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Spinal Fusions in Active Military Personnel: Who Gets a Lumbar Spinal Fusion in the Military and What Impact Does It Have on Service Member Retention?

Introduction
Back pain related to spinal degenerative disease is one of the most common causes of missed duty days and medical separation for active service members. While the topic of operative versus non-operative treatment of degenerative spine conditions in active military personnel has received more and much needed attention in the last few years, there remains a paucity of data examining the expanded demographics and clinical findings of those undergoing spinal fusion in which validated outcome measures are used to assess post-operative results. The purpose of this study was to define the characteristics and outcomes of spinal fusion surgery at U.S. military medical treatment facilities.


Materials and Methods
A cohort of 145 active military personnel undergoing spinal fusion at a single military medical center between 2008 and 2013 were examined in a retrospective fashion using data from primary source documentation recorded prospectively in the military electronic medical records and the image data repository for demographics, clinical/imaging findings and patient reported outcome scores at mean follow-up of 6 mo. Oswestery Disability Index (ODI) scores and the Visual Analog Scale (VAS) were used as patient reported outcome measures. Soldier rank, active duty status, and service-connected disability percentage were also analyzed as military specific outcome measures.


Results
The typical solider undergoing spinal fusion was a Caucasian male serving in the U.S. Army. At last follow-up, there were statistically significant improvements in pre-operative to post-operative ODI and VAS scores. Younger age at the time of surgery was a negative predictor for post-operative VAS outcomes (p = 0.047). There were six reoperations in the cohort for neurologic symptoms and hardware migration. The majority of soldiers went on to medical retirement but a considerable number saw an increase in their rank prior to doing so. Those who ended their service in regular retirement and medical retirement went on to see 90.7% and 85% service-connected disability respectively.


Discussion
This investigation reports on the largest cohort of active military personnel undergoing spinal fusion. A variety of demographic information are reviewed to clarify the picture of soldiers at risk for needing a spinal fusion. While younger age was an independent risk factors for worsened VAS scores, no independent variable portended a worse ODI score at last follow-up. Despite improvements in objective measures such as VAS, ODI, and increases in rank, soldiers going on to retirement collected a dramatic service-connected disability percentage.


Level of Evidence
Level IV, Therapeutic.