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Posterior Cervical Fusion With Recombinant Human Bone Morphogenetic Protein-2: Complications and Fusion Rate at
Ian G Dorward1, Jacob M Buchowski, Geoffrey E Stoker
1Departments of *Neurosurgery†Orthopaedic Surgery, Washington University School of Medicine, Saint Louis, MO.
Study Design:
Retrospective case series.
Objective:
The purpose of this study was to determine the fusion rate and evaluate the complications associated with the application of recombinant human bone morphogenetic protein-2 (rhBMP-2) in posterior cervical fusion.
Summary Of Background Data:
The rates of fusion and complications associated with the use of rhBMP-2 in posterior cervical fusion is unclear, though recent work has shown up to a 100% fusion rate.
Methods:
We independently reviewed consecutive series of patients who underwent posterior cervical, occipitocervical, or cervicothoracic instrumented fusion augmented with rhBMP-2. Two surgeons at a tertiary-referral, academic medical center performed all operations, and each patient had a minimum of 2-year follow-up. Fusion status was determined by bony bridging on computed tomography scans, absence of radiolucency around instrumentation, and absence of motion on lateral flexion/extension radiographs.
Results:
Fifty-seven patients with a mean age of 56.7±13.2 years and mean follow-up of 37.7±20.6 months were analyzed. Forty-eight patients (84.2%) had undergone previous cervical surgery, and 42.1% had a preexisting nonunion. Constructs spanned 5.6±2.6 levels; 19.3% involved the occiput, whereas 61.4% crossed the cervicothoracic junction. The mean rhBMP-2 dose was 21.1±8.7 mg per operation. Iliac crest autograft was used for 29.8% of patients. Six patients (10.5%) experienced nonunion; only 2 required revision. In each case of nonunion, instrumentation crossed the occipitocervical or cervicothoracic junction. However, none of the analyzed variables was statistically associated with nonunion. Fourteen patients (24.6%) suffered complications, with 7 requiring additional surgery.
Conclusions:
The observed fusion rate of rhBMP-2-augmented posterior cervical, occipitocervical, and cervicothoracic fusions was 89.5%. This reflects the complicated nature of the patients included in the current study and demonstrates that rhBMP-2 cannot always overcome the biomechanical challenges entailed in spanning the occipitocervical or cervicothoracic junction.
