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The impact of canal flare index on leg length discrepancy after total hip arthroplasty

  • Hip Arthroplasty
  • Published:
Archives of Orthopaedic and Trauma Surgery Aims and scope Submit manuscript

Abstract

Introduction

The femoral stem should protrude from femur by an appropriate vertical distance to allow leg length equalization at hip arthroplasty; this distance depends on the size/shape of medullary canal and implant. The relationship between femoral morphology and achievability of leg length restoration is currently unclear. Our aim was to examine the impact of the femoral canal flare index (CFI) on the risk of leg length discrepancy (LLD) after total hip arthroplasty with different femoral stems.

Materials and methods

The study cohort included 126 patients with unilateral primary total hip arthroplasty due to idiopathic osteoarthritis and three different types of implanted femoral stems. The impact of CFI on postoperative LLD was assessed with separate logistic regression model for each implant and covariables of age, gender, body mass index and femoral neck resection level.

Results

Higher CFI was an independent risk factor for postoperative LLD ≥ 5 mm with odds ratio 4.5 (p = 0.03) in 49 stems with cementless metaphyseal fixation Implantcast-EcoFit®, regardless of the femoral neck resection level. CFI had no significant impact on LLD in 30 stems with cementless diaphyseal fixation EndoPlus-Zweymüller® or 47 cemented collared stems Link-SPII®. No significant difference was observed between groups in pre/postoperative WOMAC scores, postoperative radiographic LLD, subjectively reported LLD, insole use or complications after mean 6.8 years of follow-up.

Conclusions

Higher CFI increases the risk of clinically detectable postoperative LLD in single-wedge femoral stems with cementless metaphyseal fixation. CFI has no significant impact on LLD in femoral stems with cementless diaphyseal fixation or cemented fixation.

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Authors and Affiliations

  1. University Medical Centre Ljubljana and Faculty of Medicine, Zaloška 9, 1000, Ljubljana, Slovenia

    Peter Brumat, Borut Pompe, Vane Antolič & Blaž Mavčič

Authors
  1. Peter Brumat
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  2. Borut Pompe
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  3. Vane Antolič
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  4. Blaž Mavčič
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Corresponding author

Correspondence to Blaž Mavčič.

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Conflict of interest

All authors declare that they have no conflict of interest with regard to this study.

Ethical approval

The study protocol was reviewed and approved by the National Medical Ethics Committee of the Republic of Slovenia on August 19, 2014, case No.# 97/08/14.

Human and animal rights statement

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study who provided prospectively collected data. For retrospective data formal consent is not required.

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Brumat, P., Pompe, B., Antolič, V. et al. The impact of canal flare index on leg length discrepancy after total hip arthroplasty. Arch Orthop Trauma Surg 138, 123–129 (2018). https://doi.org/10.1007/s00402-017-2840-6

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  • DOI: https://doi.org/10.1007/s00402-017-2840-6

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