Failure of Monoaxial Pedicle Screws at the Distal End of Scoliosis Constructs: A Case Series

BackgroundThe goals of instrumented fusion for scoliosis are to correct deformities, stabilize the spine, and achieve arthrodesis. Monoaxial pedicle screws are often used in scoliosis constructs and have shown superiority over other types of pedicle screws in their ability to correct vertebral rotation and lumbar lordosis. However, because of the fixed-angle nature of the monoaxial pedicle screw head, any malalignment at the rod–screw interface could result in less than optimum stability.ResultsThis series exhibits 3 cases of set screw loosening with the use of monoaxial pedicle screws at the distal end of long spinal fusion constructs for the management of patients with scoliosis; these complications all occurred within 6 months of the index procedures. The results of a detailed microscopic analysis of the failed components from 1 of the cases are also presented.ConclusionsFrom this evidence, the authors of the current study recommend that surgeons exercise caution when using monoaxial pedicle screws at the distal end of long spinal fusion constructs, especially after compression has been achieved on the convex portion of the curve.