HOJ-2003 v7

Wolfgang Fitz, MD Brigham and Women’s Hospital Department of Orthopaedic Surgery 75 Francis St. Boston, MA 02115 Office: 617-732-5401 Email: [email protected] INTRODUCTION Infection is a devastating complication of total knee arthroplasty, affecting up to 2% of primary knee arthroplasties and up to 5.6% of revision knee arthroplasties. [1] Two-staged reconstruction --with thorough debridement of all nonviable tissue including pseudomembrane, removal of components and cement, and long-term parenteral antibiotics followed by reimplantation-has become the standard of care in treating these infections and has met with a high rate of success.[2-4] With dual goals of eradicating infection and optimizing function, various technical modifications of the staged reconstruction process have evolved. One such technical modification, now in use for over a decade, is the utilization of a temporary intra-articular spacer fashioned out of antibiotic-impregnated bone cement. Such a spacer helps to maintain an appropriate soft tissue envelope and permits local delivery of high doses of antibiotic without systemic toxicity.[5] Traditionally, spacers have been static, consisting of a single block of cement positioned between the distal femur and proximal tibia (Figure 1). Recently, dynamic spacers have been introduced, comprising of separate femoral and tibial components that permit limited articulation with or without the combination of resterilized femoral components and thin polyethylene tibial components. A variety of techniques for making these articulating spacers appears in the literature.[6-11] However, it is unclear whether static cement spacers are superior to articulating spacers.[12] We present a simple, inexpensive method for the intra-operative manufacture of a custom-fit, all-cement articulating spacer, and review the relevant literature. SURGICAL TECHNIQUE The initial surgical treatment of the total knee arthroplasty with suspected or confirmed sepsis is approached in standard fashion. Adequate exposure for thorough debridement and removal of components is attained. Multiple tissue samples for deep cultures are taken prior to administration of intraoperative antibiotics. The knee is then irrigated copiously utilizing pulsatile lavage. A set of templates is then used to help fashion the separate femoral and tibial components of the articulating spacer. Templates for the distal femur and proximal tibia are prepared in advance from 0.7 mm thick aluminum sheeting (Figure 2) and autoclaved for sterility. The same set of templates may be used for multiple cases. The femoral template is elongated, which permits one to fashion an anterior flange to fill the suprapatellar pouch. The appropriate curvature for the distal femoral spacer is created by bending the template around a trial component that matches the general size and curvature of the patient’s extracted femoral component. Alternatively, the extracted femoral component—once autoclaved—may be used as a model for molding. Flexion and extension gaps are checked to gain an idea of the thickness of the cement needed. Strict balancing of flexion and extension gaps is not necessary, but tightness in flexion should be avoided. Antibiotic-impregnated polymethylmethacrylate (PMMA) Figure 1. AP and lateral of traditional static spacer block.