Stephen M. Papadopoulos

Comparison of BRYAN Cervical Disc Arthroplasty With Anterior Cervical Decompression and Fusion : Clinical and Radiographic Results of a Randomized, Controlled, Clinical Trial

Study Design. A prospective, randomized, multicenter study of surgical treatment of cervical disc disease. Objective. To assess the safety and efficacy of cervical disc arthroplasty using a new arthroplasty device at 24-months follow-up. Summary of Background Data. Cervical disc arthroplasty preserves motion in the cervical spine. It is an alternative to fusion after neurologic decompression, whereas anterior decompression and fusion provides a rigorous comparative benchmark of success. Methods. We conducted a randomized controlled multicenter clinical trial enrolling patients with cervical disc disease. Ultimately 242 received the investigational device (Bryan Cervical Disc), and 221 patients underwent a single-level anterior cervical discectomy and decompression and fusion as a control group. Patients completed clinical and radiographic follow-up examinations at regular intervals for 2 years after surgery. Results. Analysis of 12- and 24-month postoperative data showed improvement in all clinical outcome measures for both groups; however, 24 months after surgery, the investigational group patients treated with the artificial disc had a statistically greater improvement in the primary outcome variables: Neck disability index score (P = 0.025) and overall success (P = 0.010). With regard to implant- or implant/surgical-procedure-associated serious adverse events, the investigational group had a rate of 1.7% and the control group, 3.2%. There was no statistical difference between the 2 groups with regard to the rate of secondary surgical procedures performed subsequentto the index procedure. Patients who received the artificial cervical disc returned to work nearly 2 weeks earlier than the fusion patients (P = 0.015). Conclusion. Two-year follow-up results indicate that cervical disc arthroplasty is a viable alternative to anterior cervical discectomy and fusion in patients with persistently symptomatic, single-level cervical disc disease.

Stereotactic navigation for placement of pedicle screws in the thoracic spine

OBJECTIVEPedicle screw fixation in the lumbar spine has become the standard of care for various causes of spinal instability. However, because of the smaller size and more complex morphology of the thoracic pedicle, screw placement in the thoracic spine can be extremely challenging. In several published series, cortical violations have been reported in up to 50% of screws placed with standard fluoroscopic techniques. The goal of this study is to evaluate the accuracy of thoracic pedicle screw placement by use of image-guided techniques. METHODSDuring the past 4 years, 266 image-guided thoracic pedicle screws were placed in 65 patients at the University of Michigan Medical Center. Postoperative thin-cut computed tomographic scans were obtained in 52 of these patients who were available to enroll in the study. An impartial neuroradiologist evaluated 224 screws by use of a standardized grading scheme. All levels of the thoracic spine were included in the study. RESULTSChart review revealed no incidence of neurological, cardiovascular, or pulmonary injury. Of the 224 screws reviewed, there were 19 cortical violations (8.5%). Eleven (4.9%) were Grade II (≤2 mm), and eight (3.6%) were Grade III (>2 mm) violations. Only five screws (2.2%), however, were thought to exhibit unintentional, structurally significant violations. Statistical analysis revealed a significantly higher rate of cortical perforation in the midthoracic spine (T4–T8, 16.7%; T1–T4, 8.8%; and T9–T12, 5.6%). CONCLUSIONThe low rate of cortical perforations (8.5%) and structurally significant violations (2.2%) in this retrospective series compares favorably with previously published results that used anatomic landmarks and intraoperative fluoroscopy. This study provides further evidence that stereotactic placement of pedicle screws can be performed safely and effectively at all levels of the thoracic spine.

Traumatic atlantooccipital dislocation with survival.

Survival after traumatic atlantooccipital dislocation is rare. Only long-term survivors have been reported in the literature; however, improved prehospital care is likely responsible for the increase in the number of these patients seen at neurotrauma centers over the last decade. Associated severe and persistent neurological deficits are common in the few survivors. We report the case of a 10-year-old boy with traumatic atlantooccipital dislocation and a severe neurological injury. Low-field magnetic resonance imaging provided the additional diagnosis of an associated cervicomedullary epidural hematoma. The patient underwent emergency operative evacuation of the hematoma and an occipital-cervical fusion with internal fixation. He had a remarkable recovery in neurological function and achieved stable bony fusion 3 months postoperatively. With early recognition of this entity, improved neuroradiological imaging techniques, and aggressive treatment, patients may survive with significant neurological recovery.

Spinal cord astrocytomas : results of therapy

Spinal cord astrocytomas are rare lesions, usually of low grade, with a long natural history. Because of this, it is difficult to define the optimum approach to therapy based on available data. To provide more data, a retrospective review was performed. From 1975 through 1989, 21 patients were seen and treated (median age, 21 years), and 15 patients received radiation therapy after undergoing either biopsy or resection. The median time until death or the last follow-up examination was 41 months. The actuarial survival of all patients was 68% at 5 years. Of the five deaths, four were related to local tumor recurrence. The overall survival and recurrence-free survival of irradiated patients at 5 years was 57% and 44%, respectively. The age of the patient was a prognostic factor, with younger patients surviving substantially longer before recurrence. Of the 15 irradiated patients, 7 experienced recurrence of the tumor, which occurred within the irradiated portion of the spinal cord in all 7. Gross total resections were rarely achieved and, also, the extent of resection did not influence the risk for recurrence. In summary, we observed a long natural history for this disease, and although additional local therapy appears needed, it is unclear that either higher doses of radiation or more extensive surgery will decrease the risk of recurrence.

Intraoperative Iso-C C-Arm Navigation in Craniospinal Surgery: The First 60 Cases

OBJECTIVE:The intraoperative Iso-C C-arm (Siremobil Iso-C 3D; Siemens Medical Solutions, Erlangen, Germany) provides a unique ability to acquire and view multi-planar three-dimensional images of intraoperative anatomy. Registration for intraoperative surgical navigation may be automated, thus simplifying the operative workflow. METHODS:Iso-C C-arm intraoperative fluoroscopy acquires 100 images, each of which must be 1.8 degrees in a circumferential fashion about an “isocentric” point in space. The system generates a high-resolution isotropic three-dimensional data set that is available immediately after the 90-second C-arm rotation. The data set is ported to the image-guided workstation, registration is immediate and automated, and the surgeon can navigate with millimetric accuracy. The authors prospectively examined data from the initial 60 patients examined with the Iso-C, among whom were cases of anterior and posterior spinal instrumentation from the occiput to the sacrum. Percutaneous and minimally invasive spinal and cranial procedures were also included. RESULTS:Automated registration for image-guided navigation was attainable for anterior and posterior cases from the cranial base and entire spine. In most cases, intraoperative postprocedural imaging with the Iso-C mitigated the need for postoperative imaging. CONCLUSION:Intraoperative Iso-C three-dimensional scanning allows real-time feedback during cranial base and spinal surgery and during procedures involving instrumentation. In most cases, it obviates the need for postoperative computed tomography. Its usefulness is in its simplicity, and it can be easily adapted to the operating room workflow. When coupled with intraoperative navigation, this new technology facilitates complex neurosurgical procedures by improving the accuracy, safety, and time of surgery.

Traumatic Occipitoatlantal Dislocations

Fourteen occipitoatlantal dislocations were treated during an 11-year period. All patients presented with neurological deficits and definite evidence of spinal instability. Plain radiographs provided the diagnosis conclusively in 11 patients. Three patients required computed tomography (CT) or magnetic resonance (MR) imaging for diagnosis. Rotational subluxations were radiographically occult and associated with less severe neurological injuries compared to distracted or translated subluxations. Ten patients died acutely. One patient, who had complete C1 level quadriplegia, died after 3 months. Three patients with incomplete spinal cord syndromes had long-term survival and functional neurological recoveries. Extensive ligamentous injury predisposed patients to recurrent subluxations. In several patients, traction or a cervical collar caused distraction and neurological injury. Halo immobilization and urgent fusion are necessary for patients with salvageable neurological function. Nonoperative measures are inadequate for immediate or long-term spinal stability.

Threaded Steinmann pin fusion of the craniovertebral junction

Study Design In a clinical retrospective study, the authors review long‐term results of occipitocervical fusion using a wide diameter, contoured, threaded Steinmann pin. Objectives To evaluate the clinical and radiographic results of occipitocervical fusion using this technique in a variety of abnormalities including rheumatoid arthritis. Summary of Background Data The various surgical techniques and hardware developed for occipitocervical fusion have been associated with mixed results, particularly in patients with rheumatoid arthritis or basilar invagination. Methods Thirty‐nine patients with occipitocervical instability were internally fixed with a wide diameter, contoured, threaded Steinmann pin wired to the occiput and cervical laminae or facets. Fusion was facilitated using autologous iliac crest bone graft and a cervical orthosis. Instability resulted from rheumatoid arthritis (n = 12), congenital anomalies (n = 12), trauma (n = 10), tumor (n = 4), or osteogenesis imperfecta (n = 1). Fifteen patients had radiographic evidence of basilar invagination. Long‐term outcome (mean follow‐up period, 38.9 months; range, 12‐78 months) was based on clinical and radiographic review. Results Thirty‐seven patients (97%) had a stable postoperative occipitocervical construct: there were 35 osseous unions, two fibrous unions, and one nonunion. There was one postoperative death from pulmonary complications. No patient developed evidence of new, recurrent, or progressive basilar invagination. Conclusion The authors concluded that rigid segmental fixation of the craniovertebral junction using a wide diameter, contoured, threaded Steinmann pin and supplemental autograft creates excellent fusion with minimal complications. This technique is appropriate for a variety of abnormalities including rheumatoid arthritis.

Emergency magnetic resonance imaging of cervical spinal cord injuries: Clinical correlation and prognosis

OBJECTIVE: The goal of this study was to determine the prognostic and clinical value of magnetic resonance imaging (MRI) performed within hours after cervical spinal cord injuries in human patients. METHODS: Fifty-five patients with acute cervical vertebral column and spinal cord injuries underwent MRI as part of their initial treatment at the University of Michigan Medical Center. All images were obtained within 21 hours after injury (mean, 7.8 h) and were interpreted by an attending neuroradiologist who was blinded to the clinical status of the patients. Neurological function at presentation and in long-term follow-up examinations was compared with MRI characteristics assessed immediately after the injury. RESULTS: The presence and rostrocaudal length of intra-axial hematoma, the rostrocaudal length of spinal cord edema, the presence of spinal cord compression, and spinal cord compression by extra-axial hematoma were each significantly associated with poor neurological function at presentation and in long-term follow-up examinations. Although the best single predictor of long-term improvement in neurological function was the neurological function at presentation, four MRI characteristics, i.e., the presence of intra-axial hematoma, the extent of spinal cord hematoma, the extent of spinal cord edema, and spinal cord compression by extra-axial hematoma, provided significant additional prognostic information. MRI data demonstrated spinal cord compression for 27 of 55 patients (49%), leading to emergency surgery. Among patients who underwent imaging after restoration of normal vertebral alignment using closed cervical traction, 13 of 26 (50%) underwent emergency surgery for treatment of persistent, MRI-demonstrated, spinal cord compression. CONCLUSION: Emergency MRI after spinal cord injury provides accurate prognostic information regarding neurological function and aids in the diagnosis and treatment of persistent spinal cord compression after vertebral realignment.

Intraoperative Iso-C C-arm Navigation in Cervical Spinal Surgery : Review of the First 52 Cases

Study Design. Fifty-two study participants underwent cervical spine surgery using intraoperative Iso-C imaging with or without spinal navigation. Objectives. To evaluate prospectively the feasibility, advantages, limitations, and applications of Iso-C in cervical spine surgery. Summary of Background Data. Existing stereotactic spinal navigational systems images must be acquired before surgery and typically require cumbersome point-to-point registration. Intraoperative computed tomography (CT) and magnetic resonance imaging (MRI) provide real-time information but can restrict access to the patient, preclude the use of traditional operating room tables, and are time-consuming. The Iso-C allows quick, CT-quality, real-time data acquisition without restricting access to the patient. The data acquired can be automatically transferred to navigational systems with the immediate ability to navigate for anterior or posterior cervical spine procedures. Methods. High-resolution isotropic three-dimensional data sets were acquired using the Iso-C intraoperative fluoroscopy in 52 cervical spine cases. In 30 cases, the data were imported automatically to the StealthStation Treon to support neuronavigation. In 22 cases, a postprocedural intraoperative CT was obtained with the Iso-C primarily to assess the extent of osseous decompression and/or the accuracy of implants or instrumentation. In most cases, a postoperative high-resolution CT image was obtained and compared with the Iso-C data. Results. Successful automated registration suitable for navigation was attained for all anterior and posterior cervical spinal cases. The postprocedural intraoperative Iso-C data were 100% concordant with those of postoperative high-resolution CT as determined by a blinded neuroradiologist. Conclusions. Iso-C intraoperative fluoroscopy is an accurate and rapid way to perform CT-quality image-guided navigation in cervical spinal surgery. In most cases, it obviates the need for postoperative imaging.

Characterization of contractile responses to endothelin in human cerebral arteries: implications for cerebral vasospasm.

Cerebral vascular tone is modulated, at least in part, by the vascular endothelium. This probably results from a balance between the release of the endothelium-derived relaxing factor(s) and the endothelium-derived constricting factor(s) (e.g., endothelin). The time course of the induction and the decay of these mutually antagonizing substances differ considerably. Endothelium-derived relaxing factor is probably involved in rapid changes in vascular tone whereas endothelin may be more important in long-term modulation. We have studied the vasoconstrictor properties of endothelin in human cerebral artery strips. Endothelin typically produced an intense, sustained increae in tone over a dose range similar to that seen with other vasoconstrictor substances such as serotonin and prostaglandin F2 alpha (ED50 = 10(-8) M). The response was resistant to selective antagonists of norephinephrine, serotonin, isoproterenol, histamine, acetycholine, and angiotensin II. Only sodium nitroprusside, verapamil, and a disulfide bond reducing agent (dithiothreitol) inhibited the response. The physiological properties of this response are similar to those of a vasoconstrictor protein found in cerebrospinal fluid from patients with cerebral vasospasm after subarachnoid hemorrhage. The time course of the induction of endothelin production is consistent with the temporal sequence of vasospasm, further supporting the hypothesis that endothelin may be involved in this pathological process.