Evidence-Based Medicine

MD. Chia-Chen Hsu

The Steps in the EBM Process

The patient 1. Start with the patient -- a clinical problem or question arises out of the care of the patient

The question 2. Construct a well built clinical question derived from the case 

The resource 3. Select the appropriate resource(s) and conduct a search

The evaluation 4. Appraise that evidence for its validity (closeness to the truth) and applicability (usefulness in clinical practice)

The patient 5. Return to the patient -- integrate that evidence with clinical expertise, patient preferences and apply it to practice

Self-evaluation 6. Evaluate your performance with this patient

Step 1

Start with the patient -- a clinical problem or question arises out of the care of the patient A 65 y/o female patient visited our clinic with major complaint of right anterior knee pain for six months.

She had received right TKA for 3 years. Non-resurfacing patella was found by radiololgical examination. Should we resurface the patella in every TKA ?

Step 2Construct a well built clinical question derived from the case

Formulating Answerable Questions 形成可回答的問題

Question components: PICO– What types of P articipants ? Patient and the

ir problem– What types of I nterventions ? Intervention– What types of C omparison ? Comparison– What types of O utcomes ? Outcome

Patient or problem

Intervention Comparison Outcome

Description of the patient or the target disorder of interest

ExposureDiagnostic testPrognostic factorTherapyPatient perception

Relevant most often when looking at therapy questions

Clinical outcome of interest to you're your patient

PICO

Type of Question

EBM starts with a clear clinical question

Well defined in order to be answerable Clinical questions generally fall into

1. Causation / Etiology / Harm2. Diagnosis / Screening3. Therapy / Prevention4. Prognosis / Nature history

The well-formulated question: Therapy

People – Exposure – Comparison – Outcomes My Question

In a 65 y/o woman with a end-stage degenerative OA knee, could the patella resurfacing decrease the risk of anterior knee pain after total knee replacement ?

In a 65 y/o woman with a OA knee, can patellar resurfacing in TKA surgery decrease the risk of anterior knee pain compared with non-resurfacing of patella ?

Step 3The resource

Select the appropriate resource(s) and conduct a search

What is the ideal resource?– Located in the clinical setting – Easy to use – Fast, reliable connection – Comprehensive /Full Text – Effective search engine – Provides primary data

Resources

• Colleagues • Textbooks

– Burn your (traditional) textbooks• Summaries of the primary evidence

– ACP Journal Club | Clinical Evidence | eMedicine | POEMs and InfoRetriever | UpToDate

• Databases– MEDLINE | Cochrane Library

• Electronic textbooks and libraries– Harrisons | MD Consult | Scientific American Medicine Online | Stat!

Ref • Meta-Search Engines

– SUMSearch | TRIP: Turning Research into Practice

Limits

Types of Studies

87:1438-1445, 2005. J Bone Joint Surg Am.Emilios E. Pakos, Evangelia E. Ntzani and Thomas A. Trikalinos

Investigation performed at the Clinical Trials and Evidence-Based Medicine Unit, Department of Hygiene and Epidemiology,University of Ioannina School of Medicine, Ioannina, Greece, and the Institute for Clinical Research and Health Policy Studies,Tufts-New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts

Level of Evidence: Therapeutic Level I.

Patellar Resurfacing in Total Knee Arthroplasty. A Meta-Analysis

If the sole evidence you have about a treatment is from non-randomized studies, you have five options:

Doing another literature search See whether the treatment effect is so huge, unethical

to randomize Trial concluded that the treatment was useless or

harmful “n-of-1” trial Try to find evidence for some other treatment or simply

provide supportive care.

Randomized Trials

A Randomized Trial is most effective in experimental studies to make generalizations about a population because:

– Randomization decreases bias from confounding factors – Blinding both the investigators and patients decreases bias.

Advantages: – Strong Evidence for cause and effect – Can be faster and cheaper than observational study

Disadvantages: – Can be costly and of long duration – Ethical issues may prevent experimentation – Disease may be too rare – Study intervention may be too different from common practice – Tend to restrict scope and narrow the study question

Patellar Resurfacing in Total Knee Arthroplasty

Background: Patellar resurfacing during total knee arthroplasty remains controv

ersial. We aimed to evaluate the effectiveness of this technique through an evaluation of the current literature.

Methods: We performed a meta-analysis of randomized controlled trials com

paring total knee arthroplasties performed with and without patellar resurfacing. Outcomes of interest included the number of reoperations, the prevalence of postoperative anterior knee pain, and the improvement in various knee scores.

Materials and Methods

Searched MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials for randomized trials comparing total knee arthroplasties performed with and without patellar resurfacing;

References of retrieved articles were also screened. no language restrictions. regardless of the indication for total knee arthroplas

ty, the surgical technique, or the specific type of prosthesis used.

the risk of reoperation in knees with resurfaced and nonresurfaced patellae

the risk of reoperation according to the duration of follow-up

The risk of postoperative anterior knee pain

Patellar Resurfacing in Total Knee Arthroplasty

Results1:

Ten trials assessing 1223 knees were eligible.

The absolute risk of reoperation was reduced by 4.6% (95% confidence interval, 1.9% to 7.3%) in the patellar resurfacing arm (between-study heterogeneity, p < 0.01; I2 = 60%),implying that one would have to resurface twenty-two patellae (95% confidence interval, fourteen to fifty- two patellae) in order to prevent one reoperation.

(NNT= 1/ARR = 1/ 4.6% = 21.7)

Patellar Resurfacing in Total Knee Arthroplasty

Results 2: Patellar resurfacing reduced the absolute risk of postoperative anterior knee pain by 13.8% (95% confidence interval, 6.4% to 21.2%), implying that one would have to resurface seven patellae (95% confidence interval, five to sixteen patellae) in order to prevent one case of postoperative anterior knee pain.

(NNT= 1/ 13.8% = 7.24)

Only four trials provided adequate data for a quantitative synthesis of the changes in the various knee scores; on the basis of those four trials, there was no difference in the mean improvement in the knee scores (standardized mean difference, 0.03; 95% confidence interval, −0.50 to 0.56).

Conclusions

The available evidence indicates that patellar resurfacing reduces the risks of reoperation and anterior knee pain after total knee arthroplasty.

The observed effects are clinically important despite their modest magnitude.

Additional, carefully designed randomized trials are required to strengthen this claim.