Chiropractic Forensics
Library
William Cockburn,D.C.
Keywords: Subluxation, Lumbar Spine, Digitizing, Reliability, Repeatability, Error Factors, Validity.
Abstract: X-ray digitizing has been promoted as a highly reliable, quantitative outcome assessment tool in the adjunctive diagnosis of spinal subluxation (osseous component). There are also arguments which consider the inter and intra examiner reliability of landmark identification for biomechanical measurement (mensuration). This study yielded significant data to verify the clinical efficacy and in fact, necessity of digitization of plain film x-ray in the clinical chiropractic environment.
Introduction: The analysis of spinal instability has been for nearly a century the cornerstone of chiropractic analytical technique. In the development of other technologies such as CAT and MRI scanning, this art and science has been diminished in value. This is unfortunate as the medical and chiropractic literature for decades has espoused the virtue and indeed the necessity of measurement.
One technique, referred to as x-ray digitizing, has fallen under scrutiny for its inability to demonstrate reliability and repeatability. This is anecdotal, but there is basis due to a lack of research funding to sponsor serious double blinded study, and has nothing to do with the accuracy and reliability of the procedure.
At a recent seminar, the issue of x-ray digitizing was brought before this author. Fortunately the manufacturer of the equipment was present as a vendor and graciously agreed to allow this evaluator to perform a reliability study with the attendees present. This in itself is remarkable, as many vendors of medical equipment have, in the past, refused to allow such a "trial" for fear of untrained physicians making too high an error with their respective procedure.
At the luncheon break, nine participants were able to digitize a lateral lumbar spine neutral weightbearing film. This was performed twice by each clinician in order to determine if intra and inter examiner reliability could be demonstrated.. The results were quite remarkable and encourage others to design similar study.
Previous investigators evaluating spinal biomechanics and comparing the outcome of measurement have incorrectly attempted to correlate these type of clinical findings with pain. This was error. Biomechanic evaluation of plain film, and indeed motion or stress film is to determine instability and biomechanical failure, which is often asymptomatic. Thus the only salient argument affecting appropriateness of x-ray digitizing is its reliability and repeatability between evaluators and by the same evaluator.
Study Design: A neutral lateral lumbar radiograph was determined to be of sufficient quality, penetration and of appropriate patient placement to warrant analysis. The film was taped to a Summagraphics digitizing tablet to insure that it did not move during or between input of the examiners. A 486 computer and SDI Systems software (Spinalyzer) were utilized..
Nine individuals participated in the study. Eight doctors of chiropractic and one engineer. The lateral lumbar film has 29 landmarks for identification purposes. Initially, only the sacral base and the lower epiphyeal plate of L5 were to be utilized, consisting of two points on each segment. These points would be used to measure the sacral base angle and the L5\S1 disc angle.
We decided however, to produce more accurate results, all five lumbar vertebrae and the first segment of the sacrum would be analyzed. Five points on each lumbar verterba were identified. The anterior inferior, anterior superior, posterior superior, posterior inferior and spino-laminar junction were selected. The additional four points were two on the sacral base and two at the fused epiphyseal line of the 1st and 2nd sacral segments.
Each clincican digitized the film, beginning at the lowest points on the sacrum and progressively moving cranial to the superior endplate of L1. This digitization was saved with a physician identification number and then a second digitization of the same film was performed so that intra examiner reliability could be measured for each clinican.
Instructions: The only instructions given were to locate the corners and spinolaminar junctions of the vertebrae as displayed point by point on the computer monitor guide as each point is input to the system., and to insure that they took their time and did not hurry. Average time per film for input was approximately 1 minute.
Measurements: As x-ray analysis is vital to the objective diagnosis of patients with spinal injury with instability, we decided to select measurements which are difficult to calculate by hand. For example a distance measurement, as in a disc height, requirs only two points to be identified in a straight line. An angle however, as in the method of Cobb for scoliosis measurement, requires four lines, (one off each vertebral endplate, and then intersecting lines at 90 degree angles) to form a point at which the angle can be measured with a protractor.
Commonly, errors in hand drawing these lines take place, as well as error in the actual measurement of the angle. Our belief was that by identifying only the smallest of dots at the corners of the vertebrae and allowing the computer to perform all calculations from these "landmarks", the most accurate of measurements could be made. We felt that this would also provide a barometer for determining if clinicians could agree on landmark placement, if they could digitize film with ease, if the two sets per doctor produced reliability and repeatability, and our main aim, to determine if the measurements made were inter-examiner reliable, were error free and deemed to produce clinical utility.
The measurements chosen were: 1) The Sacral Base Angle (Ferguson), 2) Translation of L3, L4 & L5, 3) Disc Angle of L3, L4, & L5, 4) Anterior Disc Height at L3, L4 & L5 and finally 5) The Baseline angle between L3, L4. Qualitative measurements such as standard baselines, plumbline analysis, Georges Line, etc. were not used because of these measurements inability to produce quantitative data.
I would like to point out that a qualitative measurement does not necessarily mean it is not integral or important to diagnosis. We simply felt that a variety of quantitative measurements could be utilized to validate or invalidate the reliability issues which we were evaluating.
Results: Our findings are presented in the following tables and will be discussed individually.
Fergusons Sacral Angle Fig 1: This is the angle of the sacral base as compared to a true horizontal. It is often utilized in determining pelvic stability, lumbar causation of hypolordsis, and occassionally as a guide to determining if a worker my be prone to injury in a heavy lifting job.
The maximum angle difference between the two sets for the same evaluator was .9 degrees. The minimum was .2 degrees. The differences intra-examiner were compared by taking the delta from the two sets of measurements for each participant and then comparing that number to each other participant. (Fig. 1). Inter-examiner reliabilty for the sacral base angle was high, with a mean of 0.36 degrees. The actual measurements by set and evaluator are presented in the bar graph (Fig. 2.). This represents an extremely high level of accuracy and reliability both inter and intra examiner for digitization and measurement of the sacral base angle.
Lumbar Disc Angle: This measurement is taken from the endplates of two adjacent lumbar segments, the inferior endplate of the superior vertebra is compared to the superior endplate of the subjacent vertebra. An angle is formed and measured. Literature suggests that in flexion and extension x-ray templating, an increase of more than 11 degrees in disc angle is indicative of significant pathology and indeed impairment.
The maximum angle difference between the two sets for the same evaluator was 2.1 degrees. The minimum was 0.0 degrees (three evaluators). The differences intra-examiner were compared by taking the delta from the two sets of measurements for each participant and then comparing that number to each other participant. (Fig. 3). Inter-examiner reliabilty for the sacral base angle was high, with a mean of 0.57 degrees for all nine examiners between two sets of three vertebral levels evaluated.. The actual measurements by set and evaluator are presented in the bar graph (Fig.3.). This represents an extremely high level of accuracy and reliability both inter and intra examiner for digitization and measurement of lumbar disc angle.
Baseline Angle: This angle is constructed by comparing a line drawn through the lower epiphyseal plate of the vertebrae and comparing this line to a true horizontal. The resulting angle is measured and compared to the vertebra above and below to assist in determintion of flexion and extension mal-position in the lateral radiograph.
The maximum angle difference between the two sets for the same evaluator was 0.8 degrees. The minimum was 0.0 degrees . The differences intra-examiner were compared by taking the delta from the two sets of measurements for each participant and then comparing that number to each other participant. (Fig. 4).
Inter-examiner reliabilty for the sacral base angle was high, with a mean of 0.57 degrees for all nine examiners between two sets of three vertebral levels evaluated.. The actual measurements by set and evaluator are presented in the bar graph (Fig.5.). This represents an extremely high level of accuracy and reliability both inter and intra examiner for digitization and measurement of vertebral baseline angles.
Anterior Disc Height: The anterior disc height measurement is made for the L3, L4 and L5 segments. This measurement is taken from the inferior anterior endplate of the superior vertebral body and the superior anterior endplate of the subjacent vertebral segment in the motor unit.
The maximum disc height meaurement difference between the two sets for the same evaluator was 2.1 millimeters (1 examiner). The minimum was 0.0 millimeters
(6 examiners) . The differences intra-examiner were compared by taking the delta from the two sets of measurements for each participant and then comparing that number to each other participant. (Fig. 6).
Inter-examiner reliabilty for the sacral base angle was high, with a mean of 0.4 millimeters for all nine examiners between two sets of three vertebral levels evaluated.. The actual measurements by set and evaluator are presented in the bar graph (Fig.6.). This represents an extremely high level of accuracy and reliability both inter and intra examiner for digitization and measurement of vertebral baseline angles.
Translation of Vertebral Body: Also known as listhesis or offset, this measurement is utilized to determine loss of integrity of the ligamentous and disc structures of subjacent spinal motor units and is also valuable in differentiating subluxation from dislocation. The measurement is made by drawing a line through the posterior vertebral body and comparing that line to the superior posterior aspect of the subjacent vertebrae. Literature varies widely with a range of 1.1 mm to 3.5 mm for pathology. This is possibly due to different evaluators looking at neutral static (1.1 mm) versus flexion and extension (3.5mm).
The maximum offset or translation meaurement difference between the two sets for the same evaluator was 1.5 millimeters (1 examiner). The minimum was 0.0 millimeters
(8 examiners) . The differences intra-examiner were compared by taking the delta from the two sets of measurements for each participant and then comparing that number to each other participant. (Fig. 7).
Inter-examiner reliabilty for the translation or offset was high, with a mean of 0.19 millimeters for all nine examiners between two sets of three vertebral levels evaluated.. The actual measurements by set and evaluator are presented in the bar graph (Fig.7.). This represents an extremely high level of accuracy and reliability both inter and intra examiner for digitization and measurement of vertebral translation..
The entire data set for all measurements made in this study are presented for review in Table 1.
Conclusion: X-ray digitizing is a highly accurate, reliable and repeatable tool in the hands of chiropractic clinicians for the evaluation and adjunctive diagnosis of the osseous component of spinal injuries, subluxation diagnosis and in the development and management of the treatment plan. While hand measurement, with its inherent liabilities is well documented throughout the literature, the digitization of radiographs is the gold standard in the modern technological world for this form of evaluation. We have demonstrated objective, quantified correlation that is inter and intra examiner reliable and repeatable..
Discussion: There is great controversy in the literature concerning measurement of plain and motion film radiographs in the adjunctive diagnosis of patients with potential spinal injuries, with or without pain.
It is clear that spinal slippage or loss of motion segment integrity is a pathology and is ratable as evidenced by the American Medical Association Guides to Permanent Impairment, 4th edition.
Unfortunately, many physicians suffering from financial and political pressures of the emerging managed care era have lost sight of objectivity and have begun to work for third parties in an attempt to suppress valuable clinical data, in order to save those parties from high judgments in the trial courts and in payment of necessary treatment. This is not acceptable. The hearsay opinion of inept claims reviewers can only be combated by science and technology for the benefit of the patient, regardless of financial outcome.
To use the most scientific tools available for the correct decisions and judgments concerning our patients should be our goal. This should be rewarded, not condemned.
NOTE: Figures and Tables referrenced in this aricle have intentionally been excluded from the web site due to size limitations and are available directly from the author.
Home
Goals Definitions
Legal FAQ
Objective DX
Library
Related Sites