The oblique axis is a diagonal axis that runs from the most superolateral aspect of the sacrum to the inferolateral aspect of the opposite side.The oblique axis is named left or right after the side that the superior part of the axis is on. This oblique axis is the axis in which torsions are engaged on. Motion that occurs during walking is around this axis. When weight is shifted from one side to the other the oblique axes switch from left to right and back repeatedly. This motion is called dynamic motion. The axis that is engaged is on the side in which the person is bearing weight
The somatic dysfunctions of L5 and the sacrum are related. The sacrum will rotate the opposite direction of L5, and L5 will be sidebended to the same direction as the sacral axis.
A seated flexion test determines the side of dysfunction if positive on one side. If the somatic dysfunction is a torsion, the seated flexion test is found on the opposite side of the oblique axis. In torsions, the sulci and the ILA on the same side will both be anterior or posterior when compared to the same anatomic structures on the other side.
In forward torsions, the sacrum rotation is on the same side as the axis. There are two dysfunctions in this category, left on left and right on right. L5 is neutral in forward torsions.
In backward torsions, the sacrum rotation is on the opposite side as the axis. There are two dysfunctions in this category, left on right and right on left. L5 is non-neutral (flexed or extended) in backward torsions. For example, a left on right dysfunction will have a + seated flexion test on the left and L5 will be flexed or extended.
In bilateral dysfunctions, the sacral base moves anterior (in flexion) or posterior (in extension). These dysfunctions occur about the middle transverse axis. The middle transverse is also the axis in which postural motion takes place. If someone bends forward, the base of the sacrum moves anteriorly around this axis.
Since the dysfunction is bilateral and both sides are equally affected the anatomical landmarks are symmetrical. This includes the ILAs and the sulci.
A bilateral sacral flexion dysfunction will have a negative seated flexion test and a negative spring and sphinx test. The ILAs and sulci are equal bilaterally, and the sacral base is rotated anterior around the middle transverse axis. This dysfunction is associated with an increased lumbar curve. Bilateral sacral dysfunction is the most common dysfunction of the sacrum in patients who have recently given birth.
A bilateral sacral flexion dysfunction will have a negative seated flexion test, a positive spring and a negative sphinx test. The ILAs and sulci are equal bilaterally, and the sacral base is rotated posterior around the middle transverse axis. This dysfunction is associated with a decreased lumbar curve.
In unilateral dysfunctions, the sacrum is shifted either anteriorly or posteriorly on a transverse axis. The sacrum can flex or extend on the right or left side. This leaves a total of 4 sacral dysfunctions in the unilateral category: left unilateral flexion, right unilateral flexion, left unilateral extension and right unilateral flexion.
In this unilateral dysfunction, the side affected will have an anterior, deep sulci and an inferior and posterior ILA. Additionally, the seated flexion test will be positive on the side of dysfunction, and the sphinx test will be positive. For example, a right unilateral flexion will have a deep sulci on the right, a shallow sulci on the left, a posterior and inferior ILA on the right and an anterior, superior ILA on the left.
In this unilateral dysfunction, the side affected will have an posterior sulci and an ILA that is superior and anterior. The seated flexion test will be positive on the side of dysfunction, and the spring test will be positive as well. For example, a left unilateral extension will have a deep sulci on the right, a shallow sulci on the left, a shallow, posterior ILA on the right and an anterior, deep ILA on the left.
Picmonic's rapid review multiple-choice quiz allows you to assess your knowledge.
*Average video play time: 2-3 minutes
Unforgettable characters with concise but impactful videos (2-4 min each)