Background: In 80% of patients with rheumatoid arthritis the metacarpophalangeal (MP) joints are involved with increasing destruction and loss of function. Silicone arhtroplasties of the MP joints produce a limited range of motion, increasing osteolysis and fractures of the implants. The cementless, unconstrained design of the ElogenicsTM prosthesis is a new concept for treating the MP joints of rheumatoid patients.

Methods: In a prospective study 72 ElogenicsTM prosthesis were implanted, 62 in patients with rheumatoid arthritis, osteoarthritis (n=4), polyarthritis (n=5) and 1 after revision of a silicone implant. The patients were reexamined after an average follow up of 21 months (12–51 months) clinically and radiologically.

Results: The average active range of motion for extension to flexion increased from 0/18/65° before surgery to 0/14/71° after surgery. The remaining ulnar drift was 12° (preoperative 18°!). Pain in the visual analogue scale improved from 2.3 to 1.7 postoperatively. Eight palmar luxations of the implants were recognized. They were revised and are stable during the follow-up. No infection occurred. Two prostheses were changed because of loosening. The X-rays showed osteointegration in the metacarpal components. Radiolucent zones were found in progress at the basis on the palangeal components.

Conclusion: The short- and midterm results after implantation of the cementless, unconstrained ElogenicsTM prosthesis show an improved hand function and pain relief. The design of the implant may solve the accepted postoperative problem of instability of the MP joints.

In 85 % of the patients with rheumatoid arthritis the MCP-joints are involved with incressing deterioration an loss of function. The standard replacement of the MCP-joints using the Swanson-Silastic Spacers shows pain reduction and a realigment of the fingers, but the functional capacity is not improved.

The HM-MCP-arthroplasty offers a concept for better function an restoration of the rheumatoid hands and osteoarthritis.

In a prospective multicenter study 63 HM-MCP arthroplasties have been implanted. We used the redesigned model (PE-metacarpal head and Ti-ODH phalangeal base) with titanium stems. The follow up-time is 18 months (6 – 40 months). All patients are controlled with clinical and radiographic evaluation.

The active ROM of the MCP-joints demonstrated on average flex./ext. 65/10/0 (preop. 70/15/0). The grip strength at FU demonstrated 80 % of the untreated contralateral control hand. Pain has been improved using the verbal pain scale at 1.6 (preop. 2.1).

Radiographically all metacarpal and phalangeal stems show an osteointegration of the implants. Radio-lucent lines of < 1 mm have been detected at the phalangeal base without a sign of loosing.

Complications: 1 palmar luxation with a successful closed reposition, 1 ulnar subluxation of the fifth finger, 1 unsuccessful revised palmar luxation.

The results of the uncemented, unconstrained HM-MCP-arthroplasty show an improvement of the hand function and pain reduction. This endoprosthesis gives a new chance to treat the rheumatoid hand at an earlier stage of destruction before severe contracture of the soft tissues.