Study Design. Prospective, randomized, controlled trial.
Objective. To compare arthrodesis rates between patients undergoing a primary single-level minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) with either Actifuse or recombinant human bone morphogenetic protein-2 (rhBMP-2).
Summary of Background Data. Preclinical animal studies suggest that silicate-substituted calcium phosphate (Actifuse) bone graft substitute offers equivalent or an increased fusion rate compared with other graft enhancers/extenders and rhBMP-2.
Methods. Fifty-two patients undergoing a single-level unilateral MIS TLIF were evenly randomized into 2 cohorts as follows: the Actifuse cohort received Actifuse combined with 5 mL of bone marrow aspirate (n = 26; 50%), whereas the rhBMP cohort received 4.2 mg of rhBMP-2 (n = 26; 50%). A pre hoc G*Power analysis yielded a sample size of n = 26 that was determined through a 2-tailed distribution calculation. Computed tomographic analysis was performed at 6 months and 1 year postoperatively. Pre- and postoperative visual analogue scale scores were obtained to assess the clinical outcomes. Arthrodesis was determined by 2 separate, blinded orthopedic surgeons and a board certified radiologist.
Results. At 1-year follow-up, 65% (17/26) of the Actifuse cohort and 92% (24/26) of the rhBMP-2 cohort demonstrated a radiographical arthrodesis (P = 0.01). In both study cohorts, the 1-year postoperative visual analogue scale scores significantly improved (P < 0.001). Pseudarthrosis rates at 1 year were 35.0% (9/26) and 7.7% (2/26) for the Actifuse and rhBMP-2 groups, respectively (P = 0.01, OR = 6.35, 95% CI = 1.22–33.1). A greater reoperation rate was noted in the Actifuse cohort (35.0%, 9/26) compared with the BMP-2 cohort (7.7%, 2/26; P = 0.01). One patient with BMP-2 also experienced symptomatic neuroforaminal bone growth (3.8%, n = 1/26).
Conclusion. Silicate-substituted calcium phosphate was associated with a significantly lower rate of arthrodesis than rhBMP-2 in a MIS TLIF. The patients with pseudarthrosis in both cohorts were all clinically symptomatic with an unimproved visual analogue scale score. Additional analysis of Actifuse and other graft enhancers/extenders are needed prior to the utilization for an MIS TLIF.
Level of Evidence: 2
In this prospective, randomized, controlled trial in the setting of a minimally invasive transforaminal lumbar interbody fusion, the Actifuse cohort demonstrated a lower arthrodesis rate and higher reoperation rate, at 1-year follow-up, than the recombinant human bone morphogenetic protein-2 cohort. One-year visual analogue scale scores were unimproved among patients in both cohorts with a computed tomography confirmed pseudarthrosis.
From the Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL.
Address correspondence and reprint requests to Kern Singh, MD, Department of Orthopaedic Surgery, Rush University Medical Center, 1611 W. Harrison St., Ste 400, Chicago, IL 60612; E-mail: Kern.email@example.com
Acknowledgment date: June 26, 2013. First revision date: August 14, 2013. Second revision date: September 23, 2013. Acceptance date: October 21, 2013.
The device(s)/drug(s) that is/are the subject of this manuscript is/are being evaluated as part of an ongoing FDA-approved investigational protocol (IDE) or corresponding national protocol.
No funds were received in support of this work.
Relevant financial activities outside the submitted work: board membership, consultancy.