Failure Mechanism of Dynamic Hip Screw for Femoral Intertrochanteric Fracture – An Experience in Taichung Veterans General Hospital

The dynamic hip screw (DHS) is the treatment of choice for femoral intertrochanteric fracture. Cut-out of the lag screw from the femoral head head is the most common cause of mechanical failure. We reviewed 295 femoral intertrochanteric fractures treated with a dynamic hip screw in our hospital and analyzed possible causes for failure of the device. Variables analyzed includedpatient sex and age, bone quality, fracture pattern, reduction, placement of the lag screw, medial buttress reinforcement, additional fixation, and sliding capacity. Cut –out rate was 11.9% (35 cut-outs in 295 fractures). Unstable fractures had a significantly higher cut-out rate than stable fractures (34.4% vs. 5.6%). Variables that significantly predicted screw cut-out included slided sliding capacity (p=0.0133) and sex (p=0.0273) for stable fractures, and medial buttress reinforcement (p=0.0005), screw position in the frontal plane (p=0.0054), frontal reduction (p=0.0075), sliding capacity (p=0.0141), screw position in the saggital plane (p=0.0295), and saggital reduction (p=0.0450) for unstable fractures. We conclude the dynamic hip screw is the favorite treatment modality for most cases of femoral intertrochanteric fractures, despite the development of newer implants, attention is fiven to key points, such as avoidance of the followings; varus reduction in the frontal plane, retroversion reduction in the sagittal plane, screw placement in the superior region of the femoral head in the frontal plane, and screw placement in the anterior of the femoral head in the femoral head in the sagittal plane. Other key considerations include reinforcement of the medial buttress by posteromedial fragment fixation in unstable fractures if possible, use of short-barrel plates if the lag screw is shorter than 85 mm, and allowing adequate sliding capacity.

並列關鍵字

Intertrochanteric fracture ； dynamic hip screw (DHS) ； cut-out ； medial buttress, sliding capacity

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