As the population ages, the prevalence of degenerative spinal conditions is estimated to increase. With soaring healthcare costs, we must be vigilant in our accountability for proper resource allocation to ensure universal access. Significant recent increases in lumbar fusion rates have been observed in the US. Less is known regarding the Canadian experience. Our objective was to evaluate recent trends in lumbar fusion and determine how surgeon factors influence reoperation for spinal stenosis (SS) surgery.

Longitudinal follow-up study of lumbar surgical procedures for SS using administrative databases. Data was gathered on patient-hospital encounters from April 1, 1995 to December 31, 2001. We analyzed trends in spinal fusion. Index procedures (decompressions or fusions) and surgeon variables, such as specialty (orthopaedics, neurosurgery) and volume (above or below thirty cases/year), were selected as predictors of patient reoperation for SS. Adjustments were made for age, gender, and comorbidity. Reoperation rates were evaluated at six weeks, one and two years and until maximal follow-up.

6128 patients were identified (4200 decompressions and 1928 fusions). Proportionally more fusions were performed over the study period when compared to decompressions (1:2.6 in 1995 versus 1:1.5 in 2001). Orthopaedic specialty and higher surgical volume were associated with increased proportion of fusions (p< 0.0001). Reoperation rate was higher for decompressions at two years (OR 1.4) but not at long-term follow-up to ten years. Surgeon specialty had no impact on reoperation rates. Lower surgical volume demonstrated a higher reoperation rate after adjusting for specialty (Hazard Ratio 1.28).

Rates of lumbar spinal fusion have been increasing in Ontario, but at a lesser rate compared with the US. There is wide variation in surgical procedures between surgeon specialty and volume. Surgeon specialty had little impact on reoperation rates. Better long-term survival was observed in spinal surgeons with volumes over thirty cases per year after adjusting for surgeon specialty. Due to increasing rates of spinal fusion, the benefit of improved long-term survival in SS surgery with higher volume surgeons requires more detailed analysis before policy recommendations can be made.

Introduction: Flexion distraction injuries (FDI)of the thoracic and lumbar spine can be stabilized with a short construct spanning one motion-segment. This fracture is functionally defined by failure of the posterior and middle columns in tension and the anterior column in compression or tension. Treatment of a predominantly bony injury with minimal deformity (Chance type) is usually non-operative. Intra-abdominal pathology, and ligamentous spinal instability are relative indications for surgery. Deformity of greater than 17 degrees of kyphosis has a poor prognosis when treated conservatively, and represents true instability in vitro. Surgical treatment is mainly through a posterior approach with instrumentation. Which construct to use and the number of motion segments to include is controversial. Multi-level instrumentation techniques both in distraction and compression have been used as well as shorter constructs, particularly in the lumbar spine. We addressed the efficacy of single motion-segment fixation by evaluating the radiographic and functional results of this treatment technique.

Methods: All patients diagnosed with a FDI were prospectively identified over a 48 month period. Non-operatively treated fractures were excluded. Other spine fractures were excluded. Demographics, comorbidity, neurological status, operative details and complications were recorded. Radiographic reviewers were blinded to the functional outcome of the patient and the time of follow-up. The Oswestry Functional Assessment Questionnaire was administered by mail.

Results: Twenty-one eligible patients were identified. A significant (p< 0.0001) correction of deformity was achieved, from a mean preoperative kyphosis of 10.1 degrees to a mean postoperative lordosis of 0.9 degrees. No loss of correction occurred. The mean Oswestry score was 11.5, with 88% of patients having minimal disability. One patient died from unrelated morbidity.

Conclusions: Hoshikawa etal showed in vitro how compression forces alone can create FDI. Compression without flexion causes burst fractures. With moderate flexion there is FDI with anterior body compression. With increasing flexion FDI becomes entirely distractive. As the forces are concentrated at a single point, reconstruction only requires that this location be addressed. As all FDI are created by the same mechanism, regardless of structures injured only short segment fixation is required.

We have demonstrated in FDI, single level fixation is biomechanically sound. Multilevel instrumentation creates loss of adjacent level motion segments. This is not necessary. The absence of a control group precludes absolute conclusions. Nonetheless most patients reported minimal disability related to their back and had excellent radiological outcomes. This study demonstrates that posterior reduction and stabilization of a single motion-segment for FDI can adequately stabilize the spine and lead to excellent functional outcomes.

We prospectively studied the use of intercostal EMG monitoring as an indicator of the accuracy of the placement of pedicle screws in the thoracic spine.

We investigated 95 thoracic pedicles in 17 patients. Before insertion of the screw, the surgeon recorded his assessment of the integrity of the pedicle track. We then stimulated the track using a K-wire pedicle probe connected to a constant current stimulator. A compound muscle action potential (CMAP) was recorded from the appropriate intercostal or abdominal muscles. Postoperative CT was performed to establish the position of the screw. The stimulus intensity required to evoke a muscle response was correlated with the position of the screw on the CT scan.

There were eight unrecognised breaches of the pedicle. Using 7.0 mA as a threshold, the sensitivity of EMG was 0.50 in detecting a breached pedicle and the specificity was 0.83.

Thoracic pedicle screws were accurately placed in more than 90% of patients. EMG monitoring did not significantly improve the reliability of placement of the screw.