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. 2024 Jan;144(1):493-500.
doi: 10.1007/s00402-023-05058-8. Epub 2023 Sep 23.

An isoelastic monoblock cup versus a modular metal-back cup: a matched-pair analysis of clinical and radiological results using Einzel-Bild-Röntgen-Analyse software

Yama Afghanyar  1   2 , Jens Hendrik Möller  3 , Felix Wunderlich  4 , Jens Dargel  3 , Philipp Rehbein  3 , Erol Gercek  4 , Philipp Drees  4 , Karl Philipp Kutzner  4   3
Affiliations

An isoelastic monoblock cup versus a modular metal-back cup: a matched-pair analysis of clinical and radiological results using Einzel-Bild-Röntgen-Analyse software

Yama Afghanyar et al. Arch Orthop Trauma Surg. 2024 Jan.

Abstract

Introduction: Bone preservation and long-term survival are the main challenges in cementless total hip arthroplasty (THA). A good bone stock is especially important for adequate anchorage of the cup in revision cases. However, the optimal acetabular cup design for preserving good bone stock is still unclear. We aimed to compare clinical outcome, radiological alterations, migration, and wear at mid-term for two different cup types.

Materials and methods: This retrospective matched-pair study was performed using the data for 98 THA cases treated with a monoblock cup composed of vitamin E-blended highly cross-linked polyethylene (VEPE; monoblock group) or a modular cup composed of a highly cross-linked polyethylene (HXLPE) without an antioxidant (modular group). Clinical results were evaluated using the Harris Hip Score (HHS). The obtained radiographs were analyzed for radiological alterations, migration, and wear using Einzel-Bild-Röntgen-Analyse (EBRA) software.

Results: The mean follow-up duration was 73.2 ± 19.2 months (range: 32-108 months) and 60.5 ± 12.2 months (range: 20-84 months) in the monoblock and modular groups, respectively. HHS improved to 95.7 points in the monoblock group and 97.6 points in the modular group, without significant differences (p = 0.425). EBRA measurements were obtained in all cases. Acetabular bone alterations were not detected on radiological assessments. Mean cup migration was 1.67 ± 0.92 mm (range: 0.46-3.94 mm) and 1.24 ± 0.87 mm (range: 0.22-3.62 mm) in the monoblock and modular groups. The mean wear rate was 0.21 ± 0.18 mm (range: 0.00-0.70 mm) and 0.20 ± 0.13 mm (range: 0.00-0.50 mm) in the monoblock and modular groups. Both migration and wear pattern showed no significant differences (p = 0.741 and 0.243). None of the cases required revision surgery, yielding an implant survival rate of 100% in both groups.

Conclusion: The isoelastic press-fit monoblock VEPE cup and modular metal-back HXLPE cup showed equivalent mid-term wear and cup migration. Long-term studies are required to determine the effects of modularity, isoelasticity, and polyethylene stabilization with vitamin E on cup loosening and survival rates.

Keywords: Cup; Hip; Modular; Monoblock; THA; Vitamin E.

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Conflict of interest statement

Karl Philipp Kutzner and Philipp Rehbein have received research support and speaker honorarium from Mathys Ltd., Bettlach. All other authors have no relevant financial or non-financial interests to disclose.

Figures

Fig. 1
Fig. 1
The RM Pressfit vitamys cup with an optimys stem (Mathys Ltd., Bettlach, Switzerland)
Fig. 2
Fig. 2
The Fitmore cup (Zimmer Biomet, Warsaw, USA) with an optimys stem (Mathys Ltd., Bettlach, Switzerland)
Fig. 3
Fig. 3
Box plot of the Harris Hip Score (HHS) over time
See this image and copyright information in PMC

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