MIDDLE-TERM RESULTS OF ANATOMIC MEDULLARY LOCKING TOTAL HIP-ARTHROPLASTY

We report the results of cementless, anatomic, medullary locking hip p rosthesis application in our first consecutive series, We used the so- called Asian size of prosthesis with proportionally smaller stem sizes in both diameter and length. Forty-seven stems and sockets were analy zed with a mean follow-up of 69 months, The mean Merle d'Aubigne hip s cores were 8 points preoperatively and 16 points at the final follow-u p. Radiologically, the stems showed excellent stability without loosen ing, Stress shielding around the stems did occur in most cases but did not progress. Preoperative bone duality influenced the extent of stre ss shielding evaluated at the final follow-up: higher stress shielding was noted in poorer quality bones at the time of operation. There wer e problems with the sockets. The shallow socket and impingement at the protruded rim seemed to cause a high incidence of dislocation (13%). Massive polyethylene wear occurred in 5 sockets. These sockets were 48 and 46 mm in diameter with 26 mm heads. In conclusion, the stems of t he anatomic medullary locking hip prostheses used in Japan showed sati sfactory stability even in poor quality bones, but there were problems with the polyethylene liners. Our solution was to use larger sockets with 22 mm heads.