Stabilizing components of the proximal radial head
The interosseous membrane (IM) is a structure complex that is comprised of a distal, central and proximal band. Together these structures contribute to the overall forearm stability. To date, the literature has focused on the axial stability rather than the transverse stability the IM supplies to the forearm. The authors set out to determine what structures were integral for providing stability when a transverse load is applied directly to the radius, such as during biceps activation. Following investigation it was shown that with pure transverse displacement the annular ligament, central and proximal band of the IM provided equal stabilizing forces whereas during rotation the central band provided the majority of the stabilizing force.
The study was divided into two components. In part one, 8 forearms were held statically in place while a transverse displacement was applied and the stabilizing components were sequentially transected. In part two, 12 forearms were cyclically pronated and supinated while optical sensors measured radial and ulnar motion. Stabilizing structures were sequentially sectioned in part two as well.
An understanding of the stabilizing forces surrounding the elbow can invaluably help guide patient education and rehabilitation following destabilizing injuries of the proximal radius. When considering transverse forces (such as biceps activation), with the forearm in a neutral position of rotation, transection of the annular ligament and central/proximal bands each had similar outcomes regarding displacement of the radius. In contrast, it was shown that during dynamic rotation transection of the central band resulted in the greatest radial displacement. Taken together, these observation help to contribute to our knowledge base regarding elbow instability (such as post-traumatic elbow dislocation). The authors pointed out that the greatest amount of radial displacement was found in max supination, and therefore stated that rehabilitation should be focussed on limited supination in post-surgical cases.
> From: Anderson et al., J Shoulder Elbow Surg (2015) (Epub ahead of print). All rights reserved to Elsevier Inc.. Click here for the Pubmed summary.