POSNA examines role of subtalar arthroereisis
Pes planus, or flexible flatfoot, is often left untreated in children because most eventually outgrow the condition. In some children, however, the condition persists and may be associated with considerable pain. When conservative treatment fails, surgical intervention, such as subtalar arthroereisis, may be indicated. Presenters at the 2011 Pediatric Orthopaedic Society of North America (POSNA) Specialty Day program debated the role of subtalar arthroereisis in the treatment of pediatric pes planus.
A successful adjunct to tarsal coalition excision
Subtalar arthroereisis involves inserting an implant into the sinus tarsi through a small incision to block excessive subtalar joint pronation and to elevate the talus. Although Timothy C. Fitzgibbons, MD, and his colleagues at Creighton University/University of Nebraska Medical Center have been critical of use of the arthroereisis implant in the asymptomatic flexible flatfoot patient—especially in patients younger than age 10 years—and have not recommended it in older symptomatic children, they were willing to test its effectiveness in a small study.
The shift in attitude began during a 2006 AAOS continuing medical education course, “Top 15 Foot and Ankle Problems.” Dr. Fitzgibbons listened intently as fellow faculty members discussed the merits of the arthroereisis screw as an adjunct to flatfoot surgery in the adult population.
“Frankly, I was surprised,” he admitted. “But I was also intrigued by the concept of using the arthroereisis screw as a spacer or distractor in tarsal coalition excisions.”
Dr. Fitzgibbons and his colleagues conducted a small prospective study to measure the effectiveness of subtalar arthroereisis screw placement as an adjunct to symptomatic tarsal coalition resection in patients with associated flatfoot deformity. Each of the four patients (aged 11, 13, 16, and 26 years; two male, two female) underwent tarsal coalition resection and placement of a subtalar arthroereisis screw between November 2007 and June 2009. The standard surgical approach for middle facet or calca-neonavicular coalition resection was used on each patient, and the arthroereisis screw was inserted using the sinus-tarsi approach (Fig. 1).
“We initially planned to leave the screws in temporarily, but the patients were doing well, and at 13-month follow-up, we found no radiographic evidence of screw migration,” he explained. No clinical or radiographic evidence of flatfoot deformity recurrence was found, three out of four patients reported no pain, and only one patient underwent removal of the implant during cheilectomy of the talonavicular joint.
Despite the positive outcomes, the researchers were puzzled by the results. “Our goal wasn’t to get correction, it was to try and prevent the coalition from recurring,” Dr. Fitzgibbons said. “The screws were supposed to act as distracters, which would prohibit motion, yet we were surprised that all the patients experienced increased motion.”
Dr. Fitzgibbons continues to believe that the use of the arthroereisis implant in the pediatric or adult patient with an asymptomatic flatfoot is not justified.
“The use of the arthroereisis screw as an adjunct procedure, however, in adult flatfoot surgery and possibly in the adolescent patient undergoing tarsal coalition, seems to be gaining popularity,” he said, “but long-term studies are necessary to truly determine its efficacy.”
Long-term data lacking
Since their introduction in the 1970s, a variety of synthetic subtalar arthroereisis implants and methods for insertion have evolved. As a result of this ongoing search for a better arthroerei-sis implant and/or technique, no long-term follow-up studies report on the overall effectiveness of the procedure, said Vincent S. Mosca, MD, of Seattle Children’s Hospital and the University of Washington School of Medicine, Seattle.
“Subtalar arthroereisis is a joint-restricting procedure. To effectively measure how that restriction of motion affects the ankle, we need studies that go out at least 10 years,” he said.
Dr. Mosca also believes that the number and types of complications associated with subtalar arthroereisis, including inappropriate indi-cations, are underrepresented in the literature. “The flexible flatfoot is normal in babies and in about one out of four adults. If you change that by inserting an implant into the sinus tarsi, I consider that a complication—it is an inappropriate indication,” Dr. Mosca explained.
Surgical complications such as malpositioning the implant can result in overcorrection or undercorrection, and inserting an implant of the wrong size can cause the implant to break and degrade. In addition, biologic complications—including foreign body reaction, synovitis, infection, pain, osteonecrosis of the talus, and calcaneus fracture—can occur with subtalar arthroereisis. These complications are especially concerning because no clear indications for the procedure exist.
“The bottom line is that more information and, in particular, long-term studies are needed before subtalar arthroereisis can be recommended for children with flatfoot deformity—whether painful or painless,” he said. “It’s also important to clarify the surgical indications for the procedure based on the best scientific evidence available.
“Biology trumps technology in these cases,” he said. “The results of biologic surgical approaches for the correction of painful flexible foot deformity in children are the gold standard upon which to compare other methods.”
He concluded, “Based on my review of the literature, I don’t recommend subtalar arthroereisis as a treatment for painful flatfoot deformity in children.”
Disclosure information: Dr. Fitzgibbons—Foot and Ankle International; Dr. Mosca—Journal of Pediatric Orthopedics, Journal of Children’s Orthopaedics.
- Subtalar arthroereisis may be a successful adjunct to tarsal coalition resection in adults and older children with flatfoot deformity.
- Subtalar arthroereisis is associated with a variety of complications.
- The surgical indications for subtalar arthroereisis should be evidence based.
- Long-term studies are needed to prove the efficacy of subtalar arthroereisis in children with flatfoot deformity.
Maureen Leahy is assistant managing editor of AAOS Now. She can be reached at email@example.com