A novel and objective tool for determining total and shear joint contact forces after primary total hip arthroplasty

Total hip arthroplasty, a common surgical procedure in orthopedics, is used in patients with severe hip osteoarthritis to relieve pain and to restore the function. The surgery has been shown to be effective, but patients may experience gait limitations after surgery. We used a novel and innovative tool, Computed MyoGraphy (CMG), to analyse the gait kinematics and forces acting within the musculoskeletal system after total hip arthroplasty. Data obtained at different time points before and after surgery were compared with those of healthy subjects.

The gait patterns of patients with primary hip osteoarthritis patients and healthy subjects were compared using the Xsens Awinda system in combination with the CMG system. Joint contact forces and shear joint contact forces were assessed preoperatively at the 5th postoperative day as well as after the rehabilitation examining two types of movements, "walking" and "squatting".

As revealed by CMG during both, normal walking and in particular during squatting, pre- and postoperative patients showed lower values for total and shear hip joint contact forces on both sides of the body when compared to healthy subjects. These initial differences in the total and shear joint contact forces at the hip vanished after the completion of the rehabilitation process.

Total hip arthroplasty patients are initially limited to squat and walk normally, as they exert lower total and shear hip joint contact forces, interestingly not only on the affected side but also on the contralateral side. Rehabilitation improves the force development to a degree similar to healthy patients. CMG provides clinical usability that objectifies gait analyses and provide useful additional functional information for clinical practice.

Prospective study of gait analysis after primary total hip arthroplasty measured by Computed MyoGraphy (CMG) using Myonardo, DRKS00028175. Registered February 16, 2022 - Prospectively registered. Trial registration number DRKS00028175.