201. IS THERE A PLACE FOR THE SANDWICH CUP IN ALUMINA-ON ALUMINA ARTHROPLASTY? 53 CASES WITH MEAN SEVEN YEARS FOLLOW-UP

Abstract

Purpose of the study: The Al/PE sandwich is a relatively new massive alumina insert for alumina-on-alumina prostheses using a meta-back press-fit cup. Theoretically, the advantages are a less rigid system and easier positioning and removal. The reliability is however still debated. The purpose of this study was to evaluate the 7-year outcomes of a homogenous series of 53 Al/Al sandwich total hip arthroplasties (THA) implanted without cement.

Material and methods: The series included 48 consecutive patients (53 hips) implanted by the same surgeon from 1998 to 2004 using the posterolateral approach. There were 26 men and 22 women, mean age 58 years (42–69). The prosthesis used a metal back cup totally coated with HA, an Al/PE sandwich insert, a modular anatomic femoral head with partial HA coating, and an alumina head (28 mm). All patients were reviewed and assessed clinically using the Harris score (/100) and the PMA score (/18) and radiographically using the Engh and Gruen and Amstutz scores.

Results: None of the patients were lost to follow-up and none died. One patient underwent revision surgery at 84 months for fracture of the alumina insert: the sandwich insert and the head were changed, and the outcome was very good at three years. At mean 84 months follow-up (47–109), the PMA and Harris scores were, on average, 17.7 and 98 (versus 12.3 and 54 preoperatively, p< 0.05). None of the patients complained of squeaking. There was no acetabular migration or lucency and no osteolysis. A partial and isolated lucent line was observe in the Gruen and Amstutz zone 1 and 8 of the femur in 26% of the hips. Calcar atrophy was noted in 17%. Wear was note radiographically measurable.

Discussion: The clinical and radiographic results appear to be very encouraging at mid term, illustrating the excellent resistance to wear of the alumina-on-alumina bearing, particularly in young and active subjects. With the type of implant used, the improvements provided by the anchorage of the alumina insert in the PE and the increased thickness (minimal 4.5 mm), the high rate of insert fracture reported by certain series in the literature was not observed here.

Conclusion: The absence of wear and osteolysis, improved implant design, and potential advantages in terms of positioning should make this system an attractive alternative for alumina-on-alumina implants.