To investigate the relationship between fracture line morphology, bone quality and fracture type in the posterior medial humeral talus of proximal humerus fractures.

Retrospective analysis of CT data of patients with proximal humeral fractures diagnosed in our hospital from June 2020 to June 2021. Based on 3D reconstruction, the fracture line of the posterior medial humeral calcar was described, substituted into the proximal humeral template to depict the fracture map;and the coordinates of the turning point of the posterior medial fracture line were recorded, and the most concentrated coordinate interval was displayed using Matlab heat mapscript, substituted into the proximal humeral template to mark the area of concentration of the turning point of the fracture line. And according to the inclination angle of the humeral head to establish internal and external rotation and normal group, three groups of humeral distance posterior medial bone density, bone thickness and fracture horizontal line angle were performed and recorded by unordered multicategorical Logistic regression analysis.

A total of 62 patients with proximal humeral fractures were included; 21 (34%) were internally turned, 24 (39%) were externally turned and 17 (27%) were normal. Inversion: bone density 0.59±0.12 g/cm³, bone thickness 2.33±0.48 mm, fracture horizontal line angle 4.54°±14.13°. Normal: Bone density 0.57±0.15 g/cm³, bone thickness 2.60±0.33 mm, fracture level angle -1.87°±9.98°. Ectropion: bone density 0.62±0.11 g/cm³, bone thickness 2.69±0.54 mm, fracture horizontal angle -5.64°±20.03°. Epiphyseal extension occurs most often posteriorly and medially, with the fracture line turning point located posterior to the greater tuberosity. Unordered multicategorical Logistic regression of the data showed that: inversion fracture horizontal line angle (β=0.06, P=0.018), statistically significant, OR=1.06 [95%CI (1.00, 1.12)]; bone thickness (β=-2.02, P=0.041), statistically significant, OR=0.13 [95%CI (0.03, 0.71)]; bone density (β=-0.43, P=0.887), not statistically significant; none of the ectropion patterns were statistically significant (P>0.05).

The trend of the fracture line and bone thickness of the posterior medial humeral calcar are factors that influence internal rotation of the humeral head. The incidence of internal rotation is positively correlated with the upward trend of the fracture line and negatively correlated with the thickness of the bone. The fracture line turning point is most often located posterior to the greater tuberosity.

Proximal humerus fracture; Posterior medial humeralcalcar; Fracture line morphology; Bone quality