A Closer Look At The Corrective Potential Of Ultrasonic Bone Welding

This author notes ultrasonic bone welding was beneficial for a 57-year-old patient with crossover hammertoe deformity and a plantar plate tear with metatarsophalangeal joint subluxation

A 57-year-old female presented with progressing pain and deformity at her left second digit with associated metatarsalgia. A weightbearing X-ray (see left photo) revealed dorsal and medial subluxation of the second digit at the metatarsophalangeal joint (MPJ) and hammertoe, which correlated with the clinical exam (see right photo).

After the failure of conservative care attempts that included accommodative extra depth shoes, I performed surgical reconstruction. The procedures included proximal interphalangeal joint (PIPJ) arthrodesis with an implant (Smart Toe, Stryker); a Weil metatarsal osteotomy with a medial shift of the capital fragment fixated with one ultrasonic bioresorbable polymer pin (SonicAnchor, Stryker); and a plantar plate primary repair (2-0 Force Fiber, Stryker).¹

With successful surgical reduction, the patient was able to return to full weightbearing in a sneaker by the third post-op week and continues to be pain-free with no return of the deformity more than six months after the procedure (see below photos).

Comparing Current Fixation Techniques With Ultrasonic Welding

It is my opinion that current conventional fixation techniques of a single or multiple screws for the Weil osteotomy represent a compromise.¹ For ideal angled fixation not to invade the metatarsal head to the plantar plate interface, one needs to ensure fixation into the cancellous bone. However, it is difficult to achieve stability with small snap-off or cannulated screws that are best designed for bicortical stabilization.

In addition, when utilizing small pin or screw fixation of this metatarsal osteotomy, it is difficult to ensure that there will be no undesired rotation of the capital fragment post-reduction without utilizing multiple screws that would subsequently increase the complication risk with retained hardware.

One can eliminate the limitations of the current popular metatarsal decompression osteotomy fixation with the use of a resorbable polylactide polymer that surgeons can insert with ultrasonic welding techniques. Ultrasound-induced liquefaction allows this completely resorbable material to penetrate the porous structures of the bone with a quick (approximately five seconds) return to a solid state in a three-dimensional fixation that resists not only separation but rotation of the osteotomy as well. Insertion of a single pin can provide a three-dimensional primary stability in this cancellous and cortical bone.

Furthermore, the long absorptive profile of the polymer minimizes the cystic changes and foreign body reactions that continue to plague other popular absorbable fixation systems.

Dr. Rocchio is in private practice at PA Foot and Ankle Associates in Allentown, Pennsylvania. He is a Fellow of the American College of Foot and Ankle Surgeons.

Reference

1.      Sorenson MD, Weil L Jr. Lesser metatarsal osteotomy. Clin Podiatr Med Surg. 2015;32(3):275-290.