The surgical treatment of severe spinal deformities. Posterior Vertebral Column Resection for Rigid Angular Kyphotic Spinal Deformities

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1 WScJ 3: , 2015 Posterior Vertebral Column Resection for Rigid Angular Kyphotic Spinal Deformities Mohamed Wafa, Ahmed Elbadrawi Department of Orthopedics, Ain Shams University, Cairo, Egypt Abstract AIM: To summarize surgical techniques and evaluate results of posterior vertebral column resection (PVCR) in rigid angular kyphotic deformity. The choice of spine mobilization procedures to correct deformity is dependent on several factors including the magnitude of the deformity, its rigidity, presence of previous fusions and the experience of the surgeon. PVCR allows greater three dimensional spine deformity correction especially in advanced rigid angular kyphosis. Material and Methods: Forty cases of rigid kyphotic deformity patients were managed by PVCR and reviewed after mean follow-up of 29.7 ± 4 SD months (range; months). Etiologic diagnoses were congenital kyphosis in 14, post-traumatic kyphosis in 8, postinfectious kyphosis in 8 and Arnold Chiari malformation (type II) in 10 patients with no clinical or radiographic evidence of cervical instability. The mean age at surgery time was ± 2.53 SD years (range; years). The radiographic evaluation included sequential anteroposterior, lateral radiographs of the whole spine. Three-dimensional computer tomography (CT) of the curves was performed to evaluate curve pattern and rule out associating scoliotic deformity. The surgical technique consisted of pedicle screws fixation at the planned levels, circumferential cord decompression, and posterior resection of the planned vertebrae at the apex of the deformity followed by correction and fusion. Results: The mean preoperative Cobb angle was 91.6 ± 9.3 SD (range; ), the average fusion extent was ± 2.49 SD (range; 7-15 vertebrae). Pelvis was included in the fixation in 10 cases. Mean Postoperative Cobb angle was ± 4.9 SD (range; 5-25 ). The following complications were encountered: four patients with superficial wound infection and two patient with pseudoarthrosis that required anterior grafting. Conclusions: PVCR is an effective procedure for the management of rigid angular kyphosis. However, it is technically demanding procedure with possible risks for complications. Key words: Anterior reconstruction, circumferential decompression, pseudoarthrosis, PVCR, rigid kyphosis Introduction The surgical treatment of severe spinal deformities is challenging. Traditionally, a circumferential approach with anterior releases via discectomies, followed by posterior instrumentation and fusion has been the standard of care (12, 17, 18). The use of a vertebrectomy procedure has been around for quite some time as well, with the first description in 1922 by MacLennan (14) who described a posterior apical resection followed by postoperative casting for the treatment of severe scoliosis. Performing a circumferential vertebral column resection (VCR) approach World Spinal Column Journal, Volume 6 / No: 3 / September 2015 for severe rigid spinal deformity was first described by Bradford (1). He describde the use of a circumferential vertebral column resection with concave rib osteotomies, convex thoracoplasty, and segmental spinal instrumentation with fusion in 13 patients with rigid structural spinal deformities. Suk et al (17, 18) reported on a posterior-only approach with a vertebral column resection (PVCR) for fixed lumbar spinal deformities and they reported excellent surgical correction with minimal long-term complications for lumbar deformities resected around the cauda equina region. 107

2 Posterior Vertebral Column Resection for Rigid Angular Kyphotic Spinal Deformities Suk and Lenke et al (10, 17, 18) have suggested that the main advantage of PVCR is simultaneous control of the spinal column and access to the neural elements circumferentially to closely follow both during correction of the deformity. Thus, there is excellent access to the dural sac circumferentially to confirm absence of any type of impingement due to retained bony or disc material during the corrective procedure. This certainly makes the procedure safer from a neurologic prospective. PVCR is a formidable operation reserved for moderate to severe rigid angular deformities with significant spinal decompensation especially when previous fusion has been performed. It should be performed only by surgeons who have worked their way up the learning curve by performing less arduous spine mobilization procedures (10). Patients and methods: The current study was conducted as a randomized prospective study in a series of 40 patients who underwent treatment for rigid angular kyphosis by PVCR. It was held between March 2009 and April 2012, Informed consent was obtained from all individual participants included in the study. Etiologic diagnoses were congenital kyphosis in 14, post-traumatic kyphosis in 8, post infectious kyphosis in 8 and Arnold Chiari malformation type II (AC-II) in 10 patients with no clinical or radiographic evidence of cervical instability. Sagittal Cobb s angle was beyond 80, mean Cobb angle was 91.6 ± 9.3 SD (range ). The main complaints of the patients were inability to lie supine, costo-pelvic impingement and respiratory dysfunction. The neurological status was evaluated using the American Spinal Injury Association (ASIA) scoring system and was grade A in 10 patients, B in 4 patients, C in 6 and D in 20 patients. Radiographic evaluation included sequential anteroposterior (AP) and lateral plain radiographs of the whole spine. A lateral radiograph obtained under traction or with the patient lying supine on a bolster placed under the apex of the curvature to provide information on the flexibility of the deformity. Computed tomography (CT) scans, 3D reconstruction images and Magnetic resonance imaging (MRI) were done for better evaluation of the deformity and to identify the site of needed resection. Regional angulation (RA) at the level of the deformity was drawn between the superior end plate of the adjacent cranial vertebra and the inferior end plate of the adjacent caudal vertebra. At each level, the Effective Regional Deformity (ERD) is defined by subtracting the physiological RA for the level from the measured RA; (ERD = RA - Physiological RA for the level) as reported by Stagnara et al (16). Assessment of radiological fusion at follow up was based on the presence of bridging trabecular bone at the resection site according to Brantigan et al (2,3). Under general anesthesia, the patient was placed in prone position on Maquet operation table. Proper positioning is important during the PVCR procedure in order to avoid excessive pressure points in the axilla and to maintain stability of the trunk. Spinal Cord monitoring using somatosensory evoked potentials was done in all patients except those with AC-II. Posterior midline incision was performed in a centralized manner over the apex of the deformity. In patients with bad skin condition over the apex of the deformity (n=5 patients with AC-II), the incision was modified to be elliptical in shape excising unhealthy skin (Figure 1). Because of the potential for significant bleeding during these surgeries it is important to minimize epidural and os- a B Figure 1: A 9-year-old child with AC-II malformation and 110 degrees dorsolumbar kyphosis. The skin over the apex of the deformity shows marked pressure changes. The incision was planned to be elliptical around the unhealthy skin. 108 World Spinal Column Journal, Volume 6 / No: 3 / September 2015

3 M Wafa and A Elbadrawi seous blood loss by careful subperiosteal stripping of the posterior vertebral elements and using controlled hypotensive anesthesia. To gain access circumferentially around the vertebrae to be resected; after subperiosteal dissection of the posterior vertebral column, blunt dissection around the lateral aspect of the pedicles and vertebral body is performed using Penfield elevators. The soft tissues and the anterior vasculature are held a way with malleable retractors. The segmental vessels are kept lateral in a soft tissue cuff and should not be violated. Pedicle screw fixation was obtained for the appropriate levels which are included in the definitive fusion, at least three pairs of pedicle screws were inserted into the vertebrae cephalic or caudal accordingly with free-handed fashion. Multi-axial screws were recommended for use in order to avoid sagittal translation at the VCR site during correction (10,12). Subperiosteal rib resection and excision of the rib head was done to gain access to lateral and anterior aspects of vertebral bodies and for better mobilization of the curve. At the apex of deformity; Ponte osteotomy followed by laminectomy at apical levels which are planned to be resected were performed. Typically, the lamina of the level to be resected, the lamina cephalad to the pedicles above, and caudad to the pedicles below, were removed. The pedicle screws were connected through a temporary rod at one side (Figure 2). During the resection procedure a circumferential access to the spinal cord and/or cauda equina should be gained for visualizing any dural impingement during the correction. After exposure of the lateral aspects of the apical vertebrae, a working window was created through lateral pedicle-body entrance. Using a high-speed drill, the working window was enlarged cephalad and caudad till the pedicle walls were penetrated and removed using Kerrison rongeurs. The medial wall of the pedicle should be preserved as much as possible to protect nerve roots. Decancellation was continued till accessing the upper, lower end plates and anteriorly till the Anterior Longitudinal Ligament (ALL). Discectomies were done above and below the resected vertebra and lastly the floor of the spinal canal is impacted forward using a reverse angle curette. At this point, a structural bone graft was placed anteriorly and gradual compression was done through the temporary rod, the contralateral permanent rod was secured after proper contouring, and the temporary rod was replaced by another contoured rod (Figure 3). Residual autogenous bone graft was then placed posterior and lateral to help fusion. World Spinal Column Journal, Volume 6 / No: 3 / September 2015 Figure 2: Intraoperative picture of a temporary rod contoured and placed at the left side to allow vertebral resection from the other side (right). Note the suture used to ligate the root to get access to the anterior vertebral aspect that can be used for spinal cord gentle retraction. Figure 3: Intraoperative picture after PVCR with circumferential spinal cord decompression. The temporary rod is replaced by the contoured rods after correction. 109

4 Posterior Vertebral Column Resection for Rigid Angular Kyphotic Spinal Deformities In cases with dorsal spine multiple level corpectomies; insertion of interbody cage (Titanium Pyramesh cage) was done through the posterior approach after resecting the relevant nerve roots to gain access for cage placement. Results The mean operative time was 249 minutes (ranging from 210 to 320 minutes), the mean total blood loss was 850 ml (ranging from 550 ml to 1100 ml), and the mean number of resected vertebrae per case was 2.9 ± 0.73 SD (range; 2-4 vertebrae). The mean preoperative Cobb angle was 91.6 ± 9.3 SD (range ). The mean postoperative Cobb angle was ± 4.9 SD (range; 5-25 ) fig.4. The average ERD significantly decreased from a mean angle of 59 (ranging from 65 to 88 ) preoperatively to 8 (3 to 12 ) after surgery (P<0.018) with a mean correction of 51. ERD averaged 12.2 (9 to 18 ) at the latest follow up with a mean loss of correction of 4.6, and mean follow up was 29.7 ± 4 SD months (range months). Table 1 includes specific demographic, radiographic and clinical data of all patients. The average fusion extent was ± 2.49 SD (range; 7-15 vertebrae). The pelvis was included in the fixation in 10 cases. Post-operative complications included 4 patients with superficial wound infection and 2 patients with pseudoarthrosis that required anterior grafting. Mean hospital stay was 9.2 ± 0.7 SD days (ranging from 7 to 15 days). Patients were allowed to walk wearing a Thoraco- Lumbo-Sacral Orthosis (TLSO) after removing the drains. The TLSO was used for 12 weeks. By the end of the follow up period, preoperative complaints such as inability to lie supine, costo-pelvic impingement and respiratory dysfunction were markedly improved. Discussion Many techniques have been described to achieve a B C Figure 4: a) Sagittal CT scan image of AC-II patient with dorsolumbar kyphosis (110 degrees). B) 3D reconstruction of the dorsolumbar spine in the same patient. C) Postoperative plain X ray of the same patient (with spino-pelvic fixation). Cobb angle (15 degrees), anterior reconstruction was done with a fibular graft. 110 World Spinal Column Journal, Volume 6 / No: 3 / September 2015

5 M Wafa and A Elbadrawi Table 1: Specific demographic, radiographic and clinical data of all patients. Gender M/F Age (years) Pre-operative Cobb angle Post-operative Cobb angle resected vertebrae (n) Fused vertebrae (n) ASIA score Diagnosis Extent of fusion Follow up (months) 1 M A AC- II T6/ pelvis 32 2 M A AC-II T10/pelvis 28 3 M D congenital T4/T F D congenital T6/T M A AC- II T6/ pelvis 24 6 M D congenital T4/L M D congenital T5/L M B traumatic T4/L F D congenital T2/T F C traumatic T6/L M D traumatic T10/L M D congenital T7/L M B infection T5/L M A AC- II T7/ pelvis F D Infection T2/L F D Infection T8/L M C traumatic T7/L F C Infection T3/L F D Congenital T6/L M A AC- II T7/ pelvis F D Congenital T6/L F B traumatic T8/L F D Infection T4/T M D Congenital T2/T M C traumatic T8/L M B Congenital T2/T M A AC- II T6/pelvis M A AC- II T4/pelvis F A AC- II T6/pelvis F C Infection T8/L M A AC- II T4/pelvis F A AC- II T6/pelvis M D Congenital T6/T M D traumatic T6/S F C Infection T2/T M D Congenital T4/L F D Congenital T4/L F D Infection T4/L F D Congenital T6/L M D traumatic T8/L2 27 World Spinal Column Journal, Volume 6 / No: 3 / September

6 Posterior Vertebral Column Resection for Rigid Angular Kyphotic Spinal Deformities correction of severe angular kyphotic deformities of the spine. Traditionally, a circumferential approach with anterior releases via discectomies, followed by posterior instrumentation and fusion has been the standard of care (10, 12). This two-staged procedure allows thorough posterior decompression securing the neural elements during the correction but requires two surgeries with a high incidence of morbidity (10). Posterior spinal osteotomies, typically the Smith Petersen (SPO) and the Pedicle Subtraction Osteotomies (PSO), require anterior mobile disc space that is usually absent in rigid severe kyphosis (4,5,15). Although PSO can be used in angular kyphosis with anteriorly fused disc spaces, it causes excessive shortening that limits the correction to degrees (4,5,13). Therefore neither PSO nor SPO would be suitable to correct severe angular kyphosis (4-6). Single stage posterior VCR has become increasingly popular as it provides significant correction while minimizing the risk of injury to anterior vascular and visceral structures (17-19). Besides providing greater correction at a single vertebral level, PVCR provides a relatively sufficient space that will simultaneously emerge anteriorly (7, 8), which makes it possible to insert an anterior support device, such as an autologous iliac bone or a cage, for restoring normal sagittal alignment. Thus, the incidences of subluxation, residual dorsal impingement, and dural buckling at or near the osteotomy site can be effectively reduced by this technique. Moreover, it yields bony apposition anteriorly and posteriorly, providing greater stability and potential for bony union (17, 18, 20, 21). Suk (17, 18) was the first investigator to promote a posterior only VCR. There was a reduction in the total operating time and amount of blood loss through this one stage posterior-only procedure. In 2005 he described the resection to proceed from lateral to medial. Working through the space created by the resection but not proceeding past the midline, with this technique PVCR offered 53-55% correction of sagittal balance (17). In their series, the total number of resected vertebrae was 143: 76 in thoracic and 67 in lumbar. Mean operation time was 4 hours, 31 minutes with average blood loss of 2333 ml. The deformity correction was 45.2 degrees in the sagittal plane. Complications were encountered in 24 patients: 2 complete cord injuries in severe adult scoliosis and thoracic kyphosis patients who had significant preoperative cord compromise, 6 hematomas, 4 root injuries (all incomplete), 5 fixation failures, 2 infections, and 5 hemopneumothoraxes. At 2009 Lenke et al (11) described posterior only vertebral column resection for correction of rigid pediatric and adult spinal deformities and obtained 63% correction of the angular kyphosis. Kawahara et al (9) modified the procedure by inserting an interbody cage through the posterior approach to improve the correction. In the current series, 40 consecutive patients (116 vertebrae) were managed by posterior VCR for severe pure angular kyphotic deformities and this is complimentary to previous studies. All f the cases were managed by posterior only VCR with a correction rate of 54.3% foe angular kyphosis which is comparable to other correction rates reported in the literature by Suk et al (17,18) and Lenke et al (10-12) using PVCR. As Lenke has suggested, we preferred to perform laminectomy from the inferior pedicles of the level above the resected vertebra and distal to the superior pedicles of the level below the resection as this will create a residual laminectomy defect after closure to allow dural egression posteriorly avoiding impingement, and allow access to the ventral aspect of the dural sac (9). There were no spinal cord related neurologic deficits in any of the patients in this series. The main cause of neurologic deficits is the severe instability of the spine during the procedure and thus it is necessary to restore stability with a dural sac that is free from compression and not excessively shortened ventrally (10, 12), This stability is achieved through properly contoured temporary rod placement, restoring the appropriate anterior height via the anterior cage (fig.5), and maintaining normotensive anesthesia during the correction of these deformities and closure. According to Lenke et al. (9) mean arterial pressure (MAP) of 75 mmhg is sufficient to maintain spinal blood flow. In cases with dorsal spine multiple level corpectomies (table), resection of relevant nerve roots was done to gain access for cage placement. There were no complications. Time to solid bony fusion and percentage of fused cases in the present study were closely correlated with data from the literature: 95 percent of the patients achieved solid bony Fusion took on average 7.1 months postoperatively. Most series report solid bony fusion to occur in over 90 percent of cases (20, 21) and time to fusion as 7.5 to 8.6 months (2, 3). At the latest follow-up, the mean loss of kyphosis correction was 4.6 degrees and there were no clinical problems in any of the patients. 112 World Spinal Column Journal, Volume 6 / No: 3 / September 2015

7 M Wafa and A Elbadrawi a B Figure 5: a) Intraoperative picture after placing the contoured rod and insertion of a Pyramesh cage through posterior approach. B) Postoperative plain X ray of the same patient. In our experience, posterior VCR is most suitable for patients with a pure kyphosis, as the exposure of the vertebral column is easy in these patients. We achieved a mean of 51 correction (54.3% correction of angular kyphosis) which supports previous results by Suk et al (17, 18) and Lenke et al. (9,12). REFERENCES 1. Bradford DS, Tribus CB. Vertebral column resection for the treatment of rigid coronal decompensation. Spine. 22: , Brantigan JW, Steffee AD. A carbon fiber implant to aid interbody lumbar fusion. Two-year clinical results in the first 26 patients. Spine. 18: , Brantigan JW, Steffee AD, Lewis ML, et al. Lumbar interbody fusion using the Brantigan I/F cage for posterior lumbar interbody fusion and the variable pedicle screw placement system: Two-year results from a Food and Drug Administration investigational device exemption clinical trial. Spine 25: , Bridwell KH. Decision making regarding Smith-Petersen vs. pedicle subtraction osteotomy vs. vertebral column resection for spinal deformity. Spine. 31:S , Bridwell KH, Lewis SJ, Rinella A, et al. Pedicle subtraction osteotomy for the treatment of fixed sagittal imbalance: Surgical technique. J Bone Joint Surg Am. 86: 44-50, El-Sharkawi MM, Koptan WM, El-Miligui YH, et al. Comparison between pedicle subtraction osteotomy and anterior corpectomy and plating for correcting post traumatic kyphosis: A multicenter study. Eur Spine J. 20: , Gorensek M, Kosak R, Travnik L, et al. Posterior instrumentation, anterior column reconstruction with single posterior approach for treatment of pyogenic osteomyelitis of thoracic and lumbar spine. Eur Spine J. 22: , Hamzaoglu A, Alanay A, Ozturk C, et al. Posterior vertebral column resection in severe spinal deformities. Spine. 36: , Kawahara N, Tomita K, Kobayashi T, et al. Influence of acute shortening on the spinal cord: an experimental study. Spine. 30: , Lenke LG, Newton PO, Sucato DJ, et al. Complications after 147 consecutive vertebral column resections for severe pediatric spinal deformity: A multicenter analysis. Spine. 38: , Lenke LG, O Leary PT, Bridwell KH, et al. Posterior vertebral column resection for severe pediatric deformity. Minimum two-year followup of thirty-five consecutive patients. Spine. 34: , World Spinal Column Journal, Volume 6 / No: 3 / September

8 Posterior Vertebral Column Resection for Rigid Angular Kyphotic Spinal Deformities 12. Lenke LG, Sides BA, Koester LA, et al. Vertebral column resection for the treatment of severe spinal deformity. Clin Orthop Relat Res. 468: , Li X, Zhang J, Tang H, et al. Closing-opening wedge osteotomy for thoracolumbar traumatic kyphosis. Eur J Med Res. 19:59, MacLennan A. Scoliosis. BMJ. 2: , Smith-Petersen MN, Larson CB, Aufranc OE. Osteotomy of the spine for correction of flexion deformity in rheumatoid arthritis. Clin Orthop Relat Res. 66: 6-9, Stagnara P, De Mauroy JC, Dran G, et al. Reciprocal angulation of vertebral bodies in a sagittal plane: Approach to references for the evaluation of kyphosis and lordosis. Spine 7: , Suk SI, Chung ER, Kim JH, et al. Posterior vertebral column resection for severe rigid scoliosis. Spine. 30: , Suk SI, Kim JH, Kim WJ, et al. Posterior vertebral column resection for severe spinal deformities. Spine. 27: , Wang Y, Zhang Y, Zhang X, et al. Posterior-only multilevel modified vertebral column resection for extremely severe Pott s kyphotic deformity. Eur Spine J. 18: , Zeng Y, Chen Z, Sun C, et al. Posterior surgical correction of posttraumatic kyphosis of the thoracolumbar segment. J Spinal Disord. 26:37-41, Zhang XS, Zhang YG, Wang Z, et al. Correction of severe posttraumatic kyphosis by posterior vertebra column resection. Chin Med J. 123: , 2010 Manuscript submitted June 06, Accepted August 19, Address correspondence to: Ahmed Elbadrawi, Ain Shams University, Orthopedics, Cairo, Egypt ahmedelbadrawi@hotmail.com 114 World Spinal Column Journal, Volume 6 / No: 3 / September 2015