Mechanistic Insights Into Lag Screw Cut-Out: The Impact of Distal Locking Technique in Elderly Trochanteric Hip Fractures

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Abstract
Introduction Proximal femoral nails commonly used to treat trochanteric hip fractures in the elderly have different distal fixation options such as interlocking screws and claws. The aim of this study was to compare the failure rate and migration of the fixation construct during the follow-up of screw- and claw-fixed nails in elderly patients with trochanteric hip fractures. Materials and Methods A retrospective case–control study was conducted including patients aged 65 years or older and treated with a proximal femoral nail between 2018 and 2023. Patients were grouped according to the type of distal locking: screw- and claw-fixed. Demographic data and follow-up radiographs were obtained from hospital records. Follow-up radiographs were analyzed to assess fracture type, treatment failure through lag screw cut-out, and migration of the nail and the lag screw over time. Two types of migration were evaluated; distal migration of the nail in the medullary canal (nail migration distance; NMD) and migration of the lag screw in the femoral head (lag screw migration ratio; LSM). Results There were 339 patients with a mean follow-up of 7.2 ± 4.2 months (208 in the screw-fixed group and 131 in the claw-fixed group). The groups were similar in terms of age, sex, fracture type, and stability. While 16 (7.7%) cut-outs were observed in the screw-fixed group, there were 1 (0.8%) in the claw-fixed group (p = 0.004). Mean nail migration was 1.3 ± 2.1 mm for screw-fixed nails and 4.8 ± 5.8 mm for claw-fixed nails (p < 0.001). Lag screw migration ratio was significantly higher in screw-fixed nails (4.2% vs 2%, respectively, p < 0.001). Conclusions Claw-fixed nails are significantly more likely to slide in the medullary canal, resulting in a reduced lag screw cut-out compared to screw-fixed nails in elderly patients with trochanteric hip fractures.

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