Chopstick Arthropathy

Transcription

1 ARTHRITIS & RHEUMATISM Vol. 50, No. 5, May 2004, pp DOI /art , American College of Rheumatology Chopstick Arthropathy The Beijing Osteoarthritis Study David J. Hunter, 1 Yuqing Zhang, 1 Michael C. Nevitt, 2 Ling Xu, 3 Jingbo Niu, 1 Li-Yung Lui, 2 Wei Yu, 3 Piran Aliabadi, 4 and David T. Felson 1 Objective. Several investigators have speculated that mechanical stress might play an important role in the development of hand osteoarthritis (OA). Chopsticks, used universally as eating utensils in China, increase joint loading in the first through third fingers. We conducted a population-based survey among elderly Chinese individuals living in Beijing, to explore whether chopsticks use is associated with prevalent hand OA. Methods. We recruited a sample of persons ages 60 years and older, using door-to-door enumeration in randomly selected neighborhoods in Beijing. Subjects answered questions about the hand with which they use chopsticks, handedness, and pincer grip activities. Bilateral posteroanterior hand radiographs were obtained, and each joint was graded according to the Kellgren/Lawrence (K/L) scale. We defined a subject as having radiographic OA if at least 1 of his or her hand joints had radiographic OA (K/L score of >2). We defined a particular hand group (i.e., distal interphalangeal [DIP] joints, proximal interphalangeal [PIP] joints, or metacarpophalangeal [MCP] joints) as having OA if at least 1 joint of the group had radiographic OA. We calculated the prevalence of OA for each hand joint and, according to the status of chopsticks use, performed a matched analysis to examine the relationship between chopsticks use and the prevalence of hand Supported by NIH grants AR and AR David J. Hunter, MD, PhD, Yuqing Zhang, DSc, Jingbo Niu, MD, David T. Felson, MD, MPH: Boston University Arthritis Center, and Boston Medical Center, Boston, Massachusetts; 2 Michael C. Nevitt, PhD, Li-Yung Lui, MS: University of California, San Francisco; 3 Ling Xu, MD, Wei Yu, MD: Peking Union Medical College Hospital, Beijing, China; 4 Piran Aliabadi, MD: Brigham and Women s Hospital, Boston, Massachusetts. Address correspondence and reprint requests to David J. Hunter, PhD, A203, Boston University School of Medicine, 715 Albany Street, Boston, MA djhunter@bu.edu. Submitted for publication September 29, 2003; accepted in revised form January 5, OA. In the analysis, we excluded persons who reported a previous hand injury. Because most subjects used chopsticks with their dominant hand (a hand they would be expected to use more for all manual tasks), we also performed the analysis among subjects who reported that they had no hand preference when performing other activities and subjects who denied other pincer grip activities. Results. A total of 1,008 men and 1,499 women were assessed. The prevalence ratio for OA of the thumb IP joint in the chopsticks hand was 1.2 (range ) in men and 1.6 (range ) in women; the prevalence ratio for OA of the second and third PIP joints was 1.5 (range ) in men and 1.4 (range ) in women; and the prevalence ratio for OA of the second and third MCP joints was 1.4 (range ) in men and 1.4 (range ) in women. The prevalence ratios in these joints were greater than the ratios in other MCP, PIP, or DIP joints from the same hand that were unlikely to be involved by chopsticks use, especially among women. Similar results were observed when the analyses were limited to ambidextrous subjects and subjects who did not engage in any other pincer grip activities. Thumb IP joint OA affected 26% of the entire population studied, and chopsticks use accounted for 19% of the risk of OA developing in this joint in men and 36% of the risk in women. Conclusion. This epidemiologic study investigated the relationship of chopsticks use to hand arthropathy. The results suggest that chopsticks use is associated with an increased prevalence of OA in the IP joint of the thumb, and in the second and third PIP and MCP joints. Chopsticks were developed 5,000 years ago in China. Confucius advised people not to use knives at the table, because knives would remind them of the slaugh- 1495

2 1496 HUNTER ET AL terhouse. Chopsticks are usually 9 10 inches long and rectangular, with a blunt end. By AD 500, chopsticks use had spread from China to present-day Vietnam, Korea, and Japan. It is estimated that 1.5 billion people worldwide use chopsticks every day. Most Chinese people learn to use chopsticks with their dominant hand starting at age 3 4 years, and few switch their hand of chopsticks use in their lifetime. Although the mode of operation of chopsticks varies, the predominant fingers involved remain the thumb, the index finger, and the middle finger (1,2). Several investigators have speculated that mechanical stress might play an important role in the development of hand osteoarthritis (OA). In China, exposure to the use of chopsticks is potentially an important source of mechanical stress. The notion that specific physical activities that involve repeated hand use may predispose to the development of OA through joint overload is supported by a number of research findings. For example, hemiparesis reduces ipsilateral expression of hand OA, while OA is accentuated in the hand without paralysis (3). Handedness produces asymmetry in loading; however, investigations of its influence on the pattern of disease have not produced consistent results (4,5). Among middle-aged female textile workers, hand OA developed in joints that were overused (6), with OA in the distal interphalangeal (DIP) joints developing in women whose jobs involved repeated pincer grip (i.e., the thumb and fingers are pressed together at their tips to hold an object). This activity is similar to chopsticks use. Radiographic hand OA affects 45% of elderly Chinese individuals (7). When symptomatic, hand OA is associated with functional impairment (8,9). Few modifiable risk factors have been identified, but characterizing modifiable risk factors for this condition is important if we are to reduce its health burden. We undertook an analysis of a population-based survey of elderly Chinese individuals living in Beijing, to explore whether chopsticks use is associated with prevalent hand OA. Chopsticks use is associated with increased loading of joints in the thumb and the second and third digits (1,2), which are used to pinch the chopsticks. We hypothesized that chopsticks use would predispose to a particular pattern of arthritis because of specific loading of these fingers. PATIENTS AND METHODS The Beijing OA Study. The study design has been described in detail previously (10). Briefly, we recruited a random sample of men and women ages 60 years or older from 4 central districts of Beijing, China. Surveys and examinations. Subjects were interviewed at their homes. Trained health professional interviewers administered a standardized questionnaire that focused on joint symptoms and possible risk factors for OA. At the end of the interview, subjects were invited to the central examination site at Peking Union Medical College Hospital for a clinical examination, laboratory testing, and radiography. Transportation to the hospital was provided. The interview-administered survey included questions on chopsticks use and handedness. Information about chopsticks use was obtained by inquiring, Which hand do you usually use to hold chopsticks? The choices were right hand, right and left hands equally, left hand, unable to use hands, and do not know. Hand dominance was assessed by the following question: For the majority of activities you do, which of the following best describes which hand is used? The choices were right hand, right and left hands equally, left hand, unable to use hands, and do not know. Pincer grip activity was assessed by demonstrating a pinch grip (by pressing the tips of the index and middle fingers against the tip of the thumb) and inquiring about activities that were performed for an hour or more every day or nearly every day, including writing, calligraphy, sewing, knitting, handling paper, and other activities requiring use of a pinch grip. Exposure was quantified in the number of hours per day and the number of years during which the subject did this activity. Radiographs. Posteroanterior hand radiographs were obtained, with separate exposures for each hand, with the central ray on the third metacarpophalangeal (MCP) joint. Each radiograph was read by a single academically based bone and joint radiologist according to the reading protocols of the Framingham OA study (11). Fifteen joints for each hand, including 4 DIP, 4 proximal interphalangeal (PIP), 5 MCP, thumb IP, and base of thumb joints, were evaluated for the presence of osteophytes, joint space narrowing, sclerosis, and cysts. Each joint was graded for overall radiographic OA using a modified Kellgren/Lawrence (K/L) scale (12) graded 0 4, where 0 none, 1 questionable osteophyte(s) and/or questionable joint space narrowing, 2 definite small osteophyte(s), 3 definite moderate osteophyte(s) and joint space narrowing, and 4 large osteophyte(s) and severe joint space narrowing (cysts or sclerosis may be present). The weighted kappa on the K/L grade for intrareader reliability was 0.77 (95% confidence interval [95% CI] ). Statistical analysis. If the subject had at least 1 hand joint with radiographic OA, he or she was classified as having radiographic hand OA (K/L grade of 2). We defined a particular hand group (i.e., DIP, PIP, or MCP) as having radiographic OA if at least 1 joint of that joint group had radiographic OA. We calculated the prevalence of OA for each hand according to chopsticks use. Except for joint injury and handedness, all other risk factors, such as age, sex, body mass index, and education, were perfectly matched between 2 hands. Therefore, we performed a matched analysis to assess the relationship between chopsticks use and the prevalence of OA for various hand joint groups. We calculated prevalence ratios and 95% CIs by the Mantel-Haenszel method. For the analysis, we excluded 124 subjects (5%) who had a history of

3 CHOPSTICK ARTHROPATHY 1497 Table 1. Characteristics of study population* Characteristic Men (n 1,008) Women (n 1,499) Age, mean SD (range) years (59 95) (59 93) Prevalence of radiographic hand OA Distal interphalangeal joint Proximal interphalangeal joint Metacarpophalangeal joint Thumb base Thumb interphalangeal joint Previous hand injury Dominant hand Right Left Both Chopsticks-use hand Right Left Both * Except where indicated otherwise, values are the percent. OA osteoarthritis. hand injury. We further delineated hand joint categories by defining non chopsticks joints as joints of the fourth and fifth fingers that are unlikely to be affected by chopsticks use (i.e., the DIP, PIP, and MCP joints of the fourth and fifth fingers). Because most subjects used chopsticks with their dominant hand, it was difficult to sort out the effect of handedness and chopsticks use. We also performed the analysis among ambidextrous subjects who reported that they had no hand preference when performing other activities. It may be that risk in the joints affected by chopsticks use could also be influenced by other pincer grip activities. We performed further analysis among subjects who reported that they did not perform other pincer grip activities, to determine whether the effect was maintained. We estimated the impact of chopsticks use using attributable risk percentage, which was defined as follows: the prevalence of OA in the chopsticks use hand minus the prevalence of OA in the non chopsticks use hand divided by the prevalence of OA in the chopsticks use hand. RESULTS Characteristics of participants in the Beijing OA Study are presented in Table 1. The prevalence of radiographic OA in specific joint groups ranged from 7% for PIP joint OA in men to 26.4% for thumb IP joint OA in men. DIP and PIP joint OA were more common in women, reflecting the influence of sex on the occurrence of arthritis in these joints. Twenty-nine percent of men and 33% of women were ambidextrous. Ninetythree percent of men and 94% of women used chopsticks with their right hand. Table 2 shows the relationship between chopsticks use and the prevalence of hand OA in elderly men and women. In both sexes, radiographic OA was more common in the IP joint of the thumb and in the second and third PIP and MCP joints of the hand using chopsticks than in the hand not using chopsticks. In women, the second and third DIP joints also appeared to be affected by chopsticks use. Also, in women, the OA prevalence ratios in these joints were greater than those found in other MCP, PIP, or DIP joints of the same hand that were unlikely to be affected by chopsticks use. The effect was maximal in the thumb IP joint. Thumb IP joint OA affected 26% of this elderly Chinese population, and chopsticks use accounted for 19% of the prevalence of thumb IP joint OA in men and 36% of that observed in women. The prevalence ratio estimates for different K/L grades were similar to those found when considering K/L grades of 2, although the confidence limits around these estimates were wider and often included the null value of 1.0 as a result of the smaller numbers in these groups (results not shown). To further explore the possibility that this effect was mediated by dominant-hand use, we limited our analysis to subjects who were ambidextrous. In the subgroup of ambidextrous individuals, results for the chopsticks hand were the same as the results for the chopsticks hand in the whole study population (Table 3). The magnitude of the effect of chopsticks use on OA of the thumb IP joint and the second and third PIP joints was similar to that obtained in the whole sample. However, the confidence intervals were wider due to relatively small sample size. The effect on the second and third MCP joints was somewhat smaller in ambidextrous subjects than that in the entire sample. It is

4 1498 HUNTER ET AL Table 2. Association between chopsticks use and prevalence of radiographic hand OA among Beijing elderly Chopsticks-use hand Non chopsticks-use hand Joint group No. of hands Prevalence, % No. of hands Prevalence, % Prevalence ratio (95% CI) Men Thumb IP joint ( ) First MCP joint ( ) Second and third MCP joints ( ) Second and third DIP joints ( ) Second and third PIP joints ( ) Thumb base ( ) Non chopsticks-use joints ( ) Women Thumb IP joint ( ) First MCP joint ( ) Second and third MCP joints ( ) Second and third DIP joints ( ) Second and third PIP joints ( ) Thumb base ( ) Non chopsticks-use joints ( ) *OA osteoarthritis; 95% CI 95% confidence interval; IP interphalangeal; MCP metacarpophalangeal; DIP distal interphalangeal; PIP proximal interphalangeal. possible that pincer grip activities other than chopsticks use may produce this effect. However, further analysis of subjects who reported no other pincer grip activities revealed results in the chopsticks hand (Table 3) that were similar to those observed for the whole sample and for ambidextrous subjects. DISCUSSION Our study results suggest that, especially in women, chopsticks use predisposes to hand OA affecting primarily the IP joint of the thumb and the second and third PIP and MCP joints. In women, hand OA was Table 3. Relationship of chopsticks use to prevalence of radiographic hand OA* Joint group Ambidextrous subjects Subjects reporting no other pincer grip activity Men Thumb IP joint 1.1 ( ) 1.1 ( ) First MCP joint 1.1 ( ) 1.2 ( ) Second and third MCP joints 1.2 ( ) 1.4 ( ) Second and third DIP joints 0.8 ( ) 0.9 ( ) Second and third PIP joints 2.0 ( ) 2.0 ( ) Thumb base 0.8 ( ) 0.7 ( ) Non chopsticks-use joints 1.5 ( ) 1.2 ( ) Women Thumb IP joint 1.5 ( ) 1.7 ( ) First MCP joint 0.8 ( ) 4.0 ( ) Second and third MCP joints 1.2 ( ) 1.5 ( ) Second and third DIP joints 1.1 ( ) 1.4 ( ) Second and third PIP joints 1.5 ( ) 1.5 ( ) Thumb base 0.8 ( ) 0.6 ( ) Non chopsticks-use joints 1.1 ( ) 1.1 ( ) * Values are the prevalence ratios (95% confidence intervals). For men, n 266 ambidextrous subjects and 381 subjects with no pincer grip activity. For women, n 478 ambidextrous subjects and 391 subjects with no pincer grip activity. See Table 2 for definitions.

5 CHOPSTICK ARTHROPATHY 1499 more prevalent in these joints and in the second and third DIP joints than in other MCP, PIP, or DIP joints of the same hand that were unlikely to be involved by chopsticks use. This pattern of hand joint involvement is unlikely to be the result of dominant-hand use predisposing to hand OA. The effect was similar among ambidextrous subjects and those who did not perform other pincer grip activities, suggesting that it is unlikely that the effect is being mediated through hand dominance or excess use of these hands for other activities. We hypothesize that mechanical stress is the likely mechanism. Previous studies of occupational groups exposed to repetitive use of small hand joints demonstrated an excess of hand OA in joints that were used repetitively (6,13,14). In the classic surveys performed by Lawrence, coal miners were shown to have more OA than dock workers who, in turn, had more OA than office workers (14). Different types of hand function may predispose to OA in different articular areas, with studies of repeated pincer grip and generally increased workload demonstrating a predisposition to DIP joint OA (6,15,16). In contrast, a higher maximal grip strength increases the risk for development of OA in more proximal hand joints (the PIP, MCP, and thumb base joints in men, and the MCP joints in women) (17). Why did we find a relationship between chopsticks use and hand OA in women, while the relationship was not so clear in men, in whom non chopsticks joints in the dominant hand also showed a high prevalence of OA? We suggest that this is because women do not do as much heavy labor as men, and that the general increase in dominant-hand OA in men is a consequence of this heavy labor. In the past, we noted a high prevalence of MCP joint OA in Chinese individuals compared with the prevalence in US men (7), and this joint is known to be especially affected by heavy labor (18). In women, chopsticks use may represent the major loading across these hand joints, whereas in men, there are many such loads over the chopsticks-using joints and other hand joints. Based on our results, we hypothesize that the grip used to hold chopsticks produces excessive loads on the thumb IP joint and on the second and third DIP, PIP, and MCP joints and, in addition, unloads the thumb base. The typical mode of chopsticks use produces a flexed posture of the involved fingers. The majority of this flexion occurs at the thumb IP joint and the second and third PIP and MCP joints, as opposed to the straight position of the first MCP joint. Loading in a flexed position lengthens the lever arms of some muscles loading the digit joints and, in this way, is analogous to the bending and mechanical loading of squatting, a posture that is known to accelerate development of knee OA (19). The protective effect of chopsticks use upon base-of-thumb OA is intriguing. We surmise that the grip used during chopsticks use unloads the first carpometacarpal (CMC) joint. We hypothesize that the first CMC joint is a hinge about which the 2 curved lever arms apply a net traction, thus unloading this joint selectively. This study is associated with a number of advantages. Most risk factors (i.e., metabolic factors, sociodemographic factors) were perfectly controlled due to matching that compared one hand with the other within each person. Because the prevalence of hand OA is much lower in Chinese than in whites (7), and because the effect of chopsticks use on hand OA may be relatively small, elderly Chinese individuals provided a unique opportunity to investigate this weak association (20). It is very likely that cumulative exposure plays an important role in the risks of mechanical stress. We studied elderly Chinese individuals who started using chopsticks when they were very young, thus providing a long duration of exposure to this risk factor. Furthermore, although this is a cross-sectional study, the exposure (i.e., chopsticks use) is unlikely to change due to hand OA status. This study also has certain limitations. We could not entirely rule out residual confounding of dominanthand use. However, for several reasons, if such an effect exists the impact is not likely to be substantial. First, similar results were observed in the chopsticks hand of ambidextrous subjects. Second, there were differences within dominant hands between joints affected by chopsticks use and joints unlikely to be affected by the use of chopsticks, especially in women. Last, exploration of other hand physical activities that could produce a risk in the more dominant hand, including pincer grip activities, digging, and heavy lifting, did not suggest a risk from these activities. In conclusion, we have described a pattern of hand arthropathy possibly resulting from the use of chopsticks. Although the increase in prevalence associated with chopsticks use is small, this accounts for a large proportion of the OA in these joint groups. It is important to state that our investigation was of radiographic OA and not symptomatic OA. Thus, we do not know whether the effects we report have implications for symptomatic disease. We recommend further biomechanical research to evaluate the forces involved in

6 1500 HUNTER ET AL chopsticks use. Based on these analyses, it may be possible to design more ergonomically favorable chopsticks or a preferable mode of chopsticks operation. ACKNOWLEDGMENT We thank the participants of the Beijing Osteoarthritis Study. REFERENCES 1. Chang JJ, Chien TH, Lin YT. Comparison of various patterns of chopsticks use and functional performance. Gaoxiong Yi Xue Ke Xue Za Zhi 1993;9: Chen YL. Effects of shape and operation of chopsticks on food-serving performance. Appl Ergon 1998;29: Segal R, Avrahami E, Lebdinski E, Habut B, Leibovitz A, Gil I, et al. The impact of hemiparalysis on the expression of osteoarthritis. Arthritis Rheum 1998;41: Lane NE, Bloch DA, Jones HH, Simpson U, Fries JF. Osteoarthritis in the hand: a comparison of handedness and hand use. J Rheumatol 1989;16: Acheson RM, Chan YK, Clemett AR. New Haven survey of joint diseases. XII. Distribution and symptoms of osteoarthrosis in the hands with reference to handedness. Ann Rheum Dis 1970;29: Hadler NM, Gillings DB, Imbus HR, Levitin PM, Makuc D, Utsinger PD, et al. Hand structure and function in an industrial setting. Arthritis Rheum 1978;21: Zhang Y, Xu L, Nevitt MC, Niu J, Goggins JP, Aliabadi P, et al. Lower prevalence of hand osteoarthritis among Chinese subjects in Beijing compared with white subjects in the United States: the Beijing Osteoarthritis Study. Arthritis Rheum 2003;48: Zhang Y, Niu J, Kelly-Hayes M, Chaisson CE, Aliabadi P, Felson DT. Prevalence of symptomatic hand osteoarthritis and its impact on functional status among the elderly: The Framingham Study. Am J Epidemiol 2002;156: Cunningham LS, Kelsey JL. Epidemiology of musculoskeletal impairments and associated disability. Am J Public Health 1984; 74: Zhang Y, Xu L, Nevitt MC, Aliabadi P, Yu W, Qin M, et al. Comparison of the prevalence of knee osteoarthritis between the elderly Chinese population in Beijing and whites in the United States: the Beijing Osteoarthritis Study. Arthritis Rheum 2001;44: Chaisson CE, Zhang Y, McAlindon TE, Hannan MT, Aliabadi P, Naimark A, et al. Radiographic hand osteoarthritis: incidence, patterns, and influence of pre-existing disease in a population based sample. J Rheumatol 1997;24: Kellgren JH, Lawrence JS. Radiological assessment of osteoarthrosis. Ann Rheum Dis 1957;16: Kellgren JH, Lawrence JS. Rheumatism in miners. Part II. X-ray study. Br J Indust Med 1952;9: Lawrence J. Rheumatism in cotton operatives. Br J Indust Med 1961;18: Bergenudd H, Lindgarde F, Nilsson B. Prevalence and coincidence of degenerative changes of the hands and feet in middle age and their relationship to occupational work load, intelligence, and social background. Clin Orthop 1989;239: Nakamura R, Ono Y, Horii E, Tsunoda K, Takeuchi Y. The aetiological significance of work-load in the development of osteoarthritis of the distal interphalangeal joint. J Hand Surg [Br] 1993;18: Chaisson CE, Zhang Y, Sharma L, Felson DT. Higher grip strength increases the risk of incident radiographic osteoarthritis in proximal hand joints. Osteoarthritis Cartilage 2000;8 Suppl A:S Williams WV, Cope R, Gaunt WD, Adelstein EH, Hoyt TS, Singh A, et al. Metacarpophalangeal arthropathy associated with manual labor (Missouri metacarpal syndrome): clinical radiographic, and pathologic characteristics of an unusual degeneration process. Arthritis Rheum 1987;30: Cooper C, McAlindon T, Coggon D, Egger P, Dieppe P. Occupational activity and osteoarthritis of the knee. Ann Rheum Dis 1994;53: Rothman KJ, Poole C. A strengthening programme for weak associations. Int J Epidemiol 1988;17:955 9.