Low-Grade Isthmic Spondylolisthesis Treated with Instrumented Posterior Lumbar Interbody Fusion in U.S. Servicemen

Purpose: The existing literature lacks a functional outcomes study addressing instrumented posterior lumbar fusion surgery for isthmic spondylolisthesis in physically active patients. Presently, spinal surgeons can provide only anecdotal advice when discussing operative outcomes with these patients. This is a nonrandomized analysis of consecutive military servicemen treated operatively for chronic back pain and low-grade isthmic spondylolisthesis with single-level lumbar disc degeneration with emphasis on functional outcomes. The purpose was to evaluate patient-assessed function/pain/satisfaction and military job performance in U.S. servicemen treated with posterior lumbar interbody fusion (PLIF). Methods: Thirty consecutive U.S. military servicemen with chronic low back pain and low-grade lumbar isthmic spondylolisthesis were referred to the same surgeon at a military treatment facility. All servicemen were treated operatively with instrumented PLIF using autogenous iliac crest bone graft, one or two nonthreaded interbody cages (Brantigan or Harms), and a four-pedicle screw/rod construct. A concomitant bilateral posterolateral fusion was performed in all 30 cases. The average follow-up time was 15 months (range 12-48 months). Twenty-five of the 30 servicemen completed a functional outcomes questionnaire (American Academy of Orthopaedic Surgeons/Scoliosis Research Society) with emphasis on pre- and posttreatment function, pain, and satisfaction. The servicemen were also evaluated using standard military job performance parameters. Results: Three of the 30 servicemen (10%) requested and received a disability discharge from the military for back pain that continued throughout the postoperative period and prevented return to military duty. An additional 8 of the original 30 soldiers (27%) required some form of permanent physical activity limitation (situps/pushups/running/lifting) to permit their return to military duty, and 19 of 30 (63%) soldiers were able to return to full and unrestricted military duty after surgery. Those soldiers who were able to return to unrestricted military duty (n = 19) did so at an average of 6 months post treatment (range 2-16 months). Of the soldiers who were able to return to military duty, 21 of 30 (70%) were able to complete the posttreatment military physical fitness test at an average of 8 months postoperatively (range 2-32 months). No significant differences were observed between premorbid and postsurgical physical fitness test scores. There was a trend toward lower postsurgical scores. Complications included dural tear (n = 4), unilateral transient lower extremity paresthesia (n = 1), and wound seroma requiring reoperation (n = 1). Conclusions: In this nonrandomized study of 30 U.S. servicemen with chronic low back pain, low-grade isthmic spondylolisthesis, and single-level lumbar disc degeneration, instrumented PLIF surgery was associated with a high rate of return to functional military duty. Outcomes with respect to posttreatment pain, function, and satisfaction were high in patients treated with instrumented PLIF.