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Published on: September 7, 2022
Study of hip joint dislocation after total hip arthroplasty
Toshinori Masaoka1, Kengo Yamamoto, Takaaki Shishido
1Department of orthopedic surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, 160-0023 Tokyo, Japan. tmumasaoka@nifty.com
Insights
Total hip arthroplasty dislocation risk is linked to cup anteversion angle. A safe zone of 20-30 degrees is identified, potentially improved by matching stem antetorsion to bone shape for enhanced hip joint stability.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Arthroplasty Research
Background:
- Hip joint dislocation is a significant complication following total hip arthroplasty (THA).
- Identifying predisposing factors is crucial for improving patient outcomes and implant survival.
- Patient background variables and implant positioning are key areas of investigation.
Purpose of the Study:
- To determine the factors contributing to hip joint dislocation after total hip arthroplasty.
- To analyze patient background variables and their correlation with dislocation incidence.
- To establish optimal anteversion and antetorsion angles for improved THA stability.
Main Methods:
- Retrospective analysis of 317 total hip arthroplasty cases.
- Comparison of demographic and surgical variables between hips that dislocated and those that did not.
- Statistical analysis to identify significant differences, focusing on cup anteversion and stem antetorsion angles.
Main Results:
- A dislocation rate of 3.2% (10 out of 317 hips) was observed.
- The anteversion angle of the acetabular cup was the only significant differentiating factor between dislocated and non-dislocated hips.
- A potential safe zone for cup anteversion was identified between 20 and 30 degrees.
Conclusions:
- Cup anteversion angle is a critical factor influencing hip joint stability post-THA.
- Optimizing cup anteversion within the 20-30 degree range may reduce dislocation risk.
- Individualized stem antetorsion adjustment, complementing cup anteversion, can further enhance hip joint stability and minimize dislocation.
Abstract:
The present study was undertaken to identify the factors responsible for hip joint dislocation after total hip arthroplasty, laying emphasis on analysis of the background variables of the patients. Of the 317 hips included in the study, ten (3.2%) dislocated. Only the anteversion angle of the cup differed significantly between the dislocation group and the dislocation-free group. The safe zone of the anteversion angle seems to be between 20 and 30 degrees. but it is also essential to set the antetorsion angle of the stem to match the shape of individual bones to create a more stable hip joint. This safe zone may be expanded by the additive effect of antetorsion angle of the stem.