Optimal orientation of implanted components in total hip arthroplasty with polyethylene on metal articulation.
BACKGROUND
In many studies related to the total hip arthroplasty, it has been found that incorrect alignment of the total hip component is one of the major factors influencing mechanical failures. Although various recommendations for cup orientation have been presented, there were few studies that seek to determine a proper orientation of the implants based on the human motion data. The objective of this study is to determine an optimum orientation of the hip implant considering various daily activities.


METHODS
Firstly, the cup orientations free of impingement were calculated for a given set of implant geometric parameters and the required range of motion for daily activities measured in 10 subjects. Next, the optimum values for the cup orientation and stem anteversion avoiding impingement and minimizing cup wear were determined for the proposed motion criteria.


RESULTS
Different cup orientation was obtained as optimum for each combination of the neck angles (40 degrees and 50 degrees) and oscillation angles (120 degrees and 135 degrees). The corresponding optimum stem anteversion was also different when different neck angle was used.


CONCLUSIONS
As the margin for the impingement-free orientation of the cup was small, the optimum cup orientation and stem anteversion should be adopted specific for each combination of the neck angle and oscillation angle.
Department of Mechanical Engineering, KAIST, ME3022, Daejeon, South Korea.
Byung-Hoon
BH
Ko
Yong-San
YS
Yoon
D000203:Activities of Daily Living; D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D003198:Computer Simulation; D005260:Female; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D008297:Male; D008670:Metals; D009068:Movement / Q000502:physiology; D020959:Polyethylene; D011475:Prosthesis Failure; D016059:Range of Motion, Articular / Q000502:physiology*
D008670:Metals; D020959:Polyethylene