[Effect of tibial rotation on knee and ankle function in patients with extra-articular distal tibial fractures after minimally invasive plate osteosynthesis treatment].

Objective: To investigate the effect of tibial rotation on knee and ankle function in the patients with extra-articular distal tibial fractures after minimally invasive plate osteosynthesis (MIPO) treatment.

Methods: A retrospective analysis was conducted on 45 patients with extra-articular distal tibial fractures who underwent MIPO between January 2021 and December 2022. There were 20 males and 25 females, aged from 19 to 68 years (mean, 43.6 years). The causes of fractures included falling from heights in 11 cases, traffic accidents in 15 cases, bruising by a heavy object in 7 cases, and falling in 12 cases. The time from injury to hospitalization was 1-6 hours (mean, 3.7 hours). There were 28 cases of simple tibial fractures and 17 cases of tibial fractures combined with ipsilateral fibular fractures; 9 cases of open fractures and 36 cases of closed fractures. According to AO/Orthopaedic Trauma Association (AO/OTA) classification, the distal tibial fractures were classified as type 43A1 in 12 cases, type 43A2 in 17 cases, and type 43A3 in 16 cases. During follow-up, the Lower Limb Function Score (LEFS), American Orthopaedic Foot and Ankle Society (AOFAS) score, and Knee Injury and Osteoarthritis Score (KOOS) were used to evaluate the lower limb, ankle, and knee joint functions, respectively. The range of motion (ROM) of the knee and ankle joints was measured. The Short Form Health Survey (SF-36) was used to assess the quality of life of the patients. The fracture healing was observed by anteroposterior and lateral X-ray films of the ankle joint. The bilateral tibial rotation angles were measured on CT and the differences between the affected and healthy sides were caculated. The difference ≥10° was judged as tibial malrotation. According to whether there was tibial malrotation, the patients were allocated into a normal group and a malrotation group for efficacy comparison.

Results: The incisions of all patients healed by first intention without any early complications. All patients were followed up 12-26 months (mean, 18.6 months). Imaging re-examination showed that all fractures healed, with a healing time of 9-14 weeks (mean, 11.2 weeks). At last follow-up, the LEFS score was 60-68 (mean, 62.3); the AOFAS score was 89-97 (mean, 92.6); the KOOS score was 158-164 (mean, 161.3). The ROM of ankle was 40.0°-45.0° (mean, 42.8°) in flexion and 10.5°-22.0° (mean, 17.7°) in extension; the ROM of knee was 130.0°-135.0° (mean, 132.6°) in flexion and -8.8°- -5.0° (mean, -7.1°) in extension. The SF-36 score was 89-93 (mean, 90.7). The absolute value of difference of tibial rotation angle was 2.6°-17.3° (mean, 8.9°) in 45 patients, and the malrotation was observed in 15 patients (33.3%), including 10 cases of internal rotation and 5 cases of external rotation. There was no significant difference ( P>0.05) in the proportion of patients with fibular fractures before operation between the malrotation group and the normal group, as well as in the AOFAS score, KOOS score, LEFS score, SF-36 score, and ROMs of knee and ankle joints at last follow-up.

Conclusion: The incidence of tibial malrotation after MIPO treatment for extra-articular distal tibial fractures is relatively high, but it has no significant effect on knee and ankle functions. However, careful manipulation and precise evaluation should be performed during operation to avoid the occurrence of malrotation.