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


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.


CONCLUSIONS
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.
Department Orthopaedic and Trauma Surgery, Orthopaedic Centre OCON, Hengelo, the Netherlands. dfm.pakvis@gmail.com
Dean
D
Pakvis
Joan
J
Luites
Gijs
G
van Hellemondt
Maarten
M
Spruit
D000077:Acetabulum / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip; D001843:Bone Cements; D001863:Bone Screws; D020099:Coated Materials, Biocompatible; D005260:Female; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D059869:Radiostereometric Analysis; D014025:Titanium
D001843:Bone Cements; D020099:Coated Materials, Biocompatible; D014025:Titanium