Functional limitations due to stiffness as a collateral impact of instrumented arthrodesis of the lumbar spine.

Study Design: Prospective cohort study.
Objective: To understand whether patients actually perceive increased limitations as compared with their preoperative state due to stiffness after lumbar arthrodesis.
Summary of Background Data: Lumbar arthrodesis by intention eliminates spinal motion in an attempt to decrease pain, deformity, and instability. Independent of pain, loss of mobility can impact ability to perform certain activities of daily living. The lumbar stiffness disability index (LSDI) is a validated measure of the effect of lumbar stiffness on functional activities. To date, no prospective evaluations of stiffness impacts on patient function after lumbar arthrodesis have been reported.
Methods: The LSDI, 36-Item Short Form Health Survey, and Oswestry Disability Index were administered preoperatively and at 2-year minimum follow-up to 62 adult patients undergoing lumbar fusion for degenerative disease or spinal deformity. Patients also completed a satisfaction questionnaire at 2 years. Patients were separated according to the number of lumbar arthrodesis levels. Pre- and postoperative LSDI, 36-Item Short Form Health Survey physical composite score, and Oswestry Disability Index scores were compared using paired t tests.
Results: Significant improvements in Oswestry Disability Index were observed across all arthrodesis levels, and significant improvements in physical composite score were observed at level 1 and at 5 or more levels. Patients undergoing 1-level arthrodesis demonstrated statistically significant decreases in LSDI scores, indicating less impact from stiffness than at baseline. Patients with 3 or 4 levels and 5 or more levels of arthrodesis showed increases in LSDI scores, although none reached significance with the numbers available. Forty-six percent of patients reported that low back stiffness created significant limitations in activities of daily living, although 97% indicated that they would undergo the same procedure again and 91% reported that any increase in stiffness was an acceptable trade-off for their functional improvements from lumbar arthrodesis.
Conclusion: Patients undergoing elective lumbar arthrodesis reported relatively limited functional deficit due to stiffness at 2-year follow-up. Paradoxically, patients undergoing 1-level arthrodesis actually reported significantly less limitation due to stiffness postoperatively. Although the effects of stiffness did trend toward greater impacts among patients undergoing longer fusions, 91% of patients were satisfied with trade-offs of function and pain relief in exchange for perceived increases in lumbar stiffness.