Ingenuous Ruler-Guided Technique to Achieve Accurate Angles in Z-Plasty Design: A Reliability and Feasibility Study

Abstract Accurate angle construction is fundamental to successful Z-plasty. Conventional tools such as protractors are often impractical in operative settings due to sterility issues, difficulty on curved surfaces, and workflow disruption. We developed a simple ruler-based technique using multiplication factors (0.25X, 0.5X, 0.7X, 0.9X, 1.0X) to construct standard angles without specialized instruments. The aim of the study is to validate a simplified ruler-guided multiplication-factor technique for constructing Z-plasty angles without angle-measuring instruments and to assess its accuracy, reliability, and clinical feasibility. This prospective two-phase observational study included (Phase 1: 50 tracings per angle) derivation and reproducibility testing of multiplication factors for standard Z-plasty angles by five surgeons and (Phase 2) clinical validation in 32 consecutive patients undergoing Z-plasty. Ruler-guided designs were compared with sterile protractor measurements. Primary outcomes were agreement assessed by intraclass correlation coefficient (ICC) and Bland–Altman analysis. Secondary outcomes included plotting time, surgeon-reported usability, and early postoperative complications. Multiplication factors demonstrated high reproducibility (SD ≤0.03) with minimal interobserver variability. Clinical validation showed excellent agreement between ruler-guided and protractor-based measurements (ICC 0.94; 95% CI 0.90–0.97). Bland–Altman analysis demonstrated a mean bias of 0.8° with limits of agreement from −3.1° to +4.7°. Plotting time was significantly shorter using the ruler-guided technique (22 ± 6 second vs. 65 ± 12 second p <0.001). Surgeon usability scores were high (mean 9.1/10). No complications attributable to planning error were observed. The simpler ruler-guided multiplication-factor technique provides clinically equivalent angular accuracy to protractor-based design while offering superior speed, ease of use, and applicability on curved surfaces. Its simplicity and universal availability make it a practical alternative for routine Z-plasty planning, particularly in high-volume and resource-limited settings.