Autologous cancellous bone has been the “gold standard” for osteosynthesis in clinical applications due to its osteoconductive, osteoinductive, and osteoproliferative potential. For over 100 years, autologous cancellous bone transfers have demonstrated consistent osteosynthetic properties in a wide variety of orthopedic and dental applications. The primary concern associated with autologous cancellous bone grafting has been historically unacceptably high donor site morbidity (with traditional open harvest approaches). Within the past two decades, there has been a widespread adoption of utilizing allograft materials and bone morphogenic protein, in an effort to avoid graft donor site morbidity. Concurrent with this trend, has been the development of a variety of minimally invasive techniques and devices to harvest autologous bone. While the autologous bone harvesting methods have led to a dramatic reduction in donor site morbidity, the level of adoption has not reflected the theoretical appeal, value proposition, and trivial donor site morbidity associated with these new techniques and devices. Unlike allograft tissue, there is no histoincompatibility and while the immunologic response generally does not prevent bone production, it is a potential impediment to graft incorporation ¹. Freeze drying diminishes but does not illuminate immunologic responses to allograft, as matrix proteins contribute to the host immune response ².

A further differentiating feature is the characteristics of the autologous cancellous bone harvested. With some devices, the cellular element is in part separated from its native position in the osseous matrix as a consequence of obligatory suction. Cancellous bone graft is incorporated via a process of creeping apposition ¹. This process commences with vascular ingrowth, which is inhibited by architectural distortion and excessive impaction. In many instances, the autologous cancellous bone is harvested in morselized form, drastically altering the native bone matrix (as a consequence of piecemeal curettage). Studies done on animal models have demonstrated that desiccation or alteration of the normal bone architecture (through morselization and impaction ² ³) inhibits bone incorporation in animal models. Obviously, this type of study cannot be performed in humans, so we are left with animal studies that indicate morselized and impacted bone has a deleterious effect on bone incorporation. In addition, while osteoblasts and mesenchymal stem cells may only survive in a relatively small percentage (as a result of limited revascularization/diffusion needed to support cellular metabolism), preservation of any percentage of these bone-generating cells is likely to have a positive influence on osteogenesis. For these reasons, preserving native bone marrow content, avoiding desiccation, and avoiding architectural distortion will optimize the likelihood of cancellous autograft incorporation. The use of the Corex Bone Harvester provides these advantages and in theory optimizes the potential for graft revascularization, incorporation, and osteoinduction.

1) Clin Orthop Relat Res

1983 Apr: (174): 28-42.
The biology of bone graft repair                                                                                                             H Burchardt                                                                                                                                 

Abstract: Cancellous and cortical autografts histologically have three differences

(1) Cancellous grafts are revascularized more rapidly and completely than cortical grafts;

(2) Creeping substitution of cancellous bone initially involves an appositional bone formation phase, followed by a resorptive phase, whereas cortical grafts undergo a reverse creeping substitution process;

(3) Cancellous grafts tend to repair completely with time, whereas cortical grafts remain as admixtures of necrotic and viable bone. Physiologic skeletal metabolic factors influence the rate, amount, and completeness of bone repair and graft incorporation. The mechanical strengths of cancellous and cortical grafts are correlated with their respective repair processes: cancellous grafts tend to be strengthened first, whereas cortical grafts are weakened. Bone allografts are influenced by the same immunologic factors as other tissue grafts. …The matrix proteins may or may not elicit graft rejection. The rejection of a bone allograft is considered to be a cellular rather than a humoral response, although the humoral component may play a part. The degree of the host response to an allograft may be related to the antigen concentration and total dose. The rejection of a bone allograft is histologically expressed by the disruption of vessels, an inflammatory process including lymphocytes, fibrous encapsulation, peripheral graft resorption, callus bridging, nonunions, and fatigue fractures.

2) Bone and Cartilage Allograft

Chapter 1                                                                                                                                      “Biology of Autografts and Allografts”                                                                                          Victor M. Goldberg, Sharon Stevenson, John W. Shaffer

3) Clin Orthop Relat Res 1998 Jul: (352): 231-8.                                                                  Impaction of cancellous bone grafts impairs osteoconduction in titanium chambers                     M Tägil, P Aspenberg

Abstract: The method of using morselized compacted cancellous allografts for hip arthroplasty revision shows results that seem to differ dramatically from other kinds of allografting. In structural cancellous allografts, bone ingrowth usually is limited to 2 to 3 mm, whereas morselized compacted grafts seem to be remodeled totally in several cases, as judged by radiography. In the current study, impacted cancellous allografts were compared with unimpacted allografts. Seventeen rats had a bone conduction chamber implanted in the tibias bilaterally. On one side the chambers contained an impacted graft (bone volume fraction 65%) and on the contralateral side an unimpacted graft (bone volume fraction 35%). Impaction of the grafts was done preoperatively with a pressure of either 25 or 2500 MPa. Ingrowing bone could enter the cylindrical interior of the chamber only at one end. After 6 weeks the mean distance the ingrown bone had reached into the graft was measured on histologic slides. With both impaction pressures, the bone ingrowth distance was decreased to 30% of the unimpacted controls. It appears that impaction alone does not have a favorable effect on the osteoconductive properties of a bone graft. On the contrary, impaction seems to disfavor osteoconduction. However, in the clinical situation this is not necessarily a disadvantage.

4) Acta Orthop Scand Suppl 2000 Feb: 290: 1-40.

The morselized and impacted bone graft. Animal experiments on proteins, impaction and load

M Tägil                                                                                                                                                     

“…The impacted grafts were compared to unimpacted ones and it was shown that impaction reduced the ingrowth of new bone into a graft in the chamber at six weeks. In Paper III, this somewhat unexpected finding was further studied. Syngeneic and allogeneic grafts showed a reduced ingrowth distance at six weeks when impacted, compared to unipacted controls.…”