Comparison of instrumented posterolateral fusion versus percutaneous pedicle screw fixation combined with anterior lumbar interbody fusion in elderly patients with L5–S1 isthmic spondylolisthesis and foraminal stenosis
Authors: Shim Jung Hyun , Kim Wan Soo , Kim Joo Hyung , Kim Dong Hyun , Hwang Jang Hoe , Park Choon Keun 
Published: May 2011

Object
The purpose of this study was to compare the clinical and radiological outcomes of treating L5–S1 isthmic spondylolisthesis and foraminal stenosis in elderly patients with instrumented posterolateral fusion (PLF) versus percutaneous pedicle screw fixation (PSF) combined with anterior lumbar interbody fusion (ALIF).

Methods
Forty-nine patients older than 65 years of age with L5–S1 isthmic spondylolisthesis and symptomatic foraminal stenosis who underwent ALIF were retrospectively analyzed. An ALIF with instrumented PLF (Group A) was performed in 23 patients, and ALIF with percutaneous PSF (Group B) was performed in 26 patients. Data were collected preoperatively and at 3 months, 6 months, 1 year, and every subsequent year. A comparative analysis was made between the 2 groups using clinical (visual analog pain scale [VAS] and modified MacNab criteria) and radiological (dynamic plain radiographs and CT scans) measures.

Results
The mean follow-up duration was 30.3 months (range 24–47 months). The mean preoperative scores on the VAS for low-back pain in Groups A and B were 5.9 and 5.7, respectively, decreasing to 1.4 and 3.6, respectively, at 6 months after surgery (p = 0.001), whereas VAS scores for low-back pain in Groups A and B at 2 years postoperatively were 1.3 and 2.3, respectively (p = 0.005). The mean preoperative scores on the VAS for leg pain in Groups A and B were 7.5 and 7.8, respectively, decreasing at 6 months after surgery to 1.2 and 1.6, respectively (p = 0.201), whereas VAS scores for leg pain in Groups A and B at 2 years postoperatively were 1.3 and 1.4, respectively (p = 0.803). The rates of patients with excellent or good outcomes in terms of the modified MacNab criteria in Groups A and B were 91.3% and 69.2%, respectively, at 6 months after surgery (p = 0.010). Those rates in Groups A and B at 2 years after the operation were 91.3% and 84.6%, respectively (p = 0.203). The fusion rates in Groups A and B were 91.3% and 57.7%, respectively, at 6 months after surgery (p = 0.008), whereas the fusion rates in Groups A and B were 91.3% and 76.9%, respectively, at 2 years after surgery (p = 0.103). There was no significant difference in terms of the complication rate between Group A (4.3%) and B (3.8%) (p = 0.691).

Conclusions
A relatively longer time until, and lower rate for, fusion in the patients treated with ALIF and percutaneous PSF were noted, which may be correlated with a relatively lower rate of patients with excellent or good outcomes. These results seem to favor ALIF with instrumented PLF rather than ALIF with percutaneous PSF in the treatment of elderly patients with L5–S1 isthmic spondylolisthesis and foraminal stenosis. However, additional long-term follow-up, a larger number of patients, and well-designed studies are necessary for a more rigorous evaluation of the outcome of patients treated using these surgical techniques.