Cervical Spine Fusion: Allograft versus Autograft

Published on 27/03/2015 by admin

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Chapter 216 Cervical Spine Fusion

Allograft versus Autograft

Argument for Allograft

Ventral approaches to the cervical spine were first introduced in the 1950s by Smith and Robinson,1 Cloward,2 and Bailey and Bagley.3 Early surgical techniques used autologous bone grafts. The longevity of these procedures is a testament to their efficacy. However, the use of autologous bone graft is unavoidably coupled with donor site morbidity. In an attempt to eliminate donor site morbidity, the use of allograft was proposed as early as the late 1950s. Since that time, allograft has been used in spinal fusions and has met with varying degrees of success. Allograft provides a comparable means to autograft by which to obtain spinal fusion while eliminating donor site morbidity.

Review of the literature reveals that allograft provides fusion rates and clinical outcomes similar to those obtained by autograft for single-level interbody cervical fusions.410 Multilevel interbody fusions are associated with increased nonunion rates and graft complication with both autograft and allograft.4,5,10,11 Nonunion rates and graft complications have been shown to increase with the number of motion segments fused with both autograft and allograft. 4,5,10,11

Various modifications in surgical technique and the use of rigid external fixation, dorsal cervical instrumentation, and, most recently, ventral cervical instrumentation have been tried in an attempt to improve fusion rates for multilevel interbody cervical fusions. The use of ventral cervical instrumentation as an adjunct to multilevel interbody cervical fusions has been shown to increase fusion rates, improve clinical outcomes, and reduce graft complication.1215 For multilevel interbody cervical fusions, the combination of allograft supplemented with ventral cervical instrumentation has been shown to provide similar fusion rates and clinical outcomes to those obtained with autograft and ventral cervical instrumentation.12,13,15,16

Single-level or multilevel corpectomies are used for the treatment of degenerative, congenital, traumatic, infectious, and neoplastic disorders of the cervical spine. Stabilization of decompressed segments presents spine surgeons with a formidable challenge. Numerous surgical techniques with various types of grafts have been proposed and used with varying degrees of success. As with multilevel interbody cervical fusions, single-level or multilevel corpectomies have an increasing rate of nonunion and graft complications as the number of motion segments fused increases, for both autograft and allograft.5,11 The literature is inconclusive regarding the ideal graft for single-level or multilevel corpectomies. Some authors find autograft to be significantly superior to allograft, with increased fusion rates and decreased graft complications.5,11,17 While other authors have found no difference between allograft and autograft, they have observed an increased time to incorporation of the graft.6,18,19

Modifications in surgical techniques and the use of rigid external fixation, dorsal cervical instrumentation, and, most recently, ventral cervical instrumentation have been used in an attempt to improve fusion rates in single- or multilevel corpectomies. The addition of ventral cervical instrumentation provides immediate cervical spine stability, improves fusion rates, and limits graft complications.121620

Various authors have found no difference in fusion rates, clinical outcome, and graft complications when comparing allograft and autograft supplemented with ventral cervical instrumentation for single-level and multilevel corpectomies.16,20,21 Most recently, Mahr et al.21 reported radiographic stability in 99.2% of their patients who underwent cervical corpectomies with fibular allograft reconstruction and ventral cervical instrumentation.

Allograft eliminates harvest site morbidity. Donor site morbidity has been reported to range from 9% to 29%.2,13,15,16,18,20,21 Harvest site complications include wound hematomas, osteomyelitis, wound infections, lateral femoral cutaneous nerve neurapraxia, fractures of the anterior superior iliac spine, and bowel perforations.13,17,22 In a study by Rawlinson,22 36% of patients had persistent donor site pain at 1 year after graft harvest. Rawlinson reported that in 45% of the patients in his study, “donor site pain had delayed their mobilization.”17 Thirty-one percent of patients in his study felt that they could have gone home sooner if not for donor site pain.16 Other advantages of allograft include decreased operative time and blood loss.9,15,16,20,21

Allograft carries the potential for transmission of infectious diseases. However, the risk of acquiring HIV infection from allograft has been estimated to be between one in 1 million and one in 1.6 million.16,21 Strict regulations regarding the testing, harvesting, treatment, handling, and storage of allograft should serve to minimize the risk of acquiring infectious disease via the implantation of allograft.

Finally, the cost of bone graft harvest has been shown to be similar to the cost of purchasing allograft and ventral cervical instrumentation.23