A therapeutic Level II study by DiGiovanni et al. in the August 3, 2016 edition of The Journal of Bone & Joint Surgery examined the relationship between successful foot/ankle fusions and the amount of graft material used. The authors found that among 573 procedures in which graft material (either autograft or AUGMENT bone graft) occupied ≥50% of the cross-sectional fusion space at nine weeks, 81% were successfully fused at 24 weeks. However, among 101 procedures with <50% of the graft space filled, only 21% were successfully fused at 24 weeks.
The authors determined both graft-fill percentages at nine weeks and fusion success at 24 weeks using CT scans. The percentage of graft fill was estimated by mental summation of graft fill present in each individual CT slice of the joint, and joint fusion was determined by measuring the percentage of osseous bridging in the same semiquantitative manner.
The significant fusion rate differences between joints with and without ≥50% graft fill were consistent regardless of whether autograft or allograft was used and regardless of which joint was fused. The authors conclude that these findings “demonstrated that when a surgeon can eliminate bone-to-bone gaps in any joint intended for fusion,…such a joint has a significantly better chance of ultimately achieving fusion,” although they caution against “overpacking a joint with excessive graft material.” DiGiovanni et al. cite the need for further research “to determine the ideal amount of graft material required for a clinically relevant and impactful effect on fusion” and to help develop “graft materials that are easier to introduce and can be more precisely inserted into the intended fusion space.”