title: Migration of press-fit cups fixed with poly-L-lactic acid or titanium screws: a randomized study using radiostereometry.
abstract: The early migration of porous acetabular cups was studied in 43 patients with osteoarthrosis. The patients were randomly allocated to additional fixation of the cup with either biodegradable poly-L-lactic acid screws or titanium screws. Radiostereometric evaluation was done during the first 2 years after the procedure in 43 hips (23 with poly-L-lactic acid screws and 20 with titanium screws). At the 2-year follow-up, cups fixed with poly-L-lactic acid screws had migrated significantly more in the proximal-distal (p < 0.05) and medial-lateral (p < 0.05) directions. Cups with titanium screws displayed more pronounced rotations around the longitudinal axis (p < 0.05). Postoperatively, on the lateral view, there was an increased occurrence of radiolucencies at the dome of the cups fixed with poly-L-lactic acid screws (p < 0.05). The clinical result did not differ between the two groups. Inferior implant-bone contact in the poly-L-lactic acid group, local changes of the bone quality, and diminishing support of the poly-L-lactic acid screws caused by their degradation with time could be reasons for the different pattern of migration observed.
authors.affiliation: Department of Orthopaedics, Sahlgrenska University Hospital, Göteborg, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Thanner
authors.forename: J
authors.initials: J
authors.lastname: Kärrholm
authors.forename: H
authors.initials: H
authors.lastname: Malchau
authors.forename: L
authors.initials: L
authors.lastname: Wallinder
authors.forename: P
authors.initials: P
authors.lastname: Herberts
mesh_terms: D000077:Acetabulum; D000368:Aged; D001175:Arthrography; D001863:Bone Screws; D004867:Equipment Design; D005260:Female; D005548:Foreign-Body Migration / Q000175:diagnosis* / Q000000981:diagnostic imaging; D006801:Humans; D007720:Knee Prosthesis; D019344:Lactic Acid; D008297:Male; D008875:Middle Aged; D011091:Polyesters; D011108:Polymers; D012399:Rotation; D014025:Titanium
chemical_list: D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide); D014025:Titanium