Comparison of NeuFlex and Swanson Metacarpophalangeal Implants for Rheumatoid Arthritis

NeuFlex and Swanson Metacarpophalangeal Implants for Rheumatoid Arthritis: a Prospective Randomized Controlled Clinical Trial

The main hypotheses for this study are as follows:

1. The use of NeuFlex implant results in flexion in the fourth and fifth MP joints that is at least 10 degrees greater than with teh use of the Swanson implant.
2. The use of the NeuFlex implant is associated with a significantly (2.5 kg or more) greater grip strength than with the use of the Swanson implant.

Many studies have evaluated metacarpophalangeal joint (MP) range of motion following Swanson arthroplasty. These studies report that overall MP flexion is restricted postoperatively. They do not usually report individual range of motion values for each digit. Therefore one cannot identify if the degree of MP flexion restriction differs by digit.

We, and others, have observed that MP flexion is particularly restricted in the ring and litter finger following Swanson arthroplasty.

There is a new implant (NeuFlex), which instead of being introduced in full extension, like the Swanson implant, has a resting position of 30 degrees of flexion. As MP flexion is particularly restricted in the ring and little finger, an implant that by design encourages flexion may be helpful. A need exists to establish if the use of the NeuFlex implant produces greater MP flexion in the ring and little finger where restricted flexion has been identified as a problem.

Inclusion Criteria:

• rheumatoid arthritis
• primary metacarpophalangeal arthroplasty of all 4 digits

Exclusion Criteria:

• diagnosis of other connective tissue disorder (e.g. SLE, MCTD)
• previous surgery of MP joints
• revision metacarpophalangeal arthroplasty