Principles of Evidence-Based Medicine




Evidence–based medicine integrates clinical expertise, patients’ values and preferences, and the best available evidence from the medical literature. Evidence–based orthopedics is a model to assist surgeons to improve the process of asking questions, obtaining relevant information efficiently, and making informed decisions with patients. With an increasing appreciation for higher levels of evidence, orthopedic surgeons should move away from lower forms of evidence. The adoption of randomized trials and high-quality prospective studies to guide patient care requires 2 prerequisites: (1) greater appreciation for the conduct of randomized trials in orthopedics and (2) improved education and training in evidence-based methodologies in surgery.


The origins of what is currently known as evidence-based medicine (EBM) go as far back as the seventeenth century, when it was observed that patients who received bleeding as part of their treatment of cholera had a much higher mortality rate than those who were not treated in the same manner. It has only been recently that EBM has seen an exponential increase in its adoption, and indeed the development of EBM has been heralded as one of the top medical milestones over the last 160 years. Although definitions vary, EBM integrates clinical expertise, patients’ values and preferences, and the best available evidence from the medical literature. In other words, as suggested by Sackett and colleagues, “Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.”


Historically, surgical decisions have largely been based on personal experience and recommendations from surgical authorities. In contrast to internal medicine, trials of surgical techniques and technologies have unique challenges and have, therefore, been slow to permeate the surgical literature. In addition, regulatory bodies have imposed less stringent controls on the validation of these technologies. As such, most surgical practice is based on lower levels of evidence. The proportion of systematic reviews and randomized controlled trials (RCTs) in leading surgical journals stands at 5%.


Regardless of the overall number of trials in surgery, it is extremely difficult for practicing surgeons to keep abreast of critical evidence, given the large number of surgical articles published monthly. Haynes stipulates that doctors need to read approximately 20 articles a day to keep up to date in their field.


Surgery is an exponentially growing specialty with 234 million operations performed globally in a year. Of these, 64 million are performed in the United States, and health care accounts for one-sixth of the economy. Furthermore, Internet-savvy patients who want the best in diagnostics and therapies demand evidence-based practice. The onus is on surgeons to provide high-quality evidence and institute best practices.


Evidence-based orthopedics


Current estimates suggest that less than 5% of the orthopedic literature represents randomized trials, although this has been steadily increasing. However, even the quality of reporting in RCTs is highly variable. Complete reporting of allocation concealment, details of blinding in follow-up, and surgical expertise in trial reports have been uncommon.


Although many orthopedic journals (eg, Journal of Bone and Joint Surgery , Clinical Orthopaedics and Related Research , Acta Orthopaedica , Journal of Orthopaedic Trauma , and Orthopedic Clinics of North America ) have adopted evidence-based approaches to reporting clinical research, there remain considerable opportunities to improve processes. Providing additional evidence-based resources and education for readers is a key first step.




Grading of evidence


The Oxford Center for Evidence Based Medicine has come up with a detailed hierarchy of evidence, as illustrated in Fig. 1 . The highest form of evidence remains a systematic review of homogeneous RCTs. A further step in grading of evidence is GRADE (Grades of Recommendation, Assessment, Development, and Evaluation). GRADE allows for a comprehensive, explicit, and transparent methodology for grading the quality of evidence and strength of recommendations about the management of patients.






Fig. 1


Levels of evidence.

From Oxford Centre for Evidence-Based Medicine. Available at: www.cebm.net/index.aspx?o=1025 . Accessed August 5, 2009; with permission.


Surgeons may believe that they are at risk of losing their autonomy with the proliferation of evidence-based guidelines. In today’s approach to using information, surgeons have to consider a change from a traditional paradigm of “this is how we have always done it” toward the application of current best evidence practices based on reliable and valid information sources. At the heart of EBM lies the amalgamation of individual clinical expertise, patient preferences, and best available evidence.




Grading of evidence


The Oxford Center for Evidence Based Medicine has come up with a detailed hierarchy of evidence, as illustrated in Fig. 1 . The highest form of evidence remains a systematic review of homogeneous RCTs. A further step in grading of evidence is GRADE (Grades of Recommendation, Assessment, Development, and Evaluation). GRADE allows for a comprehensive, explicit, and transparent methodology for grading the quality of evidence and strength of recommendations about the management of patients.






Fig. 1


Levels of evidence.

From Oxford Centre for Evidence-Based Medicine. Available at: www.cebm.net/index.aspx?o=1025 . Accessed August 5, 2009; with permission.


Surgeons may believe that they are at risk of losing their autonomy with the proliferation of evidence-based guidelines. In today’s approach to using information, surgeons have to consider a change from a traditional paradigm of “this is how we have always done it” toward the application of current best evidence practices based on reliable and valid information sources. At the heart of EBM lies the amalgamation of individual clinical expertise, patient preferences, and best available evidence.




Challenges of conducting RCTs in surgery


Proponents of EBM have always been cautious about the generalizability of results to a specific population or setting. Several problems in conducting RCTs in surgery have been reported. These problems include a general lack of knowledge, tendency to rigorously defend historically performed techniques, learning curve issues (seniority usually results in better outcomes), difficulty in blinding, and ethical considerations. One solution to overcome known biases in surgical trials is the expertise-based RCT. In this type of trial, a surgeon with expertise in one of the procedures being evaluated is paired with a surgeon with expertise in the other procedure who should ideally be from the same institution. Subjects are randomized to treatments and treated by a surgeon who is an “expert” in the procedure. This study overcomes some of the challenges associated with traditional orthopedic RCTs, including the caveat that surgeons who wish to participate in traditional RCTs must be willing to perform both techniques, and that a lack of expertise or belief in one of the interventions under evaluation may undermine the validity and applicability of the results. A recent survey of orthopedic surgeons found that most would consider this type of study design as it may decrease the likelihood of procedural crossovers and enhance validity because, unlike the conventional RCT, there is a low likelihood of differential expertise bias. Furthermore, positive steps are being made with the advent of larger multicenter trials in orthopedic surgery.




The value of observational studies when no RCTs exist


A significant proportion of the surgical literature finds its form as observational studies. It must be remembered that much of the research into the cause of diseases relies on cohort, case-control, or cross-sectional studies. Observational studies can generate significant hypotheses and have a role in delineating the harms and benefits of interventions. To ensure the robustness of reporting observational studies, the STROBE statement was created. The STROBE guidelines aim to assist investigators when writing up analytical observational studies, to support editors and reviewers when considering such articles for publication, and to help readers when critically appraising published articles.




Learning the “new” language of EBM


EBM practitioners do not have to become statisticians; however, they do need to understand key concepts and terminology to optimize their experiences.


Relative Risk, Odds Ratios, and Number Needed to Treat


If the end point of a study is binary or dichotomous, such as mortality or no mortality, then the odds ratio (OR) or relative risk or risk ratio (RR) can be calculated. The OR is the probability that a particular event will occur to the probability that it will not occur, and can be any number between zero and infinity. Risk describes the probability with which a health outcome (usually an adverse event) will occur. Measures of relative effect express the outcome in one group relative to that in the other. For treatments that increase the chances of events, the OR will be larger than the RR, so the tendency will be to misinterpret the findings in the form of an overestimation of treatment effect. OR is for case-controlled studies and RR is for cohort studies. Absolute measures, such as the absolute risk reduction or the number of patients needed to be treated (NNT) to prevent one event, are more helpful when applying results in clinical practice. The NNT can be calculated as 1/risk difference (RD).


Let us take the example shown in Table 1 , which is a hypothetical dataset from a cohort of patients who had cement inserted after hemiarthroplasty and who were compared with a matched sample of patients who did not have any cement inserted during hemiarthroplasty.


Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Principles of Evidence-Based Medicine
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