A flexible, demineralized unitary bone sheet comprised of cortical cancellous bone having a residual calcium weight of 3.0% to 8.0% with a hyaluronic acid component having a molecular weight of 700,000 to 1,500,000 with the weight of the same ranging from 1% to about 5% of the total sheet weight. The bone sheet is adapted for use during the in vivo repair of a mammalian or animal skeletal system with the thickness of the cortical cancellous sheet ranging from 2.0 mm to about 8.0 mm. The bone sheet has sufficient flexibility to allow the sheet to be shaped to conform to the configuration of a skeletal region to be repaired and sufficient tensile strength to allow the sheet to be so shaped without damage to the sheet.