STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Compare the efficacy of rhBMP-2 and bone marrow aspirate with allograft (BMAA) as alternatives to autograft in instrumented revision posterolateral lumbar fusion (PLF).

SUMMARY OF BACKGROUND DATA

The use of autogenous bone graft is the current gold standard in revision PLF; however, this practice is associated with significant donor-site morbidity. Revision PLF pose the additional challenges of a less than ideal fusion environment and a limited quantity of autogenous bone graft. rhBMP-2 and BMAA have been shown to be acceptable bone graft substitutes in several primary orthopedic procedures. The role of these bone graft substitutes in instrumented revision PLF has yet to be determined.

METHODS

Sixty-two patients (125 levels) who underwent instrumented revision PLF with a minimum 2-year follow-up were included. Group 1 contained 24 patients (13 single- [group 1A] and 11 multilevel [group 1B]) who underwent instrumented revision PLF using rhBMP-2 on an absorbable collagen sponge. Group 2 included 18 patients (7 single- [group 2A] and 11 multilevel [group 2B]) with procedures using BMAA. Group 3 consisted of 20 patients (10 single- [group 3A] and 10 multilevel [group 3B]) with procedures using autograft. Demographic, surgical, and clinical data were collected from medical records. Time to solid fusion mass formation, fusion rate, complications, and clinical outcomes were evaluated. The progression of the fusion mass was evaluated by reviewing radiographs. A diagnosis of nonunion was based on exploration during an additional revision surgery or evidence of nonunion on dynamic radiographs or computerized tomography. Clinical outcomes were assessed using a visual analog scale (VAS) before surgery and at 6-week, 6-, 12-, and 24-month follow-ups.

RESULTS

Overall fusion rate was 93.5% (58/62). All single-level revision PLF achieved solid fusion. Groups 1B and 3B achieved 100% fusion, (11/11) and (10/10), respectively;whereas group 2B had a fusion rate of 63.6% (7/11). Group 1 also developed a solid fusion mass earlier than the other groups. There was a significant decrease between preoperative and 2-year postoperative VAS scores in all groups, but no significant difference among groups. Three patients in group 2 required an additional revision surgery.

CONCLUSION

rhBMP-2 may be an appropriate alternative to autogenous bone graft in both single- and multilevel revision PLF, whereas BMAA may be appropriate as a substitute in single-level revision PLF. The use of BMAA in single-level revisions may be a more cost-effective option than rhBMP-2.