Prospective nonrandomized comparison of an allograft with bone morphogenic protein versus an iliac-crest autograft in anterior cervical discectomy and fusion

Abstract

Background context

Anterior cervical discectomy and fusion (ACDF) using autogenous iliac bone graft may lead to donor-site morbidity. This has led some surgeons to use alternatives to iliac bone graft, but often the alternatives have greater rates of nonunion and delayed union. Bone morphogenic protein (BMP) studies have found high arthrodesis rates in lumbar fusions.

Purpose

The objective of this pilot study was to compare the success of BMP combined with bone allograft with iliac bone autograft in ACDF patients.

Study design/setting

The institutional review board approved a prospective but nonrandomized study of 66 consecutive patients who had primary one- to three-level ACDF with either iliac-crest bone autograft or BMP allograft (0.9 mg BMP per level) followed prospectively over a 2- to 3-year period.

Patient sample

Consecutive patients who had primary one- to three-level ACDF with either iliac-crest bone autograft (n=36) or BMP-allograft (n=30). Patients in both iliac bone graft and BMP-allograft groups had comparable preoperative pain and disability.

Outcome measures

Visual analog scale pain, pain drawing, Oswestry index, pain medication use, opinion of treatment success, and neurological recovery.

Results

Given the nonrandomized nature of the study, the study groups were not matched. Within this limitation, both groups of patients had similar improvement in all outcome scales (visual analog scale pain, pain drawing, Oswestry index, pain medication use, and opinion of treatment success) and neurological recovery over the 2- to 3-year follow-up period. Patients in the iliac bone graft group had two pseudarthroses and two complications of the iliac-crest donor site. In the BMP-allograft group, one patient had a pseudarthrosis, but 50% had neck swelling presenting as dysphagia, which was substantially more common than the 14% present in the iliac bone graft group. Patients in the BMP-allograft group had slightly shorter surgery time, but implant and hospitalization costs were higher.

Conclusions

ACDF performed with BMP (0.9 mg BMP per level) allograft is as effective as iliac bone graft in terms of patient outcomes and fusion rates. Safety concerns related to neck swelling and higher initial costs were associated with patients in the bone morphogenic protein group.

Introduction

For patients for whom nonoperative treatment fails, anterior cervical discectomy and fusion (ACDF) using iliac-crest bone graft (IBG) usually results in both a solid fusion and clinical improvement for patients with degenerative cervical conditions [1], [2], [3]. IBG donor-site morbidity and pain have been reported to range from approximately 10% to 50% [4], [5], [6], [7], [8]. Because of these IBG-site problems, some surgeons have used alternatives to IBG, the most common being structural allograft bone. However, using allograft bone or other alternatives has shown greater nonunion rates, delayed unions, and higher rates of graft subsidence [9], [10], [11], [12]. Recent reviews and meta-analysis have concluded that autograft is superior to allograft bone for ACDF, particularly when more than one level was treated [9], [13]. Another alternative is to combine allograft bone with bone morphogenic protein (BMP). BMP is currently approved for use in the lumbar spine for interbody fusions, and prospective randomized studies of BMP combined with allograft have shown high fusion rates and improved clinical outcomes for lumbar spine applications [14].

The purpose of this pilot study was to assess the efficacy of BMP, when used in an off-label fashion and combined with allograft (fibular cortical ring), as an alternative to IBG for one to three-level ACDF. The BMP-allograft patients included in this study were assessed prospectively and compared with patients treated with traditional tricortical IBG over the same period. Patients in the two ACDF groups were followed radiographically and clinically at various time points over a 2- to 3-year period. This study specifically sought to determine the existence of a difference in clinical outcome, fusion rates, or complication rates between these two groups. A secondary purpose was to evaluate the financial burden of this new biotechnology when used in the cervical spine.

The study was preliminary in nature and was also intended to help identify and refine inclusion criteria for a larger randomized study. Readers should consider the present study only as a platform to a large-scale study that will more definitively establish the efficacy and safety of BMP-allograft use in the cervical spine.