Introduction

The aging of the population in industrialized nations appears to be an inevitable situation. It does not simply mean an increase in life expectancy owing to the improvement of medical science and health care, but additionally a significant decrease in birth rates has led to this situation. Back and neck pain are most frequently occurred presentations of older people, and the unique nature of the spine makes those problems highly complex to evaluate and to manage. The spine is a very specific anatomic and functional unit. The findings of radiological degenerative changes of the cervical spine in aging population are common. By the fourth decade of life, 30% of asymptomatic subjects show degenerative changes of the intervertebral discs, whereas by the seventh decade, up to 90% have developed degenerative alterations.^1,2 Thus, it is always important to interpret such radiological features in the light of the clinical presentation. If symptoms and findings are not correlated, the presence of a different pathology should be suspected, and appropriate evaluations are required. In order to assess the spine unit of patients (clinical, radiological; and laboratory findings; neurophysiology, etc.), cooperation between the orthopedic surgeon, the neurosurgeon, and the neurologisted is needed. Based on the present illness and physical examinations, a proper neurological workup should be performed. In addition to the neurological assessment, additional laboratory evaluations and other studies may be helpful in the differential diagnosis, including electromyography (EMG), electroneurography (ENG), sensory evoked potentials (SEP), and motor evoked potentials (MEP).

The aging of the spine induces considerable alterations in anatomical structures: discs, facet joints, ligaments, muscles, and bones. The degeneration of some of these structures can be responsible for the injury to the neural structures by herniated disc, spinal stenosis, and other degenerative disease.¹

Although various surgical treatments for spinal disorders have been proposed for years, the current concept in the evolution of all spinal surgical procedure is mostly concerned with minimally invasive techniques. The advantages of minimally invasive procedures include less postoperative pain, shorter hospital stays with faster recovery, and decreased surgical morbidity, mortality, and long-term sequelae. These benefits are the result of reduced damage to surrounding spinal structures.

Basic Science

As a flexible, multisegmental column, the functional role of the spine is to provide stabilization and upright position. The spine is composed of a static, changeless component, the vertebral bodies, and an elastic mobile component, the three joint complexes, consisting of the intervertebral disc and the two posterior facet joints. As mentioned earlier, the aging spine experiences considerable changes in anatomy (the structural components, biomechanics, etc.).²

The quantity of water present in the nucleus pulposus (contains a high proportion of hydrophilic glycosaminoglycans) decreases and both spinal height and the cushioning effect are reduced with aging. Gaps and fissures may develop in the discs, and with the time they may become desiccated and even ossified. As the disc height decreases, there may be a buckling of both anterior and posterior longitudinal ligaments. The buckling posterior ligaments may project into the spinal canal, reducing the space available for the spinal cord. Bony osteophytes may develop in the region of the vertebral bodies; endplate osteophytes may expand across the disc spaces and merge with osteophytes of adjacent vertebrae to form bridging osteophytes. If the osteophytes involve posterior endplates, they may protrude into the spinal canal, compressing the dural sac. People with congenitally narrowed spinal canals have greater risk for spinal cord compression as a result of these changes. Large bridging osteophytes on the anterior endplates may lead to severe problems in gastrointestinal, respiratory, or vascular systems. The size of the neural foramen, which the spinal nerves pass through, may be decreased both with the loss of spinal length and ossification and hypertrophy of these soft tissues around the vertebral column. Such age-related changes demonstrate the symptomatology in most patients presenting for cervical spine surgery.^1,2

Surgical Indications and Preparation

The indications for surgery include (1) persistent or recurrent upper extremity pain or numbness not responsive to a conservative treatments for more than 3 to 6 months, (2) progressive or profound neurological deficit, (3) static neurological deficit associated with radicular pain, and (4) imaging studies confirming pathoanatomic features consistent with clinical features.

All patients should have routine cervical spine radiographs, including dynamic views, computed tomography (CT) scanning, and magnetic resonance imaging (MRI) preoperatively. Intraoperative somatosensory evoked potentials are useful for monitoring the sensory neurological pathway continuously during the surgery and have been very effective for monitoring the dorsal columns of the spinal cord. This decreases the risk of an obstructed blood vessel, accidental removal of the breathing tube, or a patient becoming conscious during the procedure. Also, the patient may be monitored with motor evoked potentials (MEP) and electromyograms (EMG) intraoperatively.

Radiological Evaluation

Routine cervical spine radiographs, including anteroposterior, lateral, flexion, extension, and both oblique views, are taken for the evaluation of degenerative disc disease. The narrowing of the intervertebral disc space and neural foramen, formation of osteophytes or bony spurs, subluxation of facet joints, and segmental instability are commonly shown in degenerative cervical diseases. Although cervical radiographs and CT scanning are useful for visualizing bony anatomy and overall alignment of the spine, they are limited in the evaluation of neural structures, such as neural foramen, spinal cord or nerve roots, and the presence or absence of neural compression.

Magnetic resonance imaging provides excellent images of spinal structures, such as discs, neural elements, bony structures, muscles, and ligaments. It is the preferred method for confirmatory diagnosis and is generally recognized in published studies.

Surgical Techniques