THORACOSCOPIC SPINE TETHERING IN SCOLIOSISDr Jaren Riley, MDDr Steve Rothenberg, MD
OBJECTIVES•Understand principle of guided growth for osseus structures•History of guided growth for the spine•Indications for vertebral body tethering•T echnique•Outcomes
POSTERIOR SPINAL FUSION•3 hurdles with posterior spinal fusion•Must wait for skeletal maturity (or near maturity)•Decreased spinal motion•Adjacent segment degeneration
GUIDED GROWTH •Heuter-Volkman Law•Compression across a growth plate slow growth•Distraction accelerates growth
GUIDED GROWTH IN THE SPINE •Newton et al 2008•Bovine model•Placed lateral tether•6 months of growth•Straight spines became curved•Vertebral stapling•Rigid implant across mobile segment•Poor outcomes
FURTHER INNOVATION •Lenke 2010•Vertebral tether with polypropylene rope across mobile segment•Newton•Also showed that discs maintained hydration•Vertebral bodies returned to normal shape•This is the key to MAINTAINING the correction!!!
INDICATIONS •Growth•Must have enough growth remaining to correct the curve•Shouldn’t have too much growth remaining, or curve will overcorrect•Curve size•Curve should be large enough that it will predictably need surgical intervention in the future•Curves too big will not correct•T ether will break•Mechanics too powerful for tether to overpower •Growth•Risser 0, triradiate cartilage closed, Sanders hand stage ≤ 4•Curve Size•40-65º
INDICATIONS•Must be able to tolerate single lung ventilation•Screen for risk factors pre op•ALWAYS tell parents, we don’t know until we know•Any risk factors•Pre op nebulizer treatment•All patients•Ketamine•No longer use double lumen ET tube •Flexible curve•Rotation•Doesn’t remodel well•Rotation must either be small, or family must understand it may not improve•T4 may be upper limit for instrumentation•L4 may be lower limit (iliac crest gets in the way)
TECHNIQUE •Lateral decubitus•Convexity up•Arrange padding to allow for curve manipulation
TECHNIQUE •Thoracoscpic access•3-4 incisions•MUST create portals more posterior than normal to accommodate the rotation of the spine•Elevate periosteum, take down segmentals•If instrumenting both sides of a vertebral body, spare a segmental artery on one side
TECHNIQUE•Why posteriorly placed portals?
TECHNIQUE •How many portals?•2-3 levels/ portal•No need to create a new incision for each rib space•Shift current incision to next rib space
TECHNIQUE •Starter awl•Staple
TECHNIQUE •Tap•Screw
TECHNIQUE •Place and tension tether
TECHNIQUE •Check screw location, orientation, and length with O-arm
OUTCOMES•Samdani (n=11)•2 returned to OR to loosen tether (overcorrection)•Good curve correction in coronal, sagittal and axial planes •Newton (n=17)•41% revision rate•Complications•T ether breakage•Overcorrection•Curve progression
OUTCOMES •Number of cases: 8•Avg inpatient stay: 3.5 days•Avg time with chest tube: 2 days•No neurologic deficits•No infections•One gymnastics state champion (6 months postop)•Follow up too short
FUTURE DIRECTIONS •Refine indications•Algorithms for curve magnitude, growth remaining, flexibility, and how much correction to shoot for in surgery•Better instrumentation•Reliable tether•Smaller implants