Tubular Endoscopic Transpedicular Diskectomy

32 Tubular Endoscopic Transpedicular Diskectomy

Ricardo B. V. Fontes, Manish Kasliwal, John O’Toole, and Richard G. Fessler

32.1 Introduction

Symptomatic thoracic disk herniation (TDH) is a relatively uncommon pathology that may present a significant technical challenge to treat because of the anatomical constraints of the narrow thoracic spinal canal, the necessity to minimize cord manipulation, and the frequently calcified nature of TDH. Laminectomy alone was historically associated with poor outcomes, so a variety of anterior and posterolateral approaches were developed to treat TDH, including the transfacet-transpedicular approach first described by Patterson and Arbit in 1978. This technique is especially amenable to minimally invasive concepts and can be very successfully performed through a tubular endoscopic approach.1,2,3,4,5

32.2 Patient Selection

Midline TDH causing thoracic myelopathy (Fig. 32.1) is the main indication for tubular endoscopic transpedicular diskectomy.

Absolute contraindication is purely paramedian TDH (a transpedicular approach is not necessary), and relative contraindications are broad-based TDH causing bilateral compression (it may require a bilateral approach) and intradural TDH.

32.3 Technique

32.3.1 Preoperative Planning

Preoperative planning includes MRI or CT myelogram of the thoracic spine. If MRI is done, then noncontrast CT of the thoracic and lumbar spines is performed to assess TDH calcification and localization (ribs, transitional lumbar levels).

Cardiac clearance is necessary to maintain blood pressure during the procedure.

Preoperative chest X-ray is obtained to count ribs, and lumbar spine X-ray is taken to confirm the number of lumbar vertebrae.

32.3.2 Anesthesia and Positioning

General anesthesia without neuromuscular blockade (Fig. 32.2) is used. Intraoperative neurophysiological monitoring is done with SSEP and EMG. The patient is positioned prone on a Wilson frame, with checks for ocular pressure or contact points.

Mean arterial pressure is kept above 80 mm Hg at all times.

Rail attachment for the retractor arm is caudal and opposite the surgeon.

32.3.3 Localization

Preoperative marking is done with radiopaque material or fluoroscopic localization is accomplished with multiple views (anteroposterior for counting, lateral for lower thoracic levels and ribs). Image guidance may be used with intraoperative acquisition (O-arm), especially if the TDH is calcified. Fluoroscopy or navigation is utilized throughout the procedure.

Fig. 32.1 Case example, a 45-year-old male with progressive spastic paraparesis. (a) MRI and (b) CT demonstrate a large, predominantly midline T7–T8 disk herniation. This is a good example of an ideal patient for an endoscopic transpedicular diskectomy. The herniation is slightly larger on the right.

32.3.4 Entry Point

The entry point is 2 to 3 cm off midline, on the side of the larger TDH component or worse symptoms. Cranial-caudal position at the level of the affected interspace is confirmed with fluoroscopy.

32.3.5 Skin and Soft Tissues

Local anesthesia uses lidocaine 2% with 1:100,000 epinephrine. Skin incision is made and the K-wire is inserted perpendicular to the skin (Fig. 32.3).

The initial contact point is the zygapophysial joint, then exploration proceeds medially and the guidewire is docked at the spinous process–lamina junction.

The initial tubular dilator is inserted and the K-wire is removed, followed by sequential dilation.