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neural irritation because the successful interbody arthrodesis limits motion and allows the resorption of osteophytes and prevents further deterioration. Without the graft the normal process of aging, disc degeneration, continues. This would lead to changes in the adjacent vertebra, facet joint arthritis, osteophyte formation, thickening, and buckling of the ligamentum flavum, and degeneration of the uncovertebral joints, leading to further neural foraminal compression. Therefore, especially in the young, it is recommended that interbody fusion be completed as part of the anterior cervical microdiscectomy. The anterior approach was first introduced in the 1950s by Robinson and Cloward (4).
FUSION
There is no consensus on the type of fusion to be performed with anterior cervical microdiscectomy. The shape of the graft can be horseshoe, dowel graft, iliac strut graft or keystone graft; the strongest being the tricortical graft (16). The graft can be autograft, allograft or methacrylate. The allograft can be fresh frozen, freeze-dried, or gas sterilized. Fresh frozen allograft has been shown to have higher fusion rates than freeze-dried allograft (3). When using allograft, additional materials such as demineralized bone matrix, coral chips or methacrylate can be utilized. The intended result is successful interbody fusion without pseudoarthrosis or graft collapse. There have been several studies which compare the fusion rate of iliac crest autograft versus allograft. Pseudoarthrosis after anterior cervical fusion may be related to persistent neck pain and, therefore, an undesirable result. Newman reported 70% of his patients with pseudoarthrosis failed to achieve significant relief of their symptoms. Brunton had clinical failures in 19 of 20 patients with pseudoarthrosis, White had 47% clinical failures with pseudoarthrosis, as well as Farley had 83% failure with pseudoarthrosis, with complete resolution after successful fusion. Therefore, it is important to try to obtain successful fusion for the relief of clinical symptoms.
The use of autograft or allograft for single level fusion, yields similar clinical and radiographic results. Rish demonstrated fusion of 82% with autograft and 80% with allograft, Cloward (5) demonstrated 100% fusion with allograft, Zdeblick (18) showed 95% fusion for autograft and allograft, An demonstrated fusion in 74% with autograft and 54% with demineralized bone matrix allograft. Hanley demonstrated 92% fusion rates in both autograft and allograft. Graft collapse is also important and has been shown to occur more frequently with allograft than with autograft (18). The advantages of using allograft are that the operative time and hospitalization
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