AWARD NUMBER: W81XWH-13-2-0087 TITLE: Optimization of Soft Tissue Management, Spacer Design, and Grafting Strategies for Large Segmental Bone Defects using the Chronic Caprine Tibial Defect Model PRINCIPAL INVESTIGATORS: Dr. Pluhar CONTRACTING ORGANIZATION: Regents

Background: The Masquelet induced membrane technique is a commonly used method for treating segmental bone defects. However, there are no established clinical standards for management of the spacer-induced membrane (IM) prior to grafting. Questions/purposes: Two clinically-based hypotheses were tested in the Caprine Chronic Tibial Defect model: 1) A textured spacer will increase IM surface area will increase bone regeneration; 2) Surgical scraping to remove a thin layer of the inner IM surface will enhance bone formation. Methods: Thirty-two female goats were assigned to four groups: smooth spacer with/without membrane scraping and textured spacer with/without membrane scraping. An initial surgery created a composite defect by excising 5cm of bone, 9cm of periosteum and 10g of muscle. Segments were stabilized with an intramedullary rod and an antibiotic-impregnated polymethylmethacrylate spacer with smooth or textured surface was implanted. Four weeks later, the spacer was removed and the IM was either scraped or left intact before autogenous cancellous bone grafting. Bone formation was assessed using xrays, microCT and histology at 16 weeks. Results: MicroCT analysis demonstrated significantly greater bone formation in defects with scraped IM compared to defects with intact IM (p= 0.041). There were no significant differences in bone formation detected between textured and smooth spacers (p= 0.47). Conclusion: Scraping the IM surface provided a more vascular environment that promoted bone regeneration; however increasing the surface area had no effect. Clinical Relevance: Scraping the IM during the second stage of the Masquelet technique is a rapid and simple means of improving healing of segmental defects.