Can We Improve Fusion Rates With Bone Marrow Aspirate?

Foot and ankle surgeons often face the challenge of obtaining adequate bone healing in a timely fashion in patients with multiple risk factors for poor bone healing. Smoking, diabetes, Charcot, a history of high energy injury, multiple surgeries at an osseous surgical site, a history of delayed or nonunion, a history of avascular necrosis, alcohol abuse, immunosuppression, acute/uncontrolled infections, chronic infections, a poor soft tissue envelope and suboptimal vascularity are just a few of the many risk factors for poor bone healing.

   Careful preparation of opposing bone surfaces, compression across the arthrodesis or healing site, and the use of internal fixation to limit external stresses are all required for successful healing of bones and arthrodesis procedures. Loss of bony structure and volume is common at sites of fusion and fracture. Therefore, one may add bone graft to fill defects and/or increase the volume of bony mass.

   Surgeons commonly utilize bone grafts in reconstructive foot and ankle procedures. Historically, the autologous cortical and cancellous bone graft originated in the iliac crest and was considered the standard of care. In response to the potential morbidity associated with iliac crest bone graft, several techniques have emerged using other donor locations and modalities in order to obtain such grafts.

   Goujon first demonstrated the osteogenic capacity of bone in rabbits.1 Since the 1960s, some authors have shown that osteogenic stem cells in bone marrow are responsible for the biological efficacy of cancellous bone. Connolly and co-workers demonstrated a positive correlation between bone marrow osteogenic capacity and cell concentration, and researchers have successfully treated nonunions clinically with autologous bone marrow grafting alone in animal experiments.2

   Hernigou and colleagues have confirmed the effectiveness of concentrating bone marrow for the treatment of atrophic nonunions.3 However, the efficacy appears to be related to the concentration of progenitor cells in the graft. A concentration of five times or higher yielded a 100 percent fusion rate. Aspirating bone marrow from the iliac crest appears to be less than optimal in the absence of concentration.

   A successful bone graft must contain osteogenic progenitor cells as well as osteoconductive and osteoinductive material for optimal healing potential. Tiedeman and colleagues reported beneficial effects of osteoprogenitor cells found in autogenous bone marrow aspirates in an uncontrolled study.4 Research by Muschler and co-workers has led to improvement in obtaining a richer concentration of progenitor cells from the bone marrow harvest.5

Pertinent Pearls On Obtaining Bone Marrow Aspirate For Fusions

The lateral calcaneus is an alternative to iliac crest and proximal tibia donor sites. Surgeons should only choose this site when 30 mL of aspirate is required. This is commonly the case for a midfoot or forefoot procedure. Biomet’s BioCUE bone marrow concentration kit provides 80 percent recovery and eight times the concentration of mesenchymal stem cells.

   We make a small incision on the lateral side of the ankle, anterior to the insertion of the Achilles tendon down to the calcaneus. One would insert the BMA needle anterior to the Achilles tendon and posterior to the sural nerve. Position the BMA needle at a maximum depth through the calcaneus. Advance the trocar medial to dorsal from the insertion point. Proceed to insert the needle to a maximum depth of 3 cm or until you meet resistance from cortical bone on the side opposite the insertion point.

   Remove the trocar and connect the anticoagulant syringe to the BMA needle. Aspirate 2 to 4 mL of bone marrow, withdraw the needle an additional 1 cm and repeat the aspiration. Repeat this process until the BMA needle is positioned in cancellous bone. Postoperative pain at the aspiration site is rare.

   The marrow is concentrated via removal of erythrocytes and plasma from the aspirate. One would directly inject the concentrated bone marrow aspirate into the joint being fused. Usually, this occurs along with subchondral drilling to augment the healing and rate of fusion. Patients are required to be non-weightbearing in a cast for at least eight weeks.

   While there is literature on the use of bone marrow aspirate in spinal fusion, there are currently no published studies on the fusion rate in foot and ankle surgery with bone marrow aspirate. Incidentally, we have found that patients who receive the BMA in conjunction with their fusion generally have shown radiographic signs of fusion at their arthrodesis site approximately two weeks earlier than control patients.

In Conclusion

Bone-marrow-derived mesenchymal stem cells may provide an emerging option for improving fusion rates in foot and ankle arthrodesis procedures. Mesenchymal stem cells make up 2 to 3 percent of the total mononuclear cells in bone marrow. They have the capacity to differentiate into various cell types, including osteoblasts and chondrocytes. Mechanical stimulation, present growth factors and the new environment can all influence the direction in which the stem cells differentiate. These cells regenerate tissue and support angiogenesis.

   Further studies are needed to determine if the role of bone marrow aspiration in foot and ankle surgery is effective over a broader range of patients, and if it augments or speeds up the healing of arthrodesis procedures and/or nonunion/ delayed unions.

   Dr. Chandler is a Fellow at the University Foot and Ankle Institute in Los Angeles.

   Dr. Baravarian is an Assistant Clinical Professor at the UCLA School of Medicine. He is the Chief of Podiatric Foot and Ankle Surgery at the Santa Monica UCLA Medical Center and Orthopedic Hospital, and is the Director of the University Foot and Ankle Institute in Los Angeles.

References
1. Goujon E. Recherches experimentales sur les proprietes physiologiques de la moelle des os. J Anat Physiol. 1869;6:399-412.
2. Connolly J, Guse R, Lippiello L, Dehne R. Development of an osteogenic bonemarrow preparation. J Bone Joint Surg Am. 1989;71(5):684-91.
3. Hernigou P, Poignard A, Beaujean F, Rouard H. Percutaneous autologous bone-marrow grafting for nonunions influence of the number and concentration of progenitor cells. J Bone Joint Surg Am. 2005;87-A:1430-1437.
4. Tiedeman J, Garvin K, Kile T, Connolly J. The role of a composite, demineralized bone matrix and bone marrow in the treatment of osseous defects. Orthopedics. 1995;18(12):1153-1158.
5. Muschler G, Boehm C, Easley K. Aspiration to obtain osteoblast progenitor cells form human bone marrow: the influence of aspiration volume. J Bone Joint Surg Am. 1997;79(11):1699-1709.

Additional References
6. Jia X, Peters P, Schon L. The use of plateletrich plasma in management of foot and ankle conditions. Oper Tech Sports Med. 2011;19:177-184.
7. Fitzgibbons T, Hawks M, McMullens S, Inda D. Bone grafting in surgery about the foot and ankle: indications and techniques. J Am Academy Orthop Surgeons. 2011;19(2): 112-120.