Spine
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Comparative Study
Mechanical stiffness of segmental versus nonsegmental pedicle screw constructs: the effect of cross-links.
A biomechanical study in porcine spines of the construct stiffness effects of segmental pedicle screws. Stiffness effects of supplementation of nonsegmental screw constructs with cross-links was also evaluated. ⋯ Segmental pedicle screw constructs increased mechanical stiffness compared to nonsegmental constructs in our fusion models. Placement of a single cross-link with nonsegmental screws eliminated statistical differences for 3 and 4-vertebral level constructs, and may be a satisfactory alternative in this clinical setting. Caution in applying these results inlonger constructs is recommended, given persistent increased stiffness found for the segmental 5-vertebral level models.
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Retrospective radiographic analysis of patients with adolescent idiopathic scoliosis (AIS) status after instrumentation removal. ⋯ Instrumentation removal in AIS is not always a benign process because the long-term follow-up of this cohort of patients shows a "settling" effect in the coronal plane of the main thoracic and TL/L curves after instrumentation removal. Interestingly, there was no change in the sagittal plane with time. Parents and patients should be counseled for this result when instrumentation removal is contemplated, and limited removal of focally symptomatic implants should be considered.