Abstract

Although predicted hip joint center (HJC) locations are known to vary widely between functional methods, no previous investigation has detailed functional method dependent hip and knee biomechanics. The purpose of this study was to define a normative database of hip joint biomechanics during dynamic movements based upon functional HJC methods and calibration tasks. Thirty healthy young adults performed Arc, Star Arc, and Two Sided calibration tasks. Motion capture and ground reaction forces were collected during walking, running, and single-leg landings. Two sphere-fit (geometric & algebraic) and two coordinate transformation techniques were implemented using each calibration (12 total method-calibration combinations). Surprisingly, the geometric fit-Two Sided model placed the HJC at the midline of the pelvis and above the iliac spines, and thus was removed from analyses. A database of triplanar hip and knee kinematics and hip moments and powers was constructed using the mean of all subjects for the eleven method-calibration combinations. A nested ANOVA approach compared calibration[method] peak hip kinematics and kinetics. Most method differences existed between geometric fit and coordinate transformations (58 of 84 total). No Arc-Star Arc differences were found. Thirty-two differences were found between the Two Sided and Arc/Star Arc calibrations. This database of functional method based hip and knee biomechanics serves as an important reference point for inter-study comparisons. Overall, this study illustrates that functional HJC method can dramatically impact hip biomechanics and should be explicitly detailed in future work.

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