Clinical Improvement After Lumbar Fusion

Study Design.Retrospective review of a single institution cohort.Objective.The goal of this study is to identify features that predict delayed achievement of minimum clinically important difference (MCID) following elective lumbar spine fusion using Patient-Reported Outcomes Measurement Information System (PROMIS) surveys.Summary of Background Data.Preoperative prediction of delayed recovery following lumbar spine fusion surgery is challenging. While many studies have examined factors impacting the achievement of MCID for patient-reported outcomes in similar cohorts, few studies have assessed predictors of early functional improvement.Methods.We retrospectively reviewed patients undergoing elective one-level posterior lumbar fusion for degenerative pathology. Patients were subdivided into two groups based on achievement of MCID for each respective PROMIS domain either before six months ("early responders") or after six months ("late responders") following surgical intervention. Multivariable logistic regression analysis was used to determine features associated with odds of achieving distribution-based MCID before or after six months follow up.Results.147 patients were included. The average age was 64.3 +/- 13.0 years. At final follow-up, 57.1% of patients attained MCID for PI and 72.8% for PF. However, 42 patients (49.4%) reached MCID for PI by six months, compared to 44 patients (41.1%) for PF. Patients with severe symptoms had the highest probability of attaining MCID for PI (OR 10.3; P=0.001) and PF (OR 10.4; P=0.001) Preoperative PROMIS symptomology did not predict early achievement of MCID for PI or PF. Patients who received concomitant iliac crest autograft during their lumbar fusion had increased odds of achieving MCID for PI (OR 8.56; P=0.001) before six months.Conclusion.Our study demonstrated that the majority of patients achieved MCID following elective one-level lumbar spine fusion at long-term follow-up, although less than half achieved this clinical benchmark for each PROMIS metric by six months. We also found that preoperative impairment was not associated with when patients would achieve MCID. Further prospective investigations are warranted to characterize the trajectory of clinical improvement and identify the risk factors associated with poor outcomes more accurately.