Faculty Bibliography

For medulloblastoma patients, the current therapeutic paradigm of surgery followed by radiation and chemotherapy can lead to long-term remission. However, the sequelae of treatment can be very debilitating, particularly in young children. Immunotherapy is an attractive treatment approach to optimize the targeting of tumor cells while sparing the vulnerable surrounding brain that is still developing in children. Understanding the relationship between medulloblastoma and the immune system is critical to develop effective immunologic-based treatment strategies for these patients. This review focuses on current knowledge of tumor immunology and the factors that contribute to the lack of immune system recognition of these tumors. The specificity of tumor antigens present in medulloblastoma is also discussed along with a summary of early clinical immunotherapy results.

STUDY DESIGN/METHODS:Retrospective review of consecutive case series. OBJECTIVE:To assess the safety and efficacy of the microendoscopic approach for treatment of recurrent lumbar disc herniation. SUMMARY OF BACKGROUND DATA/BACKGROUND:The standard surgical approach for the treatment of recurrent disc herniation uses an open technique with a wide exposure. Many would consider a minimally invasive approach such as microendoscopic discectomy (MED) to be contraindicated in the setting of recurrent disc herniation. METHODS:Sixteen consecutive patients with recurrent lumbar disc herniation who failed conservative management underwent MED. Before surgery and at follow-up, patients completed the Oswestry Disability Index, SF-36, and assessment of leg pain using the Visual Analog Scale. Outcome was also assessed using modified McNab criteria. RESULTS:No case required conversion to an open procedure. Mean operative time was 108 minutes, and mean estimated blood loss was 32 mL. The only surgical complications were 2 durotomies that were treated with dural sealant without sequelae. Mean hospital stay was 23 hours, and mean follow-up was 14.7 months. Approximately 80% of patients had good or excellent outcomes based on modified McNab criteria. The remaining 3 patients had fair outcomes, and no patient had a poor outcome. All standardized measures improved significantly, including mean Visual Analog Scale for leg pain (8.2 to 2.2, P<0.001), mean Oswestry Disability Index (59.3 to 26.7, P<0.001), SF-36 Physical Component Summary score (28.3 to 42.4, P<0.001), and SF-36 Mental Component Summary score (38.2 to 48.3, P<0.001). As of last follow-up no patient has showed recurrence of herniation or evidence of delayed instability. CONCLUSIONS:MED is a safe and effective surgical approach for the treatment of recurrent lumbar disc herniation. Standardized measures of outcome show that MED for recurrent herniation produces improvement in pain, disability, and functional health that is at least comparable with outcomes reported for conventional open microdiscectomy.

BACKGROUND:Minimally invasive approaches to intradural pathology have evolved in part in an effort to reduce approach related destabilization of the spine. No biomechanical data exist however evaluating the effects of traditional and minimally invasive exposures. METHODS:A finite element model of the lumbar spine was generated, and a simulated open laminectomy and a modified hemilaminectomy at L4 were performed. Forces were applied to assess changes in flexion, extension, axial rotation, and lateral bending. FINDINGS/RESULTS:Open laminectomy produced much greater changes in extension, flexion, and axial rotation than the modified hemilaminectomy from the intact. Lateral bending was similarly unaffected for both exposures. INTERPRETATION/CONCLUSIONS:The results suggest that a minimally invasive hemilaminar exposure preserves the structural integrity of the lumbar spine and minimizes alterations to segmental motion postoperatively.

STUDY DESIGN/METHODS:A cadaver study comparing 3 different minimally invasive approaches to the anterior thoracic spine. OBJECTIVE:To assess the feasibility of minimally invasive thoracic corpectomy from a posterolateral approach and to compare surgical results from 3 approaches. SUMMARY OF BACKGROUND DATA/BACKGROUND:Traditional posterolateral approaches to the thoracic spine are effective but are associated with a high rate of operative morbidity. METHODS:Thoracic corpectomies were performed using a modified tubular retractor starting at 3, 6, and 9 cm off of midline. Postoperative computed tomography scans were performed and analyzed to assess the extent of corpectomy and ventral decompression. RESULTS:From 3 to 6 to 9 cm, a significant difference in extent of corpectomy (65.8%, 81.5%, and 82.6%, P=0.02) and ventral decompression (83.6%, 90.4%, 94.6%, P=0.05) was noted between 3 cm and the more lateral approaches. The 9 cm approach required more rib resection and average working distances of 8.4 to 11.3 cm, which made the procedure more difficult technically and less suited to the length of standard instruments. CONCLUSIONS:Minimally invasive thoracic corpectomy is feasible and a 6 cm approach off of midline appears optimal.

Hemangioblastomas occur in 2% to 15% of reported series of intramedullary spinal cord tumors. They are benign, highly vascular tumors that can be cured with surgical resection. Complete removal of these tumors with low morbidity is possible with current microneurosurgical techniques and a thorough understanding of the typical relationship of the tumor to adjacent neural structures. We describe our experience with 16 intramedullary and 2 lumbosacral nerve root hemangioblastomas and review the relevant published literature. A detailed discussion of the operative technique is provided along with an operative video. Three illustrative cases are used to demonstrate clinical considerations that can arise with these tumors, including surgery during pregnancy, symptoms related to syrinx or syringomyelia, and postoperative consequences of neurological deficits.

STUDY DESIGN/METHODS:A validated finite element model of the intact lumbar spine (L1-S1) was modified to study the biomechanical changes as a result of surgical alteration for treatment of stenosis at L3-L4 and L4-L5 using 2 established techniques and 1 new minimally invasive technique. OBJECTIVE:To investigate the impact of graded posterior element removal associated with new surgical techniques on postoperative segmental motion and loading in the annulus. SUMMARY OF BACKGROUND DATA/BACKGROUND:Several studies have shown that laminectomy increases and produces segmental instability unless fusion is performed. However, no data exist comparing the biomechanical impact of completely preserving the contralateral anatomy and what effect this has compared to traditional approaches. METHODS:The effect of graded removal of posterior elements because of iatrogenic change associated with the 3 approaches was investigated using an 800 N compressive preload using the follower load technique and application of 8 Nm flexion, 6 Nm extension, 4 Nm torsion, and 6 Nm lateral bending moments. RESULTS:This study shows that removal of posterior elements for treatment of stenosis at L3-L4 and L4-L5 results in increased flexion-extension and axial rotation at the surgical site. This study also shows that the segmental motion following a traditional laminectomy is greater than the minimally invasive approach in flexion, extension, left and right axial rotation. Moderate preservation of the posterior elements which occurs in the intralaminar approach generates greater segmental motion that the minimally invasive approach in extension, left and right axial rotation. CONCLUSION/CONCLUSIONS:Minimization of bone and ligament removal associated with minimally invasive procedures results in greater preservation of the normal motion of the lumbar spine after surgery. This study suggests that preservation of the posterior spinal elements associated with minimally invasive surgery could minimize the risk of developing de novo postoperative changes in spinal alignment and/or acceleration of facet and disc degeneration.

OBJECTIVE:To demonstrate the feasibility of and initial clinical experience with a novel minimally invasive posterolateral thoracic corpectomy technique. METHODS:Seven procedures were performed on 6 cadavers to determine the feasibility of thoracic corpectomy using a minimally invasive approach. The posterolateral thoracic corpectomies were performed with expandable 22 mm diameter tubular retractor paramedian incisions. The posterolateral aspects of the vertebral bodies were accessed extrapleurally, and complete corpectomies were performed. Intraprocedural fluoroscopy and postoperative computed tomography were used to assess the degree of decompression. In addition, 2 clinical cases of T6 burst fracture, 1 T4-T5 plasmacytoma, and 1 T12 colon cancer metastasis were treated using this minimally invasive approach. RESULTS:In the cadaveric study, an average of 93% of the ventral canal and 80% of the corresponding vertebral body were removed. The pleura and intrathoracic contents were not violated. Adequate exposure was obtained to allow interbody grafting between the adjacent vertebral bodies. The procedures were successfully performed in the 4 clinical cases using a minimally invasive technique, and the patients demonstrated good outcomes. CONCLUSION/CONCLUSIONS:Based on this study, minimally invasive posterolateral thoracic corpectomy safely and successfully allows complete spinal canal decompression without the tissue disruption associated with open thoracotomy. This approach may improve the complication rates that accompany open or even thoracoscopic approaches for thoracic corpectomy and may even allow surgical intervention in patients with significant comorbidities.

OBJECTIVE:This report illustrates the adequacy of minimally invasive exposure for the resection of an intramedullary ependymoma. CLINICAL PRESENTATION/METHODS:The patient presented with a history of upper back pain, but a lesion was found during a workup for increased back pain after a motor vehicle accident. INTERVENTION/METHODS:The intramedullary ependymoma was approached using a muscle-splitting retractor and extended hemilaminar exposure. The tumor was removed using conventional techniques. CONCLUSION/CONCLUSIONS:This minimally invasive exposure is adequate for selected intramedullary lesions and may be especially useful in patients with a high risk of postlaminectomy deformity.

Thoracic spine fusion may be indicated in the surgical treatment of a wide range of pathologies, including trauma, deformity, tumor, and infection. Conventional open procedures for surgical treatment of thoracic spine disease can be associated with significant approach-related morbidity, which has motivated the development of minimally invasive approaches. Thoracoscopy and, later, video-assisted thoracoscopic surgery were developed to address diseases of the thoracic cavity and subsequently adapted for thoracic spine surgery. Although video-assisted thoracoscopic surgery has been used to treat a variety of thoracic spine diseases, its relatively steep learning curve and high rate of pulmonary complications have limited its widespread use. These limitations have motivated the development of minimally invasive posterior approaches to address thoracic spine pathology without the added risk of morbidity involved in surgically entering the chest. Many of these advances are ongoing and represent the forefront of minimally invasive spine surgery. As these techniques are developed and applied, it will be important to assess their equivalence or superiority in comparison with standard open techniques using prospective trials. In this paper the authors focus on minimally invasive posterior thoracic procedures that include fusion, and provide a review of the current literature, a discussion of future pathways for development, and case examples. The topic is divided by pathology into sections including trauma, deformity, spinal column tumors, and osteomyelitis.