Higher American Society of Anesthesiologists Classification Does Not Limit Safety or Improvement Following Minimally Invasive Transforaminal Lumbar Interbody Fusion

OBJECTIVE: The American Society of Anesthesiologists (ASA) physical status classification has been used to risk stratify surgical candidates. Our study compares outcomes of minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) procedures based on preoperative ASA physical status classification. METHODS: A surgical registry was reviewed for primary, single-level MIS TLIF patients. Patients were categorized by preoperative ASA physical status classification: ASA I, ASA II, ASA III+. Perioperative complications were compared among groups. Patient-reported outcome measures (PROMs) for back pain, leg pain, physical function, and disability were recorded preoperatively and at 6-week, 12-week, 6-month, 1-year, and 2-year postoperative timepoints. PROM improvement from baseline (ΔPROM) and minimum clinically important difference (MCID) achievement was calculated for each timepoint and compared among groups. MCID achievement was determined as ΔPROMs that surpassed previously established MCID values. RESULTS: Of the 487 patients, 64 had an ASA classification of I, whereas 336 had an ASA of II, and 87 had an ASA of III or greater. Rates of complications were not associated with ASA classification (all p>0.050). Neither mean PROM scores nor ΔPROM scores were significantly associated with ASA classification at any timepoint (all p>0.050). MCID achievement was significantly associated with ASA classification for back pain at 1 year only (p=0.041). Overall MCID achievement was not significantly associated with ASA classification for any PROM (p>0.050). CONCLUSION: While ASA classification has been commonly used to risk stratify surgical candidates for spinal procedures, patients with an ASA of III or greater may be able to achieve similar long-term outcomes following MIS TLIF given proper selection criteria.