Of the various materials used, it would appear that the best substitute for fresh autogenous-bone grafts (if mechanical factors are not a consideration) is the organic matrix of bone devoid of its inorganic salt. This conclusion, incidentally, is not new. Nicholas Senn came to the same conclusion in 1889 on the basis of a series of experiments in which filled bone defects with heterogenous bone previously treated with dilute hydrochloric acid. To quote Senn : "Antiseptic decalcified bone is the best substitute for living bone grafts and the restoration of loss of substance in bone . . . [such a] packing furnished the best medium for the growth and development of the tissue resulting from the regenerative process initiated by the trauma." Miller, in a clinical report in 1890, stated that pieces of ox ribs, decalcified with dilute hydrochloric acid and sterilized by soaking in dilute carbolic acid, appeared to be superior to fresh bone in obtaining repair of a tibial defect.

Apparently successful replacement of an implant depends on the readiness with which it can be invaded by vascular elements. The presence of inorganic salts in the implant would appear to impede rather than accelerate the process of replacement. In this connection Cohen, Maletskos, Marshall, and Williams reported that a study of the fate of bone grafts by means of radioactive tracers revealed that all of the calcium incorporated into the callus came by way of the circulating blood from skeletal sources situated throughout the body rather than through diffusion from the graft. Whether any antigenic factors are present in decalcified matrix implants or whether the organic matrix can be further fractionated has not yet been determined.