A Multimodal Measurement System for Quantifying Time-Dependent Suture Tension Relaxation and Wound Closure Strength

Postoperative wound stability in microsurgical suturing depends on time-dependent deformation of sutures and tissues. This study develops a multimodal suturing mechanics measurement system (MSMMS) to evaluate real-time suture tension and wound closure strength, defined as the extra stress needed to initiate wound reopening.

The MSMMS integrates micro-force suture tension sensing, global load and displacement measurement, and full-field digital image correlation (DIC). Sutured silicone specimens with pre-cut wounds were used as controlled surrogates. Stress relaxation was tested under uniaxial and sutured conditions, and relaxation parameters were extracted using a dual Maxwell model. Synchronized mechanical and DIC data identified crack initiation and wound closure strength.

The MSMMS captured two-phase relaxation in both sutures and silicone. Under the same initial stress, the sutured configuration produced about 20% greater suture relaxation than uniaxial loading. Wound closure strength showed a non-monotonic dependence on relaxation time: it decreased by 5-10% after short relaxation and partially recovered at longer times. Increasing the initial suture tension from 0.3 to 0.5 N increased wound closure strength by less than 5%.

Unlike conventional force-only or endpoint tests, the MSMMS enables synchronized characterization of suture tension, global loading, and wound closure strength. This framework provides a quantitative basis for optimizing surgical tension and evaluating smart suturing devices. The characterization of relaxation time constants may also help identify the optimal postoperative time window for suture adjustment.