Prevalence and associated factors for primary osteoarthritis of the thumb carpometacarpal joint in the general elderly population: A cohort survey randomly sampled from a basic resident registry of a small rural town in Japan.

Background: Osteoarthritis of the thumb carpometacarpal joint often presents pain and affects activity of daily life. There is no consensus regarding prevalence of primary radiographic osteoarthritis and symptomatic osteoarthritis of the thumb carpometacarpal joint, and their associated factors are not well investigated. The purpose of this study is to evaluate the prevalence and associated factors of primary radiographic and symptomatic osteoarthritis of the thumb carpometacarpal joint in a resident cohort.

Methods: A total of 1297 residents aged 50 to 89 were randomly sampled from a small rural town in Japan, and their demographic data and questionnaire regarding lifestyle and job were obtained. All participants underwent posteroanterior radiographs of the bilateral hands. Participants with thumb carpometacarpal joint radiographic osteoarthritis were diagnosed if one of their thumb carpometacarpal joints was Kellgren-Lawrence grade 2, 3, or 4. Symptomatic osteoarthritis was diagnosed by tenderness or positive motion pain at the thumb base. Associated factors for the thumb carpometacarpal joint radiographic osteoarthritis were statistically analyzed.

Results: A total of 646 thumbs with 323 participants (153 male and 170 female) were investigated. The mean age was 69.1 (range 50-89) years, The prevalence of thumb carpometacarpal joint radiographic osteoarthritis was 17.3 % (13.7 % males and 20.6 % females) and that of thumb carpometacarpal joint symptomatic osteoarthritis was 3.1 %. Associated factors for thumb carpometacarpal joint radiographic osteoarthritis were presence of finger joint radiographic osteoarthritis in the ipsilateral hand, increasing age, and female in order of degree of relevance. Dominant hand, body mass index, smoking history, heavy manual or agriculture work, use of vibrating tools, racket or bat sports, or scaphotapeziotrapezoidal joint radiographic osteoarthritis were not associated factors for thumb carpometacarpal joint radiographic osteoarthritis.

Conclusions: The prevalence of thumb carpometacarpal joint primary radiographic osteoarthritis in general Japanese elderly aged 50-89 years was 17.3 %, most of carpometacarpal joint radiographic osteoarthritis was asymptomatic.