Does the Patient's Position Affect the Results of Spinal Fusion?Posterior spine surgery (from the back of the spine) is usually done with the patient in a certain position. This position is prone (face down) with the belly hanging free. The patient is in a face down kneeling position with the hips and knees bent.
This position helps keep pressure off the abdomen to reduce bleeding into the epidural space. The epidural space is inside the spinal canal but outside the spinal cord.
The problem with this position is that it places the low back in a position of flexion. The natural swayback curve called lordosis straightens out and curves in the opposite direction. There is some concern about the loss of lordosis that occurs when the hips are flexed. It's important to avoid a flat back after lumbar fusion.
In this study, before and after lordosis measurements are taken via X-rays. Patients were compared using two different operating tables. The goal was to see if different positions during the procedure make a difference in the lumbar spine. All patients had a one- or two-level posterior lumbar interbody fusion (PLIF).
The patients were divided into two groups. Group one was placed on a special surgical table called the Wilson frame. Group two used the OSI Jackson spinal table. Hip flexion was about 30 degrees using the Wilson frame. The OSI Jackson spinal table positioned the hips in about 70 degrees of hip flexion.
The authors reported no difference in the amount of total lumbar lordosis between the groups. This was true for measurements taken before, during, or after the operation. There were some changes in the amount of segmental lordosis (just at the level of the fusion).
This study showed that the position of the hips is important but more to prevent bleeding than to maintain spinal position. The position of the vertebrae is affected more by the type of fusion cages used. Lordosis is maintained better when it is built into the angle of the cage. It's important to keep the natural lordosis in the lumbar spine after fusion. It's not possible to do so using a position of hip flexion.
Future studies may evaluate the effect of using hip extension just before the metal rods are inserted. This might help maintain the amount of lordotic position needed. Preventing blood loss is a higher priority than preserving lumbar lordosis. The hope is that both can be accomplished in the future.
Jae Hyup Lee, MD, PhD, et al. Effect of Intraoperative Position Used in Posterior Lumbar Interbody Fusion on the Maintenance of Lumbar Lordosis. In Journal of Neurosurgery: Spine. March 2008. Vol. 8. No. 3. Pp. 263-270.
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