Methods for identifying and evaluating quality spine measurements
In our previous two books, Spine Outcomes Measures and Instruments and Spine Classification and Severity Measures, the measures that we attempted to identify and evaluate were literature driven. We systematically searched the literature for all available measures. Such an approach was beyond the scope of this book since there is an abundance of spine measurements in use today. Therefore, experts in each specialty area were invited to identify all measurements that they felt were common, clinically relevant, and sometimes controversial. Each clinical author was directed to refer to the following three questions when writing their chapter and selecting the measurements to be evaluated:
What are the most suitable tests or measurements to test disease or trauma with a spine population?
What are the most reliable screening tests during preoperative evaluation of spine patients?
What is the scientific basis for the use of these tests and measurements in a spine population?
These measurements were compiled and evaluated for quality in each of the chapters corresponding to the specialty area.
What makes a quality spine measurement?
Many factors must be considered when selecting a “quality spine measurement”. An explanation of these factors is the main focus of this chapter. In assessing the overall quality of a spine measurement, two major areas should be considered: scientific validity and clinical utility.
Scientific validity
Our expert panel agreed that a measurement tool should possess the following four methodological qualities:
Interobserver reliability
Intraobserver reliability
Universality
Disease specificity
The value of interobserver and intraobserver reliability is obvious. If one cannot reliably repeat a measurement, or if a second individual cannot reliably reproduce that measurement, then that measurement has little worth. We have reviewed the literature to assess interobserver and intraobserver reliability for all measurements.
Universality refers to the spectrum of diseases for which a measurement tool can be used. The Adams trunk forward bending test, for instance, could be considered one of the most simple “back tests”, being representative of the ability of a patient to lean forward. This test can be performed by any patient with almost any spine condition, and some conclusions as to mobility, flexibility, and trunk conditioning of the patient can be drawn. For certain thoracolumbar scoliotic deformities this test becomes particularly relevant as it will show unilateral trunk elevation indicative of an axial rotational deformity.
Disease specificity reflects the accuracy of the measurement in indicating disease. For example lumbar range of motion is a nonspecific measure, whereas Schober′s test may more specifically suggest pathology, such as ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis.
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