Analysis of a retrieved Isola spinal system fractured in service

A 1/4-in.diameter two-column Isola spinal system implanted in a 13-year-old girl suffering from cerebral palsy and a severe neuromuscular scoliosis of 120 degrees, was replaced 22 months after primary implantation. The system was removed due to fracture of the lower left (concave) bar, between its two cross connectors (i.e., the distal bypass connector and a transverse cross link), as a result of a postoperative infection and a subsequently developed pseudarthrosis. The retrieved implants were analyzed with the use of a multitechnique characterization procedure involving macroscopic and microscopic examination, micro-multiple internal reflectance FTIR spectroscopy, X-ray fluorescence (XRF) spectrometry, roughness measurement, and mechanical testing of the constituent material and components. Findings suggest that the spinal system failed due to in vivo loosening of a two-set screw tandem connector and subsequent overloading of the contralateral bar.