Foot & Ankle

Periprosthetic bone infection

Periprosthetic infection of total ankle joint replacements is not as well studied or characterised as that of the hip and knee. Whilst infection is as common a problem as in other replacement joints, the relative rarity of ankle arthroplasty means that whilst well described, infections around the ankle joint are not well studied. Researchers in Bern (Switzerland) set out to evaluate the utility of their standardised hip and knee infection protocols for treating infections of the ankle.³ They describe a case series of 34 infected joints drawn from a series of 511 ankle replacements and followed-up to a minimum of two years after operation. There was a mixture of acute (56%) and chronic (44%) infections, with the overwhelming majority of infections caused by Staphylococcus spp (71%). Surgical strategies included retention of components (62%), revision of both components (30%) and arthrodesis (8%). The treating team were successful in eradication of the infection in 68% of patients with this strategy, although superior cure rates were seen with revision of both components (90%). There was significant variation in the treatment strategies between patients with infected ankle replacements, and the authors noted that 80% of patients were not treated in what would be considered a standard manner for total knee or hip infection. These authors sensibly infer that treatment of ankle replacement infections should be along similar lines to those developed for other periprosthetic infections, and in particular the quality of the soft-tissues over the infected joint should be conserved. More aggressive treatment with revision of both components results in a more successful treatment strategy.

Infection in ankle fixation

Due to the poor soft-tissue envelope and subcutaneous nature of the bone, there is potentially a significant incidence of infection after ankle fixation. The majority of the published literature however, focusses on high risk groups such as diabetics, the elderly and open fractures. Little however is known about the functional outcomes of patients following the development of infection – surgeons in Leicester (UK) set out to establish the long-term functional consequences of previous post-operative infection.⁴ The research team undertook an age- and gender- matched cohort study to identify patient and surgical risk factors for infection, in addition to assessing the long term functional sequelae of both superficial and deep infection in a series of over 700 patients. The incidence of infection was 4% (n = 29/717) and deep infection occurred in 8 patients (1.1%). Olerud and Molander ankle performance scores were severely impeded in the infection group (60 vs 90) and multivariant regression analysis undertaken identified risk factors of diabetes (odds ratio (OR) 15), nursing home residence (OR 12) and Weber C fractures (OR 4) to be significant risk factors for infection. This paper demonstrates surprisingly poor long term results for patients who have suffered from superficial and deep infections. It seems likely to us here at 360 that this moderate impairment is partly due to the infection and also partly due to the fact that no adjustment of outcome scores has been undertaken to consider their identified risk factors (many of which would be expected to affect baseline function).