Posterior Fusion for Idiopathic Scoliosis



Posterior Fusion for Idiopathic Scoliosis


Craig M. Birch



Operative Indications



  • Primary indication: Progressive thoracic curve greater than 50° or thoracolumbar/lumbar curve greater than 40°


  • Pain is not an indication for surgical intervention without further evaluation and treatment related to pain


Preoperative Imaging



  • Typical adolescent idiopathic curve pattern is right thoracic with left lumbar and potential left upper thoracic curve (Figure 3.1)


  • Typical curves: Right thoracic, left lumbar



    • Preoperative imaging should consist of standing posteroanterior (PA) and lateral full spine radiographs or EOS imaging


    • Right and left bending films to adequately determine flexibility and Lenke criteria (Figure 3.2)


  • Atypical curves: Left thoracic, kyphosis, severe coronal decompensation



    • Additional preoperative imaging is required and should include magnetic resonance imaging (MRI) of the entire spine to evaluate for neurologic anomaly, specifically tethered spinal cord, Chiari malformation, and syrinx (Figure 3.3)


    • Computed tomography (CT) is typically not used unless preoperative templating is required for navigation or for robotic assisted surgery




Positioning



  • Patient is intubated with bite block, orogastric (OG) tube, arterial line, and multiple large bore intravenous access established per anesthesia protocol. Foley is placed for urinary output measurement. Neuromonitoring leads attached for motor evoked potentials (MEPs), somatosensory evoked potentials (SSEPs), and electromyography (EMG)


  • Patient is flipped prone on the Jackson frame


  • Neck position should be checked to ensure in a neutral position. No additional flexion or extension


  • Arms positioned with shoulders abducted to 90°, elbows flexed to 90°, and wrists in neutral position


  • Arms padded with no pressure on the ulnar nerve


  • Back is then widely draped with 1000 drapes


  • Most surgeons have preferred prescrub of either alcohol followed by hydrogen peroxide or chlorhexidine which should include the periphery of the 1000 drapes


  • Wide prep consisting of chlorhexidine unless allergic and then Betadine. Border of the 1000 drapes should be included in both the prescrub and the prep


  • Spinous processes are then palpated, typically counting from most prominent C7 down to anticipate levels of fusion. Incision is drawn based on palpated landmarks. Ioban sticky drape is laid directly onto skin as last step








Surgical Approach


Posterior Exposure



  • Incision over the spinous processes of anticipated levels of fusion



    • Some surgeons scratch the skin followed by dilute epinephrine injection into the skin and subcutaneous tissue followed by sharp dissection down to the level of the posterior fascia. Others prefer incision to dermis and immediate use of electrocautery dissection down to posterior fascia. Effort should be made to minimize soft tissue dissection to avoid creating large dead space








Bony Dissection (Figure 3.4)



  • Spinous processes are identified and split using electrocautery


  • Cobb and electrocautery dissection down the spinous processes to lamina and then out to the transverse process


  • Interspinous ligament of the most cephalad level should be left intact. The fascia should be split off to each side so as to not disrupt the ligamentous attachment (Figure 3.5)













Technique in Steps


Facetectomy (Figure 3.6)



  • Facet joints are identified, and the capsule is removed using Cobb and electrocautery


  • Capener gauge or bone scalpel is used to remove the inferior articular facet exposing the underlying cartilage of the superior articular facet of the distal vertebral body


  • Facet joints will be more overlapped, and bone will be more dense on the concavity


  • Capener, curette, or burr is used to remove the articular cartilage

Jun 9, 2022 | Posted by in Reconstructive surgery | Comments Off on Posterior Fusion for Idiopathic Scoliosis
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