Decompression And Implantation Of An Interlaminar Stabilization Implant For The Minimally Invasive Treatment Of Lumbar Spinal Stenosis With Back Pain; Operative and Three Year Clinical and Radiographic Outcomes From a Level 1 US IDE Study

Presented at SMISS Annual Forum 2014
By Reginald Davis MD
With Hyun Bae MD, Thomas Errico MD, Carl Lauryssen MD, Scott Leary MD,

Disclosures: Reginald Davis MD None Hyun Bae MD A; Relievant., Thomas Errico MD None, Carl Lauryssen MD None, Scott Leary MD None,

Introduction:
Spine surgery has been evolving and trending towards greater utilization of minimally invasive surgery (MIS), with instrumentation and implants that provide less morbidity in the operative and immediately post-operative period, while providing similar or better long-term clinical outcomes.

Aims/Objectives:
This level 1 study compares outcomes from MIS for the treatment of lumbar spinal stenosis (LSS) using decompression and an interlaminar stabilization implant (ILS), to decompression with posterolateral fusion, pedicle screws and autologous bone graft.

Methods:
A prospective, randomized 2:1 trial comparing ILS (n=215) to fusion (n=107) was conducted at 21 sites under an FDA investigational device exemption. At inclusion, all patients had MRI-confirmed LSS at one or two contiguous levels between L1-L5 and VAS Back Score of ≥50mm. The primary outcome was composite clinical success (CCS) calculated at month 24; the current evaluation represents longer term follow-up.

Results:
Operative time was 98.0 minutes for ILS vs.153.2 minutes for fusion (p<0.0001). Estimated blood loss was 109.7 ml ILS vs. 348.6 ml fusion (p<0.0001). Hospital stay was 1.9 days ILS vs 3.19 fusion (p<0.0001). The 3 year CCS, defined as achieving ≥15 point improvement on ODI and freedom from reoperations and steroid injections, was 65.6% ILS vs 54.8% fusion (p=0.091). The reoperation/injection rate was 25% ILS vs. 24% fusion. Percentage experiencing ≥20 mm improvement on visual analog scale (VAS) back and worse leg pain were 83% ILS vs 80% fusion (p=0.7) for back pain, and 83% ILS vs 85% fusion (p=0.5) for worse leg pain. There was no significant implant-level change in range of motion in ILS cohort with mean change of -0.20 deg, p=0.15, while in the fusion cohort index-level motion was significantly reduced with mean change of -2.51 deg p<0.0001 and significant between group difference (p<0.0001). At the level above ILS, there was no significant change in motion with mean change of 0.33 deg (p=0.26). For fusion there was significant increase in motion above the implant level with mean increase of 1.55 deg p=0.005 and significant between group difference (p=0.027).

Conclusions:
At 3 years post-op, clinical outcomes show more ILS patients achieve composite clinical success than fusion patients. Radiographic analysis show adjacent level motion remains at preoperative levels in the ILS cohort vs. significantly elevated in the fusion cohort. This longer- term data suggests that MIS using decompression with an interlaminar stabilization implant provides outcomes that are increasingly favorable compared to fusion for treatment of moderate to severe LSS.