Graft subsidence after instrument-assisted anterior cervical fusion

Abstract

<jats:p content-type="fine-print"><jats:italic>Object.</jats:italic> Bone grafts used in anterior cervical fusion (ACF) may subside postoperatively. The authors reviewed a recent series in which instrument-assisted ACF was performed to determine the degree of subsidence with respect to fusion length, use of segmental screws, and patient smoking status, age, and sex.</jats:p> <jats:p content-type="fine-print"><jats:italic>Methods.</jats:italic> Charts and implant records were reviewed for all 70 patients who underwent instrument-assisted ACF during a 2-year period. The procedures, grafting materials, plate types/lengths, and patient smoking status were recorded. The immediate postoperative and follow-up lateral radiographs were analyzed. The plate lengths and lengths of the fused segments were measured in a standardized fashion.</jats:p> <jats:p content-type="fine-print">The mean intraoperative and follow-up fusion segment lengths were 54.3 and 51.9 mm, respectively. Greater subsidence occurred in multilevel fusions than in single-level fusions. There were noticeable changes in the position of plates or screws on 14 of 70 follow-up x-ray films. No new neurological deficits related to graft subsidence occurred, and the reoperation rate was 3%. There was no statistical relation between subsidence and the following variables: segmental fixation, smoking status, sex, age, or dowel size when corrected for length of the plate. Hardware migration correlated significantly with plate length in cases of two- and three-level fusions.</jats:p> <jats:p content-type="fine-print"><jats:italic>Conclusions.</jats:italic> The length of a fusion segment decreases in the immediate weeks following instrument-assisted ACF. Construct length is the most important determinant of subsidence. When designing multilevel cervical constructs, consideration of the effects of graft subsidence may help to avoid hardware-related complications.</jats:p>

New Technical Tip for Anterior Cervical Plating : Make Hole First and Choose the Proper Plate Size Later

“…Goffin et al 7) found late degenerative changes at disc levels adjacent to fused regions in 15 of 25 patients with fractures and/or dislocations of the cervical spine, and recommended the use of the shortest plate possible to avoid extending the plate into adjacent discs. Tye et al 18) suggested that the risk of developing adjacent level ossification is increased in the setting of plate placement within 5 mm of an adjacent unfused disc space and another study also reported that a PDD of at least 5 mm from adjacent disc spaces reduces the likelihood of moderate-to-severe adjacent-level ossification, and that the risk of adjacent-level ossification is higher at cephalad adjacent levels than caudal adjacent levels 13) . As mentioned above, there is a general consensus that use of the shortest plate and the longest PDD possibly reduces the likelihood of developing postoperative degenerative changes, including adjacent level ossification, after ACDF.…”

Anterior cervical stabilization using a semi-constrained cervical plate and titanium mesh cage for single level corpectomy

“…However, Tye et al compared 12-mm and 14-mm bone dowels and found that the use of a larger dowel does not reduce the rate of subsidence. 23 Benzel also emphasized the importance of graft location in anterior cervical reconstruction. 22 He concluded that interbody bone grafts should be placed within or slightly ventral to the neutral axis region, particularly if dorsal stability is inadequate, and that a more ventral location might be optimal if the dorsal stability is adequate.…”

“…15 Tye et al suggested that the placement of screws immediately above and below the graft at the top and bottom of the construct might help minimize the hardware complications resulting from graft subsidence. 23 Some authors recommend ensuring sufficient packing of Table 5 Reports of cervical corpectomy and reconstruction with a titanium mesh cage and variable anterior cervical plate manufacturers of the plate and screw construct used are given the bone in the TMC. The volume of autograft harvestable from a single level corpectomy defect might be not sufficient to allow firm overpacking of the cage.…”

“…7,20,21 Furthermore, given their small footprint and sharp edges, TMCs are susceptible to fatigue failure and subsidence, [16][17][18][19] and the surface area and position have been suggested to influence load transmission and cage settling into the vertebrae. 22, 23 We studied the outcomes of semi-constrained anterior cervical fusion with TMCs and a local autograft after a cervical corpectomy, and quantified the clinical effects of using cages of two sizes in anterior cervical reconstruction.…”

Comparative Biomechanical Study of Cervical Spine Stabilisation by Cage Alone, Cage with Plate, or Plate-Cage: A Porcine Model

“…[38][39][40][41][42] Excessive subsidence can cause adverse effects, such as segmental kyphotisation, foraminal stenosis with recurrent radiculopathy, 43 and neck pain. In our study, the greatest subsidence was noted with cage-alone stabilisation; additional plating significantly decreased the extent of subsidence.…”