The third case here is an idiopathic scoliosis case with a focal sagittal plane deformity but well compensated overall. We got our correction with three levels of lateral. She didn’t need a ton of correction in the sagittal plane. Similar in concept, we developed this construct using multiple materials ranging from super stiff cobalt chrome 6.0 mm and 5.5 mm to less stiff titanium rods measuring 5.0 mm to 6.0 mm and connecting those with dual-headed pedicle screws at the top of the construct.
Before using the built-in dual-headed screws I would employ the side-to-side connector system we typically use for outrigger rods and match that to the patient. It’s almost impossible to get dual-headed screws to fit well in the upper thoracic spine, so I still tend to use side-to-side connectors, but this puts a lot more stress on the connecting rod as there’s a much larger gap in between where those connectors sit.
The dual-headed pedicle screw technique puts most of the stress on the screws themselves, rather than the connecting rods. The dual-headed pedicle screws are placed either at the UIV minus one or UIV minus two, depending on how much give you want to provide at the top of the construct. Ideally you don’t want to have that gap with outrigger rod spanning T12-L1 if you can avoid it. This is a very nice way to share that load with the pedicle screws and create a biomechanically strong construct at the top while providing some give there and preventing undue stress on the superior levels.
Dr. Mullin: You and I are on the same page that we want to go from a fused long segment and have some way to get a soft landing. My way is getting transitioned through these tethers.. I’m doing more the spinous process tethering, which again is just another way to get the soft landing.
I played around in lab on the sublaminar technique. I don’t think we need to be subjecting patients to something with unproven benefit, so that’s why I tether the spinous process. Spinous process tethering offers pretty minimal disruption of the soft tissue. My one concern in Zach’s concept of his soft landing is that it’s not soft enough.
There are a couple different ways reported for weaving technique. I’ll thread in the inner spinous between T10 and T11 and then go through a hole I drill with the matchstick and use a tenaculum at T9 to thread through the T8 posterior ligamentous complex and back down into the T9 spinous process where it’ll be one hole, but the tether will pass through twice and finally loop down back through the T10, T11 interspinous space. The immersing tether has a blunt needle attached to it, which makes it easier to pass through.
