抄録
Since 1980 we have developed a surface replacement type of elbow prosthesis composed of a humeral mold (policrystalline alumina) and an HDP ulnar component with a ceramic peg. No cement has been used for prosthetic fixation. All patients operated on were suffering from definite or classical rheumatoid arthritis. By 1985 this ceramic prosthesis had been used on 21 elbows in 21 rheumatoid patients. Taking into account clinical evaluation over the 3 years, the design of the humeral mold was then changed into a stemmed prosthesis mainly due to the loosening on the mold (17%) that occurred with the original. From 1986 a humeral mold with a sapphire stem (10 cm in length) has been used for 5 elbows in 5 rheumatoid patients, using bone cement in 2 of them. In our operative procedure, the posterior approach described by W.A. Souter has been commonly used, but special instruments for correct cutting of the bone and setting of the prosthesis were developed by us.
In the clinical evalution, R.B. Brigham Hospital's scoring system was applied for the assessment of the original surface replacement type of prosthesis; an arerage score of 29.6 preoperatively had improved to 77 at an average of 66 months postoperatively. However, the Mayo Clinic's scoring system was introduced for the evaluation of the stemmed prosthesis replacement; the score was 51.2 preoperatively and 86, 8 postoperatively (using the R.B. Brigham Hospital's scoring system, 29.0 preoperatively and 83, 0 postoperatively were obtained in the same patients) . With respect to clinical evaluation, the pain and functional scores are given so much weight in the Brigham Hospital's scoring system that the score seemed to show too much improvement. Therefore we decided that the Mayo Clinic's scoring system was better for assessing the exact condition of the elbow function.
Postoperative complications such as instability and prosthetic loosening seemed to be decreased after the design chanage to a stemmed prosthesis and instrument developments though the follow-up time is still short.
