Incorporation of perforated and demineralized cortical bone allografts. Part I: radiographic and histologic evaluation

Massive cortical bone allografts have been found to incorporate slowly into host bone. They are subject to complications such as nonunion, fatigue fracture and infection. In an attempt to improve osteoinduction in cortical bone allografts, laser perforated and partially demineralized cortical bone allografts were orthotopically transplanted into the sheep tibia. In this model, mid-shaft tibial bone allografts from out-bred sheep donor animals were prepared by partial demineralization and drilling of 0.33-mm diameter holes with a pulsed, 2.94-microm wavelength Erbium:Yttrium-Aluminum-Garnet laser. Recipient animals of the same out-bred strain were divided into three groups of eight according to the type of cortical allograft used: group 1, fresh-frozen, no treatment; group 2, laser hole grid; and group 3, laser hole grid and partial demineralization. Plain films were taken in two standard views at monthly intervals. Incorporation was evaluated at nine months postoperatively. Longitudinal radiographic data was correlated to a histologic and morphometric evaluation of each bone graft. Computer tomography was used for the latter analysis. Results showed that untreated allografts, although surrounded by a periosteal bone cuff, were poorly incorporated. Partial demineralization lead to excessive resorption of allografts, but little new bone formation. Laser perforation and partial demineralization induced complete incorporation of allografts into the host bone. Based on the results of the radiographic, histologic and morphometric evaluation, the development of laser-perforated and partially demineralized bone allografts was proposed for clinical use.