Computerized tomography evaluation of a resorbable implant after transforaminal lumbar interbody fusion

Synthetic bioabsorbable implants have recently been introduced in spinal surgery; consequently, the indications, applications, and results are still evolving. The authors used absorbable interbody spacers (Medtronic Sofamor Danek, Memphis, TN) packed with recombinant bone morphogenetic protein (Infuse; Medtronic Sofamor Danek) for single- and multiple-level transforaminal lumbar interbody fusion (TLIF) procedures over a period of 18 months. This is a consecutive case series in which postoperative computerized tomography (CT) scanning was used to assess fusion status.

There were 22 patients (17 men, five women; 39 fusion levels) whose mean age was 41.6 years (range 23-70 years) and in whom the mean follow-up duration was 12.4 months (range 6-18 months). Bridging bone was noted as early as the 3-month postoperative CT scan when obtained; solid arthrodesis was routinely noted between 6 and 12 months in 38 (97.4%) of 39 fusion levels. In patients who underwent repeated CT scanning, the fusion mass appeared to increase with time, whereas the disc space height remained stable. Although the results are early (mean 12-month follow-up duration), there was only one noted asymptomatic delayed union/nonunion at L5-S1 in a two-level TLIF with associated screw breakage. There were no infections or complications related to the cages.

The bioabsorbable cages appear to be a viable alternative to metal interbody spacers, and may be ideally suited to spinal interbody applications because of their progressive load-bearing properties.