Study Finds Long-Term Retention Of STAR Implants

For patients with a mobile bearing Scandinavian Total Ankle Replacement (STAR), a recent study notes implants retained at nine years post-op were “highly likely” to survive at 15 years.  

The study, published in Foot and Ankle International, focused on 24 total ankle arthroplasties performed from 1998 to 2000. The authors found a metal implant survival rate of 73 percent at 15 years. In 18 patients, the prosthetic alignment had not changed in comparison with the immediate postoperative radiograph, according to the study. Furthermore, the study authors note that American Foot and Ankle Orthopaedic Society (AOFAS) scores improved by an average of 32 points from a preoperative AOFAS score of 39.6 to an AOFAS score of 71.6 at the time of the study.

The authors note that one patient required a subtalar fusion for symptomatic adjacent joint arthritis and three patients had a broken polyethylene implant component. The study also notes 52 percent of patients with retained implants needed a second surgical procedure with three patients needing two additional surgeries.

Jeffrey E. McAlister, DPM, FACFAS, says the study results of 90 percent ankle replacement retention at nine years and 73 percent at 15 years are “excellent total ankle arthroplasty benchmarks” for data to report to patients and apply to further advancements in total ankle arthroplasty research and innovation.

Dr. McAlister, an attending at the CORE Institute in Phoenix, says his patient population is “doing very well” with the STAR prosthesis and notes a high patient satisfaction rate. He adds that he has only had to revise two implants out of 75 to 100 within the past five years, which included one tibiotalocalcaneal joint fusion and one STAR revision. His experience is similar to the study results, which showed 15 patients having no radiographic signs of osteolysis around either component at 15 years.

The metallic failure rate “seems high,” notes John Grady, DPM, the Director of Podiatric Residencies at Advocate Christ Medical Center and Advocate Children’s Hospital in Illinois. He says the study’s results that over 50 percent of retained implants needed revision surgery is higher than his own experience.

One possible reason for the discrepancy in results may be a difference in the age of implanted patients and the amount of subsequent osteopenia, or that some or most of the additional procedures were not related to the replacement, such as those procedures performed in remote joints or performed secondary to subsequent injuries, according to Dr. Grady.

Dr. Grady, the Scientific Chair of the Midwest Podiatry Conference, also notes the average range of motion in the study is significantly lower than in his own experience. He says the reason for this may be the additional procedures he often does with ankle replacement such as gastrocnemius recession.

Dr. McAlister notes the longevity and survivorship of ankle arthroplasty systems rely heavily on patient selection and initial alignment, specifically in the coronal plane. He says the aim of total ankle arthroplasty should be to decrease pain with activity and adds that the preoperative counseling process is critical to survivorship.

Can Thermograms Be Beneficial In Predicting Diabetic Foot Complications? 

By Brian McCurdy, Managing Editor

A recent study supports the use of thermograms to examine temperatures in the diabetic foot, noting that a change in temperature may correlate with complications.

The study, published in Diabetic Foot and Ankle, examined 186 thermogram findings from patients with diabetes. Researchers note that in a patient with diabetes, an asymmetric thermogram may demonstrate a decreased blood supply, which one may use vascular ultrasound to confirm. The study authors point out that regions of abrupt temperature change, in the form of cold or hot spots, may correspond with ischemia or inflammation.

Stephanie Wu, DPM, notes that studies have shown that high temperature gradients between feet may predict the onset of diabetic neuropathic foot ulcers and self-monitoring along with appropriate foot care may reduce the risk of ulcerations. She says temperature monitoring has identified other diabetic foot complications such as Charcot neuroarthropathy and osteomyelitis.

As Dr. Wu suggests, a multicenter clinical trial over an extended period of evaluation can provide more insight into patients’ long-term adherence to thermogram technology and better evaluate the long-term outcomes and benefits of temperature monitoring.

Although temperature monitoring is non-invasive, the price of an advanced thermal imaging system with high resolution may hinder its wide adoption in clinical practice, according to Dr. Wu, the Associate Dean of Research and a Professor of Surgery at the Dr. William M. Scholl College of Podiatric Medicine, and a Professor of Stem Cell and Regenerative Medicine at the School of Graduate Medical Sciences at the Rosalind Franklin University of Medicine and Science.

“Current research has focused on the feasibility and efficacy of incorporating temperature monitoring into textiles and mats along with smartphone technology to enhance patient adaptation and incorporation into their daily routine,” says Dr. Wu. “Current diabetic foot care is primarily focused on treatment. A shift of focus from treating diabetic foot ulcers to preventing diabetic foot ulcers is needed.”

Does A Longer Second Metatarsal Lead To Plantar Plate Injury?

By Brian McCurdy, Managing Editor

The presence of longer second metatarsals may lead to higher loads under the second metatarsophalangeal joint (MPJ), which may contribute to plantar plate injuries, according to a recent study in Foot and Ankle International.

The study authors retrospectively reviewed weightbearing radiographs and pedobarographic data from 100 patients who were walking without a limp. The study found a positive association between the relative length of the second metatarsal to the first metatarsal with the ratio of peak pressure beneath the respective MPJs. In addition, researchers say the relative length of the second metatarsal to the third metatarsal had a positive association with the ratios of peak pressure, pressure-time integral and force-time integral beneath their respective MPJs.

Craig Camasta, DPM, notes the study suggests that peak pressures are greatest under the second metatarsal but there is no correlation to patients with any plantar plate pathology. He emphasizes that the normal parabola is that the second metatarsal projects the longest “and any direct correlation that a long second metatarsal is causative of plantar plate injuries is unfounded.”  

Dr. Camasta feels first ray pathology more strongly correlates with plantar plate injuries and the number one cause for first ray pathology is hallux valgus. Dr. Camasta advocates using the second toe as a barometer for when there should be strong consideration toward fixing the bunion. If the hallux is crowding the second toe, causing lateral deviation of the second toe or causing the second toe to dorsiflex at the MPJ, fixing the bunion will reduce the chance of the patient developing a plantar plate injury, according to Dr. Camasta, a faculty member of the Podiatry Institute, who is in private practice at Village Podiatry Centers in Atlanta.  

He has also not found that routine shortening of the second metatarsal is necessary to repair a plantar plate injury successfully. Other factors, such as race and gender, are more commonly implicated than second metatarsal length in the development of plantar plate injuries, according to Dr. Camasta.