Original PI left institution and successor has no interest in continuing project.

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.

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.

Inclusion Criteria:

• Individuals must be older than 18 and younger than 75 years of age, both genders.
• Participants must be experiencing symptoms related to their baseline condition for at least six months before the surgery.
• Clinical and radiographical clinical diagnosis of hallux rigidus.
• Hallux Rigidus grade III or grade IV.
• Surgical indication after failure of nonoperative treatment (at least six months).

Exclusion Criteria:

• Previous hallux metatarsophalangeal fusion.
• Less than 20 degrees of complete range of motion on the hallux metatarsophalangeal joint.
• Patient desire or medical indication for a hallux metatarsophalangeal joint arthrodesis.
• Patient desire or medical indication for other surgical modalities.
• History or documented evidence of autoimmune or peripheral vascular diseases.
• History or documented evidence of peripheral neuropathy (nervous compression syndrome, tarsal tunnel syndrome) or systemic inflammatory disease a (rheumatoid arthritis, seronegative, connective, etc.).
• Any condition that represents a contraindication of the proposed therapies.
• Any physical or social limitation that makes the protocol continuation unviable.
• Impossibility or incapacity to sign the informed Consent Form.
• Presence of infectious process (superficial on the skin and cellular tissue, or deep in the bone) in the region to be treated.
• Pregnancy.
• Clinical and imaging diagnosis of untreated osteoporosis.
• Serum vitamin D levels below 20ng/ml.
• Non-palpable anterior or posterior tibial pulse; or abnormal capillary filling.
• Tumor lesions (primary or secondary tumors).