David McFarlane put a query to an email discussion list about the diagnosis and treatment of upper limb overuse syndromes.

He collated and summarised the replies he received, and emailed this summary to the list. I am presenting this here, with his agreement, as an information source. It is NOT meant to be a comprehensive review of the subject!  

David wrote: Many thanks to all of you who supplied me with information on the diagnosis and treatment of hand/arm overuse syndromes. By way of a small Christmas present I have summarised the picture that emerged from the references that you gave me:-

Most overuse injuries associated with sporting activities and physical work are caused by repetitive eccentric muscle contractions (Hutson, 1997, page 40). By contrast most overuse problems reported by sedentary workers and other workers who have to work in constrained postures are associated with sustained isometric contractions.

Constrained work postures can cause either physiological pain or pathological pain (Hutson, 1997, page 44). Physiological pain is localised and proportional to the cause usually occurring immediately after the cause (the original irritative stimulus) and is typically transient or temporary. This type of pain is often found in the initial stages of overuse injuries. These are sometimes called "type 1"work-related upper limb disorders (type I WRULDs).

In the case of Carpal Tunnel Syndrome (CTS) there may also be clumsiness with buttons due to hypoaesthesia (Hutson, 1997, page 80). If the sufferer feels the need to let the affected arm hang out of the bed the cause is almost certainly Carpal Tunnel Syndrome. This condition is usually found amongst meat-packers, check-out clerks and assembly workers (Hutson, 1997, page 77) unless it is due to systemic causes such as hypothyroidism, rheumatoid arthritis, peripheral neuritis or alcoholism (Hutson, 1997, page 80). Consequently cases of CTS cases amongst office workers are often not solely due to work-related causes.

Neuropathic pain (pathological pain) is chronic and persists after the original cause. Pathological pain is often caused by substances called prostanoids that are released by inflammation processes (Samad, Moore, Sapirstein, Billet, Allchorne, Poole, Bonventre and Woolf, 2001).

Work-related neuropathic pain in the arms is usually diffuse and widespread. It tends to persist after the original cause. It is characterised by excessive sensitivity to pain known as "hyperalgesia" (Hutson, 1997, page 13) and a lowered pain threshold (Hutson, 1997, page 45). This type of pain is often found in the final stages of overuse injuries. These are sometimes called "type 2 work-related upper limb disorders". These syndromes are characterised by pain that is often described as burning, throbbing, stabbing or aching (Hutson, 1997, page 108) and a characteristically limp handshake (Hutson, 1997, page 109). Sufferers sometimes report a sensation of swelling in a body area where no swelling is visible. In some cases the patients have cold, swollen, blue hands (Hutson, 1997, page 110) Tricyclic antidepressant drugs can often be useful for treating these but improvements are usually seen only after prolonged treatment (Hutson, 1997, page 115).

These pain syndromes are sometimes found in patients who had a pre-existing depression neurosis but medical texts (such as Hutson) seem to imply that these drugs are effective for pain relief whatever the aetiology of the pain. Compensation appears to adversely affect the efficacy of treatment of these pain syndromes (Joyce, 1989 as quoted in Hutson, 1997, page 115).

Early treatment is advisable as these conditions are reversible during the early stages (Hutson, 1997, page 112). Conventional therapy techniques are rarely effective (Hutson, 1997, page 113). Useful forms of treatment include TENS, acupuncture, acupressure and trigger point therapy (massage, stretching or rest) (Hutson, 1997, page 113). However, the most effective therapy are neural mobilization techniques (in which neural tissues are moved, either by movement relative to their surroundings or by tension development) and neural blocks (Hutson, 1997, page 115).

Prolonged muscle use where muscle contraction reaches 20% of the maximum contraction is believed to be a risk factor (Karlsson and Olander, 1972 as quoted in Hutson, 1997, page 106). This typically occurs in tasks where the arms have to be held in fixed postures for prolonged periods until they are fatigued. Some researchers have postulated that chronic pain in the arms might be due to abnormal nerve functioning caused by mechanical tension on the nerves and other neural structures (Quintner and Elvey, 1993).

Most sufferers of neuropathic pain exhibit allodynia i.e. a painful response to a normally non-painful stimulus (Hutson, 1997, page 110). There are three types of allodynia. a) thermal, b) chemical, and c) mechanical (Kim and Chung, 1995). These can easily be tested by the Hendler Alcohol Drop and Swipe Test (Hendler, 1995). In this test, a physician squeezes an alcohol swab so that a drop of alcohol lands on the patient's affected area. If the patient immediately withdraws the limb and complains of a burning pain, the physician has demonstrated thermal allodynia, i.e. a painful response to the cooling effects of a drop of alcohol on a limb. After two minutes, if there has been no response to the thermal test, a patient may begin to experience burning pain in the affected limb. This occurs as the fat soluble alcohol permeates the skin and begins to chemically irritate the hypersensitive C fibers, which conduct the message of pain. If the patient then experiences pain, this demonstrates chemical allodynia. Then, with the leftover alcohol swab, the physician gently strokes the affected area. If this produces pain, this clearly demonstrates mechanical allodynia.

The design of workplaces, workplace equipment and work practices should be optimised. Failure to deal with these issues is a common feature of many of many overuse syndromes (such as tendinitis, epicondylitis and carpal tunnel syndrome) that are characterised by physiological pain (Armstrong and Ulin, 1995 in Hunter, Mackin and Callahan, 1995).

In conditions caused by eccentric muscle contractions (typically those reported by workers who do heavy physical work) sore muscles are commonly reported. There is evidence that strong eccentric contractions of muscles can damage the muscle fibres (Friden, Sjostrom and Ekblom, 1981 as quoted in Kuorinka and Forcier, 1995). This type of damage is reversible if the sufferer is permitted sufficient rest for recovery (Kuorinka and Forcier, 1995). The symptoms of these conditions often include burning, tingling and numbness (Hutson, 1997, page 79). Early diagnosis is also helpful.

Many overuse syndromes are caused by degradation of the tissues rather than inflammation. Hence, it makes no sense to delay the diagnosis until inflammation is detected (Hutson, 1997, page 65). In particular diagnosis should not be delayed until a physical dysfunction becomes apparent (Hutson, 1997, page 78). Unfortunately, Some medical tests for these syndromes (such as Tinel's test) are of limited value due to their lack of sensitivity and specificity (Hutson, 1997, page 80).

Physiological pain syndromes can be effectively treated by steroid injections and resting the affected area from the physical stresses that are causing it (Hutson, 1997, page 66). Joint immobilisation techniques (such as wrist splinting) should not be used to protect soft tissues. Some of these syndromes (such as carpal tunnel syndrome) will resolve completely with adequate rest (Hutson, 1997, page 73). Rest from the activity that causes physical stresses is useful for promoting healing. This is illustrated by the fact that rotator cuff syndromes caused by leisure activities have a better prognosis than work related cases (Hutson, 1997, page 95).      

References.

1. M.Hutson, (1997), "Work-Related Upper Limb Disorders: Recognition and Management", (Butterworth-Heinemann; Oxford).

2. T. Samad, K Moore, A. Sapirstein, S. Billet, A. Allchorne, S. Poole, J. Bonventre and C. Woolf, (2001), "Interleukin-1beta-mediated induction of Cox-2 in the CNS contributes to inflammatory pain hypersensitivity", Nature 2001 Mar 22;410(6827):471-5.

3. Quintner and R. Elvey, (1993), "Understanding "RSI": a review of the role peripheral neural pain and hyperalgesia, J. Manual Manipulative Therapy, 1 (3), 99-105.

4. J. Williams, (1987), "The failure of the "RSI" concept", Medical Journal of Australia, no. 147, pages 233-236.

5. J. Karlsson and B. Olander, (1972), "Muscle metabolites with exhaustive static exercise of different durations", Acta Physiol Scand, no. 86, pages 309-314.

6. S. Kim, and J. Chung, (1995), "Sympathectomy alleviates mechanical allodynia in an experimental animal model for neuropathy in the rat", Neuroscience Letter 134 (1995) , 131 - 134.

7. N. Hendler, (1995), Reflex sympathetic dystrophy: clearing up the misconceptions, J. of Workers Comp., vol. 5, no. 1, pp. 9-20, 1995.

8. T. Armstrong and S. Ulin, (1995), "Analysis and design of jobs for control of work-related upper limb disorders", Chapter 103 of "Rehabilitation of the hand: surgery and therapy", edited by M. Hunter, E. Mackin and A. Callahan, (Mosby; St. Louis).

9. J. Friden, M. Sjostrom and D. Ekblom, (1981), "A morphological study on delayed muscle soreness", Exp, 37, pages 506 -507.

10. I. Kuorinka and L. Forcier (editors), (1995), "Work related musculoskeletal disorders (WMSDs): a reference book for prevention", (Taylor and Francis; London).