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Corinna C. Zygourakis, Kevin S. Cahill and Mark R. Proctor

A previously healthy 2-year-old girl sustained a C1–2 ligamentous injury after a motor vehicle accident and underwent successful halo immobilization, with postimmobilization images showing good cervical alignment. At the time, plain radiography, CT scanning, and MR imaging showed a normal odontoid. Four years later, however, the patient was found to have an os odontoideum, evident on plain radiography and CT imaging. At the 10-year follow-up, the os odontoideum had not been surgically repaired, and the child had mild hypermobility.

This is the first documented case in the modern imaging era of delayed os odontoideum formation after definitive CT scanning showed no fracture. As such, this suggests that os odontoideum may result from traumatic vascular interruption in the developing spine, with resulting osseous remodeling leading to an os odontoideum. This case argues against the congenital etiology of os odontoideum, as well as the strict posttraumatic theory whereby a trauma-induced odontoid fracture leads to osseous remodeling and subsequent development of an os odontoideum.

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Kevin S. Cahill, Paul C. McCormick and Allan D. Levi

The risk of postoperative cancer following the use of recombinant human bone morphogenetic protein (BMP)–2 in spinal fusion is one potential complication that has received significant interest. Until recently, there has been little clinical evidence to support the assertion of potential cancer induction after BMP use in spinal surgery. This report aims to summarize the findings from clinical data available to date from the Yale University Open Data Access (YODA) project as well as more recently published large database studies regarding the association of BMP use in spinal fusion and the risk of postoperative cancer. A detailed review was based on online databases, primary studies, FDA reports, and bibliographies of key articles for studies that assessed the efficacy and safety of BMP in spinal fusion. In an analysis of the YODA project, one meta-analysis detected a statistically significant increase in cancer occurrence at 24 months but not at 48 months, and the other meta-analysis did not detect a significant increase in postoperative cancer occurrence. Analysis of 3 large health care data sets (Medicare, MarketScan, and PearlDiver) revealed that none were able to detect a significant increase in risk of malignant cancers when BMP was used compared with controls. The potential risk of postoperative cancer formation following the use of BMP in spinal fusion must be interpreted on an individual basis for each patient by the surgeon. There is no conclusive evidence that application of the common formulations of BMP during spinal surgery results in the formation of cancer locally or at a distant site.

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Kevin S. Cahill and Elizabeth B. Claus

Object

The authors conducted a study to determine population-based estimates of survival following the diagnosis and treatment of nonmalignant intracranial meningioma in the US in the modern era.

Methods

Patients with nonmalignant intracranial meningioma were identified through the Surveillance, Epidemiology, and End Results (SEER) database for the years 2004–2007. Predictors of undergoing resection were identified and odds ratios calculated. Estimates of survival were calculated using Kaplan-Meier estimation method and Cox proportional hazards model.

Results

There were 12,284 patients with a diagnosis of nonmalignant intracranial meningioma included in the analysis. Only 55% had histological confirmation of the diagnosis of nonmalignant meningioma. Resection was used as an initial treatment in 43% of cases. Patients treated with surgery were more likely to be younger (OR 9.3, 95% CI 8.1–10.7, for resection in patients age 40–59 years compared with age > 80 years), male (OR 1.4, 95% CI 1.3–1.5, for males compared with females), white (OR 0.8, 95% CI 0.7–0.9, for black patients compared with white patients), and have larger tumors (OR 11.8, 95% CI 10.3–13.6, for tumors of the largest quartile compared with the smallest quartile). Patients treated with resection had a 3-year postdiagnosis survival estimate of 93.4% (95% CI 92.5%–94.3%) compared with 88.3% (95% CI 85.5%–90.6%) in patients not treated with resection (p < 0.01). Younger patient age, female sex, unilateral tumors, and resection were predictors of improved postdiagnosis survival after multivariate adjustment in patients with histologically confirmed meningiomas.

Conclusions

This analysis represents the first modern population-based analysis of treatment patterns and outcomes in US patients with nonmalignant intracranial meningioma. Over 85% of patients survive 3 years after diagnosis, and resection is associated with improved survival.

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Kevin S. Cahill, Joseph L. Martinez, Michael Y. Wang, Steven Vanni and Allan D. Levi

Object

The aim of this study was to determine the incidence of motor nerve injuries during the minimally invasive lateral interbody fusion procedure at a single academic medical center.

Methods

A retrospective chart review of 118 patients who had undergone lateral interbody fusion was performed. Both inpatient and outpatient records were examined to identify any new postoperative motor weakness in the lower extremities and abdominal wall musculature that was attributable to the operative procedure.

Results

In the period from 2007 to 2011 the lateral interbody fusion procedure was attempted on 201 lumbar intervertebral disc levels. No femoral nerve injuries occurred at any disc level other than the L4–5 disc space. Among procedures involving the L4–5 level there were 2 femoral nerve injuries, corresponding to a 4.8% injury risk at this level as compared with a 0% injury risk at other lumbar spine levels. Five patients (4.2%) had postoperative abdominal flank bulge attributable to injury to the abdominal wall motor innervation.

Conclusions

The overall incidence of femoral nerve injury after the lateral transpsoas approach was 1.7%; however, the level-specific incidence was 4.8% for procedures performed at the L4–5 disc space. Approximately 4% of patients had postoperative abdominal flank bulge. Surgeons will be able to minimize these motor nerve injuries through judicious use of the procedure at the L4–5 level and careful attention to the T-11 and T-12 motor nerves during exposure and closure of the abdominal wall.

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Mark B. Frenkel, Kevin S. Cahill, Ramin J. Javahary, George Zacur, Barth A. Green and Allan D. Levi

Object

The goal of this study was to compare the rates of solid arthrodesis and complications following multilevel, instrumented anterior cervical fusion in patients treated with and without bone morphogenetic protein (BMP).

Methods

The authors conducted a retrospective cohort study of patients who underwent multilevel (2+ level) anterior cervical fusions performed for degenerative disc disease with or without the concurrent use of BMP-2 from 1997 to 2012. The dosage throughout the study ranged from 2.1 to 0.26 mg/level (mean 1.0 mg/level). All patients were evaluated postoperatively by means of radiographs and CT scans to determine fusion status.

Results

The overall fusion rate for the patients treated without BMP (n = 23) was 82.6% compared with a 100% fusion rate in the group treated with BMP (n = 22) (p = 0.04). The pseudarthrosis rates increased with number of fusion levels in patients who did not receive BMP, whereas all patients in the group treated with BMP had solid arthrodesis. Furthermore, there were 2 instrumentation failures in the non-BMP group. There was a direct correlation between the incidence of complications and the dosage of BMP used per level, with no complications reported at doses equal to or less than 1.1 mg/level.

Conclusions

The overall rate of bony arthrodesis was increased following the use of BMP in multilevel anterior cervical fusion. Traditional methods without BMP had a high rate of pseudarthrosis. The complications associated with the use of BMP appeared to be dose related and of low incidence when BMP is used in doses equal to or less than 1.1 mg/level.

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Kevin S. Cahill, Ian Dunn, Thorsteinn Gunnarsson and Mark R. Proctor

Object

Lumbar disc herniation is a rare but significant cause of pain and disability in the pediatric population. Lumbar microdiscectomy, although routinely performed in adults, has not been described in the pediatric population. The objective of this study was to determine the surgical results of lumbar microdiscectomy in the pediatric population by analyzing the experiences at Children's Hospital Boston over the past decade.

Methods

A series of 87 consecutive cases of lumbar microdiscectomy performed by the senior author (M.R.P.) from 1999 to 2008 were reviewed. Presenting symptoms, physical examination findings, and preoperative MR imaging findings were obtained from medical records. Immediate operative results were assessed including operative duration, blood loss, length of stay, and complications, along with long-term outcome and need for repeat surgery.

Results

This series represents the first surgical series of pediatric microdiscectomies. The mean patient age was 16.6 years (range 12–18 years) and 60% were female. The preoperative physical examination results were notable for motor deficits in 26% of patients, sensory changes in 41%, loss of deep tendon reflex in 22%, and a positive straight leg raise in 95%. Conservative management was the first line of treatment in all patients and the mean duration of symptoms until surgical treatment was 12.2 months. The mean operative time was 110 minutes and the mean postoperative length of stay was 1.3 days. Complications were rare: postoperative infection occurred in 1%, postoperative CSF leak in 1%, and new postoperative neurological deficits in 1%. Only 6% of patients needed repeat lumbar surgery and 1 patient ultimately required lumbar fusion.

Conclusions

The treatment of pediatric lumbar disc herniation with microdiscectomy is a safe procedure with low operative complications. Nuances of the presentation, treatment options, and surgery in the pediatric population are discussed.

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Joseph R. O'Brien and William D. Smith

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John H. Sampson, James E. Herndon II, Allan H. Friedman and Amy P. Abernethy