Preliminary report of clinical experience with metal-on-highly-crosslinked-polyethylene hip resurfacing

Abstract

Objectives Modern metal-on-metal (MoM) hip resurfacing arthroplasty (HRA), while achieving good results with well-orientated, well-designed components in ideal patients, is contraindicated in women, men with head size under 50 mm, or metal hypersensitivity. These patients currently have no access to the benefits of HRA. Highly crosslinked polyethylene (XLPE) has demonstrated clinical success in total hip arthroplasty (THA) and, when used in HRA, potentially reduces metal ion-related sequelae. We report the early performance of HRA using a direct-to-bone cementless mono-bloc XLPE component coupled with a cobalt-chrome femoral head, in the patient group for whom HRA is currently contraindicated. Methods This is a cross-sectional, observational assessment of 88 consecutive metal-on-XLPE HRAs performed in 84 patients between 2015 and 2018 in three centres (three surgeons, including the designer surgeon). Mean follow-up is 1.6 years (0.7 to 3.9). Mean age at operation was 56 years (sd 11; 21 to 82), and 73% of implantations were in female patients. All patients were individually counselled, and a detailed informed consent was obtained prior to operation. Primary resurfacing was carried out in 85 hips, and three cases involved revision of previous MoM HRA. Clinical, radiological, and Oxford Hip Score (OHS) assessments were studied, along with implant survival. Results There was no loss to follow-up and no actual or impending revision or reoperation. Median OHS increased from 24 (interquartile range (IQR) 20 to 28) preoperatively to 48 (IQR 46 to 48) at the latest follow-up (48 being the best possible score). Radiographs showed one patient had a head-neck junction lucency. No other radiolucency, osteolysis, component migration, or femoral neck thinning was noted. Conclusion The results in this small consecutive cohort suggest that metal-on-monobloc-XLPE HRA is successful in the short term and merits further investigation as a conservative alternative to the current accepted standard of stemmed THA. However, we would stress that survival data with longer-term follow-up are needed prior to widespread adoption. Cite this article: R. B. C. Treacy, J. P. Holland, J. Daniel, H. Ziaee, D. J. W. McMinn. Preliminary report of clinical experience with metal-on-highly-crosslinked-polyethylene hip resurfacing. Bone Joint Res 2019;8:443–450. DOI: 10.1302/2046-3758.810.BJR-2019-0060.R1

Trends and developments in hip and knee arthroplasty technology

“…To date, 88 MoX resurfacings have been implanted. 9 This articulation has the potential to minimise metal ion release and with the lower stiffness of polyethylene there is reduced potential for stress shielding seen with stiffer acetabular components, though this is at the possible risk of increased volumetric polyethylene wear. 10…”

Despite higher revision rate, MoM large-head THA offers better clinical scores than HR: 14-year results from a randomized controlled trial involving 48 patients

“…If the encouraging results of these studies are confirmed in the long term then the use of CoC LDH THA, would be a favorable alternative to HR in the young active patient. In recent years, CoC or MoP HR were also introduced but femoral head necrosis and loosening would stay unresolved [ 8 , 27 , 28 ].…”

Capsular ligaments provide a passive stabilizing force to protect the hip against edge loading

“…This is particularly relevant in the context of hip resurfacing as it is equivalent to the differences in subtended arc angle between implant designs that were found to be susceptible to edge loading wear, and those that were more tolerant of adverse loading. 39 , 40 Further, the near native-sized head diameters of these devices mean that the wrapping function of the ischiofemoral ligament is maintained, a factor that also benefits dual mobility THA. 41 It may explain why in previous work, an increased risk of dislocation was found when the ischiofemoral ligament was unrepaired.…”