Thoracic Fracture through a Prior Instrumented Arthrodesis in a Patient with Ankylosing Spondylitis without Hardware Loosening: A Case Report

The objective of this article is to report a case of a patient with ankylosing spondylitis who sustained a fracture through a prior solid arthrodesis without loosening or changing posterior instrumentation. There have been few cases reported of a patient with ankylosing spondylitis suffering a fracture through a prior instrumented arthrodesis. None have noted the instrumentation remaining intact with the fracture through the middle of the construct. The surgeon must be aware of this possibility to avoid spinal instability that may lead to a neurological deficit. We retrospectively reviewed the case. A review of the literature was performed through a PubMed search. A patient was found to have a fracture within a prior construct despite the presence of a posterior instrumentation. The mechanism of failure was a three-column spine fracture with "bending" of the rods. This patient was treated with a revision posterior/anterior instrumentation and fusion with placement of larger-diameter rods for added stiffness. Fractures through a prior instrumented arthrodesis are rare but still can occur in the ankylosing spondylitis patient. Given the higher risk of epidural hematoma and neurological compromise in this patient population, the surgeon must keep this on the differential diagnosis when treating patients with a prior instrumented arthrodesis.