**10. Types of sutures**

Once you choose a surgical approach it is important to decide the surgical technique and how to suture the muscle.

The suture of a muscle belly is easier in its proximal third and distal third, whereas only in some muscles in the middle third; this is because the tendon fibers flatten and extend into the muscle belly giving the stitches a greater support [54].

Literature describes many types of knots and sutures, such as the conventional Kessler, the modified Kessler and the figure-eight horiziontal mattress and more complex ones, such as the Mason-Allen, the Modified Mason-Allen and suturing the perimeter of the lesion.

The integrity and viability of the remaining muscle tissue is important and indicative for a good prognosis; furthermore the preservation of the epimiysium and the possibility of suturing it to the muscle makes the suture more resistant. From an in vitro study on pig muscles [55], it has been shown that suturing the epimysium gives the suture greater resistance to tensile stress compared to sutures made only on he muscle tissue and perimysium. This is because the epimysium consists of more connective tissue and is composed of two layers, hence much more resistant to tension compared to the perimysium [56].

The Kessler stitch would seem to be more resistant to pull-out suturing than simple stitch or simple suturing with a tendon graft [57].

Kragh [16] compared the Kessler stitch and a stitch combinations (Mason-Allen stitch and stitch around perimeter) in pig muscle. These two types of sutures were considered the strongest in a pilot study carried out before the main study where 9 different types of suturing were compared: simple stitch, running simple (epimysium based, non-core) stitch, the figure of eight stitch, the modifed Kessler stitch, a vertical mattress stitch, a horizontal mattres stitch (core), a horizontal mattress stitch (inverted, epimysium based, non-core), a double right angle stitch, a combination (Modified Mason-Allen and perimeter) stitch. At the tensile tests carried out, the Kessler stitch achieved a maximum load of 35 N, whereas the combined suture achieved 74 N. Not only did the combined suture achieve a greater tensile load, but also the Kessler stitch failed because the sutures were pulled away from the muscle tissue, whereas in the combined suturing, the better distribution of the forces induced a gradual lengthening of the muscle fibers and the stitches were not torn away from the tissue at the 35 mm lengthening.

Similar results were obtained on fresh frozen cadaveric human tissue [58]. Comparing Kessler, figure eight, mattress, Mason-Allen, perimeter and perimeter-Mason-Allen on different muscles of human cadaver, Kessler stitch was the least resistant and tore the muscle with an average load of 1.65 kg; the strongest suture, as was observed in other studies, was the combined suture, Mason-Allen plus perimeter stitch, that withstood a weight of 6.4 kg on average. It was also observed that the simple sutures tend to tear the tissue and the epimysium longitudinally, whereas the more complex sutures failure involves more the transversal tissue. In fact, the epimysium is the key to a robust suture, it is more robust in the tissue where the suture can adhere firmly, the complex sutures involve a greater surface area than the simple ones.

It should also be noted that the simple sutures close the epimysium flaps but in the deep layers, fibers are free and when subsequent contraction of the muscle flaps occur, although held together at the extremity by the suture, deep below the surface tend to form a gap that favors the formation of hematomas, prolong the period of healing and promote excessive fibrosis which may in turn lead to exuberant scar tissue. Hence, the complex suture allows the surgeon to pull together the edges of the tear both at the extremes and deep in the muscle enhancing a greater biological performance [58].

The muscle tissue, due to its physical characteristics, does not offer a solid anchor for sutures which, if positioned improperly, tend to tear the fibers and are pulled from the muscle. When the suturing encompasses multiple points on the injured muscle and the correct technique is used, it can sustain heavy loads and prevent further injuries and ineffective sutures. In theory a stronger suture and one that is less damaging to the muscle tissue should allow earlier mobilization without the risk of failure; therefore improving the healing, shortening the period of immobility and in turn decreasing muscle atrophy.

These in vitro tests demonstrate how to make the most of myorrhaphy. In vivo, however, there are no significant differences between the stitches used Even when comparing a Kessler stitch with a simple suture in a tendon graft, Chien et al. [57] found no difference in terms of muscle healing in rabbits.

Some authors have proposed the use of grafts to reinforce the suture, but It is still unclear whether the use of an augmentation graft suture, as performed by Botte et al. [59] on a case series of 58 patients, is useful to make improvements in clinical and functional outcomes.
