Lateral Intramuscular Planar Approach for Instrumentation/Stabilization L3 to Sacrum

Lateral Intramuscular Planar Approach for Instrumentation/Stabilization L3 to Sacrum



Abstract


The lateral intramuscular planar (LIMP) approach allows the surgeon unencumbered and relatively bloodless access to the transverse processes and pedicle region of the lower lumbar spine and sacrum. The plane is between the multifidus and the pars lumborum, the two main functional muscle groups at these level; it is oblique and j-shaped, in contradistinction to description in most anatomy texts.


Pedicle screw placement is facilitated, as the LIMP approach is angled precisely along the pedicle axis; minimal or no muscle retraction is necessary to “medialize” the screw. Transforaminal interbody spacers can be applied via the LIMP approach. Graft harvest, by iliac un-capping, is done with essentially no extension of soft tissue dissection.


The disadvantage of the LIMP approach relates to the need for midline decompression techniques, thus requiring a third (midline) exposure in such cases.


Keywords: multifidus, pars lumborum, aponeurosis of the erector spinae, transforaminal interbody, iliac un-capping



Your assumptions are your windows on the world. Scrub them off every once in a while, or the light won’t come in.


Isaac Asimov


7.1 Introduction


Wiltse 1 and others have described a paraspinal approach to the lumbar spine through a natural plane lateral to the multifidus and medial to the erector spinae musculature (latissimus thoracis and iliocostalis lumborum). This plane is often anatomically depicted as sagittal and vertically oriented to the sacrum. In reality, the long fibers of the erector spinae below L3 are represented by a superficial aponeurosis (deep fascia). True muscular fibers of the erector spinae at this level are mainly their pars lumborum components that run obliquely lateral to medial from the ilium to the transverse processes (TPs). The multifidus flares laterally into the ilium as well (more so than is usually depicted in anatomic texts). Thus, the plane between the multifidus and the pars lumborum component (of the longissimus thoracis) is oblique and J-shaped (see muscular anatomy, Chapter 2). This plane can be found most easily at the ilium between the attachments of the pars lumborum and the multifidus, the fibers of which differ visually in orientation. The multifidus attachment can overlap that of the pars lumborum sometimes, necessitating exploration under its lateral/superior edge in order to find the fatty lateral intramuscular plane above the inferior attachment of the pars lumborum. This plane is then easily developed down to the medial aspects of the TPs, enabling excellent exposure of the extraforaminal spine. 2


7.2 Clinical Presentation




  • Painful radiculopathy.



  • Incapacitating antigravity axial chronic low back pain.


7.3 Image Pathology




  • Evidence of excessive vertebral motion (“instability”) contributory to symptomatology (or potentially so).



  • Severe degenerative discogenic changes contributory to the axial antigravity pain (L3–S1).


7.4 Contraindications (Relative)




  • The lateral intramuscular planar (LIMP) approach is applicable mainly for pathology from L3 to S1.


7.5 Operative Technique


Midline or bilateral para-axial incisions (~4 cm laterally):




  • Dissection and clearance of the deep fascia in midline, then (in all but thinnest patients) lateral dissection through the subcutaneous adipose tissue to avoid extensive lateral uncovering of the deep fascia (▶ Fig. 7.1).



  • Dissection through the subcutaneous adipose tissue with exposure of the ilium and the attachment there of the aponeurosis of erector spinae (AES); incision with the cautery just through the AES exposing muscle underneath; incision is parallel to the ilium (diverging laterally) preserving residual leaf at the ilium for closure (note: for males, incision is as close to the ilium as possible; in females, incision is about 4 cm laterally with larger residual leaf of the AES; ▶ Fig. 7.2).



  • At palpable ilial drop-off, continue incision cephalad parallel to midline through both layers of the thoracolumbar fascia (and intervening adipose tissue).



  • Visualization of change in the muscle fiber appearance from homogenous medial to lateral (multifidus) to chevron appearance (pars lumborum; ▶ Fig. 7.2).



  • With two dissectors, explore the muscle transition area and identify the intramuscular plane between the multifidus (lateral shiny fascia) and pars lumborum. Adipose tissue is seen within the plane and extends down to the region of the juncture of the TPs and superior articular processes (SAPs). (Note: if there is difficulty finding the proper plane, then incision at the superior lateral attachment of the multifidus to the ilium will reveal lateral aspect of the adipose plane underneath; ▶ Fig. 7.3).



  • Explore through the deeper adipose plane to identify the medial aspect–appropriate TPs and clear these laterally for eventual grafting site.



  • Using cautery, expose the SAPs/lateral facet/pars at each level necessary for pedicle screw fixation and/or posterolateral grafting (▶ Fig. 7.4).



  • Closure with interrupted sutures of the AES and both layers of the thoracolumbar fascia.



    Fig. 7.1 Transadipose subcutaneous dissection laterally to expose the ilium and limit the dead space on top of the deep fascia.


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Dec 22, 2019 | Posted by in NEUROSURGERY | Comments Off on Lateral Intramuscular Planar Approach for Instrumentation/Stabilization L3 to Sacrum
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