Fighting Megaprosthetic Infections: What are the Chances of Winning?

Megaprosthetic infections continue to be a leading mode of failure after limb salvage surgery. Though challenging, amputations can be avoided with proper management in majority of the cases. This study aims to describe the spectrum of mega-endoprosthetic infections at our institute and assess the treatment efficacy in these patients.

All patients treated for endoprosthetic infection at our institute between 2010 and 2018 were retrospectively analyzed for overall survival of reconstruction method, site and type of megaprosthesis, adjuvant therapy, microbial isolates, surgical and medical management and outcomes.

Thirty-five patients (22 males: 13 females) were analyzed following treatment for endoprosthetic infection. Majority were around the knee joint [most commonly with proximal tibia (n = 14) followed by distal femur (n = 12) megaprosthesis]. Ten patients had undergone primary surgical procedure at our institute, while 25 patients presented with infection after megaprosthesis implantation. In the 28 culture-positive infections, the most common micro-organism was Staphylococcus spp. (18 patients: methicillin-sensitive Staphylococcus aureus = 9, coagulase-negative Staphylococcus = 5, methicillin-resistant Staphylococcus aureus = 1, Staphylococcus epidermidis = 3) and poly-microbial infection was present in three patients. Nine patients underwent successful debridement and wound wash with insertion of antibiotic impregnated cement beads in 5/9 cases. Twenty-one patients required a two-stage revision. Of these 30 patients, all but one has completely resolved infections. One patient with resurfaced late infection after re-implantation is on chronic suppressive antimicrobial therapy and close follow-up. Amputation because of uncontrolled infection was performed in three patients (one death post-operatively due to systemic complications of septicemia), while two patients opted for amputation as opposed to stage revisions. Median antimicrobial therapy duration was 6 weeks (1-12 weeks). Reconstructive surgery for soft tissue cover was required in seven patients.

In patients with early or acute presentation without frank granulation or pus around the implant, debridement and insertion of antibiotic cement beads was adequate. Two-stage revisions with complete removal of the megaprosthesis showed best results in infections that could be controlled with antimicrobial therapy. More than one exchange of cement spacer was required for uncontrolled infections. Multidisciplinary approach in consultation with the infectious disease team is essential to determine choice of antibiotic cement for beads/spacer as well as appropriate adjuvant antimicrobial therapy to solve the challenging problem of endoprosthetic infections following bone tumor surgery. Adequate and healthy soft tissue cover of the implant should be achieved wherever indicated.