By far the most important experimental study is the Randomized
Controlled Trial
A single variable is randomly assigned; this may be called the
independent variable and is usually a treatment.
Each different treatment is called an arm of the study. The outcome
variables are clinical, radiographic, or functional measures of the
success of management
Randomization limits the dependence of outcome variables on other
factors in the study (e.g., gender, age, fracture severity), thus
helping to isolate the effect of the treatment on outcomes
These other factors are often called confounding
variables, because they may also influence the outcome
variables if they are not properly addressed
Randomized control trials control for confounding and bias and
isolate the effect of the treatment on the outcomes (to the greatest
extent possible)
The disadvantages are cost, complexity, and the ethical
considerations involved in randomly assigning treatments
Several modifications of Randomized control trials are important.
Crossover studies – These involve switching patients
between different arms of the study.
For example, one arm may receive physical therapy for 4
weeks and another arm medical therapy for 4 weeks. Then the
patients switch therapies for another 4 weeks.
Such patients may act as their own controls and increase the
power of the study.
If patients wait a period of time between therapies,
receiving no therapy, this is a washout period in
which the effect of the first therapy is allowed to wear
off.
Partial compliance – Many Randomized control trials
involve imperfect compliance with the study protocol by patients
who find the protocol difficult to adhere to
If this effect is large, special analytic methods are needed
to increase confidence in the results