Recognition of posterior thoracolumbar instrumentations used in spinal deformity surgery and techniques for implant removal.

Spinal surgeries requiring implant removals/revisions are becoming more common, as a long time has passed since contemporary spinal instrumentation was developed and utilized. Recognizing implants and manufacturers preoperatively from radiographs and preparing appropriate instruments for removal are mandatory. The objective of the present paper was to review the various designs of contemporary posterior thoracolumbar spinal implants along with their radiographic features to facilitate the identification of previously used systems in removal or revision surgeries. We focused on contemporary spinal implants that have been commonly used in spinal deformity surgery since the development of screw-and-rod constructs up to 2005. The pertinent information was requested from three major manufacturers (DePuy Synthes, Medtronic and Stryker). Characteristics of each system are reviewed with radiographic features, and the instruments needed for revision are summarized. We propose a systematic identification diagram. Rod loading can be categorized as offset-loading, side-loading or top-loading. Screw design can be cylindrical, conical or dual-core threading. Each system has unique features that can facilitate identification. Identifying the materials and diameters of the rod is also imperative. When removal of an unidentified system is needed or removal of an identified system fails, the short rod has to remain loaded on the screw and the implant removed en bloc as an isolated piece. Understanding the radiographic features of spinal implants used in previous surgeries will help surgeons prepare for the increasing incidence of revision surgeries.