Bilateral pedicle fractures following anterior dislocation of the polyethylene inlay of a ProDisc® artificial disc replacement -: A case report of an unusual complication

Study Design. An unusual complication resulting from an artificial disc replacement for lumbar degenerative disc disease and its treatment are reported Objective. To describe the clinical circumstance, radiologic findings, treatment, and outcome of bilateral pedicle fractures associated with dislocation of the polyethylene inlay of a ProDisc® replacement at L5/ S1 level. Summary of Background Data. To the authors' knowledge, no published reports in the English literature have described bilateral pedicle fractures following a single level artificial lumbar total disc replacement. Methods. A 30- year- old male underwent a ProDisc® total disc replacement at L5/ S1 level for discogenic pain. Six- week postoperative assessment showed improvement in the visual analog and Oswestry scores. Assessment at 18 weeks postoperatively for acute pain revealed an anterior slip of the superior plate component, and computerized tomography showed bilateral pedicle fractures of the fifth lumbar vertebra. At surgery, the poly insert was found to have dislocated anteriorly. A salvage interbody fusion was then performed using the standalone anterior lumbar interbody fusion cage. Results. The most recent review confirmed radiologic evidence of fusion with improvement in the subjective evaluation scores Conclusions. We hypothesize that the current implant design in which the contribution to lordosis angle is purely from the superior component may be responsible for the reported complication. We suggest that dividing the contribution equally between both endplates might increase the stability, and this has been discussed with the manufacturers.