Residency · Residency · Oral Maxillofacial Surgery

Evidence-Based Practice and Critical Appraisal in OMFS

Introduction

Evidence-based practice (EBP) integrates the best available research evidence with clinical expertise and patient values to guide decision-making. As OMFS continues to evolve, the ability to critically appraise the literature and apply findings to clinical practice is an essential competency for every resident and practitioner. This lecture provides a framework for evaluating the surgical literature and implementing evidence-based approaches in OMFS.

The Three Pillars of Evidence-Based Practice

Evidence-based practice rests on three pillars. The first is the best available research evidence, drawn from systematic reviews, randomized controlled trials, and cohort studies. The second is clinical expertise, representing the surgeon's accumulated knowledge, skills, and judgment. The third is patient values and preferences, encompassing individual patient circumstances, concerns, and informed choices. EBP does not replace clinical judgment but rather provides a framework for integrating evidence into decision-making.

Levels of Evidence

Oxford Centre for Evidence-Based Medicine Hierarchy

Grades of Recommendation

Grades of recommendation correspond to the quality of supporting evidence. Grade A represents a strong recommendation based on consistent Level I evidence. Grade B is a moderate recommendation based on consistent Level II to III evidence. Grade C is a weak recommendation supported by Level IV evidence. Grade D is a very weak recommendation based on Level V evidence or inconsistent and inconclusive evidence.

Reality in OMFS Literature

The majority of OMFS literature consists of Level III to IV evidence, primarily retrospective studies and case series. RCTs are difficult to conduct in surgery due to ethical constraints, blinding challenges, and small patient populations. Systematic reviews and meta-analyses are increasing but are limited by the quality of included studies. The surgeon must frequently make decisions even when Level I evidence is unavailable.

Formulating Clinical Questions

PICO Framework

The PICO framework structures clinical questions into four components. P (Patient/Population) defines who the patient or patient group is. I (Intervention) specifies the intervention, treatment, or exposure being considered. C (Comparison) identifies the alternative, whether another treatment, placebo, or no treatment. O (Outcome) describes the desired measurable outcome.

Example PICO Questions in OMFS

A well-formed PICO question might ask: In patients with impacted third molars (P), does prophylactic antibiotics (I) compared to no antibiotics (C) reduce the incidence of postoperative infection (O)? Another example: In patients with mandibular angle fractures (P), does one miniplate on the tension band (I) compared to two miniplates (C) result in equivalent fracture stability and complication rates (O)?

Searching the Literature

Key Databases

PubMed/MEDLINE is the primary biomedical database with free access and MeSH headings for structured searches. The Cochrane Library provides systematic reviews and meta-analyses representing the highest quality of evidence synthesis. Embase has a European focus and is complementary to PubMed for comprehensive searches. CINAHL covers nursing and allied health literature. Google Scholar is a broad search engine useful for initial exploration but lacks structured search capability.

Search Strategy

Effective searching uses MeSH terms combined with Boolean operators (AND, OR, NOT). Filters are applied for publication date, study type (RCT, systematic review), human subjects, and English language. Searches should start broad and narrow with additional search terms. Reference lists of key articles should be reviewed for additional relevant studies, and alerts can be set up for ongoing monitoring of topics of interest.

Critical Appraisal of the Literature

Evaluating Randomized Controlled Trials

Key questions when evaluating an RCT address randomization (was allocation truly random, and was concealment of allocation used to prevent selection bias?), blinding (were patients, providers, and outcome assessors blinded, keeping in mind this is difficult in surgical trials?), sample size (was a power analysis performed, as underpowered studies risk Type II errors or false negatives?), intention-to-treat analysis (were all randomized patients analyzed in their assigned groups?), and follow-up (was it adequate and complete, with loss to follow-up greater than 20% threatening validity?). The CONSORT statement provides a standardized checklist for reporting RCTs.

Evaluating Systematic Reviews and Meta-Analyses

Systematic reviews are evaluated using the PRISMA guidelines for standardized reporting. The search strategy should be comprehensive and span multiple databases. Inclusion and exclusion criteria should be explicit and appropriate. Heterogeneity is assessed by the I-squared statistic, with values greater than 50% indicating significant heterogeneity. Publication bias is assessed by funnel plot symmetry, recognizing that small negative studies are less likely to be published. The risk of bias in included studies should be evaluated using the Cochrane ROB tool, and the conclusions should be supported by the data.

Evaluating Observational Studies

The STROBE statement provides reporting guidelines for cohort, case-control, and cross-sectional studies. Confounding variables should be identified and controlled for. Selection bias is assessed by examining how patients were selected and whether there were systematic differences between groups. Outcomes should be objectively defined and measured. Critically, observational studies demonstrate associations rather than causation.

Understanding Statistical Concepts

Key Terms

The p-value represents the probability of observing the result (or more extreme) if the null hypothesis is true, with the convention of p less than 0.05 for statistical significance. The confidence interval (CI) is the range within which the true effect likely lies (95% CI) and is more informative than the p-value alone. The number needed to treat (NNT) indicates how many patients need to be treated to prevent one adverse event. Relative risk (RR) is the ratio of event rates between groups, used in cohort studies and RCTs. The odds ratio (OR) is the ratio of odds of an event, used in case-control studies and approximating relative risk when the event is rare. Absolute risk reduction (ARR) is the difference in event rates between groups and is clinically more meaningful than relative risk.

Statistical vs. Clinical Significance

A statistically significant result may not be clinically meaningful, as small differences can reach statistical significance with large sample sizes. The magnitude of effect (effect size) and its clinical relevance should always be assessed. For example, a new fixation system that reduces operative time by 3 minutes (p=0.02) is statistically significant but clinically trivial.

Applying Evidence to Practice

Clinical Practice Guidelines

Clinical practice guidelines synthesize evidence into actionable recommendations, such as the AAOMS guidelines for MRONJ and third molar management. They are graded by strength of recommendation and quality of evidence and should be updated regularly as new evidence emerges. Guidelines are recommendations rather than mandates, and clinical judgment for individual patients remains paramount.

Barriers to EBP in OMFS

Barriers include limited Level I evidence for many surgical questions, surgeon bias and attachment to established techniques, time constraints for literature review in busy clinical practice, industry influence on research funding and publication, and the difficulty of conducting blinded surgical trials.

Strategies for Overcoming Barriers

Strategies for overcoming these barriers include journal clubs for regular critical appraisal of current literature, continuing education through conferences, online courses, and society meetings, participation in multi-center trials and registries, critical evaluation of industry-sponsored research for bias, and maintaining a culture of questioning and lifelong learning.

Clinical Pearls

The PICO framework transforms vague clinical questions into searchable, answerable queries. Most OMFS literature is Level III to IV evidence, meaning the surgeon must often make decisions based on imperfect evidence. Statistical significance does not equal clinical significance, and the magnitude and clinical relevance of the effect should always be assessed. Systematic reviews are only as good as the primary studies they include, so the included studies must be critically appraised rather than just the conclusions. Evidence-based practice is a skill that improves with practice, and critical appraisal should be made a regular habit through journal clubs and self-directed learning.

References

1. Sackett DL, et al. "Evidence Based Medicine: What It Is and What It Isn't." BMJ. 1996;312(7023):71-72.
2. OCEBM Levels of Evidence Working Group. "The Oxford Levels of Evidence 2." Oxford Centre for Evidence-Based Medicine. 2011.
3. Dodson TB. "Evidence-Based Medicine and Its Application to Oral and Maxillofacial Surgery." Journal of Oral and Maxillofacial Surgery. 2006;64(9):1426-1430.
4. Greenhalgh T. How to Read a Paper: The Basics of Evidence-Based Medicine and Healthcare. 6th ed. Wiley-Blackwell; 2019.

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