Increased incidence of cage migration and nonunion in instrumented transforaminal lumbar interbody fusion with bioabsorbable cages

Abstract

Recent advances in the field of spinal implants have led to the development of the bioabsorbable interbody cage. Although much has been written about their advantageous characteristics, little has been reported regarding complications associated with these cages. The authors conducted this prospective cohort study to compare fusion and complication rates in patients undergoing transforaminal lumbar interbody fusion (TLIF) with carbon fiber cages versus biodegradable cages made from 70/30 poly(l-lactide-co-d,l-lactide) (PLDLA). Between January 2005 and May 2006, 81 patients with various degenerative and/or structural pathologies affecting the lumbar spine underwent single- or multilevel TLIF with posterior segmental pedicle screw fixation using implants made of carbon fiber (37 patients) or 70/30 PLDLA (44 patients). Clinical and radiological follow-up was performed at 6 weeks, 3 months, 6 months, and 1 year, and is ongoing. The incidence of nonunion, screw breakage, and cage migration were compared between the 2 groups. There was no significant difference in demographic data between the 2 groups, the mean number of lumbar levels operated, or distribution of the levels operated. There was a significantly increased incidence of nonunion (8 patients, 18.2%) and cage migrations (8 patients, 18.2%) in patients receiving the PLDLA implants compared with carbon fiber implants (no patients) (p = 0.006 and 0.007, respectively). There was no significant difference in demographic data between patients with cage migration and the rest of the patient population. Five of the 8 cases of migration occurred at the L5-S1 level while the remaining 3 occurred at the L4-5 level. The mean time to implant failure was 9.3 months. This study showed an increased incidence of nonunion (18.2%) and postsurgical cage migration (18.2%) in patients undergoing TLIF with biodegradable cages versus carbon fiber implants (0%) (p = 0.006 and 0.007, respectively).