The Forearm Joint
The forearm is composed of the radial and ulnar shafts, which are linked by the interosseous membrane and intercalated between the elbow and wrist. The forearm ensures pronation/supination and longitudinal load transfer. The radius and ulna are connected
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Introduction The forearm has three main functions: to allow prono-supination and therefore appropriate hand positioning, to transfer longitudinal loads between the wrist and the elbow, and to serve as an attachment site for the muscles that move the wrist and fingers. The forearm is made of two bones, the radius and the ulna, which are joined at the proximal and distal radio-ulnar joints (PRUJ and DRUJ, respectively). Both joints are located at the ends of the forearm and are therefore often considered either part of the elbow (PRUJ) or wrist (DRUJ). The largest part of the forearm, between the DRUJ and PRUJ, is composed of the radial and ulnar shafts linked by the interosseous membrane (IOM) and is classically viewed as a transition segment between the elbow and wrist. However anatomical works and biomechanical studies have shown that both the PRUJ and DRUJ are not independent of the forearm and cannot function if the forearm is either locked, unstable or destroyed and we introduced the “three locker” concept in 2007 [60]. This also had led some authors to consider the radial and ulnar shafts C. Dumontier () Department of Hand and Plastic Surgery, Hôpital St Roch, 5 rue Pierre Devoluy, BP 1319, 06006 Nice, France e-mail: [email protected] M. Soubeyrand Service de Chirurgie Orthopédique, Hôpital du Kremlin-Bicêtre, 78 rue du général Leclerc, 94275 Le Kremlin-Bicêtre, France
linked by the IOM as an authentic joint, just as are the scapulo-thoracic junction or subacromial space. Because this joint is intercalated between the PRUJ and DRUJ, an appropriate designation is ‘middle radio-ulnar joint’ (MRUJ), as suggested by LaStayo and Lee [27]. Comparison of species have shown that the forearm joint (zeugopodium) has evolve differently among mammalian species and is part of the evolution of primates for whom prono-supination was useful to live in trees [61]. Most of the muscles involved in prono-supination (i.e., pronator teres, brachial biceps, and supinator) insert at the MRUJ. Studies focussed on the IOM (and therefore the MRUJ) establish that the IOM is not merely a fibrous band filling the interosseous space, but instead a multicomponent ligamentous structure that has a complex behaviour and plays an essential role in forearm stability and physiology [2]. This also suggests that the conventional description of the forearm as a simple segment intercalated between the wrist and the elbow may be outdated and that a more relevant concept may be that of a tri-articular complex in which the MRUJ plays a crucial role [12, 16, 17]. Therefore it seems appropriate to describe the forearm unit as the “forearm joint” to better understand its pathology.
Anatomy and Biomechanics Both the PRUJ and DRUJ have been widely described and are well known. The stability of the PRUJ is achieved by the annular ligament
G. Bentley (ed.), European Instructional Lectures, European Instructional Lectures 13, DOI 10.1007/978-3-642-36149-4_14, © EFORT 2013
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Fig. 1 Three-quar
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