Association of maximum back and leg pain severity with objective functional impairment as assessed by five-repetition...

The five-repetition sit-to-stand (5R-STS) test was designed to capture objective functional impairment (OFI), and provides a new adjunctive dimension in patient assessment. Its interpretability and confounders remain poorly understood. We quantify the association among maximum patient-reported back (MBP) or leg pain (MLP) and OFI as measured by the 5R-STS using data from two prospective studies. Patients performed the 5R-STS test and completed visual analogue scales (VAS) for back and leg pain severity. Maximum pain severity was defined as VAS scores of 9 or 10. The association of MBP and MLP with 5R-STS test times as well as with the presence of OFI (> 10.5 s) and severe OFI (> 22.0 s) as determined by the 5R-STS baseline severity stratification was quantified by use of crude and adjusted regression models. A total of 258 patients were included. MBP and MLP were reported by 27 (10.5%) and 76 (29.5%) patients, respectively. Rates of OFI differed among patients with (92.6%) and without (55.0%) MBP (p < 0.001), while presence of MLP did not influence OFI (61.8% vs. 57.7%, p = 0.632). Similarly, severe OFI was more common among patients with MBP (33.3% vs. 9.1%, p < 0.001), but not among patients with MLP (17.1% vs. 9.3%, p = 0.119). In the adjusted logistic analysis, the influence of MBP on OFI persisted (odds ratio [OR] 10.08, confidence interval [CI] 2.73-65.74, p = 0.003), while MLP demonstrated no association (OR 0.91, CI 0.49-1.72, p = 0.780). These associations were consistent with findings pertaining to raw 5R-STS test times and in discectomy patients alone. There is a strong association of maximum back pain severity on VAS with the degree of OFI determined by 5R-STS testing. Radiculopathy with maximally strong back pain, however, does not seem to relevantly influence 5R-STS performance.Trial registration ClinicalTrials.gov : NCT03321357 & NCT03303300.