Responsiveness and minimal clinically important difference of the Brief BESTest 12 months after surgery for lumbar spinal stenosis: a prospective cohort study in Japan.

Abstract

Prospective cohort study. To assess the responsiveness of the Brief Balance Evaluation Systems Test (Brief BESTest) after lumbar spinal stenosis (LSS) surgery and to determine its minimal clinically important difference (MCID). LSS leads to balance impairment and increased fall risk, even after surgical decompression. Although postoperative balance improves, the specific subsystems that recover and the clinically meaningful magnitude of the change remain unclear. This prospective study included 197 patients aged ≥60 years who underwent decompression or fusion surgery for LSS. Balance was assessed preoperatively and 12 months postoperatively using the Brief BESTest. Responsiveness was quantified using the standardized response mean (SRM). The MCID was determined using receiver operating characteristic (ROC) analysis with the Global Rating of Change as an anchor. Bootstrap resampling was used to evaluate MCID stability. Patients were classified into moderate or severe groups based on preoperative Brief BESTest scores, using 13 points as the previously identified cutoff for increased fall risk in older adults. The Brief BESTest scores improved significantly in all patients (11.6±5.5 to 14.1±6.2; SRM=0.51). The severe group showed greater responsiveness (SRM=0.64) than the moderate group (SRM=0.38). In the subsystem, the largest improvements were observed in anticipatory postural adjustments and gait stability, whereas stability limits showed little change. ROC analysis identified an MCID of 2 points (area under the curve=0.79), which was consistent across the severity subgroups. Bootstrap validation confirmed the stability of this 2-point MCID. The Brief BESTest showed moderate responsiveness to balance improvements after LSS surgery, with marked gains in anticipatory adjustments and gait stability. The MCID of the Brief BESTest after LSS surgery is 2 points, providing a practical benchmark for postoperative evaluation regardless of preoperative severity.