Cervical spine pathology arising from degenerative disease, tumor, trauma, or infection may present with multilevel involvement. When the pathology involves ventral compression of the neural elements, as commonly occurs with cervical stenosis, ventral decompression may be necessary. With simple discectomy, spinal canal and foraminal decompression can be difficult, inadequate, or both because the exposure is limited to the intervertebral space. In circumstances where multilevel reconstruction with graft stabilization is preferable to multilevel discectomy, a long segment corpectomy allows a wider neural decompression to be performed safely and under direct visualization.

Restoring biomechanical stability to obtain alignment, promote bone fusion, and protect the neural elements is best accomplished in some patients with multilevel corpectomy and long strut grafts. The length of the strut graft depends on the number of levels that need decompression. Cervical corpectomy and fusion with strut grafting is associated with excellent results in terms of neurologic recovery and high fusion rates (1, 2 and 3). However, strut grafts are known to be vulnerable to graft migration and displacement (4, 5, 6, 7 and 8). These are among the more serious complications of this procedure with potential for neurologic, esophageal, or airway compromise. A thorough understanding of the various causes, technical considerations, biomechanical effects, and patient factors is essential for successful avoidance and management of graft displacement and related complications.

Besides requiring revision surgery to replace the graft and augment stabilization, migration or dislodgement of long strut grafts may impinge on surrounding vital anatomic structures or result in a pseudarthrosis (1,4—8). Dorsal graft migration can lead to compression of the spinal cord, resulting in neurologic injury. The esophagus can become compressed or perforated by a ventrally dislodged graft, and tracheal impingement may produce airway obstruction. Despite these serious potential consequences, the incidence of graft displacement remains incompletely defined. Because the overall incidence is relatively low, factors contributing to graft migration are also not completely understood.

High complication rates of up to 60% have been reported when performing multilevel cervical corpectomy and reconstruction (4,9). Graft dislodgment is reported in 5% to 50% of multilevel corpectomy patients when stand-alone grafts have been placed with or without ventral plating (9,10). Thirty to fifty percent of complications following multilevel corpectomy and fusion relate to graft and instrumentation issues, which carry a significant reoperation rate (4—12).

Zdeblick and Bohlman (11) reported a 33% construct failure rate when using stand-alone fibular allograft in patients with cervical kyphosis and myelopathy. All of these patients required reoperation for graft extrusion. Vaccaro et al. (9) noted similar results, with a 9% failure rate in patients undergoing two-level corpectomy and fusion with plating and a 50% failure rate for three-level corpectomy and fusion with plating. Sasso et al. (10) reported a 6% failure rate in their patients who underwent cervical spine locking plate augmented two-level cervical corpectomy and fusion, but a 71% (5/7) failure rate after three-level fixedplated cervical corpectomy and fusion augmented with a spanning plate. All construct failures following three-level corpectomy occurred within 2 months after surgery and resulted from ventral graft displacement at the caudal vertebra. Three of these patients underwent revision surgery consisting of dorsal cervical fusion with lateral mass instrumentation. MacDonald et al. (8) noted early graft displacement of over 2 mm in approximately 11% of patients undergoing corpectomy of two or more levels, with most of these patients requiring revision surgery. These authors also noted an increasing rate of graft complications with increased length of decompression and fusion.

The above data suggest strongly that the incidence of graft migration is directly associated with increasing length of the graft and the number of levels involved in the surgery. Single-level corpectomies have the lowest incidence of graft migration, and the incidence increases with each
additional level. In Wang et al.’s (12) series, this occurred despite the use of postoperative immobilization in halo vests for four-level procedures, as compared with twoposter braces for one-, two-, and three-level surgeries. Two patients had graft migration identified within 4 days during the hospital stay. Both of these patients had an episode of emesis thought to have contributed to the complication due to increased stress on the graft.

In addition to graft length, the caudal vertebral level of the fusion appears to have an effect on graft stability. Of the 16 patients reported by MacDonald et al. (8) with graft migration, 14 involved C6 as the caudal level of corpectomy, with the fusion extending to the C7 vertebral body. The remaining two patients had single-level corpectomies ending at C6 and a history of emesis in the postoperative period thought to have resulted in movement of the graft. In Wang et al.’s (12) series, two-level corpectomies extending to C7 experienced a higher rate of migration than three-, four-, and five-level ventral decompressions that did not extend to C7. Additionally, no long fusion (two levels or more) had a problem with graft migration when it extended caudally only to C6.

The association of a fusion extending caudally to C7 with graft displacement may be related to the cervical lordosis of the C7 body associated with the sagittal inclination at the cervicothoracic junction. This sharp angular change possibly results in increased stress at the graft-end plate interface, leading to the observed higher probability of graft extrusion. Fusions that extend caudally to C7 should be performed carefully to ensure that the graft is seated. Care should be taken to preserve as much of the ventral cortex of the lower vertebral body as possible to resist fracture and allow for a strong inferior anchor. However, even meticulous surgical technique with ventral stabilization or postoperative halo immobilization is often insufficient to prevent this complication. Given this, many surgeons recommend the addition of dorsal cervical fusion and instrumentation for these patients.