[Mechanical Testing of Tendons Sutured with Newly Developed Biomaterial]

PURPOSE OF THE STUDY Tendon injuries continue to be a highly topical issue. Research and clinical activities in this area aim to achieve an optimal repair of the damaged tendon. Such suture is characterised by maximum tensile strength, resistance to gapping at the repair site, preservation of smooth surface, prevention of adhesions and facilitation of fast rehabilitation and active tendon movement. The suture as such is required to show mechanical resistance in particular. Considered optimal is the use of core suture of the tendon in combination with epitendinous suture. The group of researchers has for several years already been exploring new materials. They can contribute to better balance between adequate mechanical strength of the suture and biological support of healing. MATERIAL AND METHODS The study was carried out as an ex vivo experiment on porcine tendon models. A tendon segment was obtained from slaughtered animals and a total rupture of the tendon was imitated by sharp cutting of its central portion. Subsequently, the tendon was repaired by Adelaide suture using coated braided polyester (Ethibond) and two types of new polyamide 6 based (PA6) sutures. The first suture was designed as an unabsorbable polyester core (PES silk) surrounded by absorbable PA6 nanofibres. The second suture was created by braiding a PES silk yarn and two viscose yarns with PA6 nanofibres into a composite surgical suture. As a part of the study also examined was the tensile strength of suture with the use of other stitches, effect of the shape of the needle s point on the tensile strength of the suture and the effect of secured mattress peritendinous suture. The tensile strength of the suture was tested until failure and the achieved maximum load was monitored. RESULTS The PES core yarn with PA6 nanofibre braiding showed lower tensile strength (28.5 ± 5.2 N) than the yarn braided from one PES yarn and two viscose yarns with PA6 nanofibres (45.7 ± 6.7 N). Both newly developed sutures, however, fail to achieve the tensile strength of Ethibond (100.3 ± 19.1 N). In case of Ethibond suture using various types of stitches, the lowest tensile strength was observed in McLarney 4-strand core suture (68.8 ± 18.7 N). A higher tensile strength was achieved by Adelaide 4-strand core suture (83.6 ± 11.2 N). The highest tensile strength was seen in 6-strand core Savage suture (147.4 ± 22.7 N). When the effect of the type of needle was tested, a statistically significant difference between the taper point needle (72.0 ± 7.0 N) and reverse cutting needle (63.3 ± 9.6 N) was observed. In case of McLarney suture the epitendinous stitch increased the tensile strength by 46.2% and in case of Adelaide suture by 48.3%. CONCLUSIONS For tendon core suture, the use of sutures with multiple longitudinal segments seems more appropriate. The epitendinous suture can considerably reinforce the basic load-bearing core suture. Also observed was not an insignificant effect of the needle profile on the resulting tensile strength of the suture. In materials developed by us, more suitable seems to be the design of braiding of absorbable nanofibers with a load-bearing non-absorbable yarn. While the mechanical tensile strength of new materials is lower, the benefits are expected in the form of biological support of healing. Moreover, the nanofibers can be used as a carrier of biological and therapeutic substances. Further improvement of mechanical properties of the newly developed biomaterial can be foreseen if the material of the load-bearing non-absorbable yarn is changed or the load-bearing yarn and nanofibres ratio modified. This pilot study shall use the findings for further development and modification of new materials in basic research and shall also verify the biological aspects and the course of healing in in vivo studies. Key words: tendon, suture, pig, biomaterials, nanofibres, mechanical testing, healing, polyester, Adelaide.