Abstract
BackgroundMetal-on-metal hip resurfacing arthroplasty (HR) has been gaining popularity especially for young and active patients. Although different series report good mid-term results, the long-term outcome and failure mechanisms are still concerning. In this consecutive revision case series, 9 retrieved specimens of a failed Birmingham Hip Resurfacing (BHR) were divided according to the time to fracture: 3 specimens failed at less than 6 months (Group 1), 3 failed between 6 months and 3 years (Group 2) and 3 failed later than 3 years (Group 3). The objective of the study was to examine by a specific quantitative histomorphometry and microtomography (micro-CT) method the characteristics of bone quality and its microarchitecture in retrieved metal-on-metal HR.MethodsA series of 948 BHR were performed between 2001 and 2009. Among these implants 10 failures occurred and nine of these underwent revision surgery and were examined by histomorphometry and micro-CT.ResultsHistomorphometry showed a significant increase in trabecular separation (Tb.Sp) in Group 3 in comparison with Group 1 (113%, p < 0.05). In the top region, micro-CT showed that Groups 2 and 3 presented significant lower bone volume (Group 2: 61%, p < 0.005; Group 3: 1%, p < 0.05), trabecular number (Group 2: 53%, p < 0.005; Group 3: 40%, p < 0.05), and higher Tb.Sp (Group: 71%,p < 0.05) when compared to Group 1. Additionally, histomorphometry showed that the top regions in Group 1 had a significantly lower mean percentage of empty osteocyte lacunae than the top regions in both Group 2 and 3 (p < 0.05).ConclusionsThis study showed that the morphometric parameters considered are crucial for a good understanding of mechanical properties of HR and may be of significant importance in the pathogenesis of HR failure particularly in the development of late fractures.
Highlights
Metal-on-metal hip resurfacing arthroplasty (HR) has been gaining popularity especially for young and active patients
This study showed that the morphometric parameters considered are crucial for a good understanding of mechanical properties of HR and may be of significant importance in the pathogenesis of HR failure in the development of late fractures
It is clear that we require a better understanding of the failure mechanisms of the current generation of metal-on metal HR implants, no studies have ever used histomorphometric and microtomographic evaluation to evaluate the characteristics of bone quality and its microarchitecture in retrieved metal-on-metal HR
Summary
Metal-on-metal hip resurfacing arthroplasty (HR) has been gaining popularity especially for young and active patients. Different series report good mid-term results, the long-term outcome and failure mechanisms are still concerning In this consecutive revision case series, 9 retrieved specimens of a failed Birmingham Hip Resurfacing (BHR) were divided according to the time to fracture: 3 specimens failed at less than 6 months (Group 1), 3 failed between 6 months and 3 years (Group 2) and 3 failed later than 3 years (Group 3). HR long-term follow up confirms its superiority in comparison with total hip replacement [3,4] Various complications, such as femoral neck fracture [5,6,7], avascular necrosis [8,9] and pseudotumour formation [10,11], as well as unexplained pain, aseptic loosening [12], and osteolysis [4] have been reported. Good correlations were found between the structural parameters determined by microtomography (μCT) images and those assessed on histomorphological slices [20]
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