British Journal of Rheumatology 1995;34:274-282 TOPICS IN ORTHOPAEDIC SURGERY SERIES EDITORS: S. HUGHES AND M. WALPORT SURGERY TO THE WRIST JOINT

THE wrist plays a crucial role in upper limb function and dexterity. Powerful but relatively bulky forearm muscles taper to slim tendons which carry the forces to the slender, mobile finger tips. The mechanism produces an extremely effective robot arm, combining power with precision. A mobile wrist further augments dexterity, producing a wide range of dorsiflexion and palmar flexion with additional radio-ulnar deviation. The importance of pronation and supination range is often underestimated in assessment of overall upper limb dexterity. Even a small reduction in forearm rotation range will be perceived by patients as under-mining upper limb dexterity. Dorsi-palmar flexion range produces benefits in two quite separate areas. A normal range will permit the hand to be presented to objects with optimal ease with obvious benefits in overall dexterity. There are, however, quite separate benefits in a mobile wrist encapsulated in the concept of the 'tenodesis effect'. Firm grasp is automatically performed in wrist exten-sion. The wrist is stabilized by wrist flexors and exten-sors in a position of mid extension. This permits the digital flexors to function at optimal power. In a similar way digital extension is potentiated by an element of wrist flexion. The wrist acts as a fine adjustment of digital function potentiating the required effect. The desire to retain overall wrist mobility and to preserve the tenodesis effect creates a working principle which advises against operative intervention to the wrist which will cause a loss of all movement. This is not to say that arthrodesis of the wrist should not be considered in some situations. Patients regain satis-factory upper limb function following arthrodesis in terms of the ability to perform the activities of daily living, but considerable adaptation is required with some loss of dexterity