Study of the relation between the posterior malleolus fracture and the development of osteoarthritis

At least 10% of ankle fractures involve the posterior malleolus of the tibia, which has been related to poorer long-term prognosis. Our aim was to analyse the clinical and functional outcomes of ankle fractures involving the posterior edge, treated surgically without direct reduction of the third malleolus.

We performed a retrospective study of 45 patients aged under 60, who we classified into three groups in terms of the percentage of joint involvement of the posterior fragment (<10%, 10%-25% and >25%) assessing the functional outcomes using the visual analogue pain scale (VAS), the AOFAS scale (American Orthopedic Foot and Ankle Society) of the ankle and hindfoot and the global health questionnaire SF-36; we also analysed the degree of osteoarthritis with weight-bearing radiography, at least one year following the injury.

The mean VAS pain score of the sample was 1.1 (0-5) at rest and 3 (0-8) on exercise; 88.4±10.1 on the AOFAS scale, and 68.5±19.3 points on the SF-36. Up to 18% of the patients developed radiographically significant osteoarthritis in the short and medium term (between 12 and 73months, with a mean of 33months). Of the patients, 55.6% had involvement of between 19% and 25% of the joint surface. We found that a larger posterior fragment size related to a greater degree of early-onset osteoarthritis (P<.03) and poorer AOFAS scores (P<.01).

Ankle fractures involving the posterior malleolus seem to contribute to the development of early-onset osteoarthritis with functional limitation in young adults.