Clamp fixation to prevent unfolding of a suture knot decreases tensile strength of polypropylene sutures

Purpose Although sutures evolved in last decade and the product spectrum broadened largely, they can be still classified into two: monofilament and multifilament. Sutures are the mainstay of orthopedic procedures like fascial closures, tendon repairs or tenodesis. In every repair, a suture loop is created. This suture loop is prone to failure due to suture elongation, knot slip and suture breakage. As the knot is the stress riser in a suture loop, the majority of acute loop failure occurs just adjacent to the knot. Monofilament sutures have higher bending stiffness and tendency to untie than multifilament sutures. The first throw of monofilament sutures have tendency to untie, which decrease loop tension and result in loss of achieved tissue approximation. Methods Although a common practice is to fix the first throw via a clamp before the locking one is tied, it can be hypothesized that a potential deforming effect can lead to a decrease in ultimate failure load of a monofilament suture loop. Results Fixing the first throw significantly reduced the ultimate failure load of monofilament nonabsorbable polypropylene sutures (Prolene) (62.2 ± 8 N vs. 72.7 ± 9 N, p = 0.019). The ultimate failure load achieved by monofilament sutures Polyglyconate (Maxon) and Nylon (Ethilon) and braided absorbable Polyglactin (Vicryl) were not affected by fixing the first throw. Conclusion Under microscopic examination, polypropylene sutures were found to be deformed by clamp fixation, while the others were not. Polypropylene sutures can be easily damaged when it is fixed by a clamp during knot tying. Presented data demonstrated that in real surgical situations clamp fixation of polypropylene knots can damage the suture loop and carry the risk of acute failure of repair site during early rehabilitation.