Shoulder elevation and arm extension influence elbow joint loading during door-opening in total elbow arthroplasty: a musculoskeletal modelling study.

Total elbow arthroplasty (TEA) is used to treat end -stage elbow pathologies, yet implant failure is common due to excessive joint loading. This study compared elbow-joint loading, kinematics, and kinetics in TEA patients and healthy controls, and assessed the influence of elbow flexion-extension (FE) and shoulder elevation (SE). Seventeen participants (6 TEA, 11 controls) performed a door-opening task. Musculoskeletal modeling was used to estimate elbow kinematics, net joint moments FE and varus-valgus (VV)), and humeroulnar joint reaction forces (HUJRF). Statistical parametric mapping (SPM) analyzed time-series differences between groups, while cross-correlation assessed relationships between kinematics and loading. TEA patients showed reduced peak elbow extension (43.9 ± 14.9° vs. 5.8 ± 7.2° in controls, 0°=full extension, p < 0.001). Total HUJRF was highly correlated with SE (TEA r̄=0.83 ± 0.07; controls r̄=0.89 ± 0.06) and moderately correlated with FE angle (TEA r̄= 0.83 ± 0.03; controls r̄= 0.73 ± 0.07). VV moments showed moderate correlations with SE (TEA r̄= 0.59 ± 0.16; controls r̄= 0.66 ± 0.09) and FE angle (TEA r̄=0.66 ± 0.08; controls r̄=0.68 ± 0.05). These results suggest TEA patients adapt their movements to compensate for reduced motion while maintaining similar peak joint loads. Postoperative care should address movement patterns alongside load management. Further refinement of musculoskeletal models is needed to improve HUJRF estimation plus support rehabilitation and prosthetic design.