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 cervical spine must provide structural support for the head, allow large range of motion and protect both the spinal cord and branching nerves. There are two types of spinal joints: the intervertebral discs which are flexible connections and the facets, which are articulating synovial joints. Both types degenerate with age. Current surgical treatments include spinal fusion and articulating disc replacement implants. If both disc and facet joints are degenerated, fusion is the only option. In spinal fusion, the disc is removed and the adjacent vertebrae are fused which causes abnormally high stress levels in adjacent discs. In disc replacement, an articulating device is inserted to restore intervertebral motion and mimic healthy spinal kinematics. Disc arthroplasty does not significantly increase adjacent level stress but the lack of rotational constraint causes increased facet contact pressures. Thus, there is a need for a cervical total level arthroplasty system (CTLAS) that has a disc implant specifically designed to preserve the facet joints and implants for facet arthroplasty that can act independently or in-unison with the disc replacement. The conceptual design of a CTLAS implant system was proposed that would replace the disc and the facet joints. To facilitate medical imaging, PEEK (polyetheretherkeytone) was selected as the structural and bearing material. In the present thesis, multi-station pin-on-plate wear testing was initiated for pairs of unfilled (OPT) and carbon-fiber-reinforced (CFR) PEEK. Wear is important in arthroplasty implant design because wear particles can cause osteolysis leading to loosening. A variety of experiments were performed to investigate the effects of load, contact geometry and lubricant composition on wear. CFR PEEK was found to have much lower and more predictable wear than OPT PEEK in the present experiments. The wear of OPT PEEK pairs showed sensitivity to lubricant protein concentration. The coefficient of friction during testing was found to be quite high (up to 0.5), which might have clinical implications. Also, some subsurface fatigue was found, exposing carbon fibers of CFR PEEK. This remains a concern for its long-term application. Further wear testing is recommended using actual implants in a spine wear simulator.

Bibliography: leaves 198-219. / xii, 219 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the effect of implant design on the femoral bone remodelling response in a sheep cemented hip arthroplasty model. The clinical section of the thesis also indicates the importance of biological factors in the femoral bone remodelling response. / Thesis (Ph.D.)--University of Adelaide, Dept. of Orthopaedics and Trauma, 1998

[Truncated abstract] Unicondylar knee arthroplasty (UKA) has re-emerged as a successful treatment option for isolated single compartment tibio-femoral joint osteoarthritis. However despite its increasing use, controversy still remains over fixed or mobile bearing tibial components, as there is a lack to prospective randomised studies reported in the literature. In addition, the theoretical advantages of the mobile bearing for knee kinematics, kinetics and clinical outcome have not been evaluated in vivo. The aim of this research study was to explore the clinical and biomechanical outcomes of the fixed and mobile bearing UKA. . . . When the results for the both studies were combined, utilising the Preservation and MG fixed bearing prostheses, there was a significant relationship between knee adduction moment, and a poor prognosis predicted from RSA. Those patients with translation or rotation of the tibial component in any direction above 1mm and 1.5 degrees respectively were considered to have a poor prognosis for long term fixation. Of the 28 patients, the 8 patients considered to have a poor prognosis, had increased knee adduction moments post-surgery (mean difference = 1.66Nm.kg-1, p = 0.007). There was no difference between the groups for knee flexion moment (mean difference 0.16Nm.kg-1, p = 0.844). Pre-surgery gait was unable to predict the post-surgery outcome, due to the significant changes in gait from pre- to post-surgery. Care must taken when implanting the Preservation mobile bearing prosthesis, as long term outcome is questionable. The mobile bearing prosthesis also produced the worst clinical outcome, however the theoretical advantages of the mobile bearing does not affect gait. Gait analysis is a useful tool to identify patient who are overloading their prosthesis, leading to potential early failure. Identification of these gait patterns can allow for early intervention to reduce joint load, and possible extend the longevity of the prosthesis.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis (Ph.D.)--University of Adelaide, Dept. of Orhtopaedics and Trauma, 1998. / Bibliography: leaves 198-219.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.