Accuracy of MRI and X-Ray Measurement of Displacement Distance of Humeral Lateral Condyle Fractures.

OBJECTIVE To investigate the accuracy of X-ray and magnetic resonance imaging (MRI) measurements in evaluating the displacement of humeral lateral condyle fracture (HLCF) in different positions of the forearm based on human cadaveric HLCF models. METHODS Three human cadaveric elbow HLCF fracture models were successfully established. The wrist joint was fixed, and the forearm was rotated forward along the mid-axis. The maximum distance between the two segments of the lateral fracture gap was defined as LFS (lateral fracture space) distance, and the maximum distance between the two segments of the fracture gap at the anterior and posterior margins of the fracture model was defined as PFS (posterior fracture space). The LFS and PFS distances of the human cadaveric elbow HLCF fracture models were measured during forearm rotation at 0o, 45o, 90o, and 135o rotation using a Capture Motion System (CMS), positive and lateral elbow X-ray, coronal and sagittal MRI scans, respectively, and the CMS measurements were considered as the true fracture gap distances. The values obtained by CMS, X-ray, and MRI measurements for both LPS and PFS distances in the HLCF fracture model at each position during rotation were recorded. The LFS and PFS distances were measured by two independent orthopaedic and joint imaging physicians. The data were measured three times by each physician, and the final values were the average of the two measurements. The outcomes were determined by whether a statistical difference exists in the LFS and PFS among the CMS, X-ray, and MRI groups. RESULTS The interobserver agreement tests between the two observers showed good agreement in the measurements. A multiple sample ANOVA showed statistical differences in the LFS distances of HLCF measured at 0o, 45o, 90o, and 135o rotated by three radiographic measurements (P  0.05). The same results were observed in terms of PFS values obtained by CMS, X-ray, and MRI measurements at 0o, 45o, 90o, and 135o pronation. It was statistically different among the three groups as shown by multiple sample ANOVA (P  0.05). CONCLUSION X-rays often underestimate the degree of displacement of HLCF fractures; MRI measurements are closer to the true values compared with X-ray.