[Early weight bearing after uncemented total hip prostheses--an analysis of acetabulum cup migration].
OBJECTIVE
The postoperative mobilisation after cementless total hip arthroplasty is usually non-weight bearing within the first six weeks to achieve bony ingrowth for the implant. Since 1995 weight bearing mobilisation is performed at our clinic even after cementless implantation of the Alloclassic (Zweymüller-Sulzer) system. The aim of the presented study was the detection of any negative influence of weight bearing mobilisation on the stability of this cementless implant.


METHODS
The horizontal and vertical cup migration of 42 cementless acetabular cups (Alloclassic Zweymüller-Sulzer) in 40 patients after weight bearing mobilisation and a minimum follow up of 24 months were analysed by a digital migration analysis. The results were compared to a normative migration profile of the same that was recently established.


RESULTS
The migration analysis did not exceed the level of accuracy of 1.3 mm in any patient. The mean horizontal cup migration was 0.3 mm in both groups after 24 months, the mean vertical migration was 0.4 mm in both groups. No significant difference of the acetabular stability was detectable. None of the implants showed radiological signs of loosening or migration.


CONCLUSIONS
The presented data justify an early postoperative weight bearing mobilisation using the cementless Alloclassic threated cup, provided that primary stability of the implant can be achieved.
Dominkus
M
M
Universitätsklinik für Orthopädie und Forschungslabor, Univ.-Klinik für Orthopädie, Allgemeines Krankenhaus der Stadt Wien, Osterreich.
Funovics
P
P
Schwameis
E
E
D000077:Acetabulum; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000534:rehabilitation*; D004434:Early Ambulation; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D016896:Treatment Outcome; D016474:Weight-Bearing / Q000502:physiology*