266 - Initial Clinical Outcomes of an Interspinous Process Fixation System w...

#266 Initial Clinical Outcomes of an Interspinous Process Fixation System with Polyaxial Design

MIS Techniques and Outcomes

Poster Presented by: J.A. Sclafani


J.A. Sclafani (1)
K. Liang (1)
C. Gordon (2)

(1) Milestone Research Organization, San Diego, CA, United States
(2) Precision Spine Care, Tyler, TX, United States


Background: Early interspinous process fixation constructs utilize rigid fixation plates with immobile spikes which increase the difficulty of device implantation when anatomic variations are encountered. The PrimaLOK™ SP system has evolved from early interspinous process fixation devices to integrate multiple polyaxial features with the goal of accommodating natural osseous anatomic variations to achieve optimal implant placement and fixation integrity. Early cadaveric biomechanical studies of this plating system used as an adjunct to ALIF cage implantation have demonstrated significantly reduced flexion/extension/lateral bending and axial rotation range of motion compared to native segments under physiologic loads. The purpose of this study was to evaluate clinical outcome in patients treated with this device.

Methods: A retrospective, non-randomized, single-center chart review at or beyond the one year post-operative time point was conducted to collect pre-operative and peri-operative data. A post-operative numerical NRS and modified MacNab classification score were obtained from each patient in the cohort via phone survey. Statistical analyses were performed via one-way ANOVA or t-tests with significance defined as p< 0.05.

Results: A total of 53 patients (29 female, 24 male) with a mean age of 60 years were included in the study. The most common primary surgical indications were stenosis (45.3%), herniated disc (18.9%) and spondylolisthesis (11.3%). Median hospital stay was 2 days (range 1-7 days). There were no reported peri-operative blood transfusions or cases of radiographic fracture/migration of the device at the 6 week post-operative time point. Overall, there was a significant improvement in reported pain scores with a pre-operative average (7.17, n=53), and post-operative average (4.7, n=50, p=0.0001, 22 months average follow up). According to the modified MacNab criteria, satisfactory (excellent or good) results were obtained in 48% of all patients. A significant improvement in pain score was reported when the primary diagnosis was stenosis (2.65 points, p=0.0001) or spondylolisthesis (4.4 points, p=0.01). Patients with pre-operative pain scores greater than 8/10 reported more pain improvement (3.5 points, p< 0.0001, n=24) than patients with pre-operative pain scores less than 5 (0 points, p=0.96, n=8). Patients with a BMI less than 30 reported a 63% satisfactory MacNab score and significant pain improvement (3 points, p< 0.0001, n=30) while those with a BMI greater than 30 reported a 19% satisfactory Macnab score and significant pain improvement (1.8 points, p=0.02, n=16).

Conclusions: These results indicate that this interspinous fusion system produces significant clinical improvement when employed to treat patients with stenosis, herniated disc, or low grade spondylolisthesis. Patients with high pre-operative pain score and BMI under 30 can be predictors of better clinical outcome and should be considered prior to implantation. These early results appear promising, although further evaluation in a larger series of patients would be helpful in evaluating the outcome.