Telemeterized in vivo hip joint force data: A report on two patients after total hip surgery

Abstract

Two telemeterized femoral components were implanted in two patients as part of normal total hip replacement procedures. The two components were instrumented to measure the three force components directed along: (a) the neck axis, (b) transverse to the neck axis and in the plane of the prosthesis, and (c) transverse to the neck axis and perpendicular to the plane of the prosthesis. Data were collected at multiple sessions during the early postoperative period for a number of standard activities, including gait, stair climbing, rising from a chair, single leg stance, double leg stance, ipsilateral and contralateral straight leg lifts while supine, ipsilateral flexion and extension while standing, and ipsilateral abduction while standing and lying on the contralateral side. These data are summarized and compared with the published results from analytic studies and with the results from previous studies using instrumented femoral components. Peak loads for gait during the period of study were roughly 2.7 body weights (BW) when the patients walked at their normal pace. Contact forces at the hip during stationary single leg stance approximated the peak loads during gait with values ranging from 2.1 to 2.8 BW. The highest forces recorded reached values approaching 5.5 BW and occurred during periods of instability while the patient engaged in stationary single leg stance. Our in vivo data indicate that forces generated during the above activities increase in magnitude quite rapidly during the early postoperative period and that during this period the patients have the ability to perform the activities of daily living without generating the high amplitude joint contact forces suggested by the results of dynamic studies. Joint contact forces during gait were found to depend on speed, but the high absolute magnitudes predicted by model studies were not supported by the in vivo data.

Effects of episodic subluxation events on third body ingress and embedment in the THA bearing surface

“…Total hip arthroplasty preparation in multi-axis joint simulator actuated by an MTS 858 Bionix materials testing machine, and including third body particle circulation. Hip joint level walking cycle from Kotzar et al (1991), as adapted to the multi-axis joint simulator. THA subluxation event for studying third body particle ingress.…”

“…The level walking waveforms determined by Kotzar et al (1991) were converted to axial loads and rotational degrees-of-freedom for the MTS joint simulator (Figure 3). Body weight was assumed to be 620 N. Cycle frequency was 1 Hz.…”

Stability Differentials for Proximal vs Distal Fusion of Total Hip Arthroplasty Femoral Impaction Grafts

“…The constructs were loaded with 250,000 three-dimensional physiologic duty cycles for level walking and stair climbing [27], which were converted to axial and torsional loads for the MTS machine to apply [19]. Loading was at 50% full-scale.…”

Whole Bone Mechanics and Bone Quality

“…The forces generated during various daily activities have been measured at the hip and ranged from less than body weight to many multiples of body weight. The lowest forces occurred during nonweightbearing rehabilitation exercises and the highest forces while rising from a chair or climbing stairs [7,74]. For any given set of applied loads, the characteristics of the bone, joint, or other skeletal structure of interest determine whether the skeleton can carry these loads successfully or fracture will result.…”