Correlation between cephalic screw positioning of Standard Gamma 3 Nail for intertrochanteric fractures and cut-out incidence.

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Lateral fractures of proximal femur are the most frequent fractures in elderly people. Internal fixation using medullary nails is the gold standard of treatment (Gamma 3 nail is the most implanted device) due to reduced incidence of complications than other devices. We report our experience in treating this kind of fractures with Gamma 3 nail, between January 2015 and December 2021. We performed a retrospective cohort study of patients treated in our orthopaedic department; level of clinical care is III: 559 patients (431 females and 128 males, with an average age of 85.3years) with lateral femoral neck fracture. All patients were surgically treated with Gamma 3 standard nail (SGN). We evaluated preliminary X-rays to classify fractures, according to AO-OTA classification and post-operative X-ray to verify cephalic screw position site, according to areas described by Cleveland in 1959: we measured tip-to-apex distance (TAD) and tip-to-apex calcar referred distance (CalTAD). Finally Chang reduction quality criteria (CRQC) for fracture reduction of trochanteric fractures were determined using preoperative or postoperative Antero-Posterior (AP) and lateral radiographs in a Picture Archiving and Communication System (PACS). Incidence of cut-out was evaluated in relation with these parameters. Patients were divided into 2 groups: first group had cephalic screw in optimal positions (5-8-9), the other group had cephalic screw in other positions. In 328 patients (58.7%) screw was in positions 5-8-9, in 231 patients (41.2%) screw was in not-optimal position. Median TAD was 19.1±7.0mm (range=0.0-50.5); in 463 patients (82.8%) TAD was≤25mm. Median CalTAD was 21.4±4.7mm (range=5.7-39.2); in 105 patients (79.4%) CalTAD was≤25mm. Cut-out was observed in 8 cases (1.43%). Multivariate analysis showed a significant correlation (p<0,05) between incidence of cut-out and fracture type 31A2 and with TAD values>25mm. Cephalic screw position did not influence incidence of cut-out. In order to obtain fracture healing with a low risk of failure, in particular cut-out, it is necessary to obtain good reduction of fracture and optimal lag screw position in order to achieve a TAD inferior to 25mm.