Bone-Graft Resorption Reduced by the Induced Membrane Technique and Factors Affecting Volumetric Changes

Background: Little is known about the volumetric changes of grafted bone over time when using the induced membrane technique. This study investigates the volumetric changes of bone graft using serial computed tomographic (CT) scans following the induced membrane technique. Methods: Patients with critical-sized bone defects had serial CT scans after undergoing bone-grafting using the induced membrane technique. CT scans to evaluate the volume of bone graft were obtained immediately postoperatively and at 6 and 12 months. The change in the volume of bone graft was determined at 6 and 12 months postoperatively. Patient demographic characteristics, the location and composition of the bone graft, and the type of fixation construct were analyzed. Results: Forty patients met inclusion criteria. There were 27 tibiae and 13 femora with a mean size defect of 8.6 cm (range, 2.5 to 20.6 cm). Of these patients, 21 received autograft with cancellous bone graft and 19 received mixed autogenous bone with demineralized bone matrix (DBM) at a mean time of 17 weeks after the membrane formation. For the first 6 months, there was an overall osseous resorption of −9.9%. The overall graft volume from 6 to 12 months demonstrated an increase of osseous volume by +1.6%. For the entire 12-month period, there was a mean graft volume resorption of −8.3%. A correlation was found between the early volumetric changes of grafted bone and the percentage of DBM in the graft mixture. A correlation was also found between the late volumetric changes and the location of defect or the type of fixation. Conclusions: At 1 year after use of the induced membrane technique for the treatment of a critical-sized bone defect, resorption of the grafted bone averaged −8.3%. The volumetric changes were influenced by the property of the grafted bone, the fixation construct, and the location of the defect. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.