Volumetric analysis of thoracic and lumbar vertebral bodies

During the last decade, vertebral augmentation techniques with cement (kyphoplasty and vertebroplasty) have revealed that 75% to 100% of individuals with osteoporotic vertebral compression fractures have good to moderate pain relief postoperatively, as well as adequate restoration of the vertebral body height. The volume of cement injected into a vertebra varied in different reports. To our knowledge, there are no studies that report on the physiological distribution of thoracic and lumbar vertebrae body volumes.

The purpose of this study was to quantitatively evaluate thoracic and lumbar vertebral body volumes.

Forty computed tomography (CT) scans of the thoracic and lumbar spines were used to measure a volume of each vertebral body.

Forty CT scans with standard 2.5-mm bone window cuts of the thoracic and lumbar vertebrae (20 men and 20 women) were analyzed to measure the volumetric capacity of vertebral bodies using a BrainLAB Software (iPlan RT image 4.0) program. The software was tested for validity and reliability in two pilot studies. Mean and standard deviations for each vertebral body volume were calculated and recorded. The vertebral body working distance and the so-called "safe zone" were also measured to determine a size of a balloon to be used in kyphoplasty.

Vertebral body volume increased gradually from T1 to L4 with the exception of L5, which measured to be smaller than L4. The mean thoracic vertebrae volume was 15.0 cm(3) (ranged in the absolute values from 5.2 to 39.5 cm(3)), and the mean lumbar vertebrae volume was 35 cm(3) (ranged in the absolute values from 19.7 to 61.5 cm(3)). Men had larger volume vertebral bodies only in the lumbar spine compared with women. The average vertebral body working distances from T1 to T4 was 23.4+/-2.7 mm, from T5 to T9 was 30.3+/-3.6 mm, and from T10 to L5 was 35.5+/-3.9 mm.

Knowing the physiological variability of vertebral body volumes may help prevent complications as a result of underaugmentation or overaugmentation with excessive amount of cement during kyphoplasty or vertebroplasty in osteoporotic compression fractures. We recommend using 10 mm balloons from T1 to T4, 15 mm balloons from T5 to T9, and 20 mm balloons from T10 to L5 for kyphoplasty.