What is the aim of this review?
The aim of this review was to find out whether animal bite wounds heal better when they are closed with stitches straight away (primary closure), or if the wounds are left open to heal for a short time before closure (delayed closure) or not stitched at all (no closure). We wanted to find out which wounds healed fastest, and if the method of closure affected the likelihood of wound infection, the appearance of the scar, the length of time patients were in hospital, and more serious side effects such as death. To answer this question, we collected and analysed all relevant studies (randomised controlled trials). Randomised controlled trials are medical studies where people are chosen at random to receive different treatments. This type of trial provides the most reliable health evidence. We found four relevant studies.
All the studies we found concerned dog bites. In terms of wound infection, we cannot be certain whether it is better to close dog bite wounds straight away, or wait a while before stitching, or leave them with no stitches. There was little difference in the appearance of the bite scar. Most of the evidence we found was of low certainty due to the size of the studies and the methods used.
What was studied in the review?
Mammalian bite wounds from animals such as dogs, cats and monkeys are a common problem throughout the world. In developed countries, many bite wounds are caused by domestic pets. In lower-income countries bites can also be caused by wild animals. Dogs are generally responsible for the majority of bites. Bite wounds are at high risk of infection as microbes are transmitted into the wound from the animal's mouth. In lower-income countries these wound infections can lead to serious complications and in some cases death.
The first priorities when treating an animal bite are to stop the flow of blood from the wound, provide pain relief, and prevent infection. This can include appropriate vaccination against tetanus and rabies. It is often recommended that bite wounds are not stitched straight away if infection is suspected, as closing an infected wound could delay healing and be potentially fatal.
What are the main results of the review?
In July 2019 we searched for randomised controlled trials comparing primary closure versus delayed or no closure for mammalian bite wounds. We found four relevant studies on dog bites. They were carried out in the UK, Greece and China. No other mammalian bite studies were identified. Three of the studies we included compared primary closure with sutures (immediate stitches) with no closure for dog bite wounds. One study compared primary closure with delayed closure for dog bites. The people in the studies were followed, where stated, from 14 days to three months. Overall, participants from both sexes and all age groups were represented.
We are uncertain whether primary closure of dog bite wounds increases the proportion of wounds which are infection-free compared with no closure (very low-certainty evidence from two studies including a total of 782 people) and compared with delayed closure (very low-certainty evidence from one study with a total of 120 people). There is little difference in the appearance of dog bite wounds when primary closure is compared with no closure (moderate-certainty evidence from one study with a total of 182 participants). None of the included studies reported proportion of wounds healed, the time to complete wound healing, length of hospital stay or adverse events. The number of people in the included studies was small, and the people who assessed the outcomes were aware of which treatment had been given. Both of these are reasons why the results are uncertain.
How up to date is this review?
We searched for studies that had been published up to July 2019.
All the studies we identified concerned dog bites. There is no high-certainty evidence to support or refute existing recommendations concerning primary closure for dog bites. The potential benefits and harms of primary closure compared with delayed or no closure for mammalian bites remain uncertain and more robust trials are needed.
Mammalian bites are a common presentation in emergency and primary healthcare facilities across the world. The World Health Organization recommends postponing the suturing of a bite wound but this has not been evaluated through a systematic review.
To assess the effects of primary closure compared with delayed closure or no closure for mammalian bite wounds.
In July 2019 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.
We included randomised controlled trials which compared primary closure with delayed or no closure for traumatic wounds due to mammalian bite.
Two review authors independently screened titles, abstracts and full-text publications, applied the inclusion criteria, and extracted data. We pooled data using a random-effects model, as appropriate. We used the Cochrane 'Risk of bias' tool and assessed the certainty of the evidence using the GRADE approach.
We found three trials (878 participants) that compared primary closure with no closure for dog bites and one trial (120 participants) that compared primary closure with delayed closure. No other mammalian bite studies were identified. The trials were from the UK (one trial), Greece (one trial) and China (two trials). Overall, participants from both sexes and all age groups were represented.
We are uncertain whether primary closure improves the proportion of wounds which are infection-free compared with no closure, as the certainty of evidence for this outcome was judged to be very low (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.97 to 1.05; 2 studies, 782 participants; I2 = 0%). We downgraded the evidence by one level for high risk of bias and two levels for imprecision. There is no clinically important difference in cosmesis (acceptable physical/cosmetic appearance) of dog bite wounds when primary closure is compared with no closure (mean difference (MD) -1.31, 95% CI -2.03 to -0.59; 1 study, 182 participants). The certainty of evidence for this outcome was judged to be moderate (we downgraded our assessment by one level for imprecision).
We are uncertain whether primary closure improves the proportion of dog bite wounds that are infection-free compared with delayed closure, as the evidence for this outcome was judged to be very low (RR 0.98, 95% CI 0.90 to 1.07; 1 study, 120 participants; I2 = 0%). We downgraded the evidence by one level for high risk of bias and two levels for imprecision.
None of the four trials reported any adverse outcomes such as death or rabies but they were, in any case, unlikely to have been large enough to have satisfactory power to provide precise estimates for these. Important outcomes like time to complete wound healing, proportion of wounds healed, and length of hospital stay were not evaluated.