Introduction: Lumbar spinal stenosis is one of the most common causes of low back pain, particularly in older adults. Conventional treatment typically begins with conservative management, progressing to surgical options such as laminectomies and discectomies for patients who do not achieve adequate pain relief. In 2006, the minimally invasive lumbar decompression (mild®) procedure received FDA approval as an alternative procedure in an outpatient setting. This retrospective study evaluates the safety and efficacy of this procedure at a single institution.
Methods: Our study included all patients who underwent the mild® procedure across the Mayo Clinic enterprise from the procedure’s inception to October 2024. The primary outcomes of interest were complication and reoperation rates. Patient-reported outcome measures, including the Numeric Pain Rating Scale (NPRS), Patient-Reported Outcomes Measurement Information System (PROMIS 10), and Oswestry Disability Index (ODI), were assessed preoperatively, postoperatively, and at last follow-up.
Results: A total of 175 patients were identified, with 44.6% being female. The mean age at the time of the procedure was 76.3±8.7 years, and the most frequently treated site was L4-5 (53.7%). There was a significant decrease in NPRS (p=0.02) and ODI (p=0.002) following the procedure. Complications were observed in 14.9% of patients, with hematomas and bleeding being the most frequent (n=10), followed by uncontrolled pain (n=5), weakness (n=5), and numbness (n=4). The overall reoperation rate was 54.3% (n=95), with 25.1% (n=44) undergoing a surgical procedure. Among the 100 patients (57.0%) evaluated by neurologic or orthopedic surgery after their initial mild® procedure, 67 were considered surgical candidates, with 42 (62.7%) proceeding to surgical reoperation. The average time to surgical reoperation was 380.7±442.9 days. No significant differences were found in age, gender, NPRS, PROMIS 10, or ODI scores between surgical candidates who underwent surgical reoperation and those who did not.
Conclusion : Although patient-reported outcome measures suggest that pain improves after the mild® procedure, the high rate of reoperation highlights the need to consider long-term effectiveness of this procedure.
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