Wednesday, September 23, 2009

Viewing end plate from injury prospective

* This following information must be seen in the light of my previous 2 posts especially the last post. This class ends the series.

1. The vertebral body & the end plate:

According to Prakash et al, many factors decide the integrity of the body of the vertebra. Gross design of the vertebral body is one of the most important adaptations for axial loading. The body of the vertebra is inter-segmental in origin, which results in dual vascular and nerve supply, both from superior and inferior aspects of the body. The vertebral body ossifies from 3 primary centers, one for centrum, which will form the major portion of body, and the other two for neural arches. The cartilaginous growth plate is mainly responsible for the longitudinal vertebral growth.

2. Intra-structural strength variation of end plates with specific reference to lumbar & sacral regions:

Many studies indicate that some regions of the vertebral body may be stronger than others. Hence the failure strengths are different in different part of the end plate. Working in end plate strength of lumbar & sacral region Grant et al (2001) & Hou et al (2009) found that:

1. Posterolateral regions being stronger (parts closest to the pedicles are the strongest) and stiffer than the anterior and central regions. The central regions were porous, as the fused trabeculae and peripheral regions had fewer and smaller pore structures.

2. Sacral and inferior lumbar endplates were both found to be stronger than the superior lumbar endplates.

Grant et al’s study (2001) reveals interesting aspects of end plate strength i.e. significant regional strength and stiffness variations in the lumbar and sacral endplates & the center of the bone is the weakest part of the lumbar endplates and it is also not the strongest region of the sacral endplate.

Similarly Hou et al’s study reveals further that failure load distribution did not change with the BMD (bone mineral density) decrease. There is inter-segmental variation in failure strength noted in a same region for example failure loads of the lumbar endplates showed an increasing tendency from L1-L5 segments. They concluded the differences in the anatomic structures of different regions are the histologic foundation of biomechanical properties of lumbar endplates.

Relationship of disc generation & end plate strength:

In another study Grant et al (2002) reveal that increased disc degeneration is associated with an overall failure load decrease in the inferior lumbar endplates. The strength in the central regions of the superior endplates was reduced with increasing degeneration, but this was not observed peripherally. Further locations of the strongest regions of the endplate did not change with either bone density or disc degeneration i.e. postero-lateral regions remain the strongest part of end plate under these condition.

Effect of endplate removal on the structural properties:

Recent reports indicate that there is a significant effect of end plate removal on the local structural characteristics of the vertebral end plate. Oxland et al reported with end plate removal, the mean failure load decrease to about 33% of the intact failure load & there is a trend toward greater decreases posteriorly. Further with end plate removal, the mean stiffness also decreases substantially with the greater decrease laterally.

Reference:

1. Prakash; Osteoporos Int. 2007 Jul;18(7):891-903. Epub 2007 Apr 3.
2. Grant et al; Spine (Phila Pa 1976). 2001 Apr 15;26(8):889-96.
3. Hou et al; Spine (Phila Pa 1976). 2009 May 20;34(12):E427-33.
4. Grant et al; J Orthop Res. 2002 Sep;20(5):1115-20.
5. Oxland TR et al; Spine (Phila Pa 1976). 2003 Apr 15;28(8):771-7.
6. Lowe TG et al; Spine (Phila Pa 1976). 2004 Nov 1;29(21):2389-94.

Class in disc pain-3 (end plate- an anatomic region often unexplored)


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