My father had a kyphoplasty done for a fractured spine and ended up with a second fracture in the next spinal level. We took him to a second surgeon for an opinion about what caused the two fractures. She told us the first fracture was because of brittle bones. The second fracture was likely caused by too much cement oozing out of the kyphoplasty. Wouldn't extra cement make it stronger, not weaker?
Vertebral compression fracture refers to a mini-collapse of a vertebra in the spine. Tiny fracture lines in the bone (usually the front half of the vertebra) result in the bone taking on a wedge- or pie shape when viewed on X-rays from the side.
This type of fracture is most common in older adults who have osteoporosis (decreased bone mass or brittle bones). Just the weight of the body and pressure from postural changes (stooped head and shoulders) can put enough pressure (or compression, hence the name compression fracture) on the bone to cause a collapse.
The balloon kyphoplasty procedure is designed to restore height of the fractured and collapsed vertebra.
Two long needles are inserted through one or both sides of the spinal column into the fractured vertebral body. These needles guide the surgeon while drilling two holes into the vertebral body. The surgeon uses a fluoroscope (special 3-D real-time X-rays) to make sure the needles and drill holes are placed in the right spot.
The surgeon then slides a hollow tube with a deflated balloon on the end through each drill hole. Inflating the balloons restores the height of the vertebral body and corrects the kyphosis deformity. Before the procedure is complete, the surgeon injects bone cement into the hollow space formed by the balloon. The cement is injected a little bit at a time until the cavity is filled. They try to keep most of the cement in the front three-fourths of the vertebral body. This fixes the bone in its corrected size and position and supports the front part that has collapsed the most.
This procedure halts severe pain and strengthens the fractured bone. However, it also gives the advantage of improving some or all of the lost height in the vertebral body, helping prevent or correct kyphosis. It does not, however, prevent a second or subsequent fracture from occurring at the next (adjacent) level. In fact, there is some concern that the kyphoplasty might actually increase the risk of another vertebral compression fracture.
One reason for this is the oozing cement you mentioned. Leakage of the stiff cement into the disc area of a person with osteoporosis increases the stress and load on the endplate. The endplate is a cartilaginous structure between the disc and the vertebral bone. Any change in the forces placed on the endplate are translated to the adjacent vertebral bone. Studies clearly show that cement leakage increases the risk of a second (recurrent) vertebral compression fracture.
But there may be other risk factors that contribute to adjacent compression fractures. Another possible reason for recurrent vertebral fractures is bone metabolism. Decreased bone mineral density from altered bone metabolism may be an important risk factor in compression fractures. Other possible variables include age, body mass index, history of tobacco use, and the use of antiosteoporosis medications.
So, although cement leakage is an important risk factor in recurrent vertebral compression fractures, it isn't the only one. Altered bone metabolism combined with cement leakage may double the risk but the exact proportion of influence from each one has not been determined.
Christos P. Zafeiris, MSc, MD, et al. Hypovitaminosis D as a Risk Factor of Subsequent Vertebral Fractures After Kyphoplasty. In The Spine Journal. April 2012. Vol. 12. No. 4. Pp. 304-312.
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