Fractured Steinmann Threaded Fixation Pins Following Vertebral Body Resection and Stabilization: Medical Device Pathological Analysis of Two Cases

Abstract

ABSTRACTVertebral body resection in the treatmenL of metastatic neoplasms of the spine is increasingly common for radioresistant tumors. It is also favored for treating progressive neurological disease due to tumor-associated spinal cord compression. Spine stabilization following resection is accomplished by several techniques. Increasing in popularity is the combination of threaded fixation pins and methylmethacrylate filler.In the two cases reported in this communication, failure of threaded AISI 316 stainless steel pins occured through corrosion fatigue. Corrosion begins at the base of the threads and is exacerbated by galvanic cell formation at the methyl methacrylate-bone interface. Fatigue is experienced because the cervical and vertebral bodies are each a part of a joint that normally experiences 10 – 20 degrees of both antero-posterior and lateral flexion.We conclude that in active patients, non-threaded cobalt chrome pins are the preferred material for stabilization of the lumbar and cervical spine following vertebral body resections.