Introduction

Osteloysis following metal-on-UHMW polyethylene Total Hip Arthroplasty (THA) is well reported, as is lack of osteolysis following Ceramic-on-Ceramic (CoC)THA. Early ceramic failures did report some osteolysis, but in flawed implants. As 3rd and now 4th generation ceramic THAs come into mid- and long-term use, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. Osteolysis reported after 3rd generation CoC THA often included metallosis due to neck rim impingement. In our department we have revised only 2 hips in over 6000 CoC THAs for osteolysis. Both had evidence of metallosis as well as ceramic wear. The technique used by Radiologists for identifying the nature of lesions on CT is the Hounsfield score which will identify the density of the tissue within the lucent area. It is common for radiologist to have no access to previous imaging, especially pre-operative imaging if a long time has elapsed.

With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA which states there is osteolysis? Revision of such implants in elderly patients has a high risk of morbidity and mortality.

Introduction

The possibility of corrosion at the taper junction of hip replacements was initially identified as a concern of generating adverse reactions in the late 1980s. Common clinical findings of failure are pain, clicking, swelling, fluid collections, soft tissue masses, and gluteal muscle necrosis identified intra operatively.

Background

Total Hip Arthroplasty (THA) using the Direct Anterior Approach (DAA) is a muscle sparing approach which promotes early mobilisation of patients. It is a technically challenging approach shown to have a high rate of complications, especially during the learning curve. Here we present the results of 157 cases of THA via a DAA on a standard theatre table, with a minimum of 6 months follow-up.

Introduction and Aims

The 21^st Century has seen ceramic bearings become an increasingly popular choice in total hip arthroplasty due to their high wear resistance and inert wear debris without osteolysis promising a long term bearing solution. Early ceramic bearings were hindered by fracture but improved manufacturing processes and materials subsequently produced stronger ceramics. These third generation ceramics showed greatly reduced fracture rates but there is limited evidence in the literature reporting their long term survival and wear characteristics. The purpose of this study was to determine osteolysis and survival rates of Alumina ceramic bearings in cementless total hip arthroplasties with a minimum follow-up of 15 years.

Introduction

Squeaking is a potential problem of all hard on hard bearings yet it has been less frequently reported in metal-on-metal hips. We compared a cohort of 11 squeaking metal-on-metal hip resurfacings to individually matched controls, assessing cup inclination and anteversion between the groups to look for any differences.

Introduction

The success of total hip arthroplasty has meant its indications have been extended to the younger more active patient. Due to the higher activity levels and increased demands of these patients, revision rates have been traditionally higher than when compared to older patients [1]. Ceramic on ceramic bearings may offer a viable long term solution as manufacturing methods have evolved resulting in improved mechanical properties, particularly of third and fourth generation ceramics. We report the outcome of primary cementless, alumina-on-alumina hip arthroplasty with a minimum 10 year follow up in 110 patients under the age of 55 years of age at time of surgery.

Introduction

The Delta Motion device (developed by Finsbury Orthopaedics, Leatherhead, United Kingdom, now manufactured by DePuy, Leeds, United Kingdom) is a pre-assembled factory fitted cup. It has been introduced to overcome some of the concerns relating to intra-operative assembly with improper seating of the liner and chipping. This device has a thinner shell and liner in comparison with other cups, allowing the use of larger sized heads which should help reduce the risk of impingement and dislocation. A drawback of the pre-assembled design is the inability to use supplementary screws to achieve stability and the difficulty in obtaining primary stability compared with a thin titanium shell. To date we are not aware of any publications reviewing the outcomes of these devices.

Introduction

Modularity is being increasingly used throughout the world for both primary and revision total hip arthroplasty. Recently there have been concerns of increased corrosion and fretting at the modular junctions. In the SROM® modular hip system, two modular junctions are the head-neck taper junction and the stem-sleeve taper junction. The aim of this study was to investigate corrosion at these junctions with the use of different bearing materials.

Introduction

Edge loading commonly occurs in all bearings in hip arthroplasty. Edge loading wear can occur in these bearings when the biomechanical loading axis reaches the edge and the femoral head loads the edge of the cup producing wear damage on both the head and cup edge. When the biomechanical loading axis passes through the polished articulating surface of the acetabular component and does not reach the edge, the center of the head and the center of the cup are concentric. The resulting wear known as concentric wear is low in metal-on-metal (MOM) bearings, and is negligible in ceramic-on-ceramic (COC) bearings. Edge loading is well defined in COC hip bearings. However, edge loading is difficult to identify in MOM bearings, since the metal bearing surfaces do not show wear patterns macroscopically. The aims of this study are to compare edge loading wear rates in COC and MOM bearings, and to relate edge loading to clinical complications.

Edge loading commonly occurs in all bearings in hip arthroplasty. The aim of this study compares metal bearings with edge loading to alumina bearings with edge loading and to metal bearings without edge loading.

Seventeen failed large diameter metal-on-metal hip bearings (8 total hips, 9 resurfacings) were compared to 55 failed alumina-on-alumina bearings collected from 1998 to 2010. The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.).

The median time to revision for the metal hip bearings and the alumina hip bearings was 2.7 years. Forty-six out of 55 (84%) alumina bearings and 9 out 17 (53%) metal bearings had edge loading wear (p<0.01). The average volumetric wear rate for metal femoral heads was 7.87 mm3/yr (median 0.25 mm3/yr) and for alumina heads was 0.78 mm3/yr (median 0.18 mm3/yr) (p=0.02).

The average volumetric wear rate for metal heads with edge loading was 16.51 mm3/yr (median 1.77 mm3/yr) and for metal heads without edge loading was 0.19 mm3/yr (median 0 mm3/yr) (p=0.1). There was a significant difference in gender, with a higher ratio of females in the alumina group than the metal group (p=0.02).

Large diameter metal femoral heads with edge loading have a higher wear rate than smaller alumina heads with edge loading. Metal-on-metal bearings have low wear when edge loading does not occur.

Aim

Alumina ceramic on ceramic bearings in total hip arthroplasty (THA) may reduce the prevalence of osteolysis due to its properties of low wear and chemical inertness. This is critical in the younger patient population as they place increased demands over a longer period. This study reports on the clinical and radiographic outcomes of a series of modern cementless ceramic on ceramic THA at a minimum of 10 years in this younger group.