Introduction:

The optimal surgical treatment for patients with degenerative spondylolisthesis and stenosis is controversial.  Surgical alternatives for these patients involve a decompression alone, or one performed concomitantly with a lumbar fusion.  The aim of this study was to carefully follow patients with degenerative spondylolisthesis undergoing bilateral decompression alone to determine the reoperation rate, demographic predictors of this, and the change in mobility profiles of the involved segments over the period of followup after the index surgery.

Methods:

Patients with degenerative spondylolisthesis undergoing bilateral decompression alone from a university spine practice involving 3 different surgeons were recruited to enroll in the study.  Most patients (80.4%) were treated with a midline-sparing unilateral approach for a bilateral decompression.  Flexion/extension films, preoperative MRI or CT scans, and preoperative demographic and patient reported outcome measures (PROMs) including the Oswestry Disability Index (ODI) and NPRS leg and back pain.  Postoperative clinical follow up was obtained at (3 months, 6 months, 1 year, and 2 years, and then yearly if possible) including PA and flexion/extension lateral lumbar films.  Postoperative MRI scans were obtained as clinically indicated for recurrent or new symptoms.  The university IRB approved the study.  Changes in radiographic and PROM outcomes with time were assessed with repeated measures GEEs.  We tested relationships between reoperation and previously suggested thresholds of 1.25mm translation, 6.5 mm disc height, and 50° facet joint angulation (Blumenthal et al. 2013) via Fisher’s exact tests.

Results:

The final cohort included 46 patients (52.2% female, 69.7±9.3 years).  The range of dynamic translation was a 2 mm and angular motion was a mean of 7° on flexion/extension films preoperatively.   Average disc heights on MRI were 8.6 (95% CI: 7.8, 9.4) mm and Facet joint angulation was a median of 45.0 (IQR: 45.0, 54.0) degrees.  In the postoperative period, Flexion increased by 1.0 (0.4, 1.6) degrees (p = 0.011).  Patients improved after surgery with a median ODI of 32.5 (20.0, 42.0) preop decreasing to a median of 10.0 (4.0, 18.0) 2 years postop (p < 0.001).  28.3% of patients had a reoperation, and 19.6% had a reoperation at the same level during the course of followup, which was a median of 28.1 months (range 6 – 51 months). Preoperative translation greater than 1.25 mm (Blumenthal et al. 2013) was associated with reoperation, with no patients under this threshold having reoperation, while 39.4% of patients over this threshold had a reoperation (p = 0.009).  No other cutoffs or radiographic parameters were significantly associated with reoperation.  Patients with higher back and leg pain preop were more likely to have a reoperation at the same level (p = 0.043, 0.013, respectively).

Discussion:

In this patient group of 46 people treated with decompression alone for stenosis in the setting of degenerative spondylolisthesis, we found a rate of reoperation of 28.3% with a median follow up of over 2 years postop, and found that reoperation was higher in patients with more than 1.25 mm of dynamic translation, as well as in patients with higher preoperative back and leg pain.