Comparing Movement Patterns and Physical Function Between Chronic Low Back Pain Patients With Nociplastic and Nociceptive Pain Categories.
BACKGROUND: Individuals with chronic low back pain (LBP) often present with significant physical dysfunction. The underlying cause is difficult to diagnose due to the heterogeneous nature of LBP categories. METHODS: Two hundred and fifty-six patients were assessed as having either nociceptive (NC) or nociplastic (NP) chronic low back pain using validated surveys, including the PainDETECT Questionnaire and a chronic overlapping pain condition screener. Additional covariates of anxiety, depression, and fear avoidance were evaluated using standard surveys. Physical function was judged objectively using a sit-to-stand test (STS; quantified using marker-less motion capture calculated kinematic scores and movement metrics) and subjectively (PROMIS-physical function survey). Demographics (age, sex, BMI), psychological factors, and biomechanical outcomes were compared across pain categories using nonparametric statistics and regression modeling. RESULTS: Compared to the NC group, the NP group was significantly older (NP: 61.0 ± 21.0, NC: 53.5 ± 29.3, p = 0.03) and reported higher levels of anxiety (NP: 51.2 ± 17.4, NC: 48.0 ± 13.4, p = 0.002) and depression (NP: 49.0 ± 14.7, NC: 41.0 ± 10.8, p = 0.009). NP also had worse perceived physical function (PROMIS-PF) (NP: 39.3 ± 6.9, NC: 42.1 ± 7.3, p < 0.001) and slower STS times (NP: 12.5 ± 6.1 s, NC: 12.0 ± 5.8, p = 0.03). Despite these differences, the NP group exhibited biomechanical function closer to the healthy control average motion trajectory (K-score; NP: 77.6 ± 8.1, NC: 75.6 ± 8.1, p = 0.03) during the STS task. Regression models evaluating the association between biomechanical variables and pain categories, while adjusting for age, sex, and BMI, identified significant differences between pain categories only for PROMIS-physical function. CONCLUSION: While individuals with nociplastic pain reported lower perceived physical function and exhibited differences in demographic and psychological factors, pain categories were not significant predictors of objective biomechanical measures after adjusting for age, sex, and BMI. However, pain category was a significant predictor of PROMIS-PF, suggesting that it is more closely associated with perceived functional limitations than with quantitative biomechanical performance.
