Why the P-value culture is bad and confidence intervals a better alternative.

In spite of frequent discussions of misuse and misunderstanding of probability values (P-values) they still appear in most scientific publications, and the disadvantages of erroneous and simplistic P-value interpretations grow with the number of scientific publications. Osteoarthritis and Cartilage prefer confidence intervals. This is a brief discussion of problems surrounding P-values and confidence intervals

Statistical analysis of arthroplasty register data

Data from arthroplasty registers are often analyzed using survival methods. Several methodological problems exist, for example relating to competing events, non-random censoring, non-proportional hazards and dependent observations. League tables and ranking of specific survival results leds to further methodological difficulties. Most of these problems are, however, well known and a number of methods for dealing successfully with the problems have been developed. These methods are usually accessible in commercially available statistical software packages

Xenotransplantation public perceptions: rather cells than organs.

The aim of this study was to describe some of the factors that might play a role in influencing attitude to xenotransplantation: first, the consideration of receiving cells and tissue from xenotransplants in relation to whole xeno-organs; secondly, the fact that there is greater uncertainty regarding the result and risk of infection associated with xenotransplantation than with allotransplantation. We also describe the attitude to research on xenotransplantation, and the relationship between the attitude to receiving a xenotransplant and an allotransplant. Finally, we describe the attitude to xenotransplantation in relation to treatment for renal failure and waiting-time for allotransplantation. A questionnaire was sent to randomly selected members of the public aged 18 to 75 (n=1000) and to all patients in the same age range who were waiting for kidney transplants in Sweden in the spring of 1998 (n=460). The response rate was 60% among the public and 87% among the patients. Both study groups were positive to a greater extent in their attitude to receiving cells and tissue than to receiving a whole organ such as a kidney. The response `rather positive' to receiving organs was generally favored by the public, whereas the most generally favored response to receiving cells and tissue was `very positive'. When there was suggested to be a greater uncertainty regarding the outcome with xenotransplantation compared with allotransplantation, the number of negative and uncertain respondents increased, both among the public and the patients. Eighty percent of the public and about 90% of the patients were in favor of continued research on xenotransplantation. Of those members of the public who responded, the attitude to receiving an organ from a human was positive in 86% of cases, with an emphasis on `very positive'. There was a moderate relation between the attitude to receiving an organ from a human and to receiving a xenotransplant. Among the patients, there was no systematic or strong relation between the attitude to xenotransplantation and the kind of dialysis treatment they were on. Neither was there any systematic or strong relation to the waiting-time. The overall impression is that the attitude to xenotransplantation seems to be most influenced by whether the xenotransplant would involve whole organs or cells and uncertainty regarding the outcome

The Swedish Knee Arthroplasty Register: a review.

We are entering a new era with governmental bodies taking an increasingly guiding role, gaining control of registries, demanding direct access with release of open public information for quality comparisons between hospitals. This review is written by physicians and scientists who have worked with the Swedish Knee Arthroplasty Register (SKAR) periodically since it began. It reviews the history of the register and describes the methods used and lessons learned. Cite this article: Bone Joint Res 2014;3:217-22

Metal-on-metal joint bearings and hematopoetic malignancy.

To access publisher's full text version of this article. Please click on the hyperlink in Additional Links field.This is a review of the hip arthroplasty era. We concentrate on new metal bearings, surface replacements, and the lessons not learned, and we highlight recent reports on malignancies and joint implants. A low incidence of blood malignancies has been found in bone marrow taken at prosthetic surgery. The incidence is increased after replacement with knee implants that release very low systemic levels of metal ions. A carcinogenic effect of the high levels of metal ions released by large metal-on-metal implants cannot be excluded. Ongoing Swedish implant registry studies going back to 1975 can serve as a basis for evaluation of this risk.Swedish Association of Local Authorities and Regions Faculty of Medicine, Lund University Stiftelsen for Bistand at Rorelsehindrade i Skane Region Skan

A randomized trial of balloon kyphoplasty and nonsurgical management for treating acute vertebral compression fractures: vertebral body kyphosis correction and surgical parameters.

Objective. To compare the efficacy and safety of balloon kyphoplasty (BKP) with nonsurgical management (NSM) during 24 months in patients with painful vertebral compression fractures (VCFs). Summary of Background Data. Recently, several large randomized controlled trials have been conducted and reported how vertebral augmentation compares with NSM for patients with acute VCFs. Few of these trials report on the surgical aspects and radiographical vertebral deformity results. Methods. Adults with 1 to 3 VCFs were randomized within 3 months of pain to undergo bilateral BKP (n = 149) or NSM (n = 151). Surgical parameters, subjective quality of life assessments and objective functional (timed up and go) and radiographical assessments were collected. Results. Compared with NSM, the BKP group had greater improvements in SF-36 physical component summary (PCS) scores at 1 month (5.35 points; 95% CI, 3.41 - 7.30; P < 0.0001) and when averaged across the 24 months (overall treatment effect 2.71 points; 95% CI, 1.34-4.09; P = 0.0001). The kyphoplasty group also had greater functionality by assessing timed up and go (overall treatment effect - 2.49 s; 95% CI, - 0.82 to - 4.15; P = 0.0036). At 24 months, the change in index fracture kyphotic angulation was statistically significantly improved in the kyphoplasty group (average 3.13° of correction for kyphoplasty compared with 0.82° in the control, P = 0.003). Number of baseline prevalent fractures (P = 0.0003) and treatment assignment (P = 0.004) are the most predictive variables for PCS improvement; however, in patients who underwent BKP, there may also be a link with kyphotic angulation. In BKP, the highest quart for kyphotic angulation correction had higher PCS improvement (13.4 points) than the quart having lowest correction of angulation (7.40 points, P = 0.0146 for difference). The most common adverse events temporally related to surgery (i.e., within 30 d) were back pain (20 BKP, 11 NSM) new VCF (11 BKP, 7 NSM), nausea/vomiting (12 BKP, 4 NSM), and urinary tract infection (10 BKP, 3 NSM). Several other adverse events were possibly related to patient positioning in the operating room. Conclusion. Compared with NSM, BKP improves patient quality of life and pain averaged during 24 months and results in better improvement of index vertebral body kyphotic angulation. Perioperative complications may be reduced with more care in patient positioning

ArthroplastyWatch.com three-year follow-up: where do we stand now?

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No bias of ignored bilaterality when analysing the revision risk of knee prostheses: Analysis of a population based sample of 44,590 patients with 55,298 knee prostheses from the national Swedish Knee Arthroplasty Register

BACKGROUND: The current practice of the Swedish Knee Register is not to take into consideration if one or both knees in a patient are subject to surgery when evaluating risk of revision after arthroplasty. Risk calculations are typically done by statistical methods, such as Kaplan-Meier analyses and Cox's proportional hazards models, that are based on the assumption that observed events are independent, and this is rarely appreciated. The purpose of this study was to investigate if ignoring bilateral operations when using these methods biases the results. METHODS: The bias of not taking bilateral operations into account was investigated by statistically analysing 55 298 prostheses in 44 590 patients, undergoing knee arthroplasty surgery in Sweden during 1985–1999, using traditional proportional hazards analysis, which assumes that all observations are independent, and a shared gamma frailty model, which allows patients to contribute repeated observations. RESULTS: The effect of neglecting bilateral prostheses is minute, possibly because bilateral prosthesis failure is a rare event. CONCLUSION: We conclude that the revision risk of knee prostheses in general can be analysed without consideration for subject dependency, at least in study populations with a relatively low proportion of subjects having experienced bilateral revisions