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Vertebroplasty/Kyphoplasty
Injecting a spinal vertebrae with plastic for support-Restoring the height of a collapsed vertebra

For many years there has been no help for those individuals with osteoporosis (thinning of the bone) that develop a collapse of a spinal vertebra called a compression fracture that may be painful. Recently new techniques have been developed to restore and support the collapsed vertebra and relieve the accompanying pain. In these relatively low risk procedures, a needle is placed into the vertebra and a plastic material injected which hardens and supports the vertebra (vertebroplasty). Alternately the collapsed vertebra is restored in height with a balloon before injecting the plastic (kyphoplasty).

Anatomy

  • The normal spine is composed of 24 building blocks called vertebrae (seven cervical, twelve thoracic and five lumbar vertebra) that sit on the sacrum, which is the back part of the pelvic bone
  • Each vertebra is constructed of a body, lamina, and pedicles, which surround an opening, the spinal canal. Each vertebra has a spinous process, a section of bone that extends backwards from the lamina in the midline. (Figure 1)
  • Passing through the spinal canal is the spinal cord and, in the lumbar region, nerve roots. (All the roots together in the lumbar spinal canal are called the cauda equinae.)
  • Along the spinal canal, nerve roots exit through 'holes' in the side of the canal formed by two adjacent vertebrae called foramina
  • Separating any two vertebral bodies is a soft elastic material called a disk
  • On each side of the back of the spinal canal and linking one vertebra to the next are a series of small joints called facets. Extending outward from the area of the pedicle and facet and acting as an anchor for some of the short muscles between vertebrae is a short segment of bone called the transverse process
  • Normally there is motion between the adjacent vertebrae. The motion occurs at the disk, facets and ligaments.
Figure 1 - Anatomy of a spinal vertebrae (see text)

Pathology

  • Compression fractures of the spine
    1. With advancing age it is common, particularly in women after menopause, for bone to lose calcium (osteoporosis) and be subjected to a greater chance of fracture
    2. Less than 40% of postmenopausal women have a normal bone density (a measure of the amount of calcium in the bone)
    3. Up to 40% of these women with osteoporosis will have a fracture during their lifetime
    4. Compression fractures of the spine with loss of height of the vertebra are a frequent finding in those individuals with osteoporosis - 75% of these fractures are not related to injury (Figure 3)
  • Vertebral hemangiomas
    1. A hemangioma is a small non-cancerous tangle of blood vessels - similar to reddish birthmaks found on the skin
    2. When present in a vertebra, a hemangioma may be the cause of back pain
  • Metastatic disease of the spine
    1. Cancerous tumors in other parts of the body may go (metastasize) to the vertebra of the spine
    2. The vertebra weakened by the tumor may collapse and cause pain
  • Fractures of the vertebra can cause terrible pain that may last for months and cause significant disability
    Figure 3 - AP (A) and lateral (B) X-rays showing a compression fracture of a vertebrae previously injected with PMMA. The bone biopsy needle has been inserted into another vertebrae with a compression fracture. Courtesy AANS

History and Exam

  • Patients with a fracture from osteoporosis are
    1. mostly women
    2. patients who have been on steroids (cortisone like medications) for a long time
    3. patients with kidney failure
    4. individuals who have been in bed for a long time
  • Patients with a fracture as a result of tumor metastasis will frequently have other evidence of active cancer
  • With painful compression fractures may who have not been active may develop
    1. poor air exchange in the lungs that may lead to pneumonia
    2. blood clots in the veins of the legs or pelvis
    3. pulmonary embolus (blood clots that may go to the lung)
    4. narcotic dependence
    5. depression because of their poor quality of life
  • Frequently the pain is increased by tapping over or near the fractured vertebra

Tests

  • One of the first tests are X-rays of the spine. The X-rays are taken from front to back and from side to side. The X-rays show which vertebra have a compression fracture. The degree of compression is not necessarily related to the degree of collapse
  • Magnetic Resonance Imaging (MRI) may show
    1. Only a simple compression fracture
    2. That the fracture is due to a metastatic tumor
    3. A hemangioma of the body of the vertebra which may extend into the pedicles and lamina if the hemangioma is aggressive. The bone may show an irregular honeycomb pattern and there may be changes in the tissues around the vertebra

Indications/Contraindications for Surgery

  • The major indication for vertebroplasty is pain coming from a vertebra that has collapsed or contains an hemangioma or tumor
  • Patients with certain forms of lung disease may not be a candidate for vertebroplasty
  • The patient must be able to lie prone (flat on his stomach) for the entire procedure
  • Patients that have a bleeding tendency may not be suitable to receive the procedure

Surgical Procedure

  • Vertebroplasty
    1. Vertebroplasty may be carried out in an operating room or in a special X-ray suite. A needle is placed in a vein so that the patient can get medication for sedation and pain. The patient lies prone with padding under the body and with the hips slightly bent. The arms are positioned above the shoulder. (Figure 2)
    2. A radiopaque (visible on X-ray) marker is placed on the patient over the vertebra to be injected. Positioning of the marker is guided by fluoroscope (video-like X-ray machine). Clearly seeing the correct vertebra is more difficult in the severely osteoporotic patient
    3. Local anesthetic is then injected into the skin and along the path toward the pedicle of the vertebra to be injected. The needle is left in against the pedicle to mark the path of the special needle used for injecting the cement. The special needle is an 11-gauge bone biopsy needle. A small skin incision is made and bone biopsy needle inserted
    4. The tip of the bone biopsy needle is stuck for about 1-2 mm into the pedicle. This is the most painful part of the procedure and additional pain medication is given before this is done. Positioning of the this needle is continuously guided with the fluoroscope in both the anterior-posterior (AP, front to back) and lateral (side to side) views
    5. The bone biopsy needle is advanced to the front one-third of the vertebra. (Figures 3 and 4) On the AP view the needle lies near the midline of the body of the vertebra. The needle is filled with saline (salt solution) to prevent air injection. A contrast solution that can be seen on X-ray is injected. The surgeon takes X-ray pictures during the injection to see how the contrast flows from the center of the vertebra into the local veins. Ideally the contrast material slowly fills and a blush of contrast is seen on X-ray. If there is a rapid run-off of contrast material the needle is repositioned
    6. The plastic material to be injected is then prepared. The material is polymethylmethacrylate (PMMA), which comes in two parts, a powder (methylmethacrylate polymer) and liquid (methylmethacrylate monomer). The powder is mixed with tungsten powder or barium sulfate to make it visible on X-ray. The liquid is added to the powder and mixed to a thick yet pourable consistency similar to honey
    7. The PMMA is then loaded into several small syringes. The syringe is connected to the bone biopsy needle and injected under fluoroscopic guidance to be sure that the material does not run off into the veins. The PMMA hardens after injected to support the vertebra (Axial and sagittal animations)
    8. The needle is then removed and a stitch used to close the small incision
Figure 2 - Illustration of the position of the patient on the operating or fluoroscopic table. The hips are elevated and the arms are forward to avoid any problem with the lateral X-ray. The arrow indicates the direction of the needle. Courtesy AANS
Figure 4 - Illustration of the bone biopsy needle penetrating the pedicle and entering the body of the vertebrae that has a compression fracture (A). The PMMA fills the vertebrae from front (B) to back (C). Courtesy AANS
Animations
Figure 5 - Animation of a bone biopsy needle entering the vertebral body through the pedicle, PMMA injected and the needle removed
  • Kyphoplasty
    1. The kyphoplasty is similar to the above vertebroplasty procedure. (Figure 6)
    2. After the bone biopsy needle is inserted, a special balloon is inserted into the body of the vertebra and inflated to raise the collapsed bone (Figure 7 and 8)
    3. The balloon is deflated and removed leaving a cavity (Figure 9)
    4. The cavity left by the balloon is then filled with PMMA and the needle removed (Figure 10)
Figure 6 - Compression fracture with loss of height of the vertebral body. © T. Graves Figure 7 - A needle is inserted into the vertebral body through which a special balloon catheter is introduced. © T. Graves
Figure 8 - The balloon is inflated under pressure to decompress the collapsed vertebral body. © T. Graves Figure 9 - The balloon is deflated leaving a cavity inside the vertebral body. © T. Graves
Figure 10 - A catheter is inserted into the cavity through which the cavity is filled with PMMA. © T. Graves

Complications

  • Complications occur in
    1. approximately 3% of osteoporotic patients
    2. approximately 5% of patients with hemagiomas
    3. approximately 10% of patients with cancer to the vertebra
  • The most common complications are
    1. Rib fracture due to the downward on the back needed to insert the needle in the bony vertebra
    2. Irritation of an adjacent nerve root
    3. These complications usually resolve on their own in a few months
  • Pneumothorax (punctured lung)
  • Fracture of the pedicle
  • PMMA pulmonary embolus - the PMMA enters the veins through the bone and is taken to the lung
  • Compression of the spinal cord with paralysis or loss of feeling
  • Increased back pain
  • PMMA may go outside the bone into the soft tissues
  • Wound Infection
  • Pneumonia

Postoperative Care

  • The patient is kept lying flat for two hours and then allowed to sit and walk
  • If pain relief is good, the patient may be able to be discharged home with muscle relaxant and anti-inflammatory medication (such as Motrin)
  • The patient is encouraged to remain as active as possible
  • About 90% of the patients with osteoporosis and hemangioma and about70% of those with metastases improve

select link here: Adapted from 'Vertebroplasty' by R.D. Fessler, et. al. in the Neurosurgical Operative Atlas, volume 9, pg 233, 2000, published by the American Association of Neurologic Surgeons; with permission.