Thoracoscopic Approaches to Deformity Correction [1]

37 Thoracoscopic Approaches to Deformity Correction [1]

Leok-Lim Lau and Hee-Kit Wong

37.1 Introduction

The thoracoscopic approach represents a physiological approach to adolescent idiopathic scoliosis with a single, structural, main thoracic curve and classical thoracic hypokyphosis. The approach utilizes the natural body cavity via strategically placed portals to assess the vertebrae, with the potential to save levels needed for instrumentation, to improve thoracic kyphosis, and to preserve the posterior spinal muscle complex. While the learning curve is steep, the following guide facilitates familiarity with the process.

37.2 Preoperative Planning

Thoracoscopic deformity correction can be considered when the scoliotic curves have the following characteristics:

• Single and right-sided structural thoracic curves. In patients with adolescent idiopathic scoliosis, they are classified as Lenke 1 curves.

• The thoracic curve is flexible and bends down to less than 45°.

• The end vertebrae (the most tilted vertebrae on X-rays) situate within T4 to L1 inclusively.

• Thoracic kyphosis is less than 40°.

The contraindications to the procedure include:

• Patients unable to tolerate or to achieve satisfactory single-lung ventilation, especially patients with pre-existing restrictive lung diseases or right heart failure

• Previous thoracotomy or pleural adhesion

Full-length posteroanterior (PA) lateral erect and PA bending spine X-rays, and/or bolster films, are essential for evaluation and surgical planning.

37.3 Position and Anesthesia

With patient in a supine position, single-lung ventilation is achieved with a double-lumen endotracheal tube. The ideal position of the tube is shown (Fig. 37.1). Malposition may result in hypoxemia and hypercarbia. The tube position is verified with bronchoscopy both before and after completion of the positioning. There is a tendency for the endotracheal tube to migrate further into the left bronchus on turning the patient from the supine to left lateral position.

The patient is turned to lie on the left lateral side on a standard radiolucent operating table, such as the Amsco table (Steris Corporation, Mentor, OH), with an axillary roll (Fig. 37.2). The table is bent at the midsection to open up the interval between the rib cage and the pelvis, and to facilitate clearance between the rigid telescope and camera from the pelvis during surgery.

The neck is supported and maintained in a neutral position. The right shoulder and elbow are flexed at 90° and are supported on an arm rest. Adequate access to the third rib on the right lateral chest wall should be checked by palpation of the rib. The left upper limb is flexed and supported. The left hip and left knee are flexed, while the right lower limb is kept straight, with a pillow in between the lower limbs. Additional straps can be used to stabilize the patient’s position and to prevent excessive rolling movement.

Pressure areas, such as elbows, knees, and ankles, are padded.

Fig. 37.1 Successful selective left lung intubation is imperative to achieve adequate ventilation in the presence of a completely empty right lung. (a) Endotracheal tube position is confirmed with the bronchoscope. (b) The intended position and (c, d, e) unintended positions are shown.

Fig. 37.2 The patient is in the left lateral position. The ribs are marked, starting from the most caudal floating rib.

37.4 Portals of Entry

The ribs are identified by palpation of the last floating rib, and are marked accordingly. Useful surface anatomy is that the angle of the scapula overlies the fifth rib.

Four portals are required. The portals are chosen with the aid of preoperative radiographs. Typically, the portals are situated along the third, fifth, seventh, and ninth ribs or, instead, along the fourth, sixth, eighth, and tenth ribs. The portals cover the curve from end vertebra to end vertebra (Fig. 37.3). An ideal portal sits directly in line and perpendicular to the midlateral part of the vertebral body. Fluoroscopy is used to assist in locating the point along the rib, taking into consideration vertebral body rotation (Fig. 37.4, Fig. 37.5). For example, at the upper thoracic portal, fluoroscopy is usually in a neutral position; at the midthoracic portals, 10 to 15° of rotation may be required at the apex of the curve, depending on the axial rotation of the vertebrae. Intermittent direct visualization via the portals allows better depth perception at the surgical field (Fig. 37.6).

Fig. 37.3 Planning so that the thoracoscopic portals span the end vertebrae of the scoliotic curve. (a) In this case, the curve spans the third to tenth ribs. (b) Inline placement of portals on alternate ribs (third, fifth, seventh, and ninth) is usually adequate, as the lower ribs are more flexible.

Fig. 37.4 An ideal portal sits directly in line at the midlateral part of the vertebral body. (a) At the upper thoracic portal, the rotation is first determined in the lateral position (b) under fluoroscopy. Spinous processes (red arrows) are verified to be in central positions on the vertebral bodies. (c) The fluoroscope is then turned into the lateral position, with the radiological marker pointing at the midlateral position on the vertebral body. (d) In mid portals, rotation of 10 to 15° may be required. The fluoroscope is positioned at 10° rotation (e,f) to center the spinous process in an anteroposterior view. (g) In the lateral position, the 10° rotation is accounted for. (h) The radiological marker is then positioned over the midlateral part of the vertebral body. This marks the ideal entry point for the portal.