Thesis (M. Med. Sc.)--University of Hong Kong, 2004. / Also available in print.

With the increasing advocacy for maintaining a healthy lifestyle in regards to exercise and the average age of the population in the U.S. growing older, there has been an increased incidence of arthritic knee damage as a result of osteoarthritis. Once non-procedural methods of treatment have been exhausted, such as NSAIDs and physical therapy, the most effective therapy to regain previous range of motion and quality of life is total knee arthroplasty (TKA). Additionally, TKA is useful to treat patients with rheumatoid disease once their knees have reached end-stage cartilage damage, although it does not restore function as well in these patients as it does in patients with osteoarthritis. Current technological developments have produced prostheses that mimic physiological movement and allow attachment of components positioned similarly to ligaments in the human knee, providing better longevity and functional recovery from the damaged state. The TKA procedure has become fast-tracked to limit the length of stay for patients and the cost to both the individual and the hospital. Though this change to fast-track procedures has helped limit post-operative complications, such as venous thromboembolism, multiple comorbidities and componentry failure continue to increase the risk of failure or revision of the procedure. With the projected increase in the need for TKAs in the future, it is important to review factors that may influence access and success of this procedure, for example, the effect socioeconomic status has on the ability of different patients to receive quality replacements and experience sustained quality of life. Multiple studies have shown that utilization of TKA differs between low income and high income populations, with racial minority populations undergoing the procedure less often as they represent a greater percentage of low income populations. Interestingly, low income patients report greater improvement in function when compared to high income patients, most likely due to low income patients being admitted with more severe knee damage when compared to the other population. Their satisfaction, along with financial constraints and insurance, are factors that lower the rate of revision for low income populations even though their measured range of motion post-operatively is not as good as that in high income populations on average. Social support has been determined to be a significant factor in determining whether patients will undergo TKA and follow the rehabilitation prescribed to them appropriately. Studies have shown less social support reported from minority groups, but not low income cohorts specifically. Using the current knowledge of the impact these differences in socioeconomic status can have on the outcomes of TKA, can help create healthcare environments which will optimize the success rate of TKA for all patients, regardless of socioeconomic status, and prevent unnecessary strain on the healthcare system due to avoidable post-operative issues. Future studies should determine what policies and procedures can be implemented to help aid patients, such as greater social support, and to support hospitals with limited resources in an effort to improve surgical outcomes.

This thesis is missing pages 98-107, all of which are not in the other copies of the thesis. -Digitization Centre / In total knee arthroplasty with bone defect of the tibia, it was believed that with older designs of tibial tray, both block and stem augments must be used with the tibial tray to improve the knee stability. Obviously, the extended stem causes more difficulties to the surgery as well as more suffering to the patients. Getting rid of the extended stem and still maintaining enough stability is therefore very desirable. The newest tray design, Deltafit Keel tray, which provides much more contact with the human bone structure, may provide enough stability without the extra long stem. The objective in this project is to answer the questions - Is the stem augmentation definitely required alongside the block implant for the cases of bone defect in TKA (Total Knee Arthroplasty) when using the Deltafit Keel tibial tray design? In other words, does the configuration of Deltafit Keel tray with a block provide enough stability in the cases of bone defect? In order to give a reliable answer, three configurations have been studied by conducting both experiments and FEA simulation. The three cases are Deltafit Keel tibial tray only (case 1-no bone defect defect), tray with block augment (case 2-with bone defect assumed) and tray with block and extended stem (case 3-with bone defect assumed). In this study, three commercially available composite bones with isotropic material properties are utilized. For each configuration, the bones are clamped in a testing apparatus and 3000 N static compressive load is imposed on the top surface of the tibia tray at central, medial and lateral locations. In experiment, the strains and displacements at strategically selected locations were measured by strain rosettes (strain gages) and DVRT (Differential Variable Reluctance Transducer) displacement transducers, respectively. In order to simulate the three cases, FE model is established by employing several advanced software including CATIA, True Grid Mesh generator and Abaqus. In order to compare with the experimental results, nine cases (three implant configurations with three different loading positions for each) have been simulated using Abaqus/Standard 6.4. In addition to the nine-case studies, the influence of load offsetting is also investigated by shifting the nodal load along medial-lateral and anterior-posterior directions. It is found that load shifting one node in either direction does not cause significant change in either strain or displacement. Furthermore, FE results of adjacent elements are checked as well and no sudden changes are observed. Since the discrepancy of the output from adjacent elements is negligible, an average value of the elements can be used to represent the output in a small region to compare the experimental strain measured by strain rosettes. Both the experimental data and FEA simulation results lead to the conclusion that comparable stability can be achieved with the configuration of Deltafit Keel tibial tray and a block as compared to the case of Deltafit Keel tray only without bone defect. Moderate improvement of stability, but with significant stress shielding, is found when the extended stem is implanted. For the amount of bone defect and the bone material properties used in this study, the Deltafit Keel tray with a block is the best choice because it is able to provide adequate stability and avoid excessive stress shielding. The loss of a substantial amount of bone to implant an extended stem to trade for the excessive stability may not be worthwhile. Besides, stress shielding is a potential problem which may exist if the extended stem is used. / Thesis / Master of Applied Science (MASc)

Introduction: Studies show that Total Knee Arthroplasty (TKA) is successful for the majority of patients however some continue to experience some functional limitations and anecdotal evidence indicates that stiffness is a common complaint. Some studies have suggested an association between stiffness and functional limitations however there has been no previous work which has attempted to objectively quantify knee joint stiffness following TKA. The purpose of this study was to pilot and evaluate a method for the quantitative evaluation in joint stiffness in replaced knees, OA knees and healthy controls and to explore whether there is an association between stiffness and functional limitations post-TKA surgery. Methods: The first part of the study created a biomechanical model of knee stiffness and built a system from which stiffness could be calculated. A torque transducer was used to measure the resistance as the knee was flexed and extended passively and an electrogoniometer concurrently measured the angular displacement. Stiffness was calculated from the slope of the line relating the passive resistive torque and displacement. The torque and joint angle at which stiffness was seen to increase greatly was also noted. The system was bench tested and found to be reliable and valid. Further tests on 6 volunteers found stiffness calculations to have acceptable intra-day reliability. The second part was conducted on three groups: those with end-stage knee OA (n = 8); those who were 1 year post-TKA (n = 15) and age matched healthy controls (n = 12). Knee range of motion was recorded and participants then completed the WOMAC, the SF-12 and a Visual Analogue Score for stiffness as well as indicating words to describe their stiffness. Four performance based tests – the Timed Up and Go (TUG), the stair ascent/descent, the 13m walk and a quadriceps strength test were also undertaken. Finally, passive stiffness at the affected knee was measured. Results: 100% of OA, 80% of TKA and 58% of controls reported some stiffness at the knee. The OA group reported significantly higher stiffness than the OA or TKA groups. There was no difference in self-reported stiffness between the TKA and control groups. Of the total number of words used to describe stiffness, 52% related to difficulty with movement, 35% were pain related and 13% related to sensations. No significantly differences were found between groups in the objective stiffness measures. Significant differences were found however in threshold flexion stiffness angles between groups. When this angle was normalised, differences between groups were not significant. No significant differences were found between groups in the threshold stiffness torque. Greater self-reported stiffness was found to be associated with worse self-reported function. A higher flexion stiffness threshold angle was associated with slower timed tests of function but also with better quadriceps muscle strength. Conclusions: The results support anecdotal reports that perceived stiffness is a common complaint following TKA but there was no evidence to show that patients with TKA have greater stiffness than a control group. There was however evidence to show that patients’ were unable to distinguish between sensations of stiffness and other factors such as pain. Self-perceived increased stiffness was associated with worse functional performance. Greater stiffness however was not necessarily negative. Stiffness increases earlier in flexion range were associated with better functional performance. These results suggest that an ideal threshold range for stiffness may exist; above which negative perceptions of the knee result in worse function but below which, knee laxity and instability may also result in worse function.

Osteoarthritis (OA) is one of the leading causes of global disability. Surgical intervention in the form of Total Knee Arthroplasty (TKA) has been established as an excellent treatment modality for people with OA who experience joint symptoms that have a substantial impact on their quality of life and are refractory to non-surgical treatment. In the 1970s the concept of implanting TKAs in mechanical alignment (MA) was developed as a compromise to confer mechanical advantage to the prosthesis, ignoring the patient's natural anatomy, to prevent early failure of the implant. Until now, this compromise has not been revisited. Satisfaction following TKA remains inferior to total hip arthroplasty. The cause of this dissatisfaction is not clear. Implant survival is no longer comparable to that of the early designs of TKA, and recent studies have suggested that deviation from neutral alignment does not have the detrimental effect on survivorship as previously thought. In an attempt to improve patient satisfaction following TKA a new technique has been developed whereby the prostheses are implanted in such a way as to recreate the alignment of the knee in the patient's pre-arthritic state. This has been termed natural or kinematic alignment (KA). This thesis examines the impact of KA in TKA with the primary hypothesis that TKA performed utilising KA would lead to improved functional outcome following surgery compared to that of MA. An initial single surgeon proof of concept case series of 25 patients was performed to look at the precision of new patient specific cutting blocks. The results suggested that the cutting blocks were accurate in producing the desired cuts. Following the proof of concept case series, a feasibility study was then performed comparing the new KA technique with the standard MA technique. The feasibility study familiarised the operating surgeons with the new technology in preparation for a Randomised Control Trial (RCT). A prospective blinded RCT was performed to compare the functional outcome of patients implanted with TKA in MA with that of KA. A total of 71 patients undergoing TKA were randomised to either MA (n=35) or KA (n=36). Preand post-operative hip knee ankle (HKA) radiographs were analysed. A number of patient reported outcome measures and functional tests were assessed pre-operatively, 6 weeks, 3 months, 6 months, and at 1 year post-operation. The cutting guides were accurate. There were no statistically significant differences between the MA and KA groups at 1 year. A cohort of post-menopausal women with unilateral osteoarthritis treated with TKA utilising the KA philosophy had dual energy x-ray absorptiometry scans 1.5 years post-operatively using a modified validated densitometric analysis protocol, to assess peri-prosthetic Bone Mineral Density (BMD). The contralateral knee was scanned so that relative bone mineral density could be calculated. Statistical analysis revealed no significant difference in relative peri-prosthetic bone mineral density due to variation in implant position with respect to the Lateral Distal Femoral Angle (LDFA) and the Medial Proximal Tibial Angle (MPTA). There was a significant correlation with overall HKA angle and the relative BMD under the medial side of the tibial tray. KA TKAs appear to have comparable short-term results to MA TKAs with no significant differences in function 1 year post-operatively. Overall HKA angle rather than the individual component position caused change in relative BMD under the tibial tray, therefore aiming for an anatomical joint line may improve kinematics without a detrimental effect on the implant. Further research is required to see if any theoretical long-term functional benefits of KA are realised or if there are any potential effects on implant survival.

After Total Knee Arthroplasty, contact stresses at the surface and stresses at the implant-cement-bone interface are directly related to the joint contact forces. These stresses are a major factor in wear and fatigue, aseptic loosening, stress shielding and osteoporosis. Implant contact stresses influence the wear and fatigue damage of the Ultra High Molecular Weight Polyethylene (UHMWPE) articulating surface, decreasing the longevity of the implant. The contact stresses are influenced by the kinematics, the bearing congruency of the articulating surfaces and insert thickness. Thus, various studies have focused on the prediction and optimization of kinematics at the joint interface, contact areas, and stresses in different knee implant designs. As a result, the successful total knee replacement designs depend on joint kinematics and the contact stresses. The objective of this study was to perform contact stress analysis on a newly designed surface guided knee implant, in order to evaluate the design with respect to the potential of polyethylene wear. In order to test the performance of this design, Finite Element Modeling (FEM) was used as a good medium to analyze the design’s specifications, and to evaluate the results of the stress analysis of the design. For validation and also comparison with previous studies, results of this study were compared with those of related work with similar loading and constraints. Based on the gathered data from FE analysis of the design, it can be concluded that the new surface guided knee implant shows lower peak contact pressure than other previously evaluated implants. / October 2015

Total knee arthroplasty (TKA) is a common surgical procedure for the treatment of patients with pain and immobility as a result of osteoarthritis or rheumatoid arthritis. Pain-related interference, pain and nausea are recovery-limiting in these patients in the immediate postoperative period. Preoperative educational interventions that include pain communication and management information have been shown to decrease pain in joint replacement patients (McDonald & Molony, 2004). This randomized controlled trial compared usual preoperative education to an individually delivered preoperative education program. Participants (N=143) were randomized to intervention or usual care groups during routine preadmission testing. The usual care group received the usual preoperative teaching. The treatment group received the usual care teaching, a booklet containing content specific to symptom management after TKA, an individual teaching session during the preadmission testing visit and a telephone follow-up support call during the week before surgery. The primary outcome for this study was pain-related interference with activity and was measured using the Brief Pain Inventory Interference subscale (BPI-I) (Cleeland et al., 1994) on postoperative day three. Secondary outcomes were pain, nausea and expected postoperative activity and were measured on postoperative days one, two and three. There were no differences between groups in any of the outcomes for this study. BPI-I total scores were 24.4±14.4 in the intervention group and 22.4±15.1 in the usual care group (P=0.5) on the third postoperative day. Overall results demonstrated that although TKA patients had severe postoperative pain and severe nausea, they received inadequate doses of analgesia and anti-emetics. Available evidenced based protocols and practices in the health care environment were not followed Individualizing education content was not sufficient to produce a change in postoperative symptoms for these patients. Further research involving the modification of environmental and system factors affecting the provision of symptom management interventions is warranted.

Total knee arthroplasty (TKA) is a common surgical procedure for the treatment of patients with pain and immobility as a result of osteoarthritis or rheumatoid arthritis. Pain-related interference, pain and nausea are recovery-limiting in these patients in the immediate postoperative period. Preoperative educational interventions that include pain communication and management information have been shown to decrease pain in joint replacement patients (McDonald & Molony, 2004). This randomized controlled trial compared usual preoperative education to an individually delivered preoperative education program. Participants (N=143) were randomized to intervention or usual care groups during routine preadmission testing. The usual care group received the usual preoperative teaching. The treatment group received the usual care teaching, a booklet containing content specific to symptom management after TKA, an individual teaching session during the preadmission testing visit and a telephone follow-up support call during the week before surgery. The primary outcome for this study was pain-related interference with activity and was measured using the Brief Pain Inventory Interference subscale (BPI-I) (Cleeland et al., 1994) on postoperative day three. Secondary outcomes were pain, nausea and expected postoperative activity and were measured on postoperative days one, two and three. There were no differences between groups in any of the outcomes for this study. BPI-I total scores were 24.4±14.4 in the intervention group and 22.4±15.1 in the usual care group (P=0.5) on the third postoperative day. Overall results demonstrated that although TKA patients had severe postoperative pain and severe nausea, they received inadequate doses of analgesia and anti-emetics. Available evidenced based protocols and practices in the health care environment were not followed Individualizing education content was not sufficient to produce a change in postoperative symptoms for these patients. Further research involving the modification of environmental and system factors affecting the provision of symptom management interventions is warranted.

Knee osteoarthritis is a debilitating disease causing pain and disability in adults. Biomechanical factors including obesity, abnormal magnitude and load distribution have been cited to play a role in its initiation and progression with its definite cause being multi-factorial. Total knee arthroplasty has become the treatment of choice for knee osteoarthritis and although the procedure is mostly successful, there are some patients who experience implant failures which necessitates revision surgery. Revision surgery is more complicated and thus there is the need to monitor patients who have undergone TKA so as ensure better outcomes and also address problems much earlier. Objective methods like Radiostereometric Analysis (RSA) has proven to be a good tool at diagnosing these implant failures. Inducible displacement with RSA has the potential to serve as a one-time measure to diagnose implant failures. Previous studies have applied loads to induce motion to the knee in various ways- squatting, exercising and weight-bearing on the affected limb. This was not standardized and caused wide variations in the data. This work looked at refining a device used to apply standardized loads to the knee resulting in a more portable and faster way of applying load to the joint. Gait analysis is used to assess implant function pre and post surgery. Some gait patterns have also been related to implant failure. Previous works have focussed primarily on associations between well-working implants (non-revised patients) and these gait patterns (adduction moments and flexion angles). This work focussed on any differences in the gait patterns between patients who did not undergo revision surgery and those that did. Although most parameter differences did not reach statistical differences, they point to important trends that may explain the causative factors (adduction moments) whiles others may point to the effects of disease progression (external rotation).

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted. Includes bibliographical references.