INTRODUCTION:

A number of bone graft substitutes that claim to be both osteoconductive and bioactive (sometimes termed ‘osteostimulative’) are now available. They proport to combine the advantages of osteoconductive and osteoinductive graft substitutes without the associated drawbacks and complications. The aim of this study was to evaluate the clinical and radiological effectiveness of three such bone graft substitutes used in patients undergoing single level lumbar fusion.

METHODS:

A consecutive series of patients undergoing primary single level transforaminal lumbar interbody fusion (TLIF) for degenerative lumbar conditions were allocated either BonAlive® putty MIS (BonAlive® Biomaterials Ltd., Turku, Finland) (n=20) or NanoBone® SBX putty (Artoss GmbH, Rostock, Germany) (n=19) bone graft substitute and prospectively studied. The graft was used alone (without autologous supplementation) in the cage, in the disc space and in the lateral gutters. This data was then compared with a historical cohort comprised of patients who had previously undergone primary single level TLIF using Actifuse (Baxter, Unterschleißheim, Germany) bone graft substitute in a similar fashion (n=63). Fusion rate was assessed at 12 months postoperatively using computed tomography (CT) by an independent radiologist blinded to bone graft type. Radiological parameters included bone growth through the cage, bone growth around the cage, new end-plate cyst formation and new end-plate sclerosis. Patient reported outcome measures were assessed via the Oswestry Disability Index (ODI), and the Back and Leg Visual Analog Scale (VAS) preoperatively and at 6 weeks, 6 months, and 12 months postoperatively.

RESULTS:

There was no statistical difference in fusion rates between groups, with BonAlive® achieving a rate of 80%, NanoBone® a rate of 84% and Actifuse a rate of 87% at 12 months. The presence of new endplate sclerosis was significantly lower (p=0.016) with Actifuse (24%) than with BonAlive® and NanoBone® (55% and 42%). There was no significant difference in new endplate cyst formation; BonAlive® 30%, NanoBone® 32% and Actifuse 17%. There were no significant differences for ODI, back VAS and leg VAS between the groups at any of the postoperative timepoints. At 12 months BonAlive® patients had an improvement in ODI of 58%, NanoBone® patients an improvement in ODI of 59% and Actifuse an improvement in ODI of 66%, compared with baseline. Four patients did not reach minimally clinically important difference in ODI and VAS improvement: 2 in the BonAlive® group, 1 in the NanoBone® group and 1 in the Actifuse group. There were no significant graft-related complications. There were no reoperations.

DISCUSSION:

All three bone graft materials exhibited similar radiological results and patient reported outcomes. Results were comparable with other materials and techniques to the point that these bone graft substitutes could be considered as satisfactory replacements for autologous bone graft.