• Multicenter retrospective cohort study comparing the results of unilateral laminotomy for bilateral decompression versus posterior decompression with instrumented fusion for low-grade degenerative spondylolisthesis with lumbar spinal stenosis.

Patients diagnosed with  degenerative spondylolisthesis patients (DS) and symptomatic lumbar spinal stenosis (LSS) have had standard surgical recommendations of fusion in combination with decompression since the 1990’s.   Since the early 1990’s, surgical techniques have become less invasive.  What traditionally required wide pedicle to pedicle wide laminectomies with partial facetectomies for central stenosis can now be achieved with unilateral laminotomy with bilateral decompression (ULBD).  This technique spares more of the facet joints, the dorsal ligamentous complex, the mid portion of the neural arch and preserves the muscular and ligamentous attachments to the contralateral side.  Because of the preservation of some of the stabilizers of the spine,  more surgeons have been performing this surgical technique instead of the more traditional midline decompression and fusion.

This is a retrospective cohort study reviewing EMR Database from five Kaiser Permanente Northern California centers from January 1, 2007 to December 31, 2011.   An Exclusion criteria was established.  The charts were reviewed to identify Surgical patients who had the specific ULBD procedure for DS and LSS.  A total of 164 patients were identified.

During that period,  3457 patients with DS and LSS who underwent Fusion were identified, using the same exclusion criteria.   A propensity score matching system was established.  Because of the smaller number of ULBD patients,  it was decided to identify at least three Fusion cases foe each ULBD case.  The matching methods considered age, sex,  race,  and smoking status.   437 confirmed cases were included in the fusion cohort versus the 164 cases in the ULBD.   The Charlson comorbidity index for each patient ( index using a weighted score based on the diagnoses for 17 serious health conditions in the year before cohort entry) was also reviewed to establish a propensity match between the two cohorts.  There was no significant differences in the age,  sex ethnicity, smoking,  BMI or Charlson comorbidity index.

RESULTS:

ULBD had decreased mean length of hospital stay  (2.3 vs 4.6 days).

ULBD had less blood loss (82 ml vs 445 ml)

ULBD had a lower 5 year reoperation rate  (10.4% vs 17.2%)

ULBD had a higher return to the ER within 90 days (12.2% vs 5%)

There was no difference in the postoperative complications or 90 day reoperation rates.

Long term,  the ULBD were more likely to have a reoperation at the index level.  The Fusion group were more likely to have a reoperation at an adjacent level.

The study outcomes were based on reoperation rates and not necessarily on clinical outcomes.

The authors acknowledge the limitations of the study including the retrospective nature,  the potential for selection bias based on unknown radiographic studies such as pre-operative instability x-rays, the exclusion of patients who had expired before the 5 year followup period,  the lack of uniformity of the fusion techniques,  and lack of accounting for the presence of pre-existing adjacent level degeneration.

The study explores the issue of whether surgical techniques may contribute to the development of instabilities associated with DS.  Certainly,  with current surgical preferences,   more surgeons are using minimally invasive and structure sparing approaches.   With these techniques,  we may start seeing less utilization of lumbar fusion for a certain subset of patients with DS and LSS.    A future prospective study may help answer this issue.  Certainly,  many issues of cost,  future disability,  and satisfaction might be addressed with the results of such as study.