A554. THE POROUS TANTALUM MONOBLOC ACETABULUM – RESULTS TO 10 YEARS

Abstract

A monobloc porous tantalum acetabular cup with a 28mm internal diameter was employed in 397 primary total hip replacements between August 1997 and December 2003. All patients were personally examined at yearly intervals for 3 years following surgery and at 2 year intervals thereafter. Thirty-one patients were known to have died and 69 hips were lost to follow up less than three years following implantation, leaving 297 hips (81%) available for review up to 10 years following implantation.

The mean age at surgery was 66.2 years, with 12% of patients aged 80 years or older. 58% of the patients were female and 42% male. 82% of the patients had osteoarthritis. Clinical and radiographic data were analyzed for patients followed for a minimum of 3 years. Mean follow up was 5.4 years. The mean preoperative Harris hip score was 31, increasing to 89 at last follow up.

The most common complication was dislocation. Eleven patients had dislocations in the early postoperative period: 4 required closed and 2 open reduction, and five required revision of the acetabular component for recurrent instability. Three patients (4 hips) with severe rheumatoid arthritis developed late instability and required acetabular revision. Four patients had a femoral fracture, 2 of which healed with slight settling and 1 of which required open reduction, subsequently became infected and required removal of the prosthesis. There was 1 superficial and 2 additional deep infections, one of which required component removal. Two patients had a fracture of the greater trochanter and required internal fixation. Four femoral components loosened, of which 3 were revised, all without involvement of the acetabular component.

There were 3 transient sciatic nerve palsies; one resolved completely and two partially, although all 3 were lost to follow before 3 years.

The porous tantalum monobloc acetabular components performed remarkably well at up to ten years following implantation. There were no instances of clinical or radiographic loosening, no osteolysis and no measurable wear visible on postoperative radiographs. The highly porous tantalum achieved reliable bony ingrowth in all cases. We hypothesize that the direct compression molding of the polyethylene into the porous tantalum substrate eliminated the backside wear and the flexion of the polyethylene liner that occurs in modular cups.