[Treatment of the fifth metacarpal neck fracture with elastic intramedullary nail under the guidance of high frequency ultrasound].

Objective: To analyze the feasibility and effectiveness of elastic intramedullary nail fixation for the fifth metacarpal neck fracture under the guidance of high frequency ultrasound.

Methods: The clinical data of 30 patients with the fifth metacarpal neck fractures who were treated with elastic intramedullary nails fixation under the guidance of high frequency ultrasound and met the selection criteria between May 2013 and September 2017 were retrospectively analysed. There were 24 males and 6 females, the age ranged from 18 to 58 years, with an average of 31.4 years. The head-shaft angle of the fifth metacarpal was (55.6±11.3)°. The time from injury to operation was 12 hours to 8 days, with an average of 2.4 days. The operation time, number of intraoperative fluoroscopy, fracture reduction, complications, and fracture healing time were recorded. The head-shaft angle of the fifth metacarpal on the affected side after fracture healing were measured and compared with the healthy side. At last follow-up, the active range of motion of the fifth metacarpophalangeal joint of both sides were measured, and the function was evaluated by using the total active movement (TAM) evaluation standard of the Hand Surgery Association of Chinese Medical Association.

Results: The operation time was 22-40 minutes, with an average of 32.4 minutes; the intraoperative fluoroscopy was performed once; ultrasound images and X-ray fluoroscopy showed that the fracture was well reduced and no adjustment was required. The incisions healed well after operation, without tendon adhesion or local numbness. All 30 patients were followed up 8-16 months, with an average of 11.7 months. The fracture healing time was 4-8 weeks, with an average of 5.6 weeks. The head-shaft angle of the fifth metacarpal was (13.2±1.4)°, which was significantly improved when compared with preoperative value ( t =-20.02, P =0.00); and there was no significant difference ( t =1.94, P =0.06) when compared with the healthy side [(12.6±1.0)°]. At last follow-up, the active range of motion of the fifth metacarpophalangeal joint on the affected side was (89.4±2.4)°, showing no significant difference ( t =-1.58, P =0.13) when compared with the healthy side [(90.3±2.0)°]. According to the TAM evaluation standard of the Hand Surgery Association of Chinese Medical Association, all patients were considered to be excellent.

Conclusion: The effectiveness of elastic intramedullary nail fixation for the fifth metacarpal neck fracture under the guidance of high frequency ultrasound is definite. It can dynamically observe the fracture reduction from different angles, reduce ionizing radiation and postoperative complications.