Does the Dual-Mobility Hip Prosthesis Produce Better Joint Kinematics During Extreme Hip Flexion Task?

BACKGROUND: Total hip arthroplasty (THA) using dual-mobility (DM) design permits larger hip range of motion. However, it is unclear how it benefits the patients during activities of daily living. The purpose was to compare kinematic variables of the operated limb between THA patients using either DM or single-bearing (SB) implants during a squat task.

METHODS: Twenty-four THA patients were randomly assigned to either a DM or SB implant and matched to 12 healthy controls (CTRLs). They underwent 3-dimensional squat motion analysis before and 9 months after surgery. Sagittal and frontal plane angles of the pelvis and the hip were analyzed using statistical parametric mapping. Paired analyses compared presurgery and postsurgery squat depth.

RESULTS: Peak sagittal pelvis angle of DM was closer to normal compared with that of SB. Both implant groups had similar hip angle patterns and magnitude but significantly lower than the CTRLs. SB reached a much large hip abduction compared with the other groups. Both surgical groups had significantly worst squat depth than the CTRLs.

CONCLUSION: Neither THA implant groups were able to return pelvis and hip kinematics to the level of CTRLs. The deficit of DM implants at the pelvis combined with the poorer functional scores should caution clinicians to use this implant design in active patients. SB design causes a larger hip abduction to reach their maximum squat depth. Post-THA rehabilitation should focus on improving joint range of motion and strength.