The distal 1/3 fracture of the humeral shaft refers to the fracture from below the middle part to 2 cm above the condyle of the humerus. The structural and anatomical characteristics of the distal 1/3 of the humeral shaft make it a prone site for fracture. As the aging of society progresses, about 85% of the patients occur in people over 50 years of age, with the incidence peaking in the 60-90-year age group. For distal humerus fractures, non-surgical methods such as upper limb suspension fixation usually result in good treatment if there is no significant displacement. However, for severely displaced or comminuted fractures, surgical treatment with locking plate internal fixation is usually more effective. However, there are inconsistent conclusions about the clinical effectiveness of different internal fixation procedures, which increases the difficulty of selecting an appropriate clinical treatment strategy. The efficacy varies, especially in treating distal humerus 1/3 fracture with double plate internal fixation. Therefore, it is essential to analyze the factors affecting the therapeutic effect based on clinical data, evaluate the prognosis of patients accordingly, and provide timely and reasonable treatment to improve the quality of life of patients with distal humerus 1/3 fracture.

To investigate the biomechanical characteristics of double plate internal fixation in treating distal humerus 1/3 fracture and its effect on elbow joint function and elbow joint motion.

A total of 160 patients with distal 1/3 fracture of the humerus admitted to our hospital from January 2020 to December 2022 were randomly divided into a traditional internal fixation group (80 cases) and a double plate internal fixation group (80 cases) . The two groups’ surgical indicators, postoperative Mayo score of elbow function, elbow joint score, complication rate, and improvement of shoulder joint function were compared. The C1 fracture model of the distal humerus was established using artificial bone. Traditional internal fixation and double plate internal fixation were used, respectively. The model was modeled using special software, various biomechanical tests were simulated, and finite element analysis was performed. The patients were divided into the excellent group (≥75 points) and the non-excellent group (<75 points) according to the postoperative Mayo score. The primary data of the two groups were analyzed, and the factors affecting the surgical efficacy of the patients were analyzed using logistic regression.

The incision length, operation time, intraoperative blood loss, and fracture healing time in the double-plate internal fixation group were significantly lower than those in the traditional internal fixation group (P<0.05) . The improvement of elbow joint function Mayo score, elbow joint motion, elbow joint score, and shoulder joint function in the double-plate internal fixation group were significantly higher than in the traditional internal fixation group (P<0.05) . The complication rate of the double plate internal fixation group (6.25%) was significantly lower than that of the traditional internal fixation group (21.25%) (P<0.05) . The finite element analysis results showed that the stress distribution was more uniform, the strain energy density was lower, the fracture stability was higher, and the fracture healing speed was faster in the double-plate internal fixation group. Logistic analysis showed that age, gender, fracture type, internal fixation mode, intraoperative blood loss, fracture-healing time, and complication rate were the most important factors influencing the surgical outcome of patients (OR=8.32, 95% CI=2.54-27.28, P<0.01) .

The treatment of distal 1/3 humerus fracture with double plate internal fixation has good biomechanical properties, can effectively improve fracture stability, promote fracture healing, improve elbow joint function and elbow joint motion, and reduce the incidence of complications. It is a safe, effective, and reliable treatment method.