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Outcome study of BAK cages for interbody fusions with unilateral pedicle screw fixation of the lumbar spine.

1 August 2002


Object- The purpose of this study was to determine the outcome of adult patients who underwent BAK Cage (manufactured by Spine Tech of Minnesota) implants which were secured with unilateral pedicle screw fixation instrumentation. Patients were treated with BAK cages for a myriad of lumbar spine conditions. As a subpopulation the purpose of this study was also to determine outcome in failed back syndrome in populations of adult patients who were diagnosed with failed back syndrome. Functional, anatomical, economical outcome was assessed, as well as fusion rate, activity limitations, and patient perception of surgical success.

Methods- 41 patients with spondylolisthesis, herniated discs, recurrent discs, degenerative disc disease, stenosis, radiculopathy, or failed back syndrome at one or two lumbar levels were selected for the retrospective study. All patients underwent discetomy, BAK cage implant with allograft or autograft bone and fixated with unilateral pedicle screws. Patients were selected in consecutive order who had undergone fusion between June 2000 and December of2001. They were identified by CPT codes 22851, 22612, 22610. No one was excluded from the study. Patients were then followed in clinic for routine follow up with films. Patients were interviewed via telephone or with a questionnaire using a modified Prolo score to assess functional status and economic status. In addition a FS-36 Health Survey assessed other medical conditions such as depression which may hinder the ability to return to optimal functioning status.

Conclusions- There was a 93% fusion rate, 5% pseudarthrodosis rate, and 2% instrumentation explantation rate in which one patient auto fused. Complications were two infections, one superficial and one deep. There were four incidental durotomies, and one patient required re-operation due to cauda equina syndrome which developed 24 hours postoperatively. Fifty percent of patients who responded to survey had a primary or secondary diagnosis of failed back syndrome. There was no difference between overall outcome of main patient population and subpopulation of failed back syndrome patients. There were no life threatening complications and no instrumentation failure occurred. 72% of patients showed an increase in AEF scores, 9% showed a decrease and 19% showed no overall change in AEF scores. 51% showed a Prolo score of good or excellent. 84% of patients reported fair, good, or excellent outcomes and 68% of those reported good or excellent results of spinal fusion.


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