10.1 The Ventral and Lateral Approaches to the Cervical and Upper Thoracic Spine

The traditional ventral approach to the cervical spine provides a wide exposure of the ventral cervical vertebral bodies. ¹ For the purpose of instrumentation placement, this approach provides an appropriate exposure of the spine.

Commonly, a nearly horizontal incision placed along a skin crease is used. If a lengthy exposure of the ventral cervical spine is desired, a diagonal incision along the ventral border of the sternocleidomastoid muscle is used. Blunt and careful sharp dissection is accomplished along the medial border of the sternocleidomastoid muscle, between the trachea and esophagus medially, and the carotid artery, jugular vein, and vagus nerve laterally. Stretch and compression of the recurrent laryngeal nerve can be minimized by careful sharp dissection and by the use of low endotracheal tube cuff pressures. ² Subperiosteal dissection, beginning at the midline and extending laterally to the most lateral extent of the vertebral body, is performed bilaterally and past the rostral and caudal extent of the planned vertebral exposure as defined by radiographic localization (Fig. 10.1a). ^{1 ,​ 3 ,​ 4} Great care is taken to minimize sympathetic trunk injury. This structure is more medial and so more vulnerable in the low cervical spine. ⁵ Two points are crucial: (1) the attainment of a more-than-adequate exposure, both laterally and rostrally–caudally and (2) the maintenance of this exposure with appropriate self-retaining retraction. The former is achieved via meticulous sharp and blunt dissection with minimal soft tissue stretching. The latter can be achieved with either of two types of retractor system: (1) a patient-mounted system or (2) a table-mounted system. The former causes an asymmetric and often excessive application of pressure to the soft tissues. The latter may eliminate this complication while providing greater exposure. As with all instrumentation techniques, a thorough knowledge of the anatomical and biomechanical nuances of implant–bone interface sites is imperative. In this regard, minimization of the incidence of recurrent laryngeal nerve injury is critical. A knowledge of anatomy is key. The incidence of recurrent laryngeal nerve injury is higher in more extensive and redo cases. There appears to be no difference in its incidence related to the side of exposure, as was once thought. ⁶ Careful sharp dissection can also minimize the incidence of dysphagia, which increases with revision surgery and with levels operated upon. ⁷ The etiology of postoperative dysphagia is multifactorial and related to the disruption of swallowing function during several phases. An understanding of such increases success with treatment and, obviously, prevention. ⁸

Ventral cervical spine exposure via the ventral approach does not result in significant deinnervation of muscles. Although the longus colli muscles are injured, they are injured symmetrically along the midline raphe. Furthermore, their importance in the prevention of spinal deformity is not known, but most likely is minimal.

Lateral exposure of the cervical spine can be gained via an approach described by Verbiest. ⁹ Usually, passing through the same tissue planes as depicted in Fig. 10.1a, this approach is used to gain access to the most lateral aspect of the spine, overlying the vertebral arteries. Retraction of the sympathetic chain medially, with the longus colli muscle, often preserves the function of this structure (Fig. 10.1b). ¹⁰

Ventral exposures of the high cervical spine to treat a variety of pathologies can be undertaken. The approach varies, depending on the pathology being addressed. Such can, in fact, be used for decompression of the atlantoaxial vertebral artery ¹¹ or for an extreme lateral approach for resection of ventral pathologies such as those related to or involving the dens. ¹²

Ventral exposure of the upper thoracic spine can be attained via a sternum-splitting (median sternotomy) approach (Fig. 10.1c). ¹³ However, with its extensive and invasive nature, this approach may not be necessary in many cases. The exposure is limited by vascular structures. A more limited (less invasive) manubriectomy (and medial clavicle resection) approach gains essentially the same access to the spine (Fig. 10.1d). ^{10 ,​ 14} Teng et al described a low suprasternal approach, with or without manubriotomy and sternotomy, to such lesions. They also described the indication for such extended approaches. They emphasize the importance of magnetic resonance (MR) imaging at the cervicothoracic junction to assess the geometry of access and exposure before surgery. ¹⁵ A ventrolateral trans–first rib approach may also be considered. ¹⁶ The paucity of clinical experience with the latter, however, is a limiting factor regarding its use.

10.2 The Ventrolateral Transthoracic and Extrapleural Thoracotomy Approaches

The ventrolateral approach to the thoracic spine can be used for ventrolateral exposure from about T5 to T10. Intercostal muscle incision, with or without rib resection, provides access to the thoracic cavity. Careful lung retraction provides a wide view of a lengthy portion of the spine. Postoperatively, the remaining ribs may be bound together by strong circumferential sutures to augment chest wall stability (perhaps at the cost of an exaggerated tendency toward spinal deformation and potential risk for intercostal nerve injury, with an accompanying intercostal neuralgia).

Exposure from the left is impeded by the aorta, and exposure from the right is impeded by the vena cava. These structures pose risks related to vascular injury and operative exposure (Fig. 10.2a). The ventrolateral approach, in addition, entails problems with visualization of the entirety of a ventrally placed implant. Furthermore, the dural sac is not decompressed until all ventral structures have been removed. This may create a slight hazard with respect to dural sac decompression operations. ³

The transthoracic exposure, by definition, is asymmetric. The intercostal muscle incision minimally disrupts stability. Rib resection, with the postoperative binding together of the remaining ribs, predisposes the patient to a spinal deformation about the coronal plane (scoliosis). In some cases, it may be appropriate to consider the use of intraoperative stabilization techniques to augment stability.

The extrapleural thoracotomy approach is depicted in Fig. 10.2b. ¹⁷ This approach has a theoretical advantage regarding pulmonary complications and provides nearly the same exposure as the thoracotomy approach. The extrapleural thoracotomy provides a significant advantage at the thoracolumbar junction. Use of the extrapleural thoracotomy in this region allows the diaphragm to be displaced forward, as opposed to being incised, which is required in the transdiaphragmatic approach to the same region (see the following).

10.3 The Transdiaphragmatic Approach to the Thoracolumbar Spine

The transdiaphragmatic approach to the spine allows a ventrolateral exposure of the thoracolumbar junction. Other than the extrapleural thoracotomy and the lateral extracavitary approach, the transdiaphragmatic approach is the only approach that provides a ventral exposure of this region of the spine (Fig. 10.3). ³

Rib resection may be required for this approach. The lower ribs, however, have a minimal effect on stability.

10.4 The Ventrolateral Extraperitoneal Approach to the Upper and Midlumbar Spine

The ventrolateral extraperitoneal approach to the upper lumbar spine is essentially the same approach used to gain access to the sympathetic chain for sympathectomy in the lumbar paravertebral region. ^{3 ,​ 4 ,​ 18} This exposure provides access to the ventrolateral spinal canal from L2 to below the pelvic brim. The dissection proceeds in an anatomical manner by splitting incisions through the external oblique and transversus muscles, along the muscle fibers of each muscle layer, into the retroperitoneal space and then to the spine. If high lumbar exposure is necessary, the diaphragmatic crus may be separated from the anterior longitudinal ligament of the vertebral column. The sympathetic chain can be visualized in the groove between the psoas muscle and the vertebral body.

A major advantage of this approach is the straightforward nature of the exposure, which is familiar to most spine and vascular surgeons. However, it provides a disappointingly narrow longitudinal exposure. This exposure is limited rostrally by the crus of the diaphragm and caudally by the pelvic brim. This approach also makes it difficult to expose the neuroforamina without psoas muscle retraction—which is difficult to begin with—or resection. Exiting lumbar nerve roots, which pass through the psoas muscle, may be injured during this approach. A thorough knowledge of the regional anatomy and care to protect the neural elements are imperative. The advantages and disadvantages of this approach are similar to those of the ventral transthoracic approach (Fig. 10.4). In recent years, less invasive and mini-open approaches have been employed with success. The preservation of the musculature is key to decreasing morbidity. ¹⁹

This exposure asymmetrically deinnervates and injures muscle, albeit minimally. A unilateral injury to the psoas muscle from lateral subperiosteal exposure along the vertebral body can cause hip flexor weakness. It may also affect spinal stability directly through the disruption of muscle spinal support (asymmetrically), and indirectly through induced hip flexor weakness.