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Ankle allograft replacement may be indicated for patients with lower BMI
Surgeons still see a high revision rate in younger, thinner patients because they are more active.
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Researchers recently found a high failure rate and high revision rate in patients who underwent osteoarticular ankle allograft replacement, which they attributed to high body mass index and a more active patient population.
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Images: Kadakia AR |
Anish Raj Kadakia, MD, of the University of Michigan in Ann Arbor, and Mark S. Myerson, MD, and Clifford Jeng, MD, at the Foot and Ankle Institute at Mercy Medical Center in Baltimore conducted a study on 29 bipolar osteoarticular allograft replacements in patients with an average age of 41 years.
At a mean follow-up of 18 months, the researchers found a 34% revision rate and a 62% clinical and radiographic failure rate. Those patients who failed were significantly younger, had a higher mean body mass index (BMI) and larger coronal plane deformity at preop.
Although the younger patients were ideal for this operation, they were also more active, which may have caused some failures.
“It’s kind of a ‘Catch-22’ that they’re the ones that you need to do the procedure on, but they’re also the ones who are going to use this [allograft] more actively,� Kadakia told Orthopedics Today.
He also attributed the high failure rate to technical error and graft fracture in the early failures, and to immunologic rejection in the late failures.
“The bone graft and cartilage were initially thought to be immunoprotected … but there’s a lot of thinking that this is not the case and there is some sort of ‘rejection’ of the grafts,� Kadakia said.
High revision and failure rates
Intraoperatively surgeons made cuts using the Agility (DePuy Inc.) ankle arthroplasty jigs, which helped them to precisely standardize and match the cuts for the patient and the graft, Kadakia said.
At follow-up, researchers labeled as failures those patients with persistent pain, recurrent radiographic arthritis, allograft collapse, allograft fracture or revision, according to a study abstract.
Nineteen patients (66%) retained the graft at follow-up, and the remaining 34% had radiographic and clinical failure and required revision.
Of the 19 patients who retained the graft, 11 patients (38%) had clinical and radiographic success. Eight patients had radiographic or clinical failure, but six have not undergone revision surgery because they are functioning adequately and prefer not to have another surgery, Kadakia said.
Reasons for allograft failure included: five (17%) tibial allograft fractures, two (7%) talar allograft fractures, five (17%) tibial allograft collapses and five patients (17%) with recurrent arthritis, according to the abstract.
Reasons for failure
In evaluating the factors for failure, researchers found that the patients with clinical and radiographic success were significantly older with a mean age of 46 years, compared to 38 years for those patients with radiographic failure (P<.05).
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Patients with radiograph success also had a lower mean BMI, 24, compared to 28 in patients with failures. And they had a lower coronal malalignment of 2°, compared to 6° in the patients with failures.
The researchers also evaluated the allografts for donor age, duration to implantation, tibial and talar graft thickness and allograft size match, but found no association with failure.
To avoid failure, Kadakia suggested that surgeons carefully select patients for this procedure, that they handle the implantations with care, use the cutting guides for accuracy, and place the graft early because cartilage is nonviable after 18 days.
He added: “One of the key factors for future success is studying the immunologic rejection of grafts, just as they do for kidney transplants and other transplants.�
For more information:
- Kadakia AJ, Jeng C, Myerson M, et al. Osteoarticular ankle allograft replacement. Presented at the American Orthopaedic Foot and Ankle Society 22nd Annual Summer Meeting. July 14-16, 2006. La Jolla, Calif.