This study outlined the development of an injury model to correlate forearm position in association with elbow injuries. Twenty cadaveric arms were placed in an impact-testing apparatus. The arm was disarticulated at the wrist with the elbow maintained in full extension with a 27 kg mass used to impact against the disarticulated distal radius in varying degrees of forearm rotation measured from the starting point of full supination. A trend was noted that in full supination there were no radial head fractures but there was a proximal radial shaft fracture and a distal ulnar fracture. In more neutral positions, a marginal radial head fracture was encountered with a lesser incidence of interosseous membrane injuries and a 30% contact area at the radiocapitellar joint. In relative pronation, the radial head sustained greater comminuted fractures, exhibited a higher average percent of contact of the radiocapitellar joint of 54% and had an increased incidence of interosseous membrane injuries.
This model appears to correlate with many long held tenants of the effect of forearm rotation on ultimate injuries including that of radial head fractures and Essex-Lopresti injuries. The influence of muscle tension and body dynamics during a fall on an outstretched hand, however, are not included in the model. In addition, there was much variability in the maximum amount of forearm rotation within the specimens ranging from 80 to 130 degrees of rotation and the authors did not clearly establish neutral forearm rotation in these specimens which made the interpretation of the data difficult to follow. This model may, however, be broadened to study more complex injury patterns with the hope to further understand their mechanism of injury and ultimately lead to more sound treatment.
J of Bone and Joint Surgery