The initial recommendation for the postoperative regime after uncemented total hip arthroplasty (THA) was 6-12 weeks of partial weight bearing (PWB) to obtain a stable implant position during bone ingrowth. In recent years patients with uncemented THA have increasingly practiced full weight bearing (FWB) after surgery, which has largely been based on clinical experience rather than on scientific evidence. The aim of this thesis was to investigate the effects of FWB versus PWB for 3 months on the stability of the implants and on bone mineral density (BMD), as well as body composition (BC) of the lower extremities. We used radiostereometric analysis (RSA) to measure implant micromotion and dual X-ray absorptiometry (DXA) to measure BMD and BC. Forty-six patients with strictly unilateral osteoarthritis of the hip (OAH) received uncemented THA. These patients were then randomized to the FWB or PWB groups and followed for 5 years. In a preoperative cross-sectional study the BMD of the hip and heel were compared between the OAH-affected side and the healthy side. The study showed an increase of BMD at the femoral neck and a decrease at the total hip and trochanter. The results of a RSA study of cup stability showed that there might be minimal movement in medial and proximal directions during the first postoperative week. These results indicate that the RSA baseline investigation of uncemented cups should be performed as early as possible after the first postoperative day. FWB had no adverse effects on the stability of the uncemented press-fit cups or the uncemented cementless Spotorno (CLS) femoral stems after a 5-year follow-up. There was no difference in periprosthetic BMD around the CLS stem regardless of the postoperative weight bearing regime. All zones around the femoral stem indicated a recovery in BMD toward baselines, except the calcar region, which showed progressive loss in BMD to -22% at 5 years post-surgery. FWB had no effect on the changes in BC after surgery. In conclusion, FWB is safe in uncemented THA in terms of stability, BMD and BC. Furthermore, THA apparently counteracts age-related changes in BC but not in BMD.

New surgical approaches for total hip arthroplasty (THA) are being developed to reduce muscle damage sustained during surgery, in the hope to allow better muscle functioning afterwards. The goal of this study was to compare the muscle sparing anterior (ANT) approach to a traditional lateral (LAT) approach with three-dimensional motion analysis. Kinematics and kinetics were obtained with an infrared camera system and force plates. It was hypothesized that (1) the ANT group would have closer to normal range of motion, moments and powers, compared to the LAT group, and that (2) the ANT group would have higher peak hip abduction moment than the LAT group. Forty patients undergoing unilateral THA for osteoarthritis between the ages of 50 and 75 (20 ANT, 20 LAT) were asked to perform three trials of walking, stair ascent and stair descent. Patients were assessed between six to twelve months postoperatively. Twenty age- and weight-matched control participants (CON) provided normative data. Results indicated that both THA groups had gait anomalies compared to the CON group. Both THA groups had reduced hip abduction moment during walking (CON vs. ANT: p<0.001; CON vs. LAT: p=0.011), and the ANT group had a significantly lower hip abduction moment compared to the LAT group (p=0.008). Similar results were observed during stair descent, where the ANT group had reduced peak hip abduction moment compared to the CON group (p<0.001) and the LAT group (p=0.014). This indicates that the anterior approach did not allow better gait and stair climbing ability after THA. It is therefore thought that other variables, such as preoperative gait adaptations, trauma from the surgery, or postoperative protection mechanisms to avoid loading the prosthetic hip, are factors that might be more important than surgical approach in determining the mechanics of THA patients after surgery.

Bakgrund: Primär total höftplastik utförs vanligtvis på patienter med höftledsartros när konservativ behandlings smärtlindrande effekter inte är tillräckliga. Efter ingreppet kan postoperativa rörelserestriktioner tillämpas för att minska luxationsrisken. Rörelserestriktionerna har emellertid ifrågasatts då studier visat att något samband mellan tillämpande av restriktioner och minskad risk för luxation inte föreligger. Syfte: Kartlägga tillämpande av postoperativa rörelserestriktioner vid svenska sjukhus som genomför primär total höftplastik med direktlateralt snitt samt undersöka skillnader mellan universitets-/regionsjukhus, länssjukhus, länsdelssjukhus och privatsjukhus avseende tillämpandet av restriktioner. Studien syftade även till att kartlägga icke-standardiserade restriktioner. Metod: Tvärsnittsstudie med en deskriptiv och komparativ studiedesign. Totalt svarade 42 sjukhus på en egenkonstruerad webbenkät som utgjorde underlaget för datainsamlingen. Resultat: Vilka postoperativa restriktioner som tillämpades för flexion över 90°, utåtrotation över 45°, inåtrotation över 45°, adduktion över neutralläge samt flexion över 90° kombinerat med samtidig rotation och adduktion varierade på de deltagande sjukhusen. Det förelåg inga signifikanta skillnader mellan sjukhusgrupperna gällande nämnda rörelser. Flera sjukhus tillämpade icke-standardiserade restriktioner baserade på patients individuella förutsättningar samt kunde variera beroende på protestyp. Även rekommendationer om att undvika extrema rörelser förekom. Konklusion: Det är en variation gällande vilka restriktioner som tillämpas efter primär total höftplastik. Med hänsyn till denna studies resultat samt aktuell evidens bör postoperativa restriktioner fortsatt diskuteras. / Background: Total hip arthroplasty (THA) is commonly performed on patients with hip osteoarthritis when conservative treatment no longer reliefs pain sufficiently. Movement restrictions are applied to prevent hip dislocations, although those have recently been questioned since studies have shown that a liberal regimen does not increase the risk of hip dislocation. Purpose: To chart movement restrictions following THA performed with a direct lateral approach at Swedish hospitals and analyzes differences in those between university hospital, county hospitals, district hospitals and private hospitals. This study also aimed to chart non- standardized movement restrictions. Method: A cross-sectional study with a descriptive and comparative design. Data was collected from a self-made web survey, which was answered by 42 hospitals. Results: The appliance of restrictions regarding flexion beyond 90°, external rotation beyond 45°, internal rotation beyond 45°, adduction beyond centerline and flexion of 90° or beyond combined with adduction and rotation varied among the participating hospitals. There were no significant differences between participating hospital groups regarding mentioned movements. Non-standardized restrictions were influenced by the individual factors of the patient as well as the prosthesis type. Patients were also recommended to not perform any extreme movements. Conclusion: There is a variation regarding appliance of postoperative restrictions during the first six weeks postoperatively. In the light of the results of this study, together with recent evidence postoperative, restrictions should be further discussed.

New surgical approaches for total hip arthroplasty (THA) are being developed to reduce muscle damage sustained during surgery, in the hope to allow better muscle functioning afterwards. The goal of this study was to compare the muscle sparing anterior (ANT) approach to a traditional lateral (LAT) approach with three-dimensional motion analysis. Kinematics and kinetics were obtained with an infrared camera system and force plates. It was hypothesized that (1) the ANT group would have closer to normal range of motion, moments and powers, compared to the LAT group, and that (2) the ANT group would have higher peak hip abduction moment than the LAT group. Forty patients undergoing unilateral THA for osteoarthritis between the ages of 50 and 75 (20 ANT, 20 LAT) were asked to perform three trials of walking, stair ascent and stair descent. Patients were assessed between six to twelve months postoperatively. Twenty age- and weight-matched control participants (CON) provided normative data. Results indicated that both THA groups had gait anomalies compared to the CON group. Both THA groups had reduced hip abduction moment during walking (CON vs. ANT: p<0.001; CON vs. LAT: p=0.011), and the ANT group had a significantly lower hip abduction moment compared to the LAT group (p=0.008). Similar results were observed during stair descent, where the ANT group had reduced peak hip abduction moment compared to the CON group (p<0.001) and the LAT group (p=0.014). This indicates that the anterior approach did not allow better gait and stair climbing ability after THA. It is therefore thought that other variables, such as preoperative gait adaptations, trauma from the surgery, or postoperative protection mechanisms to avoid loading the prosthetic hip, are factors that might be more important than surgical approach in determining the mechanics of THA patients after surgery.

The development of total hip arthroplasty has reached a state when quality prostheses are made, whose longevity is influenced significantly by material properties, design, component fixation and rate of wear of the articulating surfaces. It is the wear rate which is the most important factor influencing successful results for the use of total hip prostheses. The aim of this thesis is to perform a research on the various combinations of hip prostheses and its loading conditions. Also an experimental measurements of Bovine serum lubricating film thickness between the artificial femoral head and a glass disc are performed for different contact kinematic conditions.

Study Objective Although data from the Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Venous Thrombosis and Pulmonary Embolism (RECORD) 1-4 trials have shown a similar postoperative bleeding risk between rivaroxban and enoxaparin in patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA), anecdotal observations from local institutions have suggested that postoperative bleeding rates seemed higher in patients who received rivaroxaban than those reported in the RECORD trials. Thus, the objective of this pilot study was to assess postoperative bleeding events observed in clinical practice in patients receiving rivaroxaban after undergoing THA and TKA and to compare their results with those published in the RECORD trials. Design Retrospective cohort study with a comparator group of patients from the RECORD 1-4 trials. Setting Two institutions within a regional health care system. Patients Four hundred forty adults who received at least one dose of rivaroxaban 10 mg daily after undergoing THA or TKA in the two institutions between August 2011 and October 2013 (cohort group), and 6183 patients who received rivaroxaban in the RECORD 1-4 trials (comparator group). Measurements and Main Results Postoperative bleeding was assessed in the cohort patients versus the patients in the RECORD trials. The primary outcome, occurrence of any postoperative bleeding, was a composite of major and clinically relevant nonmajor bleeding as defined in the RECORD trials. Any postoperative bleeding occurred in 6.8% of the cohort patients versus 3.2% of the RECORD trial patients (p<0.0001); 1.4% of the cohort patients versus 0.38% of the RECORD trial patients suffered a major bleed (p=0.013). Within defined major bleeding, bleeding leading to reoperation and clinically overt extrasurgical site bleeding resulting in either a hemoglobin level decrease of at least 2 g/dl or transfusion of 2 units or greater of packed red blood cells were reported in 0.68% versus 0.19% (p=0.073) and 0.68% versus 0.13% (p=0.032), respectively, of the cohort patients versus the RECORD trial patients. Conclusion Overall, any postoperative bleeding in the cohort patients occurred significantly more frequently than that observed in the RECORD trial patients. The major bleeding rate was also significantly higher in the cohort patients, influenced by higher rates of bleeding leading to reoperation and clinically overt extrasurgical site bleeding resulting in either a hemoglobin decrease of at least 2 g/dl or transfusion of two units or greater of packed red blood cells. These findings from our pilot study are thought provoking and, thus, invite further investigation.

京都大学 / 0048 / 新制・論文博士 / 博士(人間健康科学) / 乙第13033号 / 論人健博第2号 / 新制||人健||3(附属図書館) / 32991 / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 坪山 直生, 教授 黒木 裕士, 教授 妻木 範行 / 学位規則第4条第2項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

First devised over half a century ago, metal-on-polyethylene (MoP) hip prostheses have become the gold standard for total hip arthroplasty (THA), a surgical intervention for degenerative hip joint conditions. The accumulation of polyethylene wear debris after long-term, in vivo articulations, can induce adverse cellular reactions, osteolysis and aseptic loosening of the implant – ultimately resulting in the failure of the THA. Despite the distinct differences between the biotribology of MoP and MoM prostheses, there is a lack of congruent high resolution research investigating the biotribological interactions and surface structures of MoP hip prosthesis components. This study characterized the surface and subsurface microstructural changes in failed MoP hip prosthesis retrievals using advanced electron microscopy techniques. The samples were comprised of retrieved metallic cobalt-chromium-molybdenum (CoCrMo) alloy femoral head components, one ultra-high molecular weight polyethylene (UHMWPE) acetabular cup component, and unused CoCrMo reference samples. The surface of the reference samples contained linear, parallel, uniform scratches as a result of the manufacturing process; whereas the surface of the retrieval samples were covered in an abundance of scratches and a layer of residual deposits, attributable to in vivo articulation of the implant. Characteristic hard phases were observed and examined on the surface and from the cross-sectional preparation of the cast CoCrMo samples. The multiphasic hard phases on the cast samples can strengthen the material but also be sites of crack propagation and material detachment, contributing to the generation of wear particles. Lastly, a nanocrystalline layer, 20 to 400 nm in thickness was observed in the subsurface microstructure of all samples (including references). Previous MoM studies suggest that the nanocrystalline layer is a result of dynamic crystallization in response to multidirectional, chronic loading in vivo, however, the presence of the layer in the unimplanted references suggest that the nanocrystalline layer can be formed during the production of the prosthesis component and therefore, pre-exists implantation. The imperfections on new, unused implants can have protective effects (e.g. troughs from scratches can be a reservoir for wear debris) but may influence in vivo wear processes after implantation (e.g. scratches may be a source of wear debris). Higher resolution analyses on more retrieval and reference samples are required to pinpoint the exact mechanism of failure in MoP hip prostheses and extend the longevity and efficacy of THA. / Thesis / Master of Applied Science (MASc)

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