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Vertebroplasty may not lead to pressure changes in the neighboring disc space
Investigators find that etiology, not surgery, may be a factor for increased postop fracture risk.
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While previous research has questioned whether vertebroplasty affects the neighboring disc space, a new biomechanical study indicates that the procedure has no impact on the pressure patterns at the adjacent disc space.
Researchers studied the pressure distribution in seven cadaver spines at the L4-L5 disc space through a range of motion before and after vertebroplasty performed at the L4 level. A comparison of the pressure profiles before and after vertebroplasty showed no significant differences in the pressure distribution in the adjacent disc space.
"The data suggest that changes in intradiscal pressure profiles adjacent to a vertebroplasty would not increase the pressure seen at the adjacent disc space," Michael Tseng, MD, told Orthopedics Today.
Pressure mapping technique
Tseng and his colleagues affixed the lumbar spine specimens with pressure monitors at the anterior, posterior, center, left and right portions of the L4-L5 disc space, according to their abstract. They then placed the specimens in a six-degrees-of-freedom testing apparatus and examined pressure distribution within the disc space in axial rotation, lateral bending and flexion/extension. The investigators repeated the testing protocol after performing a vertebroplasty at the L4 level and recorded the postoperative pressure patterns.
They discovered that the procedure did not lead to changes in the pressure magnitude in the neighboring joint space. Tseng said that the researchers were not surprised by their findings.
"Prior mathematical, finite-element analyses have led to mixed conclusions regarding the effect of vertebral augmentation on adjacent segments," he said. "We suspected that vertebroplasty would not increase the pressure seen at the adjacent disc space."
Etiology a cause of risk
The findings also point to etiology — not vertebroplasty — as a potential factor for increased postoperative fracture risk. "Prior reports demonstrate an increased risk of subsequent fracture following vertebroplasty," Tseng said. "These data suggest the increased risk is related to underlying etiology — for example, osteoporosis, trauma, etc. — and not the surgical intervention, since the load transmission through the disc space does not increase."
The research sheds new light on a procedure that may grow in importance as the elderly population booms. "With our aging population, cement augmentation of the vertebral body will play an increasing role in fracture care and instrumented fusions of osteoporotic bone," Tseng said. "Understanding the effect of this modality on adjacent segments is essential."
For more information:
- Michael Tseng, MD, is an orthopaedic resident at William Beaumont Hospital. He can be reached at 3601 West 13 Mile Road, Suite 604, Royal Oak, MI 48073; 646-765-0333; e-mail: mdtseng@hotmail.com. He indicated that Synthes Spine funded the study. A portion of the vertebroplasty cement and associated supplies were also donated by Cook Medical.
- Tseng M, Bilkhu S, Herkowitz H, Truumees E, Demetropoulos CK. Effects of vertebroplasty on adjacent intradiscal pressure profile. #117. Presented at the International Society for the Study of the Lumbar Spine 34th Annual Meeting. June 10-14, 2007. Hong Kong.