Synthetic Cartilage Implant Versus Interposition Arthroplasty in Hallux Rigidus Treatment: A Randomized Clinical Trial

A minimum of 100 patients with grade III hallux rigidus will be randomized in two parallel groups for surgical care. The first group will be submitted to the insertion of a synthetic cartilage implant at the metatarsophalangeal (MTP) joint. The second group will receive a dermal interposition arthroplasty at the MTP. Both sides will undergo the same post-operative protocol. Pain, complications, and functional results will be evaluated in a minimal of two years of follow-up.

The synthetic implant begins by performing and dorsal midline approach, from the proximal phalanx diaphysis to the first metatarsal neck. Dissection is carried avoiding injury to the dorsal cutaneous nerves and the extensor hallucis longus tendon. The capsule is open longitudinally, osteophytes removed, and a guidewire inserted through the center of the first metatarsal head. The position of the metallic wire is checked and the tunnel for the implant is drilled. The synthetic cartilage implant (Cartiva™, Stryker Medical®) is introduced through the tunnel, leaving it proud with the head surface by 2mm. The capsule is closed, followed by the other planes and the skin. The patient is banded and placed in a postoperative hard sole shoe for six weeks. Range of motion is encouraged from the third week and the shoe is discontinued after the sixth week. Return to sports activities and normal shoewear occurs by twelve weeks.

The interposition arthroplasty initiates with the same dorsal midline approach, from the proximal phalanx diaphysis to the first metatarsal neck. Dissection is carried avoiding injury to the dorsal cutaneous nerves and the extensor hallucis longus tendon. The capsule is open longitudinally and osteophytes are removed. A guidewire inserted through the center of the first metatarsal head and the center of the proximal phalanx for proper surface preparation. Convex-concaves anatomical drills are used, removing remaining cartilage and opening space for the graft. A decellularized dermal allograft (Arthroflex™, Arthrex®) is placed at the joint and sutured to the head, maintaining the epidermal surface in contact with the phalanx. The graft is trimmed, the capsule is closed, which is followed by the other planes and the skin. The patient is banded and placed in a postoperative hard sole shoe for six weeks. Range of motion is encouraged from the third week and the shoe is discontinued after the sixth week. Return to sports activities and normal shoewear occurs by twelve weeks.

The WBCT is the standard of care for the preoperative and postoperative assessment of patients with hallux rigidus. Some of the complications will also be evaluated through WBCT. No extra WBCT will be performed other than what we normally do for patients.

Randomization will be performed previously at the beginning of the study and will be performed by an outside researcher. Allocation will happen during surgery scheduling.