**2.2 Posterolateral lumbar fusion**

The efficacies of rhBMP-2 have been studied and reported over the past few years. Boden et al. in their prospective randomized multicenter clinical trials demonstrated that the administration of rhBMP-2 in posterolateral lumbar fusion (PLF) [19]. They compared the effect of rhBMP-2 in patients with suffering from degenerative disc disease following PLF [20]. The patients were divided into three groups: autograft with pedical screw fixation, rhBMP-2 with pedical screw fixation, and rhBMP-2 without pedical screw fixation [21]. They concluded that they


### **Table 1.**

*Showing the rates of fusion and adverse events associated with the application of rhBMP-2.*

recorded a 100% fusion rate in the rhBMP-2 groups compared to the 40% fusion rate in the autograft group was 40.

Carreon and colleagues in their study, compared the application of autograft and higher dose rhBMP-2 in single-level of PLF case was carried out [22]. They concluded in their study that they recorded an 89% and 96% fusion rate in the autograft group and rhBMP- 2/CRM group respectively at 2 years follow-up. However they also recorded no similar clinical outcome measures between the two compared groups [23]. There have also been few smaller studies that reported related results of high fusion rates with the use of rhBMP-2 in PLF compared to ICBG [24].

### **2.3 Posterior lumbar interbody fusion**

Haid and co-worker reported the efficiency of rhBMP-2 in posterior lumbar interbody fusion (PLIF), however there is a possibility for heterotopic bone formation. Haid and co-workers reported that they recorded 92.3% and 77.8% fusion rate with rhBMP-2 group and control group respectively, however there was an insignificant difference in clinical progress between the two compared groups [25]. They also reported via CT imaging that there was formation of ectopic bone around the PLIF [26].

### **2.4 Anterior cervical fusion**

Baskin and colleague reported that there was a 100% fusion rate with the administration rhBMP-2 when compared with autograft [28]. Furthermore, they reported that the efficiency of rhBMP-2 was further improved when collagen sponges, PEEK cages, bioab- sorbable spacers, and allograft rings were added to it [29]. However, the positive results have been marred by reports of the incidence of soft-tissue related complications including potentially life-threatening airway compromise from tissue swelling. Cole, Veeravagu [30] conducted a MarketScan database-based retrospective study regarding the use of rhBMP in anterior cervical discectomy and fusion procedure. The outcomes of the study indicated that the use of drug is associated with increased incidence of hematoma, seroma, dysphagia, and pulmonary complications. Low dose rhBMP is also not associated with reduced incidence of the postoperative complications [31]. The FDA has placed a black box warning on the use of rhBMP-2 in the anterior cervical spine indicating that the risk of use may outweigh the benefit and therefore, its use is not recommended in anterior cervical fusion.

### **2.5 Transforaminal lumbar interbody fusion**

There have been studies to investigate the efficiency of rhBMP-2 on transforaminal lumbar interbody fusion (TLIF, **Figure 2**). Villavicencio et al., in their clinical study on 74 patients, underwent single and multiple- level TLIF administered with rhBMP-2 and combined with auto- graft [33]. They recorded that there was radiographic evidence of fusion in all 74 patients after 10 months [34]. Furthermore, they recorded few adverse events in the rhBMP-2 group noting two patients developed postoperative radiculitis. In another similar study by Rihn et al., 48 patients underwent single-level TLIF administered with rhBMP-2 [35]. They concluded radiographic fusion, improved clinical outcomes and satisfaction with surgical results in 95.8%, 83% and 84% of the patients, respectively. However, 27.1% of their patients had complications like transient postoperative radiculitis and symptomatic ectopic bone formation (**Table 2**).

*Application of Bone Morphogenetic Protein in Spinal Fusion Surgery DOI: http://dx.doi.org/10.5772/intechopen.96883*

### **Figure 2.**

*An axial CT scan of the lumbar spine demonstrating ectopic bone formation (arrow) in the left neural foramen impinging on the exiting nerve root in a patient who underwent a transforaminal lumbar interbody fusion with rhBMP-2. Culled from [32].*


### **Table 2.**

*Showing alternative therapies to the use of rhBMP-2.*

### **3. Conclusion**

The use of rhBMP-2 offers an alternative therapeutic option when iliac crest autograft is either unavailable or may result in severe side effects. There are various clinical studies investigating how the use of rhBMP-2 can be effective in achieving spinal fusion. However, though rhBMP-2 is effective at achieving spinal fusion patients need to be informed of the possible formation ectopic bone requiring additional surgery and seroma formation when preforming transforaminal lumbar interbody fusion. There is a need for further study to minimize or lower the rates of complication linked with the application of rhBMP-2.

### **Conflict of interest**

The authors deny any conflict of interest in any terms or by any means during the study.
