Study Focuses On TAR Survivorship After Subtalar Joint Arthrodesis

A recent study in the Journal of Foot and Ankle Surgery evaluated the effect of subtalar joint arthrodesis on talar component subsidence after primary total ankle replacement (TAR) and its effect on ankle replacement survivorship.

The study included 33 patients with ipsilateral subtalar joint arthrodesis with the authors noting that eight patients required a return to the operating room for four revisions and four reoperations at a median follow-up of 24.3 months. In the group of 33 control patients, nine required a return to the operating room with four revisions and five reoperations at a median follow-up point of 38.4 months. The study notes no statistically significant radiographic differences between the two groups and that TAR did not result in decreased survivorship when surgeons combined it with an ipsilateral subtalar joint arthrodesis.

Study lead author Mark Prissel, DPM, says the authors focused on fixed bearing TAR for analysis. He notes that these devices are more common in the United States with more implant options. Specifically with attention to the talus, Dr. Prissel notes the included prostheses did demonstrate some variability including flat-cut implants, such as InBone I and InBone II (Total Ankle Institute/Wright Medical) and chamfer-cut implants, such as Salto Talaris (Integra LifeSciences) designs.

Dr. Prissel notes the study was limited somewhat by chronology in that there were design improvements from InBone I to InBone II in regard to more robust talar fixation with the addition of anterior pegs and improved coronal plane stability with a sulcus design. The aforementioned factors likely did influence the study results as the majority of revisions occurred in the InBone I portion of the cohort and this prosthesis is no longer implanted, according to Dr. Prissel, who is in private practice at the Orthopedic Foot and Ankle Center in Westerville, Ohio.

Lawrence DiDomenico, DPM, FACFAS, has had a positive experience with performing ipsilateral subtalar joint arthrodesis with TAR. If there is a solid fusion, he says the subtalar joint becomes one solid block of bone (talus and calcaneus) and provides a solid platform for the implant.   

To prevent the chance of implant revision, Dr. DiDomenico, who is in private practice at Ankle and Foot Care Centers in Youngstown, Ohio, suggests evaluating each patient individually and thoroughly for pre-op cysts or bony changes with advanced imaging that may require a staged surgery or fusion prior to the index TAR procedure.     

“The best way to prevent revision in this complex patient population is proper selection of appropriate candidates for the procedure and meticulous intraoperative technique to ensure proper placement of the prosthesis,” says Dr. Prissel.

Total ankle replacement technology continues to evolve and improve the available implants, notes Dr. Prissel. He identifies recent trends including improved insertion reproducibility, simplified instrumentation, limiting bone resection for primary implantation and continued advancement in polyethylene science.

Dr. Prissel says there is not yet appropriate sample size to properly analyze the differences among prior, simultaneous and subsequent subtalar fusion in a patient who has had a TAR. He calls for larger studies involving additional prostheses including a larger variety of fixed-bearing as well as mobile-bearing devices.

Do Charcot Wounds Increase The Chance Of Amputation?

By Brian McCurdy, Managing Editor

Having a Charcot-related foot wound at initial presentation increases the chance of having a major lower extremity amputation by a factor of 6, according to a study in Foot and Ankle International.

Researchers focused on 280 feet in 245 patients with diabetic Charcot neuroarthropathy between 2005 and 2015. All the study patients were treated by a single surgeon. Patients were divided into those who presented to the clinic with a Charcot-related foot wound and those who did not have a wound. The study notes that 164 feet with Charcot-related wounds needed 35 amputations in comparison with five amputations in 116 feet without Charcot wounds. The study cites other risk factors associated with major amputation in patients including active infection at presentation, non-union/instability after reconstruction and postoperative wound problems. The authors note the overall rate of successful limb salvage in patients who surgeons deemed to be reconstructive candidates was 90 percent.

For Guy Pupp, DPM, the patients who have the highest risk for major amputation with Charcot include those with wounds and underlying osteomyelitis, bone loss with severe fragmentation and osseous disintegration, and Charcot at the tibio-talar level. He notes patient adherence plays a large part in successfully managing this population.

One should individually evaluate each Charcot patient depending upon the site of the arthropathy (midfoot or ankle), bone loss, infection including soft and hard tissue involvement, metabolic and nutritional status, and vascular status (especially “old” Charcot), according to Dr. Pupp, the Program Director of the Podiatric Residency at Providence Hospital and Medical Center in Southfield, Mich.

He says treatment might range from a tendo-Achilles lengthening with plantar exostectomy to midfoot arthrodesis with a bone graft, beams and circular frame fixation. Dr. Pupp will fuse his “ankle Charcot” patients with a bone graft and intramedullary nail. He will also utilize an orthobiologic and bone stimulator when indicated.

Dr. Pupp attempts to prevent wounds in Charcot patients with appropriate offloading and stabilizing/balancing with prescription shoes, boots and braces. However, when this approach is not successful, he will manage patients surgically. Due to anecdotal observations and “Charcot bone metabolism,” Dr. Pupp says he utilizes an ankle foot orthotic for an extended post-op period.

How Effective Is WIFI In Predicting Limb Loss?

By Brian McCurdy, Managing Editor

Researchers have cited the wound, ischemia and foot infection (WIFI) restaging system for predicting limb loss. A recent study in the Journal of Vascular Surgery says WIFI restaging at one month postoperative may help identify patients at higher risk for limb loss.

This most recent study involved 180 patients with critical limb ischemia who had revascularization, 29 of whom had major amputations. The authors performed WIFI scoring preoperatively, immediately postoperative and at one and six months after intervention. As the study notes, at one month postoperative, the ischemia grade correlated with amputation-free survival but the preoperative ischemia grade did not. Furthermore, one-month post-op grades for wound and foot infection correlated with amputation-free survival.

The goal for WIFI is not specifically to classify wounds, ischemia or infection, but to classify limb threat, notes David G. Armstrong, DPM, MD, PhD. He notes the scoring system includes none (0), mild (1), moderate (2) and severe (3) for wound, for ischemia and for foot infection. He compares the WIFI system to the TNM staging system for cancer, which measures the extent of the tumor, spread to the lymph nodes and metastasis. The system has now been validated in a half dozen large studies in a few thousand patients, according to Dr. Armstrong.

“Let’s face it. The high risk limb in people with diabetes and multisystem disease is very similar to cancer and we have made that case on innumerable occasions, both epidemiologically in terms of morbidity and mortality, and in terms of it being a chronic, complicated and very expensive condition,” says Dr. Armstrong, the Director of the Southern Arizona Limb Salvage Alliance and a Professor of Surgery at the University of Arizona Medical Center in Tucson, Ariz.

With the WIFI system, Dr. Armstrong can tell another physician he has a patient with a score of 3, 2, 3, and the physician will know the patient has a severe wound with moderate peripheral vascular disease, a “severe, raging” diabetic foot infection, and that the limb is (by the combined score) at a very high threat. By grading patients in this manner, he says one can follow them over time.

“A system like this can really be a common language and have a really predictive outcome,” says Dr. Armstrong. “It really is heartening to see the toe and flow, podiatric and vascular surgery, coming together to create a lingua franca to measure and manage the people we treat.”