The Effect of Surgical Technique and Spacer Texture on Bone Regeneration: A Caprine Study Using the Masquelet Technique.

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 induced membrane before grafting. QUESTIONS/PURPOSES: Two clinically based theories were tested in a chronic caprine tibial defect model: (1) a textured spacer that increases the induced-membrane surface area will increase bone regeneration; and (2) surgical scraping to remove a thin tissue layer of the inner induced-membrane surface will enhance bone formation. METHODS: Thirty-two skeletally mature female goats were assigned to four groups: smooth spacer with or without membrane scraping and textured spacer with or without membrane scraping. During an initial surgical procedure (unilateral, left tibia), a defect was created excising bone (5 cm), periosteum (9 cm), and muscle (10 g). Segments initially were stabilized with an intramedullary rod and an antibiotic-impregnated polymethylmethacrylate spacer with a smooth or textured surface. Four weeks later, the spacer was removed and the induced-membrane was either scraped or left intact before bone grafting. Bone formation was assessed using micro-CT (total bone volume in 2.5-cm central defect region) as the primary outcome; radiographs and histologic analysis as secondary outcomes, with the reviewer blinded to the treatment groups of the samples being assessed 12 weeks after grafting. All statistical tests were performed using a linear mixed effects model approach. RESULTS: Micro-CT analysis showed greater bone formation in defects with scraped induced membrane (mean, 3034.5 mm3; median, 1928.0 mm3; quartile [Q]1-Q3, 273.3-2921.1 mm3) compared with defects with intact induced membrane (mean, 1709.5 mm3; median, 473.8 mm3; Q1-Q3, 132.2-1272.3 mm3; p = 0.034). There was no difference in bone formation between textured spacers (mean, 2405.5 mm3; median, 772.7 mm3; Q1-Q3, 195.9-2743.8 mm3) and smooth spacers (mean, 2473.2 mm3; median, 1143.6 mm3; Q1-Q3, 230.2-451.1 mm3; p = 0.917). CONCLUSIONS: Scraping the induced-membrane surface to remove the innermost layer of the induced-membrane increased bone regeneration. A textured spacer that increased the induced-membrane surface area had no effect on bone regeneration. CLINICAL RELEVANCE: Scraping the induced membrane during the second stage of the Masquelet technique may be a rapid and simple means of improving healing of segmental bone defects, which needs to be confirmed clinically.

Fatigue analysis of plates used for fracture stabilization in small dogs and cats.

OBJECTIVE: To evaluate the fatigue life of stacked and single, veterinary cuttable plates (VCP) and small, limited contact, dynamic compression plates (LC-DCP). STUDY DESIGN: In vitro biomechanical study. METHODS: Fracture models (constructs; n = 8) were assembled for each of 6 groups all with 8-hole plates: 2.0 mm LC-DCP; 2.4 mm LC-DCP; single 1.5/2.0 mm VCP; stacked 1.5/2.0 mm VCP; single 2.0/2.7 mm VCP; and stacked 2.0/2.7 mm VCP. Plate(s) were secured to 2 polyvinylchloride pipe lengths, mounted in a testing system with a custom jig, and subjected to axial loading (10-100 N) for 1,000,000 cycles at 10 Hz or until failure. Differences in number of cycles to failure among groups were compared. Failure mode was determined. RESULTS: All LC-DCP and single VCP constructs failed before 1,000,000 cycles. Stacked 2.0/2.7 mm VCP constructs withstood 1,000,000 cycles without failure. ANOVA and Fisher's least significant difference tests demonstrated significantly more cycles to failure for the stacked 1.5/2.0 mm VCP and stacked 2.0/2.7 mm VCP compared with the single 1.5/2.0 mm VCP, single 2.0/2.7 mm VCP, 2.0 mm LC-DCP, or 2.4 mm LC-DCP. Constructs that failed did so through a screw hole adjacent to the gap. CONCLUSION: Stacked VCP constructs have greater fatigue lives than comparably sized LC-DCP or single VCP constructs. Plates with 2.4 mm screws were not significantly different from the comparable construct with 2.0 mm screws. CLINICAL RELEVANCE: Although these data reveal that stacked VCP create a superior construct with respect to cyclic fatigue, surgeons must decide whether this is a clinical advantage on a case-by-case basis.