The Supine Leg Check (SLC) is a screening test for the Atlas Subluxation Complex (ASC) used by the National Upper Cervical Chiropractic Association (NUCCA). A difference in observed leg length inequality (LLI) of 0.25 (1/4) inch indicates the presence of the ASC indicating need for a postural assessment. Use of the SLC as the only indicator for making the correction and determining that the ASC was reduced on post assessment, is an improper use of the test. As Dr. Gregory states: “It must, however, be borne in mind that it is only one means of determining the presence of a C1 subluxation, a subjective one at that; and should be used in conjunction and in agreement with other subluxation determining devices”.
In 1943 Dr. John Grostic began recording the results of the SLC on patient’s listing cards. In February 1979, Dr. Ralph R. Gregory reported a rigorously investigated procedure outlined in the Upper Cervical Monograph, A Model for the Supine Leg Check. Any guidelines for the proper use and performance of the test are contained therein. The NUCCA Textbook omitted the head-rotation sequence of the test procedure.
The SLC does not look for a “short leg” or anatomic short leg but the presence of inequality in observed leg length or a functional short leg. Dr. Gregory preferred the term “contractured leg”, which he defined as: “An apparent difference in the leg length of a C1 subluxated individual when measured in the supine position, and resulting from spastic contracture of the extensor musculature of the spinal column”.
According to NUCCA theory, observed functional leg length inequality (LLI) is an indirect result of the imbalance in reticular regulation of muscle reflexes originating from the ASC. Functional LLI, as measured by the SLC, results from muscle tonus observed in spastic contracture affecting the pelvis or pelvic obliquity. This functional pelvic unleveling moves the entire spine away from the vertical axis. The SLC is not a test for determining an anatomic short leg.
A 2006 study in JMPT by two medical doctors, Timgren and Soinila, Reversible Pelvic Asymmetry suggest reversible pelvis asymmetry is demonstrated by an apparent leg length difference and scoliosis. The intervention was a thrust or manipulation on the ankle of the side with a dysfunctional SI joint. Coupled with this was a self-embracing muscle energy technique. This article brings some credence that pelvis asymmetry can create an apparent short leg. Their conclusions: “Acquired postural asymmetry of the sacroiliac joint may be a neglected cause of several neurologic and other pain-related symptoms that can be relieved by a simple and safe treatment”. The next research question to ask is what effect would a NUCCA correction intervention have on postural asymmetry and apparent short leg?
In 1992, Manello published Leg Length Inequality in JMPT, reporting an extensive literature review on the various tests and procedures used to determine leg length inequality in medicine and chiropractic. This is the ‘go-to’ article for developing a solid background on the topic.
Dr. Gary Knutson published a study, in 2000, “The supine leg check as a determinant of physiological/postural leg length inequality: A case study and analysis”, concluding: “within certain parameters, non-weight-bearing postural leg checks are evidence of physiological or postural, and not anatomic, LLI”. This defines the SLC as a functional test of leg length inequality.
In 2005, Dr. Knutson revisited the contractured leg in a two-part article, Anatomic and functional leg-length inequality: A review and recommendation for clinical decision-making. The first part discusses the anatomic short leg where he concluded: The prevalence of anatomic inequality was found to be 90%, the mean magnitude of anatomic inequality was 5.2 mm (SD 4.1) (~1/5-inch). The evidence suggests that, for most people, anatomic leg-length inequality does not appear to be clinically significant until the magnitude reaches ~ 20 mm (~3/4-inch). Anatomic leg-length inequality is near universal, but the average magnitude is small and not likely to be clinically significant.
In part two, the functional or unloaded leg-length asymmetry was discussed and he concluded that: The unloaded, functional leg-length alignment asymmetry is a likely phenomenon, although more research regarding reliability of the measurement procedure and validity relative to spinal dysfunction is needed. Functional leg-length alignment asymmetry should be eliminated before any necessary treatment of anatomic LLI.
While the 70+ year history of SLC use would conclude the test is reliable and valid, the scientific literature reflects Dr. Knutson’s conclusion. Very few of the tests used clinically in chiropractic have been subjected to statistical tests in measurement of their consistency. There has been some investigation, specifically, into the reliability of the SLC, among and between chiropractors (intra and inter-examiner reliability). Through anecdote it seems obvious that Drs. Grostic and Gregory researched the SLC as it was developed and it was then further honed by Dr. Gregory for the 1979 article, yet there is no written record in existence.
The first reliability study specifically on the SLC was performed by Addington, as reported in the Upper Cervical Monograph in 1983. He concludes: the assessments used were “incapable of producing consistent patient evaluation.” The conclusion of low reliability as indicated by the statistical analysis may be a reflection of the study design and execution, having an inadequate sample size for investigation being principal. This indicates the need for proper planning in study design for further investigation.
Drs. Roger Hinson and Susan Brown pick up the investigational gauntlet of the SLC in their 1998 study, Supine Leg Length differential estimation: An inter- and intra- examiner reliability study, published in the now defunct Chiropractic Research Journal which was never indexed. Knowledge of this study is thereby limited by not being indexed in Pub Med further supporting the supposition, ‘if it is not in Pub Med, it does not exist.’ Their conclusion: “Our study supports the thesis that experienced clinicians can reliably estimate supine leg length differential in practice.”
Further study in 2000 by Hinson et al., Pre- and Post-adjustment Supine Leg-Length Estimation was published as a conference abstract in the Journal of Chiropractic Education, indexed by Pub Med. Their conclusion; “Spinal adjustments resulted in a decrease in LLI in the experimental group. The LLI in the control group decreased as well, but to a lesser degree.” In the same journal, Hoiriis et al. published another conference abstract, Baseline Characteristics of Chiropractic Patients: Correlation of Anatometer Readings with Supine Leg-Length Inequality. Their conclusions, in reference to concomitant posture assessment: “The supine short leg occurs on the opposite side from that of the heavy side and the high ilium.” Conversely the contractured leg occurs on the side of the low ilium that does not support body weight as much as the other (light side).
There has yet to be an investigation into prevalence of atlas misalignment in the general population. As a result of the hypertension study, based on advice from the NIH, Drs. Bakris and Woodfield began developing a research proposal for developing the SLC as a screening test for atlas misalignment. Presence of an atlas misalignment would then require further evaluation to determine the presence of the ASC. Due to the lack of a track record of prior investigations on the SLC appearing in the indexed literature, two proposals submitted to the NIH were rejected. Establishing this track record in the indexed literature of SLC investigation is vital for the sustainability of the NUCCA procedure. The first question to address is if it possible to demonstrate any reliability to any leg check procedure. From the literature review the track record is poor, yet the majority of those studies are with anatomic tests.
In 2007 in JMPT, Schneider et al. report on a functional LLI procedure in Interexaminer Reliability of the prone leg length analysis procedure. Their conclusions: “results indicate that 2 clinicians show good reliability in determining the side of the short leg in the prone position with knees extended but show poor reliability when determining the precise amount of that leg length difference.” This indicates that agreement which leg is short is possible, while agreement in estimating the actual difference presents more of a challenge.
One difficulty in establishing reliability of a procedure is the inherent variability naturally present between examiners. It may be possible through extensive training to minimize this variability between examiners thereby increasing their agreement and reliability of the procedure. In 2009 in JMPT Holt et al. use a training procedure as reported in Interexaminer reliability of a leg length analysis procedure among novice and experienced practitioners. “Examiners had 8 consensus training sessions that lasted approximately 45 minutes each.” It is apparent from the conclusion that consensus training increases the ability of examiners to agree: “this study revealed good interexaminer reliability of all aspects of the leg length analysis protocol used.”
The question then exists; will training work for the SLC? In Efficacy of Hands-on Instructional Training for the Supine Leg Check: A Feasibility Study published in a conference abstract, it was reported a 10% increase was obtainable in both intra- (77%) and inter-examiner (70%) agreement. The challenge is that only near perfect agreement is an acceptable standard.
A more intense training session before the study was planned in the follow up, Interexaminer reliability of supine leg checks for discriminating leg length inequality. Published in 2011 in JMPT, Woodfield, et al. concluded: “the examiners showed moderate reliability in assessing leg-length inequality at 1/8-inch increments and good reliability in determining the presence of a leg-length inequality.”
From this study, improvement in study design based upon these results has been developed. At this point in time using the Bakris-Woodfield proposal where the anatomical leg length inequality is ‘normed’ at baseline by the gold standard CT-scanogram with use of a NUCCA correction intervention could conserve finances while providing more relevant information. A study such as this with established reliability in the orthogonal radiograph marking and analysis procedure could carry great impact and allow for beginning use of the SLC as a screening test to determine prevalence of atlas misalignment in the general population.