Using the method of four-dimensional finite element analysis of bone bearing capacity, using the methods of parallel CT scanning of both legs, geometric modeling of both legs and finite element analysis for postoperative patients with long bone fracture, through the comparative analysis of the same part of the healthy limb, and according to the changing trend on the time axis, to judge the degree of bone healing of the target bone segment, and to assist in the diagnosis of bone healing, delayed union and non-union of long bone.

From 2014 to 2017, 26 cases of clinically diagnosed femoral bone healing were systematically followed up. The CT data were used for three-dimensional modeling and material assignment, and the three-dimensional finite element model of the long bone of the lower limb was established, and the bearing force of the target bone segment was simulated and calculated. Through the finite element analysis software, the uniaxial compression experiment was carried out to analyze the load of the target bone segment of both legs. Combined with the maximum value of Mises stress and the total area under the stress-strain curve, the ratio analysis was used as an index to observe the degree of bone healing, the clinical diagnosis was modified twice, and the final clinical healing results were observed.

All patients were followed for 2 to 4 years, with an average follow-up time of 3.4 years. There were 26 cases clinically diagnosed with delayed bone union and complete bone union. The finite element bone bearing capacity analysis was used to analyze the 26 cases for a total of 54 times. The revised diagnosis was: 6 cases (23.1%) were bone union. Poor bone union was determined in 16 cases (61.5%). Bone nonunion was determined in 4 cases (15.4%). The ratio analysis was performed using the mises maximum stress and the total area under the stress-strain curve, and the chi-square test was performed (P>0.05), showing no statistical difference. Fisher's exact probability test (P=0.170) showed statistical significance, and there was a non-random correlation between the two methods.

By using the technique of finite element bone bearing capacity analysis, the degree of bone healing at the fracture end can be analyzed quantitatively in three dimensions, combined with the description of the changing law in the time axis. It can provide a relatively objective diagnostic basis for the clinical diagnosis of nonunion and delayed union. This method can also well observe that the bone healing process of high energy injury is difficult to evolve according to the classical bone healing theory, and it usually takes a longer time for bone healing, but it can show its slow healing trend and has a broad application prospect.