To analyze the associations of age and gender with post-operative outcomes after pilon fracture and the effect of interaction between age and gender on the outcomes.

A retrospective cohort study was performed of the 101 successive patients with pilon fracture who had been treated by open reduction and internal fixation from March 2009 to November 2013 and completely followed up. The distributions of potential prognostic factors (diabetes, injury mechanism, open fracture, Rüedi-Allgöwer classification and AO classification) were analyzed in different age and gender groups. The outcomes were evaluated in terms of reduction quality by the Burwell-Charnley criteria, time for return to work, traumatic osteoarthritis by Kellgren-Lawrence grading scale and the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score. The odds ratio and regression coefficients were estimated by Logistic regression and linear regression model; P values for interaction between age and gender were estimated by likelihood ratio tests.

Of all the 101 pilon patients, 84 were male and 12 were the aged. The distributions of gender (P=0.028) and mechanism (P=0.032) were significantly different between the aged and the younger patients, showing there were more females in the aged patients and low-energy injury wasmore likely to cause a pilon fracture in the aged patients. As multivariate analyses suggested, with the above influencing factors controlled, a median follow-up of 41.2 months revealed age was an independent favorable prognostic factor for reduction quality (OR=3.919, P=0.041). The association between gender and time for return to work was significantly different between the aged and the younger patients, as indicated by interaction analyses (P=0.030).

There may be more females in the aged patients with pilon fracture than in the younger ones. It is likely that the aged patients sustain a pilon fracture because of low-energy injury and achieve a fracture reduction of poorer quality. Although the quality of reduction may be poorer for the aged, there may be no significant difference between the aged and the younger patients in the mid-long-term AOFAS score. It is advisable for surgeons to provide personalized treatment to better help the patients.

Ankle injuries; Prognosis; Aged; Interaction analysis