Risk factors for periprosthetic ankle joint infection: a case-control study

Periprosthetic ankle joint infection is a feared complication of total ankle arthroplasty because the implant fails in the majority of cases. However, risk factors for developing these infections are unknown.

We aimed to determine risk factors for infection in a matched case-control study that included twenty-six patients with periprosthetic ankle joint infection and two control groups, each consisting of fifty-two patients.

The prevalence of periprosthetic ankle joint infection within our cohort was 4.7%. Four infections (15%) had a hematogenous origin and twenty-two (85%), an exogenous origin. Staphylococcus aureus was the most common pathogen, followed by coagulase-negative staphylococci. Preoperative predisposing factors associated with infection included prior surgery at the site of infection (odds ratio [OR] = 4.56, 95% confidence interval [CI] = 0.98 to 21.35, and OR = 4.78, 95% CI = 1.53 to 14.91, in comparison with the two control groups) and a low American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score (35.8 versus 49.8 and 47.6 in the two control groups, p ≤ 0.02). The mean duration of the index surgery was significantly longer in the case group than in both control groups (119 versus eighty-four and ninety-three minutes, p ≤ 0.02). After surgery, persistent wound dehiscence (OR = 15.38, 95% CI = 2.91 to 81.34, p = 0.01, in comparison with both control groups) and secondary wound drainage (OR = 7.00, 95% CI = 1.45 to 33.70, and OR = 5.31, 95% CI = 1.01 to 26.78, in comparison with the two control groups, p ≤ 0.04) were associated with the development of a periprosthetic ankle joint infection.

Patients at risk for periprosthetic ankle joint infection following total ankle arthroplasty include those with a history of surgery on the ankle, a low preoperative AOFAS hindfoot score, and a long operative time. Postoperatively, patients with a prolonged wound dehiscence or a secondary wound-healing problem are also at risk for infection.