Metatarsophalangeal HAPY® spherical pyrocarbon implant: Technical note

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Podiatric medicine

Background:

• The first metatarsophalangeal joint (MTP1) is crucial for foot function.
• Degenerative conditions of the MTP1 joint often lead to pain and limited mobility.
• Current arthroplasty options may involve bone resection or fusion, potentially sacrificing joint function.

Purpose of the Study:

• To introduce a new arthroplasty concept for the MTP1 joint using a pyrocarbon interposition implant.
• To describe the surgical technique for implanting the HAPY® spherical interposition implant.
• To evaluate the preliminary clinical outcomes and radiographic findings of this novel MTP1 arthroplasty.

Main Methods:

• A spherical pyrocarbon interposition implant (HAPY®) was used, designed for gliding on bone/cartilage without bone integration.
• A surgical technique involving hollowing a spherical cavity in the metatarsal head to stabilize the implant was employed.
• A preliminary study assessed 22 patients with a mean follow-up of 36 months, evaluating AOFAS scores and radiographic changes.

Main Results:

• The mean AOFAS score significantly improved from 64 preoperatively to 91 postoperatively (p<0.05).
• No instances of subchondral cyst formation or osteolysis were observed at the final assessment.
• The implant functions via gliding, aiming to maintain MTP1 joint mobility and function.

Conclusions:

• The HAPY® pyrocarbon interposition implant represents a promising arthroplasty option for the MTP1 joint.
• This technique may effectively improve patient function and reduce pain without causing adverse bone reactions.
• Further long-term studies are warranted to confirm the durability and efficacy of this implant concept.