Optomechanical evaluation of knot security in Monocryl and Maxon sutures under varying pH conditions

Knot stability and security are crucial factors in surgical suture performance, ensuring optimal tension distribution and minimizing the risk of wound dehiscence. The mechanical behavior of surgical knots is influenced by suture material properties, knot configuration, and environmental factors such as localized pH deviations, which can accelerate material degradation. This study investigates the impact of pH-induced degradation on the mechanical and optomechanical performance of square and surgeon's knots tied with Maxon and Monocryl sutures under acidic (pH 5) and neutral (pH 7) conditions. Stress-strain analysis and Mach-Zehnder interferometry were employed to assess Young's modulus, mechanical loss percentages, tensile strength, toughness, phase maps, and 3D refractive index profiles over 20 d. Young's modulus results revealed significant reductions in acidic conditions. Maxon's surgeon knot decreased from 516 MPa to 228 MPa, while Monocryl's surgeon knot dropped from 434 MPa to 132 MPa over 20 d. Mechanical loss was notably higher in acidic conditions, with Maxon's surgeon knot exhibiting a 65.30% reduction and Monocryl's surgeon knot showing an 82.3% decrease. Toughness declined similarly, particularly in knotted configurations. Phase maps revealed substantial structural distortion, especially in Monocryl's perpendicular orientation at pH 5, indicating severe degradation. 3D refractive index profiles demonstrated that Maxon maintained greater internal uniformity, while Monocryl showed pronounced structural disruption under acidic conditions. Maxon's stability under different pH conditions makes it suitable for long-term applications, while Monocryl's rapid degradation suggests its suitability for scenarios requiring faster material breakdown. These findings provide valuable insights for suture selection in diverse wound conditions.