESIGN: This is a prospective comparative cohort study. PATIENT SAMPLE: One hundred consecutive patients with symptomatic thoracic herniated discs were operated by mini-TTA (56 patients) or transpedicular discectomy (44 patients). OUTCOME MEASURES: Neurologic assessment by American Spinal Injury Association (ASIA) Impairment Scale and patients’ self reported perceived recovery and complications. METHODS: The consistency and location of the herniated disc in relation to the spinal cord was evaluated by preoperative computed tomography and magnetic resonance imaging. Patients were assessed neurologically before surgery and at regular outpatient controls at 2 months or later. Long-term follow-up was achieved by questionnaires sent by mail. RESULTS: In both groups, most patients had symptoms of myelopathy and radicular pain; patients who underwent mini-TTA, more frequently suffered from spasticity. Fifty-eight percent of the herniated discs were calcified and 77% were larger than one-third of the spinal canal. All patients presented with ASIA Grade C or D (64%) or ASIA Grade E (36%). Postoperatively, 50% of the patients treated with mini-TTA and 37% of the transpedicular group improved at least one grade on the ASIA scale (p5.19). The duration of surgery, blood loss, hospital stay, and complication rate were significantly higher in patients treated with mini-TTA and were mainly related to the magnitude and consistency of the herniated disc. At long-term follow-up, 72% of the mini-TTA patients reported good outcome versus 76% of the transpedicular discectomy group (p5.80). CONCLUSIONS: Surgical treatment of a symptomatic herniated disc contributed to a clinical improvement in most cases. The approach is dependent on the location, the magnitude, and the consistency of the herniated thoracic disc. Medially located large calcified discs should be operated through an anterolateral approach, whereas noncalcified or lateral herniated discs can be treated from a posterior approach as well. For optimal treatment of this rare entity, the treatment should be performed in selected centers. Ó 2013 Elsevier Inc. All rights reserved.
Keywords:
Thoracic disc; Herniation; Mini-TTA; Posterolateral; Calcification; Spine; Surgery
Introduction The first case of thoracic disc herniation with spinal cord compression was reported by Key in 1838 [1]. The earliest record of thoracic disc surgery was carried out by Adson FDA device/drug status: Not applicable. Author disclosures: MPA: Grants: Cascade trial (F, Cascade trial sponsored by Amedica Corporation). RHMAB: Grants: NutsOhra Fonds (F, Paid directly to institution/employer). The disclosure key can be found on the Table of Contents and at www. TheSpineJournalOnline.com. 1529-9430/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.spinee.2013.09.053
in 1922, who performed a laminectomy and disc removal [2]. Thoracic disc herniations are relatively rare, and surgical treatment comprises less than 1% of all intervertebral disc surgeries [3–5]. Whenever symptomatic, patients may * Corresponding author. Department of Neurosurgery, Medical Center Haaglanden, PO Box 432, 2501 CK, The Hague, The Netherlands. Tel.: 070-3302054; fax: 070-3809459. E-mail address: [email protected] (M.P. Arts)
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present with progressive myelopathy, localized thoracic pain, and/or radicular pain. Although the entity of thoracic disc herniation is well known, the appropriate indications and choice of surgical strategy are controversial. Formerly, dorsal decompression with laminectomy was the standard procedure in the treatment of thoracic disc herniations. Because of poor outcome and neurologic deterioration, laminectomy was abandoned and alternative approaches were studied [6]. Patterson and Arbit [7] introduced the posterolateral transpedicular discectomy without laminectomy that has been shown as safe and effective. This technique has been modified into a transfacet pedicle-sparing approach [8–10]. However, substantial paravertebral muscle dissection is needed to gain access to centrally located disc herniations, but even then, adequate ventral dura decompression can be challenging [11,12]. Anterior transthoracic discectomy was advocated to improve direct ventral access and avoid spinal cord manipulation, although pulmonary complications and intercostal neuralgia may occur [6,13,14]. In recent years, extensive open thoracotomy was modified into less invasive techniques, such as the mini-transthoracic approach (mini-TTA) and thoracoscopic discectomy [15–18]. A recent comparative study has shown benefits in favor of miniTTA, especially in patients with paramedially located disc herniations [19]. To our knowledge, no comparative study between mini-TTA and posterolateral transpedicular approach of thoracic disc herniations has been performed. In the present cohort, we report the results of 100 consecutive patients with thoracic disc herniations who underwent mini-TTA or transpedicular discectomy. Materials and methods Patient population Between March 2005 and January 2013, 100 consecutive patients with 106 symptomatic thoracic disc herniations were treated in two Dutch neurosurgic centers (66 patients in The Hague and 34 patients in Nijmegen). Preoperative and postoperative neurologic examinations were available of all patients. Symptoms were assessed using the American Spinal Injury Association (ASIA) Impairment Scale. Patients were examined neurologically during the outpatient control 2 months after surgery, or more often when necessary (follow-up moment 1). The long-term results were investigated by means of a questionnaire sent by mail (follow-up moment 2) that included selfreported recovery, visual analog pain score, and neurologic complaints related to thoracic disc herniation. Patients’ self perceived recovery was measured by the seven-point Likert scale; ‘‘complete recovery,’’ ‘‘almost complete recovery,’’ and ‘‘some recovery’’ were determined as good outcome [20]. Radiographic imaging Preoperative magnetic resonance imaging (MRI) was performed in all patients to document the localization of
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the herniated disc, relation of the herniated disc to the spinal cord, and the size of the herniated disc; less than onethird of the spinal canal diameter, one-third to two-thirds of the spinal canal diameter, or larger than two-thirds of the spinal canal diameter (Figs. 1 and 2, A and B). All patients underwent additional computed tomography (CT) for the documentation of calcified (Fig. 1, C and D) or noncalcified herniated discs (Fig. 2, C and D). Postoperative imaging of the spinal cord was not used routinely, but only on indication and when additional fusion was performed. Surgical procedures Mini-TTA Under general anesthesia and two-lumen tube ventilation, the patient is placed in lateral decubitus position with the table tilted. Spinal cord monitoring was not used. In all cases, a right side approach is performed, except for those patients with disc herniation at the thoracolumbar junction where the diaphragm on the right side prevents adequate exposure. The involved thoracic disc and adjacent vertebral bodies are drawn on the skin under fluoroscopic control. A 6 to 8 cm long skin incision is made parallel to the orientation of the rib. After splitting the fibres of the latissimus dorsi and serratus anterior muscles, the underlying rib is exposed and the mini-TTA spreader (Braun-Aesculap, Melsungen, Germany) is positioned between the ribs. When necessary, the rib can be removed partially for extensive exposure of the thoracic spine. After deflating the lung, the visceral pleura is opened and the lung is retracted with an inflatable lung retractor. The affected disc is verified fluoroscopically. Under microscopic magnification, the rib head, cranial part of the pedicle, the inferolateral part of the cranial vertebral body, and the superolateral part of the caudal vertebral body are removed with a high-speed drill. After opening the longitudinal ligament, the herniated disc can be mobilized anteriorly away from the spinal cord (Fig. 3) In case of a large calcified herniated disc, substantial bony removal may be necessary, and additional instrumented fusion is performed in the same procedure when an estimated 25% or more of the craniocaudal extent of the vertebral body has been removed. Finally, a chest tube is placed and the wound is closed in layers [15]. Transpedicular discectomy The patient is placed in a prone position under general anesthesia, and no spinal cord monitoring was used. The involved thoracic disc is verified fluoroscopically and a midline skin incision of approximately 10 cm length is made. The ipsilateral paravertebral muscles are subperiostally dissected and retracted laterally to expose the facet joint and pedicle. After fluoroscopic verification of the affected disc level, the medial part of the inferior and superior facets and the cranial part of the pedicle are drilled off with a highspeed burr. The disc space lateral to the dural sac is incised, and the disc fragments are removed under microscopic
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Fig. 1. Example of a calcified herniated disc. (A) Sagittal and (B) transversal T2 magnetic resonance images of a paramedian herniated disc T9–T10, larger than two-third of the spinal canal diameter. (C and D) The herniated disc is hypointense on T2 imaging. Computed tomography confirms complete calcification of the herniated disc.
magnification (Fig. 4) In case of a calcified herniated disc, a trough is drilled in the underlying vertebral body to mobilize the herniated disc dorsally. When necessary, partial costotranversectomy is performed to gain access ventrally to the dura in case of central disc extrusion. Additional instrumented fusion was not performed. After adequate spinal cord decompression, the wound is closed in layers over a suction drain. Statistical analysis Student paired two-tailed t tests were used to compare parametric data; otherwise Pearson chi-square tests, Fisher exact test, or Mann-Whitney U tests were used. Results are presented as means6standard deviations. A probability value less than .05 was considered statistically significant. Statistical analysis was performed with SPSS software (version 20; SPSS Inc., Chicago, IL, USA).
Results Fifty-six patients underwent mini-TTA and 44 patients were treated with transpedicular discectomy. Baseline characteristics of the patients are presented in Table 1. The level of the herniated disc ranged from T2–T3 to T12–L1, and the most common affected disc levels were in the lower thoracic region. Nearly 80% of the herniated discs were larger than one-third of the spinal canal and almost 60% of the herniated discs showed calcifications on CT. Surgical findings and postoperative course Surgical findings and postoperative course are depicted in Table 2. The mean duration of a mini-TTA procedure was 229 minutes versus 98 minutes for transpedicular discectomy (p!.001), with substantially more blood loss during mini-TTA procedure (1,157 mL vs. 213 mL, p!.001).
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Fig. 2. Example of a noncalcified herniated disc. (A) Sagittal and (B) transversal T2 magnetic resonance images of paramedian noncalcified herniated disc T8–T9, smaller than one-third of the spinal canal diameter. (C and D) The herniated disc is hypointense on T2 imaging. Computed tomography documents no calcification.
In the mini-TTA group, 17 patients presented with calcified herniated disc adherent to dura versus 3 patients treated by transpedicular approach (p5.005). In nine patients treated by mini-TTA, more than 25% of the vertebral body was drilled away to remove the herniated disc safely, and additional instrumented fusion was performed. The mean hospital stay in patients treated with mini-TTA procedure was significantly longer (10.1 days vs. 4.9 days; p5.03). Pulmonary complications, such as pneumonia and pleural effusions (18%), cerebrospinal fluid leakage requiring external drainage and bed rest for a few days (18%), were the main complications. Two patients of the transpedicular group were reoperated; one patient developed paraplegia caused by rebleeding and the other patient was operated on the wrong level. In the mini-TTA group, three patients were reoperated; one patient developed a cerebrospinal fluid fistula to the pleura that needed transthoracic reintervention and closing the duradefect followed by external
cerebrospinal fluid drainage; one patient had insufficient dura decompression requiring repeated mini-TTA; and one patient underwent a mini-TTA for an assumed herniated disc. During surgery an epidural abnormality was not found, and an immediate postoperative MRI showed an intradural mass. At a second operation through a posterolateral approach with intradural inspection, a meningioma was identified and completely removed. Clinical outcome Data was available for 96 patients at follow-up moment 1 and 77 patients returned the long-term questionnaires at follow-up moment 2. The mean (6standard deviation) follow-ups from surgery to moment 1 and moment 2 were 34631 weeks and 4.162.1 years, respectively. In the mini-TTA group, 28 patients (50%) improved one or more grades on the ASIA scale versus 15 patients (37%) in the
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Fig. 3. Intraoperative microscopic view of right-sided mini-transthoracic approach of a large paramedian calcified herniated disc at T9–T10 (same patient as in Fig. 1). Parts of the inferolateral cranial and superolateral caudal vertebral bodies are removed with a high-speed drill. (Top Left) A dissector is placed in the formed cavity. (Top Right) The posterior longitudinal ligament is opened and the calcified herniated disc is mobilized anteriorly away from the spinal cord. (Bottom) After removal of the calcified herniated disc, the dura is adequately decompressed.
transpedicular group (p5.19) (Table 3). After the mini-TTA procedure, three patients worsened one or more grades on the ASIA scale; the calcified thoracic disc appeared to be ossification of the posterior longitudinal ligament in two patients and a meningioma in the other patient. In the transpedicular group, one patient worsened neurologically because of rebleeding. On follow-up moment 2, 72% of the mini-TTA patients reported good outcome versus 76% of the transpedicular discectomy group (p5.80). Visual Analog Score (0–100mm) thoracic back pain in the mini-TTA group and posterolateral
group was 30628 mm versus 36632 mm, respectively (p5.38). Other long-term symptoms are shown in Table 4.
Discussion Initial attempts to decompress the dura via laminectomy were disappointing because of vascular insufficiency and microcontusions secondary to spinal cord manipulation. Therefore, variations in surgical techniques were developed to allow a more direct approach to the intervertebral disc,
Fig. 4. Intraoperative microscopic view of posterior transpedicular discectomy of a right-sided noncalcified mediolateral herniated disc at T10–T11. (Left) The paravertebral muscles are dissected on the right side and the wound spreader is placed. The facet, pedicle, and adjacent laminae are reduced with a highspeed drill to gain access to lateral and ventral of the dura. (Right) The asterisk marks the disc space after removal of the herniated disc.
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Table 1 Demographic data of 100 patients with 106 thoracic disc herniations, who underwent mini-TTA or transpedicular discectomy Baseline characteristics
Mini-TTA (N556)
Transpedicular (N544)
Female gender Mean age in yrs (range) Body Mass Index (range) Comorbidities Diabetes Pulmonary disease Morbid obesitas Symptoms Localised thoracic pain Radicular pain Sensory deficit Motor deficit Spasticity/hyperreflexia Miction disturbance Indications for surgery Radiculopathy Myelopathy Mean duration of symptoms (wks) (range) Level of herniated disc T2T3 T4T5 T5T6 T6T7 T7T8 T8T9 T9T10 T10T11 T11T12 T12L1 Disc calcification Axial localization Paramedian Mediolateral Lateral Size of herniated disc !1/3 of spinal canal 1/3–2/3 of spinal canal O2/3 of spinal canal
33 (59) 52.4 (29–82) 27.8 (20–46)
26 (59) 56.9 (28–86) 26.6 (20–34)
3 (5) 1 (2) 3 (5) 16 14 46 32 42 23
(29) (25) (82) (57) (75) (41)
13 (23) 43 (77) 93.4 (1–520) 0 0 3 7 7 8 14 10 5 2 47
(5) (13) (13)* (14)*,y (25)*,y (18)z (9)z (4) (94)
p Value .99 .08 .23 .38
2 (5) 2 (5) 0 20 17 35 22 24 17
(45) (39) (80) (50) (55) (39)
14 (32) 30 (68) 68.8 (0–312) 1 4 2 2 3 3 6 4 12 7 11
(2) (9) (5) (5) (7)x (7)x (14) (9) (27)x (16) (25)
35 (63) 19 (34) 2 (4)
10 (23) 22 (50) 12 (27)
10 (18) 29 (52) 17 (30)
13 (30) 29 (66) 2 (5)
.10 .20 .80 .55 .04 .84 .34
.25 .02
!.001 !.001
.04
TTA, transthoracic approach. Numbers in parentheses are percentages. * One patient had a herniated disc at three levels. y One patient had a herniated disc at two levels. z One patient had a herniated disc at two levels. x One patient had a herniated disc at three levels.
such as ventral transthoracic and posterolateral transpedicular. The best surgical treatment of thoracic disc herniations remains controversial. Comparative studies on conventional transthoracic access versus posterior decompression have been published previously [10]. However, to our knowledge, our study is the first comparative cohort of patients with symptomatic thoracic disc herniations treated with mini-TTA versus transpedicular discectomy. The clinical outcome of mini-TTA and posterolateral discectomy is favorable in both groups, and more than 70% of the patients reported good outcome on short and long terms. This study confirmed that the choice of approach is dependent on the consistency of the herniated disc, its size, and its location related to the spinal cord. Especially calcified, larger
and medially located herniated discs were approached through a mini-TTA. However, the complication rate is substantial and many of these are directly related to the TTA. The complication rate of 38% in the mini-TTA group in our study is high, but in accordance to other recently reported papers on thoracic disc surgery [8,10,13,17]. Cerebrospinal fluid leakage was the most frequently reported complication in patients treated with mini-TTA that is directly related to the calcifications of the herniated disc adherent to the dura. The significantly less frequent complication rate in the posterolateral group can be explained by smaller and less often calcified disc herniations. Pulmonary related morbidity is the other main complication of the mini-TTA procedure that is related to opening the pleura and retraction on the deflated
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Table 2 Operative characteristics Surgical characteristics
Mini-TTA (N556)
Transpedicular (N544)
p Value
Duration of surgery (min) (range) Blood loss (mL) (range) Instrumented fusion Disc adherent to dura Intradural disc extension Duration of chest tube (d) (range) Duration of stay ICU (d) (range) Hospital stay (d) (range) Total complications Neurologic deterioration Cerebrospinal fluid leakage Pneumonia/pleural effusion Wrong level surgery Repeated surgery Wrong level surgery Insufficient dura decompression Rebleeding Cerebrospinal fluid fistula
229 1,157 9 17 4 2.2 1.0 10.1 21 2 10 10 0 3 0 2 0 1
98 213 0 3 1 NA NA 4.9 2 1 0 0 1 2 1 0 1 0
!.001 !.001 .004 .005 .38 !.001 !.001 .03 !.001
(90–510) (100–12,000) (16) (30) (7) (0–11) (0–5) (3–70) (38)* (4) (18) (18) (5)
(30–220) (10–600) (7) (2)
(2–30) (5) (2)
(2) (5)
.85
ICU, intensive care unit; TTA, transthoracic approach; NA, not applicable; SD, standard deviation. Numbers presented are means (with ranges), means6SD, and percentages (parentheses). * Two patients had multiple complications.
lung. Possibly, this complication could be reduced by an alternative extrapleural approach of the spinal column in which the pleura is dissected from the rib and remains intact, and therefore, no chest tube is required [21]. However, the use of a chest tube in our most recent cases was abandoned, as our pulmonary surgeons convinced us that it was not necessary because the lung tissue was not violated. These patients were also directly transferred to the ward with an intermittent stay at the intensive care unit. The higher complication rate with mini-TTA could explain the longer stay in the hospital for these patients in addition to the preoperatively more severe symptoms in the group. The long-term results of patients with surgically treated disc herniations are favourable. Although most patients presented with spinal cord symptoms, which are often regarded as permanent disability, more than 70% of the patients in both groups reported good outcome, ranging from complete
Table 3 Neurologic status measured by the ASIA classification. Mini-TTA ASIA grade A B C D E
Table 4 Long-term symptoms of 77 patients, reported on the questionnaire sent by mail. Outcome
Transpedicular
Preoperative (%)
Postoperative (%)
Preoperative (%)
Postoperative (%)
0 0 11 (20) 28 (50) 17 (30)
0 2 1 12 41
0 0 11 (25) 14 (32) 19 (43)
0 0 3 (7) 10 (23) 28 (64)
(4) (2) (21) (73)
recovery to some recovery. However, most patients reported persistent sensory and motor deficits with thoracic back pain. These long-term results together with potential complications should be discussed in detail with patients while obtaining consent. The main limitation of the present study is selection bias and lack of randomization. Based on the presence of disc calcification and axial localization, patients were selected for mini-TTA or transpedicular discectomy. Large paramedian calcified discs were nearly always operated through mini-TTA, and patients with smaller lateral herniated discs were mostly operated by a posterior approach. Possibly, two different patient populations were studied. Ideally, future randomized controlled studies seemed to be warranted. However, in our opinion, a golden standard will be difficult
ASIA, American Spinal Injury Association; TTA, transthoracic approach. In the mini-TTA group, 28 patients (50%) improved one or more grades on the ASIA scale versus 15 patients (37%) in the transpedicular group (p5.19).
Mean FU in (mo) (range) VAS thoracic pain (mm) (range) Good outcome Symptoms Local thoracic back pain Radicular pain Sensory deficit legs Motor deficit legs Pulmonary discomfort
Mini-TTA (N544)
Transpedicular (N533)
p Value
29.1 (3–64) 29.9 (0–100)
26.6 (4–64) 36.1 (0–92)
.51 .38
32 (72)
25 (76)
.80
9 18 29 19 6
13 9 16 12
(20) (41) (66) (43) (14)
(39) (27) (48) (36)
0
TTA, transthoracic approach; FU, follow-up; VAS, Visual Analog Score. Likert good recovery is defined as ‘‘complete recovery,’’ ‘‘almost complete recovery,’’ and ‘‘some recovery.’’
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Fig. 5. Postoperative (Left) X-ray, (Middle) computed tomography, and (Right) magnetic resonance image of mini-transthoracic approach removal of a large calcified herniated disc T9–T10, with supplemental instrumentation (same patient as in Figs. 1 and 3). (Left) Whenever more than 25% of the craniocaudal extent of the vertebral body had to be removed, additional anterior bicortical screw and rod fixation was performed to prevent iatrogenic scoliosis. (Middle and Right) The herniated disc was removed completely and the spinal cord was adequately decompressed.
to obtain through randomized controlled trials because the approach will be defined not only by the surgeon’s preference, but, more importantly, by the consistency of the herniated disc and its relation to the spinal cord. We are confident that a randomized trial on posterior approach versus anterolateral approach for large calcified and medially located herniated thoracic discs will not be approved. The optimal approach for laterally located disc herniation on the other hand, is still open for discussion. However, considering the risk of complications and duration of hospital stay, there seems to be a slight preference for a posterolateral approach based on the results of the present study. This is in agreement with the data of Bransford et al. [10]. The surgical treatment of patients with symptomatic thoracic disc herniations can be challenging and may be associated with varying risks. Therefore, these complex spinal procedures should be concentrated in supraregional experienced spine centers with high-volume patient care. The treatment algorithm for the optimal surgical approach should consist of MRI, CT, and conventional radiograph of the lumbar spine. The latter is mandatory for documentation of possible transition spine, which is one of the pitfalls of wrong level surgery. Additional CT focusing on axial localization and presence of calcifications is also essential because MRIs of calcified and noncalcified herniated discs can be similar (Figs. 1 and 2). Based on our experience, patients with large calcified paramedian herniated discs should be treated with mini-TTA. All other patients can be treated by posterolateral approach.
There is no consensus whether routine instrumentation is needed in patients with thoracic herniated discs [10,13,17,18]. We have instrumented 9 of 56 patients of the mini-TTA group and none of the posterior group. Whenever more than 25% of the craniocaudal extent of the adjacent vertebral body was reduced to remove the herniated disc safely, we performed an additional fusion with placement of bicortical screws and rod fixation (Fig. 5). In this way, iatrogenic scoliosis will be prevented. In our opinion, supplemental fusion is not needed in patients with posterior removal of thoracic disc herniation because the unilateral pedicle and facet joints are only partially reduced and instability is not likely. Also, bony removal of the adjacent vertebral bodies is limited in case of noncalcified or lateral herniated discs. In conclusion, the long-term surgical outcome of thoracic disc herniation was favourable in most cases treated with mini-TTA and posterolateral discectomy. The complication rate of transthoracic procedures was higher and mainly related to pulmonary morbidity, and the neurologic complications were not different between both approaches. Patients with calcified herniated discs should be informed about the additional risk of cerebrospinal fluid leakage. Based on this experience, it is our opinion that large calcified paramedian herniated discs are best treated by an anterior approach, whereas noncalcified or lateral herniated discs can be treated from posterior as well. Because the entity is rare, its treatment should be concentrated in experienced centers to optimize the surgical strategy for each specific thoracic herniated disc.
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