by Dempsey S. Springfield, MD
Dempsey S. Springfield, MD, is the Robert K. Lippmann Professor of Orthopaedics; chairman, department of orthopaedics; and orthopaedic surgeon-in-chief, Mount Sinai Medical Center, New York.
I recently had a patient with a benign bone tumor whom I treated with a curettage and an autogenous iliac crest bone graft. She is a horseback riding instructor and physically active. Both of her wounds healed without difficulty. This was a relief after one of the residents showed me Younger and Chapman's1 article on the complications of autogenous bone grafts. Younger and Chapman reviewed 239 patients who had 243 autogenous bone grafts and found an 8.6 percent incidence of what they called "major" complications and a 20.6 percentincidence of "minor" complications. Patients rarely think of complications being major or minor. Any complication is a major problem for a patient.
I thought everything was going well with my patient. Her bone lesion healed quickly and I was able to let her start back to her usual activities eight weeks after the surgery. Then she became one of the 8.6 percent "major" complications. She sustained a fatigue fracture of the iliac crest anteriorly to the defect produced by harvesting her graft. This began an almost nine-month saga of decreased activities, difficulty at work and frustration until the fracture finally healed and she was able to get back to her full activities. I was distraught. She was destroyed.
Since then I have been thinking and reading about alternatives to conventional autogenous bone grafts. There are a number of substitutes for autogenous bone grafts, all of which eliminate the need for harvesting the patient's own bone, although the addition of bone marrow is recommended for some. For those interested, there is an excellent review by Costuntino and Friedman2 in the ENT literature.
Allograft bone has been used as a substitute for conventional bone grafts for at least 150 years. During the past 20 years it has become accepted and widely-used. It can be stored as fresh frozen bone in a freezer or as freeze-dried bone at room temperature. In a recent advertisement for allograft bone, Lee Trevino is shown swinging a golf club, presumptively after his neck fusion, which was done using allograft bone, probably freeze-dried. The reader is probably supposed to think their golf game will improve if allograft is used.
A few years ago it was common for femoral heads removed at the time of a routine total hip replacement to be saved for later use as a bone graft. The risk of transmitting a viral disease has made this practice almost extinct. Large, well-managed bone banks have replaced the single-institution "freezer in the OR" banks and safe bone is available, but the risk of viral transmission remains at least a theoretical possibility.
Allograft bone is especially attractive when a larger segment of bone needs to be replaced, but it also can be used to fill smaller defects. It has a slightly higher risk of postoperative infection compared to autogenous bone grafts and it has only osteoconductive properties but it is an adequate substitute for autogenous bone graft.
According to the advertisements in our journals, synthetic bone grafts are just as good as autogenous bone grafts. Can we believe them? The added benefit over allograft is that the synthetic substitutes do not have a risk of viral transmission. Interpore® is advertised heavily in our journals and is said to be "As good as gold." It is supposed to have the "equivalent" rates of healing, as autogenous grafts. It is calcium hydroxyapatite made from chemically-altered marine coral. It is nonresorbable and has a chemical composition similar to bone. It is not as strong as bone, and is not to be used to improve screw fixation, in areas of reduced blood supply or in patients with nutritional disorders. Sounds as if it is of limited use.
Collagraft® is another bone graft substitute available. It is purified type I, bovine dermal fibrillar collagen (PFC) and a mixture of ceramic hydroxyapatite granules (65 percent) and betatricalcium phosphate granules (35 percent). It is recommended that autogenous bone graft or, at least, bone marrow be added to this material and so it should be considered a bone graft extender not a substitute. Unaltered marine coral (a calcium carbonate) can be used as a substitute, but this material is resorbed by the patient.
These substitutes and additives may have their place in orthopaedic surgery, but it is unlikely they will replace autogenous bone grafts any time soon. Autogenous bone grafts provide both osteoinductive and osteoconductive stimuli for bone growth. Autogenous bone grafts can be large cortical segments or corticocancellous curetting. They can be used to provide mainly mechanical support or mainly to stimulate new bone formation. When the host bed is compromised, autogenous bone can bring its own blood supply and even when the host has metabolic disorders the autogenous bone functions well. Autogenous bone is still the gold standard and the best source of bone graft.
What does the future hold? The immediate future of bone grafts will probably include further refinements of the current synthetic materials. These will continue to provide osteoconductive stimuli only. I suspect they will be sublimated with osteoinductive factors as soon as these factors can be commercially synthesized. Further in the future, I believe we will have synthetic materials of sufficient quality that we will not need to use autogenous bone grafts and that we will have the technology to induce bone formation without any graft materials, but for now the patient is their best own donor.