Upper cervical Subluxations manifest clinically in various forms of postural distortion (i.e., functional leg length inequality, pelvic distortion, head and shoulder tilt, head translation, unequal weight distribution). Clinically, it has been found that functional Leg length inequality (LLI) and upper cervical Subluxations occur concomitantly. The Supine leg check (SLC) has been the primary assessment used by orthogonally based upper cervical practitioners for more than 50 years. The term functional pelvic distortion (FPD) has been previously introduced.¹ This may be a more accurate descriptor for what the doctor is actually measuring—muscle tone imbalance and resultant pelvic distortion—as opposed to LLI.

FPD contrasts with Anisomelia, which is an anatomical short leg. Various studies have revealed that an anatomical short leg of 5 millimeters or more occurs in about half of the adult population.²,³,⁴,⁵ Approximately 90% of the population has been found to have some degree of LLI, with an average amount of about 5 millimeters.⁶ However, several possible inaccuracies in this observation have been previously covered.¹ Subluxations and the resultant postural distortion can have a significant effect on the measurement of femur head heights. It is recognized that anatomical short legs do exist, although the frequency can be debated. In clinical practice, upper cervical practitioners have observed that more than 90% of their patients are “balanced” (equalization of the SLC) after the Subluxation is reduced. However, a balanced supine or prone leg check does not necessarily mean that the patient does not have an Anisomelia, as these two phenomena likely occur concurrently in many cases.

Research has shown very high inter- (>0.9 intraclass correlation coefficient) and Intraexaminer Reliability for the SLC⁷ and moderate Reliability for prone leg checks.⁸,⁹,¹⁰ The Hinson and Brown study⁷ found that doctors were able to reliably measure the recumbent LLI to within 1/4 inch in 80% of cases and within 1/8 inch in 60% of the trials. Cooperstein et al.¹¹ found that a blinded examiner had an excellent test-retest Reliability (ICC = 0.85) for assessing artificial LLI (insertion of shims in boot) with prone leg checks. Pilot studies on pre- and postassessment of FPD after an upper cervical Adjustment have been conducted,¹²,¹³,¹⁴ with larger Validity studies to be conducted.¹⁵

These types of studies involve a group of patients being initially examined by a group of doctors with the SLC. The patients then receive an upper cervical Adjustment, sham Adjustment (in one particular study design), or no Adjustment. This is followed by a group of doctors conducting an SLC who are blinded to the type of intervention that was provided to the patient. The purpose of the study is to determine if the doctors can assess a marked change in FPD as a result of the chiropractic intervention, as opposed to the doctor’s bias. Pilot studies have been promising, but more published research is necessary.

LLI has a different clinical significance to various physicians. For some, this condition is thought to have no importance until the inequality is ½ inch or greater.¹⁶
To the other extreme, many authors feel that a difference of just a few millimeters is significant for various musculoskeletal symptoms.¹⁷,¹⁸,¹⁹,²⁰,²¹,²²,²³,²⁴ Compelling evidence has been published that shows:

The assessment of upright posture is an important outcome that is also monitored by upper cervical doctors. Posture has been shown to be a somewhat stable condition⁶⁵,⁶⁶,⁶⁷,⁶⁸,⁶⁹,⁷⁰,⁷¹,⁷²,⁷³,⁷⁴ that can be reliably assessed.⁶⁶,⁷⁰,⁷⁵,⁷⁶,⁷⁷,⁷⁸,⁷⁹,⁸⁰,⁸¹,⁸²,⁸³,⁸⁴,⁸⁵ The challenge is to objectify postural analysis. Devices ranging from wall-mounted grids (Fig. 9-1) to computerized technology have been used to improve such assessments. The Grostic/Orthospinology Adjustment is considered to be a full spine correction. This may be considered an a priori assumption; however, it is supported by a wealth of clinical data over the past 60 years. Studies have revealed significant postural and bilateral weight-bearing changes resulting from subjects receiving upper cervical Adjustments.⁵⁹,⁶⁰,⁸⁶