276. RELEASE OF THE INTEROSSEOUS MEMBRANE IN ROTATIONAL MALUNION OF THE RADIAL SHAFT: IMPACT ON PRONOSUPINATION

Abstract

Purpose of the study: The slightest alteration of the antebrachial anatomic configuration, which constitutes a complex and precise biomechanical system, yields a limitation in pronosupination. Unlike the metaphysical region, little is known about rotational malunion involving the radial shaft. Kasten et all demonstrated in 30 cases that a rotational malunion of the radial shaft leads to significant loss in the pronosupination arc. If the proximal and distal radioulnar joints are intact, the interosseous membrane (IOM) probably plays an important role in this limitation.

Material and methods: The purpose of our study was to evaluate the impact of releasing the IOM on the pro-nosupination arc in an experimental model with a rotational malunion of the radial shaft inducing pronation.

Results: The study involved eight cadaver forearms free of all muscle structures and devoid of prior trauma. After stabilizing the elbow at 90°, the upper limb was fixed on a metal frame used as the reference to measure pronosupination. For each specimen, motion was measured initially, after osteotomy of the radius shaft to induce pronation then associated with longitudinal section of the IOM. A midshaft transverse osteotomy induced 78±7 pronation on average and was fixed with a DCP.

Discussion: The mean pronosupination arc was initially 175 in our population (81 pronation, 94 supination). After the creating the rotational malunion, this arc decreased significantly to 126 (SD. p> 0.05) (99 pronation, 27 supination). Release of the IOM increased this arc significantly from 27 to 153 (SD, p> 0.05) (105 pronation, 48supination)

Conclusion: Our study confirms the impact of rotational malunion on the pronosupination arc and shows the positive effect of releasing the IOM. Suppression of the IOM leads to a simpler biomechanics for the antebrachial system, allowing greater mobility of the bone one over the other. There are several clinical applications of this observation for the correction of shaft malunion of the antebrachial bones, but also certain corrective osteotomies for malpositions in the neurological patient.