Impact of Hallux Valgus Severity on General and Foot-Specific Health-Related Quality of Life

Transcription

1 Arthritis Care & Research Vol. 63, No. 3, March 2011, pp DOI /acr , American College of Rheumatology ORIGINAL ARTICLE Impact of Hallux Valgus Severity on General and Foot-Specific Health-Related Quality of Life HYLTON B. MENZ, 1 EDWARD RODDY, 2 ELAINE THOMAS, 2 AND PETER R. CROFT 2 Objective. To explore the prevalence of and factors associated with hallux valgus and to assess the impact of hallux valgus severity on general and foot-specific health-related quality of life (HRQOL) in older people. Methods. People age >56 years who participated in the 6-year followup of the North Staffordshire Osteoarthritis Project (n 2,831) completed a survey that included the Medical Outcomes Study Short Form 36 (SF-36) health survey and the Manchester Foot Pain and Disability Index (FPDI). Self-reported hallux valgus severity was assessed using a validated instrument. Comparisons of SF-36 and FPDI scores were made across 5 severity grades of hallux valgus. Results. Hallux valgus was present in 36.3% of the study population and was associated with female sex, older age, and pain in other bodily regions. There was a progressive reduction in all SF-36 component scores as the severity of hallux valgus increased; this association remained after adjusting for age, sex, education, and body mass index. The strength of these associations diminished after also adjusting for pain in the back, hip, knee, and foot, but hallux valgus severity remained significantly associated with reduced physical function, bodily pain, general health, social function, and mental health subscale scores. Among participants with foot pain, increasing hallux valgus severity was also significantly associated with greater impairment on the pain and function subscales of the FPDI after adjusting for age, sex, and body mass index. Conclusion. There is a progressive reduction in both general and foot-specific HRQOL with increasing severity of hallux valgus deformity. INTRODUCTION Hallux valgus is a common condition affecting the forefoot in which the first metatarsophalangeal joint is progressively subluxed due to lateral deviation of the hallux and medial deviation of the first metatarsal (1,2). The condition is frequently accompanied by a painful soft tissue and osseous prominence, commonly referred to as a bunion, on the medial aspect of the first metatarsal head. As the deformity progresses, the lateral displacement of the hallux interferes with the normal alignment and function of Supported by the Medical Research Council (grants G and G ) and the North Staffordshire Primary Care Research and Design Consortium. 1 Hylton B. Menz, PhD: Keele University, Keele, UK, and La Trobe University, Bundoora, Victoria, Australia; 2 Edward Roddy, DM, Elaine Thomas, PhD, Peter R. Croft, MD: Keele University, Keele, UK. Dr. Menz is an Australian National Health and Medical Research Council Fellow, and this work was conducted as part of an Arthritis Research UK National Primary Care Centre Visiting Fellowship. Address correspondence to Hylton B. Menz, PhD, Musculoskeletal Research Centre, Faculty of Health Services, La Trobe University, Bundoora, Victoria 3086, Australia. E- mail: h.menz@latrobe.edu.au. Submitted for publication May 2, 2010; accepted in revised form October 27, the lesser toes, resulting in hammer toe or claw toe deformities, altered weight-bearing patterns, and the development of plantar keratotic lesions (corns and calluses) (3). Pressure from footwear may also lead to the formation of an adventitious bursa over the joint that may become inflamed and painful (4). The cause of hallux valgus is not well understood. There is some evidence that the condition is an autosomal dominant trait with partial penetrance, since 90% of people with hallux valgus report a positive family history (5,6). Other contributing factors include wearing shoes with an elevated heel and narrow toe box, structural factors such as excessively long first metatarsals, round metatarsal heads, and large intermetatarsal angle, and pronated foot posture (7). However, because hallux valgus may take several decades to develop, no prospective risk factor studies have so far been undertaken. Prevalence estimates based on surveys in samples from the general population of adults in different countries using varying definitions have yielded estimates ranging from 21 65% (8 14). The largest study so far undertaken of a general population sample (involving 4,249 people age 30 years) reported a prevalence of 28% (15). Women are significantly more likely to develop hallux valgus as compared with men (1,2,13 17), with sex ratios as high as 9:1 (1,2,13 17), and the prevalence of hallux valgus increases 396

2 Health-Related Quality of Life and Hallux Valgus 397 steadily with age (15). The condition has a significant impact on balance (18) and gait patterns (19), and is a risk factor for falls in older people (20,21). Three studies have also demonstrated that people with hallux valgus exhibit significantly lower scores on health-related quality of life (HRQOL) questionnaires (22 24), suggesting that the condition has a much broader impact than local pain and discomfort. A large proportion of people with the condition undergo surgery to correct the deformity, making it the most commonly performed orthopedic foot and ankle procedure (25,26). One of the limitations of the available literature on hallux valgus is that it has generally been classified as simply being present or absent. This is problematic, not only because different case definitions have been used (involving simple clinical observation [9,12,13] or self-report [8,10,11]), but also because the degree of deformity varies considerably. Although there are now 2 validated clinical assessment tools that enable the severity of the deformity to be documented (using either 4- or 5-level classifications [27,28]), these scales have generally been dichotomized prior to analysis. To the best of our knowledge, the only study to examine hallux valgus across multiple levels of severity used simple visual observation and focused on radiographic correlates (29). Therefore, there remains a need to assess the impact of hallux valgus, taking into account the severity of the deformity, since more severe forms of the condition are likely to have a greater impact on HRQOL. Furthermore, there is a need to determine the relative impact of the condition on general HRQOL (as indicated by generic HRQOL scales) as opposed to HRQOL related specifically to foot impairment. Therefore, the aims of this study are to explore the prevalence of and factors associated with hallux valgus and to assess the impact of hallux valgus severity on general and foot-specific HRQOL in a large community-based sample of older people. SUBJECTS AND METHODS Participants. Participants were drawn from the 6-year followup of the North Staffordshire Osteoarthritis Project (NORSTOP), the details of which have been described elsewhere (30). In summary, the baseline sampling frame consisted of all adults age 50 years registered with 3 general practices (n 11,309) from the North Staffordshire Primary Care Research Consortium. The samples were then checked by the general practitioners (GPs) for exclusions (for example, severe psychiatric or terminal illness) and 79 people were excluded prior to baseline mailing (55 deaths or departures and 24 GP exclusions). Questionnaires were mailed with a letter from the GP practice, accompanied by a study information leaflet, and reminders were sent to nonresponders after 2 and 4 weeks. In the UK, more than 95% of people are registered with a general practice, so general practice registers provide a convenient frame for sampling a local population (31). Adjusted response rates of 71.3% (n 7,878) and 84.7% (n 4,234) at baseline and 3-year followup, respectively, were obtained (32). The 6-year followup consisted of a 2-stage mailing, a health survey questionnaire, and a subsequent regional pains survey questionnaire, for those giving permission for re-contact and reporting pain in their hands, knees, hips, or feet in the previous 1-year period on the health survey questionnaire. Ethical approval for the 6-year followup was provided by the North Staffordshire Research Ethics Committee. Health survey questionnaire. This questionnaire collected information, including sociodemographics (age, sex, and education level), anthropometrics (height, weight, and body mass index [BMI]), completion of higher education (using the question, Did you go from school to fulltime education or university? ), and bodily pain. The question used to ascertain bodily pain was, In the past four weeks, have you had pain that lasted for one day or longer in any part of your body? and was followed by instructions to shade in the location of pain on a full-body paper manikin, with the front and back of the body depicted. General HRQOL was assessed using the Medical Outcomes Study Short Form 36 (SF-36) subscales (33). Self-reported hallux valgus was assessed using a validated line-drawing instrument depicting varying degrees of the condition (28). The instrument consists of 5 drawings for each foot, with each drawing illustrating a sequential increase in the hallux valgus angle of 15 degrees. The drawings were accompanied by instructions for participants to compare the line drawings to their own bare feet while standing and to select the picture that best represented their left and right feet in turn. Using this instrument, hallux valgus was documented in 2 different ways. First, hallux valgus was dichotomized for each foot by classifying the 3 most severe grades as present and the 2 least severe grades as absent (28). Second, hallux valgus severity was documented using each of the 5 ordinal categories for the left and right feet. Because the severity of hallux valgus may differ between feet in the same individual, participants were then categorized into 5 hallux valgus groups (hereafter referred to as 1, 2, 3, 4, or 5) depending on the severity of the deformity on their most severely affected foot. Since each line drawing illustrates an increase of 15 degrees in the hallux valgus angle, the 5 levels of severity approximate to hallux valgus angles are 0, 15, 30, 45, and 60 degrees. Regional pains survey questionnaire. Foot-specific HRQOL was documented using the Manchester Foot Pain and Disability Index (FPDI) (34) for those reporting foot pain in the previous 12 months. The FPDI consists of 19 statements beginning with the phrase Because of pain in my feet.... The statements have been found to cluster around 3 constructs: pain intensity (5 items), functional limitation (10 items), and concern with personal appearance (2 items) (34). The remaining 2 items relate to the difficulty in performing work or leisure activities, and, as had been done in previous studies (35), were excluded since many participants in the study were of retirement age. In a recent psychometric study, the pain and function items were found to fit the Rasch model (36), so the inter-

3 398 Menz et al val-level scores (where the scores are measured on a logit scale with higher scores representing greater levels of pain or functional limitation) derived from this study were employed in this analysis. The psychometric study was conducted using pilot study data from NORSTOP, an identically drawn sample from the same broad local population-sampling framework as supplied the sample for the main study (30). Statistical analysis. The analysis was undertaken in 2 stages. First, differences in demographic factors, BMI, comorbid pain, SF-36 domain scores, and pain and function subscales of the FPDI between those with and without hallux valgus (using the dichotomous case definition) were compared using independent-samples t-tests (for continuously-scored variables) and chi-square tests (for dichotomous variables). Second, mean SF-36 subscale scores across the 5 hallux valgus severity categories were compared using multivariate analysis of variance. For the SF-36 subscales, 4 models were developed: 1) unadjusted, 2) adjusted for age, sex, education, and BMI, 3) adjusted for age, sex, education, BMI, back pain, knee pain, and hip pain, and 4) adjusted for age, sex, education, BMI, back pain, knee pain, hip pain, and foot pain. Low scores on the SF-36 subscales are indicative of greater impairment. Among those people who reported foot pain in the last 12 months, mean SD FPDI subscale scores across the 5 hallux valgus severity categories were also compared using multivariate analysis of variance. For the FPDI pain and function subscales, 2 models were developed: 1) unadjusted and 2) adjusted for age, sex, education, and BMI. High scores on the FPDI are indicative of greater impairment. Colinearity of the models was assessed using the variance inflation factor (VIF) statistic for each covariate, with VIFs less than 5 considered to be acceptable (37). All analyses were performed using SPSS, version 15.0 for Windows. RESULTS Respondents. A flow chart of participants is provided in Figure 1. From the population of 4,234 adults who completed the 3-year followup survey, 3,596 gave permission for further contact. During the 3-year period between the surveys, 181 deaths had occurred and 5 exclusions were made by the GPs; therefore, 3,410 questionnaires were mailed. During the 3 mailing waves of the health survey questionnaire, 37 exclusions were made to the database, leaving an eligible study population of 3,373 adults. A total of 2,831 completed health survey questionnaires were returned, giving an adjusted response of 83.9%. The nonresponders were made up of 73 people who declined to participate, 40 people who stated ill health as the reason for not completing the questionnaire, and 429 people from whom no response was received. Of the 2,831 responders to the health survey questionnaire, 2,002 were eligible to receive the regional pains survey questionnaire and 1,756 (87.7%) responded. Respondents to the 6-year followup health survey questionnaire were more likely to be women (56.5%) compared with those excluded before and during mailing (39.0%) or not responding (53.7%; , 2 df, P 0.001). Age group was strongly related to 6-year status ( , 6 df, P 0.001). Nonresponders and responders who were ages years at recruitment were most likely to be in the youngest age group, while exclusions were most likely to occur in those age 70 years at recruitment. Response at the 6-year followup was also significantly related to the SF-12 mental (F[2,3201] 15.2, P 0.001) and physical (F[2,3201] 60.3, P 0.001) scores recorded at 3 years; higher scores on both scales were seen for those responding at the 6-year followup, while the lowest scores were seen for those excluded. There were no differences in those who completed the health survey (n 2,831) and those who completed the regional pains survey and hallux valgus tool (n 1,030) in relation to mean SD age ( years versus years; t[3,859] 0.0, P 1.00) or sex (56.4% versus 60.2% women; 2 2.7, 1 df, P 0.10). Prevalence and correlates of hallux valgus. Of the 2,681 respondents to the health survey who completed the self-report hallux valgus instrument, the prevalence of hallux valgus using the dichotomous case definition was 36.3%, was greater in women, and increased with age (Figure 2). The demographics, presence of bodily pain, and SF-36 scores for those with and without hallux valgus are shown in Table 1. Those with hallux valgus were significantly older, were more likely to be women, were shorter, weighed less, had a lower BMI, were more likely to report any bodily pain (and pain in the low back, hip, knee, and foot), and exhibited lower scores (indicative of greater impairment) on each of the subscales of the SF-36. Of the 1,030 responders to the regional pains survey who reported foot pain in the past 12 months, those with hallux valgus also exhibited higher scores (indicative of greater impairment) on both the pain and function subscales of the FPDI. Hallux valgus was unilateral in 41% of cases and bilateral in 59% of cases. Participants with bilateral hallux valgus exhibited greater impairment than those with unilateral hallux valgus, as evidenced by lower scores on the physical function, bodily pain, and general health subscales of the SF-36, and higher scores on the pain and function subscales of the FPDI (data not shown). Impact of hallux valgus severity on general HRQOL. Figure 3 shows the mean (95% confidence interval) SF-36 subscale scores across the 5 levels of hallux valgus severity. There was a significant downward trend in all SF-36 subscale scores as hallux valgus severity increased, which remained significant (P 0.001) after adjusting for age, sex, education, and BMI. A similar pattern was evident after also adjusting for back pain, hip pain, and knee pain, although the association with the role-emotional subscale was no longer significant. After additionally adjusting for foot pain, the association with the role-physical and roleemotional subscales was no longer significant (Table 2). There was no evidence of multicolinearity between covariates for any of the models (VIF 2 for all independent variables).

4 Health-Related Quality of Life and Hallux Valgus 399 Respondents to baseline Health Survey n=7,878 (response rate=71.3%) Respondents to 3 year follow-up Health Survey n=4,234 (response rate=84.7%) Respondents to 3 year follow-up Health Survey consenting to further contact n=3,596 (84.9%) Excluded prior to mailing (n=189) deaths -5GPexclusions Mailed 6 year follow-up Health Survey n=3,410 Excluded during mailing (n=37) Eligible 6 year Health Survey population n=3,373 Non-respondents (n=542) - 73 declined to participate -40illhealth no response Completed 6 year Health Survey n=2,831 (response rate=83.9%) Completed hallux valgus tool n=2,681 (94.7%) Sample for general health-related quality of life analysis with SF-36 Eligible to receive Regional Pains Survey n=2,002 Completed Regional Pains Survey n=1,756 (response rate=87.7%) Reported foot pain in past 12 months, completed hallux valgus tool and FPDI n=1,030 (58.4%) Sample for foot-specific health-related quality of life analysis with FPDI Figure 1. Flow chart of participants through the North Staffordshire Osteoarthritis Project. GP general practitioner; SF-36 Medical Outcomes Short Form 36 Health Survey; FPDI Manchester Foot Pain and Disability Index. Impact of hallux valgus severity on foot-specific HRQOL. Figure 4 shows the mean FPDI subscale scores across the 5 levels of hallux valgus severity. There was a significant upward trend (indicative of greater impairment) in both the pain and function subscales as hallux valgus severity increased, which remained significant after adjusting for age, sex, education, and BMI (Table 3). There was no evidence of multicolinearity between covariates for any of the models (VIF 2 for all independent variables). DISCUSSION The first objective of this study was to explore the prevalence of, and factors associated with, hallux valgus deformity. Previous studies using a range of case definitions have reported prevalence estimates ranging from 21 65% (8 14). In this study, we used a validated self-report instrument and found the prevalence of hallux valgus to be 36.3% in community-based adults age 56 years. This

5 400 Menz et al Figure 2. Prevalence of hallux valgus (using the dichotomous case definition) by age and sex (n 2,681). Overall prevalence 36.3% (n 973). finding is consistent with Roddy et al (15), who examined 4,249 people age 30 years using the same instrument and reported an overall prevalence of 28%, with a prevalence between 30% and 50% in those people age 50 years. Consistent with previous reports, we also found that the prevalence of hallux valgus increased with age (15), was Figure 3. Unadjusted mean Medical Outcomes Short Form 36 (SF-36) Health Survey component scores by hallux valgus severity grade (worst foot). higher in women (13 17), and was associated with pain in other body regions (14,15). However, in contrast to some previous studies (14,38), we found that those with hallux valgus had a lower, not higher, BMI. Interestingly, in a recent study, Nguyen et al (17) reported that hallux valgus Table 1. Demographics and health-related quality of life according to dichotomous classification of hallux valgus* Characteristic Total sample (n 2,681) Hallux valgus (n 974) No hallux valgus (n 1,707) P Demographics Age at baseline, years Female, no. (%) 1,507 (56.2) 696 (71.5) 811 (47.5) Higher education, no. (%) 392 (14.9) 155 (16.3) 237 (14.1) Anthropometrics Height, cm Weight, kg Body mass index, kg/m Regional pains Any bodily pain, no. (%) 1,691 (74.5) 652 (80.9) 1,039 (70.9) Low back pain, no. (%) 1,114 (42.7) 469 (48.2) 675 (39.5) Hip pain, no. (%) 925 (34.5) 385 (39.5) 540 (31.6) Knee pain, no. (%) 1,081 (40.3) 442 (45.4) 639 (37.4) Foot pain, no. (%) 822 (30.7) 384 (39.4) 438 (25.7) SF-36 subscales Physical function Role-physical Bodily pain General health Vitality Social function Role-emotional Mental health Manchester Foot Pain and Disability Index subscales Pain Function * Values are the mean SD unless indicated otherwise and are subject to missing values, apart from age and sex; t-tests reported for continuously-scored variables and chi-square tests reported for dichotomous variables. SF-36 Medical Outcomes Study Short Form 36 Health Survey. At least 1 painful site marked on a full body manikin. Total for this analysis 1,030 (explanation in Results section).

6 Health-Related Quality of Life and Hallux Valgus 401 Table 2. SF-36 subscale scores across the 5 hallux valgus severity grades (n 2,681)* Hallux valgus severity grade (worst foot) 1 (n 511) 2 (n 1,196) 3 (n 739) 4 (n 178) 5 (n 57) P Model 1 Physical function 66.1 (63.7, 68.5) 65.2 (63.7, 66.9) 62.5 (59.4, 63.5) 55.8 (51.6, 60.0) 52.1 (44.8, 59.4) Role-physical 60.8 (57.0, 64.6) 55.8 (53.3, 58.3) 50.7 (47.5, 53.9) 45.6 (39.0, 52.2) 40.0 (28.4, 51.5) Bodily pain 61.0 (58.7, 63.3) 58.9 (57.4, 60.4) 54.4 (52.5, 56.4) 50.6 (46.6, 54.6) 44.5 (37.6, 51.5) General health 62.8 (60.9, 64.7) 60.3 (59.0, 61.5) 57.6 (55.9, 59.1) 54.5 (51.2, 57.8) 51.4 (45.6, 57.2) Vitality 57.1 (55.1, 59.0) 55.9 (54.6, 57.2) 52.2 (50.6, 53.9) 49.6 (46.2, 53.0) 43.7 (37.8, 49.7) Social function 78.4 (76.0, 80.9) 78.1 (76.5, 79.7) 74.3 (72.2, 76.3) 70.1 (65.9, 74.3) 62.2 (54.9, 69.5) Role-emotional 75.0 (71.4, 78.7) 73.9 (71.5, 76.2) 70.4 (67.3, 73.5) 65.1 (58.8, 71.4) 65.6 (54.5, 76.5) Mental health 75.6 (73.9, 77.2) 74.8 (73.7, 75.8) 71.5 (70.2, 73.0) 69.8 (67.0, 72.6) 65.7 (60.7, 70.7) Model 2 Physical function 64.5 (62.3, 66.8) 64.9 (63.4, 66.3) 62.8 (60.9, 64.7) 56.0 (52.1, 59.9) 57.0 (50.2, 63.8) Role-physical 58.4 (54.9, 62.0) 55.3 (53.0, 57.6) 52.8 (49.8, 55.8) 45.5 (39.3, 51.7) 47.3 (36.5, 58.2) Bodily pain 59.0 (57.0, 61.0) 58.4 (57.1, 59.7) 56.2 (54.5, 57.9) 50.9 (47.4, 54.3) 50.8 (44.7, 56.8) General health 61.7 (59.8, 63.5) 60.1 (58.9, 61.2) 58.4 (56.9, 60.0) 54.6 (51.5, 57.7) 54.6 (49.1, 60.1) Vitality 56.0 (54.1, 57.9) 55.6 (54.4, 56.8) 53.1 (51.5, 54.7) 49.7 (46.5, 52.9) 46.8 (41.1, 52.6) Social function 77.2 (74.9, 79.6) 77.8 (76.3, 79.3) 75.3 (73.3, 77.3) 70.1 (66.1, 74.1) 65.8 (58.7, 72.8) Role-emotional 73.8 (70.2, 77.3) 73.5 (71.2, 75.9) 71.5 (68.5, 74.5) 65.2 (59.0, 71.4) 69.4 (58.6, 80.2) Mental health 75.0 (73.4, 76.6) 74.6 (73.6, 75.7) 72.0 (70.7, 73.4) 69.8 (67.0, 72.6) 67.2 (62.3, 72.2) Model 3 Physical function 63.7 (61.5, 65.9) 64.5 (63.1, 66.0) 63.3 (61.4, 65.1) 58.6 (54.8, 62.4) 58.4 (51.7, 65.0) Role-physical 57.3 (53.8, 60.8) 54.8 (52.6, 57.1) 53.4 (50.5, 56.4) 49.0 (42.9, 55.1) 49.1 (38.5, 59.8) Bodily pain 58.2 (56.3, 60.2) 58.1 (56.8, 59.4) 56.6 (55.0, 58.3) 53.1 (49.7, 56.5) 52.0 (46.1, 57.9) General health 61.2 (59.4, 63.0) 59.8 (58.7, 61.0) 59.0 (57.2, 60.2) 56.2 (53.1, 59.3) 55.5 (50.1, 60.9) Vitality 55.4 (53.6, 57.3) 55.4 (54.2, 56.6) 53.4 (51.9, 55.0) 51.5 (48.3, 54.7) 47.6 (42.0, 53.2) Social function 76.5 (74.2, 78.8) 77.5 (76.0, 79.0) 75.7 (73.8, 77.7) 72.4 (68.4, 76.4) 67.0 (60.0, 73.9) Role-emotional 73.1 (70.0, 76.7) 73.3 (71.0, 75.6) 71.8 (68.8, 74.8) 67.1 (60.9, 73.3) 70.3 (59.6, 81.1) Mental health 74.7 (73.1, 76.3) 74.5 (73.5, 75.6) 72.2 (70.8, 73.6) 70.8 (68.0, 73.6) 67.7 (62.8, 72.6) * Values are the mean (95% confidence interval). SF-36 Medical Outcomes Study Short Form 36 Health Survey. Adjusted for age, sex, education, and body mass index (BMI). Adjusted for age, sex, education, BMI, back pain, hip pain, and knee pain. Adjusted for age, sex, education, BMI, back pain, hip pain, knee pain, and foot pain. was associated with a lower BMI in women but a higher BMI in men, which they attributed to overweight or obese women being more likely to wear less constrictive footwear. Since we did not collect data pertaining to footwear, we were unable to explore this relationship in the current study. The second objective of this study was to assess the Figure 4. Unadjusted mean Manchester Foot Pain and Disability Index (FPDI) pain and function subscale scores (Rasch scale) according to hallux valgus severity (worst foot). impact of hallux valgus severity on general and footspecific HRQOL. Three previous studies have examined the relationship between hallux valgus and the SF-36 (22 24); however, all 3 were conducted in hospital settings, and 2 used dichotomized definitions of hallux valgus (23,24). More recently, Abhishek et al reported that hallux valgus and concurrent big toe pain, but not hallux valgus alone, was associated with lower scores on the World Health Organization quality of life instrument (39). The only study to correlate hallux valgus severity with HRQOL scores used radiographic measurements and reported that the hallux valgus angle was negatively associated with the general health subscale score, and the intermetatarsal angle was negatively associated with the role-physical, roleemotional, and mental health subscale scores (22). However, no adjustment for potential confounders was performed, and the sample size was small (22 patients). Nevertheless, our findings confirm these preliminary observations in a much larger sample and indicate that the greater the severity of hallux valgus, the greater the impact on both general and foot-specific HRQOL. Importantly, these trends persisted after adjustment for several potential confounders, including pain in other lower extremity regions.

7 402 Menz et al Table 3. FPDI subscale scores (Rasch scale) across the 5 hallux valgus severity grades in participants who reported foot pain in the past 12 months (n 1,030)* Hallux valgus (worst foot) Pain Function Grade 1 (n 145) 1.08 ( 1.35, 0.81) 1.46 ( 1.82, 1.10) Grade 2 (n 437) 0.87 ( 1.02, 0.72) 1.29 ( 1.50, 1.09) Grade 3 (n 322) 0.59 ( 0.77, 0.40) 0.97 ( 1.21, 0.73) Grade 4 (n 93) 0.40 ( 0.74, 0.06) 0.49 ( 0.94, 0.03) Grade 5 (n 33) 0.75 (0.18, 1.32) 0.47 ( 0.31, 1.25) P * Values are the mean (95% confidence interval) adjusted for age, sex, education, and body mass index. FPDI Manchester Foot Pain and Disability Index. The impact of hallux valgus was not limited to the pain and physical function subscales of the SF-36, indicating that the condition also has a detrimental impact on broader aspects of HRQOL. Even after adjusting for the presence of foot pain, there remained a significant downward trend in general health, vitality, social function, and mental health scores across the 5 severity categories. In addition to the well-documented effect of hallux valgus on gait, balance, and falls (18 21), it is also possible that this is due to the difficulty many people with hallux valgus have in finding aesthetically acceptable footwear. Although medical-grade footwear with additional width and depth to accommodate the deformity is now widely available, it has been suggested that these shoes may have a detrimental effect on self-esteem and therefore contribute to social isolation, particularly in older women (40,41). Indeed, in patients considering surgical correction of hallux valgus, the ability to wear regular footwear is one of the most frequently cited expectations of the surgery (42), and satisfaction following surgery is strongly influenced by whether or not patients are able to wear their preferred footwear (24,43). Interestingly, there appeared to be a cutoff point for hallux valgus severity beyond which SF-36 scores began to decline, with little difference noted between the 2 least severe categories (Figure 3). The first image of the selfcompletion instrument we used represents a normal foot with a straight hallux, with subsequent images depicting increases in the hallux valgus angle of 15 degrees (28). Given that hallux valgus is typically defined as being present when the hallux valgus angle is greater than 20 degrees (16), previous applications of this tool have defined hallux valgus using the 3 most severe categories (15,28,39). Our results provide additional validation to this dichotomous classification, since significant declines in HRQOL were most evident in the 3 most severe categories. The role of pain in relation to the detrimental impact of hallux valgus is complex. Although people with hallux valgus are more likely to report foot pain (12,44) and big toe pain (15), they are also more likely to report pain in other body regions such as the knee (15); results confirmed in the current study for low back, hip, knee, and foot pain. It is therefore important to delineate the specific contributions of hallux valgus and pain in other regions of the lower extremity that may impact HRQOL. Our results indicate that adjustment for pain in the low back, hip, and knee did not substantially alter the effect of hallux valgus on SF-36 subscale scores, but adjusting for foot pain did. This indicates that a significant component of the detrimental impact of hallux valgus, particularly in relation to physical function, can be explained by concurrent foot pain. However, there remains a significant residual impact of hallux valgus on general health, vitality, social function, and mental health aspects of quality of life after foot pain is considered, which, as discussed previously, may be due to the effect of the condition on gait and balance, as well as difficulties associated with purchasing aesthetically pleasing footwear leading to a reduction in social participation. Foot-specific HRQOL was evaluated using the pain and function subscales of the FPDI (34,35). This tool explicitly asks participants whether each statement relates to pain in their feet, and it therefore provides a more specific indication of foot-related disability than the generic SF-36. Although the original FPDI also contains a subscale relating to concern about appearance, a recent analysis found that only the pain and function subscales fit the Rasch model (36), thereby allowing them to be analyzed as intervallevel scores. Because the FPDI was included in the regional pains survey questionnaire and was only completed by those who reported foot pain, the sample size for this component of the analysis was smaller (n 1,030). Nevertheless, the results revealed a similarly progressive decline in pain and function (as evidenced by larger subscale scores) as hallux valgus severity increased, and this persisted after adjusting for age, sex, education, and BMI. The observation that hallux valgus has a progressive detrimental impact on general and foot-specific HRQOL suggests that interventions aimed at correcting or slowing the progression of the deformity may have beneficial effects beyond that of localized pain relief. Indeed, 2 cohort studies have reported improvements in HRQOL scores following surgical correction of hallux valgus. Saro et al found that SF-36 bodily pain, vitality, and mental health subscale scores significantly improved in 94 women following surgery (24), while Dawson et al found that all SF-36 subscales, in addition to scores on the foot-specific Manchester-Oxford Foot Questionnaire and American Orthopedic Foot and Ankle Society scales, improved following surgery in a sample of 91 patients, with the greatest

8 Health-Related Quality of Life and Hallux Valgus 403 improvements noted for the foot-specific tools (45). However, whether the severity of hallux valgus influences the degree of improvement in HRQOL following intervention (either surgical or conservative) is yet to be adequately determined. The tool we have used in this study may therefore have some value as a predictor of clinical outcomes of hallux valgus treatment if combined with more detailed assessments in intervention studies. This study has a number of strengths. First, in contrast to previous clinical investigations, the sample was derived from a large population-based study and is therefore more likely to be generalizable to the broader community. Second, we used a validated self-report tool to assess hallux valgus across 5 levels of severity, whereas previous studies have used dichotomous definitions. Third, we assessed both generic and foot-specific HRQOL, and the footspecific tool we used (the FPDI) has been recently validated for use as an interval scale using Rasch analysis (36). However, we acknowledge that the study also has some inherent limitations. First, the hallux valgus self-assessment tool has not yet been validated against radiographic observations, and although we are confident that it provides a useful measure of the alignment of the hallux, other factors, such as the degree of joint degeneration, are likely to influence the impact of the condition on pain and function. Second, we did not collect information on other foot conditions (such as lesser toe deformity and plantar lesions) that frequently develop in conjunction with hallux valgus and may have an additional detrimental impact on HRQOL. Third, we did not request participants to document the precise location of their foot pain, so when adjusting for foot pain in the multivariate models, we cannot be certain that the foot most severely affected by hallux valgus was also the foot participants reported as being painful; it is possible that in some cases foot pain was unilateral but contralateral to the side affected the worst by hallux valgus. Fourth, we did not collect any information on footwear, which is likely to influence the impact of the condition on HRQOL. Finally, all prospective cohort studies are affected by responder bias; in our study, those who responded to the 6-year followup were generally healthier, younger, and more likely to be women than nonresponders. As such, the prevalence of hallux valgus reported here may be overestimated, and the strength of the relationships between hallux valgus and HRQOL may be underestimated. Despite these limitations, the findings reported in this study provide strong evidence from a large populationbased sample to indicate that there is a progressive reduction in both general and foot-specific HRQOL with increasing severity of hallux valgus deformity. Importantly, the impact of increasing hallux valgus severity on HRQOL is independent of age, sex, education, BMI, and pain in other regions, and extends beyond pain and physical function to affect general health, vitality, social function, and mental health. In conclusion, there is a progressive reduction in general and foot-specific HRQOL with increasing severity of hallux valgus deformity that is independent of age, sex, BMI, and pain in other regions. These findings indicate that hallux valgus is a significant and disabling musculoskeletal condition and suggest that interventions to correct or slow the progression of the deformity may have beneficial effects beyond that of localized pain relief. ACKNOWLEDGMENTS We are grateful to the administrative and health informatics staff at the Arthritis Research UK Primary Care Centre, Primary Care Sciences, Keele University, and the doctors, staff, and patients of the three participating practices. AUTHOR CONTRIBUTIONS All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. Dr. Menz had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study conception and design. Menz, Roddy, Thomas, Croft. Acquisition of data. Thomas. Analysis and interpretation of data. Menz, Roddy, Thomas. REFERENCES 1. Hardy RH, Clapham JC. Observations on hallux valgus: based on a controlled series. J Bone Joint Surg Br 1951;33B: Mann R, Coughlin M. Hallux valgus: etiology, anatomy, treatment and surgical considerations. Clin Orthop Relat Res 1981; 157: Spink MJ, Menz HB, Lord SR. Distribution and correlates of plantar hyperkeratotic lesions in older people. J Foot Ankle Res 2008;2:8. 4. Thomas S, Barrington R. Hallux valgus. Curr Orthop 2003;17: Johnston O. Further studies of the inheritance of hand and foot anomalies. Clin Orthop Relat Res 1959;8: Pique-Vidal C, Sole MT, Antich J. Hallux valgus inheritance: pedigree research in 350 patients with bunion deformity. J Foot Ankle Surg 2007;46: Kilmartin TE, Wallace WA. The aetiology of hallux valgus: a critical review of the literature. Foot 1993;3: Black JR, Hale WE. Prevalence of foot complaints in the elderly. J Am Podiatr Med Assoc 1987;77: Brodie BS, Rees CL, Robins DJ, Wilson AF. Wessex feet: a regional foot health survey. Volume I: the survey. Chiropodist 1988;43: Greenberg L, Davis H. Foot problems in the US: the 1990 National Health Interview Survey. J Am Podiatr Med Assoc 1993;83: Crawford VL, Ashford RL, McPeake B, Stout RW. Conservative podiatric medicine and disability in elderly people. J Am Podiatr Med Assoc 1995;85: Benvenuti F, Ferrucci L, Guralnik JM, Gangemi S, Baroni A. Foot pain and disability in older persons: an epidemiologic survey. J Am Geriatr Soc 1995;43: Dunn JE, Link CL, Felson DT, Crincoli MG, Keysor JJ, McKinlay JB. Prevalence of foot and ankle conditions in a multiethnic community sample of older adults. Am J Epidemiol 2004;159: Cho NH, Kim S, Kwon DJ, Kim HA. The prevalence of hallux valgus and its association with foot pain and function in a rural Korean community. J Bone Joint Surg Br 2009;91: Roddy E, Zhang W, Doherty M. Prevalence and associations of hallux valgus in a primary care population. Arthritis Rheum 2008;59: Coughlin MJ, Jones CP. Hallux valgus: demographics, etiology, and radiographic assessment. Foot Ankle Int 2007;28: Nguyen US, Hillstrom HJ, Li W, Dufour AB, Kiel DP, Procter- Gray E, et al. Factors associated with hallux valgus in a

9 404 Menz et al population-based study of older women and men: the MOBI- LIZE Boston Study. Osteoarthritis Cartilage 2010;18: Menz HB, Morris ME, Lord SR. Foot and ankle characteristics associated with impaired balance and functional ability in older people. J Gerontol A Biol Sci Med Sci 2005;60: Menz HB, Lord SR. Gait instability in older people with hallux valgus. Foot Ankle Int 2005;26: Menz HB, Morris ME, Lord SR. Foot and ankle risk factors for falls in older people: a prospective study. J Gerontol A Biol Sci Med Sci 2006;61: Mickle KJ, Munro BJ, Lord SR, Menz HB, Steele JR. ISB Clinical Biomechanics Award 2009: toe weakness and deformity increase the risk of falls in older people. Clin Biomech 2009;24: Lazarides SP, Hildreth A, Prassanna V, Talkhani I. Association amongst angular deformities in hallux valgus and impact of the deformity in health-related quality of life. Foot Ankle Surg 2005;11: Thordarson DB, Ebramzadeh E, Rudicel SA, Baxter A. Ageadjusted baseline data for women with hallux valgus undergoing corrective surgery. J Bone Joint Surg Am 2005;87: Saro C, Jensen I, Lindgren U, Fellander-Tsai L. Quality-of-life outcome after hallux valgus surgery. Qual Life Res 2007;16: Menz HB, Gilheany MF, Landorf KB. Foot and ankle surgery in Australia: a descriptive analysis of the Medicare Benefits Schedule database, J Foot Ankle Res 2008;1: Saro C, Bengtsson AS, Lindgren U, Adami J, Blomqvist P, Fellander-Tsai L. Surgical treatment of hallux valgus and forefoot deformities in Sweden: a population-based study. Foot Ankle Int 2008;29: Garrow AP, Papageorgiou A, Silman AJ, Thomas E, Jayson MI, Macfarlane GJ. The grading of hallux valgus: the Manchester Scale. J Am Podiatr Med Assoc 2001;91: Roddy E, Zhang W, Doherty M. Validation of a self-report instrument for assessment of hallux valgus. Osteoarthritis Cartilage 2007;15: Pique-Vidal C, Vila J. A geometric analysis of hallux valgus: correlation with clinical assessment of severity. J Foot Ankle Res 2009;2: Thomas E, Wilkie R, Peat G, Hill S, Dziedzic K, Croft P. The North Staffordshire Osteoarthritis Project (NorStOP): prospective, 3-year study of the epidemiology and management of clinical osteoarthritis in a general population of older adults. BMC Musculoskelet Disord 2004;5: Jordan K, Porcheret M, Kadam UT, Croft P. The use of general practice consultation databases in rheumatology research. Rheumatology (Oxford) 2006;45: Thomas E, Mottram S, Peat G, Wilkie R, Croft P. The effect of age on the onset of pain interference in a general population of older adults: prospective findings from the North Staffordshire Osteoarthritis Project (NorStOP). Pain 2007;129: Ware JE, Snow KK, Kosinski M, Gandek B. SF-36 health survey: manual and interpretation guide. Boston: The Health Institute, New England Medical Center; Garrow AP, Papageorgiou AC, Silman AJ, Thomas E, Jayson MI, Macfarlane GJ. Development and validation of a questionnaire to assess disabling foot pain. Pain 2000;85: Menz HB, Tiedemann A, Kwan MM, Plumb K, Lord SR. Foot pain in community-dwelling older people: an evaluation of the Manchester Foot Pain and Disability Index. Rheumatology (Oxford) 2006;45: Muller S, Roddy E. A Rasch analysis of the Manchester Foot Pain and Disability Index. J Foot Ankle Res 2009;2: Glantz S, Slinker B. Primer of applied regression and analysis of variance. New York: McGraw-Hill; Frey C, Zamora J. The effects of obesity on orthopaedic foot and ankle pathology. Foot Ankle Int 2007;28: Abhishek A, Roddy E, Zhang W, Doherty M. Are hallux valgus and big toe pain associated with impaired quality of life? A cross-sectional study. Osteoarthritis Cartilage 2010;18: Park C, Craxford AD. Surgical footwear in rheumatoid arthritis: a patient acceptability study. Prosthet Orthot Int 1981;5: Williams AE, Nester CJ, Ravey MI. Rheumatoid arthritis patients experiences of wearing therapeutic footwear: a qualitative investigation. BMC Musculoskelet Disord 2007;8: Tai CC, Ridgeway S, Ramachandran M, Ng VA, Devic N, Singh D. Patient expectations for hallux valgus surgery. J Orthop Surg (Hong Kong) 2008;16: Dawson J, Coffey J, Doll H, Lavis G, Sharp RJ, Cooke P, et al. Factors associated with satisfaction with bunion surgery in women: a prospective study. Foot 2007;17: Menz HB, Morris ME. Determinants of disabling foot pain in retirement village residents. J Am Podiatr Med Assoc 2005; 95: Dawson J, Doll H, Coffey J, Jenkinson C. Responsiveness and minimally important change for the Manchester-Oxford foot questionnaire (MOXFQ) compared with the AOFAS and SF-36 assessments following surgery for hallux valgus. Osteoarthritis Cartilage 2007;15: