Statistics show that elbow fractures account for about 4% of fracture types in adults, and distal humerus fractures account for 30% of all elbow fractures. Due to the complex neurovascular structure of the distal humerus, it is often difficult to treat such fractures, and surgeons face many challenges. Accurate movement of the ulnar nerve and its protection throughout open reduction and internal fixation (ORIF) operation is crucial, as it can significantly reduce the risk of iatrogenic nerve injury. Nevertheless, ulnar neuropathy is a relatively common complication after ORIF surgery for distal humeral fractures, with an incidence of up to 38%. A variety of potential causes can cause ulnar nerve dysfunction. Among them, ulnar nerve preposition is a technical method often considered in the surgical intervention of elbow fractures. Fascia covering adequately protects the ulnar nerve during the preposition process from subsequent damage to the ulnar nerve by surrounding tissues (scar, ectopic ossification, healed bone tissue) and internal fixation devices.On the other hand, the method used by the surgeon to peel the ulnar nerve during the preposition process will extensively separate the soft tissue, and there is a risk of iatrogenic damage to the ulnar nerve. At present, in the field of orthopedic trauma, whether or not ulnar nerve preposition is used by surgeons in open reduction and internal fixation of elbow fractures, especially distal humerus fractures, and how this operation affects the function of ulnar nerve after surgery is still a controversial issue. According to the study of Ruan et al., ulnar nerve preposition is significantly effective in improving ulnar nerve dysfunction during open reduction and internal fixation. However, other studies have suggested that ulnar preposition has no additional benefit and may even increase the risk of ulnar nerve dysfunction.

To investigate the clinical efficacy of ulnar nerve preprocessing in open reduction and internal fixation of distal humerus fracture.

From January 2014 to December 2020, 76 patients with distal humerus fracture (AO/OTA classification 13-C) requiring open reduction and internal fixation in the Department of Orthopedics, Beijing Chaoyang Hospital Affiliated to Capital Medical University were continuously included in this study. They were divided into two groups according to whether the anterior treatment covered the inferior ulnar nerve with forearm fascia during the operation: pretreatment group =17 cases, control group =59 instances. Patients ' general data and surgical information were collected, including gender, age, fracture type, and operation time. Follow-up information was also recorded, including the healing time of the affected limb bone and postoperative complications. A unified follow-up node (1 year after surgery) was intercepted, and the outpatient doctor would measure the patient’s elbow joint motion (elbow flexion and extension Angle and forearm rotation Angle) . In order to objectively and comprehensively quantify the postoperative performance of the patient’s elbow, the Mayo elbow performance score was used in this study. MEPS) . Patients with symptoms or abnormalities of the ulnar nerve in the affected limb were recorded on time. The modified McGowan prognostic rating was used to quantify the clinical status of the ulnar nerve in the patients after surgery.

A total of 76 patients with distal humerus fractures were followed up for at least one year, including 17 patients in the ulnar nerve preposition group, with an average age of 54.3 (31-71) years, and 59 patients in the ulnar nerve non-preposition group, with an average age of 56.7 (28-73) years. The two groups had no statistically significant differences in fracture classification and fracture healing time. In the anterior ulnar nerve group, the mean flexion and extension range of the elbow joint was (130.4±12.7) ° and (25.6±3.0) °, and the mean pronation and supination range of the forearm were (60.8±5.5) ° and (61.8±5.4) °. In the non-anterior ulnar nerve group, the mean flexion and extension range of the elbow joint was (128.6±9.3) ° and (24.1±3.4) °, and the mean pronation and supination range of the forearm were (59.7±4.3) ° and (61.2±5.2) °. There was no significant difference in the elbow-forearm range of motion between the two groups with ulnar nerve anterior/non-anterior (P > 0.05) . Follow-up results of patients with inferior ulnar nerve preposition covered by fascia indicated 9 cases of ulnar nerve injury, and a follow-up review found that there were still 4 cases of adverse events with poor recovery of residual ulnar nerve. The modified McGowan rating system for these patients indicated that there were 7 cases of grade 1 and 2 cases of grade 2. intraclass correlation coefficient (ICC) was used to evaluate the reliability and validity of the scoring system, and it was found that both were good (0.78 and 0.84) . There were 10 cases of ulnar nerve symptoms in the patients who did not undergo ulnar nerve preposition during the operation, and four cases of poor residual ulnar nerve function were observed in the follow-up review, including 8 cases in grade 1 and 2 cases in grade 2 of the modified McGowan classification. The results indicated no statistical difference between ulnar nerve preposition and non-preposition (P > 0.05) .

Ulnar nerve preposition during ORIF for distal humerus fractures does not provide any benefit and may put patients at greater risk of nerve damage. Based on this, the present study suggests that the clinical effect of in situ ulnar nerve release in the surgical treatment of distal humerus fracture is insignificant.