of the Posterior Lumbar Muscles: Study of Lumbosacral Malformations and the Extraforaminal Approach (ELIF)


Fig. 1

CT-scan lateral and axial views L4–L5. Measurement of the surfaces of Multifidus and the three posterior muscles (M + L + IC) with horizontal cross-section




Table 1

True levels


































 

Normal lumbar spine


Lumbar spine with sacralization


False or non-functional disc


S1S2


L5S1


Free disc


First disc


L5–S1


L4–L5


Second disc


L4–L5


L3–L4


Third disc


L3–L4


L2–L3


Fourth disc


L2–L3

 


Instead, a disc, under a vertebra completely or partially attached to the pelvis is a false or non-functional disc. Usually, this disc is S1S2.


The surface of the posterior muscles has been measured at the level of the four last “free discs” and, if necessary, the “non-functional disc ”, with horizontal cross-sections, that go through the posterior part of the inferior endplate.


These horizontal cross-sections are studied from native slides acquired during CT scan and not with cross-sections made in the axis of the disc.


The axis of the disc varies with lumbar lordosis. The cross-sections overlap and represent a shifting surface of the muscles. Instead, horizontal cross-sections, by definition, are parallel and represent a specific surface of the muscle.


Two muscular surfaces have been measured: the surface of the Multifidus (MS) alone and the global surface (GS) of the three muscles (M + L + IC). The ratio of the two surfaces (MS/GS) has been calculated.


The vertebrae have been named in accordance with classic data:



  • Five free lumbar vertebrae



  • The L3 transverse process is longer, larger and more horizontal than any other



  • Instead the L4 transverse process is short, slender with an oblique ascending slope



  • The innominate line crosses the disc L5S1 in its posterior part, on the lateral X-ray



  • The sacral slope (S1 endplate) is 38° (± 8°)



  • The superior attachment of the psoas muscle is at T12L1 level


Results


The results are reported in Table 2.



  • Those of a lumbar spine that has been seen as normal



  • Those of lumbar spine with lumbosacral malformation




Table 2

Surfaces ratio of the lumbar posterior muscles at every disc level










































$$ \mathrm{Surfaces}\ \mathrm{ratio}=\frac{\mathrm{Multifidus}}{\mathrm{Multifidus}+\mathrm{Longissimus}+\mathrm{Iliocostalis}} $$

 

Normal lumbar spine


Sacralization


Number of spines


59


31


False or non-functional disc




Free disc


First disc


95% (80–100%)


64% (43–81%)


Second disc


51% (43–66%)


37% (33–42%)


Third disc


34% (27–39%)


20% (15–27%)


Fourth disc


18% (15–21%)


15% (12–18%)

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Apr 25, 2020 | Posted by in ORTHOPEDIC | Comments Off on of the Posterior Lumbar Muscles: Study of Lumbosacral Malformations and the Extraforaminal Approach (ELIF)
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