[Imaging study on tibial torsion malreduction after tibial intramedullary nailing].

OBJECTIVE: To explore changes in physiological torsion angle of tibia and torsion angle of tibia after intramedullary nailing for tibial shaft fractures, and to determine whether torsion angle of the uninjured side of tibia could be used as a reference standard for judging the recovery of torsion angle of the injured side after operation.

METHODS: A retrospective analysis was conducted on clinical data of 154 patients with unilateral tibial shaft fractures who underwent closed reduction with intramedullary nails from January 2018 to December 2023. There were 110 males and 44 females;aged from 22 to 90 years old with an average of (41.0±18.6) years old;82 patients on the right side and 72 patients on the left side;95 patients with type A, 35 patients with type B, and 24 patients with type C according to AO fracture classification;6 patients with proximal tibial fractures, 47 patients with middle tibial fractures, 91 patients with distal tibial fractures, and 10 patients with segmental fractures;127 patients associated fibular fractures, including 30 patients with proximal fibular fractures, 43 patients with middle fibular fractures, 38 patients with distal fibular fractures, and 16 patients with segmental fibular fractures. Postoperative CT was used to assess bilateral tibial torsion angles. The incidence, grading and distribution of poor tibial torsion angle reduction were statistically analyzed. The differences in physiological tibial torsion angles of healthy limbs on the left and right sides were also examined. The distribution of poor reduction of left or right tibial torsion angles after correction of baseline differences was analyzed, the classification of tibial torsion angles after baseline correction was summarized, and the related factors of poor torsion angle reduction were investigated.

RESULTS: Among 55 patients (36%), there was a 10° or greater change in tibial torsion angle after operation;there was a difference of approximately 10° in torsion angle between the left and right tibial intramedullary nails after operation, which was statistically significant (P=0.000). After operation, the right tibial shaft fracture was more likely to result in abnormal external rotation, while the left tibial shaft fracture was more prone to abnormal internal rotation. There was a statistically significant difference in distribution of abnormal torsional angle reduction between left and right sides (P=0.000). The normal tibia had a tibial torsion and external rotation angle. The right side (41.1±8.0)° has an additional 4° of external rotation compared to the left side (37.0±8.2)° (P<0.01). After the 4° correction, the incidence of poor reduction of torsion angle decreased (45 patients, 29%), and the distribution of poor reduction of torsion angles on the left and right sides became more balanced (P=0.588), and there was no statistically significant difference in absolute values of torsion angles on the left and right sides (P=0.192). The classification of 30 patients with poor reduction of torsion angle after 4° correction changed. There were significant differences between AO classification of tibial fractures(P=0.002), the location of tibial fractures (P=0.001), fibular fractures and their locations (P<0.001) and incidence of poor reduction of tibial torsion angle.

CONCLUSION: There is a relatively high incidence of poor reduction of tibial torsional external rotation angle after intramedullary nail treatment. The normal anatomical tibia has a tibial torsional external rotation angle, and there is a 4° difference between the left and right sides. This is of great significance for the precise diagnosis of poor reduction of the tibial torsional angle after intramedullary nail treatment for tibial fractures. Patients with type C fractures, segmental tibial fractures, and combined fibular fractures (especially segmental fractures) are more likely to have poor reduction of the tibial torsional angle after intramedullary nail treatment. Clinicians should pay special attention to the recovery of the tibial torsional external rotation angle when performing intramedullary nail treatment for these types of tibial fractures.