John H. Chi

Prevalence, complications, and hospital charges associated with use of bone-morphogenetic proteins in spinal fusion procedures.

CONTEXT No national data exist to examine use of bone-morphogenetic proteins (BMPs) in spinal fusion surgery. OBJECTIVE To determine the patterns of use and rates of complications and financial charges associated with BMP use in spinal fusion nationally. DESIGN, SETTING, AND PATIENTS Retrospective cohort study of 328,468 patients undergoing spinal fusion procedures from 2002-2006 identified from the Nationwide Inpatient Sample database, a 20% sample of US community hospitals. MAIN OUTCOME MEASURES The rates of use of BMP among patients undergoing spinal fusion procedures are examined along with complications, length of stay, and hospital charges associated with use of this fusion adjunct. RESULTS The nationwide usage of BMP has increased from 0.69% of all fusions in 2002 to 24.89% of all fusions in 2006. Use of BMP varied by patient sex, race, and primary payer with increased use seen in women (56.26% with BMP vs 53.35% without BMP; odds ratio [OR], 1.12; 95% confidence interval, [CI], 1.09-1.16) and Medicare patients (29.62% with BMP vs 27.16% without BMP; OR, 1.43; 95% CI, 1.31-1.56) and decreased use in nonwhite patients (8.69% with BMP vs 10.23% without BMP; OR, 0.80; 95% CI, 0.75-0.85). When comparing immediate postoperative, in-hospital rates of complications for the year 2006 among patients undergoing spinal fusion by BMP use status, no differences were seen for lumbar, thoracic, or posterior cervical procedures. On univariate analysis and after multivariable adjustment, the use of BMP in anterior cervical fusion procedures was associated with a higher rate of complication occurrence (7.09% with BMP vs 4.68% without BMP; adjusted OR, 1.43; 95% CI, 1.12-1.70) with the primary increases seen in wound-related complications (1.22% with BMP vs 0.65% without BMP; adjusted OR, 1.67; 95% CI, 1.10- 2.53) and dysphagia or hoarseness (4.35% with BMP vs 2.45% without BMP; adjusted OR, 1.63; 95% CI, 1.30-2.05). Bone-morphogenetic protein use was associated with greater inpatient hospital charges across all categories of fusion. Increases between 11% and 41% of total hospital charges were reported, with the greatest percentage increase seen for anterior cervical fusion. CONCLUSION Bone-morphogenetic protein was used in approximately 25% of all spinal fusions nationally in 2006, with use associated with more frequent complications for anterior cervical fusions and with greater hospital charges for all categories of fusions.

Biomechanical Comparison of Posterior Lumbar Interbody Fusion and Transforaminal Lumbar Interbody Fusion Performed at 1 and 2 Levels

Study Design. Biomechanical laboratory study of human cadaveric spines. Objective. To determine the difference in acute stability between posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) performed at 1 and 2 levels with and without posterior fixation. Summary of Background Data. Circumferential spinal fusion with both an interbody graft and posterior pedicle screw-rod construct has been advocated to decrease pseudarthrosis rates. Both PLIF and TLIF theoretically allow for 3-column fixation and fusion. Methods. Specimens underwent either PLIF or TLIF at L2–L3 (single-level) and L3–L4 (2-level), both with and without pedicle screw instrumentation. During TLIF, an interbody allograft was placed in the anterior or middle column. Nondestructive, nonconstraining pure moment loading was applied to each specimen. Results. There were no significant differences in the range of motion after either PLIF or TLIF at 1 level. The addition of pedicle screws tended more strongly to increase rigidity after 1-level PLIF compared to TLIF. Position of the TLIF graft did not affect stability. The addition of pedicle screws to a 2-level construct significantly reduced all motions tested. Conclusions. Based on our findings, posterior fixation with a pedicle screw-rod construct is suggested for 1-level PLIF and TLIF, and is necessary to achieve stability after interbody fusion across 2 levels using either technique.

Selecting treatment for patients with malignant epidural spinal cord compression-does age matter?: results from a randomized clinical trial.

Study Design. Randomized clinical trial. Objective. To determine if age affects outcomes from differing treatments in patients with spinal metastases. Summary of Background Data. Recently, class I data were published supporting surgery with radiation over radiation alone for patients with malignant epidural spinal cord compression (MESCC). However, the criteria to properly select candidates for surgery remains controversial and few independent variables which predict success after treatment have been identified. Methods. Data for this study was obtained in a randomized clinical trial comparing surgery versus radiation for MESCC. Hazard ratios were determined for the effect of age and the interaction between age and treatment. Age estimates at which prespecified relative risks could be expected were calculated with greater than 95% confidence to suggest possible age cut points for further stratification. Multivariate models and Kaplan-Meier curves were tested using stratified cohorts for both treatment groups in the randomized trial each divided into 2 age groups. Results. Secondary data analysis with age stratification demonstrated a strong interaction between age and treatment (hazard ratio = 1.61, P = 0.01), such that as age increases, the chances of surgery being equal to radiation alone increases. The best estimate for the age at which surgery is no longer superior to radiation alone was calculated to be between 60 and 70 years of age (95% CI), using sequential prespecified relative risk ratios. Multivariate modeling and Kaplan-Meier curves for stratified treatment groups showed that there was no difference in outcome between treatments for patients ≥65 years of age. Ambulation preservation was significantly prolonged in patients <65 years of age undergoing surgery compared to radiation alone (P = 0.002). Conclusion. Age is an important variable in predicting preservation of ambulation and survival for patiens being treated for spinal metastases. Our results provide compelling evidence for the first time that particular age cut points may help in selecting patients for surgical or nonsurgical intervention based on outcome.

Limitations of the C6/Wistar rat intracerebral glioma model: implications for evaluating immunotherapy.

OBJECTIVE Intracranial rat glioma models are a useful method for evaluating the efficacy and toxicity of novel therapies for malignant glioma. The C6/Wistar model has been used extensively as a reproducible in vivo model for studying primary brain tumors including anti-glioma immune responses. The objective of the present study is to provide in vivo evidence that the C6 rat glioma model is allogeneic within Wistar rats and is therefore inappropriate for evaluating immune responses. METHODS Growth patterns and immune responses of C6 cells implanted into the brain and flank of Wistar rats were analyzed and compared to an immunogenic syngeneic model (9L/Fischer). RESULTS Wistar rats with C6 tumors developed a potent humoral and cellular immune response to the tumor. Wistar rats given simultaneous flank and intracerebral tumors had a survival rate of 100% compared to an 11% survival rate in control animals receiving only intracranial C6 cells. CONCLUSION The C6 rat glioma induces a vigorous immune reaction that may mimic a specific anti-tumor response in Wistar rats. Efficacy of immunotherapy within this model must be cautiously interpreted.

Glioproliferative Lesion of the Spinal Cord as a Complication of “Stem-Cell Tourism”

A primitive neoplasm composed predominantly of nonhost cells was detected in the thoracic spinal cord and thecal sac of a 66-year-old man who had received experimental stem-cell treatment from commercial clinics.

Primary Vertebral Tumors: A Review of Epidemiologic, Histological, and Imaging Findings, Part I: Benign Tumors

Primary vertebral tumors, although less common than metastases to the spine, make up a heterogeneous group of neoplasms that can pose diagnostic and treatment challenges. They affect both the adult and the pediatric population and may be benign, locally aggressive, or malignant. An understanding of typical imaging findings will aid in accurate diagnosis and help neurosurgeons appreciate anatomic subtleties that may increase their effective resection. An understanding of the histological similarities and differences between these tumors is imperative for all members of the clinical team caring for these patients. In this first review of 2 parts, we discuss the epidemiological, histological, and imaging features of the most common benign primary vertebral tumors—aneurysmal bone cyst, chondroma and enchondroma, hemangioma, osteoid osteoma, and osteoblastoma—and lesions related to eosinophilic granuloma and fibrous dysplasia. In addition, we discuss the basic management paradigms for each of these diagnoses. In combination with part II of the review, which focuses on locally aggressive and malignant tumors, this article provides a comprehensive review of primary vertebral tumors.

Posterior interhemispheric approach: surgical technique, application to vascular lesions, and benefits of gravity retraction.

OBJECTIVE: To review an experience with the posterior interhemispheric approach applied to vascular lesions in the posterior midline, to examine the effects of patient position and gravity retraction of the occipital lobe, and to identify circumstances requiring increased exposure by sectioning the falx and tentorium. METHODS: During a 6.5-year period, 46 posterior interhemispheric approaches were performed to treat 28 arteriovenous malformations, 10 dural arteriovenous fistulae, seven cavernous malformations, and one posterior cerebral artery aneurysm. Twenty-three patients were positioned prone and 23 patient were positioned laterally. RESULTS: A standard posterior interhemispheric approach was used in 38 patients, and the occipital bitranstentorial/falcine approach was used in seven patients. A contralateral occipital transfalcine approach was used with one thalamic cavernous malformation. All lesions were resected completely and/or obliterated angiographically, with good neurological outcomes in 83% of patients and no operative mortality. Blood loss was lower, operative durations were shorter, postoperative cerebral edema was decreased, and visual outcomes were improved in patients positioned laterally. CONCLUSION: The posterior interhemispheric approach, without additional dural cuts, is appropriate for most vascular lesions in the posterior midline. Gravity retracts the occipital lobes when patients are positioned laterally, enhancing operative exposure and reducing morbidity. Extension of the posterior interhemispheric approach to a transtentorial or transfalcine approach is required for falcotentorial dural arteriovenous fistulae and vein of Galen arteriovenous malformations, but is not usually necessary with cavernous malformations or other arteriovenous malformations.

Vertebroplasty and kyphoplasty for spinal metastases.

Purpose of reviewPathologic fractures of the spine are extremely painful and cause significant disability and morbidity in patients suffering from metastatic cancer. Often, these patients are not candidates for open surgical procedures and cannot address mechanical instability and radiation therapy can take weeks to become effective. Minimally invasive surgical techniques have been developed over the past several years, offering a simple and effective way of managing painful pathologic fractures. Recent findingsVertebroplasty and kyphoplasty offer patients a minimally invasive, percutaneuous procedure that dramatically reduces pain related to pathologic spinal fractures almost immediately with very low complication rates. Visual analog scale pain scores, narcotic usage and quality of life scales (SF-36) have all been shown to improve in a durable fashion for over 1 year. Also, these procedures can be performed before, after or concurrently with most radiation and chemotherapy protocols. SummaryWe recommend vertebroplasty or kyphoplasty in properly selected patients with painful pathologic fractures as early as possible. Newer biomaterials, which are softer than currently used cement, may offer better protection from adjacent level fracturing and lower complication rates.

Primary vertebral tumors: a review of epidemiologic, histological and imaging findings, part II: locally aggressive and malignant tumors.

This second part of a comprehensive review of primary vertebral tumors focuses on locally aggressive and malignant tumors. As discussed in the earlier part of the review, both benign and malignant types of these tumors affect the adult and the pediatric population, and an understanding of their subtleties may increase their effective resection. In this review, we discuss the epidemiologic, histological, and imaging features of the most common locally aggressive primary vertebral tumors (chordoma and giant-cell tumor) and malignant tumors (chondrosarcoma, Ewing sarcoma, multiple myeloma or plasmacytoma, and osteosarcoma). The figures used for illustration are from operative patients of the senior authors (Z.L.G. and J.H.C.). Taken together, parts 1 and 2 of this article provide a thorough and illustrative review of primary vertebral tumors.

Outcomes for single-level lumbar fusion: the role of bone morphogenetic protein.

Study Design. Retrospective analysis of a population-based insurance claims data set. Objective. To determine the risk of repeat fusion and total costs associated with bone morphogenetic protein (BMP) use in single-level lumbar fusion for degenerative spinal disease. Summary of Background Data. The use of BMP has been proposed to reduce overall costs of spinal fusion through prevention of repeat fusion procedures. Although radiographic fusion rates associated with BMP use have been examined in clinical trials, few data exist regarding outcomes associated with BMP use in the general population. Methods. Using the MarketScan claims data set, 15,862 patients that underwent single-level lumbar fusion from 2003 to 2007 for degenerative disease were identified. Propensity scores were used to match 2372 patients who underwent fusion with BMP to patients who underwent fusion without BMP. Logistic regression models, Kaplan-Meier estimates, and Cox proportional hazards models were used to examine risk of repeat fusion, length of stay, and 30-day readmission by BMP use. Cost comparisons were evaluated with linear regression models using logarithmic transformed data. Results. At 1 year from surgery, BMP was associated with a 1.1% absolute decrease in the risk of repeat fusion (2.3% with BMP vs. 3.4% without BMP, P = 0.03) and an odds ratio for repeat fusion of 0.66 (95% confidence interval [CI] = 0.47–0.94) after multivariate adjustment. BMP was also associated with a decreased hazard ratio for long-term repeat fusion (adjusted hazards ratio = 0.74, 95% CI = 0.58–0.93). Cost analysis indicated that BMP was associated with initial increased costs for the surgical procedure (13.9% adjusted increase, 95% CI = 9.9%–17.9%) as well as total 1-year costs (10.1% adjusted increase, 95% CI = 6.2%–14.0%). Conclusion. At 1 year, BMP use was associated with a decreased risk of repeat fusion but also increased health care costs.