Spine Pathology

Low Bone Density

Low bone density can be a problem for anyone receiving any type of endoprotheses in the knee, hip, shoulder, or back. However, low bone density for ADR patients does not disqualify them for surgery, because bone ceramic material can be injected into the vertebral body to support the endoprothesis. However, despite all precautions bad bones can be a problem in about 3 out of every 500 hundred cases, leading to subsidence. Microfractures and other defects of the bones are not always detected by tests or perioperative examination.

Bone Density Testing

Bone density testing has been historically used for determining osteoporosis and osteopenia, the precursor to osteoporosis. In ADR surgery, some spine surgeons use bone density measurements to assess the risk of subsidence of the disc into the bone, although in this author’s opinion bone density testing should be used by all spine surgeons. Subsidence also occurs in fusion.

Bone density testing, when properly done, is about 80% accurate in assessing osteoporosis and osteopenia. The results are reported as a T score. A T score is a statistical term denoting where the patient lies on the normal curve of distribution. A T score of 0 means that the patient is exactly average for the patient’s gender, height, weight and age. A T score of +1 means the patient is one standard deviation above the average person for bone density. A T score between -1 and -2.5 is interpreted as osteopenia and scores lower than -2.5 are interpreted as osteoporosis.

At it's heart both the DXA (low radiation) and/or the QCT scanner (high radiation) look for the amount of minerals per a given volume. The measuring unit is kg/m3. Slices are measured as g/cm2. Of course, the findings are normalized to the population group of the patient. Reference data exists on the femur, lumbar, hip, total body and wrist. None exist for the cervical or thoracic spine.

A popular myth is that bone density should always be done in the area of the operation, but this is not necessarily true and shows a lack of understanding of how the test works. For example, they suggest a lumbar patient should have a lumbar bone density test. While it is acceptable to do the test in the lumbar spine (and ProSpine does lumbar testing) caution must be exercised with the resulting numbers, because patients with DDD have shorter spines than normal and can create a false high result. Bone density measurements in the hip are entirely acceptable.

Bone density is surprisingly consistent throughout life, except for many women past the age of fifty, who are a high risk group for osteoporosis, or at least that is the conventional wisdom. ProSpine testing has shown in its patient population a much higher risk for men, than previously thought.

Proper operation of the scanner by the technician is also required. It is not merely a question of turning on the switch. Judgments are made by the technician about where each level begins and ends.

Perioperative Examination of the Bone

An experienced surgeon exams the conditions of the bones during surgery. The machine tests are just indicators.

Cervical myelopathy is an insidious condition of the spinal cord, which if allowed to progress can cause permanent paralysis and even death. Cervical myelopathy is usually caused by what is know as Cervical Spondylotic Myelopathy (CSM) or trauma.

Cervical myelopathy is insidious, because unlike compressed nerves radiating from the spinal cord, the spinal cord feels no pain and it is difficult for patients to say when the symptoms begin. Cervical myelopathy is developed slowly, resulting from a spinal canal stenosis, which is a narrowing of the spinal canal. It is the slow degeneration of the spine called spondylosis, which causes the narrowing of the spinal canal.

Cervical myelopathy begins with compression of the spinal cord in the cervical spine. Edema begins to build about the spinal cord as the cord attempts to protect itself. This edema appears as white in a t2-weighted MRI images.

Early symptoms of cervical myelopathy:

• Heavy feeling in the legs
• Unable to walk at a brisk pace
• Gait disturbance, e.g. bilateral uncertainty when walking blindfolded.
• Deterioration in fine motor skills (such as handwriting or buttoning a shirt)
• Feelings of numbness, tingling, pins and needles, or shooting fire like pain in the arms and/or legs, when bending their head backward or far forward (known as Lermitte’s phenomenon).
• Reduced bladder control, or sexual disturbance, associated with the above.

Spinal nerves inside the spinal cord, which run from the brain to the legs will be affected. Thus these medical signs will become pathological:

Traumatic cervical myelopathy with spinal canal stenosis is usually diagnostic at the time of the trauma or is the result of acute disc herniation. The symptoms can be the same as cervical myelopathy caused from degenerative conditions.

Degenerative Disc Disease: Definition

Degenerative Disc Disease (DDD) (sometimes spelled Degenerative Disk Disease) is a major cause of back pain. It is a particular type of spondylosis, where the protein and collagen structures, particularly in cartilage, gradually deteriorate with age. The intervertebral discs are affected by spondylosis, because there are more than 60 bands of collagen fibers called lamellae, which encase the water-filled nucleus. The weakening of these bands and the annulus fibrosis leads to water loss in the nucleus, loss of disc height, the reduction of distance between vertebrae, and the increased probability of a herniated disc.

Degenerative scoliosis is a distortion of the spinal column. It can have different forms and different causes. It is to be distinguished between the scoliosis that occurs in youth. Degenerative scoliosis is observed in older persons. The type of scoliosis that occurs in younger people generally is described under idiopathic scoliosis. However, solid fusion of the back or implantation of long rods is no longer the only treatment options.

The main cause of the degenerative scoliosis is the wearing of the spinal disks with associated intervertebral disc height reduction, leading to instability of the spinal column. If this instability cannot be corrected by the muscle volume apparatus, different forms of scoliosis can develop as the body’s focal point shifts causing, bad posture, sloping of the pelvic girdle, sacroiliitis and much of more. These variations and incorrect loading of the spine are connected frequently with back pain. However, nerve pain in the legs can be experience, due to narrowing of the nerve exit points, which is called neuroforamina stenosis.

In the patient shown right, we have three segments, which have full 360-motion instrumentation, DSS plus ADR. Although removal much of curve and rotation of this spine has been achieved, perfect straightness is not achieved always after surgery. But this spine is within tolerance and can be further straighten in time and retain motion with proper rehab. This patient was advised to have his entire lumbar spine fused by other doctors.