Procedure: retrieve massive allograft
Allograft constructs removed because of infection or cancer complications will be retained for biomechanical testing

Allograft bone is the primary source of graft material for large skeletal defects resulting from trauma, disease, oncological resection, or reconstruction of failed total joint arthroplasties. The physical characteristics of such grafts after various intervals of remodeling and incorporation in vivo have never been studied.

The purpose of this study is to obtain tissue from allografts retrieved at autopsy, at amputation for oncological complications and from patients undergoing revision procedures for failed allograft transplantation. We will evaluate the mechanical properties, histomorphometric indices and presence of microfractures.

Our hypotheses are:

• histomorphometric parameters of porosity and microfracture density will predict allograft strength,
• microfracture density will be correlated with time in vivo and allograft strength,
• the rate of host-allograft nonunion and fracture will correlate with radiation therapy and chemotherapy.

The retrieved tissue will be processed using standard undecalcified histology and quantitatively assessed for degree of incorporation, allograft porosity, and microfracture density. The biomechanical characteristics of the bulk allograft and allograft-host junction will be quantified and compared to allograft bone prior to transplantation.