Pediatric Medial Epicondyle Fractures: A Radiographic And Cadaveric Study
Jue Cao, MD1; Brandon S. Smetana, MD1; Patrick Carry, MS. 2; Kathryn M. Peck, MD1; Gregory A Merrell, MD1
1Indiana Hand to Shoulder Center, Indianapolis, IN; 2Children's Hospital Colorado, Aurora, CO
There is considerable controversy in treatment of pediatric medial epicondyle fractures with regards to the amount of fracture displacement. The purposes of the study are three-fold; to identify the orientation of the medial elbow physis, to compare the accuracy of determining fracture displacement between axial x-rays and standard AP x-rays, and to determine the relationship between the amount of fracture displacement and loss of terminal elbow extension.
Materials & Methods:
12 Pediatric elbow CTÕs and 19 Pediatric elbow MRIÕs were analyzed for the orientation of the medial elbow physis. After determining the correct orientation of the medial physis, 15 adult cadaveric medial epicondyle fracture models were created in the correct orientation at displacements of 2mm, 5mm, 10 mm, and maximum displacement with elbow at 90 degrees of flexion. A linear mixed model regression analysis was used to compare displacement based on the axial versus the AP radiographic methods. Lateral x-rays were taken at the maximum elbow extension in each fracture model and a linear mixed model regression analysis was used to assess fracture displacement in relation to terminal elbow extension.
The medial epicondyle physis was found to be a posterior structure angled distally at 36 degree and angled posteriorly at 46 degrees. (Figure 1) At 2mm of displacement, the AP X-rays overestimated displacement relative to axial view [Mean difference: 0.38 mm, 95% CI: -0.9 to 1.7mm, p = 0.5617]. In contrast, The AP X-rays significantly underestimated displacement relative to the axial X-rays at 5mm [Mean difference: -1.6, 95% CI: -2.9 to -0.3, p=0.0142], at 10mm [Mean difference: -4.48, 95% CI: -5.8 to -3.2mm, p<0.0001] and at maximal displacement [Mean difference: -7.1, 95% CI: -8.3 to -5.8, p<0.0001]. (Figure 2) For every 5mm increase in displacement, there was a 4.71 degrees loss [95% CI: 3.64 to 5.78¡, p<0.0001] in terminal elbow extension in our cadaver models. (Figure 3)
Understanding the medial epicondyle physeal location and orientation will help clinicians to more anatomically reduce these fractures. Having an x-ray technique that better estimates the actual displacement and knowing how fracture displacement affects elbow terminal extension will provide for better delineation of fractures that could be non-operatively treated verses those that warrant operative fixation.
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