Minimally invasive lumbar decompression





Introduction


Minimally invasive lumbar decompression (MILD) is an image-guided approach used in the treatment of symptomatic lumbar central spinal stenosis. This procedure is a good option for patients who are not responsive to conservative or injection therapy and either do not want an open surgical decompression or are not good surgical candidates. Lumbar spinal stenosis (LSS) is a degenerative disease of the aging spine. LSS is the most common indication for spinal surgery in patients above the age of 65.


Indication


The MILD procedure is indicated for patients with symptomatic central LSS due to ligamentum flavum hypertrophy. It is not meant for patients with symptoms due to lateral recess spinal stenosis. It is also not indicated if stenosis is due to any cause other than ligamentum flavum hypertrophy (e.g., anterolisthesis or disc protrusion). Indications and contraindications are summarized in Table 6.1 .



TABLE 6.1

Indications and Contraindications for MILD Procedure










Indications Contraindications



  • Ligamentum hypertrophy preferably >4 mm 2



  • Central spinal stenosis



  • Symptoms of neurogenic claudication



  • No sensory or motor defect




  • Coagulopathy



  • Surgery at that level



  • Severe scoliosis



  • True allergy to dye



  • Only back pain


MILD , Minimally invasive lumbar decompression


Patient selection


Patient selection is the most important part of the MILD procedure ( Table 6.2 ). The patient should have symptomatic central LSS from ligamentum flavum hypertrophy ( Fig. 6.1 ).



TABLE 6.2

Patient Selection Factors
























Primary indication Neurogenic claudication in the presence of radiologically proven ligamentum flavum hypertrophy
Neurogenic claudication symptoms


  • Pain



  • Numbness



  • Weakness



  • Tingling in low back, buttocks, and legs initiated by standing, walking, or lumbar extension that is relieved by sitting or forward flexion.

Symptom characteristics


  • Symptoms do not follow a dermatomal pattern (a hallmark of foraminal or lateral recess stenosis), but the two distinct etiologies can coexist



  • The symptoms tend to be symmetrical, usually above the knee; this proximal distribution helps to symptomatically differentiate lumbar stenosis from vascular claudication

Physical examination Unremarkable; the presence of sensory or motor deficits should prompt surgical evaluation
Imaging


  • Imaging is required for the definite diagnosis of LSS



  • A systemic review found CT or MRI equally accurate in the diagnosis of LSS



  • MRI is preferred as ligament hypertrophy can be easily measured

Radiological criteria for spinal stenosis There are several criteria used, but anterioposterior spinal canal diameter of <10 mm or an area of <70 mm 2 is generally considered diagnostic
Diagnostic criteria used in various MILD trials


  • Neurogenic claudication for at least 3 months



  • Ligamentum flavum thickness of >2.5 mm



  • Anterolisthesis of 5 mm or less



  • Absence of spinal instability


LSS , Lumbar spinal stenosis



Fig. 6.1


Thickened ligamentum flavum outlined in red on axial view MRI lumbar spine.


Setup


Table 6.3 describes some important aspects of the procedure setup.



TABLE 6.3

Procedure Setup












Anesthesia


  • Mild to moderate sedation



  • Deep sedation or general anesthesia should be avoided unless performed with nerve monitoring

Positioning


  • Prone position with flattened or minimized lumbar lordosis



  • No pressure on the belly or chest for ease of breathing for the patient

Antimicrobial actions


  • Appropriate antibiotic is given before the start of the procedure



  • The target area is scrubbed with 2%–3% chlorhexidine/70% isopropyl alcohol solution, which is allowed to dry for 3 minutes



  • Full surgical drapes are used, and the target skin area is covered with an antimicrobial incise drape (e.g., Ioban)



Procedure



Aug 6, 2023 | Posted by in ANESTHESIA | Comments Off on Minimally invasive lumbar decompression

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