Good results with new MTP-1 prosthesis

Procedure for the three-piece device calls for short flexor tendon sparing.

Early results with a new, metatarsophalangeal prosthesis demonstrated a 37-point increase in foot and ankle scores.

The three-piece implant may offer surgeons another option for grade 2 and 3 arthrosis. “We get excellent results with two- to five-year follow-up,” said Hakon Kofoed, MD, an orthopedist at Frederiksberg Hospital in Denmark.

“All the components grow in very fast and the AOFAS score increased from 48 to 85,” he said during his presentation at the American Orthopaedic Foot and Ankle Society 21st Annual Summer Meeting.

In his study of 36 total joint replacements using the Roto-Glide implant (Implants International, U.K.) Kofoed reported four complications. One patient developed skin necrosis, and in another, the metatarsal component was too large. Surgeons removed the device in both cases. Two other patients showed subluxation of the meniscus, but were asymptomatic and the device was left in place.

“We found that the patients who had the prosthesis removed could easily be transformed into an arthrodesis,” Kofoed said.

Three-part prosthesis

Kofoed inserted the implant in 30 women and six men diagnosed with grade 2 or 3 arthrosis in the metatarsophalangeal (MTP)-1 joint. The uncemented device features the following three parts: a metal metatarsal head, a metal phalangeal portion and a polyethylene meniscus, which is placed between components.

The polyethylene meniscal structure measures 6 to 7 mm thick, while the metal phalangeal component has a circular and hollow surface, which receives a peg from the meniscus, and a short stem.

The metatarsal component has a long stem, Kofoed noted.

Patients included in the study were 50 years old, on average, and were operated on between 1999 and 2003, he said. During the procedure, Kofoed used a dorsomedial approach. He also avoided cuts to the short flexor tendon.

Preserving the short flexor tendon

“The most important step in the operation is to conserve the short flexor,” Kofoed said. “This is the most important joint stabilizer, and you must spare it at all times.”

Kofoed also wrapped patients’ great toe in a soft bandage postoperatively and prescribed full weight-bearing walking and tip toe exercises.

Researchers took preoperative radiographs and tracked patients' progress yearly with the images and AOFAS scores. Although patients showed a significant increase in scores at the latest follow-up, Kofoed cautioned that the procedure is not indicated for all MTP-1 arthrosis patients.

“It should only be used in well-aligned of arthrosis of grade 2 and 3, and always as a three component device,” he said.

For more information:
Kofoed H. Total joint replacement for MTP-1 arthrosis. Presented at the American Orthopaedic Foot and Ankle Society 21st Annual Summer Meeting. July 14-17, 2005. Boston.