Short proximal components in modular revision stems carry a higher risk for stem fractures

Abstract

Introduction: Fractures of modular hip revision stems are not uncommon. The current study examined implant-related factors on stem fracture. We hypothesised that in a modular stem the fracture risk is increased with the use of a short proximal implant component. Materials and methods: Anonymised data of all 32 patients in Switzerland with a Revitan modular hip system who had a stem fracture were obtained from the manufacturer. Implant and patient data were compared with all components implanted in Switzerland during the same time interval. Results: Between 2002 and 2017, 4834 Revitan stems were implanted, of which 32 fractured. A smaller size of the proximal stem component was significantly associated with a higher fracture risk ( p < 0.001). Compared with the control group, the proportion of male patients was higher among the fracture cases, patients were younger, and they had a higher body weight ( p < 0.001, respectively). Conclusions: The present study suggests that small proximal stem components increase the load at the modular junction due to size and lack of bony support. Surgeons should therefore avoid short proximal components so that the mid-stem junction lies as distally as possible and the risk of fracture is minimised.

Letter regarding “Short proximal components in modular revision stems carry a higher risk for stem fractures” by Falko Herold, Hubert Nötzli, and Henk Eijer

“…With a lot of interest, I read the above-mentioned paper. 1 I agree completely with the main conclusion of the paper that the use of a longer proximal modular component reduces the risk of fatigue failure at the taper junction of modular revision stems.…”

Analysis of modular taper fractures of the revision hip stem Prevision and comparison of the original and current taper design

“…4,9,11,13 However, recent analyses have shown satisfactory low failure rates of modular hip stems. 17,18 The aim of this analysis was to determine the clinical presentation and frequency of mechanical failure of the Prevision hip stem recorded in the manafacturer's vigilance database after more than 18 years of clinical experience, and in particular after a design change of the taper in 2008. Postoperative failures were divided into distal stem fractures, which could also occur in monobloc revision hip stems, and modular fractures.…”

EFORT recommendations for off-label use, mix & match and mismatch in hip and knee arthroplasty

“…high offset, short proximal component, lack of adequate medial bone supporting the junction area) seem to be more common in the obese patient. 33 – 36 Whilst one option to avoid taper connection fractures is to use a monobloc or non-modular implant, there is always a conflict when obesity is listed as a contraindication in the IFU.…”