By: William Lear, MD, Board Certified Dermatologist, Fellowship Trained Mohs Surgeon & Fellowship Director at Silver Falls Dermatology. Bill is also CTO of SUTUREGARD® Medical, Inc..
This is a frequent question that is posed to me by my Mohs fellows. First off, by "deep sutures" I am referring to absorbable sutures placed in the dermis of a wound closure. It is traditionally thought these sutures will be providing support to a healing wound longer than the superficial staples or sutures. Anticipated benefits would be less wound dehiscence and improved scar cosmesis.
Wounds heal slowly in the initial few weeks. By the tenth postoperative day, a wound (in an animal model) has about 5% of normal skin strength. As such, the idea of a slowly dissolving internal support, like deep sutures, is enticing.
The process of degradation of most synthetic sutures (e.g. Vicryl, PDS, Maxon) is hydrolysis, which is a chemical reaction. The rate of hydrolysis is affected by:
- hydrolytic enzymes
- other solutes
- surface area of the suture
Most studies on absorbable suture rely on models in which the suture is incubated within a "third space" of an living animal (e.g. rat, pig, mouse) or physiologic solution (e.g. Ringer's lactate) at body temperature. By comparing the strength of the material before and after incubation, the amount of strength retention can be calculated. For example, Vicryl typically loses 50% of its original strength within 2-3 weeks using this methodology.
The problem with this experimental setup is that, unlike a "third space" or Ringer's lactate, the healing dermis is a very dynamic and complex environment. There are waves of clotting factors to stop bleeding, influxes of various inflammatory cells releasing mediators and proliferation of fibroblasts breaking down and making new acellular supports (ie: collagen and elastin). These factors may have a significant impact upon the hydrolytic breakdown of synthetic sutures.
For these reasons, my colleagues and I took it upon ourselves to give absorbable suture a more "real world" test ( https://www.ncbi.nlm.nih.gov/pubmed/27454524 ). We chose an animal model of healing widely considered to best mimic human dermal healing: a Yucatan hairless pig. Two-inch (4.5cm) long full-thickness incisions were performed on the back of these pigs as in prior studies ( https://www.ncbi.nlm.nih.gov/pubmed/21317121 ). Wounds were randomized to either receive three absorbable polyglactin 910 (3-0 Vicryl) buried sutures or no deep sutures at all. All wounds received percutaneous interrupted nylon sutures every 5mm (total of eight sutures per wound).
At day 10 and 42 postoperative, all nylon sutures were removed, and the wounds were evaluated for either tensile strength and histopathology. For tensile strength, the scar and 4cm of adjacent skin was removed and pulled apart with an Instron tensiometer. This measured the force required to burst the wound open. Histopathology was assessed with H&E staining.
The presence of three Vicryl buried sutures in the dermis had NO effect on wound strength at either 10- or 42-days postop. However, absorbable suture created significantly more inflammation in that they created large suture granulomas in the dermis. I liken these results to a chain. A chain (buried suture) loses strength once the chain is broken. However, there is still a lump of chain (suture) in the wound long after it is providing any meaningful strength benefit to the wound. The granulomas that result from chronic foreign suture material manifest as a clinical problem at 4-6 weeks after surgery as perforating sutures ("spitting stitches"). The patient will report "pimples" in the scar line. Once the overlying pustule is ruptured, a small fragment of absorbable suture is usually retrieved.
Since learning these results back in 2016, we have progressively decreased our use of buried absorbable suture. My fellow and I will often use a buried absorbable in the middle of the wound - mostly to get initial apposition of wound edges - not because of a belief in its ability to provide prolonged support. For larger or more tense wounds, buried dermal absorbable often has limited utility in that the tensions required to appose the wound edges leading to ripping of the dermis. In these cases, we will use a SUTUREGARD bridge device to simultaneously allow initial apposition, support the wound intraoperatively. and stretch the wound edges. Even for these wounds under tension, we will use minimal (often no) buried absorbable sutures without adverse consequences.
After performing several thousand cases since 2016 in which we used far fewer buried absorbable sutures, we have noticed no increase in adverse outcomes of wound dehiscence, hematoma, poor cosmesis or other complications. Some may argue that use of a longer duration absorbable, such as PDS or Maxon, will provide longer strength retention. For us, that is not necessary, since we have had no problems with using small amounts of shorter duration absorbable suture.
In our hands, using less buried absorbable sutures saves time, saves overall cost, results in fewer postop "spitting" sutures and has had no adverse clinical outcomes.