Proposed digital arthroplasty critical study of the preliminary results

In view of the results of Swanson implants, particularly the long-term course of silicone implants, the authors studied and developed semi-constrained sliding arthroplasty designed for metacarpo-phalangeal and proximal interphalangeal joints. The preliminary study on bones and then on cadaver hands and finally on the knee of the rabbit allowed the design and experimentation of a prototype which led to the creation of a semi-constrained arthroplasty for which the elastic diaphyseal anchoring is ensured without cement and which possesses sliding surfaces composed of a metallic (proximal piece)--polyethylene (distal piece) interface. We therefore describe the principles of functioning of this arthroplasty, its technique of insertion, dorsal trans-tendon incision, its accessory (drill for diaphyseal preparations), its anatomical requirements (preservation of the palmar plate and lateral ligaments, bone section) and the postoperative course. To date, 52 arthroplasties have been inserted and we present the results of the first 36 cases for which the follow-up is equal to or a greater than one year (20 MP-16 PIP), indicating the technical modalities according to the various aetiologies (21 cases of rheumatoid arthritis--15 post-traumatic cases) and the complications. The average gain in mobility is 40 degrees with a mean range of movement of 64 degrees. In terms of pain, none of the arthroplasties were associated with pain apart from pain on cold in certain post-traumatic cases. The global and thumb-finger prehensile forces were evaluated to be an average of 90% in relation to the healthy side. Radiological assessment demonstrated fixation of the pieces in every case. Lastly, we discuss the outcome of this arthroplasty and its current indications in relation to the problems of instability essentially occurring in dislocated MP joints of rheumatoid arthritis.