Correlation between modified trochleocapitellar index and post-traumatic elbow stiffness in type C2-3 distal humeral fractures among adults

The purpose of this study was to propose the modified trochleocapitellar index (mTCI), assess its reliability, and evaluate its correlation with post-traumatic elbow stiffness in type C2-3 distal humeral fractures among adults.From January 2013 to June 2017, a total of 141 patients with type C2-3 distal humeral fractures were included. The mTCI was calculated as the ratio between the modified trochlear and capitellar angles relative to the humeral axis (mTCI-HA), lateral humeral line (mTCI-LHL), and medial humeral line (mTCI-MHL) from anteroposterior radiographs taken immediately after the operation. The patients were divided into group A (with elbow stiffness) and group B (without elbow stiffness) based on follow-up results. To determine risk factors for elbow stiffness, univariate and logistic regression analyses were performed on each radiographic parameter separately, together with other clinical variables. Interrater reliability was assessed for all measurements.Specific optimal ranges of value were identified for mTCI-HA (0.750-0.875), mTCI-LHL (0.640-1.060), and mTCI-MHL (0.740-0.900), beyond which the likelihood of elbow stiffness significantly increased (P.001). By multivariate analysis, mTCI-HA (odds ratio [OR] 26.22, 95% confidence interval [CI] 3.39-203.07, P = .002), mTCI-LHL (OR 5.37, 95% CI 2.17-13.28, P.001), and mTCI-MHL (OR 5.95, 95% CI 1.91-18.56, P = .002) values beyond the optimal ranges were identified as the independent risk factors for elbow stiffness. The interrater reliability of mTCI-HA, mTCI-LHL, and mTCI-MHL was 0.986, 0.983, and 0.987, respectively.The mTCI measurement method is reliable. Either too small or too large mTCI values were associated with post-traumatic elbow stiffness among adult patients with type C2-3 distal humeral fractures. The mTCI-HA showed a better predictive value than mTCI-LHL and mTCI-MHL.