Costotransversectomy

The spinal canal is anatomically narrowest at the thoracic level. Small lesions anterior and lateral to the spinal cord in this region tend to manifest with overt pain and neurologic symptoms. The herniated thoracic disk is one such classic pathology. Direct dorsal approaches are blind to such lesions and necessitate manipulation of the spinal cord with unforgiving sequelae of neurologic decline postoperatively. Therefore, ideal surgical treatment options must seek to increase the diameter of the access corridor to the lesions without manipulation of the spinal cord. The costotransversectomy or posterolateral approach is a versatile and less morbid approach that remains commonly used, with far less chance of spinal cord injury.

The costotransversectomy or posterolateral approach to the thoracic spine was initially developed to treat Pott’s paraplegia after posterior approaches yielded high rates of neurologic decline. ¹ Originally described by Menard and popularized by Capener, the costotransversectomy approach has undergone numerous modifications. ¹ This approach allows access to anterior and laterally located pathologies of the spinal canal. Specifically, the approach allows access to the posterior vertebral body, intervertebral disk, anterior and lateral epidural space, and intervertebral foramen ( ▶ Fig. 27.1).

Fig. 27.1 Axial view of a thoracic vertebra. The maximal exposure afforded through the costotransversectomy approach involves removal of the lamina, pars interarticularis, facets, transverse process, costal head, and posterolateral vertebral body.

27.2 Patient Selection

Centrolateral and lateral pathologies of the spinal canal are amenable to costotransversectomy. ¹^, ²^, ³ In particular, centrolateral and lateral disk herniations, compression fractures, fracture dislocations, lateral epidural lesions, and intervertebral foramen lesions can be treated ( ▶ Fig. 27.2). This approach can also be used to obtain a biopsy specimen to direct antimicrobial therapy or for tumor histology.

Fig. 27.2 Expanded operative view revealing access to the vertebral body (burst fracture and bony lesions), intervertebral disk (herniated nucleus pulposus), and nerve root (peripheral nerve tumor).

Numerous approaches have been described, in addition to costotransversectomy, for accessing disk herniations, including the transpedicular, lateral extracavitary, and transthoracic approaches. ¹^, ²^, ³ The morbidity associated with the transpedicular approach is similar to that for costotransversectomy; however, the lateral extracavitary and transthoracic approaches, developed to gain access to anteriorly located pathologies of the thoracic spine, require a more extensive dissection and potentially single-lung ventilation, respectively. Certainly, these procedures are more demanding for the patient, and the preoperative health of the patient should be thoroughly evaluated.

27.3 Preoperative Preparation

The preoperative evaluation of the patient focuses on the ability of the patient to tolerate anesthesia and prone positioning. Consultation with an anesthesiologist is particularly helpful in patients with significant comorbidities, especially cardiopulmonary ones. The correct level must be identified, with certainty, through the use of anteroposterior and lateral roentgenograms or computed tomographic scans. Image guidance with navigation may be used for accurate lesion localization, as well as subsequent instrumentation. Somatosensory and motor evoked potential monitoring is variably used. ³ A pediatric endoscope may be helpful in assessing progress in removal of anteriorly located pathologies.

27.4 Operative Procedure

An intravenous prophylactic antibiotic cefuroxime (1.5 g) is administered at least 30 minutes before incision. Intermittent pneumatic compression devices are applied. The patient is intubated, and general endotracheal anesthesia is induced. An indwelling urinary catheter is placed. Adequate venous access is ensured. Arterial line placement depends on the patient’s preoperative health and the pathology being treated; a vascular lesion or tumor could potentially lead to a significant blood loss. The patient is subsequently positioned prone on chest rolls or a radiolucent Wilson frame (Erothitan, Suhl, Germany) ( ▶ Fig. 27.3). The procedure may be performed with the patient prone or with the table tilted 20 to 30 degrees, elevating the side with the pathology. All pressure points are padded. Special attention is paid to avoiding pressure on the patient’s eyes during a long period of prone positioning. The upper limbs are positioned at 90 degrees both at the shoulder and the elbow to prevent stretch and compressive neuropathies.

Fig. 27.3 Ideal patient positioning is prone on chest rolls with the table rotated toward the pathology.

Identification of the pathological level is performed using fluoroscopy, radiography, or image guidance with stealth navigation. ⁴ Emphasis is placed on identification of the correct rib because the head articulates with the articular cavity formed by the intervertebral fibrocartilage and the adjacent vertebrae. For example, the head of the sixth rib articulates with the T5–6 disk space. This relationship holds true throughout the thoracic spine, with the exception of the 11th and 12th ribs, which articulate just below their corresponding disk spaces. Therefore, intraoperative identification of the rib leading to the level of interest is essential, and the procedure should not progress until the appropriate level has been identified.

For midline pathologies, the approach side may be chosen according to the surgeon’s preference. Otherwise, incision is made on the side correlating to radiographic pathology and symptoms. Theoretically, the risk of injuring the artery of Adamkiewicz is higher with a left-sided approach because it usually anastomoses with the anterior spinal artery by entering from the left intercostal vessels between T8 and L2; however, this increased risk has not been borne out in the literature. Furthermore, sacrifice of the intercostal vessels is rarely required. Various locations for incisions have been used, including median, paramedian, costal, and T-shaped ( ▶ Fig. 27.4). The median and paramedian incisions may be straight or curved. Incision type and location are based on exposure required for the location and extent of pathology. The incision should be planned to avoid previously irradiated skin.