Clinical Outcome of Partial Reduction And Interbody Fusion For High Grade L5–S1 Spondylolisthesis using the modified SRS Outcomes Instrument

Jason Smith. MD,
Vedat Deviren, MD,
Arash Emami, MD,
Frank Kleinstueck, MD,
David Bradford. MD
UCSF, San Francisco, CA, USA

INTRODUCTION:
In situ posterior interbody fusion with fibula allograft has improved the fusion rates for patients with high–grade spondylolisthesis. However, patients may be left with significant residual deformity. The use of this technique in conjunction with partial reduction has not been reported. We report the clinical and radiographic outcome of partial reduction followed by interbody fusion in a group of patients with high–grade slips, utilizing the Modified SRS Outcome Instrument.

MATERIALS AND METHODS:
Twelve consecutive patients have undergone partial reduction followed by posterior fibula interbody fusion for high–grade spondylolisthesis. Nine patients have had at least 24 month follow up, and are reported on here. Average age at the time of surgery was 27 years (range 8 to 51), and the average follow–up was 43 months (24 to 72). Pre–operatively eight patients had low back pain, seven patients had radiating leg pain, and five patients had hamstring tightness. The average Meyerding grade pre–operatively was 4.1 (range III–V). Charts and radiographs were reviewed, and outcome data were collected by the confidential use of the modified SRS outcomes instrument.

RESULTS:
According to the modified SRS Outcomes Instrument, all patients were either extremely or somewhat satisfied, average score 4.6 out of 5. The average mental health, function, self–image, and pain scores were respectively: 3.7, 3.6, 3.6, and 3.5 out of 5. The average grand total score was 74%. Two patients who had multiple previous surgeries had lower scores than the rest of the group. The slip angle, as measured from the superior endplate of L5, improved from 23 degrees (–5 to 42) pre–operatively to 7 degrees (–13 to 32) post–operatively. Two patients who were not initially instrumented suffered fractures of their interbody grafts. Both of these patients had repair of the pseudarthrosis with placement of pedicle screw instrumentation, with subsequent fusion. All patients ultimately achieved solid fusion. There were no permanent neurologic deficits caused by surgery. Two patients had transient EHL weakness.

CONCLUSIONS:
With average 43 months follow–up, all of our patients were either extremely satisfied or somewhat satisfied with the results of surgery. Revision surgery provides less reliable results. Without instrumentation the stress experienced by the structural graft after partial reduction risks fracture. According to the clinical and radiographic results of this study, we recommend partial reduction, posterior interbody fusion with pedicle screw instrumentation for patients with high–grade spondylolisthesis at L5–S1.