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Comparative Study
. 2014 Apr;38(4):725-31.
doi: 10.1007/s00264-013-2187-8. Epub 2013 Nov 22.

Effect of design on the initial stability of press-fit cups in the presence of acetabular rim defects: experimental evaluation of the effect of adding circumferential fins

Wolfgang O Huber  1 , Philip C Noble
Affiliations
Comparative Study

Effect of design on the initial stability of press-fit cups in the presence of acetabular rim defects: experimental evaluation of the effect of adding circumferential fins

Wolfgang O Huber et al. Int Orthop. 2014 Apr.

Abstract

Purpose: This experimental study was undertaken to examine the fixation characteristics of a six-finned acetabular cup in both primary and revision arthroplasty in comparison with two other commonly used cup designs without fins.

Methods: All three cup designs (Ananova® [Intraplant], Plasmacup® NSC [Aesculap]; Exceed ABT™ [Biomet]) were implanted into validated models of normal and revision acetabula. The defect models were designed to simulate a dorso-cranial rim defect of 90° width and 10 mm in depth (moderate rim defect) and a dorso-cranial rim defect of 130° width and 15 mm in depth (severe rim defect). The fixation strength of the three cup designs was tested by cyclically edge-loading the implanted cups using a mechanical testing machine.

Results: The six-finned Ananova implant exhibited greater resistance to foam-cup interface motion than both the Plasmacup and Exceed ABT implants. The largest average differences were observed in the resistance to ultimate spin-out, with Ananova outperforming Exceed ABT and Plasmacup by 26% and 17% in the moderate and by 36% and 38% in the severe defect models, respectively.

Conclusions: The six-finned Ananova cup was significantly more resistant to edge loading both in the normal acetabulum and in acetabula with moderate to severe dorso-cranial rim defects than cup designs without fins, indicating that it may cover a wider range of clinical indications than conventional press-fit cups and provide clinicians with the confidence that, in primary and simple revision arthroplasty, adequate fixation strength can be obtained.

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Figures

Fig. 1
Fig. 1
Ananova (a), Plasmacup (b), and Exceed ABT (c) acetabular cups, including dimensions (in mm) used in this study
Fig. 2
Fig. 2
Photographs of the final surrogate acetabulum design
Fig. 3
Fig. 3
Dorso-cranial rim defect illustration in a cross section through the CAD model of the surrogate design. a Moderate defect model with 90° defect in the ischial area. b Severe defect model with 130° defect across the ischial and iliac zones
Fig. 4
Fig. 4
Edge-loading set-up using a mechanical testing machine
Fig. 5
Fig. 5
Ultimate spin-out results of the three cup designs in the normal, moderate rim defect, and severe rim defect surrogate models (mean ± SD)
See this image and copyright information in PMC

References

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