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Size and location of posterior wall fragment on CT can predict hip instability in a cadaveric model
Theerachai Apivatthakakul1, Jason L Koerner2, Sutiwat Luangsod3
1Department of Orthopaedics, Faculty of Medicine, Chiang Mai University, Thailand; Excellence Center in Osteology Research and Training Center, Chiang Mai University.
Insights
Posterior wall acetabular fractures with fragment sizes of 20% and 25% were unstable at a 40° fracture angle. Even a 15% fragment size became unstable at a 60° fracture angle, indicating fragment size and angle impact hip stability.
Area of Science:
- Orthopedic surgery
- Biomechanics
- Trauma research
Background:
- Hip instability is a complication of posterior wall acetabular fractures.
- Predicting instability is crucial for surgical planning and patient outcomes.
- Previous research has not fully identified factors influencing hip stability in these fractures.
Purpose of the Study:
- To determine the influence of posterior wall fracture fragment size (FS) and fracture angle (FA) on hip joint stability.
- To establish a CT-based measurement for predicting hip instability in posterior wall acetabular fractures.
Main Methods:
- Utilized six human cadavers (12 hips) with pre-procedure CT evaluation.
- Randomized specimens into three groups based on FS (15%, 20%, 25%).
- Assessed hip stability under anesthesia, increasing FA from 40° in 20° increments until instability occurred.
Main Results:
- A 15% FS with a 40° FA demonstrated stability in all hips.
- Increasing FA to 60° in the 15% FS group resulted in instability (subluxation or dislocation).
- All hips with 20% and 25% FS were unstable at a 40° FA.
Conclusions:
- A posterior wall fracture fragment size of 15% and fracture angle of 40° were found to be stable.
- Increasing fragment size or fracture angle led to instability.
- CT-based measurements of FS and FA can help predict hip instability in posterior wall acetabular fractures, requiring further clinical validation.
Purpose:
Previous research has been unable to elucidate the exact factors that contribute to hip instability in the setting of posterior wall acetabular fractures. The purpose of this study was to determine the influence of posterior wall fracture fragment size and fracture angle on the stability of the hip joint in a cadaveric model.
Methods:
Six fresh human cadavers (12 hips) were used. Specimens underwent pre-procedure CT evaluation and were then randomized to one of three groups: posterior wall fragment size (FS) of 15%, 20% and 25%. Osteotomies were performed starting at a fracture angle (FA) of 40°. The specimens underwent an exam under anesthesia (EUA). If the hip remained stable, the fracture angle was increased in 20° increments and re-tested until it became unstable.
Results:
In the group with a FS of 15%, all hips were stable with a FA of 40°. Increasing the FA to 60° caused all hips to be unstable (subluxation or dislocation). In the group with a FS of 20% and 25%, all hips were unstable with a FA of 40°.
Conclusion:
In all specimens, a FS of 15% and FA of 40° were stable on EUA. Varying combinations of increasing FS size and increasing FA were all unstable. This study provides data for a CT-based measurement to predict hip instability in the setting of posterior wall acetabular fractures based on FS and FA. More research is required to validate this data in a clinical setting.
