Does tobramycin impregnation of allograft bone affect implant fixation? - an experimental study in 12 dogs.

Clinical trials have used antibiotic impregnated impacted bone allograft in revisions of infected arthroplasties. By this method high local antibiotic concentration and good control of infection was achieved. Toxicity studies, however, suggest that high local antibiotic concentration can impair osteoblast replication. We therefore asked whether impregnating morselized allograft bone with different quantities of tobramycin before impaction would impair implant fixation. We implanted three cylindrical (10 mm × 6 mm) porous-coated titanium implants into the distal femurs of 12 dogs. The implants were surrounded by a circumferential gap of 2.5 mm into which a standardized volume of morselized allograft bone, with or without tobramycin, was impacted. In each animal, the bone graft was impregnated with either 0 mg (control), 50 mg (low dose), or 200 mg (high dose) of tobramycin per 1 mL of bone graft. At the end of the 4 weeks experimental period, the implants with surrounding bone were evaluated by histomorphometric analysis and mechanical push-out test. We found no difference between the treatment groups regarding new bone formation, bone graft resorption, or implant fixation. There was, however, a tendency toward a decrease in implant fixation with higher tobramycin dose. The present study is unable to provide evidence on whether the use of topical tobramycin with allograft is safe or whether it indeed can impair implant fixation. The tendency toward an impaired implant fixation warrants further preclinical studies. Its current clinical use should be weighed against its possible positive effects on preventing infection in complicated revisions.

Acetabular Revision Using Cementless Acetabular Cup

PURPOSE: To evaluate implant survivorship and clinical outcomes after acetabular revision using cementless acetabular cups. MATERIALS AND METHODS: We evaluated 27 cementless acetabular revision cases performed between January 1998 and October 2005. All patients were followed up for more than 2 years, and the mean follow-up period was 54.1 months (range: 24~120 months). In all cases, morselized allografting was performed. Five cases needed structural allografting to achieve stability of the acetabular cup. The clinical results were analyzed using the Harris hip score, and radiological analysis was performed for evaluation of radiolucent lines, osteolysis, loosening, and changes in the hip center. RESULTS: At the time of latest follow-up, no cups showed failure requiring re-revision. The average Harris hip score improved from 67.1 points preoperatively to 91.4 points postoperatively. Radiologically, 7 cases (25.9%) showed radiolucent lines around the acetabular cup, but there was no loosening or osteolysis. CONCLUSION: Cementless acetabular revision showed satisfactory radiological and clinical results on short-term follow-up analysis. Even in cases with considerable amounts of acetabular bone loss, stable fixation could be obtained with structural bone grafting.

Acetabular Reconstruction with Impacted Morselized Allograft, Wire Mesh and Cemented Acetabular Cup in Severe Acetabular Bone Defect

PURPOSE: This study evaluated the clinical and radiographic results of an acetabular reconstruction with an impacted morselized allograft and wire mesh in revision total hip arthroplasty. MATERIALS AND METHODS: This study examined 21 cases of acetabular revisions involving 20 patients with a severe acetabular bone defect managed with an impacted morselized allograft, wire mesh and cemented acetabular cup between February 2000 and June 2003. The mean follow up period was 31.7 months. Clinically, the Harris hip score was evaluated. The radiographic parameters included bony incorporation between the host bone and allograft, the change in cup inclination, acetabular cup migration, radiolucency around the cup and loosening. RESULTS: The mean Harris hip score was improved from a preoperative 54.1 to 91.9 at the last follow up. Radiological incorporation between the host bone and allograft was achieved after an average 11.4 months after surgery. The mean change in cup inclination was 1.9 degrees, and the mean medial and superior migration was 3.93 mm and 4.41 mm respectively. The majority of these radiological changes occurred within 6 months after surgery. One case of Brooker grade I heterotopic ossification and one case of acetabular cup loosening was observed but there was no re-revision or complications, such as infection and dislocation. CONCLUSION: In a severe acetabular bone stock deficiency that cannot be reconstructed with a cementless acetabular cup, an acetabular reconstruction with an impacted morselized allograft, wire mesh and cemented acetabular cup showed good results in this short term follow up study.

Revision Total Hip Arthroplasty using Morselized Femoral Head Allograft and Cementless Cup in Acetabular Bone Deficiency / 대한정형외과학회잡지

PURPOSE: This study was aimed to evaluate the clinical and radiologic results of revision total hip arthroplasty using a cementless cup and a morselized femoral head allograft in acetabular bone deficiency. MATERIALS AND METHODS: From January 1992 to December 1999, the authors performed 37 revision total hip arthroplasties using morselized femoral head allografts and cementless cup. This study evaluated the clinical and radiologic results, at a mean follow-up of 50 months. We evaluated the Harris hip score clinically, and the displacement of acetabular cup by Yoder's criteria. Location and progression of radiolucent area within acetabular zone, which was defined by DeLee and Charnley was observed and recorded. RESULTS: Mean Harris hip score was improved from 50.6 preoperative to 89.2 at final follow-up. A radiolucent zone between host bone and graft bone was observed in 5 cases, and between graft bone and cup in 7 cases, but all of these were less than 2 mm. The change of cup angle more than 4 degrees were observed in 3 cases in Gross type 4, 4 mm superior migration of acetabular cup was observed in 1 case in Gross type 3 and 5 mm horizontal migration was observed in 1 case in Gross type 4. CONCLUSION: Although the early results in revision total hip arthroplasty have been encouraging to date except for Gross type 4, a more long term follow-up study with a larger size cases are needed.