Facet spacing – quantifying the effect of posture on interfacet spacing

Facet Spacing 1

Facet spacing has been long thought and known as an indicator of arthritis…especially when the joint space width is reduced significantly. These zygapophyseal joints (facet joints) are two important joints that lie posterior to the anterior intervertebral disc. As dynamic disc height loss occurs, the facet spacing narrows and leads to mechanical compression to the hyaline cartilage.

Furthermore, when the disc is unstable, the facets aberrantly approximate one another and can cause pain if enough force in delivered to the structures to cause irritation to the nerves that either reside below the hyaline cartilage in the subchondral bone, or the facet capsule and synovial fold.

In 2008, a group of researchers led by Drake published a manuscript in Spine titled : The Influence of Posture and Loading on Interfacet Spacing An Investigation Using Magnetic Resonance Imaging on Porcine Spinal Units and looked inter-facet spacing as it related to posture and load history.

zygapophyseal joints

They concluded that posture played a factor on the injury mechanism of the facet joints. They found that flexion increased the spacing and extension decreased the spacing. Which seems like a reasonable conclusion. They reported a “posture-dependent injury mechanism as repetitive loading and flexed postures independently increased the spacing and twist angle.”

At Dynamic Disc Designs, we are committed to sharing important dynamic spine research that can help the professional in both the work-up and communication of clinical findings to the patient. Understanding the relationship of the dynamic disc to the facet joint in spine pain is paramount when looking at pain generators spatially. Our models help with this sense through a physical dynamic spine model that not only brings the real to life bit also and a fourth dimension of time.

An example of this is demonstrated in our multilevel cervical model. This model showcases a straightening of the lordotic curve which not only slightly increases the posterior aspect of the intervertebral disc but it also demonstrates how each facet joint parallelism alters.  That is, normally there should be symmetrical spacing across both plains of facing joint surfaces, but with a reduced cervical curve, joint facing symmetry becomes angular.  This can generate uneven mechanical pressure within the synovial joints of the neck.

Below is an example of joint plain asymmetry seen in a lumbar facet. As you can see, the top of the joint is ‘tighter’ than the bottom.

Facet Joint Arthritic

Using a dynamic model reveals these geometrical changes in a way that can make sense about new (and old) pain generators.

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