Success in Replacing the Metacarpophalangeal Joints and Ulnar Head

Small-bone arthroplasties involving joint implants for finger, wrist, and forearm are often a neglected topic of analyses in the broad orthopedic community, probably because of a historical association with high failure rates.

Over the past decade, innovation has helped change former failure scenarios into success stories. "The progress continues in terms of materials, design, technique, implant technology, and clinical effectiveness for small-bone joint replacements," explains Richard A. Berger, M.D., Ph.D., a hand surgeon at Mayo Clinic in Rochester, Minn. He helped devise Mayo's modular, multistem and multisize prosthesis for ulnar-head replacement (Avanta uHead).

Mayo Clinic hand surgeon Marco Rizzo, M.D., adds, "With current advances, experienced arthroplasty teams can generally vastly improve the quality of life for patients disabled by hand pain and functional impairment from degenerative damage or trauma."

Mayo Clinic Leadership

In 1962, Mayo Clinic hand surgeons pioneered the field of arthroplasty of the small joints of the hand when they first used silicone metacarpophalangeal (MCP) implants in rheumatoid arthritis patients. Mayo continues to lead in both innovation and clinical application of orthopedic discovery to patient care. By doing so, Mayo Clinic hand surgeons continue to offer hope for improved function to patients with advanced arthritic conditions of the hands.

Highlights of Mayo's contribution to the success of small-joint arthroplasty include:

• 1970-present: Development and subsequent refinements to nonconstrained pyrolytic carbon implants for proximal interphalangeal joints (PIP) and MCP joints
• 1970-present: Development and subsequent refinements of metal and plastic surface replacement implants for proximal PIP and MCP joints
• 2001: Development of a metallic ulnar-head implant for patients with unstable forearms secondary to excision of an arthritic ulnar head
• 2007: Development of a metal and plastic sigmoid notch component to match the ulnar-head implant to create an unlinked total joint replacement

Unar-head implant

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X-ray after ulnar-head implant surgery

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Rationale for Ulnar-Head Replacement

The ulnar head is central to forearm biomechanics, stability, and full wrist motion because it is the only fixed, bony, nonmoving support for radial rotation. Rheumatoid arthritis and trauma frequently impair the ulnar head and thus destroy the pain-free proper functioning of the wrist and diminish hand grip strength in older adults. In the past 10 years, advances in implants and technique have shown ulnar-head arthroplasty to be reliable, effective primary treatment when performed at centers of orthopedic excellence.

Replacement of the distal ulnar head may be indicated when nonoperative treatment of the wrist joint does not resolve pain, weakness, and instability, and diagnostic imaging confirms damage to the distal radioulnar joint. Additionally, evidence of failed ulnar-head resection or failed arthroplasty may indicate the need for a salvage procedure. In the presence of these indications, the patient must also have adequate bone health and soft tissue to allow for osseous integration of the implant and tissue stabilization.

MCP Joints

Favorable results can be obtained with the newest generation of implants, nonconstrained pyrolytic carbon arthroplasty for MCP joint arthritis. As evidence, Dr. Rizzo cites a published Mayo Clinic team review of 142 arthroplasties (61 patients), in which 130 were primary joint replacements and 12 were revisions of prior silicone treatments.

Before and after implants

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The data showed improvements in arc of motion, oppositional pinch, and grip strength. Notes Dr. Rizzo, "Preliminary results suggest that pyrolytic carbon MCP joint arthroplasty provides good pain relief, patient satisfaction, and functional improvement in managing osteoarthritis and select cases of rheumatoid arthritis." He adds that longer follow-up evaluation will help validate these promising early results.

Expertise Creates Options

The biggest challenge now is defining the best candidates for these implants. Because of the laxity of soft tissue in severe rheumatoid arthritis patients, stability is more difficult to achieve with unconstrained implants.

Notes Dr. Rizzo, "Although the implant has worked well in selected patients with rheumatoid arthritis, those who have extensive disease, deformity, or dislocation may do better with the silicone as a fallback option. But each case is unique. It's important for patients to go to an advanced orthopedic center that can deploy all available options with equal expertise."

Mayo Clinic and Dr. Berger receive royalties related to development of some of the technologies mentioned in this article.