[Radiographic study of Coflex interspinous device for lumbar spinal stenosis]

To assess the radiography change of lumbar spinal stenosis (LSS) treated with the implantation of Coflex interspinous device retrospectively.

Sixty patients (34 male and 26 female) with LSS who underwent the decompression and Coflex device implanted surgery from January 2010 to December 2013 were followed up. The mean age of the patients was 59.4 years. There were 33 cases underwent Coflex surgery and 27 cases underwent Topping-off surgery. The Coflex segment ranged from L1/2 to L4/5 (L1-2: 1, L2-3: 5, L3-4: 19, L4-5: 35). The foraminal height, foraminal width and intervertebral space height change of the Coflex segment as well as its adjacent segment were recorded pre-/post-operatively and at last follow-up.Meanwhile, the Oswestry Disability Index(ODI) and Visual Analog Scale(VAS) were measured in all patient pre-/post-operatively and at last follow-up. The measurement data was recorded asx±s. And the independent and paired samples t-test was used to conduct the statistical analysis.

The foraminal height(FH) increased from (19.82±2.38) mm to (22.28±2.95) mm (P<0.05) post-operatively, and the FH decreased to (19.31±3.32) mm at the last follow up(P>0.05, compared to the post-operation). The average foraminal width(FW) was 11.2 mm, 11.58 mm and 11.12 mm at pre-/post-operation and follow up, which had no significant different change(P>0.05). The post-operative intervertebral space height (ISH) increased from (7.84±1.56) mm to (10.05±2.39) mm(P<0.05), and the ISH decreased to (7.91±1.77) mm at the last follow up(P>0.05, compared to the post-operation). The amount of the decreased FH and ISH had no significant difference when comparing the Coflex segment with its adjacent (Coflex±1) segments (P>0.05). The lumbar lordosis(LL) was 43.13°±15.93°, 38.41°±10.82° and 43.10°±13.21° at pre-/post-operation and follow up, there was no significant difference between pre- and post-operation(P>0.05). All patients showed statistically significant improvement(P<0.05) in the clinical outcome assessed in the VAS and ODI at the time of follow up compared to the pre-operation. The ODI score decreased from 65.12±13.56 to 9.89±1.77; the VAS score decreased from 8.02±1.81 to 1.66±0.51.

Coflex device could temporarily improve the FH and ISH after operation. However, it could not maintain the improvement as the follow-up time extended. The surgical decompression is the responsible factor for the good clinical outcome but not the improvement of FH.