The findings of this study do not completely align themselves with the most common CCP somatic dysfunctions. Interestingly, though, the sacrum and lower lumbar spine dysfunctions—left-on-left sacral torsion and right rotation of L4 and L5—were what one would expect to find in the majority of an asymptomatic population. Although these were the most commonly found dysfunctions, only 45% of participants' sacral dysfunctions resulted in the lower lumbar spine rotating in the opposite direction to the sacrum, a finding widely reported in the osteopathic literature.
2 In further disagreement with the CCP was the most common somatic dysfunction found in the pelvis: a superior shear in contrast to the commonly found innominate rotations.
While right anterior innominate dysfunctions were significantly associated with an ipsilateral longer leg (or contralateral shorter leg), left anterior innominate dysfunctions were not associated with either a left or a right shorter leg in the supine position. According to published literature,
1,3,11,37 right anterior innominate rotation will occur with ipsilateral shorter lower extremities. An explanation for this finding is that with small LLDs, the innominate bone may attempt to rotate anteriorly to lengthen the shorter leg to approximate the leg closer to the ground for more even weight-bearing distribution in a standing position (ie, compensating for the compensation).
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The sacrum and lumbar spine may also compensate in an unexpected way with small LLDs. Perhaps compensations occur elsewhere, such as through rotation of the femur or tibia or through slight adjustments at the hip, knee, and ankle joints. Compensation may occur differently when the LLD is small or if an individual is asymptomatic, thereby not adjusting his or her posture secondary to pain. Further, minor LLDs may not be as obvious when measured in a supine position as they are in a standing position. The current study showed, for example, that the leg length was always diminished in the supine position compared with its measurement in the upright position. In agreement with this finding, the apparent longer leg in the standing position may appear to retract when in the supine position. An alternative explanation is that in individuals who do not compensate for their LLDs, such as those with minor LLDs, the innominate bone may not accommodate for the LLD. Therefore, an anterior innominate rotation could be the driving force behind leg lengthening or it could be compensating for a true shorter leg in attempts to lengthen it. We cannot sufficiently explain why we did not find that left anterior innominate rotations were associated with an ipsilateral longer leg, as we did with right anterior innominate rotations, perhaps because there were only a small number of participants who exhibited a left anterior innominate rotation.
Understandably, a left superior shear was associated with a left shorter leg in the supine position. Correcting functional LLD with an OMM technique, sometimes referred to as “the leg pull,” is a technique that osteopathic physicians who perform OMM are familiar with. This finding validates the leg length assessment techniques used in OMM practice, promotes routine leg length assessment for those who exhibit small LLDs, and reaffirms that visualization of the whole person is of utmost importance. Notably, a right superior shear was not correlated with a right shorter leg in the supine position, possibly owing to the small number of participants who exhibited a right superior shear.
While pelvic dysfunctions have been associated with LLD in the literature, specific sacral dysfunctions have not, to our knowledge. The current study found that left-on-left sacral torsions are associated with a left shorter leg in the standing position. The type of sacral dysfunction that is associated with a shorter or longer leg does not seem to be specified in our review of the literature; rather, it generally states the antithesis of this finding—an anterior sacral base is associated with a shorter leg on the same side.
1(p301) A left-on-left sacral torsion would tend to exhibit an anterior sacral base on the right. Our findings are completely opposite to this where we found that a left-on-left sacral torsion (right deep base) is correlated with a shorter left leg. Although osteopathic physicians diagnose sacral dysfunctions, they do not usually quantify the severity of the dysfunction. Perhaps in patients with asymptomatic mild sacral torsions, the compensation affects different areas and manifests differently. Another explanation may be that asymptomatic sacral dysfunctions lead to LLD rather than the LLD leading to the dysfunction through a compensatory motion of the sacrum, pelvis, or lumbar spine. Further studies comparing different severities of torsions along with painful sacral dysfunctions vs asymptomatic dysfunctions may assist in further support of this phenomenon.
Although sacral declination may prompt osteopathic physicians who practice OMM to investigate for LLDs, a simple left-on-left torsion has not been previously shown to influence leg lengths, to our knowledge. Left-on-left sacral torsions occur frequently as part of the CCP. Our finding may suggest that minor leg length shortening can occur secondary to left-on-left sacral torsions, which may affect other structures in the lower extremities and warrant assessment of the lower extremities and leg lengths. These findings are consistent with those in the literature, in which small LLDs ranging from 1.5 mm to 6 mm have been shown to be symptomatic,
5 thereby influencing pelvic obliquity
11 and leading to patterns of imbalance that require treatment.
2 It has been suggested that the management of discrepancies less than 5 mm not be performed unless symptomatic,
2 but other recommendations suggest that patients with asymptomatic LLDs should be treated to prevent future symptoms.
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In relation to weight-bearing distribution, participants who exhibited a right anteriorly innominate rotation while standing bore more weight through their left lower extremity. Although no statistically significant relationships were found pertaining to standing leg lengths and somatic dysfunctions, perhaps this finding can be related back to the literature. A right anterior innominate rotation is associated with a shorter lower extremity as reported by many sources,
1,3,11,37 and then weight bearing through the longer leg is also supported by many studies, which have reported that individuals bear weight more through the longer extremity.
16,25,29-31,34,35 Participants who exhibited a longer right leg in a standing position tended to bear more weight through the right lower extremity, with a difference of 26% between extremities. In contrast, participants with a longer left leg bore more weight through the right lower extremity (the shorter leg); however, there was only a 16% difference in weight-bearing distribution between extremities in this example. Although these findings are notable, they were not statistically significant.
Most of the participants in the present study bore more weight through their right lower extremity (46%) than through their left (29%) or through both (25%). This finding seems to contradict previous findings on footedness, where most individuals have been thought to be right-footed,
36 with a more skilled right lower extremity and a more stance-dominant left lower extremity.