Abstract
Introduction: Polyethylene wear and subsequent osteolysis remain obstacles to the long-term survivorship of total hip arthroplasty (THA). Highly cross-linked polyethylene (XLPE) with radical quenching represents a massive leap forward with dramatically improved wear rates compared to ultra-high molecular weight polyethylene (UHMWPE). In this study we evaluate the wear of UHMWPE and XLPE coupled with oxidized zirconium (OxZr) femoral heads. Methods: A longitudinal, retrospective analysis was performed identifying consecutive patients who received a 28-mm OxZr-on-polyethylene primary THA from 2003 to 2004 by a single, high-volume arthroplasty surgeon. Patients were divided into two groups: those that received (1) UHMWPE liner and (2) a highly XLPE liner. Patients were included if clinical follow-up was complete to 2014 or later. Radiographic analysis was performed by two blinded observers. Measures included cup position, annual linear wear rate, and presence of osteolysis. Pairwise comparisons, correlations, and inter-rater reliability were calculated. Results: Eighty patients were in the UHMWPE group with an average follow-up of 10 ± 1.23 years and 88 patients in the XLPE group with an average of 10 ± 1.03-year follow-up. Average age (68) was similar between groups (p = 0.288). Observer reliability was excellent for cup abduction (ICC = 0.940), anteversion (ICC = 0.942), and detection of osteolysis (ICC = 0.811). Annual linear wear rates were significantly higher (p = 1 × 10−19) with UHMWPE (0.21 ± 0.12 mm/year) compared to XLPE (0.05 ± 0.03 mm/year). Linear wear rate was significantly correlated to decreasing acetabular abduction (p = 0.035). Osteolysis was noted only in the UHMWPE group, with 17 patients (21.2%) exhibiting acetabular osteolysis and 37 (46.3%) patients exhibiting femoral osteolysis. Conclusions: OxZr coupled with XLPE showed minimal wear and no osteolysis at 10-year follow up. The yearly linear penetration rate is similar to that seen in other studies of XLPE THA. A careful longitudinal follow-up will be required to determine if advanced bearings such as OxZr or ceramic can show improved performance in the second decade of implantation.
Highlights
Polyethylene wear and subsequent osteolysis remain the most common reason for revision in the medium to long term following total hip arthroplasty (THA) [1, 2]
A sixth ultra-high molecular weight polyethylene (UHMWPE) patient was revised for a periprosthetic fracture, with acetabular component revision being performed for an incidental intraoperative finding of severe osteolysis
The long-term success of THA is largely dependent on avoiding periprosthetic osteolysis by minimizing polyethylene wear
Summary
Polyethylene wear and subsequent osteolysis remain the most common reason for revision in the medium to long term following total hip arthroplasty (THA) [1, 2]. Particulate debris generated by polyethylene produces an inflammatory tissue response that leads to retroacetabular and femoral osteolysis, with subsequent loosening of these components [3]. Previous investigations have associated a causal link between wear debris and osteolysis [4] and a polyethylene linear wear rate of 0.1 mm/year is widely quoted to be the threshold for which osteolysis occurs [5]. Several studies have demonstrated that first-generation XLPE is associated with a significantly lower annual wear rate compared to UHMWPE as well as a significantly lower rate of radiographic signs of osteolysis [9, 11,12,13].
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