The Crankshaft Phenomenon

J Am Acad Orthop Surg. 2017 Sep;25(9):e185-e193. doi: 10.5435/JAAOS-D-16-00584.


The crankshaft phenomenon, a progressive rotational and angular spinal deformity that can occur after posterior spinal surgery, has been reported in pediatric patients with idiopathic, congenital, and neuromuscular scoliosis. In the skeletally immature patient, the crankshaft phenomenon is thought to occur secondary to continued growth of the anterior elements of the spine after solid posterior spinal fusion. The condition has also been reported in the setting of newer, so-called growth-friendly posterior distraction-based spinal instrumentation. The clinical evidence of crankshaft phenomenon is often subtle, whereas radiographic findings are usually more apparent. However, objective measurement of radiographic signs may be complicated by instrumentation and postoperative changes. Treatment options for patients with the crankshaft phenomenon are limited; in those with problematic deformity and/or risk of progression, additional surgery may be indicated.

Publication types

  • Review

MeSH terms

  • Child
  • Disease Progression
  • Follow-Up Studies
  • Humans
  • Osteogenesis, Distraction / adverse effects
  • Osteogenesis, Distraction / methods
  • Postoperative Complications / diagnostic imaging
  • Postoperative Complications / etiology*
  • Postoperative Period
  • Radiography
  • Retrospective Studies
  • Scoliosis / complications
  • Spinal Fusion / adverse effects*
  • Spinal Fusion / methods
  • Spine / diagnostic imaging
  • Spine / growth & development
  • Torsion Abnormality / diagnostic imaging
  • Torsion Abnormality / etiology*
  • Treatment Outcome