Foot Musculoskeletal Disorders, Pain, and Foot-Related Functional Limitation in Older Persons

Fadi Badlissi, MD, MSc; Julie E. Dunn, PhD; Carol L. Link, PhD; Julie J. Keysor, PhD, PT; John B. McKinlay, PhD; David T. Felson, MD, MPH

Disclosures

J Am Geriatr Soc. 2005;53(6):1029-1033. 

In This Article

Methods

The Feet First Study was designed to determine the prevalence and correlates of foot/ankle conditions and foot pain in a community sample of adults aged 65 and older. Details of the study methodology have been described elsewhere.[7] In brief, stratified random sampling was employed to identify potential respondents from Medicare beneficiary and town census lists. Eligibility criteria included aged 65 and older; noninstitutional residence in Springfield, Massachusetts; not bed- or chair-bound; of Puerto Rican, African-American, or white/non-Hispanic race/ethnicity; and able to communicate with examiners in English or Spanish. Proxies were used for those unable to communicate effectively because of physical or cognitive health issues.

Nine hundred twenty-two subjects were enrolled; 784 of these (including 27 proxies) completed all parts of the study and constituted the sample for these analyses.

All subjects participated in a short telephone interview, including a modified version of the Foot Health Status Questionnaire (FHSQ), a questionnaire to evaluate foot-related function and pain.[8] Examiners made home visits to interview and conduct foot examinations. All examiners were centrally trained and underwent at least 2 days of hands-on training in foot examination and assessment techniques followed by at least 1 additional day of conducting foot/ankle assessments on older volunteers, all under direct supervision of clinical consultants who gave the final approval for certification. Partway through the collection period, examiners underwent field observation by the clinical consultants to ensure continued correct techniques.

The home interview included questions about comorbidities and self-reported health (parts of the Short Form 36-item (SF-36) questionnaire).[9] The foot/ankle examination included assessment of musculoskeletal conditions. Height and weight were measured. Subjects were asked to identify painful joints (including hip, knee, and lower back) on front and rear view of a human figure diagram. A lower extremity physical performance assessment including timed walk test was performed.[10]

The foot musculoskeletal disorders in this study included hallux valgus/bunion, bunionette, hammertoe, mallet toe, claw toe, overlapping toes, pes cavus (high arch), pes planus (flat foot), and plantar fasciitis. Presence of hammertoe, a plantar flexion of the proximal interphalangeal joint (the first joint distal to the web space); mallet toe, a plantar-flexion of the distal interphalangeal joint (the second joint distal to the web space); claw toe, a plantar flexion of both joints in the same toe; or overlapping toes were counted as lesser digit deformities. Pes planus (flat foot) was considered present if the examiner was unable to insert his/her fingers under the arch of the foot with the respondent in a standing position, whereas pes cavus (high arch) was considered present if the examiner could insert his/her fingers all the way underneath the arch. Plantar fasciitis was defined as tenderness over the insertion site of the plantar fascia near the heel.

Foot pain was determined by responses to two questions. "During the last week, how often have you had aches or pains in your feet?" (never, occasionally, fairly often, very often, or always). "During the past four weeks, have you had foot pain or discomfort on most days?" (yes or no). A response of fairly often/very often/always to the first question or a yes response to the second question was counted as a positive response for foot pain.

The first functional outcome was self-reported foot health functional status (FHFS), based on four questions addressing foot-related limitations and difficulties in work, activities, and walking, and climbing stairs within the previous week. Responses to all four questions were given on a 5-point scale: not at all, slightly, moderately, quite a bit, or extreme. The subjects' answers to the four questions were added/converted to the FHFS scale (range 0-100, 0 worst-100 no problems).[8]

The FHFS scale constituted the foot function domain in the FHSQ, which has been described elsewhere.[8] The FHSQ was initially developed to evaluate the outcomes of surgical treatments of common foot conditions. The FHSQ and its subscale (FHFS scale; the above four questions) demonstrated high test-retest reliability and content, construct, and criterion validity.[8]

The second functional outcome was a timed walk test, part of an established lower extremity physical performance battery.[10] Participants were timed as they walked a measured course (3 or 4 m depending upon available space in their homes). The walk was repeated, and the time of the faster walk was converted to a 0- to 4-point scale, with 4 being the fastest. Subjects were given a score of 0 if they could not attempt or complete the walk. For the 3-m walk, 1 point was assigned for a time longer than 6.52 seconds, 2 for 4.66 to 6.52 seconds, 3 for 3.62 to 4.65 seconds, and 4 for a time less than 3.62 seconds. For the 4-m walk, 1 point was assigned for a time longer than 8.70 seconds, 2 for 6.21 to 8.70 seconds, 3 for 4.82 to 6.20 seconds, and 4 for a time less than 4.82 seconds. These categories of performance were created to permit analyses that included subjects unable to perform the walk test. This scoring method was modified from previous work.[10]

Analyses were adjusted for demographic characteristics: age (continuous), sex, and race/ethnicity. Other covariates included body mass index (BMI, weight (kg)/height (m2)) as a continuous variable; hip or foot fracture; diabetes mellitus; and hip, knee, and low-back pain. For the functional outcomes, the FHFS scale and the walk test, the use of assistive devices was adjusted for; 27 subjects used such devices.

Lower extremity conditions including ankle edema and ingrown toenail were adjusted for, because they have been shown to be associated with foot pain, and for claudication and sensory loss, because they were expected to be related to foot pain.[3,4] Ankle edema and sensory loss did not affect the coefficients of the foot disorders of interest, so they were deleted from the models.

Finally, the role-emotional domain of the SF-36 questionnaire was converted to a 0 to 100 scale (100=best) as described previously and used as a continuous variable in the analyses.[9,11] This scale was adjusted for as a proxy indicator of psychological symptoms, which are known to be associated with pain and disability.

Logistic regression was used to obtain adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for the relationship between foot musculoskeletal disorders and pain, while adjusting for potential confounders. Stepwise multiple linear regression was used to evaluate the portion of the variance in the walk test and the FHFS scale scores explained by the foot disorders. The dependent variables, the FHFS scale and the walk test scores were employed as continuous variables. In a stepwise manner, we added plantar fasciitis, arch deformities (pes cavus and planus), other foot deformities (hallux valgus, bunionette, and lesser digits deformities), and potential confounders as covariates. Finally, foot pain was added. The multiple coefficient of determination was obtained for each step. To evaluate the effect of foot pain on functional limitation, the effects of foot disorders of interest were compared, with and without adjustment for foot pain

All analyses were weighted to reflect the demographics of Springfield, Massachusetts, in 2000. The sampling weights were proportional to the inverse of the probability of selection, given the individual's initial stratum.

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