Transvertebral Transsacral strut grafting for high-grade isthmic spondylolisthesis L5-S1 with fibular allograft.

STUDY DESIGN

A clinical retrospective study was conducted.

OBJECTIVE

To evaluate the clinical and radiographic outcomes of 25 consecutive patients with symptomatic high-grade isthmic spondylolisthesis at L5-S1 treated by decompression and transvertebral, transsacral strut grafting with fibular allograft.

SUMMARY OF BACKGROUND DATA

Symptomatic high-grade isthmic spondylolisthesis serves as a challenging clinical problem. Traditional treatment by in situ posterolateral arthrodesis has been associated with pseudarthrosis rates up to 50%. Even with successful posterolateral fusion, the graft is in an unfavorable biomechanical environment, owing to it being under tension, which can allow for progression of lumbosacral kyphosis (slip angle) and sagittal translation (slip). Open reduction of spondylolisthesis improves the biomechanical situation by allowing a trapezoidal interbody graft at L5-S1, but is associated with neurologic deficits in up to 30% of patients. The technique used in this particular study achieves the biomechanical goal of a structural interbody construct without the necessity of anatomically reducing the translational slip. The fibular strut grafts were placed through an anterior approach as part of an anterior/posterior procedure, or via a posterior approach as part of a posterior-only procedure.

METHODS

A consecutive series of 25 symptomatic patients with high-grade isthmic spondylolisthesis at L5-S1 had an average age of 29.8 years. Six patients were 16 years or younger. Eight patients underwent a posterior-only approach with posterior transosseous fibular strut grafting across S1 into the L5 vertebral body combined with posterolateral arthrodesis L4-S1 using a pedicle screw-rod construct. Seventeen patients underwent a combined anterior/posterior approach with transosseous fibular allograft strut grafting at L5-S1 and L4-L5 interbody arthrodesis using a femoral ring allograft supplemented with L4-S1 posterior pedicle screw-rod instrumentation. No reduction attempts were performed, other than those occurring spontaneously by patient positioning and decompression. Patients were evaluated for clinical improvement and radiographically. Clinical outcomes were measured with the scoliosis research society outcome instrument. Radiographs were followed for arthrodesis, translation, and slip angle. Mean follow-up was 39 months (range, 30 to 71 mo). All patients preoperatively had a grade III to V slip using the Meyerding classification (mean 3.7). The slip angle averaged 37 degrees.

RESULTS

The postoperative mean slip grade was 3.5 compared with 3.7 preoperatively (no significant difference). The mean slip angle improved to 27 degrees (8 to 40 degrees) postoperatively from 37 degrees (13 to 51 degrees) preoperatively (P<0.05). All patients went on to a stable arthrodesis, with no progression in slip or slip angle. There were no permanent neurologic deficits among any of the subjects, and all patients demonstrated improvement in their preoperative gait disturbance. Scoliosis research society functional outcome score showed 24/25 extremely satisfied or somewhat satisfied at latest follow-up.

CONCLUSIONS

Treatment by this method showed improvement in lumbosacral kyphosis while avoiding the neurologic injury risk associated with open slip-reduction maneuvers. Despite no reduction in translational deformity, this technique offers excellent fusion results, good clinical outcomes, and prevents further sagittal translation and lumbosacral kyphosis progression.