Expert's comment concerning Grand Rounds case entitled "Intraspinal canal rod migration causing late-onset paraparesis 8 years after scoliosis surgery" (I. Obeid et al. Eur Spine J; 2014, DOI 10.1007/s00586-014-3367-y)

Late neurological complications due to laminar hook compression in idiopathic scoliosis surgery

Introduction

To provide a review of unusual neurological complications occurring years after spinal instrumentation surgery.

Case Presentation

The authors analyzed the cases of three patients with adolescent idiopathic scoliosis who presented with delayed neurological symptoms (later than 12 months postoperatively) following spinal deformity surgery using Texas Scottish Rite Hospital (TSRH) hook-rod instrumentation. One case presented with conus medullaris syndrome while the last two were rare cases of posterior cord syndrome due to a dislodged laminar hook at the thoracolumbar transition.

Discussion

In all three cases, the neurological symptoms were due to direct laminar hook compression. Metallosis was observed extra-spinally around the hook-rod construct but not at the sublaminar site. The dislodged laminar hook responsible for the symptoms was situated at the concavity of the curve with the blade-tip pointing downwards. Symptomatic improvement was observed in all patients following complete hardware removal. Conscientious long-term follow-up of patients undergoing posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) is important in order to recognize late neurological deficits directly related to instrumentation. Anamnesis and physical examination are key for initial assessment and diagnosis, while myelography and computed tomography (CT) images are of great help to confirm the site of spinal compression. Removal of the dislodged laminar hooks after PSF with TSRH instrumentation in AIS cases can potentially improve neurological symptoms.