Revision strategies for salvaging or improving failed cylindrical cages

Study Design. This is a review of 20 patients who experienced failure of th readed interbody fusion cages and underwent surgical correction. Objective. To review the causes and possible treatment strategies for faile d cylindrical cages. Summary of Background Data. Intraoperative complications have been describe d in the past; however, management of the postoperative patient with failur e of interbody fusion devices has not been described. Methods. In 20 patients with failed threaded titanium fusion cages (18 Bagb y and Kuslich Devices [BAK; Sulzer-Spine Tech, Minneapolis, MN], 2 Ray Thre aded Fusion Cages [Ray TFC; Surgical Dynamics, Norwalk, CT) who underwent r evision surgery, all had failure before successful arthrodesis was achieved . Eight of the original titanium cages had been inserted anteriorly (7 lapa roscopically), and 12 had been inserted for posterior interbody lumbar fusi on. Before the revision surgery, five of the implants were thought to be so lid by the referring surgeon, but pseudarthrosis was clearly present in all . In addition, 14 other explanted BAK devices were subjected to undecalcifi ed histologic preparation, quantitative histomorphometry, and histopatholog ic analysis. Results. The average length of time before revision surgery (implant durati on) was 31.8 weeks (range, 1-156 weeks). The most common revision procedure was posterior exploration of the symptomatic nerve root with foraminotomy for unrecognized lateral recess stenosis (ll;cases) or excision of iatrogen ically herniated intervertebral disc fragments (4 cases). However, four cag es inserted through posterior exposure during an interbody;lumbar fusion pr ocedure had to be removed because of migration into the spinal canal. In ni ne cases posterior pedicle screw instrumentation was necessary in addition to posterolateral fusion using iliac crest bone grafting. Conclusions. All 20 cages failed because of surgical technique rather than an intrinsic defect in fusion cage technology. The factors associated with failure of the original insertion procedure were failure to achieve adequat e distraction of the anulus fibrosis; undersized cages, especially when pla ced through the posterior interbody lumbar fusion approach; cerebrospinal f luid leakage or pseudomeningocele; Type 2 diabetes mellitus; the use of loc al bone graft rather than iliac crest inside the cage; anterior insertion i n an excessively lateral position resulting in symptoms of a far lateral di sc herniation; and failure to Identify the spinal midline during an anterio r approach.