Assessment of MASTERGRAFT PUTTY as a graft extender in a rabbit posterolateral fusion model.

STUDY
DESIGN: Randomized, controlled study in a laboratory setting. Blinded observations/assessment of study outcomes.
OBJECTIVE: The purpose of this study was to determine the performance characteristics of MASTERGRAFT PUTTY as a bone graft extender in a rabbit posterolateral spine fusion model. SUMMARY OF BACKGROUND DATA: The rabbit posterolateral fusion model is an established environment for testing of fusion concepts. It offers the opportunity to obtain radiographical, histological, and biomechanical data on novel fusion materials.
METHODS: Thirty-six rabbits were entered into the study with 30 used for analysis. Bilateral posterolateral lumbar intertransverse fusions were performed at L5-L6. The lateral two-thirds of the transverse processes were decorticated and covered with graft material: autograft only (2.5-3.0 cc per side), 25% MASTERGRAFT PUTTY/75% autograft (3.0 cc total per side), or 50% MASTERGRAFT PUTTY and 50% autograft (3.0 cc total per side). Animals were humanely killed at 8 weeks postsurgery.
RESULTS: The autograft group had a 63% radiographical fusion rate (5 of 8) and correlated with manual palpation results (63%). The 25% MASTERGRAFT PUTTY group had a 73% radiographical fusion rate (8 of 11) and a manual palpation fusion rate of 64%. The 50% MASTERGRAFT PUTTY group demonstrated a 91% (10 of 11) radiographical fusion rate and 73% manual palpation fusion rate. Histologically, no inflammatory reactions were evident regardless of implant. The 2 MASTERGRAFT PUTTY groups had new bone in direct apposition to the MASTERGRAFT ceramic granules.
CONCLUSION: In this commonly used rabbit posterolateral fusion model, MASTERGRAFT PUTTY in an autograft extender mode produces clinically and radiographically similar results to autograft fusion alone.