Abstract
PurposeDetermining the magnitude of displacement in pediatric lateral humeral condyle fractures can be difficult. The purpose of this study was to (1) assess the effect of forearm rotation on true fracture displacement using a cadaver model and to (2) determine the accuracy of radiographic measurements of the fracture gap.MethodsA non-displaced fracture was created in three human cadaveric arms. The specimens were mounted on a custom apparatus allowing forearm rotation with the humerus fixed. First, the effect of pure rotation on fracture displacement was simulated by rotating the forearm from supination to pronation about the central axis of the forearm, to isolate the effects of muscle pull. Then, the clinical condition of obtaining a lateral oblique radiograph was simulated by rotating the forearm about the medial aspect of the forearm. Fracture displacements were measured using a motion-capture system (true-displacement) and clinical radiographs (apparent-displacement).ResultsDuring pure rotation of the forearm, there were no significant differences in fracture displacement between supination and pronation, with changes in displacement of <1.0 mm. During rotation about the medial aspect of the forearm, there was a significant difference in true displacements between supination and pronation at the posterior edge (p < 0.05).ConclusionOverall, true fracture displacement measurements were larger than apparent radiographic displacement measurements, with differences from 1.6 to 6.0 mm, suggesting that the current clinical methods may not be sensitive enough to detect a displacement of 2.0 mm, especially when positioning the upper extremity for an internal oblique lateral radiograph.Electronic supplementary materialThe online version of this article (doi:10.1007/s11832-014-0553-8) contains supplementary material, which is available to authorized users.
Highlights
Fracture of the lateral humeral condyle is the second most common elbow fracture in children [12, 17], reported to represent 12–20 % of pediatric elbow fractures [11, 19, 22] with an estimated annual incidence of 1.6 per 1,000 individuals [11]
We evaluated the effect of rotation around the central axis of the forearm, and rotation around the medial edge of the forearm on displacement of a simulated lateral humeral condyle fracture using an adult cadaver model
Rotation around the central axis of the forearm isolated the effect of pull of the lateral collateral ligament and the muscles attached to the fracture fragment, while rotation around the medial edge of the forearm simulated positioning of the extremity used in the emergency room to obtain a lateral oblique radiograph
Summary
Fracture of the lateral humeral condyle is the second most common elbow fracture in children [12, 17], reported to represent 12–20 % of pediatric elbow fractures [11, 19, 22] with an estimated annual incidence of 1.6 per 1,000 individuals [11]. Surgical treatment is recommended for fractures displaced more than 2 mm, either by closed reduction and percutaneous pinning [23] or open reduction and. Some authors have suggested ultrasound, magnetic resonance imaging (MRI), arthrography, or multidetector computed tomography (CT) [5, 15, 18, 21, 27, 28] Many of these methods involve greater expense, time, radiation exposure, painful examinations, or even sedation [26]. Initial displacement assessment is often determined using plain radiographs. Several criteria have been recommended to predict the stability of minimally-displaced lateral condyle fractures using the standard radiographs [3]; despite adherence to these guidelines, fractures showing minimal displacement on initial radiographs may still displace further. Subsequent displacement while in a cast may lead to delayed union or non-union requiring operative treatment [2, 8, 9, 11, 13, 20]
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