Development and Initial Internal Validation of a Novel Classification System for Perioperative Expectations Following Minimally Invasive Degenerative Lumbar Spine Surgery.

STUDY DESIGN This was a prospective consecutive clinical cohort study. OBJECTIVE The purpose of our study was to develop and provide an initial internal validation of a novel classification system that can help surgeons and patients better understand their postoperative course following the particular minimally invasive surgery (MIS) and approach that is utilized. SUMMARY OF BACKGROUND DATA Surgeons and patients are often attracted to the option of minimally invasive spine surgery because of the perceived improvement in recovery time and postsurgical pain. A classification system based on the impact of the surgery and surgical approach(es) on postoperative recovery can be particularly helpful. METHODS Six hundred thirty-one patients who underwent MIS lumbar/thoracolumbar surgery for degenerative conditions of the spine were included. Perioperative outcomes-operative time, estimated blood loss, postsurgical length of stay (LOS), 90-day complications, postoperative day zero narcotic requirement [in Morphine Milligram Equivalent (MME)], and need for intravenous patient-controlled analgesia (IV PCA). RESULTS Postoperative LOS and postoperative narcotic use were deemed most clinically relevant, thus selected as primary outcomes. Type of surgery was significantly associated with all outcomes (P<0.0001), except intraoperative complications. Number of levels for fusion was significantly associated with operative time, in-hospital complications, 24 hours oral MME, and the need for IV PCA and LOS (P<0.0001). Number of surgical approaches for lumbar fusion was significantly associated with operative time, 24 hours oral MME, need for IV PCA and LOS (P<0.001). Based on these parameters, the following classification system ("Qureshi-Louie classification" for MIS degenerative lumbar surgery) was devised: (1) Decompression-only; (2) Fusion-1 and 2 levels, 1 approach; (3) Fusion-1 level, 2 approaches; (4) Fusion-2 levels, 2 approaches; (5) Fusion-3+ levels, 2 approaches. CONCLUSIONS We present a novel classification system and initial internal validation to describe the perioperative expectations following various MIS surgeries in the degenerative lumbar spine. This initial description serves as the basis for ongoing external validation.