Radiographic predictors of delayed instability following decompression without fusion for degenerative grade I lumbar spondylolisthesis.
OBJECTIVE
It is not known whether adding fusion to lumbar decompression is necessary for all patients undergoing surgery for degenerative lumbar spondylolisthesis with symptomatic stenosis. Determining specific radiographic traits that might predict delayed instability following decompression surgery might guide clinical decision making regarding the utility of up-front fusion in patients with degenerative Grade I spondylolisthesis.


METHODS
Patients with Grade I degenerative lumbar spondylolisthesis (3-14 mm) with symptomatic stenosis were prospectively enrolled from a single site between May 2002 and September 2009 and treated with decompressive laminectomy without fusion. Patients with mechanical back pain or with gross motion (> 3 mm) on flexion-extension lumbar radiographs were excluded. The baseline radiographic variables measured included amount of slippage, disc height, facet angle, motion at spondylolisthesis (flexion-extension), and sagittal rotation angle. Data were analyzed using multivariate forward selection stepwise logistic regression, chi-square tests, Student t-test, and ANOVA.


RESULTS
Forty patients were enrolled and treated with laminectomy without fusion, and all patients had complete radiographic data sets that were available for analysis. Reoperation was performed in 15 (37.5%) of 40 patients, with a mean follow-up duration of 3.6 years. Reoperation was performed for pain caused by instability at the index level in all 15 cases. Using multivariate stepwise logistic regression with a threshold p value of 0.35, motion at spondylolisthesis, disc height, and facet angle were predictors of reoperation following surgery. Facet angle > 50° was associated with a 39% rate of reoperation, disc height > 6.5 mm was associated with a 45% rate of reoperation, and motion at spondylolisthesis > 1.25 mm was associated with a 54% rate of reoperation. Patients with all 3 risk factors for instability had a 75% rate of reoperation, whereas patients with no risk factors for instability had a 0% rate of reoperation (p = 0.14).


CONCLUSIONS
Patients with motion at spondylolisthesis > 1.25 mm, disc height > 6.5 mm, and facet angle > 50° are more likely to experience instability following decompression surgery for Grade I lumbar spondylolisthesis. Identification of key risk factors for instability might improve patient selection for decompression without fusion surgery.
Harvard University, Cambridge, USA.
Claire
C
Blumenthal
Jill
J
Curran
Edward C
EC
Benzel
Rachel
R
Potter
Subu N
SN
Magge
J Frederick
JF
Harrington
Jean-Valery
JV
Coumans
Zoher
Z
Ghogawala
D000368:Aged; D019299:Decompression, Surgical / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000473:pathology / Q000601:surgery*; D007593:Joint Instability / Q000503:physiopathology; D007796:Laminectomy / Q000009:adverse effects / Q000379:methods*; D008159:Lumbar Vertebrae / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012086:Reoperation / Q000379:methods; D012720:Severity of Illness Index; D013123:Spinal Fusion / Q000706:statistics & numerical data; D013130:Spinal Stenosis / Q000473:pathology / Q000601:surgery*; D013168:Spondylolisthesis / Q000175:diagnosis / Q000473:pathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome