Total hip replacement (THR) is one of the most successful and most frequently performed operations. For most implants the published rate of revision at 10 years is less than 10%. However the revision rates are higher for younger and more active patients who are likely to outlive their implants. The most frequent cause of THR failure is aseptic loosening, commonly accompanied by bone loss at the implant site. THR revisions give worse functional results and fail sooner than primary THR and are complicated by this loss of bone stock. A resurfacing hip prosthesis replaces the diseased surface layer of bone and cartilage and retains the majority of the femoral head. The stress distribution in the proximal femur is closer to that in an intact hip. A conservative resurfacing prosthesis will present the surgeon with no greater problems at revision than encountered at primary conventional 11-JR. Early designs of resurfacing prosthesis conserved femoral bone stock at the expense of acetabular bone. Revision rates were high and while some failures were caused by avascular necrosis and femoral neck fracture the predominant cause was acetabular loosening. The design of a bone conserving prosthesis requires knowledge of the shape of the bony surfaces of the hip joint. A survey of the morphology of the acetabulum showed a wide variation in shape. While early resurfacing designs had hemispherical acetabular cups the bony surface is less than hemispherical. The morphology and desired range of hip motion constrain prosthesis thickness and shape. A novel resurfacing design using a polyacetal femoral component and an UHMWPE acetabular component is proposed. This bearing combination has a lower volumetric wear rate than an equivalent Co-Cr on UHWMPE bearing. Computer modelling of the resurfacing concept showed that lower moduli materials reduced stress shielding and distributed implant-bone interface stresses more evenly. Mechanical testing of polyacetal following immersion in Ringer's solution showed substantial decreases in Young's modulus while strength was unaffected.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains vii, 79 p. : ill. Includes abstract. Includes bibliographical references (p. 71-79).

In the project a method to calculate the displacement of hip prostheses inside a hip socket is made. The project, performed as a bachelor thesis project is a cooperation between Karolinska Institute and Uppsala University. Hip replacements are expensive surgeries. Loosening is a large problem for orthopedists and patients, and costs both time and expenses. If dislocations of hip prostheses are detected in an early stage, preventions to reduce the loosening can be done. The method is programmed in Matlab code utilizing Computational Tomographic Images (CT). The CT images are built up by putting 0.5 [mm] wide X-ray slices after each other. In the project a model of a human hip made of plastic is used with two real hip prostheses, one for each hip, and small balls, around some [mm] in diameter, made of tantalum are located inside the plastic bone. The purpose of the tantalum balls are to mark the bones’ position and makes it easier toget exact coordinates from the X-ray images of the bone structure.

As implant survival extends into the second and third decades focal osteolysis around cemented femoral components in total hip replacement is emerging as an important failure mechanism. Whilst the problem of focal osteolysis is well recognised, there are many aspects of its development which are poorly understood. The broad aim of this thesis is to try to provide some insights into how, why and where focal osteolysis develops around the cemented femoral component. There are broadly two sections to this thesis, chapters 2-5 present clinical and geometrical studies and chapters 6-10 a series of experimental studies. The aim of the first section was to establish what is observed in clinical practice, the aim of the second to try to explain these findings. A mid-term clinical study showed that focal osteolysis is more common with rough than polished stems that differed in no aspect other than their surface finish. Further studies established that focal osteolysis is probably always associated with defects in the cement mantle. These defects occur anteriorly at the mid-stem of the prosthesis and posteriorly at the component tip. The distribution of focal osteolysis and its strong association with cement mantle defects suggests the importance of the stemcement interface as a pathway for fluid and debris to reach the distal femur. However, at 15-25 years, osteolysis rarely develops with the polished Exeter stem even in the presence of confirmed defects in the cement mantle, suggesting that the stem seals the stem-cement interface against fluid and debris. In an attempt to explain the clinical findings a series of bench top experiments were undertaken. These studies showed that the behaviour of fluid and dye at the stemcement interface was significantly influenced by component surface finish. Bonded and debonded stem-cement interfaces of rough stems provided an incomplete barrier to fluid movement along this interface. In contrast, polished stems both bonded and debonded were able to provide a seal at the stem-cement interface. The seal at this interface was improved with component subsidence in the presence of rotational stability. It is believed that this thesis provides a rationale explanation for why focal osteolysis rarely develops around the Exeter stem in clinical practice. It also explains how, where, and why osteolysis develops around certain designs of cemented femoral components used in total hip replacement.

Thesis (MAppSc in Physiotherapy) -- University of South Australia, 1998

Thesis (MAppSc in Physiotherapy) -- University of South Australia, 1998

Thesis (MTech (Biomedical Sciences))--Cape Peninsula University of Technology, 2015. / Previous international studies have documented a marked variation in transfusion practice for Total Hip Replacement (THR) surgery. This is despite widespread dissemination of clinical guidelines for the use of blood products. The cost and potential wastage of blood products as well as concerns regarding patient care and outcomes are important drivers of optimal blood management. The aim of this study was to audit red cell product utilisation for THR surgeries at two tertiary referral hospitals.

Text in Afrikaans / In this quantitative study emphasis is placed on the role of the nurse as a member of the rehabilitation team. Furthermore, the role of the nurse in patient education as well as the importance of effective patient education during the rehabilitation process after hip replacement surgery is emphasised. Various factors that impacted on the rehabilitation process are highlighted. A structured interview schedule was used to interview a group of 20 respondents. All of the respondents participated voluntarily. Orem's Selfcare Theory was used as a theoretical basis for the study. The researcher determined which information respondents regarded as important to attain functional independence during the rehabilitation process. The data gathered would serve as recommendation for a planned information brochure that could in future be given to patients at their first visit to the surgeon before surgery. The brochure could then be used as a basis for patient education in the course of the rehabilitation process. / Advanced Nursing Sciences / M.A. (Verpleegkunde)

Text in Afrikaans / In this quantitative study emphasis is placed on the role of the nurse as a member of the rehabilitation team. Furthermore, the role of the nurse in patient education as well as the importance of effective patient education during the rehabilitation process after hip replacement surgery is emphasised. Various factors that impacted on the rehabilitation process are highlighted. A structured interview schedule was used to interview a group of 20 respondents. All of the respondents participated voluntarily. Orem's Selfcare Theory was used as a theoretical basis for the study. The researcher determined which information respondents regarded as important to attain functional independence during the rehabilitation process. The data gathered would serve as recommendation for a planned information brochure that could in future be given to patients at their first visit to the surgeon before surgery. The brochure could then be used as a basis for patient education in the course of the rehabilitation process. / Advanced Nursing Sciences / M.A. (Verpleegkunde)

Periacetabular osteolysis is a significant complication following total hip replacement surgery. It is believed to be caused by wear debris and high fluid pressures within the joint capsule. To investigate the mechanisms by which high fluid pressures are generated in total hip replacement, a physical model of the hip joint was constructed, the Acetabular Pressure Transmission Rig (APTR). An aluminium chamber held the bone analogue, a polyurethane hemisphere with a 52mm acetabular cavity, and the prosthetic components, a 28mm femoral head and various uncemented cups, were inserted without press-fit to simulate cup loosening. A synovial fluid analogue was introduced into the chamber through an elevated reservoir. Rigid transmission tubes conducted fluid pressures from the cup-cavity interface to external transducers. The APTR was loaded under various conditions and the pressures produced by the loading regimes were analysed. Pressures over 35kPa, previously shown by other groups to cause osteolysis, were measured within the APTR, reaching a maximum of 131.3kPa measured at the pole of the cup. Changes in load application led to pressure changes within the APTR, with higher loading frequency and magnitude leading to higher median pressure amplitudes. The presence of different component features, such as screw holes in the metal shell, was also shown to affect periacetabular pressures. Tests with a fibrous rim interposed between the prosthetic cup and the test cavity showed an 88% reduction in periacetabular pressures, as the increased rim interference between cup and cavity prevented fluid ingress behind the cup. A larger initial separation between the loading head and the acetabular cup caused a significant increase in measured pressures, with a 0.15mm increase in head-cup separation producing a 53% increase in pressures measured at the pole of the cup. Pressure differentials between different transducer sites indicated the ability for fluid flow behind the cup, which can be related in vivo to the movement of particulate debris to periacetabular bone. The APTR was able to measure clinically significant pressures and to analyse the effects of modifying component and loading characteristics with currently available prosthetic components. This makes the rig useful in a clinical context, as it has been shown to be capable of testing a broad range of component types under a wide range of conditions. Its use will ensure new prostheses and fixation modes can be designed in such a way as to eliminate the damaging fluid pressures currently observed in artificial hip joint replacements.