Etiology and revision surgical strategies in failed lumbosacral fixation of adult spinal deformity constructs.

STUDY DESIGN: Retrospective case analysis.

OBJECTIVE: The purpose of this study was to evaluate the etiology and salvage strategies of failed lumbosacral fixation in adult spinal deformity patients.

SUMMARY OF BACKGROUND DATA: When extending a long spinal deformity fusion to the sacrum, the lumbosacral junction is a common site for implant problems and pseudarthrosis.

METHODS: Clinical and radiographic results of 33 patients (26 women/seven men; average age, 53.5 years; range, 21-73) diagnosed and treated for lumbosacral fixation failure between 1995 and 2007 were reviewed. Twenty-one of the 33 patients underwent revision surgery at one institution for these failures and were followed postoperatively for more than 2 years (average, 50.7 months).

RESULTS: Twenty-nine of these 33 patients had two sacral screws, two patients one sacral screw, and two patients none. Bicortical sacral screws were placed in 18 patients, only 12 had distal fixation to the sacral screws (bilateral iliac screws, n = 9; others, n = 3). Seventeen of 19 patients without distal fixation to the sacral screws had screw loosening/pullout at L5 or S1. Anteriorly at L5-S1: 4/6 bone grafts collapsed, 5 of 15 intervertebral discs without anterior column support collapsed, and two of 12 titanium cages subsided into the endplates. Rod breakage between L5 and S1 (n = 9) was seen only in patients with distal fixation to the sacral screws. Nineteen of 21 revision patients received two bicortical sacral screws, whereas 20 received distal fixation to the sacral screws consisting of bilateral iliac screws in 16. Nineteen patients received anterior column support at L5-S1. Fifteen of 21 revision patients achieved solid fusion at ultimate follow-up; however, six had additional rod breakage or dislodgement at the lumbosacral junction.

CONCLUSION: With long fusions to the sacrum in the treatment of spinal deformity, the use of bilateral S1 screws alone may allow for screw loosening/pullout and/or L5-S1 cage/graft collapse/subsidence. Adding bilateral iliac screws and an anterior structural cage/graft at L5-S1 will protect the S1 screws, but may still allow L5-S1 rod breakage/dislodgement because of lumbosacral pseudarthrosis. Revision surgery in these patients remains a challenge.