Evolution of the Interspinous Process Device as a Safe and Effective Alternative for Posterior Instrumentation: Experience with Preferred Device in 198 Cases

Introduction: Interspinous process (ISP) devices have emerged as promising minimally invasive alternatives to traditional posterior instrumentation; however, the variety of iterations and limited distinctions in research have made it challenging to appropriately classify their safety and efficacy.
This study aims to evaluate clinical outcomes in patients who underwent lumbar decompression using an ISP device and compare to traditional pedicle screw fixation.

Methods: A retrospective review was conducted on patients who underwent posterior lumbar decompression using an interlaminar distraction ISP device featuring rigid, spiked locking-plate fixation with and without interbody fusion over a ten-year period. All cases were performed by a single neurosurgeon at a non-academic institution. Patients were followed for clinical outcomes up to one year. Outcome measures included visual analog scale (VAS) scores, complications, readmissions, reoperations, and length of stay. Institutional Review Board approval and patient consent was obtained.

Results: 198 patients (mean age 72; 41% male; mean BMI 26.6 kg/m2) underwent posterior lumbar fixation between March 2014 and August 2024 (one-level, n=158; two-level, n=37; three-level, n=3; total, n=246). Of the cases performed, 117 involved anterior or lateral lumbar interbody fusion, while 81 were done with posterior decompression alone. Average length of stay was one day. Mean preoperative, 2-week, 6-week, 3-month, 6-month, and 1-year VAS scores were 5.8, 3.5, 2.5, 2.1, 2.1, and 2.0, respectively. VAS scores improved significantly between each follow-up period until 3 months (p < 0.05). Four total complications were reported including one surgical site infection, one epidural hematoma, and two cases of subsidence. All four cases required readmission and reoperation. The ISP implant used was associated with a 2% complication rate and demonstrated favorable clinical outcomes compared to traditional posterior instrumentation methods such as pedicle screw placement which have reported complication rates ranging from 6% to 20.8%

Conclusion : While many versions of the ISP device exist, the implant used in this study offers a viable minimally invasive alternative to traditional posterior spinal instrumentation methods with significant pain reduction and lower complication rates. Further studies that differentiate various types of ISP implants would be valuable for accurately defining the safety and efficacy profiles of these devices.