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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXI | Pages 105 - 105
1 May 2012
M. H G. T D. B D. M G. A
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Introduction

Varus positioning of cemented ‘composite beam’ stems is associated with increased risks of aseptic loosening and stem fracture. We investigated whether the incidence of varus malalignment of the Exeter polished, double taper design in a multicentre prospective study adversely affected outcome after total hip replacement (THR).

Materials & Methods

A multicentre prospective study of 1189 THR was undertaken to investigate whether there is an association between surgical outcome and femoral stem malalignment. The primary outcome measure was the change in the Oxford hip score (OHS) at five years. Secondary outcomes included the rate of dislocation and revision, stem subsidence, quality of cementing. 938 (79.89%) were followed-up at five years.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXI | Pages 45 - 45
1 May 2012
H. R G. A R. H
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Purpose

The purpose of this study was to investigate the difference in the level of pre- and 6 months post-operative objective and subjective measures of disability between patients with full-thickness rotator cuff tears and those with impingement syndrome/low grade partial thickness rotator cuff tears. Impact of age, gender, and job demands was taken into consideration.

Methods

Standardised pre- and post-operative data were collected on consecutive patients who had undergone surgery related to rotator cuff pathology. A disease-specific disability measure, the Western Ontario Rotator Cuff (WORC) Index which explores five domains of physical symptoms – life style, work, sports, and emotions – was the primary outcome. Paired and independent non-parametric statistics and multivariable regression analysis were performed.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_II | Pages 379 - 379
1 Jul 2008
G A Hamer A Stockley I Eastell R Wilkinson J
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Introduction: The concept that aseptic loosening is a function of polyethylene wear has led to the use of cross-linked polyethylene in total hip arthroplasty (THA). We studied the relationship between polyethylene wear rate and aseptic loosening in order to model the potential effects of wear-reducing strategies on the failure rate for each prosthetic component.

Methods: 350 subjects who had previously undergone Charnley THA were divided into 3 groups: Controls (n=273); those with loosening of only the femoral stem (n=43); and those with only cup loosening (n=34). Poly-ethylene wear was measured using a validated method (EBRA). The relationship between wear rate and loosening was examined using logistic regression analysis, and estimates of the effect of wear rate modulation made using odds-ratios.

Results: The median annual wear rate in the controls (0.07mm) was lower than both stem looseners (0.09mm, p=0.002) and cup looseners (0.18mm, p< 0.001). The odds of cup loosening increased 4.7 times per standard deviation (SD) increase in wear rate above the reference (control) population (p< 0.001). The odds of stem loosening increased 1.7 times per SD, but was not independent of other risk factors (p> 0.05). The potential reduction in risk of loosening was calculated using the following formula: (OR^SD2)/(OR^SD1), where 1 and 2 are the new and old mean z-score wear rates. Thus, for a 25% or 50% reduction in wear rate, the incidence of cup loosening may reduce by 71% and 293%, respectively. The rate of stem loosening may, at best, reduce by 7% and 17%, respectively.

Discussion: Wear reduction strategies, such as cross-linked polyethylene, have the potential for a major impact on the incidence of cemented cup, but not stem, loosening.


The Journal of Bone & Joint Surgery British Volume
Vol. 57-B, Issue 3 | Pages 390 - 391
1 Aug 1975
G. A