Repetitive strain injury

Repetitive strain injury (RSI) is one of a variety of names for a group of musculo-skeletal and tendinous injuries the majority of which are found in the upper limb, the shoulder girdle, and the neck. In industry these conditions tend to be the result of repetitive motion at joints, often to extremes of movement, and under load, or by a requirement to maintain constrained or awkward postures. Pathologically similar conditions can occur not infrequently in association with osteoarthritis, pregnancy, and in post-menopausal women. In such cases, of course, the spontaneously occurring condition is aggravated by overuse. Terminology and pathology RSI is also known as Repetition Injury and as Cumulative Trauma Disorder (CTD). To understand the pathogenesis of the conditions it should be recognized that, as noted before, muscles take origin in a bone, pass across a joint and terminate in a tendon which is inserted into another bone. Some tendons, notably those around the wrist, are encased in a smooth lubricating sheath through which they run. This sheath is known as the synovial sheath. At the base of the wrist, on the palmar surface, the tendons to the fingers are held together in a ligamentous tunnel called the carpal tunnel which prevents them from splaying out on contraction of the flexor muscles of the forearm. Also passing thorugh this tunnel are small blood vessels, and fibres of the m edian nerve which provides nerve supply to the thumb, the first and second finger, and half of the third finger.The joints themselves are lined with a lubricating membrane called the synovial m em brane. Other anatomincal elements involved are the muscles and their attachments to bone. In particular, there are muscles responsible for pronation, or inward turning of the forearm, and supination, or outward turning of the forearm, which attach to protuberances on the outer corners

of the humerus bone at the elbow, known as the m edial and lateral epicondyles, respectively. Of interest also are the protective cushions or bursae, found in the shoulder joint, and elsewhere. Inflammation, with pain, swelling, and tenderness can occur in any of these structures, and although the resulting conditions.are fundamentally the same, each condition goes by a different name according to anatomical site. The suffix, . . . itis, describes inflammation, and thus, for example, RSI can occur as tendinitis when the inflammation is in a tendon, synovitis when it is in a synovial membrane, tenosynovitis when it is in the tendon and tendon sheat, epicondylitis when it affects the epicondyles and bursitis when it affects a bursa. A separate but related condition is carpal tunnel syndrom e, which occurs by reason of swelling of structures in the carpal tunnel.While these various conditions can be recognized clinically, they can occur when there is little or no obvious pathology. Indeed, McDermot (1986), in a comprehensive review, states: The term repetition strain injury is unsatisfactory. First it implies that an injury has been caused by repetitive movement. However, the problem in many workers with RSI is induced by a static muscle load, for example among those who develop pain in the shoulders and arms after maintaining their upper extremities in the raised position that is necessary for their working activities. Secondly, the term “strain” implies a pathogenesis for RSI which is by no means certain. Thirdly, there is often no apparent injury present and there may be no discernible abnormality on clinical examination.’ Accordingly, still another term, namely overuse injury, with no connotation of either repetition or strain, has come into usage. A corollary deriving from this viewpoint is that all forms of this type of injury, whether they be tenosynovitis, epicondylitis, carpal tunnel syndrome, occupational cervico-brachial syndrome, or whatever, arise from the same origin, namely overuse, and that the terminological subdivisions merely define the site or sites, and that what we are dealing within RSI, or whatever other name, is not a multiplicity of conditions but different aspects of the same condition. Some of the more common aspects are enlarged on below. Tenosynovitis Tenosynovitis is a general name given to an affliction that affects tendons and their sheaths at the wrist. The term is often misused to apply to other forms of overuse injury around the wrist, even carpal tunnel syndrome. It occurs as a dull ache, worsened by movement of the tendons concerned. There may be, in established cases, some swelling over the area, and when the wrist or fingers are moved a rasping sensation may even be felt. There is commonly weakness of the muscles involved.With continued exposure the condition will worsen, and cause increased

weakness and pain. There may be extension to other related tendons. Ultimately, if the worker persists, there could be permanent disability. If the worker is removed from the causative task however, before permanent damage is done, the condition will recover. Specialized medical treatment may nevertheless be required, and gradual rehabilitation is essential before return to full activity.