Srinath Samudrala

CADAVERIC MORPHOMETRIC ANALYSIS FOR ATLANTAL LATERAL MASS SCREW PLACEMENT

OBJECTIVE:Atlantal lateral mass screws provide an alternative to C1/C2 transarticular screws and, in some cases, can obviate the need for extending a fusion to the occiput. For these reasons, C1 lateral mass screws are becoming increasingly popular. However, the critical local anatomy and unfamiliarity with this new technique can make C1 screw placement more challenging. METHODS:Morphometric analysis was performed on 74 cadaveric spines obtained from the Department of Anatomy at the Keck School of Medicine, University of Southern California. Critical measurements were determined for screw entry points, trajectories, and lengths for application of the technique described by Harms and Melcher. RESULTS:The mean height and width for screw entry on the posterior surface of the lateral mass were 3.9 and 7.3 mm, respectively. The maximum medialized screw trajectory ranged from 25 to 45 degrees (mean, 33 degrees). The mean maximal screw length to obtain bicortical purchase was 22.5 mm, and the mean minimum screw depth was 14.4 mm. Screw depths varied on the basis of the entry point, trajectory, and vertebral morphology. The overhang of the posterior arch averaged 11.4 mm (range, 6.9–17 mm). All specimens could accommodate 3.5-mm lateral mass screws bilaterally with proper preparation of the entry site. CONCLUSION:Significant variations in the morphology of C1 exist. However, the large size of the atlantal lateral mass makes screw placement forgiving. Preoperative computed tomographic scans and intraoperative fluoroscopy are useful in guiding proper screw placement. Close attention should be paid to preparation of the screw entry site.

Cervicothoracic junction kyphosis: surgical reconstruction with pedicle subtraction osteotomy and Smith-Petersen osteotomy. Presented at the 2009 Joint Spine Section Meeting. Clinical article.

OBJECT Sagittal plane deformities can be subdivided into kyphotic and lordotic forms and further characterized according to their global or regional (focal) presentation. Regional deformities of a significant magnitude constitute a gibbous deformity. Pedicle subtraction osteotomy (PSO) and interlaminar Smith-Petersen osteotomies have been used to correct sagittal plane deformities in the cervical, thoracic, and lumbar spine. By resecting a portion of the vertebral body and closing in the gap of this vertebra, the spine is placed in local lordosis and kyphosis is corrected. These osteotomies have generally been carried out in the lumbar or less frequently in the thoracic area. While PSO has been performed in the mid and lower thoracic spine, there have been no case series of patients undergoing PSO at the CTJ. Specifically, a PSO approach that addresses the challenges of the CTJ is needed. Here, the authors review their case series of PSOs performed in the CTJ. Their goal in the treatment of these patients was to correct the regional CTJ kyphosis, restore forward gaze, and reduce the pain associated with the deformity. METHODS Eight patients (5 males and 3 females, mean age 63 years) underwent PSO for the correction of CTJ kyphosis. Pedicle subtraction osteotomy was performed at C-7 or the upper thoracic vertebrae and was facilitated by a computer-guided intraoperative monitoring system. Surgical indications included postlaminectomy kyphosis, spinal cord tumor resection, posttraumatic kyphosis, and degenerative cervical spondylosis. RESULTS The mean follow-up was 15.3 months (range 12-20 months), and the mean preoperative CTJ kyphosis was 38.67° (range 25°-60°). Clinically satisfactory correction of the regional deformity was accomplished in all patients, achieving a mean correction of 35.63° (range 15°-66°) at the CTJ, with restoration of forward gaze and significant reduction in pain. CONCLUSIONS A CTJ deformity is a distinctive form of kyphosis that presents as a variable local deformity and requires complex spinal reconstructive techniques to restore sagittal balance and forward gaze. Pedicle subtraction osteotomy allows for significant correction through one spinal segment, and it can be used safely to correct the regional sagittal alignment of the cervical spine and head in relation to the pelvis. Pedicle subtraction osteotomy can be used alone or in combination with other techniques as some patients may require multistage procedures with anterior and posterior spinal reconstruction to obtain stable sagittal correction. All deformities in these patients were kyphotic in nature with only mild elements of scoliosis or coronal plane deformity. This is unlike lumbar and thoracic curves where the kyphosis is frequently associated with scoliosis.

Image-guided thoracoscopic resection of thoracic dumbbell nerve sheath tumors.

BACKGROUND: Surgical removal of dumbbell nerve sheath tumors (NSTs) remains challenging because these neoplasms occupy ≥ 2 spinal and extraspinal spaces. The presence of intraspinal extension, tumor dimension, and/or its location within the thoracic cavity have previously made the resection of these types of neoplasms difficult. OBJECTIVE: To describe the feasibility of performing minimally invasive thoracoscopic surgery, as facilitated by an image guidance system (IGS), to achieve gross total resection of select dumbbell NSTs located in the thoracic spine. METHODS: The 3 cases presented here contained small intraspinal or foraminal components. Preoperative symptoms included Horner syndrome and back and chest wall pain. We used IGS to help guide the complete thoracoscopic resection of select dumbbell NSTs, consisting of extradural, intraforaminal, and paravertebral tumor components, which previously would have been challenging with only a thoracoscopic approach. RESULTS: IGS provided continuous intraoperative anatomic orientation to achieve gross total resection in all 3 cases. All surgical and postsurgical outcomes were satisfactory; preoperative symptoms improved or resolved; and no adverse events were observed. CONCLUSION: Thoracic dumbbell NSTs that have small intraspinal or foraminal components could be resected thoracoscopically when facilitated by IGS. Image-guided thoracoscopic resection of such dumbbell tumors may not only improve the precision of resection, reduce recurrence, and avoid the need for spinal reconstruction but also obviate the need for more invasive or simultaneous posterior procedures. The IGS enhances the accuracy and safety of 2-dimensional thoracoscopic surgery and may reduce its learning curve.

The rare case of an intramedullary cervical spinal cord teratoma in an elderly adult: case report and literature review.

Study Design. Case report and literature review. Objectives. To report the very rare case of a mature intramedullary teratoma with exophytic extension localized to the uppermost cervical spinal level in a 65-year-old woman and review the pertinent medical literature. Summary of Background Data. Cervical intramedullary teratomas are extremely rare in adults, especially in patients older than 50 years. Methods. The patient presented with progressive ataxia, mild bilateral kinetic hand tremors, and dizziness. Magnetic resonance imaging revealed an intramedullary 1.7 × 1.3 × 2.3 cm mass at C1 with exophytic extension. A C1–C2 laminectomy and a partial suboccipital craniotomy were performed, followed by a subtotal microscopic resection of the tumor. Pathology was consistent with a mature teratoma. Results. After surgery, the patients ataxia, tremor, and dizziness resolved almost immediately. Conclusion. This report presents the very rare case of a mature intramedullary teratoma located in the upper cervical spine of an elderly patient, possibly the oldest patient documented with this type of lesion. The authors recommend a conservative subtotal surgical resection of cervical intramedullary tumors because it may improve symptoms that relate to direct mechanical cord compression and avoid further harm from a gross resection.

Microvascular decompression for intractable singultus: technical case report.

OBJECTIVE Intractable singultus is a rare but significantly disruptive clinical phenomenon that often accompanies other diseases but can present in isolation due entirely to intracranial pathology. We report a case of intractable singultus that improved after microvascular decompression and present a comprehensive review of singultus by discussing its similarity to other cases of microvascular decompression, its history and etiology, and its evolutionary basis. CLINICAL PRESENTATION The patient exhibited intractable singultus for 15 years, resistant to multiple medical regimens. INTERVENTION Microvascular decompression to relieve pressure on the tenth cranial nerve and medulla oblongata resulted in near total resolution of the singultus. CONCLUSION Neurovascular compression should be considered a potentially reversible cause of intractable singultus, a significantly disabling clinical phenomenon.

Improving C1-C2 Complex Fusion Rates: An Alternate Approach

The surgical repair of atlantoaxial instabilities (AAI) presents complex and unique challenges, originating from abnormalities and/or trauma within the junction regions of the C1-C2 atlas-axis, to surgeons. When this region is destabilized, surgical fusion becomes of key importance in order to prevent spinal cord injury. Several techniques can be utilized to provide for the adequate fusion of the atlantoaxial construct. Nevertheless, many individuals have less than ideal rates of fusion, below 35%-40%, which also involves the C2 nerve root being sacrificed. This suboptimal and unavoidable iatrogenic complication results in the elevated probability of complications typically composed of vertebral artery injury. This review is a retrospective analysis of 87 patients from Cedars Sinai Medical Center in Los Angeles, California, who had the C1-C2 surgical fusion procedure performed within the time frame from 2001 to 2008, with a mean follow-up period of three years. These patients had presented with typical AAI symptoms of fatigability, limited mobility, and clumsiness. Diagnosis of C1-C2 instability was documented via radiographic studies, typically utilizing computed tomography (CT) scans or x-rays. All patients had bilateral C1 lateral masses and C2 pedicle screws. In addition, the C1-C2 joint was accessed by retracting the C2 nerve root superiorly and exposing the joint by utilizing a high-speed burr. The cavity that is developed within the joint is packed with local autologous bone from the cephalad resection of the C2 laminae. Fusion of the C1-C2 joint was achieved in all patients and a final follow-up was conducted approximately three years postoperative. Of the 87 patients, two presented with occipital headaches resulting from the C1 screws impinging on the C2 nerve root. The issue was rectified by removing instrumentation in both patients after documenting complete fusion via radiographic studies, with complete resolution of symptoms. No vertebral artery or spinal cord injuries were reported as a result of the minor complication. Overall, we aim to describe a safe and reliable alternative technique to fuse C1-C2 instability by focusing on intra-articular arthrodesis complementing instrumentation fixation. This methodology is advantageous from a biomechanical standpoint secondary to axial loading, as well as the large surface area available for arthrodesis. Additionally, this technique does not involve the resection of the C2 nerve root, resulting in low risk for vertebral artery or spinal cord injury.

Wednesday, October 30, 2001 4:42–5:25 pm Concurrent Session 2A: Cervical Spine Surgery Complications

Abstract Purpose of study: Significant controversy persists regarding the ideal treatment of an isolated unilateral jumped or locked facet after cervical spine trauma. The purpose of this study was to examine the efficacy and outcomes of such a purely anterior technique for the treatment of a unilateral jumped facet. Methods used: Between 1994 and 2002, a retrospective review was conducted at the Los Angeles County General Hospital to identify a total of 56 patients with cervical spine trauma and unilateral jumped facet syndrome who were subsequently treated by anterior cervical discectomy and fusion. Demographic data, initial neurological examinations, surgical data, radiographic findings and follow-up records were reviewed. The mean follow-up was 14.5 months with greater than 6-month follow-up available in 95% of patients. Treatment failure was identified as progression of cervical deformity, graft or hardware migration, or new neurological deficit. Time to failure was divided arbitrarily into immediate (0 to 4 weeks), early (4 weeks to 3 months), middle (3 to 6 months) and late (longer than 6 months). of findings: We identified a total of 13 treatment failures (23%) documented on delayed radiographic imaging. Within the failure group, the following variables were identified as carrying a negative prognosis as compared with the overall cohort: high-speed mechanisms of trauma (eg, motor vehicle accident vs. simple assault), presence of a motor deficit or numbness, reflex changes, loss of consciousness and/or intracranial bleed, smoking, other systemic diseases, lesions of the cervicothoracic junction (C6–T1), evidence of increased T2-signal or disc changes on the initial magnetic resonance imaging scan, presence of kyphosis or disc height loss at the injured level and successful preoperative halo reduction at a low weight. Of these, high-speed mechanisms, neurological deficit, intracranial bleeding and the presence of kyphosis were statistically significant (p Relationship between findings and existing knowledge: Our observation of a 23% failure rate at a mean interval of 11.2 weeks after anterior reconstruction for unilateral jumped facet syndrome is slightly higher than that previously reported in the literature. This study represents one of the largest single-institution studies from a major trauma center and may reflect a higher proportion of high-impact type injuries. The other negative prognostic variables suggest that a more serious injury was likely initially present in the patients whose anterior construct failed. Overall significance of findings: Careful analysis of the exact injury is needed for cases of cervical unilateral jumped facets. Whereas anterior discectomy and plating may prove adequate for low-impact type injuries, it may be inadequate for more serious cases with higher force injuries. Identification of features suggestive of more serious injury, including the ones listed above, may help guide treating surgeons to identify which patients require circumferential stabilization. Disclosures: No disclosures. Conflict of interest: No conflicts.