Determinants of patients' expectations about total knee arthroplasty outcomes

Knee osteoarthritis (OA) is the most prevalent form of arthritis in the US, affecting approximately 37% of adults. Approximately 300,000 total knee arthroplasty (TKA) procedures take place in the United States each year. Total knee arthroplasty is an elective procedure available to patients as an irreversible treatment after failure of previous medical treatments. Some patients sacrifice quality of life and endure many years of pain before making the decision to undergo total knee replacement. In making their decision, it is therefore imperative for patients to understand the procedure, risks and surgical outcomes to create realistic expectations and increase outcome satisfaction. ^ From 2004-2007, 236 OA patients who underwent TKA participated in the PEAKS (Patient Expectations About Knee Surgery) study, an observational longitudinal cohort study, completed baseline and 6 month follow-up questionnaires after the surgery. We performed a secondary data analysis of the PEAKS study to: (1) determine the specific presurgical patient characteristics associated with patients’ presurgical expectations of time to functional recovery; and (2) determine the association between presurgical expectations of time to functional recovery and postsurgical patient capabilities (6 months after TKA). We utilized the WOMAC to measure knee pain and function, the SF-36 to measure health-related quality of life, and the DASS and MOS-SSS to measure psychosocial quality of life variables. Expectation and capability measures were generated from panel of experts. A list of 10 activities was used for this analysis to measure functional expectations and postoperative functional capabilities. ^ The final cohort consisted of 236 individuals, was predominately White with 154 women and 82 men. The mean age was 65 years. Patients were optimistic about their time to functional recovery. Expectation time of being able to perform the list activities per patient had a median of less than 3 months. Patients who expected to be able to perform the functional activities by 3 months had better knee function, less pain and better overall health-related quality of life. Despite expectation differences, all patients showed significant improvement 6 months after surgery. Participant expectation of time to functional recovery was not an independent predictor of capability to perform functional activities at 6 months. Better presurgical patient characteristics were, however, associated with a higher likelihood of being able to perform all activities at 6 months. ^ This study gave us initial insight on the relationship between presurgical patient characteristics and their expectations of functional recovery after total knee replacement. Future studies clarifying the relationship between patient presurgical characteristics and postsurgical functional capabilities are needed.^

Making minimally invasive THR safe: conclusions from biomechanical simulation and analysis.

The use of smaller surgical incisions has become popularized for total hip arthroplasty (THR) because of the potential benefits of shorter recovery and improved cosmetic appearance. However, an increased incidence of serious complications has been reported. To minimize the risks of minimally invasive approaches to THR, we have developed an experimental approach which enables us to evaluate risk factors in these procedures through cadaveric simulations performed within the laboratory. During cadaveric hip replacement procedures performed via posterior and antero-lateral mini-incisions, pressures developed between the wound edges and the retractors were approximately double those recorded during conventional hip replacement using Charnley retractors (p < 0.01). In MIS procedures performed via the dual-incision approach, lack of direct visualisation of the proximal femur led to misalignment of broaches and implants with increased risk of cortical fracture during canal preparation and implant insertion. Cadaveric simulation of surgical procedures allows surgeons to measure variables affecting the technical success of surgery and to master new procedures without placing patients at risk.

Bayesian joint modeling of longitudinal and survival data

The joint modeling of longitudinal and survival data is a new approach to many applications such as HIV, cancer vaccine trials and quality of life studies. There are recent developments of the methodologies with respect to each of the components of the joint model as well as statistical processes that link them together. Among these, second order polynomial random effect models and linear mixed effects models are the most commonly used for the longitudinal trajectory function. In this study, we first relax the parametric constraints for polynomial random effect models by using Dirichlet process priors, then three longitudinal markers rather than only one marker are considered in one joint model. Second, we use a linear mixed effect model for the longitudinal process in a joint model analyzing the three markers. In this research these methods were applied to the Primary Biliary Cirrhosis sequential data, which were collected from a clinical trial of primary biliary cirrhosis (PBC) of the liver. This trial was conducted between 1974 and 1984 at the Mayo Clinic. The effects of three longitudinal markers (1) Total Serum Bilirubin, (2) Serum Albumin and (3) Serum Glutamic-Oxaloacetic transaminase (SGOT) on patients' survival were investigated. Proportion of treatment effect will also be studied using the proposed joint modeling approaches. ^ Based on the results, we conclude that the proposed modeling approaches yield better fit to the data and give less biased parameter estimates for these trajectory functions than previous methods. Model fit is also improved after considering three longitudinal markers instead of one marker only. The results from analysis of proportion of treatment effects from these joint models indicate same conclusion as that from the final model of Fleming and Harrington (1991), which is Bilirubin and Albumin together has stronger impact in predicting patients' survival and as a surrogate endpoints for treatment. ^

Joint effects of pulmonary function and aerobic power on survival in a cohort of healthy adults

Objective measurements of physical fitness and pulmonary function are related individually to long-term survival, both in healthy people and in those who are ill. These factors are furthermore known to be related to one another physiologically in people with pulmonary disease, because advanced pulmonary disease causes ventilatory limitation to exercise. Healthy people do not have ventilatory limitation to exercise, but rather have ventilatory reserve. The relationship between pulmonary function and exercise performance in healthy people is minimal. Exercise performance has been shown to modify the effect of pulmonary function on mortality in people with chronic obstructive pulmonary disease, but the relationship between these factors in healthy people has not been studied and is not known. The purpose of this study is to quantify the joint effects of pulmonary function and exercise performance as these bear on mortality in a cohort of healthy adults. This investigation is an historical cohort study over 20 years of follow-up of 29,624 adults who had complete preventive medicine, spirometry and treadmill stress examinations at the Cooper Clinic in Dallas, Texas.^ In 20 years of follow-up, there were 738 evaluable deaths. Forced expiratory volume in one second (FEV$\sb1$) percent of predicted, treadmill time in minutes percent of predicted, age, gender, body mass index, baseline smoking status, serum glucose and serum total cholesterol were all significant, independent predictors of mortality risk. There were no frank interactions, although age had an important increasing effect on the risk associated with smoking when other covariates were controlled for in a proportional-hazards model. There was no confounding effect of exercise performance on pulmonary function. In agreement with the pertinent literature on independent effects, each unit increase in FEV$\sb1$ percent predicted was associated with about eight tenths of a percent reduction in adjusted mortality rate. The concept of physiologic reserve is useful in interpretation of the findings. Since pulmonary function does not limit exercise tolerance in healthy adults, it is reasonable to expect that exercise tolerance would not modify the effect of pulmonary function on mortality. Epidemiologic techniques are useful for elucidating physiological correlates of mortality risk. ^