DISTAL MIGRATION OF THE RODS OF A CONSTRAINED POLYAXIAL PEDICLE SCREW SYSTEM

Spinal instrumentation and surgical techniques have exponentially improved over the years and today’s spinal surgeon is well equipped to rigidly fix the spine with minimum adverse effects. But, especially for adult spinal deformity surgery, up to one third of patients experience some form of radiographic and/or implant-related complications, ranging from rod or screw breakage to implant prominence(1). Distant rod migration after spine instrumentation is not a common complication but could potentially result in high morbidity or even fatal outcomes if unrecognized. There are plenty of case reports in the literature about this type of complication following spinal instrumentation. These reports range from cephalic to caudal rod migrations, which in some instances lead to near catastrophes(2-5). There are cases of rod migrating from cervical spine fixation to the occipital fossa, into the brain matter and those of rod migrating from lumbar spine fixation down to the knee(3,5,6). Interestingly, none of all these published reports describe any propensity of this type of complication happening with any particular implant brand, make or metal type. We report here three case incidents (in two patients) of lumbar spinal instrumentation that represented with caudal rod migration, all associated with one particular implant make. CASE REPORTS