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© 1996 The Journal of Bone and Joint Surgery, Inc. Carpal Instability in the Weight-Bearing Upper Extremity*   , CLEVELAND, OHIOInvestigation performed at the Department of Orthopaedic Surgery, Case Western Reserve University and University Hospitals of Cleveland; The MetroHealth Medical Center Rehabilitation Service; and the Spinal Cord Injury Unit of the Wade Park Veterans Administration Medical Center, Cleveland
The prevalence of carpal instability in a paraplegic population was investigated to establish an association between chronic repetitive stress on the wrist and the development of such instability. Nine of 162 paraplegic patients had static carpal instability and no history of an acute injury of the wrist. The predominant pattern of instability, found in eleven wrists (six patients), was non-dissociative volar intercalated segmental instability. The prevalence of carpal instability increased with the duration of weight-bearing on the upper extremity. Eighteen per cent of the patients in whom the spinal cord injury had occurred more than twenty years before the study had carpal instability. Carpal instability in these weight-bearing upper extremities and the increase in its prevalence with the duration of the forces across the wrist demonstrate an association between chronic repetitive stress on the wrist and carpal instability.
Patients who have a spinal cord injury place an inordinate amount of weight-bearing stress on the upper extremities. Impairment and disability of the upper extremity as a result of these forces has only recently been investigated. Gellman et al. introduced the term weight-bearing upper extremity while studying disabilities of the upper extremity in patients who had a spinal cord injury8. An increased prevalence of shoulder impingement, tears of the rotator cuff, and carpal tunnel syndrome has been demonstrated in these patients2,4,8,9,32. Repetitive forces placed through weight-bearing upper extremities while they are held in an abnormal posture were proposed as the cause of these disabilities2,4,8,9. Since its initial description by Gilford et al.10, carpal instability has been related to a preceding acute traumatic injury of the wrist. In early series, carpal instability was frequently associated with a history of a fall onto the outstretched hand with the wrist extended and the forearm supinated6,22. Mayfield et al. demonstrated disruption of the intercarpal ligaments and carpal instability after acute loading of the extended and supinated wrist in a cadaveric model25. However, there have been several anecdotal reports of carpal instability without a preceding acute injury of the wrist20-22, and we have seen patients with such instability in our clinical practice. We know of a single case report in which a history of chronic stress on the wrist, rather than an acute traumatic injury, may have led to carpal instability5, but we are not aware of any studies demonstrating an association between chronic repetitive stress and carpal instability. Paraplegic patients transfer, propel a wheelchair, and unweight the sacrum with the upper extremity adducted against the body, the wrist in maximum extension, and the forearm in supination8. It has been proposed that these actions place the arm in the same position in which a traumatic event produces carpal instability3,6,14,18,22,25,28,29,35. In the absence of an isolated traumatic event, chronic repetitive loading of the ligaments of the wrist may lead to carpal instability. The purpose of this investigation was to determine if the chronic repetitive forces placed through the wrists of patients who have a spinal cord injury are associated with carpal instability.
Only paraplegic patients were included in this study. Although high-functioning quadriplegic patients incur similar forces through the upper extremities, they were excluded in order to eliminate neurological deficits in the upper extremity as a variable in the development of carpal instability. Similarly, patients who had a history of cervical radiculopathy or spondylotic myelopathy were also excluded from the study. The inclusion criteria were designed to establish a homogeneous population with similar requirements for the upper extremities. Only patients who used a manual wheelchair and who could transfer independently were included in the study population; therefore, patients with incomplete paraplegia who were able to walk with crutches or a cane and patients who were restricted to a motorized wheelchair or to bed rest were excluded. In order to eliminate symptoms secondary to new forces across the wrist while the patient was adapting to a recent spinal cord injury26, the injury had to have occurred more than two years before the start of the study. Any patient who had systemic disease, such as rheumatoid arthritis or a connective-tissue disorder, was excluded from the study because of the possibility of being predisposed to rupture of the carpal ligament with the development of carpal instability. Finally, any patient who had a history of a traumatic injury of the upper extremity was excluded. A screening questionnaire was sent by mail to 281 paraplegic patients who were being actively followed at our spinal cord injury center. The questionnaire asked whether the patient had daily pain in the wrist or hand; it also determined the patient's current level of activity and if there was a history of traumatic injury of the upper extremity. Two hundred and forty-six patients returned the questionnaire, for an 88 per cent response rate. Data from the questionnaires were used to identify a study population of 162 paraplegic patients who met the inclusion criteria. Of the seventy patients in this population who indicated that they had daily pain in the wrist or hand, sixty-two (89 per cent) were available for evaluation. In addition to a complete history of symptoms related to the upper extremities, the clinical data included the dominant hand, whether the symptoms were unilateral or bilateral, the duration and intensity of the symptoms, and the association of the symptoms with or their limitation of daily activities. The patient was also asked if either wrist cracked, popped, or clunked during motion. The level of the spinal cord injury, the date on which it occurred, and the age of the patient at the time of the injury were confirmed. A complete physical evaluation of each upper extremity was performed; it included measurement of the range of motion of the shoulder, elbow, wrist, and hand; manual muscle-testing; and neurological testing. The wrist was examined for clinical features specific to carpal instability, including point tenderness over the wrist, instability of the scaphoid as described by Watson and Ballet34, and mid-carpal instability as described by Lichtman et al.20. To perform the latter test, the examiner holds the right wrist (in his or her right hand) in the neutral position and directs pressure onto the dorsum of the wrist at the level of the distal end of the capitate with his or her thumb. The wrist is then both axially loaded and ulnarly deviated. A painful clunk with ulnar deviation signifies a positive test, and it has been argued that this represents either mid-carpal instability20 or lunotriquetral instability15. Lateral radiographs were made with the wrist in neutral, flexion, extension, and the clenched-fist position, and anteroposterior radiographs were made with the wrist in neutral, radial deviation, ulnar deviation, and the clenched-fist position. The radiographs were evaluated for evidence of carpal instability with use of the criteria established by Gilula et al.11-13. As will be described, the carpal instability was classified with use of three terms to describe each pattern of instability as either dorsal or volar intercalated segmental, either dissociative or non-dissociative, and either static or dynamic. First, the lateral radiographs were reviewed for evidence of abnormal orientation of the scaphoid and lunate with respect to each other and to the distal aspect of the radius. The scapholunate, radiolunate, radioscaphoid, and lunocapitate angles were measured with the techniques proposed by Larsen et al.7,19 (Fig. 1), which have been shown to minimize both intraobserver and interobserver variability. The criteria for carpal instability, as determined by Gilula et al.11-13, were used to evaluate the radiographic data and to classify the instability. If the lunate was extended posteriorly more than 15 degrees on the lateral radiograph made with the wrist in neutral, the deformity was classified as dorsal intercalated segmental instability. If the lunate was flexed anteriorly more than 15 degrees, the deformity was classified as volar intercalated segmental instability.
Second, the radiographs were examined for ligamentous disruption in the proximal carpal row. A diastasis or discordant motion within this row represents dissociative carpal instability. Typically, dissociation of the scapholunate joint, represented by a diastasis between the scaphoid and the lunate, presents as dorsal intercalated segmental instability in which the scaphoid flexes anteriorly while the dissociative lunate slides volarly on the radius as its concave surface turns dorsally. Dissociation of the lunotriquetral joint typically results in volar intercalated segmental instability in which the triquetrum rotates dorsally and the lunate flexes anteriorly. Other patterns of dissociative carpal instability have been described, including the scapholunate advanced collapse wrist. In this pattern, a longstanding dissociation of the proximal carpal row leads to osteoarthrosis of the radiocarpal and scapholunate joints34. Non-dissociative carpal instability indicates that there is no dissociation between the bones of the proximal carpal row. A mid-carpal instability pattern, in which there is a discordant position between the proximal and distal carpal rows, is an example of non-dissociative carpal instability. This typically results in volar intercalated segmental instability with a volarly flexed lunate and a volarly displaced, dorsally rotated distal carpal row. Finally, carpal instability may be classified as either static or dynamic. In dynamic carpal instability, the orientation of the carpus is aberrant only during certain motions or while the wrist is held in certain positions. The orientation is most commonly abnormal during pronation of the forearm and ulnar deviation of the wrist29. Dynamic patterns of instability appear normal on plain radiographs. Occasionally, the dynamic pattern can be identified on radiographs made with the wrist in the clenched-fist position, but usually it can be identified only during physical examination or on cineradiographs. The limitations of the present study, in which patients were examined with plain radiographs only, restricted us to the determination of static carpal instability. Patients who were diagnosed as having carpal instability were compared with patients in the entire paraplegic study population to determine if risk factors for carpal instability could be identified. The age of the patient at the time of the study and at the time of the spinal cord injury as well as the level and duration of the spinal cord injury were examined. The Fisher exact test was used to determine significance at the 95 per cent confidence level. A control group of forty-three paraplegic patients who met the criteria for inclusion in the study but who did not have pain in the wrist was established. They were examined, at the time of their routine outpatient care in the multidisciplinary spinal cord injury clinic, for symptoms in the wrist to validate the accuracy of the questionnaire. No subject was found to have symptoms or physical findings consistent with carpal instability, and none of the radiographs made for these subjects demonstrated carpal instability.
Radiographic analysis demonstrated static carpal instability in nine patients (sixteen wrists). Six of these patients (eleven wrists) had volar intercalated segmental instability, and one patient (one wrist) had dorsal intercalated segmental instability with a radiolunate angle of 18 degrees. Two patients (four wrists) had advanced collapse of the scapholunate joint bilaterally. Both wrists in each of these last two patients had advanced dissociation between the scaphoid and the lunate with marked osteoarthrosis. The volar-flexed radiolunate angle in the eleven wrists with volar intercalated segmental instability ranged from 17 to 37 degrees (average, 25 degrees) (Fig. 2). The capitolunate angle was extended in a commensurate manner such that the axes of the radius, capitate, and third metacarpal were parallel to each other. All eleven wrists demonstrated volar subluxation of the base of the capitate on the lunate. On the lateral radiographs of the wrist in extension, the lunate extended into a neutral position. The anteroposterior radiographs of the wrist in neutral, in radial deviation, and in ulnar deviation showed no evidence of dissociation of the proximal carpal row. This represented non-dissociative carpal instability.
Physical examination of the eleven wrists that had volar intercalated segmental instability demonstrated substantially limited flexion (usually less than 45 degrees). Extension was generally not limited, allowing the wrist to be placed in extension during weight-bearing. Pain was present at the extremes of extension and flexion and was greater in flexion. No wrist had a dynamic shift of either the mid-carpal or the lunotriquetral joint or a positive scaphoid-instability test. No patient had evidence of generalized ligamentous laxity. The duration of the spinal cord injury ranged from sixteen to fifty years (average, thirty years) for the nine patients who had carpal instability and from two to fifty years (average, sixteen years) for the entire study population. The duration of the spinal cord injury was more than twenty years for eight of the nine patients who had carpal instability, compared with forty-five (28 per cent) of the 162 patients in the entire study population. These differences were significant at the 95 per cent confidence level (p = 0.01). At the time of the study, the average age of the nine patients who had carpal instability was fifty-three years (range, forty-four to sixty-nine years), compared with forty-six years (range, eighteen to eighty-one years) for the entire study population. This difference was not significant (p = 0.18). There was no predilection for a level of spinal cord injury in the nine patients who had carpal instability.
In the United States, an estimated 200,000 patients have had a traumatic spinal cord injury17,36. These injuries are the results of motor-vehicle accidents, falls, and gunshot wounds, and they occur most often in individuals in the second, third, or fourth decade of life17,36. With the advances made in rehabilitative medicine since the mid-1970's, most of these people now have a nearly normal life span. During their lifetime, they subject the upper extremities to decades of increased demand as they adapt to activities of daily living without the function of the lower extremities. Previous investigations have demonstrated shoulder impingement, tears of the rotator cuff, and carpal tunnel syndrome occurring with increased frequency in patients who have a spinal cord injury. The earliest study, of which we are aware, on weight-bearing upper extremities was performed in 1985 by Aljure et al.2, who found a 40 per cent prevalence of carpal tunnel syndrome in forty-seven paraplegic patients. Subsequent work by several authors confirmed these results and suggested that the prevalence of carpal tunnel syndrome increases with the duration of the spinal cord injury8,9,32. In 1987, Bayley et al.4 demonstrated an increased prevalence of shoulder impingement and tears of the rotator cuff in paraplegic patients. Subsequent authors reported similar results and demonstrated that the prevalence of disability of the shoulder increased with the duration of weight-bearing on the upper extremity4,8,26. In the present study, nine (6 per cent) of 162 paraplegic patients had static carpal instability on radiographic examination. As with other disabilities described in the weight-bearing upper extremity, the prevalence of carpal instability increased with the duration of the spinal cord injury. A study based on a screening questionnaire has statistical deficiencies with regard to the determination of the prevalence within a population. Limitations of our study design did not allow the radiographic and physical examination of all paraplegic patients who were followed at our spinal cord injury center. The inability to examine each patient led to the use of the screening questionnaire. Nearly 90 per cent of our paraplegic population responded to our mailing. This extraordinary rate of response provided an adequate sampling of the population. To ensure that the questionnaire screened this population effectively, forty-three paraplegic patients who had indicated on the questionnaire that they did not have symptoms in the wrists were examined at their routine appointment. No patient in this control group was found to have a notable disorder in either upper extremity. Radiographic examination demonstrated that carpal instability was not a silent finding in asymptomatic paraplegic patients. We believe that the questionnaire effectively screened our paraplegic population. True prevalence studies require large populations for accurate calculations. While the paraplegic population in this study was relatively small, it was much larger than that in previous studies regarding the prevalence of disabilities in the upper extremities of patients who had a spinal cord injury2,4,8,9. Our study group was prospectively determined by strict inclusion criteria with which an entire paraplegic population was screened. Previous studies on weight-bearing upper extremities have been based on hospitalized patients. Our study was limited to the investigation of static carpal instability. Additional investigation with cineradiography may have identified patients who had dynamic carpal instability. Plain radiographs failed to demonstrate the cause of symptoms in several patients in whom carpal instability was suspected on the basis of the physical examination. Therefore, the true prevalence of carpal instability in paraplegic individuals may be higher than the 6 per cent found in this study. The predominant pattern of carpal instability in this study, non-dissociative volar intercalated segmental instability, was found in eleven wrists (six patients). The deformity presented in a uniform pattern with volar subluxation of the capitate, dorsiflexion of the mid-carpal joint, and no evidence of dissociation of the scapholunate or lunotriquetral joint. In large studies of carpal instability, volar intercalated segmental instability has been far less common, occurring only one-sixth as frequently as dorsal instability30. The relative frequency and the uniform pattern of presentation of the volar carpal instability in our study suggest a common etiology. Since initial studies on carpal instability dealt with the more common dorsal intercalated segmental instability pattern, only recently has insight been gained with regard to the volar pattern of carpal instability. Initial studies on carpal instability by Linscheid et al.23 suggested that volar intercalated segmental instability was a result of either a dissociation between the lunate and the triquetrum, due to a sprain of the mid-carpal ligaments, or a normal variant in people who have marked ligamentous laxity. Dissociation of the lunotriquetral joint, which is on the ulnar side, has been compared with patterns of instability on the radial side. The disruption of the lunotriquetral ligament is analogous to an unstable fracture of the scaphoid that leads to a transscaphoid perilunate dorsal instability pattern of carpal collapse3. With the link between the lunate and the triquetrum disrupted, these two bones rotate discordantly, allowing collapse of the wrist into volar intercalated segmental instability. Sequential sectioning studies of the ligamentous support of the triquetrum, analogous to the classic work of Mayfield et al.24,25 on perilunate instability on the radial side, have demonstrated the development of a perilunate pattern of carpal collapse on the ulnar side15,33. By definition, dissociation of the lunotriquetral joint is an example of a dissociative pattern of carpal instability. Linscheid et al.23 suggested that the development of mid-carpal instability is due to rupture or attenuation of the mid-carpal ligamentous support. Insight into mid-carpal instability has been based on anatomical studies of the volar intercarpal ligaments1,24,27. These studies demonstrated the distally based arcuate ligamentous complex and, just proximal, a region of minimum ligamentous support centered over the mid-carpal joint, the space of Poirier24,27. The arcuate ligament, made up of the scaphocapitate and triquetrohamatocapitate ligaments, acts as the primary stabilizer of the mid-carpal joint27,30. Disruption of the ulnar arm of the arcuate complex has been shown to result in volar intercalated segmental instability with volar subluxation of the mid-carpal joint1,20,31. Similarly, disruption of the radial arm of the arcuate complex has been shown to produce volar instability16. These studies demonstrated that traumatic disruption of the mid-carpal ligamentous support leads to a non-dissociative pattern of volar intercalated segmental instability, as was seen in eleven wrists in the present study. No anatomical investigation was possible with our study design. However, the results of previous studies1,20,31 on mid-carpal instability suggest that chronic attenuation of the ligaments of the arcuate complex from weight-bearing on the upper extremity may have led to the volar intercalated segmental instability in the patients in the present study. Non-invasive investigation of the anatomy of the carpal ligaments with magnetic resonance imaging or arthrography has shown poor sensitivity with regard to the integrity of the volar inter-carpal ligaments. Invasive investigation, at the time of a reconstructive procedure, was not a consideration for any of our patients. Because paraplegic patients are so dependent on the upper extremities and because of the immobilization and rehabilitation necessitated by a limited mid-carpal arthrodesis16,20,30, none of the six patients in our study who had mid-carpal instability would consider operative reconstruction. In conclusion, the present study of a paraplegic population demonstrated an association between carpal instability and chronic repetitive stress on the wrist. Static carpal instability was found in 6 per cent of our entire study population and in 18 per cent of the patients who had had the spinal cord injury for more than twenty years. This increase in the prevalence with the duration of stress on the wrist suggests chronic repetitive stress as an etiology of carpal instability. The predominant pattern of carpal instability was non-dissociative volar intercalated segmental instability.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
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