By Mr Afshin Alijani, Consultant Surgeon, Dundee
Reviewer: Mr Stuart Oglesby, Consultant Surgeon, Dundee
“Wound closure time is not coffee time” – This was the opening statement for the lead article of the February 2019 issue of the British Journal of Surgeon (@BJSurgery). The article was dedicated to the important topic of abdominal wall closure. The author, @acdebeaux subsequently participated in a lively Twitter chat at #bjsconnect on 27th February 2019. I have summarised some of the important aspects of that article and the debate which followed, with a number of additions and expansions.
Up to 20 percent of patients who undergo laparotomy will eventually develop incisional hernias. This translates into many thousands of cases of incisional hernia every year in the UK alone. As a result, any measure that results in even a very modest improvement in the rate of incisional hernia formation can reduce the number of patients suffering from the condition significantly. This is important because incisional hernias notably affect the patients’ quality of life, and surgical repairs put a large financial burden on the health service. There is a strong body of evidence to suggest that the technique used for the abdominal closure can greatly influence the rate of incisional hernia formation.
Several factors are needed for a wound to heal by primary intention, with minimal scarring and as quickly as possible. The clean wound edges need to be held apposed, without tension, until adequate amount of collagen is deposited. In health it takes around 3 weeks for the wound to develop enough tensile strength to remain closed independent of the suture material. This is why many surgeons prefer using slowly absorbable suture material, such as PDS, over rapidly absorbable material, such as Vicryl. Too much tension in the suture will render the wound ischaemic. The causes of this excess tension include obesity, over tightened suture, and abdominal distension following surgery. The patient also needs to have the ability to mount just the right level of inflammatory response for the process of healing. Diabetes, smoking and immunosuppressive therapy are known to dampen down this inflammatory response resulting in poor tissue healing. We also know that patients with defective connective tissue such as those undergoing open abdominal aortic aneurysm repair are at increased risk of chronic wound complications such as incisional hernias.
It is important to minimise the muscle mass enclosed within the suture bites to prevent tissue necrosis; since tissue necrosis can predispose to wound infection and hernia formation. It is reassuring that most of the tensile strength of the closure comes from the collagenous aponeurosis and not from the muscle. A wound disruption during the early postoperative period, also known as a burst abdomen, is more likely to be due to a technical failure. Possible reasons include knot failure or suture material cheese-wiring through the tissue. Late wound disruption can present as an incisional hernia. Although many incisional hernias are due to patient factors, it has been shown that with refined technique the incidence of incisional hernia can be significantly reduced.
In a landmark paper published in 1974 in the BJS, T.P. Jenkins showed the importance of wound to suture length ratio and how a ratio of 1 to 4 helped to reduce the rate of burst abdomens when compared to historical controls. The 1 to 4 rule states that for every cm of wound length, a minimum of 4 cm suture length should be used to ensure a sound tension free closure. Jenkins calculated that lower ratios such as 1 to 2 were associated with large rise in suture tension in the event of abdominal distension postoperatively. We simply do not know what percentage of surgeons currently follow this important rule since the wound to suture length ratio is rarely measured and recorded in the operation notes.
Identical wound to suture length ratio is achieved by either placing large bites far apart or small bites closer together. This has been the subject of a number of randomised controlled trials.
The STITCH trial published in the lancet in 2015 was a multi-centre Dutch study with 560 elective patients being randomised for either small or large bite laparotomy closure. The technique of small bite closure was first introduced by Israelsson in Sweden. In the small bite group, 5 mm thick and 5 mm apart sutures were placed using 2/0 PDS, against the control group of 1 cm bites that were 1 cm apart using heavier looped PDS. Patients were followed up for 12 months and were assessed with a combination of clinical and/or radiological examination looking for incisional hernias. The rate of incisional hernias were significantly reduced in the small bite arm of the trial from 21% to 13%.
Although the STITCH trial adds further evidence in favour of small bite closure, the findings need to be carefully appraised before the technique can be introduced widely. There are a number of methodological issues as well as narrow inclusion criteria that influence its generalisability. Firstly, the two arms of the trial differed in both the size of the tissue bite and the suture size. As a result, the findings could either be due to differences in tissue bites or suture sizes. Secondly, the wound to suture ratio should be 1 to 4 in both arms of the trial. However, the actual wound to suture ratio is 1:5 for the small bite and 1:4 for the large bite groups. Different wound to suture ratios may imply different suture tension in the two arms and hence introduces another extremely important variable not accounted for. Furthermore, the trial excluded emergency surgery and the obese patients. The mean body mass index of the patients was 24 with an upper limit of 27. And lastly, the follow-up of 12 months should be regarded as short. It is known that the incidence of incisional hernias nearly doubles at the 3 year follow up.
Despite these shortcomings, the trial is important in a number of ways. Firstly, it shows us how even small changes in the closure technique can have big effects on the rate of incisional hernia formation. We should all pay more attention to obtaining a 1:4 wound to suture length ratio. The calculated ratio should then be recorded in the operation notes. Secondly, it shows the safety of small bite technique, albeit in an elective normal weight patient population. Taking 5 mm bites is rather brave, particularly in the obese, but perhaps much larger bites closer to 2 cm are unnecessary and we should all be aiming for smaller tissue bites for abdominal closure.
Two further trials currently recruiting patients undergoing midline laparotomies are the continuous versus interrupted (or CONTINT) trial and Hughe’s trial. CONTINT is a German study comparing continuous running suture, using slowly absorbable suture, with interrupted suturing, using rapidly absorbable suture material. Hughe’s trial, on the other hand, is comparing mass closure with added interrupted tension sutures. Hughe’s trial allows the control (mass closure) arm to be the responsible consultant surgeon’s standard closure technique. You can immediately notice that these studies also suffer from the problem of having more than one main variable in each arm of the study.
In the #bjsconnect Twitter Chat, @acdebeaux discussed two further areas of interest. These included the growing evidence in favour of mesh primary closure for the obese patients, and the use of mesh sutures to replace current generation of suture material. Most of the evidence here
is of poor quality and we should await for further studies before making a definitive judgement on the use of mesh material for primary closure of the abdomen.
My impression is that the tightness of the closure is probably more important than the size of the suture bites. An overtightened suture causes ischaemia, particularly when muscle is included, resulting in eventual wound failure and incisional hernia formation.
In my opinion, there is a need for a paradigm shift in the way we view the abdomen. We should move away from viewing the abdominal wall as a tough mechanical barrier and instead we should think of it as a delicate and complex multilayered organ which is easily injured if not handled with care. We would exert more care during the closure and handle the abdominal tissue more delicately if we were to rebrand the technique as the “abdominal wall anastomosis”. Perhaps it is only then that we may stop thinking the wound closure time is coffee time.