Inferior outcome after hip resurfacing arthroplasty than after conventional arthroplasty: Evidence from the Nordic Arthroplasty Register Association (NARA) database, 1995 to 2007

Today, total hip arthroplasty (THA) is one of the safest and most efficient surgical treatments. New materials, surgical techniques and design concepts intended to improve THA have not always been successful. Thorough preclinical and early clinical investigations can detect some aspects of under-performing, while continuing surveillance is recommended to detect and analyze reasons for any later appearing flaws. In this thesis, several ways to monitor and assess THA performance are explored and carried out, using survival analysis in registry studies, radiostereometry (RSA), radiology and clinical outcome. In Paper I, a study using the Nordic Arthroplasty Register Association (NARA) registry shows that HRA had an almost 3-fold increased early non-septic revision risk and that risk factors were found to be female sex, certain HRA designs and units having performed few HRA procedures. Papers II and III contain comparisons of highly cross-linked polyethylene (XLPE) and conventional polyethylene (PE). XLPE had a considerably lower wear rate up to 10 years but showed no obvious improvements regarding implant fixation, BMD or clinical outcome. In the NARA registry, in 2 of 4 studied cup designs the XLPE version had a lower risk of revision for aseptic loosening compared to the PE version. Paper IV describes that stem subsidence and retrotorsion measured with RSA at 2 years predicted later aseptic stem failure in an unfavorably altered, previously well-functioning cemented femoral stem. In Paper V and VI, a novel approach to measure articulation wear with RSA in radiodense hip arthroplasty articulations was presented and evaluated. Subsequently, a comparison between ceramic-on-ceramic (COC) and metal-on-conventional PE uncemented THA displayed a considerably lower wear rate, smaller periacetabular bone lesions and a relatively high squeaking rate, the latter with unknown long-term consequences, in the COC hips. Implant fixation, heterotopic ossification and clinical outcome did not differ between articulation types. In conclusion, it was confirmed that implant surveillance can be done with RSA, also in radiodense THA. Early migration predicts later aseptic implant failure. Prolonged surveillance can confirm long-term material and design performance, verify or contradict anticipated advantages as well as detect unanticipated long-term complications

The Effectiveness of Blood Metal Ions in Identifying Patients with Unilateral Birmingham Hip Resurfacing and Corail-Pinnacle Metal-on-Metal Hip Implants at Risk of Adverse Reactions to Metal Debris

We investigated whether blood metal ions could effectively identify patients with metal-on-metal hip implants with two common designs (Birmingham Hip Resurfacing [BHR] and Corail-Pinnacle) who were at risk of adverse reactions to metal debris.Patients who underwent metal-on-metal hip arthroplasty performed with unilateral BHR or Corail-Pinnacle implants and who had blood metal ions below our implant-specific thresholds were at low risk of adverse reactions to metal debris. These thresholds could be used to rationalize follow-up resources in asymptomatic patients. Analysis of cobalt alone is acceptable. Implant-specific thresholds were more effective than currently recommended fixed authority thresholds for identifying patients at risk of adverse reactions to metal debris requiring further investigation

The Effectiveness of Blood Metal Ions in Identifying Patients with Unilateral Birmingham Hip Resurfacing and Corail-Pinnacle Metal-on-Metal Hip Implants at Risk of Adverse Reactions to Metal Debris

We investigated whether blood metal ions could effectively identify patients with metal-on-metal hip implants with two common designs (Birmingham Hip Resurfacing [BHR] and Corail-Pinnacle) who were at risk of adverse reactions to metal debris.Patients who underwent metal-on-metal hip arthroplasty performed with unilateral BHR or Corail-Pinnacle implants and who had blood metal ions below our implant-specific thresholds were at low risk of adverse reactions to metal debris. These thresholds could be used to rationalize follow-up resources in asymptomatic patients. Analysis of cobalt alone is acceptable. Implant-specific thresholds were more effective than currently recommended fixed authority thresholds for identifying patients at risk of adverse reactions to metal debris requiring further investigation

Does surgical approach influence component positioning with Birmingham Hip Resurfacing?

The aim of this study was to compare the component positioning of Birmingham Hip Resurfacings implanted through a posterolateral approach with those inserted via a direct lateral approach. Sixty-four hip resurfacings for osteoarthritis were carried out by a single surgeon: 23 through a direct lateral approach and 41 through a posterolateral approach. No significant differences in implant survival, Oxford Hip Scores or complications were found. The mean abduction angle for the acetabular component was lower (p < 0.007) with a posterior approach (mean: 37.5°; range 26–50°) than the lateral approach (mean: 43°; range 30–56°). There was no significant difference in stem orientation, either in flexion/extension or varus/valgus, between the two groups. This study demonstrates that components can be implanted in an acceptable orientation through either approach but that the posterior approach results in greater closure of the acetabular component