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Updated: Aug 15, 2026
Reverse Total Shoulder Arthroplasty
Published on: July 5, 2011
Dislocations after total hip-replacement arthroplasties
Insights
Total hip replacement dislocations are linked to acetabular cup orientation. Specific anteversion and lateral opening angles reduce dislocation risk, especially within the first 30 days post-surgery.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
Background:
- Total hip replacement (THR) is a common procedure to alleviate hip pain.
- Dislocation remains a significant complication following THR.
- Acetabular cup positioning is crucial for implant stability and function.
Purpose of the Study:
- To investigate the relationship between acetabular cup orientation and dislocation after total hip replacement.
- To identify specific orientation parameters associated with increased dislocation risk.
- To define a "safe" range for acetabular cup orientation to minimize dislocations.
Main Methods:
- Analysis of 300 total hip replacement cases.
- Precise measurement of acetabular component anteversion and lateral opening angles.
- Correlation of cup orientation with dislocation events (anterior and posterior).
- Evaluation of risk factors including time post-surgery and surgical history.
Main Results:
- Nine dislocations (3%) occurred in 300 THR procedures.
- Anterior dislocations were significantly associated with increased acetabular-component anteversion.
- No significant correlation was found between cup orientation angle and posterior dislocation.
- Dislocation rate was 1.5% within the "safe" range (15 +/- 10 degrees anteversion, 40 +/- 10 degrees lateral opening) versus 6.1% outside this range.
- Higher dislocation risk observed within 30 days post-surgery and in patients with prior hip surgery.
Conclusions:
- Acetabular component anteversion is a critical factor in anterior hip dislocations after THR.
- A specific range of acetabular cup orientation (15 +/- 10 degrees anteversion, 40 +/- 10 degrees lateral opening) is associated with a lower dislocation rate.
- Optimizing acetabular cup positioning is essential for improving total hip replacement outcomes and reducing complication rates.
Abstract:
In a series of 300 total hip replacements, nine (3 per cent) dislocated. Precise measurements of the orientation of the acetabular cup were made and it was found that anterior dislocations were associated with increased acetabular-component anteversion. There was no significant correlation between cup-orientation angle and posterior dislocation. The dislocation rate for cup orientation with anteversion of 15 +/- 10 degrees and lateral opening of 40 +/- 10 degrees was 1.5 per cent, while outside this "safe" range the dislocation rate was 6.1 per cent. Other factors that were documented include time after surgery (with the greatest risk in the first thirty days) and surgical history (with a greater risk in hips that have had prior surgery).
