Posterior and Posterior Lateral Techniques for Thoracic Disc Herniations

Background

Thoracic disc herniation (TDH) is a rare form of degenerative intervertebral disc disease, making up approximately 1% of all disc herniations. Although autopsy studies find an incidence rate ranging from 7% to 15%, symptomatic disease is still rare compared to lumbar and cervical disc herniations. Males and females are affected equally, with an average age at diagnosis of 48. 4 The majority of the TDHs are reported to be located at the level T8 or below, predominantly between T8 and T11 ( Fig. 143.1 ). ^, Similarly to the other locations in the vertebral column, TDH presents mostly as a posterolateral ( Fig. 143.2A ) or a posterior (see Fig. 143.2B ) protrusion.

Clinical Presentation and Diagnosis

Patients with TDHs can be asymptomatic and diagnosed incidentally; however, history and physical examination play a crucial role in the diagnosis when patients present with signs and symptoms of the disease. As in all intervertebral disc herniations, pain is the most common presenting symptom in TDHs. The character of the pain depends on the location where the disc protrudes. In addition to pain, other symptoms of myelopathy, such as motor (58%) and sensory deficits (84%) as well as bowel and bladder dysfunction (76%), are frequently encountered according to the early reports in the literature.

To be able to visualize the extent of the herniation, the location, and the surrounding tissues, choosing the correct imaging modality is crucial. In earlier years, myelography was used as a diagnostic tool for spinal pathologies. With the advances in imaging and emergence of computerized tomography (CT) and magnetic resonance imaging (MRI), these two modalities became the most frequently utilized techniques globally. Currently, MRI is the modality of choice in diagnosis of TDHs, as it allows visualization of any compression and soft tissue changes better than CT.

Conservative and Surgical Management

The majority of TDHs either reduce in size or remain stable throughout the course of the disease. Therefore, initial approach is the conservative management of the patient. Conservative management of TDHs mainly focuses on symptomatic treatment, with pain being the most frequent symptom. Accordingly, analgesics and other pharmaceutical agents that are used for pain generally make up the treatment regimen.

However, in instances of progress in herniation, intractable or refractory pain, and symptoms of myelopathy (e.g., motor and sensory deficits, bowel/bladder symptoms), surgical management becomes the preferred modality. Throughout the years, multiple techniques and approaches were developed in order to access the disc space safely and effectively. Still, the approach depends heavily on the position of the herniation, conditions related to the patient, and the surgeon. Among those approaches, posterior and posterolateral approaches are most commonly used for posterior or lateral herniation of the thoracic disc.

Historical Evolution of Surgical Technique

Although the first cases of TDH were reported in early 19th century, the first report of a surgical treatment for TDH was published in 1934 by Mixter and Barr. The surgical procedure described in this report was a laminectomy, followed by the removal of the disc. However, the main concern with the laminectomy approach was high rates of complication due to narrow working space. After the introduction of laminectomy as the primary procedure to treat TDHs, surgeons started developing alternative approaches to achieve better outcomes. The alternative techniques mainly aimed to create an extra opening with minimal additional damage, which led to the introduction of facetectomy in addition to laminectomy. Despite the efforts of developing alternative techniques, laminectomy (with or without facetectomy) remained as the only reported technique in the literature.

One of the first alternative procedures to be reported was costotransversectomy. The actual procedure was introduced in 1894 as an approach to treat Potts disease of the thoracic spine, and it was mainly used to drain abscesses. However, the initial technique went through modifications by different surgeons due to several complications. In 1960, Hulme et al. presented the first cases of thoracic disc surgery using the costotransversectomy approach.

Emergence of more alternative techniques for resection of TDH accelerated in this era, with transthoracic approach being introduced in the same year with costotransversectomy. These techniques were followed by utilization of the costotransversectomy technique in addition to laminectomy by Gjerris and Japsen in 1975. Development of new approaches also allowed surgeons to adjust and perform the appropriate techniques according to the location and extent of the herniation. For posterior lesions, the transpedicular approach was first used in the late 1970s.