All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 1. Horizontally cemented components: AP better fixated than MB.
BACKGROUND
Controversy still exists as to whether to mount the tibial bearing on a metal baseplate or not. Furthermore, the tibial component can be either horizontally or completely cemented. We evaluated metal backing versus all-polyethylene using horizontal cementing technique.


METHODS
We randomized 40 patients with knee arthrosis (40 knees) to 2 groups: cemented total knee arthroplasty (AGC, Biomet) using either all-polyethylene (AP) or metal-backed (MB) tibial components (n = 20 for each group). All tibial implants had a total thickness of 8 mm. We used proximal cement-ing, including only the horizontal part of the tibia with avoidance of the stem-bone interface.


RESULTS
The positioning of the implants, as judged by the HKA angle, showed an average neutral alignment in both groups. Preoperatively and after 2 years, there was no statistically significant difference between the HSS scores in both groups (p = 0.6 and 0.4). After 2 years, the metal-backed components had rotated more around the longitudinal axis, median 0.5 degrees vs. 0.2 degrees (internal or external rotation, p = 0.002), and showed increased maximum total point motion, median 1.0 vs. 0.4 mm (maximum migration or MTPM, p = 0.003).


CONCLUSIONS
Our study indicates that better fixation can be obtained with the all-polyethylene design if proximally cemented thin components are used.
Department of Orthopaedics, St. Göran's Hospital, SE-112 81 Stockholm, Sweden. hans.hyldahl@stgoran.se
Hans
H
Hyldahl
Lars
L
Regnér
Lars
L
Carlsson
Johan
J
Kärrholm
Lars
L
Weidenhielm
D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods; D001843:Bone Cements; D002484:Cementation; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D007720:Knee Prosthesis; D008297:Male; D008670:Metals; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011095:Polyethylenes; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular; D013977:Tibia; D016896:Treatment Outcome
D001843:Bone Cements; D008670:Metals; D011095:Polyethylenes