Combination of Calcium Hydroxyapatite Antibiotic Carrier with Cement Spacers in Peri-Prosthetic Knee Infections Vasileios I. Sakellariou, Olga Savvidou, Christos Markopoulos, Androniki Drakou, Andreas F. Mavrogenis, and Panayiotis J. Papagelopoulos Abstract Background: Forty-six patients (38 females and 8 males) with infected knee arthroplasties were included in this study. In 31 patients (group A) an antibiotic-impregnated articulating spacer was used, whereas in 15 patients (group B) a combination of spacer and antibiotic carrier was used. Methods: All patients were reviewed weekly with laboratory examinations (white blood cell count [WBC], erythrocyte sedimentation rate [ESR], C-reactive protein [CRP]) prior to re-implantation. At a mean follow-up of 36 mo (range, 8–60 mo) no patient was lost to follow-up or had died. Results: White blood cell count and ESR showed no differences at any time interval. C-reactive protein values had a statistically significant difference between the two groups after the second week (third week p = 0.042) and group B had significantly lower CRP values at every checkpoint thereafter. The re-infection rate was 16.12% in group A and 6.6% in group B (p = 0.192). D eep infection remains one of the most devastating and challenging complications of total knee replacement (TKR). Although the incidence is reported to be low gener- ally, the complexity and duration of treatment often impart substantial physical, emotional, and financial costs to both the patient and treating physicians [1–7]. The treatment of peri-prosthetic knee infection is one of the most challenging problems in adult reconstructive surgery. Two-stage revision procedures are the gold standard in management of peri- prosthetic knee infections. Cement spacers (hand- or ready- made) impregnated with antibiotics have been used to pre- serve the space created during the resection procedure and to release antibiotics within the created dead space. However, the problems related to cement as an antibiotic carrier in- cluding random porosity, bone thermal necrosis, and un- specified antibiotic delivery rate are well recognized [8–11]. Recently, new composite biomaterials have been created in an effort to facilitate local antibiotic delivery at the site of infection in new and creative ways and to achieve high local antibiotic concentrations without associated systemic toxic- ity [12]. These novel local antibiotic delivery systems were designed to provide a framework of osteoinductive and os- teoconductive materials along with antibiotic delivery [13]. PerOssal Ò (Coripharm, Dieburg, Germany) is a new osteo- conductive biodegradable composite carrier material consist- ing of a combination of calcium sulfate and nanocrystalline hydroxyapatite (Ostim Ò , Osartis, Obernburg, Germany). Because of its good biocompatibility and sufficient and in- dividualized antibiotic release it represents a new treatment option in chronic bone infection [11,14]. The rationale of this study is that a calcium hydroxyapatite local antibiotic de- livery system (PerOssal) may overcome the known disad- vantages of cement spacers and lead to better outcome in terms of clinical parameters and re-infection rate when combined with pre-formed articulating spacers. Our purpose was to identify potential clinical and laboratory differences between cases that underwent conventional two-stage revi- sion arthroplasty and cases treated with PerOssal as an ad- ditional antibiotic carrier. Patients and Methods Study design and population We conducted a single-center cohort study including 46 consecutive patients with deep chronic peri-prosthetic in- fection after primary total knee replacement (TKR). All pa- tients were diagnosed and treated at our institution during the period 2006–2009. We included consecutive cases of late 1st Department of Orthopaedics, Athens University Medical School, General University Hospital Attikon, Haidari, Greece. SURGICAL INFECTIONS Volume 16, Number X, 2015 ª Mary Ann Liebert, Inc. DOI: 10.1089/sur.2014.083 1