Tae-Ahn Jahng

Giant invasive spinal schwannoma: its clinical features and surgical management.

BACKGROUND Giant invasive spinal schwannoma (GISS) is defined as a lesion that extends over > 2 vertebral levels, erodes vertebral bodies, and extends posteriorly and laterally into the myofascial planes. Because of its rarity, few reports have been issued. OBJECTIVE To analyze the clinical features and outcomes of GISS and to discuss surgical strategies. METHODS We analyzed the medical records, pathological findings, and radiographic studies of patients with GISS. RESULTS Fourteen patients with GISS were surgically treated between 2002 and 2007. Five lesions were in the sacral region, 4 in the lumbosacral, 2 in the thoracolumbar, and 1 each in the cervical, cervicothoracic, and thoracic regions. Gross total resection was performed in 11 of the 14 patients. Satisfactory decompression was performed in all patients for neural compression. Postoperatively, all patients showed relief of preoperative pain and paresthesia. The growth potential with the Ki-67 index was > 2% in 6 patients, and 4 of them experienced tumor regrowth or recurrence. All patients were followed up for at least 24 months. Final follow-up magnetic resonance images showed asymptomatic small tumor recurrence on the sacrum in 2 patients. Two patients required spinal stabilization. No instability was found on follow-up. CONCLUSION Total resection is the treatment of choice for patients with GISS and provides functional improvements, low permanent morbidity, and a low rate of recurrence. Total resection of the intraspinal portion and regular follow-up with consideration of the Ki-67 index is recommended when total resection is not achieved.

Comparison of the biomechanical effect of pedicle-based dynamic stabilization: a study using finite element analysis.

BACKGROUND CONTEXT Recently, nonfusion pedicle-based dynamic stabilization systems (PBDSs) have been developed and used in the management of degenerative lumbar spinal diseases. Still effects on spinal kinematics and clinical effects are controversial. Little biomechanical information exists for providing biomechanical characteristics of pedicle-based dynamic stabilization according to the PBDS design before clinical implementation. PURPOSE To investigate the effects of implanting PBDSs into the spinal functional unit and elucidate the differences in biomechanical characteristics according to different materials and design. STUDY DESIGN The biomechanical effects of implantation of PBDS were investigated using the nonlinear three-dimensional finite element model of L4-L5. METHODS An already validated three-dimensional, intact osteoligamentous L4-L5 finite element model was modified to incorporate the insertion of pedicle screws. The implanted models were constructed after modifying the intact model to simulate postoperative changes using four different fixation systems. Four models instrumented with PBDS (Dynesys, NFlex, and polyetheretherketone [PEEK]) and rigid fixation systems (conventional titanium rod) were developed for comparison. The instrumented models were compared with those of the intact and rigid fixation model. Range of motion (ROM) in three motion planes, center of rotation (COR), force on the facet joint, and von Mises stress distribution on the vertebral body and implants with flexion-extension were compared among the models. RESULTS Simulated results demonstrated that implanted segments with PBDSs have limited ROM when compared with the intact spine. Flexion motion was the most limited, and axial rotation was the least limited, after device implantation. Among the PBDS selected in this analysis, the NFlex system had the closest instantaneous COR compared with the intact model and a higher ROM compared with other PBDS. Contact force on the facet joint in extension increased with an increase of moment in Dynesys and NFlex; however, the rigid or PEEK rod fixation revealed no facet contact force. CONCLUSIONS Implanted segments with PBDSs have limited ROM when compared with the intact spine. Center of rotation and stress distribution differed according to the design and materials used. These biomechanical effects produced a nonphysiological stress on the functional spinal unit when they were implanted. The biomechanical effects of current PBDSs should be carefully considered before clinical implementation.

Comparisons of outcomes after single or multilevel dynamic stabilization: effects on adjacent segment.

Study Design A retrospective study. Objectives To compare the clinical/radiologic outcomes and effects on adjacent segments by Dynesys stabilization. Summary of Background Data Dynamic stabilization is known to preserve some range of motion (ROM) and to lessen the load on adjacent levels compared with rigid fixation. However, there is concern about the stiffness of Dynesys. In a long-term follow-up study (>4 y), motion of Dynesys was preserved in only 8% of patients and adjacent segment degeneration occurred up to 47% of patients. Little information is available about the risk factor regarding adjacent segment motion. Methods Twenty-one patients underwent lumbar spine stabilization with Dynesys owing to degenerative spinal disease (single, 7; multiple-level, 14). Clinical outcomes were evaluated using K-ODI, VAS, and MacNab criteria. Radiologic evaluations included whole spine AP/lateral, lumbar neutral, flexion, and extension x-ray. Follow-up period was 31±14 months. Single (group A) and multiple-level stabilization (group B, average 2.3 levels) were compared. Results Clinical improvement was not different between the 2 groups (P>0.05). Sagittal balance, lumbar lordosis, ROM of the lumbar spine, pelvic tilt, and sacral slope were not changed postoperatively (P>0.05) in either group. Postoperatively, ROM of stabilized segments were significantly decreased from 12.8±4.8 degrees to 3.9±5 degrees, while ROM of segments above was increased in both groups (P<0.01). Disc height was not decreased in either group (P>0.05). However, retrolisthesis was observed on adjacent segments above in 6 patients only in group B, which may suggests adjacent segment problem. Conclusions Clinically, dynamic stabilization is a good alternative treatment option for degenerative spinal disease. However, dynamic stabilization preserves only limited motion and may cause stress on the adjacent level above. Adjacent segment disease may be closely monitored, especially in cases of multiple-levels dynamic stabilization.

Comparative analysis of 3 different construct systems for single-level anterior cervical discectomy and fusion: stand-alone cage, iliac graft plus plate augmentation, and cage plus plating.

Study Design: A retrospective cohort-nested longitudinal study. Objective: To evaluate radiologic and clinically functional outcomes after single-level anterior cervical discectomy and fusion (ACDF) using 3 different fusion construct systems applying an accurate and reliable methodology. Summary of Background Data: ACDF is an established procedure that uses 3 different fusion construct systems: cage alone (CA), iliac tricortical bone block with plate (IP), and cage with plate construct (CP). The outcome of a previous study is quite different and did not correlate with experimental studies. Methods: ACDF was performed on 158 patients (90 male and 68 female), who were followed up for >12 months. The patients were divided into the following 3 treatment groups: CA, IP, and CP. Factors related to outcome were also evaluated. Fusion rate, subsidence rate, and cervical angles were used to measure radiologic outcome. The Odom criteria and the visual analog scale were used to evaluate the clinical outcome. Results: The fusion rate was higher for patients in the IP (87.1%) and CP (79.5%) groups than for those in the CA group (63.2%) after 12 months of follow-up (P=0.019). The subsidence rate was lower for patients in the IP (28.1%) and CP (38.5%) groups than for those in the CA group (58.6%) (P=0.010). Subsidence occurred for the anterior height regardless of constructs. Radiating arm pain showed greater relief in the CP group than in the CA group (P=0.015). It improved more in the CP group than in the IP group, but the differences were not statistically significant (P=0.388). Other clinical outcomes did not show significant differences. Conclusions: The trend of excellent radiologic outcome was observed for IP≥CP>CA. Plating may play a key role in the support of anterior height. As a result, plating prevents segmental kyphosis and subsidence and promotes bone fusion. Although the overall clinical outcomes were not different among the 3 groups, except for arm pain, more favorable trends regarding clinical outcome were observed for CP≥IP>CA.

Laminoplasty versus laminectomy and fusion for multilevel cervical myelopathy: a meta-analysis of clinical and radiological outcomes

OBJECT Posterior cervical surgery, expansive laminoplasty (EL) or laminectomy followed by fusion (LF), is usually performed in patients with multilevel (≥ 3) cervical spondylotic myelopathy (CSM). However, the superiority of either of these techniques is still open to debate. The aim of this study was to compare clinical outcomes and postoperative kyphosis in patients undergoing EL versus LF by performing a meta-analysis. METHODS Included in the meta-analysis were all studies of EL versus LF in adults with multilevel CSM in MEDLINE (PubMed), EMBASE, and the Cochrane library. A random-effects model was applied to pool data using the mean difference (MD) for continuous outcomes, such as the Japanese Orthopaedic Association (JOA) grade, the cervical curvature index (CCI), and the visual analog scale (VAS) score for neck pain. RESULTS Seven studies comprising 302 and 290 patients treated with EL and LF, respectively, were included in the final analyses. Both treatment groups showed slight cervical lordosis and moderate neck pain in the baseline state. Both groups were similarly improved in JOA grade (MD 0.09, 95% CI -0.37 to 0.54, p = 0.07) and neck pain VAS score (MD -0.33, 95% CI -1.50 to 0.84, p = 0.58). Both groups evenly lost cervical lordosis. In the LF group lordosis seemed to be preserved in long-term follow-up studies, although the difference between the 2 treatment groups was not statistically significant. CONCLUSIONS Both EL and LF lead to clinical improvement and loss of lordosis evenly. There is no evidence to support EL over LF in the treatment of multilevel CSM. Any superiority between EL and LF remains in question, although the LF group shows favorable long-term results.

Direct decompressive surgery followed by radiotherapy versus radiotherapy alone for metastatic epidural spinal cord compression: a meta-analysis.

Study Design. A systemic review and meta-analysis. Objective. To compare the ambulatory status and survival for metastatic epidural spinal cord compression (MESCC) in patients treated with direct decompressive surgical resection (DDSR) followed by radiotherapy (RTx) with those in patients treated with RTx alone. Summary of Background Data. Surgical techniques have remarkably evolved from decompressive laminectomy without ventral tumor excision to DDSR, which has displayed favorable outcomes since the 2000s. RTx alone has also evolved and is regarded to have accomplished outcome comparable with that of the surgery. The optimal treatment of MESCC has not been clearly defined yet. Methods. We searched MEDLINE, EMBASE, and the Cochrane library in July 2013. Comparative studies enrolled patients with similar performance, primary cancer, age, and sex at the baseline state were included. Outcome measures included ambulatory status and overall survival rate. We did a fixed-effects meta-analysis of the ambulatory status and survival in patients with MESCC compared with DDSR+RTx and RTx alone. Results. Five studies were used to obtain data from 238 and 1137 patients treated with DDSR+RTx and RTx alone, respectively. The DDSR+RTx group displayed substantial improvement in ambulatory status after the treatment that was superior to the improvement in the RTx-alone group (relative risk [RR], 1.43; 95% confidence interval [CI], 1.14–1.78) in a fixed-effects model and significantly lower deterioration after treatment than the RTx group (RR, 0.35; 95% CI, 0.19–0.63). The DDSR+RTx group showed significant improvement in the survival rate at 6 months post-treatment (RR, 1.21; 95% CI, 1.09–1.33). Similar findings were observed at 12 months post-treatment (RR, 1.32; 95% CI, 1.12–1.56). Conclusion. The meta-analysis indicates that DDSR+RTx may produce better clinical improvement of ambulation status and survival than RTx alone in the treatment of MESCC. Additional prospective studies are warranted to better address this question. Level of Evidence: 1

Postoperative survival and ambulatory outcome in metastatic spinal tumors : prognostic factor analysis.

OBJECTIVE The purposes of this study are to estimate postoperative survival and ambulatory outcome and to identify prognostic factors thereafter of metastatic spinal tumors in a single institute. METHODS We reviewed the medical records of 182 patients who underwent surgery for a metastatic spinal tumor from January 1987 to January 2009 retrospectively. Twelve potential prognostic factors (age, gender, primary tumor, extent and location of spinal metastases, interval between primary tumor diagnosis and metastatic spinal cord compression, preoperative treatment, surgical approach and extent, preoperative Eastern Cooperative Oncology Group (ECOG) performance status, Nurick score, Tokuhashi and Tomita score) were investigated. RESULTS The median survival of the entire patients was 8 months. Of the 182 patients, 80 (44%) died within 6 months after surgery, 113 (62%) died within 1 year after surgery, 138 (76%) died within 2 years after surgery. Postoperatively 47 (26%) patients had improvement in ambulatory function, 126 (69%) had no change, and 9 (5%) had deterioration. On multivariate analysis, better ambulatory outcome was associated with being ambulatory before surgery (p=0.026) and lower preoperative ECOG score (p=0.016). Survival rate was affected by preoperative ECOG performance status (p<0.001) and Tomita score (p<0.001). CONCLUSION Survival after metastatic spinal tumor surgery was dependent on preoperative ECOG performance status and Tomita score. The ambulatory functional outcomes after surgery were dependent on preoperative ambulatory status and preoperative ECOG performance status. Thus, prompt decompressive surgery may be warranted to improve patients survival and gait, before general condition and ambulatory function of patient become worse.

Post-laminectomy kyphosis in patients with cervical ossification of the posterior longitudinal ligament : does it cause neurological deterioration?

OBJECTIVE Total laminectomy (TL) is an effective surgical technique for the treatment of cervical ossification of the posterior longitudinal ligament (OPLL) along multiple levels. However, kyphosis and probable neurological deterioration have been frequently reported after laminectomy. We analyzed the changes in the cervical curvature after TL and subsequent changes in neurological status. METHODS We retrospectively reviewed the records of 14 patients who underwent TL for the treatment of cervical OPLL between Jan. 1998 and Dec. 2003. TL was selected according to the previously determined criteria. The curvature of the cervical spine was visualized on a lateral cervical spine X-ray and measured using Ishiharas Curvature Index (CI) before the operation and at the last follow-up examination. Perioperative neurological status was estimated using the modified Japanese Orthopedic Association score and the Improvement Rate (IR) at the same time as the images were evaluated. RESULTS The mean age of the patients was 57 years, the male/female ratio was 10:4, and the mean follow-up period was 41 months. The mean number of OPLL was 4.9, and the mean number of operated levels was also 4.9. The CI decreased after TL (p=0.002), which was indicative of a kyphotic change. However, this kyphotic change showed no correlation with the length of the follow-up period, number of operated levels and preoperative CI. Neurological examination at the last follow-up showed an improved neurological status in all patients (p=0.001). There was no neurological deterioration in any case during the follow-up period. Moreover, there was no correlation between IR and the degree of kyphotic change. Postoperative complications, such as C5 radiculopathy and epidural bleeding, resolved spontaneously without neurological sequelae. CONCLUSION Kyphotic change was observed in all but one patient who underwent TL for the treatment of cervical OPLL. However, we did not find any contributing factors to kyphosis or evidence of postoperative neurological deterioration.

Spinal Dural Arteriovenous Fistulas: Clinical Experience with Endovascular Treatment as a Primary Therapeutic Modality

OBJECTIVE The aim of this study was to evaluate the efficacy of endovascular therapy as a primary treatment for spinal dural arteriovenous fistula (DAVF). METHODS The authors reviewed 18 patients with spinal DAVFs for whom endovascular therapy was considered as an initial treatment at a single institute between 1993 and 2006. NBCA embolization was considered the primary treatment of choice, with surgery reserved for patients in whom endovascular treatment failed. RESULTS Surgery was performed as the primary treatment in one patient because the anterior spinal artery originated from the same arterial pedicle as the artery feeding the fistula. Embolization was used as the primary treatment modality in 17 patients, with an initial success rate of 82.4%. Two patients with incomplete embolization had to undergo surgery. One patient underwent multiple embolizations, which failed to completely occlude the fistula but relieved the patients symptoms. Spinal DAVF recurred in two patients (one collateral development and one recanalization) during the follow-up period. The collateral development was obliterated by repeated embolization, but the patient with recanalization refused further treatment. The overall clinical status improved in 15 patients (83.3%) during the follow-up period. CONCLUSION Endovascular therapy can be successfully used as a primary treatment for the majority of patients with spinal DAVFs. Although it is difficult to perform in some patients, endovascular embolization should be the primary treatment of choice for spinal DAVF.

Long-term outcome of laminectomy for cervical ossification of the posterior longitudinal ligament

OBJECT Although laminectomy is an effective surgical technique for the treatment of multilevel cervical stenotic lesions, postoperative kyphosis and neurological deterioration have been frequently reported after laminectomy. Hence, laminectomy without fusion is seldom performed nowadays. However, the clinical impression from the long-term follow-up of patients who had undergone laminectomy does not support that postoperative kyphosis is common in patients with ossification of the posterior longitudinal ligament (OPLL). In this paper, the authors assessed the long-term outcome of laminectomy for cervical OPLL in terms of the changes in the cervical curvature and in the neurological status. METHODS The authors retrospectively reviewed medical records and radiological images in patients who had undergone cervical laminectomy between 1999 and 2009. The preoperative and the final follow-up status recovery rate were assessed using the Japanese Orthopaedic Association (JOA) scale. The cervical global angle and range of motion (ROM) were measured preoperatively and at the last follow-up. The cervical spine was classified into 3 types: lordotic, straight, and kyphotic. RESULTS A total of 34 patients were available for medical record review and telephone interviews. There were 28 men and 6 women, whose mean age at the time of surgery was 57.8 years. The mean follow-up period was 57.5 months. The mean preoperative JOA score was 10.7, and the JOA score at the last follow-up was significantly improved to 14.3 (p < 0.001) with a recovery rate of 56.3%. The JOA score at each postoperative follow-up point increased until 6 years postoperatively; thereafter, it gradually decreased. The mean preoperative global angle was -11.3° and the most recent global angle was -8.4°. The preoperative ROM was 33.9° and the most recent ROM was 27.4°. There was no statistical significance in the change of cervical curvature or ROM. Preoperatively, 29 of the 34 patients had a lordotic cervical curvature and 5 patients had a straight spine. At last follow-up, 24 patients had a lordotic curvature, 3 patients changed from lordosis to kyphosis, and 7 patients had a straight spine. One patient whose cervical curvature changed from lordosis to kyphosis during the follow-up period underwent cervical fusion 9 years after the laminectomy procedure. CONCLUSIONS The long-term outcome of laminectomy for cervical OPLL is satisfactory in terms of the clinical and radiological aspects. The risk of postlaminectomy kyphosis was not high, raising the possibility that the OPLL itself may serve as a support for the spinal column.