[Effectiveness of Kirschner wire fixation for proximal phalangeal bone avulsion fracture caused by A2 circular trochlea injury of flexor digitorum tendon].

ABSTRACT

Objective: To explore the mechanism, surgical method, and effectiveness of proximal phalangeal bone avulsion fracture caused by A2 circular trochlea injury of the flexor digitorum tendon. Methods: A retrospective analysis was conducted on the clinical data of 4 patients with proximal phalangeal bone avulsion fracture caused by A2 circular trochlea injury of flexor digitorum tendon admitted between May 2018 and September 2022. The patients were all male, the age ranged from 26 to 52 years, with an average of 33 years. The injured fingers included 1 case of middle finger and 3 cases of ring finger. The causes of injury were rock climbing of 2 cases and carrying heavy objects of 2 cases. Preoperative anteroposterior and lateral X-ray films and CT examination of the fingers showed a lateral avulsion fracture of the proximal phalanx, with a fracture block length of 15-22 mm and a width of 3-5 mm. The total active range of motion (TAM) of the injured finger before operation was (148.75±10.11)°. The grip strength of the middle and ring fingers was (15.50±2.88) kg, which was significantly lower than that of the healthy side (50.50±7.93) kg ( t=-8.280, P<0.001). The time from injury to operation was 2-7 days, with an average of 3.5 days. One Kirschner wire with a diameter of 1.0 mm was used for direct fixation through the fracture block, while two Kirschner wires with a diameter of 1.0 mm were used for compression fixation against the fracture block. The fracture healing was observed, and the TAM of the injured finger and the grip strength of the middle and ring fingers were measured. The finger function was evaluated according to the upper limb functional assessment trial standards of the Chinese Medical Association Hand Surgery Society. Results: The incisions all healed by first intention after operation. All patients were followed up 6-28 months, with an average of 19 months. X-ray films showed that all avulsion fractures of proximal phalanx reached bony union, and the healing time ranged from 4 to 8 weeks, with an average of 4.6 weeks. At last follow-up, the grip strength of the middle and ring fingers was (50.50±7.76) kg, which significantly improved when compared with preoperative one ( t=-8.440, P<0.001). The TAM of the injured finger reached (265.50±2.08)°, and there was a significant difference when compared with preoperative one ( t=-21.235, P<0.001). According to the upper limb functional assessment trial standards of the Chinese Medical Association Hand Surgery Society, the finger function was all evaluated as excellent in 4 cases. Conclusion: Using Kirschner wire fixation through bone blocks and external compression fixation of bone blocks for treating proximal phalangeal bone avulsion fracture caused by A2 circular trochlear injury of the flexor digitorum tendon can achieve good effectiveness.