The epidemiology, management and impact of surgical wounds healing by secondary intention: a research programme including the SWHSI feasibility RCT
Authors: Chetter Ian , Arundel Catherine , Bell Kerry , Buckley Hannah , Claxton Karl , Corbacho Martin Belen , Cullum Nicky , Dumville Jo , Fairhurst Caroline , Henderson Eileen , Lamb Karen , Long Judith , McCaughan Dorothy , McGinnis Elizabeth , Oswald Angela , Goncalves Pedro Saramago , Sheard Laura , Soares Marta O , Stubbs Nikki , Torgerson David , Welton Nicky 
Published: September 2020

Background
Most surgical incisions heal by primary intention (i.e. wound edges are apposed with sutures, clips or glue); however, some heal by secondary intention (i.e. the wound is left open and heals by formation of granulation tissue). There is, however, a lack of evidence regarding the epidemiology, management and impact on patients’ quality of life of these surgical wounds healing by secondary intention, resulting in uncertainty regarding effective treatments and difficulty in planning care and research.

Objectives
To derive a better understanding of the nature, extent, costs, impact and outcomes of surgical wounds healing by secondary intention, effective treatments, and the value and nature of further research.

Design
Cross-sectional survey; inception cohort; cost-effectiveness and value of implementation analyses; qualitative interviews; and pilot, feasibility randomised controlled trial.

Setting
Acute and community care settings in Leeds and Hull, Yorkshire, UK.

Participants
Adults (or for qualitative interviews, patients or practitioners) with previous experience of a surgical wound healing by secondary intention. Inclusion criteria varied between the individual workstreams.

Interventions
The pilot, feasibility randomised controlled trial compared negative-pressure wound therapy – a device applying a controlled vacuum to a wound via a dressing – with usual care (no negative-pressure wound therapy).

Results
Survey data estimated that treated surgical wounds healing by secondary intention have a point prevalence of 4.1 per 10,000 population (95% confidence interval 3.5 to 4.7 per 10,000 population). Surgical wounds healing by secondary intention most frequently occurred following colorectal surgery (n = 80, 42.8% cross-sectional survey; n = 136, 39.7% inception cohort) and were often planned before surgery (n = 89, 47.6% cross-sectional survey; n = 236, 60.1% inception cohort). Wound care was frequently delivered in community settings (n = 109, 58.3%) and most patients (n = 184, 98.4%) received active wound treatment. Cohort data identified hydrofibre dressings (n = 259, 65.9%) as the most common treatment, although 29.3% (n = 115) of participants used negative-pressure wound therapy at some time during the study. Surgical wounds healing by secondary intention occurred in 81.4% (n = 320) of participants at a median of 86 days (95% confidence interval 75 to 103 days). Baseline wound area (p ≤ 0.01), surgical wound contamination (determined during surgery; p = 0.04) and wound infection at any time (p ≤ 0.01) (i.e. at baseline or postoperatively) were found to be predictors of prolonged healing. Econometric models, using observational, cohort study data, identified that, with little uncertainty, negative-pressure wound therapy treatment is more costly and less effective than standard dressing treatment for the healing of open surgical wounds. Model A (ordinary least squares with imputation) effectiveness: 73 days longer than those who did not receive negative-pressure wound therapy (95% credible interval 33.8 to 112.8 days longer). Model A cost-effectiveness (associated incremental quality-adjusted life-years): observables –0.012 (standard error 0.005) and unobservables –0.008 (standard error 0.011). Model B (two-stage model, logistic and linear regression) effectiveness: 46 days longer than those who did not receive negative-pressure wound therapy (95% credible interval 19.6 to 72.5 days longer). Model B cost-effectiveness (associated incremental quality-adjusted life-years): observables –0.007 (standard error 0.004) and unobservables –0.027 (standard error 0.017). Patient interviews (n = 20) identified initial reactions to surgical wounds healing by secondary intention of shock and disbelief. Impaired quality of life characterised the long healing process, with particular impact on daily living for patients with families or in paid employment. Patients were willing to try any treatment promising wound healing. Health professionals (n = 12) had variable knowledge of surgical wound healing by secondary intention treatments and, frequently, favoured negative-pressure wound therapy, despite the lack of robust evidence. The pilot feasibility randomised controlled trial screened 248 patients for eligibility and subsequently recruited and randomised 40 participants to receive negative-pressure wound therapy or usual care (no negative-pressure wound therapy). Data indicated that it was feasible to complete a full randomised controlled trial to provide definitive evidence for the clinical effectiveness and cost-effectiveness of negative-pressure wound therapy as a treatment for surgical wounds healing by secondary intention. Key elements and recommendations for a larger randomised controlled trial were identified.

Limitations
This research programme was conducted in a single geographical area (i.e. Yorkshire and the Humber, UK) and local guidelines and practices may have affected treatment availability, and so may not represent UK-wide treatment choices. A wide range of wound types were included; however, some wound types may be under-represented, meaning that this research may not represent the overall surgical wound healing by secondary intention population. The lack of randomised controlled trial data on the relative effects of negative-pressure wound therapy in surgical wounds healing by secondary intention resulted in much of the economic modelling being based on observational data. Observational data, even with extensive adjustment, do not negate the potential for unresolved confounding to affect the results, which can reduce confidence in conclusions drawn from observational data. Definitive evidence from a randomised controlled trial may be the only way to overcome this lack of confidence.

Conclusions
This research has provided new information regarding the nature, extent, costs, impacts and outcomes of surgical wounds healing by secondary intention, treatment effectiveness, and the value and nature of future research, while addressing previous uncertainties regarding the problem of surgical wounds healing by secondary intention. Aspects of our research indicate that negative-pressure wound therapy is more costly and less effective than standard dressing for the healing of open surgical wounds. However, because this conclusion is based solely on observational data, it may be affected by unresolved confounding. Should a future randomised controlled trial be considered necessary, its design should reflect careful consideration of the findings of this programme of research.

Future work
This research signals the importance of further research on surgical wound healing by secondary intention. Key research questions raised by this programme of research include (1) which treatments are clinically effective and cost-effective for surgical wound healing by secondary intention for all patients or for particular patient subgroups? (2) Can particular prognostic factors predict time to healing of surgical wound healing by secondary intention? And (3) do psychosocial interventions have the potential to improve quality of life in people with hard-to-heal surgical wound healing by secondary intention? Given that negative-pressure wound therapy has been widely adopted, with relatively little evidence to support its use, the design and outcomes of a randomised controlled trial would need to be carefully considered. We focused in this research on wound healing, and maintain, based on the findings of patient interviews, that this is a key outcome for future research. Impacts of negative-pressure wound therapy on outcomes such as infection and reoperation should also be considered, as should patients’ views of the treatment. The type of patient group recruited and the outcomes of interest will all influence the duration of follow-up of any planned study. The comparator in any future study will also need careful consideration.

Trial registration
Current Controlled Trials ISRCTN12761776.

Funding
This project was funded by the National Institute for Health Research Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 8, No. 7. See the National Institute for Health Research Journals Library website for further project information.