In this episode, we explore the science and clinical applications of bone grafting in foot and ankle surgery. We discuss the history of bone transplantation, the biological principles of osteoconduction, osteoinduction, and osteogenesis, and the differences between autografts, allografts, synthetic bone substitutes, and orthobiologics. We examine common graft harvest sites, including the iliac crest, proximal tibia, distal tibia, and calcaneus, and explain how grafts are used in hindfoot fusions, flatfoot reconstruction, revision surgery, and the treatment of bone loss. We also discuss graft selection, complications, evidence-based decision-making, and patient expectations during recovery.
The history and evolution of bone grafting: Bone grafts have been used for centuries, beginning in 1668 when a piece of bone from a dog's skull was used to repair a cranial defect in a Russian soldier. The first autograft was successfully performed in 1821, meaning this technique has centuries of experience and science behind it.
This episode is broken into sections:
The biology of bone healing. We reviewed this in prior episodes, but the key concept are osteoconduction, osteoinduction, and osteogenesis. Conduction refers to a scaffolding that adjacent bone cells can use to integrate a graft. Induction is the biological stimulation by the graft to incorporate, and osteogenesis refers to using orthobiologics to cause bone formation. Different grafts perform different functions, sometimes combinations of functions, and the specific needs of a surgery dictate the choice of graft material.
Autograft versus allograft. This refers simply to whether the origin is the patient themselves or some external source.
Structural and cancellous bone grafts. Structural grafts are used to maintain position or alignment, while cancellous grafts are primarily void fillers.
Demineralized bone matrix and synthetic substitutes. While not structural, these aid in fusions where bone cell contact with like cells promotes osteointegration and successful bridging of defects.
Bone marrow aspirate and growth-factor-based orthobiologics. Newer technologies have become standard in revision and reconstructive surgery, with these being used to supplement traditional grafting, not replace it.
Graft selection for fusion, deformity correction, and revision surgery. Surgeons are faced with a wide variety of conditions that require grafting. Therefore the myriad of available products have to be considered as there is no one size fits all. A specific type of graft or material in one situation may be entirely inappropriate in another.
Donor-site morbidity and graft-related complications. Specific to autografts, harvest sites may present their own complications unrelated to the primary procedural region. This is why selection of an autograft should outweigh the risks of donor site comorbidity over using an allograft.
Patient optimization and postoperative recovery. Grafting by its very nature is tedious, and implies perfect anatomy, apposition, alignment, biology, or blood supply may be constrained. If you remember back to our bone healing episode, the ideal situation is primary bone healing, which requires direct approximation of biologically intact bone ends with rigid fixation. The use of a graft in an intervening space will necessarily skip this for secondary bone healing, or something other than direct vascularization.