Foot and ankle surgery technology: Cellular bone allografts

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Due to an aging population and contributory comorbidities, foot and ankle arthrodesis procedures are expected to continue to increase in the coming years. Arthrodesis goals are to decrease pain and improve function and quality of life by reversing disability associated with arthritis, trauma, instability, diabetes and malalignment. A successful arthrodesis may be influenced by numerous risk factors, including diabetes mellitus (DM), tobacco abuse, alcohol, osteoporosis, nonsteroidal anti-inflammatory drugs, increased age and large body mass.

Nonunion rates in high-risk foot and ankle arthrodeses have been reported to be approximately 40 percent. Although some nonunions are asymptomatic, patients with symptomatic nonunions go through a great deal of pain and disability. As a consequence of their incapacitation, many of these subjects may not return to work, become addicted to pain medication, and/or suffer from depression.

Autologous corticocancellous bone graft (autograft) has historically been the gold standard as an adjunct for foot and/or ankle arthrodesis procedures. However, harvesting autograft bone often requires a second surgical site and can cause complications such as donor site pain and morbidity, fracture, seroma and infection. Additionally, the quantity of autograft is often limited and the bone quality can be poor, especially in older individuals or patients with notable comorbidities. To counter these issues, a multitude of bone graft substitutes have been developed, ranging from synthetic matrices and bone marrow aspirate to a variety of allografts. However, until recently, none of the bone graft substitutes available consisted of allogeneic bone containing viable osteogenic (bone-forming) cells.

Orthofix and The Musculoskeletal Transplant Foundation (MTF) introduce Trinity ELITE, a third generation allograft with viable cells and improved, putty-like handling properties. As with its market leading predecessors, Trinity Matrix and Trinity Evolution, Trinity ELITE contains all three physiologic properties necessary for bone formation: (1) osteoconductivity provided by its cancellous bone scaffold, (2) osteoinductivity in its demineralized component, and (3) osteogenicity in the viable mesenchymal and osteoprogenitor cells which are native to the cancellous matrix.

Trinity ELITE contains a minimum of 500,000 cells per cc; 100,000 of which are validated to be adult mesenchymal stem cells (MSCs) and/or osteoprogenitor cells (OPCs). These cells are endogenous to the donor cancellous bone particles and are maintained within the bony matrix during processing. In addition to having the viable cancellous component, Trinity ELITE also contains demineralized cortical bone from the same donor. The viable MSCs and OPCs in Trinity ELITE have previously been shown to be capable of proliferating and differentiating into bone-forming cells after thawing and culturing the cryopreserved tissue.

Cellular bone allograft can eliminate the need for harvesting autograft from patients, which, in turn, reduces operative time and expense as well as discomfort and potential complications for the subject. Furthermore, since cellular bone allograft is derived only from donors who meet specific age and health criteria, this bone graft may potentially promote bone formation in high-risk subjects better than autograft, which may have compromised quality due to comorbidities of the patient.

Recently published in Foot & Ankle International, Level II prospective, multicenter, open-label clinical trial included patients undergoing tibiotalar, midfoot, and/or hindfoot fusion using only Trinity Evolution as a bone graft option. This study was designed to enroll patients representative of those seen routinely by the foot and ankle specialist. Thus inclusion criteria were very broad without exclusions for diabetes, obesity, steroids, age and other co-morbidities known to negatively affect fusion rates.

The table below shows the fusion procedure breakdown and patient demographics of this study, which is inclusive of high risk patients. These demographics are typical of the average orthopedic foot and ankle practice. Patients were evaluated post-operatively, clinically and radiographically at six weeks, three months, six months and 12 months post-operatively.

Results
Clinical Endpoints
At three, six and 12 months, radiographic effectiveness was demonstrated with a fusion rate of 66.7 percent, 68.5 percent and 71.1 percent of subjects, respectively, and 79.7 percent, 81.1 percent and 86.8 percent of joints, respectively. High risk patients with diabetes, obesity and age did not have a negative effect on Trinity Evolution fusion rates.

Discussion
Fusion rates using cellular bone allograft were higher than or comparable to fusion rates with autograft that have been reported in the recent literature, and fusion rates were not adversely affected by several high-risk patient factors.

Patients requiring ankle, hindfoot and midfoot fusions often have multiple co-morbidities prolonging postoperative immobilization and delayed return to function which can have a significantly negative impact on quality of life and function, both of which were seen to be improved in this study with Trinity Evolution. This fact and the absence of complications attributable to Trinity Evolution suggest that it is a reasonable alternative to autograft in patients requiring foot and ankle fusion surgery.

Access the full clinical study: http://fai.sagepub.com/content/early/2015/05/13/1071100715586181.full.pdf+html?ijkey=enwSEFmsoeYLA&keytype=ref&siteid=spfai

Sponsored by Orthofix.

 

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