A cementless, elastic press-fit socket with and without screws

Abstract

Background The acetabular component has remained the weakest link in hip arthroplasty regarding achievement of long-term survival. Primary fixation is a prerequisite for long-term performance. For this reason, we investigated the stability of a unique cementless titanium-coated elastic monoblock socket and the influence of supplementary screw fixation.

Patient and methods During 2006–2008, we performed a randomized controlled trial on 37 patients (mean age 63 years (SD 7), 22 females) in whom we implanted a cementless press-fit socket. The socket was implanted with additional screw fixation (group A, n = 19) and without additional screw fixation (group B, n = 18). Using radiostereometric analysis with a 2-year follow-up, we determined the stability of the socket. Clinically relevant migration was defined as > 1 mm translation and > 2º rotation. Clinical scores were determined.

Results The sockets without screw fixation showed a statistically significantly higher proximal translation compared to the socket with additional screw fixation. However, this higher migration was below the clinically relevant threshold. The numbers of migratory sockets were not significantly different between groups. After the 2-year follow-up, there were no clinically relevant differences between groups A and B regarding the clinical scores. 1 patient dropped out of the study. In the others, no sockets were revised.

Interpretation We found that additional screw fixation is not necessary to achieve stability of the cementless press-fit elastic RM socket. We saw no postoperative benefit or clinical effect of additional screw fixation.

The study protocol and further information concerning this study is available through the corresponding author, DP.

DP: primary investigator, study design, data analysis, and manuscript preparation. JL: RSA analysis, statistical analysis, and manuscript preparation. GvH and MS: senior surgeons, manuscript preparation.

We thank Dr Petra Heesterbeek of the Department of Research, Development and Education at the Sint Maartenskliniek for statistical advice and assistance in preparation of the the final manuscript. We also thank Patricia G. Anderson of the Department of Research, Development and Education at the Sint Maartenskliniek for English editing.

This study was funded by Mathys orthopaedics, Bettlach Ltd, Switzerland, and prior to this study there were no limitations described by either party, on publishing the data resulting from this scientific study.