POSTERIOR TIBIAL TENDON DYSFUNCTION IN RHEUMATOID-ARTHRITIS

Although hindfoot pathology in rheumatoid arthritis is a significant c ause of disability for patients, the etiology of the planovalgus defor mity is controversial. The present study surveys 99 patients with clin ically proven rheumatoid arthritis for the presence and severity of hi ndfoot pathology, Specific attention was directed at the function of t he posterior tibial tendon, as disruption of this structure has been i mplicated by some investigators as a cause of hindfoot deformity in rh eumatoid arthritis, Assessment of posterior tibial function was by man ual testing using two different grading scales, as well as by examinat ion for several signs associated with posterior tibial tendon dysfunct ion. Between 13% and 64% of the study population could be considered t o have posterior tibial tendon dysfunction, depending upon the specifi c diagnostic criteria used, Using the presence of all three of the mos t stringent criteria for diagnosis, 11% of patients were believed to h ave posterior tibial tendon dysfunction. These criteria were loss of t he longitudinal arch, inability to perform a heel-rise, and lack of a palpable posterior tibial tendon. This study demonstrates that planova lgus deformity in rheumatoid arthritis can be due to clinically eviden t dysfunction of the posterior tibial muscle-tendon unit, There is a c omplex interplay between hindfoot joint disruption due to the inflamma tory process and deformity due to tendinous dysfunction, If there is p rimary subtalar joint instability secondary to the inflammatory proces s, the posterior tibial tendon is rendered dysfunctional due to derang ed hindfoot mechanics, as with primary posterior tibial tendon rupture . Since treatment of either condition (i.e., primary hindfoot instabil ity or primary posterior tibial tendon rupture) is similar, the distin ction is not important clinically. What is important is that attention to the specific cause of planovalgus would be expected to improve the overall treatment of rheumatoid feet.