After diagnosis of infection and informed consent, patients will be taken to the operating room. After anesthetization, patients will be randomized to either an articulating spacer or static spacer. Randomization will be performed by prepared opaque envelopes administered by a nonparticipant in the study. After a complete debridement of devitalized tissue, explantation of infected components and any associated cement, either an articulating or static spacer will be placed. All spacers will be formed using 3.0 g of Vancomycin and 1.0 g of Tobramycin for each 40 g packet of cement. Articulating spacers will be formed of antibiotic-impregnated cement using the Stage One system (Biomet, Warsaw, IN) sized to fit the endosteal and acetabular bone defect. Static spacers will be hand-made with a rod of antibiotic-impregnated cement and cement beads of sufficient quantity to fill the acetabulum.
Post-operatively, all patients will be made touch-down weight bearing protected with a walker or crutches. At the time of reimplantation, the joint will be aspirated and multiple cultures obtained along with intraoperative histopathological analysis to evaluate for persistent infection.
Data collected preoperatively will include age, gender, laterality, etiology of hip degeneration, comorbidities, Harris Hip score, infecting organisms and Paprosky femoral and acetabular bone loss classification. The Harris Hip score has been used extensively in the study of revision hip arthroplasty and has been found to be reliable and valid and will be determined preoperatively and at all follow-up visits.
Data collected at the time of implant removal and reimplantation will include operative time, blood loss, surgical approach, and need for an extended trochanteric osteotomy. Radiographs performed immediately following and just prior to reimplantation will be reviewed to determine if the spacer utilized has caused bone loss; bone loss to the cut bony surfaces will be confirmed intraoperatively. At each follow-up visits radiographic appearance, the Harris Hip Score, dislocation events, recurrence of infection, and the need for revision or reoperation of any kind on the hip will be determined.
All portions of this study will be part of conventional care except for randomization and collection of the Harris Hip Score. Which type of spacer is used currently depends upon the judgment of the attending surgeons and both are used routinely.
The primary outcome variable will be Harris Hip Score. A power analysis was conducted with the assistance of Dr. Mario Moric at Rush. Using the standard deviation of Harris Hip Scores from Hsieh and colleagues (2004) and Fehring and colleagues (1999), the largest previous studies reporting such data, Dr. Moric estimated 56 patients, 28 patients per group, would be needed to detect a clinically relevant difference of ten points. To account for attrition, our target total sample size will be 80 patients.
