Posterior Interbody Fusion: A Comparison of Stand Alone Threaded Cages Vs. Allograft Spacers with Pedicle Screws

PURPOSE: The advent of novel interbody devices has increased interest in posterior lumbar interbody fusions (PLIF). There are several surgical methods which include the use of threaded interbody cages as well as allograft spacers. The intent of this study was to compare the incidence of complications between two commonly employed techniques for PLIF: (1) stand-alone threaded cages placed from a posterior approach and (2) allograft spacers supplemented with pedicle screw fixation.

METHODS: Thirty-one patients treated with posterior lumbar interbody fusion using allograft bone spacers supplemented with pedicle screws and 15 patients treated with stand-alone threaded interbody cages were examined. Surgical data was obtained directly from medical records. The findings compared included blood loss, need for blood transfusion, number of units transfused, operative time, need for future revision surgery and complication rate.

RESULTS: There was a significantly lower incidence of complications (6% vs. 33%) for patients undergoing posterior lumbar interbody fusion using allograft spacers with supplemental pedicle screws (p<0.01). Two intraoperative dural tears without cerebrospinal fluid leaks occurred in patients undergoing posterior lumbar interbody fusion using allograft spacers and pedicle screws. Four dural tears with cerebrospinal fluid leaks and one postoperative pseudomeningocele requiring open drainage occurred in patients undergoing lumbar fusion with threaded fusion cages. There was no significant difference in blood loss, need for transfusion, amount of blood transfused or operative time (p<0.01).

CONCLUSIONS: Patients undergoing posterior lumbar interbody fusions with allograft bone spacers with supplemental pedicle screws had a significantly less incidence of complications than those undergoing fusion with stand-alone threaded fusion cages.