Amikacin-Impregnated PMMA for Management of Surgical Site Infection Prior to TPLO Revision in a Patient with Severe Genu Varum

A 6-year-old female spayed Pitbull presented for evaluation of a left pelvic limb lameness and genu varum with delayed union 2 months following TPLO and revision of a postoperative tibial tuberosity fracture. Draining tracts were noted after 6 weeks of empirical cephalexin therapy. The methicillin-resistant Staphylococcus pseudintermedius that was cultured was treated with TMS for 8 weeks, after which explant was performed. Following removal of the loose implants, amikacin-impregnated PMMA beads were implanted. Despite improved comfort, her lameness, stifle instability and genu varum persisted. TPLO revision was performed 11.5 months after explant, 1.5 years post TPLO. Arthrotomy revealed a ruptured CCL, torn medial meniscus and grade IV/IV medial compartment cartilage lesions. A routine TPLO was performed as well as varus correction of an 80-degree mMPTA measured on tangential caudocranial radiographs. She had complete radiographic healing after 5 months. Though widely recommended, the use of PMMA as a vehicle for local antibiotic therapy seems based on human clinical trials as few veterinary studies exist. Despite a lack of reports describing its use for TPLO infection, PMMA was chosen due to its prolonged elution profile compared with other agents. Correction of proximal tibial varus deformities with decreased mMPTA becomes important as mechanical axis deviation leads to overloading of the medial compartment. The successful outcome in this case supports the use of amikacin-impregnated PMMA for TPLO implant infection and highlights benefits of tangential preoperative radiographic assessment and improved outcome following varus deformity correction. No proprietary interest or funding was provided for this project.

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