A Preliminary Report on the FRA Spacer: Uniform Allograft for Anterior Interbody Fusion of the Lumbar Spine

Introduction:

The inherent problems with bone bank allograft include variable fusion rates, increasing cost, difficult technique, and pseudarthrosis due to inadequate fit within the disc space.

Materials & Methods

The FRA Spacer is a manufactured, uniform, wedge–shaped, femoral ring allograft. In this initial series, 44 patients underwent successful anterior interbody fusion with the FRA Spacer. All patients also had transiaminar or transpedicular fixation and posterolateral fusion with 33 tolerating both procedures on the same day. There were 25 single–level, 17 double–level, and 2 triple–level fusions – a total of 65 spacers.

Results:

Technically, the FRA performed well. Three spacers (4.4%) were broken upon insertion and replaced perioperatively. Postoperatively, 1 FRA fractured (1.5%) two days postop and was replaced without sequelae. One FRA protrusion of 5 mm occurred within 6 weeks of insertion but it was not revised. All other spacers remained fully intact. Follow–up is limited in this series to an average of 12 months with a range of 6–18 months. There was no evidence of subsidence or graft collapse. One hardware removal identified a pseudarthrosis. Halos of greater than 25% were evident with respect to six (6) spacers at six or 12 months postop. All other spacers (89%) show partial or complete incorporation at 12 or 18 months postop. Mean pain decreased 56% from preoperative levels.

Conclusion:

The FRA Spacer offers several technical advantages over bone bank femoral ring allograft. However, long–term follow–up is necessary for comparative radiographic and clinical results to both bone banked allograft and anterior fusion devices.