Multilevel anterior cervical discectomy and fusion with and without rhBMP-2: a comparison of dysphagia rates and outcomes in 150 patients
Authors: Lu Daniel C. , Tumialán Luis M. , Chou Dean 
Published: November 2012

Object
Reported complications of recombinant human bone morphogenetic protein–2 (rhBMP-2) use in anterior cervical discectomy and fusion (ACDF) cases include dysphagia and cervical swelling. However, dysphagia often occurs after multilevel ACDF procedures performed with allograft (without BMP) as well. To date, there has been no large study comparing the dysphagia rates of patients who have undergone multilevel ACDF using allograft spacers with those who underwent ACDF using polyetheretherketone (PEEK) cages filled with rhBMP2. The authors report one of the first such comparisons between these 2 patient cohorts.

Methods
The authors retrospectively reviewed 150 patient records. Group 1 (BMP group) consisted of 100 patients who underwent multilevel ACDF with PEEK cages filled with rhBMP-2 and instrumented with a cervical plate. Group 2 (allograft group) included a matched control cohort of 50 patients who underwent multilevel ACDF with allograft spacers and anterior plate fixation (without rhBMP-2). Patient demographics were not significantly different between the groups. Fusion was assessed by means of dynamic radiographs and/or CT at routine intervals. Complications, dysphagia incidence, standardized dysphagia score, Nurick grades, and fusion rates were assessed.

Results
The mean follow-up for the BMP group (Group 1) was 35 months while the mean follow-up for the allograft group (Group 2) was 25 months. There was a complication rate of 13% in the BMP group compared with 8% in the allograft group (p < 0.005). There was no significant difference in overall dysphagia incidence between the BMP group and the allograft group (40% vs 44%, respectively; p > 0.05). However, there was a significant difference in the severity of dysphagia (using the SWAL-QOL dysphagia scoring system) between the 2 groups: 0.757 for the BMP group versus 0.596 for the allograft group (p < 0.005). In subgroup analysis, the use of rhBMP-2 significantly increased the severity of dysphagia in patients undergoing 2-level ACDF (p < 0.005). However, the severity of dysphagia did not differ significantly between groups when 3- or 4-level ACDF cases were compared. There was no pseudarthrosis in Group 1 (the BMP group) compared with a 16% pseudarthrosis rate in Group 2 (the allograft group) (p < 0.05). There was a weak correlation between the total rhBMP-2 dose and the dysphagia score (Kendall tau rank correlation coefficient 0.166, p = 0.046).

Conclusions
The use of rhBMP-2 in patients undergoing 2-level ACDF significantly increases the severity of dysphagia (dysphagia score) without affecting the overall incidence of dysphagia. However, there is no statistically significant difference in the incidence or severity of dysphagia between patients undergoing 3-level or 4-level ACDF treated with PEEK/rhBMP-2 and those treated with only allograft. The use of rhBMP-2 appears to reduce the risk of pseudarthrosis. This benefit is most pronounced in patients who undergo 4-level ACDF and are smokers.