A fifty-year-old man presented to the orthopaedic spine clinic in March 2007 with a chief complaint of severe low back and bilateral lower extremity pain. He had a complicated surgical history, beginning in 1977 with an L4-L5 level laminectomy that had been performed for the treatment of a work-related injury. In 1988, the patient had undergone a total disc arthroplasty at the L3-L4 level with use of a transperitoneal approach and the AcroFlex disc implant for the treatment of unremitting back pain (Fig. 1). The patient had persistent back pain after placement of the AcroFlex disc. Three months later, the patient underwent posterior lumbar interbody and posterolateral arthrodesis from L4 to S1 with pedicle screw fixation (Fig. 2). This procedure provided moderate pain relief for approximately four to five years. The back pain returned, and the posterior instrumentation was removed in the hope of reducing the symptoms. Unfortunately, removal of the instrumentation provided little benefit. By 1998, the total disc replacement was demonstrating evidence of wear as indicated by a loss of implant height, for which the surgeon considered explantation and arthrodesis. The revision surgery was abandoned because a preoperative venogram demonstrated complete occlusion of the left common iliac vein. Therefore, the patient was advised to seek nonoperative means of controlling the pain. Over the ensuing ten years, the patient sought the assistance of a number of pain specialists, who prescribed a combination of narcotics, muscle relaxants, antidepressants, and eventually, the placement of an intrathecal morphine pump. Nevertheless, the pain progressed and, nineteen years after the index arthroplasty, the patient was referred to our institution.
On physical examination, the patient had a flexible flat-back deformity. The patient was neurologically normal aside from decreased sensation on the dorsum of both feet. He had palpable dorsalis pedis pulses and no evidence of edema in either lower extremity.
Radiographs demonstrated complete loss of the polyolefin spacer, with the metallic end plates touching one another. This resulted in the generation of a substantial amount of metal debris as noted in the adjacent vertebral bodies (Fig. 3). The computed tomography myelogram better delineated the resultant osteolysis of the adjacent vertebral bodies. Large osteolytic defects could be seen extending toward and through the posterior cortex, communicating with the epidural space. The computed tomography scan also brought into question the quality of the L4-L5 and L5-S1 arthrodesis mass and demonstrated adjacent-level disc degeneration at L1-L2 and L2-L3 (Fig. 4). Interestingly, a preoperative venogram demonstrated that the left common iliac vein had completely recanalized.
Because of the amount of metal debris, concern regarding potential carcinogenicity8 of the rubber utilized in this prosthesis, and the lack of structural integrity of the involved vertebral bodies, the patient underwent removal of the total disc implant and a so-called 360° arthrodesis at the L3-L4 level. A general surgeon provided exposure to the involved levels through a retroperitoneal approach to avoid the previous scar tissue. The L3 and L4 vertebral bodies had massive osteolysis with weakened cortical bone. There was a large amount of black rubber and metal wear debris, requiring a subtotal corpectomy of the L3 and L4 vertebral bodies followed by the placement of a fresh-frozen humeral strut allograft. Histologic analysis of the vertebral tissue demonstrated reactive fibrosis (Fig. 5). Interestingly, there were chronic inflammatory cells. The patient was then turned prone, and a revision laminectomy and foraminotomy was performed at the L4-L5 level. Intraoperative inspection revealed motion at both the L4-L5 and L5-S1 vertebral segments, indicative of a chronic pseudarthrosis. Therefore, a posterior spinal arthrodesis from L1 to the sacrum was performed with pedicle screw instrumentation and iliac crest autograft. Postoperative radiographs demonstrated a substantial reestablishment of lumbar lordosis as compared with the preoperative flat-back deformity (Fig. 6). The patient tolerated the thirteen-hour operation without incident. The total blood loss was 4400 mL, and the patient received two units of packed red blood cells and 2000 mL of cell saver reinfusion (Cell Saver; Haemonetics, Braintree, Massachusetts) as well as other blood products and intravenous fluids. The patient had an uncomplicated postoperative course and was discharged on the seventh postoperative day, at which time he was walking independently. The patient has had no notable lower extremity edema. He was most recently seen in the clinic five months postoperatively. He reported subjective functional improvement and decreased use of methadone without the use of any intermediate analgesic medication, a substantial improvement from his preoperative analgesic requirement.