Wednesday, October 19, 2022


Blog Topic: Published study in Journal of Bone and Joint Surgery: Trunk Motion of Vertebral Body Tethering vs. Posterior Spinal Fusion




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.

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