Head replacement, head rotation, and surface damage effects on metal-on-metal total hip replacements: A hip simulator study

Hip resurfacing arthroplasty in inflammatory arthritis a 3- to 5-year follow-up study

The success of hip resurfacing in younger patients with primary osteoarthritis has paved the way for the trial of the procedure in patients with secondary osteoarthritis of the hip. We retrospectively reviewed the clinical and radiologic results in a cohort of 23 patients (32 hips) with inflammatory arthritis who were chosen for hip resurfacing after normalizing vitamin D levels and ruling out proximal femoral osteopenia using dual-energy x-ray absorptiometry. At a minimum follow-up of 3 years, there was failure in only 1 hip due to fracture of the femoral neck attributable to osteonecrosis of the remnant head. The clinical outcome was evaluated using Harris hip score and was found to be good to excellent in 30 of 31 hips. Hip resurfacing is a promising alternative in carefully chosen patients with inflammatory arthritis.

Complications after metal-on-metal hip resurfacing arthroplasty

This article determines the incidence and cause of the complications commonly associated with metal-on-metal hip resurfacing implants and the proposed methods to prevent these complications. The literature available in PubMed was reviewed. Complication rates after hip resurfacing are low, and the procedure has shown both safety and efficacy in the hands of surgeons trained in specialized centers. Proper surgical technique can further reduce the incidence of femoral neck fracture, component loosening, and abnormal wear of the prosthesis. A more systematic detection of adverse local tissue reactions is needed to provide accurate assessments of their prevalence.

Transient elastohydrodynamic lubrication analysis of a novel metal-on-metal hip prosthesis with a non-spherical femoral bearing surface

Effective lubrication performance of metal-on-metal hip implants only requires optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry.

A meta-analysis of design- and manufacturing-related parameters influencing the wear behavior of metal-on-metal hip joint replacements

This article aims to clarify the influence of design- and manufacturing-related parameters on wear of metal-on-metal (MoM) joint bearings. A database search for publications on wear simulator studies of MoM bearings was performed. The results of published studies were normalized; groups with individual parameters were defined and analyzed statistically. Fifty-six investigations studying a total of 200 implants were included in the analysis. Clearance, head size, carbon content, and manufacturing method were analyzed as parameters influencing MoM wear. This meta-analysis revealed a strong influence of clearance on running-in wear for implants of 36-mm diameter and an increase in steady-state wear of heat treated components.

Effect of bearing size on the long-term wear, wear debris, and ion levels of large diameter metal-on-metal hip replacements-An in vitro study

Hip resurfacing arthroplasty has become a popular alternative to conventional hip surgery. Surface replacements with bearing sizes of 55 mm (n = 5) and 39 mm (n = 5) were tested in a hip simulator for 15 million cycles (Mc). Wear debris was isolated from the serum lubricant and characterized by field emmitting gun scanning electorn microscopy, and ion levels were measured via inductively coupled plasma mass spectroscopy at intervals throughout the test. The 39 mm bearings showed significantly greater bedding in volumetric wear (2.58 mm(3)) compared with the 55 mm bearings (1.15 mm(3)). There was no significant difference between the steady state wear rates (1-15 Mc) between the two sizes (0.10 and 0.09 mm(3)/Mc, respectively); however, this parity only became clear after 7 Mc. The wear debris isolated was oval in morphology with a mean particle size of 28 nm and a range of 9-108 nm. The Co levels measured at 0.13 Mc were significantly greater than at 3.6 Mc for both bearing sizes (10926 ppb and 176 ppb, respectively). After 0.5 Mc, the Co levels from the 39 mm bearings were significantly higher than the 55 mm (11,007 vs. 1475 ppb). The wear results support previous findings showing that increasing the femoral head size decreased volumetric bedding in wear. The ion levels measured suggest both bearing sizes have similar initial wear rates; however, the 55 mm bearings reach steady state wear more rapidly.

Der Oberflächenersatz am Hüftgelenk

Resurfacing arthroplasty is regarded as an attractive method, especially for the young patient who needs a hip replacement. However, the high expectations regarding this new technique in THR must first be met. Earlier experiences with similar forms of surface replacement have led to high revision rates with early aseptic wear induced component loosening and neck fractures. Technical progresses in production techniques for metal-on-metal articulations with minimized wear have enabled the introduction of new surface replacements for the hip joint. Long-term results of these resurfacing arthroplasties are still due. Femoral neck fractures and femoro-acetabular impingement are possible early complications which require revision. The implantation of these systems requires a high degree of operative skill and experience on the part of the surgeon. Approach dependent trauma to the musculature and endangering of the blood supply to the femoral head is balanced with the positive effect of the preservation of femoral bone stock and better options in case of revision. Whether the younger patient with a higher activity profile and an increased chance of implant loosening actually profits from the resurfacing arthroplasty will be determined in the future.