Hip simulators are designed to reproduce the forces and motion patterns of normal walking. In vivo demands on total hip replacements, however, are varied and often more severe than normal walking conditions. It is these severe conditions that often lead to implant failure. This is clinically based research aimed at understanding some of the more severe conditions in hips and the effect that these have on the performance of the total hip replacement. The polyethylene liner can act as a pump in an acetabular component, forcing fluid and wear particles through the holes to the retroacetabular bone causing osteolysis. Ten patients were studied at revision surgery. Pressures were measured in retroacetabular osteolytic lesions while performing pumping manouvers with the hip. Two laboratory experiments were then designed to study pumping mechanisms in vitro. In patients with contained osteolytic lesions, fluid pressure fluctuations could be measured in the lesion in association with the pumping action. Patients with uncontained osteolytic lesions showed no such pressure fluctuations. In the laboratory we identified 3 distinct mechanisms whereby fluid can be pumped from the hip joint to the retroacetabular bone. These pumping effects could be mitigated by improved implant design. Loading of the femoral head against the edge of the acetabular component produces dramatically increased contact pressures particularly in hard-on-hard bearings. In an analysis of 16 retrieved ceramic-on-ceramic bearings we were able to characterise the mechanism of edge loading based on the pattern of edge loading wear on the bearing surface. Finally in a radiographic study of patients with squeaking ceramic-on-ceramic hips. Squeaking was found to be associated with acetabular component malposition. It seems that edge loading or impingement may be an associated factor in these cases.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 95 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 85-92).

Skapaitė L. Kineziterapijos poveikio įvertinimas po klubo sąnario endoprotezavimo dėl koksartrozės; magistro baigiamasis darbas / mokslinis vadovas doc. A. Kimtys; Kauno medicinos universitetas, Slaugos fakultetas, Reabilitacijos klinika. – Kaunas, 2008. Darbo tikslas buvo įvertinti kineziterapijos poveikį asmenims po klubo sąnario endoprotezavimo dėl koksartrozės antrame reabilitacijos etape. Reabilitacijos kurso trukmė buvo 30 dienų. Tyrime dalyvavo 21 vienos ligoninės Fizinės medicinos ir reabilitacijos skyriaus pacientas po klubo sąnario endoprotezavimo dėl koksartrozės. Tiriamąją grupę sudarė 2 vyrai (9%) ir 19 moterų (91%), kurių amžius 50-70 metų. Pacientai buvo suskirstyti į dvi grupes pagal amžių. Pirmojoje grupėje – 7 pacientai, kurių amžius 50-65 metai (33%), antrojoje grupėje – 14 pacientų, kurių amžius 66-70 metų (67%). Tiriamųjų amžiaus vidurkis buvo 65,9 ± 6,09 metai. Pirmosios grupės pacientų amžiaus vidurkis 58,9 ± 5,96 metai, antrosios grupės pacientų amžiaus vidurkis 69,4 ± 1,01 metai. Pacientai buvo tiriamai du kartus: pirmąjį – tik atvykus į Fizinės medicinos ir reabilitacijos skyrių, antrąjį kartą – prieš išvykstant pacientui iš šio skyriaus. Kineziterapijos poveikiui vertinti buvo atliekami šie tyrimai ir testai: šlaunies raumenų jėga vertinama naudojant Oxford skalę, judesių amplitudės klubo sąnaryje – goniometriniu metodu, paciento mobilumas – pagal modifikuotą Keitel indeksą, skausmas - naudojant vizualinės analogijos skausmo skalę... [toliau žr. visą tekstą] / The aim of the study was to evaluate the effect of physiotherapy in patients after hip replacement in second stage of rehabilitation. Duration of rehabilitation course was 30 days. The study included a group of 21 patients from Rehabilitation department in one hospital after hip replacement because of coxarthrosis. Exploration shows, that more patients were women - 19 (91%), and men – 2 (9%). The age of the patients in this group was from 50 to 70 years. The average age of them was 65,9 ± 6,09 years. Patients was grouped according to age in two groups. In first group – 7 patients who‘s age was from 50 to 65 years (33%) and in second group – 14 patients who‘s age was from 66 to 70 years (67%). The average age of the patients in first group was 58,9 ± 5,96 years, in second group – 69,4 ± 1,01 years. The effect of physiotherapy was performed using the Oxford scale, goniometry technique, Keitel‘s index, Pain Visual Analog Scale, Barthel‘s index. We evaluated these indexes at two times – before rehabilitation course and after rehabilitation course. The muscle strength after rehabilitation course increased in both groups (p<0,05). The range of motions after rehabilitation course increased in both groups (p<0,05). Level of the pain after rehabilitation course decreased in both groups (p<0,05). Keitel‘s index after rehabilitation course increased in both groups (p<0,05). Barthel‘s index after rehabilitation course increased in both groups (p<0,05).

Total hip arthroplasty (THA) is a successful surgical technique that can be used for the effective treatment of fractured neck of femur, osteoarthritis, tumours, avascular necrosis, failed internal fixation, developmental dysplasia and rheumatoid arthritis. Revision surgery is necessary if loosening allows relative motion between the femoral stem and femur, causing pain and mechanical instability of the THA. The large number of revision operations undertaken each year as a result of implant failure emphasises the need for better biomechanical understanding of the femoral implant system. During 2001-02 in Australia 26,689 hip replacement operations were performed, with 3,710 of these being revision operations. The Exeter stem is the most commonly used cemented stem for primary and revision hip replacement in Australia. It is therefore very important to understand the mechanics of this clinically successful implant. Few studies have presented a through investigation into the mechanics of the Exeter stem from a fundamental perspective. To address these issues, mechanical and finite element (FE) methods were used to conduct experiments and numerical investigations into the mechanics of the Exeter stem. The femur geometry, for both the experimental and FE studies, was based upon the Sawbones model 3303 medium left third generation femur. The stem orientation for all specimens of the study was replicated from the orientation achieved by the senior surgeon implanting into the Sawbones femur. Test rigs were designed specifically to constrain the femur for the purposes of loading and stability measurements. The experimental investigation was used to investigate the torsional mechanical stability of the stem and to monitor this stability following periods of cyclic loading, using a resultant hip contact force, while monitoring the distal migration of the stem. The experimental investigation was also able to provide data for the validation of the finite element model. The resultant hip contact force was represented experimentally by a cyclic load of 1Hz applied to the head of the implant. The specimen was tested for four days. The loading regime for the initially implanted specimen involved the application of load for 6 hours a day, allowing the specimen to relax under no load for 18 hours a day. The mechanical stability of the initially implanted specimen was tested prior to the application of the cyclic load and immediately after the loading periods, prior to relaxation. Further tests were undertaken to assess the mechanical stability of the stem following the removal and reimplantation of the same stem without the use of additional bone cement (a procedure used surgically when only the acetabular component requires replacement). The reimplanted specimens were tested for a further two days following reimplantation. The six hours of loading for the reimplanted specimen was achieved using three, two hour loading periods. The stability of the reimplaned stem was assessed following each loading period. Initial studies found that the material properties of the Sawbones femurs were highly temperature dependent. If the temperature of the short glass fibre reinforced (SGFR) epoxy used for the cortical bone analogue was increased from room temperature to body temperature there was a reduction in the Young's modulus of up to 37 percent. This finding led to further investigation into the strain state of the femur for varus and neutral stem orientations to reduce femur failure during cyclic loading. The strains of the varus stem orientation were found to be higher than the strains of the neutral stem. The experiments investigating the mechanical stability under cyclic loading continued using the neutral stem orientation. For the neutral stem orientation it was found that there was no perceivable variation in the torsional stiffness of the initially implanted system during the cyclic loading period even though distal migration was observed. Torsional stiffness was observed to be compromised immediately after reimplantation. However, the torsional stiffness of the reimplanted specimen was recovered within the first two hour loading period. No perceivable variation in the torsional stiffness was observed between the initially implanted specimens and the reimplanted specimens following the first two hours of loading. The finite element model (FEM) found good agreement with the experimental investigation in terms of measured strain at two of three rosette positions and failure of the cortical bone. Trends for the stress-strain state of the stem showed good agreement with the clinical findings of failure and wear of the stem. The stress-strain state of the cement predicted the expected compressive and hoop stresses once debonding of the stem-cement interface had progressed. Strain on the surface of the femur was well predicted for pure torsional loading. The FEM has provided a valuable tool for future investigation of the effect of factors such as implant positioning on femoral component mechanics. The experimental and finite element models developed within the scope of this project have provided a powerful analysis tool for the investigation of the femoral component mechanics in THA. Application of the model to clinically relevant problems has given valuable insight into the mechanisms behind the success of this particular implant type. Models such as this will provide information on implant failure modes that will further lead to an increased implant life expectancy and a reduction in the number of revision operations performed.

Thesis (MAppSc in Physiotherapy)--University of South Australia, 1997

Thesis (MHlthSc(OccTh))--University of South Australia, 1999

Thesis (MAppSc in Physiotherapy)--University of South Australia, 1996

Thesis (MAppSc in Physiotherapy)--University of South Australia, 1997

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.