- Email: [email protected]
Non-specific arm pain
through experience and experiment, and can proceed only in the order in which events occur. If we attempt to reason backwards from the consequent (notional arm pain) to antecedent (notionally repetitive work) we allow for the possibility of a large range of antecedents without the means to distinguish the relevant from the irrelevant. Greening and colleagues’ study is flawed in other aspects, not least because no clinical syndrome has been identified a priori as a consequence of alleged “reduced movement” of the median nerve within the carpal tunnel. Furthermore, the assumption that the normal range of median nerve movement with the carpal tunnel can be established by taking the average range of movement in eight individuals without symptoms cannot be accepted as valid. Mark Awerbuch Pain Management Unit, Memorial Hospital, North Adelaide, SA 5006, Australia (e-mail:[email protected]) 1
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Littlejohn GO. Key issues in repetitive strain injury. In: Chalmers A, Littlejohn GO, Salit I, Wolfe F, eds. Fibromyalgia, chronic fatigue syndrome and repetitive strain injury. New York: Haworth Medical Press, 1995: 25–33. Greening J, Smart S, Leary R, Hall-Craggs M, O’Higgins P, Lynn B. Reduced movement of median nerve in carpal tunnel during wrist flexion in patients with non-specific arm pain. Lancet 1999; 354: 217–18. Hocking B. Epidemiological aspects of “repetition strain injury” in Telecom Australia. Med J Aust 1987; 147: 218–22. Hadler NM. Repetitive upper-extremity motions in the workplace are not hazardous. J Hand Surg 1997; 22a: 19–29. Elvey R. Brachial plexus tension tests and the pathoanatomical origin of arm pain. In: Glasgow EF, Twomey L, eds. Aspects of manipulative therapy. 2nd edn. New York: Churchill Livingstone, 1985: 116–22.
Authors’ reply Sir—We do not ask the reader to assume that NSAP is RSI, as Mark Awerbuch suggests. The term NSAP and its diagnostic criteria were formed by a consensus opinion of musculoskeletal experts in the UK to identify the upper limb pain syndrome previously referred to as RSI.1 We disagree that RSI does not appear in any taxonomy of medical disorders, and we refer Awerbuch to a major textbook on disorders of peripheral n e r v e s . 2 The term NSAP 1 is used precisely to avoid the implication of occupation-related injury. However, patients with NSAP are commonly found in occupations that involve repetitive hand activities, as shown in our patients.3
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Diagnosis was not based just on selfreported symptoms and the upper limb tension test (ULTT1). This test (not two tests), which was designed to assess brachial and median nerve gliding in the upper limb, was used in addition to the diagnostic criteria referred to above. ULTT1 (see Butler4) is not the brachial plexus tension test cited by Awerbuch. Despite being “invented by a physiotherapist”, ULTT1 is used by physicians as well as physiotherapists. In our study, only the NSAP group showed painfully restricted movement with ULTT1. Apart from one patient, the wrist that showed the most severe restriction of median nerve movement with magnetic resonance imaging corresponded to the upper limb with the most restricted range of movement during ULTT1. This finding suggests that ULTT1 would be a useful addition to the clinical examination of these patients. Awerbuch makes the point that testing validation of cause comes from survival of an idea through experience and experiment. We agree; our clinical experience with these patients suggested our experimental questions, the results of which are published in peer-reviewed journals. We are indeed trying to distinguish the relevant from the irrelevant by providing objective diagnostic criteria for NSAP. We did not set out to establish a “normal range” of movement for the median nerve at the carpal tunnel. We have, however, established a highly significant difference in nerve movement between one group of individuals without symptoms and a group of typical NSAP patients. Finally, as pointed out by Hutson,5 “to suppress recognition of the condition [RSI] and therefore its assessment and appropriate management, represents medical omnipotence based largely on diagnostic incompetence.” Let us stop procrastinating about NSAP and turn our attention instead to identifying its cause and pathogenesis so that we can reduce its incidence and use treatment techniques based on evaluated outcomes. *Jane Greening, Bruce Lynn, on behalf of the investigators Department of Physiology, University of Greater London, London WC1E 6BT, UK (e-mail: [email protected]) 1
Harrington JM, Carter JT, Birrell L, Gompertz D. Surveillance case definition for work related upper limb pain syndromes. Occup Environ Med 1998; 55: 264–71. 2 Birch R, Bonney G, Wynn Parry CB, eds. Surgical disorders of the peripheral nerves. New York: Churchill Livingstone, 1998. 3 Novak CB, Mackinnon SE. Repetitive use
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and static postures: a source of nerve compression and pain. J Hand Ther 1997; 10: 151–59. Butler D. Mobilisation of the nervous system. New York: Churchill Livingstone, 1991. Hutson M. Repetitive strain injury...that is misunderstood and misdiagnosed. BMJ 1994; 308: 269.
Sir—Jane Greening and colleagues 1 record the observation that movement of the median nerve, during wrist flexion, was reduced in patients with NSAP. The technique they used to visualise the nerve involved an openaccess magnetic resonance scanner. Unfortunately, there are only about ten of these scanners in the UK. Consequently, there would seem to be little likelihood that this technique will be possible for the population as a whole, especially for a condition which has such a high incidence as NSAP. Ultrasonography represents a much more widely available alternative. Peripheral nerves have been successfully studied with this technique2 and current equipment is well suited for the purpose of median nerve observation. An advantage of ultrasound imaging is that the images are displayed in real-time, which means that the identity of many anatomical components can be verified by the simple expedient of causing the patient to move part of their hand and observing corresponding movements in the image. In the area of the carpal tunnel, the median nerve is located anterior to the flexor pollicis longus, lateral to the flexor digitorum superficialis, and deep to the flexor retinacalum. These three structures can be made to move independently of each other by appropriate individual flexing of the thumb, fingers, and palm. Direct feedback of this nature to confirm the moveable anatomical structures increases the confidence with which the image can be analysed and non-moving features identified. With a mid-cost scanner we have successfully imaged the median nerve in the region of the carpal tunnel in a group of ten healthy volunteers, aged 22–54 years. We found that the median nerve was successfully identified in all cases (20 wrists).* Its appearance was of an echo-poor elliptical or circular feature between the strongly echogenic flexor pollicis longus and the somewhat less echogenic flexor digitorum superficialis. As Greening and colleagues described, the position, shape, and dimensions of the median varied *Images available from the authors, on request.
THE LANCET • Vol 354 • October 30, 1999
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Littlejohn GO. Key issues in repetitive strain injury. In: Chalmers A, Littlejohn GO, Salit I, Wolfe F, eds. Fibromyalgia, chronic fatigue syndrome and repetitive strain injury. New York: Haworth Medical Press, 1995: 25–33. Greening J, Smart S, Leary R, Hall-Craggs M, O’Higgins P, Lynn B. Reduced movement of median nerve in carpal tunnel during wrist flexion in patients with non-specific arm pain. Lancet 1999; 354: 217–18. Hocking B. Epidemiological aspects of “repetition strain injury” in Telecom Australia. Med J Aust 1987; 147: 218–22. Hadler NM. Repetitive upper-extremity motions in the workplace are not hazardous. J Hand Surg 1997; 22a: 19–29. Elvey R. Brachial plexus tension tests and the pathoanatomical origin of arm pain. In: Glasgow EF, Twomey L, eds. Aspects of manipulative therapy. 2nd edn. New York: Churchill Livingstone, 1985: 116–22.
Authors’ reply Sir—We do not ask the reader to assume that NSAP is RSI, as Mark Awerbuch suggests. The term NSAP and its diagnostic criteria were formed by a consensus opinion of musculoskeletal experts in the UK to identify the upper limb pain syndrome previously referred to as RSI.1 We disagree that RSI does not appear in any taxonomy of medical disorders, and we refer Awerbuch to a major textbook on disorders of peripheral n e r v e s . 2 The term NSAP 1 is used precisely to avoid the implication of occupation-related injury. However, patients with NSAP are commonly found in occupations that involve repetitive hand activities, as shown in our patients.3
1558
Diagnosis was not based just on selfreported symptoms and the upper limb tension test (ULTT1). This test (not two tests), which was designed to assess brachial and median nerve gliding in the upper limb, was used in addition to the diagnostic criteria referred to above. ULTT1 (see Butler4) is not the brachial plexus tension test cited by Awerbuch. Despite being “invented by a physiotherapist”, ULTT1 is used by physicians as well as physiotherapists. In our study, only the NSAP group showed painfully restricted movement with ULTT1. Apart from one patient, the wrist that showed the most severe restriction of median nerve movement with magnetic resonance imaging corresponded to the upper limb with the most restricted range of movement during ULTT1. This finding suggests that ULTT1 would be a useful addition to the clinical examination of these patients. Awerbuch makes the point that testing validation of cause comes from survival of an idea through experience and experiment. We agree; our clinical experience with these patients suggested our experimental questions, the results of which are published in peer-reviewed journals. We are indeed trying to distinguish the relevant from the irrelevant by providing objective diagnostic criteria for NSAP. We did not set out to establish a “normal range” of movement for the median nerve at the carpal tunnel. We have, however, established a highly significant difference in nerve movement between one group of individuals without symptoms and a group of typical NSAP patients. Finally, as pointed out by Hutson,5 “to suppress recognition of the condition [RSI] and therefore its assessment and appropriate management, represents medical omnipotence based largely on diagnostic incompetence.” Let us stop procrastinating about NSAP and turn our attention instead to identifying its cause and pathogenesis so that we can reduce its incidence and use treatment techniques based on evaluated outcomes. *Jane Greening, Bruce Lynn, on behalf of the investigators Department of Physiology, University of Greater London, London WC1E 6BT, UK (e-mail: [email protected]) 1
Harrington JM, Carter JT, Birrell L, Gompertz D. Surveillance case definition for work related upper limb pain syndromes. Occup Environ Med 1998; 55: 264–71. 2 Birch R, Bonney G, Wynn Parry CB, eds. Surgical disorders of the peripheral nerves. New York: Churchill Livingstone, 1998. 3 Novak CB, Mackinnon SE. Repetitive use
4
5
and static postures: a source of nerve compression and pain. J Hand Ther 1997; 10: 151–59. Butler D. Mobilisation of the nervous system. New York: Churchill Livingstone, 1991. Hutson M. Repetitive strain injury...that is misunderstood and misdiagnosed. BMJ 1994; 308: 269.
Sir—Jane Greening and colleagues 1 record the observation that movement of the median nerve, during wrist flexion, was reduced in patients with NSAP. The technique they used to visualise the nerve involved an openaccess magnetic resonance scanner. Unfortunately, there are only about ten of these scanners in the UK. Consequently, there would seem to be little likelihood that this technique will be possible for the population as a whole, especially for a condition which has such a high incidence as NSAP. Ultrasonography represents a much more widely available alternative. Peripheral nerves have been successfully studied with this technique2 and current equipment is well suited for the purpose of median nerve observation. An advantage of ultrasound imaging is that the images are displayed in real-time, which means that the identity of many anatomical components can be verified by the simple expedient of causing the patient to move part of their hand and observing corresponding movements in the image. In the area of the carpal tunnel, the median nerve is located anterior to the flexor pollicis longus, lateral to the flexor digitorum superficialis, and deep to the flexor retinacalum. These three structures can be made to move independently of each other by appropriate individual flexing of the thumb, fingers, and palm. Direct feedback of this nature to confirm the moveable anatomical structures increases the confidence with which the image can be analysed and non-moving features identified. With a mid-cost scanner we have successfully imaged the median nerve in the region of the carpal tunnel in a group of ten healthy volunteers, aged 22–54 years. We found that the median nerve was successfully identified in all cases (20 wrists).* Its appearance was of an echo-poor elliptical or circular feature between the strongly echogenic flexor pollicis longus and the somewhat less echogenic flexor digitorum superficialis. As Greening and colleagues described, the position, shape, and dimensions of the median varied *Images available from the authors, on request.
THE LANCET • Vol 354 • October 30, 1999