29 Anterior Correction of Thoracic Scoliosis Using the Kaneda Anterior Scoliosis System (KASS)

Thoracic scoliosis is defined as scoliosis with its apex of the major curve located within the T2 to T11-T12 disc levels. Standing posteroanterior (PA) and lateral x-ray films are utilized to determine the magnitude of the curvatures and spinal balance (Fig. 29–1). Physical examinations to clarify waist asymmetry, bilateral shoulder height asymmetry, and rib hump deformity are performed. Flexibility of the curvature is determined by preoperative bending films and traction x-ray films.

Indications for Surgery

1. Single thoracic curve (King type III and IV curves) is best indicated for this procedure.

2. Curve magnitude more than 50 degrees.

3. Adult patients with severe thoracic scoliosis.

Contraindications

1. Single anterior correction surgery is not indicated for patient with double major curve pattern (King type I and true type II curves). However, false double major curve (type II curve with flexible and small lumbar curve) can be treated by selective major thoracic curve correction.

2. Scoliosis with structural high thoracic curve (type V, etc.)

Advantages of Anterior Approach for Thoracic Scoliosis

1. Short fusion

2. Three-dimensional correction of the deformity

3. Improved cosmesis and rib hump

4. Avoids intervention to the back muscles of the spine

5. No skin protrusion caused by implants as seen in the posterior instrumentation procedure

Disadvantages

1. Spinal balance decompensation in a false double major curve (type II)

2. Shoulder height asymmetry with a structural high thoracic curve

3. The associated morbidity of a thoracotomy

Procedure

Positioning of the Patient

1. The patient is positioned on the flat table with the convexity of the curve up (lateral decubitus position).

2. The head is placed on a pillow with the cervical spine straight.

3. An axillary pad is placed to prevent circulatory disturbance of the upper extremity.

4. A pillow is placed to secure the space between the fibula head and table to prevent pressure on the peroneal nerve.

5. The scapula and arm elevated and secured proximally.

Skin Incision

1. Skin incision is made along the rib of the uppermost vertebra or one above it where instrumentation is planned. In thoracic scoliosis, this is usually the fifth, sixth, or seventh rib.

2. To avoid skin incision crossing the breast, a skin incision is placed obliquely from the angle of the rib to be resected, posteriorly to the costal cartilage of the 10th or 11th rib, anteriorly. This incision allows exposure of the vertebra as distal as T10 or T11.

3. To approach T12 or more distally located vertebrae, additional entry site needs to be prepared. Usually, an additional entry site is placed on the 10th or 11th rib. No additional skin incision is required, because the 10th or 11th rib can be approached subcutaneously.

4. Through this site, lower thoracic and, by posterior partial transection of the diaphragm and through the retroperitoneal approach, upper lumbar vertebrae can be accessed.

Exposure

1. The serratus anterior and latissimus dorsi muscles are transected in a plane parallel to the course of the rib to be transected. A cuff of serratus muscle is left on the lower pole of the scapula to facilitate its reattachment when the wound is closed and stay sutures should be placed on the cut edges of the muscles attached to the scapula for latter reattachment.

2. The scapula is displaced superiorly and rotated to expose the underlying rib.

3. The rib periosteum is incised, and stripped subperiosteally from the rib. The rib is cut as far posteriorly as possible. The anterior portion of the rib is resected 3 to 5 cm distal to the costochondral junction.

4. The pleura is incised at the bed of the resected rib superiorly and distally for the length of the wound to gain access to the thoracic cavity. A retractor is used to open and hold the ribs apart during surgery.

5. The segmental vessels are identified and ligated at the levels where instrumentation is planned.

6. The intervertebral discs and the intervening cartilage plates located among the fusion range are removed. In a stiff, large thoracic curve, mobilization requires resection of the entire annulus to the opposite concave side.

Related posts:

Posterior Cervical Laminectomy and Fusion Odontoid Fixation Posterior Scoliosis Correction: King Type V/ Double Thoracic Curves Anterior Cervical Corpectomy Anterior Lumbar Interbody Fusion Total Lumbar Disc Replacement Using the SB III Charite Prosthesis

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