Outcomes After 1- or 2-level MI-Decompression for Patients with High 5-Item Modified Frailty Index

Introduction: As the aging population increases demand for procedures addressing lumbar spine degeneration, risk stratification tools, such as frailty indices, have risen as patient-specific prognostic indicators for postoperative morbidity and mortality. The 5-factor modified frailty index (mFI-5) quantifies frailty, defined as the age-associated decline in functionality or recovery ability following a significant stressor. However, no studies have yet evaluated the utility of frailty in predicting outcomes after minimally invasive decompression (MI-Decompression) for patients with degenerative lumbar pathologies.

Methods: This retrospective study included patients who underwent primary 1- or 2-level MI-Decompression for treatment of degenerative lumbar spine conditions. mFI-5 was calculated using functional status and comorbidities, including hypertension, diabetes, chronic obstructive pulmonary disease, and congestive heart failure. Patients were stratified into three groups: non-frail (mFI-5=0), moderately frail (mFI-5=1), and severely frail (mFI-5≥2). Outcome measures included surgical details, complications, return to activity, and patient outcome measures—Oswestry Disability Index (ODI), Visual Analog Scale (VAS) back and leg pain, and Short Form 12-item Physical Component Score (SF12-PCS)— at preop and > 6 months postop.

Results: A total of 956 patients were included, 438 non-frail, 418 moderately frail, and 100 severely frail. Frail patients (mFI-5>1) were older (p < 0.001), had greater BMI (p=0.047), elevated CCI (p < 0.001), and greater percentages of ASA class > 3 (p < 0.001). Higher severities of frailty were associated with longer operative times (p < 0.001) and lengths of stay (p < 0.001), while blood loss was similar. Frail patients demonstrated worse preoperative symptoms, including ODI (p=0.019), VAS-back pain (p=0.019), and SF12-PCS (p=0.015), which continued postoperatively, including ODI (p=0.014) and SF12-PCS (p < 0.001). The magnitude of improvement between outcome metrics was comparable at ≥6-month follow-up. Return to activities, including driving, working, and stopping narcotics use, as well as all complication categories, including intraoperative, in-hospital, and postoperative, were similar across all patients.

Conclusion : MI-decompression provides comparable symptom relief and postoperative recovery, even among patients with significant frailty that may limit their ability to withstand the stresses of spine surgery. Further research is needed to delineate the relationship between frailty and outcomes in open versus minimally invasive spine procedures, especially as surgical techniques evolve and patient indications expand.