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Objectives and questions: Distal femoral shaft fractures are rare but serious injuries, constituting approximately 6% of all femoral fractures. They predominantly affect young males and elderly females. Surgical treatment is the gold standard, with antegrade intramedullary nailing (IMN) being a standard technique. Fracture healing can be complicated, but data on revision rates, reasons for revision, and radiological parameters following antegrade IMN are scarce in literature. This study aims to assess revision rates, union rates and radiological parameters.

Material and methods: A retrospective review of all patients with femoral shaft fractures operated at the Kantonsspital St. Gallen from January 2007 to December 2020 was performed. Inclusion criteria were infra-isthmal femoral shaft fractures (IIFS) treated with antegrade IMN. Patients with concomitant proximal or intra-articular fractures, incomplete records, or missing radiographs were excluded. The primary endpoints were overall revision rate and reasons for revision. Secondary endpoints included time to revision, time to union, and radiographic assessments using the modified Radiographic Union Score for Tibial Fractures (mRUST) and the effective working length of the distal fracture segment (EWLD) to assess mechanical stability as a predictor. The modified RUST Score ranges from 4 to 16 points and is calculated by scoring healing of each cortex on the ap and lateral view.

Results: Screening of the database resulted in 571 femoral fractures. A total of 56 fractures met the inclusion criteria. Mean follow-up duration was 19.5 months. Of the 56 fractures treated with antegrade IMN, 16 (28.57%) required revision surgery. Reasons for revision included delayed union (10.71%), non-union (7.14%), locking screw migration (5.36%), malrotation (3.57%) and infection (1.79%). Dynamization was the most frequent revision procedure (50.00%). Median time to revision was 121 days and median time to union was 186 days, with 40.82% of fractures uniting within 180 days.

The mean mRUST score at 6 months was 11, with the medial cortex demonstrating the highest scores across all follow-ups. Mean EWLD was 0.73 (range: 0.54–0.88), but no significant correlation was found between EWLD and time to union (Spearman’s p = 0.110, p = 0.471) or revision rate (p = 0.961, Mann-Whitney test).

Discussion and conclusions: Our study found high revision rates following antegrade IMN for IIFS fractures of 28.57%, which underscores the complexity of managing these fractures. Delayed union and non-union were the most common reasons for revision. However, antegrade IMN is an effective treatment for IIFS fractures, achieving satisfactory union rates at final follow-up.