Transvertebral Trans-sacral Strut Grafting for High-Grade Isthmic Spondylolisthesis

Summary: 23 patients with symptomatic high-grade isthmic spondylolisthesis treated by decompresssion and trans-vertebral, trans-sacral strut grafting, either anterior/posterior approach, or pure posterior approach. Translational reduction methods were not performed, but attempt was made to improve slip angle, which was significantally imporved post-operatively in these patients. No cases of neurologic decline, slip or slip angle progression, obvious pseudoarthrosis, or instrumentation failure associated with this treatment method. SRS outcomes measures showed 22/23 patients extremely or somewhat satisfied at latest follow-up.

Symptomatic high-grade isthmic spondylolisthesis presents a challenging clinical problem. Traditional treatment by in situ posterolateral arthrodesis has been associated with pseudoarthrosis rates up to 50%. Even with successful posterolateral fusion, the graft is in unfavourable biomechanical environment (tension), and can still allow progression of lumbosacral kyphosis (slip angle) and sagittal translation (slip). Open reduction of spondylolisthesis theoretically improves biomechanical situation, but is difficult and can be associated with neurologic deficits in up to 30%. The purpose of this study was to review results of treatment of high-grade spondylolisthesis by decompression and trans-vertebral, trans-sacral strut grafting.

Methods: Consecutive series of 23 sympotmatic pts. Avg age 29.8 yr, six pts 16yrs or younger. 7 pts underwent posterior-only approach, with posterior transosseous fibular strut grafting across S1 into L5, with instrumented posterolateral arthrodesis L4-S1. 16 pts underwent combined anterior/posterior approach with transosseous strut grafting and L4/L5 interbody arthrodesis with subsequent posterior instrumentation L4-S1. No attempt at reduction, other than pt positioning, was attempted. Pts evaluated for clinical improvement, radiographs followed for arthrodesis, and changes in translation or slip angle. Clinical outcomes measured with the SRS outcome instrument.

Results: Avg F/U 38 months (range 26-60). Avg preop slip 3.7 (range 3-5), Avg postop slip 3.5. Avg preop slip angle 37 (13-51), improved postop to 27 (8-40) (P<0 .05). All went on to apparently stable arthrodesis, with no progression in slip or angle. pts demonstrated improvement preoperative neurologic deficits and gait disturbance. SRS outcomes showed 22/23 extremely satisfied somewhat satisfied. There were permanent pseudoarthroses.

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