Papers by Keyword: Hip Arthroplasty

Abstract: Stress shielding phenomenon is an important issues in considering the primary stability of the cementless hip arthroplasty. Stress shielding occurs when there is a mismatch in the elastic modulus of two materials perfectly bonded to each other, such as the prosthesis stem and the bone. In this study, influences of different prosthesis stem lengths on stress distribution in cementless THA are examined using finite element method. The calculated stress distribution is discussed with respect to stress shielding and primary stability issues in THA femur cases. Results show that similar pattern in stress distribution for intact and THA femur but differs in magnitudes. The stress level increases from the neck to the middle region and peaks at locations coinciding with the tip of the prosthesis. The maximum stress for intact femur is 55.5 MPa, THA with short stem is defined up to 112 MPa, while with medium and long stem are 204 MPa and 278 MPa, respectively.

Abstract: The goal of hip arthroplasty is to restore the patient to an active and pain free life for ever. Unfortunately, prosthetic implants fail because of loosening, wear or infection. This study sets out to ascertain whether or not Hydroxyapatite hip arthroplasty (HA) will produce long-lasting function of at least ten years in unselected patients of all ages and all diagnoses. Cemented implants used in hip arthroplasty often loosen after ten or more years of use. This is partly mechanical but also associated with debris disease arising from plastic wear products. Cementing techniques have been improved and the Swedish Hip Register [1] demonstrates that the revision rates have been reduced with improved cementing techniques. Revision surgery after cemented arthroplasty is difficult and may be complicated by fracture of the host bone Bioactive materials are being used to secure joint implants [2,3] and this paper presents the results of a consecutive series of hip arthroplasties carried out over a total period of over 19 years using the Furlong Hydroxyapatite Ceramic Coated hip prosthesis.[4, 5]

Abstract: This paper describes the clinical application of alumina ceramic and, more recently, Zirconia Toughened Alumina (ZTA), to the bearing surfaces of hip implants with a maximum follow up of fifteen years. Patients are assessed pre- and post-operatively using the Harris Hip Score. [1] X-rays are taken annually and, where appropriate, post mortem histological examination is carried out. Results are discussed. Some failures of alumina ceramic components have been seen and measures to prevent such incidents are described.

Abstract: Wear debris contributes to the development of granulomatous debris disease and loosening. It is accepted that hydroxyapatite ceramic (HA) will bond a prosthesis to bone.[1,2] Osteolysis has not been seen for several years after implantation but cases are now emerging [3]. Is HA still working Should we use hard on hard bearings Should we abandon polythene liners With a modular hip system, patients with polythene acetabular liners have been compared with those with ceramic liners. Polythene liners wear out and patients with a life expectancy of more than ten years should have ceramic/ceramic bearings.

Abstract: Uncemented hip arthroplasty is gaining interest. However, it is alleged that uncemented hip implants fail in osteoporotic bone because of early loosening and a higher incidence of periprosthetic fractures. Will Hydroxyapatite Ceramic Coated Hips (HAC) bond on to the osteoporotic bone and continue to function well in this vulnerable group of patients Post-menopausal women are prone to develop osteoporosis. They are seen too frequently with wrist, hip and spinal crush fractures following minor low impact injuries. These ladies also contribute to the cohort of patents requiring hip arthroplasty for all the usual diagnoses including sub capital fractures. This is a study of HAC hip arthroplasty in female patients over the age of sixty which includes women with osteoporosis.

Abstract: It has been shown that with high interfacial temperatures in hip bearings, it is possible to precipitate proteins, greatly reduce the compressive creep properties of ultrahigh molecular weight polyethylene (UHMWPE), and change the phase content of monolithic tetragonal zirconia. These induced features may alter the wear rate of UHMWPE. It was the objective of this study to examine the interfacial temperatures of oxidized zirconium (OxZr) heads as compared with metallic and ceramic heads coupled with polyethylene in a hip simulator. The interface temperatures were measured by placing thermocouples within 0.5 mm of the interface surface of both femoral heads and acetabular liners, and then articulating the surfaces using a 12-station AMTI anatomic hip simulator. The alumina femoral heads had the lowest average interfacial temperature, followed in increasing order by OxZr, CoCr, and zirconia. The ranking corresponds to the thermal conductivity of each material. A statistically significant difference (p<0.05) was found between all four materials for the femoral head temperature. No difference was seen in liner temperature between the alumina and OxZr groups, but statistical differences were found between all other combinations. Additionally, increasing head diameter, peak load, cyclic frequency, and serum concentration all resulted in statistically significant increases in both femoral head and liner temperatures.

Abstract: The Omnifit-HA femoral stem component has shown excellent results in early clinical studies. This is an independent prospective study of the outcome of a ydroxyapatite-coated femoral component implanted by one surgeon with an intermediate-term follow up. The senior author performed 103 consecutive uncemented total hip arthroplasties in 96 patients from July 1991 to December 1996. The components implanted were the Omnifit-HA femoral stem and the Omnifit PSL porous-coated acetabular shell. The mean age at the time of the index procedure was 52 years old (range, 27–78) and male:female ratio was 54:42. Three patients were deceased and four patients were lost to follow-up. The mean follow up was 10.3 years (range, 7.3–12.7 years). Clinical and radiographic evaluations were performed by an independent observer. The average preoperative and postoperative Harris Hip Scores were 55 and 92, respectively. The overall survivorship of the Omnifit-HA stem was 100% with no femoral revisions. The survivorship of the Omnifit PSL cup was 89.7% with 4 acetabular revisions for aseptic loosening and 6 polyethelene liner exchanges for osteolysis or late instability. The mean polyethylene wear rate was 0.24 mm per year. This long-term follow up shows that the use of circumferentially coated hydroxyapatite stems can protect against the migration of wear debris along the femoral stem.

Abstract: To reduce osteolysis and loosening, alumina bearings in hip arthroplasty have been used in Sunderland since 1991. This consecutive series demonstrates the results which have been most rewarding. However, ceramic implant fractures have been encountered but these probably represent less than meticulous operative technique. The results are published and the complications discussed together with advice to reduce the incidence of implant failure.

Abstract: Traditionally implants for hip arthroplasty are secured with bone cement. Problems have been encountered with cement fixation with loosening and osteolysis attributed to the reaction to particulate cement material and also polyethylene debris from wear. Cementing techniques have been improved and the Swedish Hip Register [1] demonstrates that the revision rates have been reduced with improved cementing techniques. However, uncemented hip arthroplasty is now having a revival. In particular, bioactive materials are being used and this paper presents the results of a consecutive series of hip arthroplasties carried out over a total period of just 16 years. All the patients are included, including primary and revision hip arthroplasty. Patients are assessed using the Harris Hip Score [2]. 13% of the hips scored less than 80 on the Harris Hip Score but only 9.4% scored poor pain scores. These represent the results of poor hip arthroplasty, of which an even smaller percentage are related to failed HA hip arthroplasty.