Urolithiasis is a common urological condition, particularly in the stone belt region. In recent years, percutaneous nephrolithotomy (PCNL) has become the standard treatment for large renal stones in the era of less invasive interventions. The modified lateral position with extended legs offers improved patient comfort, better respiratory mechanics, and enhanced surgical ergonomics. However, mastering this technique requires experience. This study evaluates the learning curve of a single urologist performing 70 consecutive cases, assessing improvements in surgical efficiency, precision, and complication rates over time.

This retrospective study analyzed 70 PCNL procedures performed in the modified lateral position with extended legs. All surgeries were conducted by a single urologist who had prior experience with conventional PCNL but was newly adopting this modified approach. Patients were divided into three chronological groups: Cases 1–25, Cases 26–50, and Cases 51–70. Key parameters, including operative time, fluoroscopy duration, number of needle punctures, stone-free rate, length of hospital stay, and complications, were recorded and compared. Cumulative summation (CUSUM) analysis was used to evaluate the surgeon’s learning progression and proficiency milestone.

Over time, the operative duration significantly decreased from a median of 65 minutes in the first 25 cases to 55 minutes in the later cases (p=0.049). The number of needle punctures required per procedure was reduced, with single-attempt punctures increasing from 40% to 75% (p=0.023). Fluoroscopy exposure also showed a decreasing trend (p=0.049). The overall stone-free rate improved from 92% to 100%, while complications such as bleeding and infection remained low and stable. CUSUM analysis indicated that proficiency was achieved after approximately 40 cases.

The learning curve for PCNL in the modified lateral position with extended legs demonstrates a significant improvement in surgical efficiency and precision after 40 cases. The refinement of technique over time results in shorter operative duration, reduced fluoroscopy exposure, and fewer needle punctures without compromising safety. These findings support the feasibility and benefits of this approach, encouraging wider adoption in urological practice.