Para spinal Approach to Lumbar Spine

Relevant Anatomy:

The Erector Spinae are large superficial muscles below the deep lumbodorsal fascia arising from the iliac crest, the thoracolumbar processes, and the aponeurosis on the sacrum. This muscle makes a confluent mass in the lower lumbar region but can be discerned into three muscles in the upper lumbar region: the Illiocostalis, the longissimus, and the spinalis. The multifidus are a series of the small muscles seen prominently only in the lumbar spine. These originate from the mamillary process of the superior facet and insert of spinous processes medially about two segments higher. The most lateral muscle is the Quadratus lumborum originating from the iliac crest and illio lumbar ligament, it runs obliquely and inserts into the 12th rib and the transverse process of upper four lumbar vertebrae. The Interspinalis muscle are pair of deep muscles which are present between the two spinous process, similarly the inter transversii are present bilaterally between the transverse process.

Positioning;

Prone Position.

Prevent abdominal pressure as it leads to an increase in spinal venous pressure and bleeding intraoperatively.

Bolsters or horseshoe shaped pheasant cushion may be used.

Pad the knees with foam rubber and shin and anterior border with pillow.

Free chest expansion and no pressure on abdomen is the key

Exposure:

Incision: A curved para spinous incision about three finger breadth from the midline centered on the vertebral levels that need to be exposed.

Adrenaline infiltration: Depends on surgeon’s preference, as the duration of action is limited. A 1: 500,000-epinephrine solution in saline can be injected into subcutaneous tissue.

The skin and subcutaneous tissue is cut till dorsolumbar fascia is reached. The Fascial incisions are made at about the same lateral to the spinous process, approximately three fourth of the way out laterally to sacrospinalis. The muscle mass can be bluntly dissected using fingers.

Palpate the transverse processes and the posterosuperior iliac spine, which is present in the inferior aspect.

The facet joints present medially can then be exposed and soft tissue cleared from it.

The fusion bed can then be prepared at desired levels.

Potential Complications:

Nerve root Damage: The traversing nerve root lie anterior to the transverse process, however they risk a chance of injury if the dissection is inadvertently carried anterior to the transverse processes or the intervening intertransverse membrane.

Clunial Nerve Damage.