Impingement in total hip arthroplasty: A geometric model.

Total Hip Arthroplasty (THA) is one of the most common and successful surgical interventions. The survivorship at 10 years for the most commonly used systems is over 95%. However, the incidence of revision is usually much higher in the 0-1 year time period following the intervention.

Evaluation of a new methodology to simulate damage and wear of polyethylene hip replacements subjected to edge loading in hip simulator testing.

Wear and fatigue of polyethylene acetabular cups have been reported to play a role in the failure of total hip replacements. Hip simulator testing under a wide range of clinically relevant loading conditions is important. Edge loading of hip replacements can occur following impingement under extreme activities and can also occur during normal gait, where there is an offset deficiency and/or joint laxity.

Comparison of ceramic-on-metal and metal-on-metal hip prostheses under adverse conditions.

Ceramic-on-metal (COM) hip replacements, where the head is BIOLOX® Delta ceramic and the liner is CoCrMo alloy, have demonstrated reduced wear under standard simulator conditions compared to metal-on-metal (MOM) bearings. COM hips are now being used clinically around the world. MOM hip resurfacings have raised concerns regarding poor clinical performance and increased in vivo wear was associated with steeply inclined acetabular components and translationally malpositioned components.

Squeaking hip arthroplasties: a tribological phenomenon.

The clinical incidence of squeaking has been reported with increasing frequency, with ceramic-on-ceramic bearings seemingly most affected. This study investigated potential causes of squeaking in hard-on-hard hip bearings through 2 sets of experimental conditions. Bearing clearance appeared to affect the incidence of squeaking in metal-on-metal surface arthroplasties.

Wear of ceramic-on-carbon fiber-reinforced poly-ether ether ketone hip replacements.

Total hip replacement has been a successful surgical intervention for over 50 years, with the majority of bearings using a polyethylene cup. Long-term failure due to osteolysis and loosening has been widely documented and alternative bearings have been sought. A novel carbon fiber-reinforced poly-ether ether ketone (CFR-PEEK) cup was investigated through experimental friction and wear studies.

Changes in whole blood metal ion levels following resurfacing: serial measurements in a multi-centre study.

Seventy-seven patients implanted with unilateral resurfacing prosthesis were recruited from four centres. Serial whole blood samples were collected and ion levels were analysed. In most cases, the ion levels stabilized by 3 months.

The influence of clearance on friction, lubrication and squeaking in large diameter metal-on-metal hip replacements.

Large diameter metal-on-metal bearings (MOM) are becoming increasingly popular, addressing the needs of young and more active patients. Clinical data has shown excellent short-to-mid-term results, though incidences of transient squeaking have been noted between implantation and up to 2 years post-operative. Geometric design features, such as clearance, have been significant in influencing the performance of the bearings.

A hip joint simulator study of the performance of metal-on-metal joints: Part II: design.

The separate and combined roles of head diameter and clearance were studied experimentally in simulator tests and also theoretically. Head diameters ranging from 16-54 mm and various clearances were studied. Effective mixed-film lubrication achieved through careful design and manufacture greatly reduced wear.

A hip joint simulator study of the performance of metal-on-metal joints: Part I: the role of materials.

The use of metal-on-metal low-wearing bearings has promoted great interest in the factors determining the volume of wear debris generated in such joints, including the developing surface replacement alternatives. Twenty-six pairs of low- and high-carbon components in wrought or cast form of 36 mm nominal diameter and exhibiting similar clearances were studied over 5 million test cycles in a 10-station hip joint simulator. Low-carbon cast materials exhibited higher wear than high-carbon cast or wrought materials.