Infrapatellar Approach to Intramedullary Nail Fixation of Distal One-Fourth Tibial Fractures.

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This study aimed to report the radiological outcomes and risk factors for malalignment of fractures in the distal one-fourth of the tibia treated with intramedullary nailing via the infrapatellar approach. This study retrospectively analyzed 60 patients (37 men and 23 women; mean age, 45.4 years) who had distal one-fourth tibial fractures and were treated with intramedullary nailing using the infrapatellar approach. These patients were treated between January 2009 and December 2021, with a minimum follow-up of 1 year. Fractures were classified according to the Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association system: 25 were type 42A, 30 were type 42B, and 5 were type 43A. Radiographic outcomes focused on bone union and malalignment, defined as a valgus deviation greater than 5° compared to the unaffected side. Potential risk factors for malalignment, including open fractures (9 cases, 15%), distal tibial extension (20 cases, 33%), and distal fibular fractures (24 cases, 40%), were documented. Bone union was achieved in all cases, with an average duration of 3.2 months (range, 3-5 months). No cases of postoperative wound infection or neurovascular damage were observed. The average coronal plane malalignment was 2.6° of valgus (range, 0°-9.3°), with significant malalignment (over 5°) occurring in 5 patients (8.3%). Comparison of the malalignment (n = 5) and normal (n = 55) groups showed a statistically significant difference in distal bone fragment length (average, 66.5 mm vs. 77.2 mm; p = 0.008) but no significant differences in other variables. A change-point analysis revealed that cases with a primary fracture line < 65 mm showed 4.5° of coronal malalignment, while those with > 65 mm showed 2.3°; the difference was statistically significant (p = 0.01). Intramedullary nailing using the infrapatellar approach for distal one-fourth tibial fractures results in successful bone union with a low incidence of valgus malalignment. However, careful attention is necessary to prevent angular deformities, especially when the distal fragment is short.