This was a study of
trunk (back) motion from the Philadelphia Shriners hospital by a previous spine
fellow from Washington University, Dr. Joshua Pahys. This elegant study used a motion analysis lab
to quantify back motion between two groups of patients: 1) 65 patients having undergone
Vertebral Body Tethering (VBT), and 2) 47 patients who had a Posterior Spinal Fusion
for idiopathic scoliosis.
They evaluated thoracic
and lumbar flexion, extension, sidebending and rotation.
PSF had significant
loss of motion in all 4 directions at 2 years postoperative.
Flexion loss at L1 11 degrees
Flexion loss at L4 30 degrees
For each level of the fusion down
from L1 there was a 7 degree decrease in flexion motion
VBT had significant loss
of flexion and sidebending at 2 years postoperative.
Flexion
loss at L1 11 degrees
Flexion
loss at L4 17 degrees
Take away message
from this study about trunk motion after PSF and VBT:
1.
No clinical difference in trunk motion when PSF
vs. VBT are instrumented to </= L1.
This means there is not a compelling argument about using VBT to
preserve back motion if the surgeries end at T11, T12 or L1. In fact, a PSF is probably a better choice
since the spine can be actively derotated to decrease the rib prominence, much
better than a VBT procedure. When surgery goes down to L2, L3 or L4 VBT does
preserve more motion
2.
VBT did decrease in flexion and sidebending vs.
preop. This means only back extension
and rotation were preserved and there was no significant impact by performing
VBT surgery
3.
SRS scores are similar at 2 years postop. Patients did well in both groups and there
was no perceptible difference in pain, appearance, or function.