This study reports the ten-year outcomes of a three-arm, multicentre randomised controlled trial comparing Cobalt-Chrome (CoCr) and Oxidised Zirconium (OxZr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) versus highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and XLPE liner; Group B received an OxZr femoral head and XLPE liner; and Group C received an OxZr femoral head and UHMWPE liner. The outcomes of 262 study patients were analysed at ten years follow-up.

At ten years, increased linear wear rates were recorded in group C compared to group A (0.133 ± 0.21 mm/yr vs 0.031 ± 0.07 mm/yr respectively, p<0.001) and group B (0.133 ± 0.21 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p<0.001). Patients in group C had increased risk of osteolysis and aseptic loosening requiring revision surgery compared with group A (7/133 vs 0/133 respectively, p=0.007) and group B (7/133 vs 0/135 respectively, p=0.007). There was a non- significant trend towards increased liner wear rates in group A compared to group B (0.031 ± 0.07 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p=0.128). All three groups were statistically comparable preoperatively and at ten years follow-up from a clinical score perspective.

The use of UHMWPE was associated with progressively increased annual liner wear rates. At ten years follow-up, this translated to an increased incidence of osteolysis and aseptic loosening requiring revision, compared with XLPE. Femoral heads composed of OxZr were associated with a non-significant trend towards reduced wear rates compared to CoCr, but this did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two treatments groups.

INTRODUCTION

Historically, the clinical performance of novel implants was usually reported by designer surgeons who were the first to acquire clinical data. Regional and national registries now provide rapid access to survival data on new implants and drive ODEP ratings. To assess implant performance, clinical and radiological data is required in addition to implant survival. Prospective, multi-surgeon, multi-centre assessments have been advocated as the most meaningful. We report the preliminary results of such a study for the MiniHip™femoral component and Trinity™ acetabular component (Corin Ltd, UK).

Introduction

In Total Hip Arthroplasty (THA), polyethylene wear reduction is key to implant longevity. Oxidized Zirconium (OxZi) unites properties of a ceramic bearing surface and metal head, producing less wear in comparison to standard Cobalt-Chromium (CoCr) when articulating with Cross-linked polyethylene (XLPE) in vitro. This study investigates in vivo polyethylene (PE) wear, outcomes and complications for these two bearing couples in patients at 5 year follow-up

The optimum approach for Total Hip Arthroplasty is hotly debated. Many surgeons, especially the newly trained, have been wary of the posterior approach because of higher reported rates of dislocation.

We analysed 137 consecutive patients who underwent Primary Total Hip Replacement for Osteoarthritis during the first three years of practice of a newly appointed consultant with an interest in hip and knee arthroplasty. All surgeries were either performed by or under the direct supervision of the senior author. The posterior capsule and short external rotators were reattached to the Greater Trochanter as a routine.

Data was gathered prospectively by proforma for all the patients, one at the time of operation and one each at 3 months and 12 months from the surgery. 4 patients died due to causes unrelated to their arthroplasty (2.9%) and 6 patients (4.3%) were lost to follow up.

The patients were grouped into A, B and C depending on involvement of one hip, both hips and multiple joint diseases respectively and the patients were analysed for pain scores (1–6), function scores (1–6) and satisfaction levels (1–5) after the surgery. All the complications during and after surgery were noted, and special emphasis was laid on the incidence of dislocation, and factors contributing to it. The results were compared with the incidence reported in the literature for posterior and other approaches.

The results were gratifying and were comparable with major series of Total Hip Replacement via the posterior approach. Only one patient (0.7%) had a dislocation. This occurred during the index admission when the patient sat down on a ward toilet without a raised toilet seat. The hip was reduced under General Anaesthesia and he had no problem thereafter. 122 patients (96%) had no pain or minimal pain not limiting the activity after the surgery but 5 patients (4%), 3 from Group C had activity related pain or pain at rest. 93 patients (73%) were walking without a stick after surgery and 34 patients (27%) were using a stick for extra safety. 5 patients (4%) had superficial infection which settled with antibiotics and one patient (0.7%) had deep infection which required a Revision hip surgery. 6 patients developed Deep Vein Thrombosis (4.7%) and one patient (0.7%) had Pulmonary Embolism but all the patients returned to good function after treatment. One patient (0.7%) developed transient Sciatic nerve palsy but recovered completely.

We conclude that the posterior approach, already known to cause less blood loss and to allow optimum component positioning and alignment, is compatible with a low overall rate of early complications. Specifically, the dislocation rate is low and comparable with large series performed by approaches traditionally considered to carry a lower rate of dislocation.