FOUR-YEAR FOLLOW-UP OF A TANTALUM, MONOBLOCK ACETABULAR COMPONENT

Abstract

Osteolysis secondary to polyethylene wear is the most serious aseptic long-term complication following THR. Studies have shown that fixation with screws, modularity and lack of extensive bone ingrowth are associated with increased osteolysis. This study examines the initial experience with a cup designed to address these issues.

One hundred and twenty-seven consecutive primary THR were performed between 1997–1999 using unce-mented monoblock, elliptical, tantalum cup without screw holes. Average follow-up 40 months (range 24 to 61). 79 THR in females, 48 in males. 48% THR hybrid fixed, 52% uncemented. Average age 61.6 years (range 19 to 88). Pre and post-operative clinical assessment with Harris hip score (hhs), WOMAC, SF-36. One independent, blinded observer performed zonal radiographic analysis with modified DeLee and Charnley method.

Average hhs at recent follow-up 93 (range 85 to 100). All shells appear fixed with bone ingrowth. Dome-gaps present in 6 cups post-op; all have filled in. Radiolucencies at follow-up: 4% zone 1, 8% zone 2; none greater than 1 mm. No cup migration. 8 cup related complications: 5 dislocations (4%) 1 subluxation, 2 undisplaced rim fractures (1.7% – no treatment). 3 dislocations, 1 subluxation occurred more than three months post-op. 3 revisions: 1 deep wound infection, 1 liner exchange (using reaming technique), 1 femoral head exchange.

Uncemented monoblock, elliptical tantalum cup without holes provides secure, symptom-free fixation at 4 years. No complications associated with use of tantalum. Elliptical shape associated with dome gaps, all of which appeared to fill by 3 months. Monoblock design results in increased polyethylene lip prominence associated with 6 cases of instability. Effect of prominent rim on impingement and long-term wear requires careful follow-up.