SCIENTIFIC ARTICLE
Evaluation of Radiographic Instability of the Trapeziometacarpal Joint in Women With Carpal Tunnel Syndrome Jeong Hwan Kim, MD,* Hyun Sik Gong, MD, PhD,† Youn Ho Kim, MD,† Seung Hwan Rhee, MD,† Jihyoung Kim, MD,† Goo Hyun Baek, MD†
Purpose To determine whether median nerve dysfunction measured by electrophysiologic studies in carpal tunnel syndrome (CTS) is associated with thumb trapeziometacarpal (TMC) joint instability. Methods We evaluated 71 women with CTS and 31 asymptomatic control women. Patients with generalized laxity or TMC joint osteoarthritis were excluded. We classified the electrophysiologic severity of CTS based on nerve conduction time and amplitude and assessed radiographic instability of the TMC joint based on TMC joint stress radiographs. We compared subluxation ratio between patients with CTS and controls and performed correlation analysis of the relationship between the electrophysiologic grade and subluxation ratio. Results Thirty-one patients were categorized into the mild CTS subgroup and 41 into the severe CTS subgroup. There was no significant difference in subluxation ratio between the control group and CTS patients or between the control group and CTS subgroup patients. Furthermore, there was no significant correlation between electrophysiologic grade and subluxation ratio. Conclusions This study demonstrated that patients with CTS did not have greater radiographic TMC joint instability compared with controls, and suggests that TMC joint stability is not affected by impaired median nerve function. Further studies could investigate how to better evaluate proprioceptive function of TMC joint and whether other nerves have effects on TMC joint motor/proprioceptive function, to elucidate the relationship between neuromuscular control of the TMC joint, its stability, and its progression to osteoarthritis. (J Hand Surg Am. 2015;40(7):1298e1302. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Diagnostic II. Key words Instability, trapeziometacarpal joint, osteoarthritis, carpal tunnel syndrome, median nerve.
From the *Department of Orthopedic Surgery, Seoul Medical Center; and the †Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, Korea. Received for publication November 26, 2014; accepted in revised form April 15, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Hyun Sik Gong, MD, PhD, Department of Orthopedic Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Korea; e-mail: [email protected]. 0363-5023/15/4007-0003$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.04.026
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thumb trapeziometacarpal (TMC) joint osteoarthritis are common in postmenopausal women.1,2 These 2 conditions are frequently seen together.1,3 Studies have suggested several potential causes of TMC joint osteoarthritis, such as ligamentous laxity, bony incongruence between the trapezium and metacarpal base, the aging process, and hormonal status.4e11 Although a precise mechanism has not been clearly confirmed, instability of the TMC joint in association ARPAL TUNNEL SYNDROME (CTS) AND
INSTABILITY OF TMC JOINT IN CTS
with some of these causes is related to TMC joint osteoarthritis.4e6,11 There is controversy regarding the association between CTS and TMC joint osteoarthritis. Florack et al12 reported that 39% of patients who underwent arthroplasty of TMC joint had CTS. Other surgeons13,14 described a surgical approach using the same incision for both TMC joint arthroplasty and carpal tunnel release. However, Shin et al15 showed that the prevalence of CTS was similar in patients with and those without radiographic findings of TMC joint arthritis in a population-based study. The function of nerves innervating the TMC joint can affect joint stability because intact joint innervation and preserved proprioceptive function is essential for normal joint homeostasis.16e18 The TMC joint is innervated by branches from the median, radial, and lateral antebrachial cutaneous nerves, which provide proprioceptive and nociceptive fibers to the joint capsule.19e22 Muscle contribution to joint stability is a combination of intrinsic and extrinsic muscles that are innervated by the median, ulnar, and radial nerves. Stability of the TMC joint is primarily ligamentous, and other factors may contribute to joint stability.4e11 Neuromuscular factors including balance of the muscle forces acting across the joint and proprioceptive and nociceptive input may contribute to the pathophysiology of the TMC joint. Because CTS has been associated with TMC joint osteoarthritis, we hypothesized that median nerve dysfunction from CTS could lead to changes in joint proprioception or joint nociception that result in the joint instability. Additional contributions from weakening of the thenar muscles could contribute further to TMC joint instability because the median nerve innervates most of the thenar muscles overlying the joint and the nerve dysfunction may cause muscle imbalance between median and other innervated intrinsic and extrinsic muscles. Therefore, the purpose of this study was to determine whether median nerve dysfunction measured by electrophysiologic studies in CTS was associated with TMC joint instability.
and a positive electrophysiologic study. We tried to eliminate potentially confounding variables by excluding the patients from both the study and the control group who had a history of trauma to the TMC joint; generalized ligament laxity defined by scores of 4 or more according the scale of Beighton and Horan,23 which could be a confounding factor; radiographic TMC joint osteoarthritis; and underlying diseases that might affect neuromuscular status, such as stroke, Parkinson syndrome, sensorimotor polyneuropathy, and diabetic neuropathy. Women have greater joint mobility than men24; thus, comparison within the same sex is appropriate. Men were excluded from the analysis because there were too few for statistical analysis. Finally, 71 women with CTS and 31 control women were enrolled in this study. Mean age of all subjects was 56 years (range, 32e79 y). Mean ages of the control and CTS groups were 56 years (range, 32e79 y) and 56 years (range, 32e78 y), respectively. Evaluation of median nerve function We performed electrophysiologic studies for all subjects in a standard manner while maintaining skin temperature above 31 C. We performed sensory nerve conduction studies using antidromic methods by stimulating at the wrist and recording using ring electrodes from the index and little fingers. Motor nerve conduction studies used supramaximal stimulation at the wrist and were recorded with a surface electrode from the abductor pollicis brevis muscle and abductor digiti minimi muscle. We classified electrophysiologic severity according to the Bland classification.25 Based on nerve conduction time and amplitude, the classification included the following 7 grades: 0 (normal), 1 (very mild, demonstrable only with the most sensitive tests); 2 (mild, slow sensory conduction and normal motor conduction); 3 (moderately severe, motor terminal latency greater than 4.5 ms and less than 6.5 ms with preserved sensory nerve action potential); 4 (severe, absent sensory nerve action potential and motor terminal latency less than 6.5 ms); 5 (very severe, motor terminal latency greater than 6.5 ms); and 6 (extremely severe, unrecordable surface motor potentials less than 0.2 mV). Based on the Bland classification, we categorized patients into normal, mild (grades 1 and 2), and severe (grade 3 or over) subgroups. In addition, a single surgeon evaluated thenar muscle atrophy and considered it to be present if the bulk of the muscle was reduced markedly or if normal elastic consistency was absent during opposition.26
MATERIALS AND METHODS Subjects Our institutional review board approved this study. We prospectively evaluated radiographic TMC joint instability in women with CTS who were scheduled to undergo carpal tunnel release and asymptomatic control women between January 2013 and December 2013 at our urban tertiary referral hospital. Diagnosis of CTS was made based on both symptoms of CTS J Hand Surg Am.
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Evaluation of radiographic TMC joint instability We evaluated the radiographic instability of the TMC joint using a stress view radiograph modified by Wolf et al.24 A posteroanterior radiograph was taken with the patient pressing both thumbs together with the radial borders of both thumbs contacting each other. We measured radial subluxation (RS) of the base of the first metacarpal and the articular width (AW) of the etacarpal. The subluxation ratio (SR) of the RS to the AW was calculated as a measure of first metacarpal subluxation considered to be the measurement of the radiographic instability of the TMC joint (Fig. 1). Two authors, who were orthopedic surgeons and blinded to patients’ information, measured the radiographic parameters twice with a 2-week interval between readings. Intra- and inter-rater reliabilities of radiologic assessments were tested using interclass correlation coefficients. The intra-class correlation coefficient value of the intra-rater reliability was 0.89 and the inter-rater reliability was 0.86. Because these intra-class correlation coefficient values indicated high reliability, we used the radiographic parameters measured by one of the authors in the analysis. A previous study showed that these measurements had high inter- and intra-rater reliability (average intra-class correlation coefficient for inter-rater reliability of 0.8).24
FIGURE 1: Trapeziometacarpal joint stress view radiograph. Measurement of AW and RS.
Table 1 lists the mean SR, SDs, ranges, and P values. There were no significant differences in SR between any of the groups and controls. There was no significant correlation between SR and age (Pearson coefficient r ¼ e0.09; P ¼ .35) or between SR and Bland electrophysiologic grade (r ¼ e0.01; P ¼ .94).
Statistical analysis We compared the SR between groups using the t test. We also performed correlation analyses between SR and electrophysiologic grade and age. P < .05 was considered statistically significant. To determine statistical power, the primary outcome variable was the SR. A previous study reported a mean SR of 0.31 (range, 0.06e0.58).27 Therefore, we assumed the standard deviation to be about 0.1. The current study was designed to determine a 30% difference in the SR between the 2 groups (for an effect size of 1.0). A power analysis indicated that a sample size of 23 patients to each of the groups would provide 90% statistical power to detect this effect size between groups (a ¼ .05; b ¼ .10) with use of the t test.
DISCUSSION Eaton and Littler4 described basal joint hypermobility as a factor in the development of TMC joint osteoarthritis. Reports of TMC joint subluxation and arthritis in patients with Ehlers-Danlos syndrome support the concept that joint instability leads to TMC joint osteoarthritis.5,6 The stability of inherently unstable TMC joint depends on the bony anatomy of the joint and the action of restraining ligaments and periarticular muscles.4,22,28e32 Pellegrini29 showed that attrition of the anterior oblique ligament caused abnormal mechanical loading on the TMC joint, resulting in degenerative cartilage wear. However, Ladd et al32 reported that the dorsal ligament complex innervated by superficial radial nerve and lateral antebrachial cutaneous nerve was the thickest and had the highest cellularity and innervation. Researchers33e36 have suggested that the muscles around the TMC joint could provide dynamic stability of the joint. Furthermore, the function of nerves innervating the TMC joint can affect joint stability by their nociceptive and proprioceptive function.16e21 Hagert et al21 reported that the presence of mechanoreceptors in the dorsal TMC joint ligaments
RESULTS In this electrophysiologic study, there were 31 normal, 13 grade 1, 17 grade 2, 27 grade 3, 3 grade 4, 9 grade 5, and 1 grade 6 CTS findings. Therefore, 31 hands were in the normal group, 30 hands were combined into the mild CTS group (Bland grades 1 and 2), and 41 hands were placed in the severe CTS group (Bland grade 3 or more). Ten patients had thenar muscle atrophy (Table 1). J Hand Surg Am.
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TABLE 1.
Comparison of SR Between Patients With CTS and Controls n
Mean SR (SD, range)
P Value Compared With Control Group
31
56
0.26 (0.14, 0e0.57)
Mild
30
56
0.30 (0.13, 0.05e0.47)
Severe
41
57
0.27 (0.13, 0e0.46)
1.00
Control group CTS group
Age, y
.95
Total
71
56
0.28 (0.13, 0e0.47)
.50
Thenar atrophy
10
62
0.32 (0.09, 0.21e0.46)
.20
function.37,38 In addition, we evaluated only the median nerve by electrophysiologic studies, not other nerve functions. Therefore, electrically identified compression neuropathy of the only one nerve may not cause significant loss of proprioception at the TMC joint. Another issue is whether proprioceptive fibers are lost early or late if they are affected in CTS. In animal studies, large fibers with proprioceptive function were damaged earlier than were small fibers,39 whereas in a human study, small Ad and C fibers were damaged earlier than large Ab fibers in CTS.40 In addition, joint proprioception is a function not only of peripheral nerves innervating the joint, but also of the central nervous system involved in the integration of sensory inputs and motor control.41 Further studies may help evaluate the proprioceptive function of the TMC joint in a more sensitive way and determine whether TMC joint proprioceptive function is affected by other nerves. There were several limitations to this study. First, although we excluded patients with generalized ligament laxity and a history of trauma to the thumb, we could not evaluate the status of TMC joint ligaments that are important for joint stability. Furthermore, we did not evaluate hormonal status and occupational factors that might have influenced TMC joint stability. Second, all patients were women who chose to undergo surgery. Therefore, the findings of this study may not be generalized to all women with CTS. Finally, we evaluated only parts of the thenar muscles that are innervated by the median nerve, although TMC joint stability can be influenced by other intrinsic and extrinsic muscles. A study suggested that the first dorsal interosseous muscle could be a dynamic stabilizer of the TMC joint.35 Further studies looking at electromyelograms of other muscles involved in the TMC joint would be required. Further studies could better evaluate the proprioceptive function of the TMC joint and determine whether other nerves have effects on TMC joint motor/ proprioceptive function and elucidate the relationship
might infer a proprioceptive function of these ligaments in addition to their biomechanical importance in joint stability. The thenar branch of the median nerve innervates most of the thenar muscles and in part contributes to the TMC joint, although the palmar cutaneous branch of the median nerve also innervates the TMC joint and the lateral antebrachial cutaneous nerve and superficial radial nerve contribute most of the mechanoreceptors identified in the dorsal ligaments.19e21 In this study, we wanted to determine whether median nerve dysfunction could affect TMC joint stability. This study showed no difference in TMC joint instability between the control and CTS groups. In addition, we found no correlation between electrophysiologic grade and joint instability. Florack et al12 reported that 95 of 246 patients who had TMC joint arthroplasty (39%) had CTS. They postulated that the association between the 2 conditions might have resulted from alterations in the osseous anatomy of the carpal canal caused by degenerative arthritis or from inflammation in the TMC joint. However, they acknowledged that inflammatory changes were not identified in histologic studies of flexor tenosynovium in patients with CTS. Shin et al15 evaluated radiographs and nerve conduction studies in 368 individuals aged more than 65 years in a populationbased cohort and found no correlation between the electrophysiological severity of CTS and the radiographic grade of TMC joint osteoarthritis. However, those 2 studies had no control groups. Their subjects were either patients with severe osteoarthritis who needed surgical treatment or community-dwelling patients who might have had asymptomatic radiographic changes.12,15 We evaluated whether median nerve dysfunction contributes to joint instability, and our results do not support the association. We could not determine whether median nerve dysfunction could lead to changes in proprioception of the TMC joint. Other studies on the wrist after anterior interosseous neurectomy and posterior interosseous neurectomy did not show loss of proprioceptive J Hand Surg Am.
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between neuromuscular control of the TMC joint and its stability and progression to osteoarthritis.
19. Lorea DP, Berthe JV, De Mey A, Coessens BC, Rooze M, Foucher G. The nerve supply of the trapeziometacarpal joint. J Hand Surg Br. 2002;27(3):232e237. 20. Poupon M, Duteille F, Cassagnau E, Leborgne J, Pannier M. Anatomical study of the nerve supply of the trapeziometacarpal joint: fifteen dissections. Rev Chir Orthop Reparatrice Appar Motil. 2004;90(4):346e352. 21. Hagert E, Lee J, Ladd AL. Innervation patterns of thumb trapeziometacarpal joint ligaments. J Hand Surg Am. 2012;37(4):706e714. 22. Neumann DA, Bielefeld T. The carpometacarpal joint of the thumb: stability, deformity, and therapeutic intervention. J Orthop Sports Phys Ther. 2003;33(7):386e399. 23. Beighton P, Horan F. Orthopaedic aspects of the Ehlers-Danlos syndrome. J Bone Joint Surg Br. 1969;51(3):444e453. 24. Wolf JM, Oren TW, Ferguson B, Williams A, Petersen B. The carpometacarpal stress view radiograph in the evaluation of trapeziometacarpal joint laxity. J Hand Surg Am. 2009;34(8):1402e1406. 25. Bland JD. A neurophysiological grading scale for carpal tunnel syndrome. Muscle Nerve. 2000;23(8):1280e1283. 26. Mallette P, Zhao M, Zurakowski D, Ring D. Muscle atrophy at diagnosis of carpal and cubital tunnel syndrome. J Hand Surg Am. 2007;32(6):855e858. 27. Wolf JM, Schreier S, Tomsick S, Williams A, Petersen B. Radiographic laxity of the trapeziometacarpal joint is correlated with generalized joint hypermobility. J Hand Surg Am. 2011;36(7):1165e1169. 28. Bettinger PC, Linscheid RL, Berger RA, Cooney WP, An K-N. An anatomic study of the stabilizing ligaments of the trapezium and trapeziometacarpal joint. J Hand Surg Am. 1999;24(4):786e798. 29. Pellegrini VD Jr. Osteoarthritis of the trapeziometacarpal joint: the pathophysiology of articular cartilage degeneration: I. Anatomy and pathology of the aging joint. J Hand Surg Am. 1991;16(6):967e974. 30. Edmunds JO. Current concepts of the anatomy of the thumb trapeziometacarpal joint. J Hand Surg Am. 2011;36(1):170e182. 31. Lin JD, Karl JW, Strauch RJ. Trapeziometacarpal joint stability: the evolving importance of the dorsal ligaments. Clin Orthop Relat Res. 2014;472(4):1138e1145. 32. Ladd AL, Lee J, Hagert E. Macroscopic and microscopic analysis of the thumb carpometacarpal ligaments: a cadaveric study of ligament anatomy and histology. J Bone Joint Surg Am. 2012;94(16):1468e1477. 33. Cooney W III, Chao E. Biomechanical analysis of static forces in the thumb during hand function. J Bone Joint Surg Am. 1977;59(1): 27e36. 34. Smutz WP, Kongsayreepong A, Hughes RE, Niebur G, Cooney WP, An K-N. Mechanical advantage of the thumb muscles. J Biomech. 1998;31(6):565e570. 35. Boutan M. Role du coule opposant-1er interosseux dorsal dans la stablilite de l’articulation trapezo-metacarpienne. Ann Kinesither. 2000;27(7):316e324. 36. O’Brien VH, Giveans MR. Effects of a dynamic stability approach in conservative intervention of the carpometacarpal joint of the thumb: a retrospective study. J Hand Ther. 2013;26(1):44e51. 37. Gay A, Harbst K, Hansen DK, Laskowski ER, Berger RA, Kaufman KR. Effect of partial wrist denervation on wrist kinesthesia: wrist denervation does not impair proprioception. J Hand Surg Am. 2011;36(11):1774e1779. 38. Patterson RW, Niel MV, Shimko P, Pace C, Seitz WH. Proprioception of the wrist following posterior interosseous sensory neurectomy. J Hand Surg Am. 2010;35(1):52e56. 39. Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by an pneumatic tourniquet. J Anat. 1972;113(3): 433e455. 40. Tamburin S, Cacciatori C, Praitano ML, et al. Median nerve smalland large-fiber damage in carpal tunnel syndrome: a quantitative sensory testing study. J Pain. 2011;12(2):205e212. 41. Proske U, Gandevia SC. The proprioceptive senses: their roles in signaling body shape, body position and movement, and muscle force. Physiol Rev. 2012;92(4):1651e1697.
ACKNOWLEDGMENT This work was supported in part by the institution’s research fund (grant 14-2014-001). We received no specific grant from any other funding agency in the public, commercial, or not-for profit sectors. The authors thank the Medical Research Collaborating Center at Seoul National University Bundang Hospital for statistical analyses. REFERENCES 1. Bickel KD. Carpal tunnel syndrome. J Hand Surg Am. 2010;35(1): 147e152. 2. Pellegrini VD Jr. Osteoarthritis at the base of the thumb. Orthop Clin North Am. 1992;23(1):83e102. 3. Armstrong AL, Hunter JB, Davis TR. The prevalence of degenerative arthritis of the base of the thumb in post-menopausal women. J Hand Surg Br. 1994;19(3):340e341. 4. Eaton RG, Littler JW. Ligament reconstruction for the painful thumb carpometacarpal joint. J Bone Joint Surg. 1973;55(8):1655e1666. 5. Moore JR, Tolo VT, Weiland AJ. Painful subluxation of the carpometacarpal joint of the thumb in Ehlers-Danlos syndrome. J Hand Surg Am. 1985;10(5):661e663. 6. Gamble JG, Mochizuki C, Rinsky LA. Trapeziometacarpal abnormalities in Ehlers-Danlos syndrome. J Hand Surg Am. 1989;14(1): 89e94. 7. Bettinger PC, Linscheid RL, Berger RA, Cooney WP, An K-N. Trapezial tilt: a radiographic correlation with advanced trapeziometacarpal joint arthritis. J Hand Surg Am. 2001;26(4):692e697. 8. Kurosawa S, Tsuchiya I, Takagishi K. Trapezial-metacarpal joint arthritis: radiographic correlation between first metacarpal articular tilt and dorsal subluxation. J Hand Surg Am. 2013;38(2):302e308. 9. Halilaj E, Moore DC, Laidlaw DH, et al. The morphology of the thumb carpometacarpal joint does not differ between men and women, but changes with aging and early osteoarthritis. J Biomech. 2014;27(11): 2709e2714. 10. Wolf JM, Scher DL, Etchill EW, et al. Relationship of relaxin hormone and thumb carpometacarpal joint arthritis. Clin Orthop Relat Res. 2014;472(4):1130e1137. 11. Jónsson H, Elíasson GJ, Jónsson A, et al. High hand joint mobility is associated with radiological CMC1 osteoarthritis: the AGESReykjavik study. Osteoarthritis Cartilage. 2009;17(5):592e595. 12. Florack TM, Miller RJ, Pellegrini VD, Burton RI, Dunn MG. The prevalence of carpal tunnel syndrome in patients with basal joint arthritis of the thumb. J Hand Surg Am. 1992;17(4):624e630. 13. Melone CP Jr, Beavers B, Isani A. The basal joint pain syndrome. Clin Orthop Relat Res. 1987;220:58e67. 14. Cassidy C, Glennon PE, Stein AB, Ruby LK. Basal joint arthroplasty and carpal tunnel release through a single incision: an in vitro study. J Hand Surg Am. 2004;29(6):1085e1088. 15. Shin CH, Paik NJ, Lim JY, et al. Carpal tunnel syndrome and radiographically evident basal joint arthritis of the thumb in elderly Koreans. J Bone Joint Surg Am. 2012;94(16):e1201ee1206. 16. Johansson H, Sjölander P, Sojka P. A sensory role for the cruciate ligaments. Clin Orthop Relat Res. 1991;268:161e178. 17. Michelson JD, Hutchins C. Mechanoreceptors in human ankle ligaments. J Bone Joint Surg Br. 1995;77(2):219e224. 18. Sjölander P, Johansson H, Djupsjöbacka M. Spinal and supraspinal effects of activity in ligament afferents. J Electromyogr Kinesiol. 2002;12(3):167e176.
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Evaluation of Radiographic Instability of the Trapeziometacarpal Joint in Women With Carpal Tunnel Syndrome Jeong Hwan Kim, MD,* Hyun Sik Gong, MD, PhD,† Youn Ho Kim, MD,† Seung Hwan Rhee, MD,† Jihyoung Kim, MD,† Goo Hyun Baek, MD†
Purpose To determine whether median nerve dysfunction measured by electrophysiologic studies in carpal tunnel syndrome (CTS) is associated with thumb trapeziometacarpal (TMC) joint instability. Methods We evaluated 71 women with CTS and 31 asymptomatic control women. Patients with generalized laxity or TMC joint osteoarthritis were excluded. We classified the electrophysiologic severity of CTS based on nerve conduction time and amplitude and assessed radiographic instability of the TMC joint based on TMC joint stress radiographs. We compared subluxation ratio between patients with CTS and controls and performed correlation analysis of the relationship between the electrophysiologic grade and subluxation ratio. Results Thirty-one patients were categorized into the mild CTS subgroup and 41 into the severe CTS subgroup. There was no significant difference in subluxation ratio between the control group and CTS patients or between the control group and CTS subgroup patients. Furthermore, there was no significant correlation between electrophysiologic grade and subluxation ratio. Conclusions This study demonstrated that patients with CTS did not have greater radiographic TMC joint instability compared with controls, and suggests that TMC joint stability is not affected by impaired median nerve function. Further studies could investigate how to better evaluate proprioceptive function of TMC joint and whether other nerves have effects on TMC joint motor/proprioceptive function, to elucidate the relationship between neuromuscular control of the TMC joint, its stability, and its progression to osteoarthritis. (J Hand Surg Am. 2015;40(7):1298e1302. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Diagnostic II. Key words Instability, trapeziometacarpal joint, osteoarthritis, carpal tunnel syndrome, median nerve.
From the *Department of Orthopedic Surgery, Seoul Medical Center; and the †Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, Korea. Received for publication November 26, 2014; accepted in revised form April 15, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Hyun Sik Gong, MD, PhD, Department of Orthopedic Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Korea; e-mail: [email protected]. 0363-5023/15/4007-0003$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.04.026
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Published by Elsevier, Inc. All rights reserved.
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thumb trapeziometacarpal (TMC) joint osteoarthritis are common in postmenopausal women.1,2 These 2 conditions are frequently seen together.1,3 Studies have suggested several potential causes of TMC joint osteoarthritis, such as ligamentous laxity, bony incongruence between the trapezium and metacarpal base, the aging process, and hormonal status.4e11 Although a precise mechanism has not been clearly confirmed, instability of the TMC joint in association ARPAL TUNNEL SYNDROME (CTS) AND
INSTABILITY OF TMC JOINT IN CTS
with some of these causes is related to TMC joint osteoarthritis.4e6,11 There is controversy regarding the association between CTS and TMC joint osteoarthritis. Florack et al12 reported that 39% of patients who underwent arthroplasty of TMC joint had CTS. Other surgeons13,14 described a surgical approach using the same incision for both TMC joint arthroplasty and carpal tunnel release. However, Shin et al15 showed that the prevalence of CTS was similar in patients with and those without radiographic findings of TMC joint arthritis in a population-based study. The function of nerves innervating the TMC joint can affect joint stability because intact joint innervation and preserved proprioceptive function is essential for normal joint homeostasis.16e18 The TMC joint is innervated by branches from the median, radial, and lateral antebrachial cutaneous nerves, which provide proprioceptive and nociceptive fibers to the joint capsule.19e22 Muscle contribution to joint stability is a combination of intrinsic and extrinsic muscles that are innervated by the median, ulnar, and radial nerves. Stability of the TMC joint is primarily ligamentous, and other factors may contribute to joint stability.4e11 Neuromuscular factors including balance of the muscle forces acting across the joint and proprioceptive and nociceptive input may contribute to the pathophysiology of the TMC joint. Because CTS has been associated with TMC joint osteoarthritis, we hypothesized that median nerve dysfunction from CTS could lead to changes in joint proprioception or joint nociception that result in the joint instability. Additional contributions from weakening of the thenar muscles could contribute further to TMC joint instability because the median nerve innervates most of the thenar muscles overlying the joint and the nerve dysfunction may cause muscle imbalance between median and other innervated intrinsic and extrinsic muscles. Therefore, the purpose of this study was to determine whether median nerve dysfunction measured by electrophysiologic studies in CTS was associated with TMC joint instability.
and a positive electrophysiologic study. We tried to eliminate potentially confounding variables by excluding the patients from both the study and the control group who had a history of trauma to the TMC joint; generalized ligament laxity defined by scores of 4 or more according the scale of Beighton and Horan,23 which could be a confounding factor; radiographic TMC joint osteoarthritis; and underlying diseases that might affect neuromuscular status, such as stroke, Parkinson syndrome, sensorimotor polyneuropathy, and diabetic neuropathy. Women have greater joint mobility than men24; thus, comparison within the same sex is appropriate. Men were excluded from the analysis because there were too few for statistical analysis. Finally, 71 women with CTS and 31 control women were enrolled in this study. Mean age of all subjects was 56 years (range, 32e79 y). Mean ages of the control and CTS groups were 56 years (range, 32e79 y) and 56 years (range, 32e78 y), respectively. Evaluation of median nerve function We performed electrophysiologic studies for all subjects in a standard manner while maintaining skin temperature above 31 C. We performed sensory nerve conduction studies using antidromic methods by stimulating at the wrist and recording using ring electrodes from the index and little fingers. Motor nerve conduction studies used supramaximal stimulation at the wrist and were recorded with a surface electrode from the abductor pollicis brevis muscle and abductor digiti minimi muscle. We classified electrophysiologic severity according to the Bland classification.25 Based on nerve conduction time and amplitude, the classification included the following 7 grades: 0 (normal), 1 (very mild, demonstrable only with the most sensitive tests); 2 (mild, slow sensory conduction and normal motor conduction); 3 (moderately severe, motor terminal latency greater than 4.5 ms and less than 6.5 ms with preserved sensory nerve action potential); 4 (severe, absent sensory nerve action potential and motor terminal latency less than 6.5 ms); 5 (very severe, motor terminal latency greater than 6.5 ms); and 6 (extremely severe, unrecordable surface motor potentials less than 0.2 mV). Based on the Bland classification, we categorized patients into normal, mild (grades 1 and 2), and severe (grade 3 or over) subgroups. In addition, a single surgeon evaluated thenar muscle atrophy and considered it to be present if the bulk of the muscle was reduced markedly or if normal elastic consistency was absent during opposition.26
MATERIALS AND METHODS Subjects Our institutional review board approved this study. We prospectively evaluated radiographic TMC joint instability in women with CTS who were scheduled to undergo carpal tunnel release and asymptomatic control women between January 2013 and December 2013 at our urban tertiary referral hospital. Diagnosis of CTS was made based on both symptoms of CTS J Hand Surg Am.
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Evaluation of radiographic TMC joint instability We evaluated the radiographic instability of the TMC joint using a stress view radiograph modified by Wolf et al.24 A posteroanterior radiograph was taken with the patient pressing both thumbs together with the radial borders of both thumbs contacting each other. We measured radial subluxation (RS) of the base of the first metacarpal and the articular width (AW) of the etacarpal. The subluxation ratio (SR) of the RS to the AW was calculated as a measure of first metacarpal subluxation considered to be the measurement of the radiographic instability of the TMC joint (Fig. 1). Two authors, who were orthopedic surgeons and blinded to patients’ information, measured the radiographic parameters twice with a 2-week interval between readings. Intra- and inter-rater reliabilities of radiologic assessments were tested using interclass correlation coefficients. The intra-class correlation coefficient value of the intra-rater reliability was 0.89 and the inter-rater reliability was 0.86. Because these intra-class correlation coefficient values indicated high reliability, we used the radiographic parameters measured by one of the authors in the analysis. A previous study showed that these measurements had high inter- and intra-rater reliability (average intra-class correlation coefficient for inter-rater reliability of 0.8).24
FIGURE 1: Trapeziometacarpal joint stress view radiograph. Measurement of AW and RS.
Table 1 lists the mean SR, SDs, ranges, and P values. There were no significant differences in SR between any of the groups and controls. There was no significant correlation between SR and age (Pearson coefficient r ¼ e0.09; P ¼ .35) or between SR and Bland electrophysiologic grade (r ¼ e0.01; P ¼ .94).
Statistical analysis We compared the SR between groups using the t test. We also performed correlation analyses between SR and electrophysiologic grade and age. P < .05 was considered statistically significant. To determine statistical power, the primary outcome variable was the SR. A previous study reported a mean SR of 0.31 (range, 0.06e0.58).27 Therefore, we assumed the standard deviation to be about 0.1. The current study was designed to determine a 30% difference in the SR between the 2 groups (for an effect size of 1.0). A power analysis indicated that a sample size of 23 patients to each of the groups would provide 90% statistical power to detect this effect size between groups (a ¼ .05; b ¼ .10) with use of the t test.
DISCUSSION Eaton and Littler4 described basal joint hypermobility as a factor in the development of TMC joint osteoarthritis. Reports of TMC joint subluxation and arthritis in patients with Ehlers-Danlos syndrome support the concept that joint instability leads to TMC joint osteoarthritis.5,6 The stability of inherently unstable TMC joint depends on the bony anatomy of the joint and the action of restraining ligaments and periarticular muscles.4,22,28e32 Pellegrini29 showed that attrition of the anterior oblique ligament caused abnormal mechanical loading on the TMC joint, resulting in degenerative cartilage wear. However, Ladd et al32 reported that the dorsal ligament complex innervated by superficial radial nerve and lateral antebrachial cutaneous nerve was the thickest and had the highest cellularity and innervation. Researchers33e36 have suggested that the muscles around the TMC joint could provide dynamic stability of the joint. Furthermore, the function of nerves innervating the TMC joint can affect joint stability by their nociceptive and proprioceptive function.16e21 Hagert et al21 reported that the presence of mechanoreceptors in the dorsal TMC joint ligaments
RESULTS In this electrophysiologic study, there were 31 normal, 13 grade 1, 17 grade 2, 27 grade 3, 3 grade 4, 9 grade 5, and 1 grade 6 CTS findings. Therefore, 31 hands were in the normal group, 30 hands were combined into the mild CTS group (Bland grades 1 and 2), and 41 hands were placed in the severe CTS group (Bland grade 3 or more). Ten patients had thenar muscle atrophy (Table 1). J Hand Surg Am.
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TABLE 1.
Comparison of SR Between Patients With CTS and Controls n
Mean SR (SD, range)
P Value Compared With Control Group
31
56
0.26 (0.14, 0e0.57)
Mild
30
56
0.30 (0.13, 0.05e0.47)
Severe
41
57
0.27 (0.13, 0e0.46)
1.00
Control group CTS group
Age, y
.95
Total
71
56
0.28 (0.13, 0e0.47)
.50
Thenar atrophy
10
62
0.32 (0.09, 0.21e0.46)
.20
function.37,38 In addition, we evaluated only the median nerve by electrophysiologic studies, not other nerve functions. Therefore, electrically identified compression neuropathy of the only one nerve may not cause significant loss of proprioception at the TMC joint. Another issue is whether proprioceptive fibers are lost early or late if they are affected in CTS. In animal studies, large fibers with proprioceptive function were damaged earlier than were small fibers,39 whereas in a human study, small Ad and C fibers were damaged earlier than large Ab fibers in CTS.40 In addition, joint proprioception is a function not only of peripheral nerves innervating the joint, but also of the central nervous system involved in the integration of sensory inputs and motor control.41 Further studies may help evaluate the proprioceptive function of the TMC joint in a more sensitive way and determine whether TMC joint proprioceptive function is affected by other nerves. There were several limitations to this study. First, although we excluded patients with generalized ligament laxity and a history of trauma to the thumb, we could not evaluate the status of TMC joint ligaments that are important for joint stability. Furthermore, we did not evaluate hormonal status and occupational factors that might have influenced TMC joint stability. Second, all patients were women who chose to undergo surgery. Therefore, the findings of this study may not be generalized to all women with CTS. Finally, we evaluated only parts of the thenar muscles that are innervated by the median nerve, although TMC joint stability can be influenced by other intrinsic and extrinsic muscles. A study suggested that the first dorsal interosseous muscle could be a dynamic stabilizer of the TMC joint.35 Further studies looking at electromyelograms of other muscles involved in the TMC joint would be required. Further studies could better evaluate the proprioceptive function of the TMC joint and determine whether other nerves have effects on TMC joint motor/ proprioceptive function and elucidate the relationship
might infer a proprioceptive function of these ligaments in addition to their biomechanical importance in joint stability. The thenar branch of the median nerve innervates most of the thenar muscles and in part contributes to the TMC joint, although the palmar cutaneous branch of the median nerve also innervates the TMC joint and the lateral antebrachial cutaneous nerve and superficial radial nerve contribute most of the mechanoreceptors identified in the dorsal ligaments.19e21 In this study, we wanted to determine whether median nerve dysfunction could affect TMC joint stability. This study showed no difference in TMC joint instability between the control and CTS groups. In addition, we found no correlation between electrophysiologic grade and joint instability. Florack et al12 reported that 95 of 246 patients who had TMC joint arthroplasty (39%) had CTS. They postulated that the association between the 2 conditions might have resulted from alterations in the osseous anatomy of the carpal canal caused by degenerative arthritis or from inflammation in the TMC joint. However, they acknowledged that inflammatory changes were not identified in histologic studies of flexor tenosynovium in patients with CTS. Shin et al15 evaluated radiographs and nerve conduction studies in 368 individuals aged more than 65 years in a populationbased cohort and found no correlation between the electrophysiological severity of CTS and the radiographic grade of TMC joint osteoarthritis. However, those 2 studies had no control groups. Their subjects were either patients with severe osteoarthritis who needed surgical treatment or community-dwelling patients who might have had asymptomatic radiographic changes.12,15 We evaluated whether median nerve dysfunction contributes to joint instability, and our results do not support the association. We could not determine whether median nerve dysfunction could lead to changes in proprioception of the TMC joint. Other studies on the wrist after anterior interosseous neurectomy and posterior interosseous neurectomy did not show loss of proprioceptive J Hand Surg Am.
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between neuromuscular control of the TMC joint and its stability and progression to osteoarthritis.
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ACKNOWLEDGMENT This work was supported in part by the institution’s research fund (grant 14-2014-001). We received no specific grant from any other funding agency in the public, commercial, or not-for profit sectors. The authors thank the Medical Research Collaborating Center at Seoul National University Bundang Hospital for statistical analyses. REFERENCES 1. Bickel KD. Carpal tunnel syndrome. J Hand Surg Am. 2010;35(1): 147e152. 2. Pellegrini VD Jr. Osteoarthritis at the base of the thumb. Orthop Clin North Am. 1992;23(1):83e102. 3. Armstrong AL, Hunter JB, Davis TR. The prevalence of degenerative arthritis of the base of the thumb in post-menopausal women. J Hand Surg Br. 1994;19(3):340e341. 4. Eaton RG, Littler JW. Ligament reconstruction for the painful thumb carpometacarpal joint. J Bone Joint Surg. 1973;55(8):1655e1666. 5. Moore JR, Tolo VT, Weiland AJ. Painful subluxation of the carpometacarpal joint of the thumb in Ehlers-Danlos syndrome. J Hand Surg Am. 1985;10(5):661e663. 6. Gamble JG, Mochizuki C, Rinsky LA. Trapeziometacarpal abnormalities in Ehlers-Danlos syndrome. J Hand Surg Am. 1989;14(1): 89e94. 7. Bettinger PC, Linscheid RL, Berger RA, Cooney WP, An K-N. Trapezial tilt: a radiographic correlation with advanced trapeziometacarpal joint arthritis. J Hand Surg Am. 2001;26(4):692e697. 8. Kurosawa S, Tsuchiya I, Takagishi K. Trapezial-metacarpal joint arthritis: radiographic correlation between first metacarpal articular tilt and dorsal subluxation. J Hand Surg Am. 2013;38(2):302e308. 9. Halilaj E, Moore DC, Laidlaw DH, et al. The morphology of the thumb carpometacarpal joint does not differ between men and women, but changes with aging and early osteoarthritis. J Biomech. 2014;27(11): 2709e2714. 10. Wolf JM, Scher DL, Etchill EW, et al. Relationship of relaxin hormone and thumb carpometacarpal joint arthritis. Clin Orthop Relat Res. 2014;472(4):1130e1137. 11. Jónsson H, Elíasson GJ, Jónsson A, et al. High hand joint mobility is associated with radiological CMC1 osteoarthritis: the AGESReykjavik study. Osteoarthritis Cartilage. 2009;17(5):592e595. 12. Florack TM, Miller RJ, Pellegrini VD, Burton RI, Dunn MG. The prevalence of carpal tunnel syndrome in patients with basal joint arthritis of the thumb. J Hand Surg Am. 1992;17(4):624e630. 13. Melone CP Jr, Beavers B, Isani A. The basal joint pain syndrome. Clin Orthop Relat Res. 1987;220:58e67. 14. Cassidy C, Glennon PE, Stein AB, Ruby LK. Basal joint arthroplasty and carpal tunnel release through a single incision: an in vitro study. J Hand Surg Am. 2004;29(6):1085e1088. 15. Shin CH, Paik NJ, Lim JY, et al. Carpal tunnel syndrome and radiographically evident basal joint arthritis of the thumb in elderly Koreans. J Bone Joint Surg Am. 2012;94(16):e1201ee1206. 16. Johansson H, Sjölander P, Sojka P. A sensory role for the cruciate ligaments. Clin Orthop Relat Res. 1991;268:161e178. 17. Michelson JD, Hutchins C. Mechanoreceptors in human ankle ligaments. J Bone Joint Surg Br. 1995;77(2):219e224. 18. Sjölander P, Johansson H, Djupsjöbacka M. Spinal and supraspinal effects of activity in ligament afferents. J Electromyogr Kinesiol. 2002;12(3):167e176.
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