Needle Size and Imaging Used in Percutaneous Biopsies of the Spine
Lesions of the spine are often biopsied in order to make an accurate diagnosis. The problem could be a tumor, infection, or cancer metastases. During the biopsy, a small piece of tissue is removed and sent to the lab for proper identification.
Treatment is based on these findings. Open-incision biopsy is quickly being replaced by fluoroscopic- or CT-guided percutaneous biopsy. In this report, the effect of the inner diameter of the biopsy needle is summarized. The authors present their findings from a meta-analysis done using 25 published reports.
Percutaneous means through the skin. During a percutaneous biopsy, a very long, thin needle is inserted through the skin and soft tissues and then into the bone. A sample of the suspicious tissue is removed and analyzed by the pathologist.
In order to guide the needle to the right spot, the surgeon uses an X-ray device called fluoroscopy. This type of imaging allows the surgeon to see while moving the needle. The advantage of this type of biopsy is that the muscles aren't cut open. The surgeon can also avoid damaging nearby nerves. The disadvantage is that it is less accurate than an open biopsy.
CT scan is another method used to guide biopsies. CT scans give the surgeon a more accurate image of the structures. But the technique isn't real-time like it is with fluoroscopy. The use of CT scans to guide the process takes longer than fluoroscopy. But it is more accurate for difficult to reach areas such as the thoracic or cervical (neck) spine.
After reviewing all relevant articles, the authors summarized the findings. The use of CT-scans to guide the needle was slightly more accurate and safer (fewer complications) when compared with fluoroscopic-guided biopsies. The difference wasn't huge (3.3 per cent complication rate with CT scan compared with 5.3 per cent for fluoroscopy). There aren't many studies to go by, so these findings might be different if a larger number of patients were involved.
Besides comparing results with different guidance systems, the authors also investigated the results comparing different sized needles used to do the biopsies. One challenge in performing biopsies is to get enough of the pathologic tissue to make a diagnosis. This is called adequacy. Accuracy is also important. Usually the accuracy of a biopsy is confirmed after surgery when the removed tissue is examined more thoroughly.
The inner diameter of the needle was evaluated as a factor in adequacy and accuracy of percutaneous spinal biopsies. Most of the studies were done with spinal metastases. Radiation before the biopsy complicated the diagnosis. In general, a smaller diameter needle had better results. The needle didn't block the surgeon's view or damage the soft tissues it passed through. Larger diameter needles were better for taking samples from sclerotic (hardened) bone lesions.
The authors conclude that when doing percutaneous spine biopsies, the surgeon may have a choice between fluoroscopy and CT-guided biopsy. There are pros and cons to each one. Choosing the right one for the most accurate diagnosis depends on the type of lesion, location of the problem, and level (cervical, thoracic, or lumbar spine). The expertise of the surgeon is also an important factor in the outcome.
Ali Nourbakhsh, MD, et al. Percutaneous Spine Biopsy: A Meta-Analysis. In The Journal of Bone and Joint Surgery. August 2008. Vol. 90-A. No. 8. Pp. 1722-1725.
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