This study was to evaluate results after conversion of fused hip to total hip replacement arthroplasty and to correlate factors that affect the results.

Twenty-five hips in twenty-three patients who underwent THRA for bony ankylosis of hip from January 1983 to July 1996 were reviewed.

Of 19 cases who had adjacent joint pain, 13 cases improved clinically. The average Harris Hip Score improved from 74 points preoperatively to 86 points postoperatively, and HSS seemed to have no relationship with the causes and duration of ankylosis or presence of previous operation. Radiologically, three of femoral components that had been inserted without cement were loose. The socket was loose in all 6 cases using PM type prosthesis. Within 19 cases that porous coated hemispheric prosthesis were inserted, the socket was loose in 2 cases. The acetabular socket of PM type showed much higher incidence of aseptic loosening ( p< 0.01 ).

THRA in fused hip improved the quality of life by restoring joint motion and relieving pain in adjacent joint affected secondarily to fused hip. However, threaded type cup showed high rate of failure due to lack of biologic fixation.