HIP UPDATE IN 2012 

Minerva Ortopedica e Traumatologica 2012 April;63(2):111-23

Copyright © 2012 EDIZIONI MINERVA MEDICA

language: English

Revisions of metal-on-metal hip resurfacing: causes, treatment options and improved outcome

De Smet K. A. ¹, Van Der Straeten C. ²

¹ Department of Orthopedic Surgery, ANCA Medical Center, Ghent, Belgium; ² Independent Consultant Clinical Research, Rheumatologist, Ghent, Belgium

Metal-on-metal hip resurfacing arthroplasty (MoMHRA) has been used in increasing numbers to treat hip pathologies in young and active patients. The reasons for HRA revision have evolved with improving surgical experience and techniques. Ease of revision was a perceived advantage but studies have shown an increased risk of re-revision and poor revision outcome with adverse soft tissue reactions. The aim of this study was to investigate the causes of failure and the operative findings in all consecutive HRA revisions performed at an independent specialist centre and to identify factors that improve revision outcome. One hundred and thirteen HRA revisions performed by a single surgeon (2001-2010) were retrospectively reviewed. Forty-three primary surgeries were done at our centre, the remaining elsewhere. Eight different HRA designs were revised mainly in females (60%). The mean time to revision was 31 months (0-101). Component orientation was measured using EBRA. Histological evaluation was performed at an independent specialist laboratory. Harris Hip Score (HHS) was obtained pre-revision and at latest follow-up (mean: 3 years; 0.5-10 years). The initial experience of the first 42 cases (Initial Group) was previously reported (2008). Cases 43-113 comprised the Later Group. Ion levels were used as a diagnostic tool since 2006 (N.=74). The most common cause of revision was cup malpositioning (N.=57; 50%) and the most common intra-operative finding was an adverse soft tissue reaction (N.=50; 44%) usually correlated with high metal ions. There was a higher incidence of component malpositioning, osteolysis, elevated metal ions, and metal sensitivity in women. HHS significantly improved postrevision (P<0.001). Ten complications and 6 re-revisions occurred. The incidence of complications/re-revisions was significantly reduced since the introduction of metal ions (P=0.004). Patients of the Later group were noted to have less soft tissue damage, had significantly bigger femoral heads implanted at surgery, were educated of the increased complication risk and wore a brace for 6 weeks. Outcome, complication and re-revision rates were significantly better in the later group compared to the Initial group, even in the presence of soft tissue reactions. Component malpositioning was the most common cause of HRA failure. Surgical experience, evaluation of metal ion levels, use of large diameter bearings other than metal and patient education are important factors in improving HRA revision outcome. Patients with soft tissue reactions can have good outcome if operated prior to extensive soft tissue destruction.