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Objectives and questions: Total hip arthroplasty (THA) significantly impacts lower extremity kinematics, influencing gait and functional outcomes. Accurate measurement of these changes is critical for postoperative assessment and rehabilitation. Traditional 3D motion capture systems, while accurate, are often impractical in clinical settings. The Orthelligent^® Vision, a portable motion analysis tool, offers a potential alternative, but its validity and reliability for evaluating post-THA kinematics remain unverified.

Material and methods: This cross-sectional study included 30 patients who underwent THA (Group T) and 20 healthy controls (Group H). Hip range of motion (ROM)—including flexion, abduction, and rotation—was assessed during standardized gait and functional tasks using synchronized kinematic recordings from the Orthelligent^® Vision system and a validated three-dimensional motion capture system. Validity was assessed using Pearson’s correlation coefficients (r) and Bland-Altman analysis, while intraclass correlation coefficients (ICCs) were used to evaluate test-retest and inter-rater reliability. Group T underwent assessments preoperatively, as well as at 6 and 12 weeks postoperatively, whereas Group H was evaluated at a single time point. Differences in ROM and angular kinematics between groups were analyzed using appropriate parametric and non-parametric statistical methods.

Results: The Orthelligent^® Vision system demonstrated strong validity against the gold-standard system, with robust correlations for hip flexion (r = 0.92), abduction (r = 0.89), and rotation (r = 0.86), minimal bias (±1.5°–1.8°), and excellent reliability (test-retest ICCs: 0.91–0.94; inter-rater ICCs: 0.89–0.92). Kinematic variability in hip range of motion was observed in Group T across different time points, with significant improvements from preoperative assessment to 6 and 12 weeks postoperatively (38.2° ± 4.1° vs. 40.7° ± 4.2° vs. 44.3° ± 3.9°, p < 0.01). Compared to healthy controls, Group T exhibited significant kinematic deficits, including reduced sagittal-plane hip range of motion (38.2° ± 4.1° vs. 43.7° ± 3.8°, p < 0.001) and increased frontal-plane asymmetry (p = 0.028). High measurement precision (SEM = 1.2°, 95% CI: 0.9°–1.5°) further supports the system’s clinical utility for detecting postoperative kinematic deviations, facilitating objective rehabilitation monitoring and early intervention.

Discussion and conclusions: The Orthelligent^® Vision is a valid and reliable tool for assessing lower extremity kinematics in THA patients. Its portability and precision support its utility in clinical and research settings, enabling efficient postoperative monitoring and personalized rehabilitation strategies.