A Closer Look At A New Nitinol Hammertoe Implant

A new nitinol fixation device can provide multi-axial active stabilization for hammertoe arthrodesis without requiring surgeons to freeze the device before use.

The HammerLock 2 is a shape memory hammertoe implant that can fit into narrower proximal canals and has conforming and compressive fixation, according to the manufacturer BME. The company notes that the implant has a spear-like proximal segment with multi-axial conforming arms that can promote secure fixation.

Mary Crawford, DPM, FACFAS, has been using the HammerLock 2 since November and usually uses the 10 degree angulated implant. In comparison to the original Hammerlock, she says not having to keep the device in the freezer is an advantage as the freezer is not conveniently located near the operating rooms at her hospital. In addition, Dr. Crawford says the HammerLock 2 has more variations in length for the proximal phalanx segment and is more secure within the phalanx due to its multi-axial design. She also notes it is easier to insert and the insertion handle detaches easily once the implant is in place.

“I find the system very easy to use and all the equipment required for implantation, including all the drills and broaches, is conveniently packaged,” says Dr. Crawford, a Fellow and Past President of the American College of Foot and Ankle Surgeons. “They are all clearly numbered so the steps taken to properly insert the implant are easy to follow. The equipment seems simpler to use than the first-generation HammerLock device.”

Other advantages for the HammerLock 2 are that is pre-sterilized, fully disposable, does not require forceps and does not require manual compression after implantation, according to BME.
Dr. Crawford has seen good results so far with the Hammerlock 2 implant.

“In the initial post-op phase of care, the digits are definitely less swollen (with the HammerLock 2 implant) than with standard K-wire fixation. The digits are therefore less painful due to less swelling and less aberrant motion in comparison to K-wire fixation of an arthrodesis or arthroplasty,” notes Dr. Crawford, who is in private practice at Ankle and Foot Clinics in Everett, WA. “Long-term, the implants do well and have very predictable results with the intrafragmentary compression leading to proper fusion of the arthrodesis of the proximal interphalangeal joint.”

Dr. Crawford says the digits are well aligned in both the sagittal plane and transverse plane alignment, and adds that she has not had to remove any of the implants.

Contraindications to using the HammerLock 2 would include severe osteopenia or a metal allergy to nickel, according to Dr. Crawford. She has not experienced any complications to date.

She notes one possible disadvantage to the HammerLock 2 is there is no cannulation of the implant to allow for pin fixation across the lesser metatarsophalangeal joint (MPJ) if necessary due to flexor transfer or MPJ contracture release. However, Dr. Crawford has resolved this disadvantage by pinning from the plantar base of the digit into the metatarsal head and has talked to colleagues who have resolved this by pinning from the dorsal metatarsal into the base of the digit.