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

Thesis (M.A.)--Northern Kentucky University, 2009. / Made available through ProQuest. Publication number: AAT 1462163. ProQuest document ID: 1686693671. Includes bibliographical references (p. 41-45)

Thesis (Ph.D.)--Duquesne University, 2004. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 90-97) and index.

Thesis (M.E.)--University of Canterbury, 2005. / Typescript (photocopy). "August 2005." Includes bibliographical references (p. 107-115). Also available via the World Wide Web.

The history of total knee arthroplasty stretches back over 70 years. Many studies have shown that TKA is, in general, a successful operation for the relief of joint pain, with patient satisfaction rates of 90-95% and implant survival rates at 10-15 years of greater than 90%. However, a number of studies have also shown the potential for failures or complications arising post-implantation leading to revision surgery. This thesis presents finite element (FE) models of the distal femur following primary and revision total knee arthroplasty. Pre-arthroplasty models are also developed for comparison. Particular attention is given to how femoral component design and method of fixation impacts the mechanical environment of the distal femur and stability of the prosthesis. FE analyses with fully bonded interfaces indicate that femoral components are subject to areas of low stress (stress shielding) immediately under the anterior flange and chamfer regardless of internal implant features. However, internal implant features were found to play a role in the pattern and magnitude of stress concentrations. Both stresses and motions were observed to increase with increasing flexion angle, indicating the importance of testing at multiple angles. The initial models of the distal femur were extended to incorporate the effects of ageing and endosteal thinning of the femoral cortex, through novel application of pre-existing FE modelling techniques, specifically the ability to assign variable material properties corresponding to the nodal temperatures output from a heat transfer analysis. The findings from this study indicate that older patients with osteoporosis may be at increased risk of periprosthetic fracture compared to younger healthy patients. The use of a revision femoral component with a cemented stem as a means to mitigate this fracture risk was also investigated. FE analyses using frictional interfaces were employed to determine the influence of femoral component design on micromotion at the interface. These models showed that all primary implants were subject to similar magnitudes of relative motion at the interface, however, the distinct internal implant features led to very different regional variations. Furthermore, certain internal implant features (i.e. femoral box) were found to be highly sensitive to errors in surgical bone cuts. This aspect of the thesis also concluded that the addition of a stem served to significantly reduce motions at the interface in comparison to primary stemless implants. Long stemmed prostheses were found to result in the smallest levels of interface motion. This study also detailed the design and creation of an in vitro test setup for the purposes of determining the influence of stem length and fixation on the stability of revision prostheses. Experimental results using this test rig showed that a cemented short stem provides as much initial stability as the uncemented long stem, and is easier to fit surgically. Corresponding FE models incorporating a virtual representation of the test rig and in vitro loading conditions revealed that the relative motion at the multi-planar bone-prosthesis interface cannot be adequately described using a single reference point. However, in vitro setups may be used to predict a general measure of implant stability and to provide a source of calibration for FE. The distal femur models were further modified to investigate how the presence of condylar defects as classified by AORI defect classification system (Engh 2006) and weak osseous support due to osteoporosis may adversely affect the survival of the prosthesis. These investigations revealed that fixation of the femoral component, the presence of a large condylar defect and the level of osseous support all had an impact on stress in the implant, it is concluded that a non-modular approach should be adopted in older patient groups with severe osteoporosis to mitigate the risk of component junction failure and distal femoral fracture.

It has been noticed that the need for total knee replacement surgery is increasing for Asian region. A total knee replacement is a permanent surgical solution for a patient having debilitating pain in knee joint suffering from arthritis. In this surgery, knee joint is replaced with components made up of bio-compatible materials after which the patient can resume the normal day to day activities. Western population has bigger build compared to Asian population. Most of the total knee replacement prosthesis are designed for western population. When these total knee prosthesis are used for Asian population, they cause a mismatch leading to various clinical complications such as reduced range of motion and pain. The studies have been limited to clinical complications caused by the mismatch. To address this limitation, current study is aimed to find the mechanical implications such as stress distribution, maximum stresses, maximum displacements etc., caused by mismatch of total knee replacement components with knee. A surgeon selects total knee components for a patient based on some critical dimensions of femur and tibia bone of knee. In addition, a method to accurately calculate these dimensions of the femur and tibia bone of a real knee was developed in the current study. This method calculated the points of curvature greater than a threshold (decided based on the radius of the curvature) found out using the formula of curvature. Further, the highest point was calculated based on maximum height from a line drawn between initial and final point within the captured points, also the extreme points were calculated based on the sign change in slope of points within the captured points, giving multiple points on the boundary of bones extracted in an MRI image of a patient. The distance between two selected farthest points, out of these points, in specific direction was the basis for selection of the TKR components. Total knee replacement components were modeled in Geomatics Studio 12 software, bones were modeled in Rhinoceros 5 software, assembly of bones and total knee replacements components was done in Solid works 2013 software, the finite element model of the assembly was developed in Hyper mesh 11 software and, the stress analysis and post processing was done in ABAQUS 6.13 software. A static, implicit non linear analysis was performed. Simulations were performed for two conditions: at standing (0o of flexion) and at hyper-flexed (120o of flexion). In order to figure out if there were any mechanical implications of mismatch, the full model of assembly consisting of femur, tibia and fibula bones assembled with total knee replacement components, and the reduced model consisting of only total knee replacement components were simulated separately, results of which have been discussed in the current thesis. In this work, the effect of change of length of ligaments at 120o of flexion in detail was also studied. This study brought out various outcomes of contact mechanics and kinematics between the components of total knee replacement prosthesis.

No description available.

Robotic assisted partial knee arthroplasty (PKA) has gained in popularity as a treatment for end stage knee osteoarthritis (OA) that involves only one or two compartments of the knee over total knee arthroplasty (TKA). PKA surgeries are known for their less invasive and more precise treatment of medial or lateral compartmental (+/- patellofemoral) arthritis, improved postoperative range of motion, greater ligament and bone preservation, and a more natural gait. The Robotic Arm Interactive Orthopedic MAKO Stryker (RIO; MAKO Stryker, Fort Lauderdale, Florida) Robot has significantly improved PKA implant alignment by providing real-time feedback during surgery and improving three-dimensional implant placement accuracy. To assess kinematic differences between robotic assisted PKA and manual technique TKA, a 14-camera optoelectronic motion capture system (Optitrack, NaturalPoint, Corvallis, OR USA) was designed and installed in a hospital hallway to collect patient gait outcomes directly after clinic appointments. This thesis investigates the feasibility and validity results from setting up a motion capture system and its associated reliability when using it in a high traffic clinical environment. The first objective of this thesis was to investigate a total of 26 patients (14 TKA, 12 PKA) that underwent a kinematic gait assessment at 4-time points; preoperatively, and postoperatively (3,6,12 months). At 3 and 6 months postoperatively, the TKA group had improved knee flexion range of motion (ROM) during walking compared to the PKA group. This result was statistically significant (3-month p value =0.042, 6-month p value= 0.048). At 6 months, changes in the knee adduction/abduction angles were also significantly different (p value= 0.023), showing less knee ROM in the frontal plane after a PKA comparable to healthy controls. Despite differences in improvements in joint kinematics during walking between the two groups, these factors did not necessarily correlate with better perceived patient reported outcomes (PROMs). The results obtained from this pilot study display initial feasibility and suggest further research is required on a larger sample size to confirm if PKA surgeries are superior to TKA surgeries in terms of gait function. In conclusion, a repeatable, instrumented gait analysis was setup in a busy orthopedic hallway where reliable data can be collected. / Thesis / Master of Applied Science (MASc) / Robotic assisted partial knee replacements have been gaining popularity in recent years due to the perceived benefits over a total knee replacement such as preserving more bone, faster recovery, and improved walking outcomes. A partial knee replacement can either replace one or both compartments of the knee joint, depending on the level of arthritis in the patient's knee. This thesis investigated the differences in walking ability before and after surgery using a specialized system installed in the hospital to collect data during regularly scheduled appointments. Patients in this study either received a partial knee replacement with the help of a surgical robot, or a regular total knee replacement. The results showed that there is a significant difference in how much the knee moves during walking between patients who had the robot surgery and those who had the usual surgery. However, the patient’s experience and their perception of how well they were doing after surgery were not different between the two surgeries. This study provided valuable insight into the current surgical treatments available for knee arthritis.

Increased workload on our healthcare system calls for more automation, this too in the pre-operative planning of total knee arthroplasty (TKA) surgery. This should keep in mind however that success in TKA is measured through having proper limb alignment. This thesis project implemented a virtual positioning assessment software that provides an initial position based on its bone and implant inputs with their specific landmarks. Positions can be furtherly adapted and evaluated based on flexion facets, obtaining decreased pre-operative workloads. The software was validated through an analysis comparison of the femur positioning of nine cases with the former used analysis tool of the university Hospital of Ghent. The newly implemented software was concluded to approximate the patients’ pre-operative alignment better for all translational and rotational parameters, except anteroposterior translation and internal/external rotation of the femur.

Knee osteoarthritis (OA) is a progressive disease that ultimately requires patients to receive a total knee arthroplasty (TKA) to replace the damaged structures within the knee with an artificial joint. Surgeons have many options when selecting an appropriate implant. Patients want a TKA that feels 'normal' and allows them to perform most activities without pain, stiffness, and other residual symptoms. However, 20% of patients remain unsatisfied with their surgery, regardless. This thesis aimed to examine the effect of implant selection during TKA on knee biomechanical function during various ADLs. Several gaps were identified within the review of literature: 1) patient-reported outcome measures cannot differentiate between medial ball and socket (MBS) and posterior stabilized (PS) implants, 2) most biomechanical studies were performed only in postoperative patients, and 3) studies that compared MBS and PS implants were primarily focused on level walking conditions, and overlooked tasks that placed more demand on the knee joint. Twenty-eight individuals with severe knee OA were randomized to receive either an MBS (n=14) or PS implant. They completed a biomechanical assessment within one month and one year after TKA and were compared to 14 controls of similar age, sex, and body mass index. They performed a variety of tasks which explored three main areas: 1) examine the alterations in gait variability among individuals with OA following a TKA procedure using either a PS or MBS implant; 2) enhance the understanding of the post-operative effects of TKA with either MBS and PS implants on knee biomechanics and muscle activities during level walking, as well as more demanding tasks such as descending a ramp or staircase; 3) simulate the dynamic knee joint loads in post-operative TKA patients with either PS or MBS implants during closed-chain, bilateral tasks such as sit-to-stand. Initially, a series of studies were performed to develop a new test called waveform-level variance inequality test (eqvartest), which had not been previously utilized in the literature. This test was used to identify discrepancies in gait variability pre and post-TKA in the gait cycle. Following TKA, patients showed decreased variability in knee moment and power at single-limb support. Neither the MBS nor PS implant provided the same level of variability as the control group, demonstrating reduced knee joint stability. The MBS group had a gait pattern closer to the control group during level walking, whereas the PS group walked with a stiffer knee. However, during more demanding ADLs, the differences were less apparent. During ramp descent, knee joint stability issues became prominent as MBS and PS groups adopted a 'cautious gait pattern,' widening their base of support and stiffening their knee to reduce loading. During stair descent, the MBS implant provided increased stability as it required less muscle activity than the PS, requiring greater hamstring muscle activation. During sit-to-stand, MBS and PS groups favoured their non-operated knee as they had reduced total vertical, medial, and lateral KCF on their operated knee compared to their non-operated side. This may be due to compensatory strategies developed through the progression of knee OA and may increase the risk of developing knee OA on the non-operated limb. The outcomes of this thesis can assist clinicians in selecting the most appropriate implant for their patients and guide them in designing rehabilitation programs that can enhance patient function following TKA.