In-vivo quantification of dynamic hip joint center errors and soft tissue artifact

Abstract

Hip joint center (HJC) measurement error can adversely affect predictions from biomechanical models. Soft tissue artifact (STA) may exacerbate HJC errors during dynamic motions. We quantified HJC error and the effect of STA in 11 young, asymptomatic adults during six activities. Subjects were imaged simultaneously with reflective skin markers (SM) and dual fluoroscopy (DF), an x-ray based technique with submillimeter accuracy that does not suffer from STA. Five HJCs were defined from locations of SM using three predictive (i.e., based on regression) and two functional methods; these calculations were repeated using the DF solutions. Hip joint center motion was analyzed during six degrees-of-freedom (default) and three degrees-of-freedom hip joint kinematics. The position of the DF-measured femoral head center (FHC), served as the reference to calculate HJC error. The effect of STA was quantified with mean absolute deviation. HJC errors were (mean±SD) 16.6±8.4 mm and 11.7±11.0 mm using SM and DF solutions, respectively. HJC errors from SM measurements were all significantly different from the FHC in at least one anatomical direction during multiple activities. The mean absolute deviation of SM-based HJCs was 2.8±0.7 mm, which was greater than that for the FHC (0.6±0.1 mm), suggesting that STA caused approximately 2.2 mm of spurious HJC motion. Constraining the hip joint to three degrees-of-freedom led to approximately 3.1 mm of spurious HJC motion. Our results indicate that STA-induced motion of the HJC contributes to the overall error, but inaccuracies inherent with predictive and functional methods appear to be a larger source of error.

In Vivo Pelvic and Hip Joint Kinematics in Patients With Cam Femoroacetabular Impingement Syndrome: A Dual Fluoroscopy Study

“…These control participants had no history of hip pain. Controls were screened with an anterior‐posterior (AP) radiograph prior to study inclusion . The AP radiograph provided general screening of hip pathology, including acetabular dysplasia, Legg–Calvé–Perthes disease, and acetabular retroversion.…”

“…For each activity, two trials were captured when possible, but activity level, allotted DF time, and image quality limited the ability to capture and analyze activities from some participants (Table ). For the walking trials at a self‐selected speed, the same treadmill speed was used for level and incline walking trials based on the preferred walking speed of the participant . For all walking trails, a single gait cycle was evaluated.…”

“…Controls were screened with an anterior-posterior (AP) radiograph prior to study inclusion. 19,[21][22][23] The AP radiograph provided general screening of hip pathology, including acetabular dysplasia, Legg-Calvé-Perthes disease, and acetabular retroversion. Alpha angle measurements were obtained from the AP radiograph as well as from oblique-axial reformatted magnetic resonance images (MRI) that were acquired for another study that utilized the same control population.…”

“…For the walking trials at a self-selected speed, the same treadmill speed was used for level and incline walking trials based on the preferred walking speed of the participant. 19,22 For all walking trails, a single gait cycle was evaluated. For rotational pivots and abduction, only the position of the maximum range of motion was evaluated herein.…”

Three‐dimensional femoral head coverage in the standing position represents that measured in vivo during gait

“…It is important to recognize that, although statistically significant, the differences may not be clinically-meaningful, as they were quite small (difference of 1.9-5.3%, calculated as 23-67 mm 2 ). We previously showed that hip translation during gait in these subjects was only 0.6 mm (Fiorentino et al, 2016a). Such small translations are unlikely to move the femoral head center enough to have a major impact on coverage, especially if the hip is spherical in shape.…”