Rinsing of allograft bone does not improve implant fixation

Abstract

Background and purpose Impacted morselized allograft bone is a well-established method for reconstructing bone defects at revision surgery. However, the incorporation of bone graft is not always complete, and a substantial volume of fibrous tissue has been found around grafted implants. We hypothesized that rinsing the bone graft may improve graft incorporation by removing the majority of immunogenic factors present in blood, marrow, and fat.

Methods We implanted a cylindrical (10- × 6-mm) porous-coated Ti implant into each proximal tibia of 12 dogs. The implants were surrounded by a 2.5-mm gap into which morselized fresh frozen allograft bone was impacted. The bone graft was either (1) untreated or (2) rinsed in 37°C saline for 3 × 1 min. After 4 weeks, the animals were killed and implant fixation was evaluated by mechanical push-out and histomorphometry.

Results The groups (rinsed vs. control) were similar regarding mechanical implant fixation (mean (SD)): shear strength (MPa) 2.7 (1.0) vs. 2.9 (1.2), stiffness (MPa/mm) 15 (6.7) vs. 15 (5.6), and energy absorption (kJ/m²) 0.5 (0.2) vs. 0.6 (0.4), The same was evident for the new bone formation on the implant surface and around the implant: ongrowth (%) 6 vs. 7 and ingrowth (%) 9 vs. 9. Although not statistically significant, a 61% reduction in fibrous tissue ongrowth and 50% reduction in ingrowth were found in the rinsed group.

Interpretation Within the limits of this experimental model, we did not detect any benefits of rinsing morselized allograft bone prior to impaction grafting.

JBA, JB: design, surgery, analysis, and writing of the manuscript; MS, JEB: design, surgery, analysis, and review of the manuscript; KS: design, analysis, and review of the manuscript.

We thank laboratory technician Jane Pauli of the Orthopaedic Research Laboratory, Aarhus University Hospital, for excellent laboratory work (histological sectioning and histomorphometrical analysis). We also thank the Orthopaedic Biomechanics Laboratory, Minneapolis, for surgical assistance.

This work was supported by the Danish Rheumatism Association, Aarhus University, the Kornings Foundation (Denmark), and the National Institutes of Health (NIH) (grant AR-42051). DePuy Inc. (USA) kindly donated the porous coating. The sponsors did not contribute to the design of the study, evaluation of the results, or to writing of the manuscript.