Do I Need to Use Bone Graft for Foot or Ankle Surgery? Which Graft Should I Use—Autologous or Allograft?
Christopher
Bibbo,
DO, FACS, FAAOS
The foot and ankle surgeon commonly encounters situations where patients possess risk factors for bony healing problems (Table 49-1), have had same-site failed surgeries, or have bone defects that will require restoration of bone stock.1-3
To begin, common sense is paramount in treating patients and assessing risk factors. When it appears that bone will be needed, currently there is no equal substitute. The decision whether allograft or autograft is needed is based on patient stratification, surgical needs, and clinical situation (Figure 49-1). It is the author’s preference that when bone graft is needed, autograft is the bone source of choice. Allograft is certainly an acceptable bone graft in patients where structural material is needed to restore length, fill defects, or correct deformity in an area that is richly vascularized (such as cancellous bone or cortical bone with a large muscle bed over it) in patients who are not at risk for bone healing problems. For example, in a normal, healthy young patient in whom an Evans procedure or other similar lateral column lengthening is being performed, allograft is certainly acceptable. If the patient has a high risk for a nonunion, then autograft is preferred. In patients where the area is not richly vascularized, not only do we need bone, but we need osteoprogenitor cells; both osteoinductive and osteoconductive properties are needed in the bone graft. In this instance, autograft is again the preference (Figure 49-2). Whether it is richly vascularized or not richly vascularized, in an anatomical area where there is a defect or deformity in a patient that has significant risk factors for bone healing problems, autograft is preferred. The use of bone substitutes in place of bone is unacceptable (eg, photo-oxidized bovine bone or polyglycolic/polylactate materials are unsuitable in place of human bone).4,5
Figure 49-1. Two starkly contrasting cases. (A) Elective first tarsometatarsal fusion in a healthy young adult where bone graft is not needed, compared to (B) a high-energy open pilon fracture in a smoker that will require bone grafting and osteobiologic augmentation.
Figure 49-2. Six-centimeter iliac crest autograft used to reconstruct multiple nonunions of the medial column (outlined) in a high-risk patient. The construct fused uneventfully and the patient experienced only minimal, transient donor site morbidity.
A common question arises in patients who are in the ambulatory setting, have low risk factors, and are undergoing procedures that have known risk for nonunions (eg, talar navicular fusions, metatarsophalangeal joint fusion, and Lapidus procedures). It is a common question to ask if there is anything to be done to specifically enhance the union rates in these situations and if bone is actually required. My answer to this question is that proper surgical technique can generally suffice without the use of additional bone. Additional bone that can be harvested locally can be used if there is a defect. If a question still arises, we use adjuvant modalities such as platelet-rich plasma in my practice.6 The assessment of the need for bone graft, as well as adjuvant osteobiologic agents, has been proposed by me in my Host-Surgical Site classification system,6 which uses a 4-category system that stratifies patients into risk classes that correlate with surgical needs for bone graft and osteobiologic adjuvants (Figures 49-3 and 49-4).
Figure 49-3. Bibbo Host-Surgical Site classification to assess the need for bone graft and osteo-adjuvants. (Reprinted with permission from Bibbo C, Hatfield PS. Platelet-rich plasma concentrate to augment bone fusion. Foot Ankle Clin. 2010;15(4):641-649.)
Figure 49-4. Schematic hierarchy of risk factors, bone graft, and osteobiologic adjuvants. (Reprinted with permission of Dr. C. Bibbo.)
When dealing with larger reconstructions, the iliac crest remains the single best source for autologous bone graft (see Figure 49-1). Unfortunately, both clinicians and patients commonly have an aversion to harvesting iliac crest bone, with a common citation of high donor site morbidity. It is the author’s experience that patients experience transient donor site discomfort, but residual sequelae and complications are very low, even in obese and morbidly obese patients (Bibbo C, unpublished data). This author’s observation echoes the finding of DeOrio and Farber that the morbidity in harvesting iliac crest is actually quite low and that, when complications occur, they are transient and minor in nature7 and iliac crest bone graft should be sought when needed. Even allograft sources carry risks, particularly delayed and nonunions, infection, and fatigue fracture.8,9 In an effort to avert the perceived morbidities from iliac crest harvest site morbidity and to avoid the use of allograft, local (more easily accessed) bone graft harvesting techniques have become popular. Sources for local bone include the calcaneus, the cuboid, medial malleolus, distal tibia, and proximal tibia. However, even “local” bone graft harvests have demonstrated a 9% complication rate.10 The surgeon must be warned that the quality of bone from these sites is highly variable, the quantity limited, and, for the majority of foot and ankle cases, adequate. For example, in an elderly patient, the author has noted that the proximal tibia quite often yields only fatty marrow and is a poor source for bone graft. Recently, the author’s observations have been confirmed histologically by other investigators who demonstrated that proximal tibial graft sites yield a more fatty marrow than the iliac crest, which consistently yields a graft with a robust level of cellular activity.11
The most richly vascularized and highly populated area (with stem cells) is still the iliac crest. As the body grows older, the areas for reserves of stem cells decreases throughout the body.12,13 It appears that the iliac crest may be the best site for osteoprogenerative cells, but even this diminishes as aging ensues. These data do not, however, fully address the questions of precursor cell recruitment (graft cytokine levels) in the overall function of bone grafting. A “2-stage” hypothesis theory has been proposed to explain the fate of mesenchymal cells in-vitro, implicating that microenvironmental cues (soluble factors) are part of the complex biology of cellular (osteoprogenitor) differentiation and its role in bone healing.14 Despite these data, many clinicians still use proximal tibial bone graft, despite the evidence that the iliac crest provides the most active, robust source for autologous bone. This author follows simple, sound clinical reasoning that expounds the philosophy that, in general, when bone graft is needed, the source is dictated based upon risk factors, the age of the patient, and specific needs (amount structural versus nonstructural).
All osteo-adjuvant modalities, including platelet-rich plasma, demineralized bone matrix, and bone morphogenetic protein are adjuncts to bone healing, and are not substitutes for human bone (both autograft and allograft). A simple way to stratify the assessment of patients for the need for both bone grafting and adjuvant osteobiologic agents has been proposed by me in my classification system,6 which uses a surgical site and surgical candidate scale to assess the risk and need for adjuvant material. Adjuvants that can be used include platelet-rich plasma, demineralized bone matrix, bone morphogenetic protein, etc. The use of tricalcium sulfate materials and bone void fillers are simply bone void fillers that allow creeping substitution. Thus, they must be used in a well-contained defect in an area that is richly vascularized. Bone graft filler materials have no application in the reconstruction of cortical defects.
Conclusion
The use of bone graft in foot and ankle surgery is based on a sound, common sense assessment of the clinical situation, as well as host risk and surgical site risk factors. The traditional teaching for the use of bone graft still holds. When bone graft is needed to fill defects, span bone voids, correct alignment, and, when coupled with increasing risk factors, autogenous bone graft is to be used. The consideration that there is unacceptably high second surgery site morbidity has really not been completely substantiated, and, in the author’s clinical experience, even large bone grafts in the morbidly obese patient can still result in good long-term results with minimal second site morbidity. Thus, for most purposes, in at-risk patients, autologous bone graft trumps allograft. However, there are certain situations where allograft will remain a valuable component in the surgeon’s armamentarium. Risks of using allograft (frozen and freeze dried) increase depending on the size of the graft used. In large allograft constructs, incorporation of the allograft may take many months, if not years. In large foot and ankle reconstructions, allograft may be subject to fatigue failure and may also act as a nidus for inflammation and infection. At times, combinations of allograft and autograft must be used because there are limitations on the amount of autograft that can be harvested. Nonetheless, the use of any bone graft must be weighed against host risk factors (ex, smoking, diabetes), surgical site risk factors, (ex, vascularity of the area), and the demands of the proposed surgical construct. Thus, bone graft is not needed in every foot and ankle surgery, but rather it is dictated by host factors, surgical indications, as well as the surgical technique required to meet the operative demand of each individual patient.
References
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