Growing Rods for Early-Onset Spinal Deformity



Growing Rods for Early-Onset Spinal Deformity


Grant D. Hogue





Indications



  • Evaluated on a case-by-case basis



    • Patients with a rib-vertebral angle difference >20° and Cobb angle >20° should be considered high risk for progression of their curve


  • Children with significant growth remaining and



    • Curves with a Cobb angle >50°


    • Curves causing significant comorbidity to other body systems


  • Recommend magnetic resonance imaging (MRI) for curves that progress, have Cobb angle >20°, and/or have examination with absent abdominal reflexes or other concerning neurologic findings



    • Alternative treatments


    • Observation for curves <20° or curves that do not progress


  • Serial casting or bracing for progressive curves >20° and optimally younger than 2 years


Sterile Instruments/Equipment Table



  • Radiolucent table with supports as needed or spine frame table if patient is of sufficient size


  • Standard instrumentation for posterior spinal fusion


  • Advanced imaging of choice (fluoroscopy, navigation, robotics)


  • Manufacturer-specific instrumentation based on surgeon’s choice of traditional growing rod (TGR) or magnetically controlled growing rod (MCGR)


Patient Positioning



  • Patient positioning (Figure 8.1) will vary largely based on patient size and curve magnitude


  • Prone position with appropriate pads and gel rolls for support on a radiolucent flat top



    • Check that all rolls and padding devices are radiolucent


  • Prone on frame with head holder and pads


  • In patients with contractures, special accommodations must be made at the time of positioning


Surgical Planning



  • Anchor points: Rib, spine, and pelvis



    • Points of fixation are determined by the type of curve (idiopathic, neuromuscular, neurogenic), curve parameters (apex, end vertebrae, etc.), and local bone size/quality


    • Occasionally shorter constructs (Figure 8.2) can be employed, but T2-L3 is typically a safe and predictable construct for most neurotypical patients













    • With the current availability of pedicle screw sizes, many patients can be treated safely with all screw constructs, but secondary to pedicle size or bone quality, there are often times when hooks are the better choice


    • When using hooks exclusively at an anchor site, it is recommended to add a cross-link for augmentation of stability and a claw configuration (Figure 8.3)


  • Even in very small children, pedicle screws can generally be used in the lumbar spine



    • In cases of poor bone quality or perceived diminished implant strength, short rods can be added into the proximal construct to increase local stability or even to allow for fusion with staged insertion of the growing construct at a later date (see Figures 8.3 and 8.4)


    • Longer constructs should be considered in neuromuscular scoliosis patients with probable need for pelvic fixation


    • Three-segment proximal fixation has led to fewer anchor pullout complications in our practice


Surgical Approach



  • Standard midline posterior approach to the spine with subperiosteal dissection at the levels to be instrumented.



    • Can be either done with a single long incision or smaller incisions directly over the anchor levels and the rod connector(s) (Figure 8.4)


    • It is important to note that even if using 1 long incision, the only deep dissection is at the anchor levels