Functional Outcomes Among Military Patients Following Spinal Arthrodesis

Introduction: Postoperative functional outcomes among patients who undergo spinal arthrodesis represent concerns for surgeons and patients alike. However, whether outcomes demonstrate overall associations with affected spinal regions and general surgical approaches appear little-studied. If present, functional outcome variation could suggest the need for further investigation to verify best practices. These are important considerations for military medicine due to the growing emphasis on physical readiness for soldiers. Our specific aims were to assess a large military population for associations between postoperative, medically-assigned functional levels and two possible predictors, the affected spinal region and anterior versus posterior approaches.

Methods: We leveraged official administrative and health record data assembled for medical readiness studies of US military members (2011-14). We identified 311 individuals who underwent spinal arthrodesis, affected regions and approaches, and medically-assigned activity restrictions at postoperative month six. We classified subjects as functionally impaired if restricted at level three or higher on the Army’s four-tier scale. These restrictions variously prohibited activities including strenuous lifting and rigorous training or deployment. Based on preliminary data, we restricted analyses to cervical or lumbar procedures with anterior or posterior approaches to ensure adequate statistical power. We applied multivariable logistic regression controlling for combinations of surgical approach, spinal region, sex, age, pay grade, and race.

Results: There were 274 (88.10%) male and 37 (11.90%) female patients. Mean age was 37.78 years (median: 38; standard deviation: 7.61; range: 20 to 59). There were 90 subjects (28.94%) with anterior procedures; 221 (71.06%) underwent posterior approaches. We identified 200 subjects with cervical procedures (64.31%) and 111 (35.69%) had lumbar procedures. No statistically significant unadjusted difference in functional impairment risk existed between anterior versus posterior procedures (P = 0.873) or by spinal region (P = 0.841). The lowest pay grade group demonstrated the sole statistically significant adjusted finding (3.85 times the adjusted odds of functional impairment; 95% confidence interval: 1.35 to 11.03) versus the highest pay grades.

Conclusion : Broad surgical procedure categories did not predict functional outcomes in spinal arthrodesis in this military population. Further study may be useful to identify outcome variation based on other factors such as pathophysiology and finer aspects of surgical approaches.