Periapatite may not improve micromotion of knee prostheses in rheumatoid arthritis.

UNLABELLED: Prosthesis migration in bone inevitably occurs in cemented and uncemented total knee arthroplasty tibial components. Cemented designs as the gold standard give immediate fixation whereas cementless designs need a period of bone ingrowth onto the surface irregularities of the implants. The addition of bioactive coatings may enhance this process of ingrowth. A controlled randomized prospective RSA study was carried out on 26 Duracon implants in a rheumatoid arthritis patient group to evaluate the effect of a periapatite coating on the fixation of the tibial tray. The coated and the noncoated groups were matched for sex, age, body mass index, and HSS Knee Score. Stage of preoperative joint destruction and preoperative and postoperative mechanical leg axis showed no differences. We saw no differences in migration between the two groups, but a trend for lesser translations along and rotations about all three axes in the periapatite group. The periapatite-coated components showed a lower variance in subsidence than did the uncoated components. Both groups also showed a high variance in anterior tilting of the components. The cementless PA-coated Duracon prosthesis used in patients with RA may provide improved fixation of tibial components although we could not demonstrate improvement in this small controlled series. LEVEL OF EVIDENCE: Therapeutic Level II. See the Guidelines for Authors for a complete description of levels of evidence.

Souter-Strathclyde total elbow arthroplasty: medium-term results.

The Souter-Strathclyde unconstrained elbow prosthesis was prospectively studied in 36 patients (45 prostheses) with rheumatoid arthritis (Larsen grade 4 and grade 5). The mean age of the patients at the time of operation was 63 years (range: 39 to 75 years). Eight patients (9 prostheses) died within five years of implantation, from causes unrelated to the elbow arthroplasty. One patient was lost to follow-up, leaving 27 patients (35 prostheses) for review. The mean length of follow-up was 98 months (range: 60 to 174 months). At 8.2 years follow-up, the prosthesis showed a probability of survival of 76% (SD 9%) with revision of the humeral component as an end point; the percentage dropped to 67% (SD 9%) when radiographic loosening was taken as an end-point. Survival of the ulnar component was 98%. Loosening of the humeral component seems to be related to both the short humeral stem and a persistent extension deficit.