The management of wounds following primary lower limb arthroplasty: a prospective, randomised study comparing hydrofibre and central pad dressings

Abstract

Wound care following lower limb arthroplasty has not been subject to in‐depth clinical research, primarily because such wounds usually heal without complication. However, when prosthetic implants are used, serious wound problems can be disastrous (Whitehouse et al. Infect Control Hosp Epidemiol 2002;23:183–9; Lindwell OM. Clin Orthop Relat Res 1986;211:91–103). We report the results of a prospective, randomised, controlled trial comparing a hydrofibre (Aquacel^®) and central pad (Mepore^®) dressing in the management of acute wounds following primary total hip or knee arthroplasty left to heal by primary intention. Dressing performance was measured in 61 patients receiving total hip or knee replacements. There was a significant reduction in the requirement for dressing changes before five postoperative days in the hydrofibre group (43% compared with 77% in the central pad group), and there were fewer blisters amongst patients in the hydrofibre group (13% compared with 26% in the central pad group). We conclude that there is a potential role for hydrofibre dressing in the management of arthroplasty wounds.

Introduction

To date, wound care following lower limb arthroplasty has not been subject to in‐department clinical research, primarily because such wounds usually heal without complications.

However, when implants are used, serious wound problems can be disastrous (1). Wound blisters, for example, are formed in the epidermis adjacent to the surgical incisions and are a significant cause of discomfort, pain and postoperative morbidity and can lead to prolonged hospital stay and even prosthesis sepsis (2, 3). Patients often experience pain caused by traditional gauze wound dressings adhering to the wound and wound bed, and this in turn may also lead to the need for analgesia, increased healing time and prolonged hospital stays (4). Thus, the choice of the most appropriate postoperative wound dressing is very important.

Modern dressings appear to offer a better alternative to the traditional gauze dressings (4). Several studies comparing hydrofibre (Aquacel^®) dressing to other forms of dressings (e.g. ribbon gause, alginate) on wounds left to heal by secondary intention have shown hydrofibre to perform better in terms of ease of application/removal, patient comfort and number of dressing changes required 4, 5, 6, 7.

The aim of this prospective, randomised, controlled trial was to determine whether the hydrofibre dressing performs better than central pad dressing for orthopaedic wounds left to heal by primary intention following lower limb arthroplasty.

Materials and Methods

This a single centre study, comparing two types of dressings one of which is commonly used in joint replacements (Central pad dressing). This was performed at a unit at the Royal National Orthopaedic Hospital in Stanmore where only primary joint replacements were performed and all patients were cared for in a special ward lead by nursing staff.

Materials

Hydrofibre is a highly absorbent sterile hydrocolloid wound dressing composed of sodium carboxymethylcellulose fibres. On contact with wound exudates, it converts into soft gel. Hydrofibre is available in different sizes, conforms to body contours and can be folded into several layers at the time of application. The central pad (Mepore^®) dressing consists of an absorbent pad located centrally on apiece of apertured, non woven polyester fabric, coated with a layer of acrylic adhesive. The polyester backing makes the central pad dressing flexible so that it conforms to body contours.

Study design and statistical methods

This was a prospective, randomised, controlled trial. The primary null hypothesis assumed that use of the hydrofibre dressing would not lead to a reduction in the number of dressing changes required up to 5 days postoperatively. The 5 days target was chosen on the basis that dressing should not be disturbed following surgery unless the wound discharges, and that most patients with total knee replacement would be discharged home 5 days following surgery and would require a dressing change before discharge. In this trial, a difference of 30% in the proportion of patients requiring dressing changes before 5 days could be detected with approximately 80% power at the 5% significance level. This is the difference we have seen in our results.

The percentage of patients requiring a change of dressing or developing wound blisters was compared between the groups using the Chi‐square tests. A total of 61 patients undergoing total hip or total knee arthroplasty were selected. Patients were randomised to receive the hydrofibre or central pad dressing using the software programme Minim (8), which uses the minimisation method to achieve a good balance of patient demographics [in this study: age, body mass index (BMI) and type of arthroplasty (total hip or total knee replacement)] between treatment groups (Table 1).

Table 1.

Randomisation schedule accodring to the Minim programme

		Hydrofibre group	Central pad group
Age	40–60 years	5	5
	60–75 years	13	14
	75–90 years	12	12
BMI	<20	1	1
	20–30	15	16
	>30	14	14
Arthroplasty	Total hip replacement	10	12
	Total knee replacement	20	19

Surgical methods

The surgical procedures were all performed by three surgeons who standardised surgical technique and postoperative care.

All total hip replacements were performed using a modified Hardinge approach, with the patient in lateral position. All total knee replacements were performed under tourniquet, and all were performed using a standard mid‐line incision with medial para‐patellar arthrotomy approach. Skin clips were used for wound closure after all procedures. One drain was used in both total hip and total knee replacements. The suction drain exit was positioned away from the actual wound.

Dressings were applied separately to the wound and the suction drain exit site. This facilitated the removal of the drain after 24 h without disturbing the wound dressing. The suction drain site was dressed with hydrofibre and transparent film (Tagaderm^TM). The hydrofibre wound dressing was also covered and secured in place with transparent film dressing. All dressings were applied under strict aseptic conditions in theatre and if possible left undisturbed for at least 5 days. Wound dressings were changed if they became soaked with exudates and/or if the patient experienced discomfort. After 5 days, if a patient wound with a hydrofibre dressing continued to leak, the dressing was replaced with another made of hydrofibre. If the patient had wound leakage with a central pad dressing this was replaced with another central pad dressing.

All patients received 1·5 g cefuroxime at induction of anaesthesia and further doses of 750 mg at 8 and 16 h postoperatively. All patients also received 20 mg enoxaparin sodium as prophylaxis for deep vein thrombosis starting from the first day postoperatively until discharge.

Assessments

Evaluation of the performance of the dressing was rated on scale of 0 to 5, where 0 indicated easy/most comfortable application or removal, and 5 indicated most difficult/least comfortable (Table 2).

Table 2.

Scoring scale for assessment of patient comfort

Ease of application or removal of dressing	Very easy/most comfortable	Easy/comfortable	Moderate	Not easy	Uncomfortable	Very difficult/painful
Score	0	1	2	3	4	5

The wound assessments were performed by trained staff and supervised by the research nurse, and that involved completing the dressing assessment forms. The presence or absence of blisters and exudate from the drain site or wound was also noted.

Results

Patient disposition and characteristics

Demographic characteristics were well matched between the two arms of the study (Table 3). Forty‐one females and 20 males with an average age of 69·8 years and average BMI of 29, were studied. Medical history included hypertension (19 patients were receiving antihypertensives), angina (n = 5), myocardial infarction (n = 1) and non insulin dependent diabetes (n = 4). Twenty‐three patients underwent total hip replacement and 38 patients underwent total knee replacement. All cases were primarily, uncomplicated procedures. Thirty patients were allocated to the hydrofibre group and 31 patients to the central pad group. The average operating time was 86 min for a total hip replacement and 87 min for a total knee replacement.

Table 3.

Patient demographics

Patients and procedures (n = 61)	Dressing type Hydrofibre (n = 30)	Central pad (n = 31)
Mean age in years (SD)	69·6 (10.9)	70·1 (10.8)
Mean BMI (SD)	29·4 (5.4)	28·5 (4.5)
Total hip replacement	11	12
Total knee replacement	19	19

Dressing assessment

Change of dressing before five postoperative days was required by 13/30 (43%) patients in the hydrofibre group compared with 24/31 (77%) patients in the central pad group. This difference was highly statistically significant (χ² = 7·42, d.f. = 1, P = 0·001). Four of 30 (13%) in the hydrofibre group developed wound blisters compared with 8/31 (26%) patients in the central pad group. This difference between the dressing groups, however, was not statistically significant (χ² = 1·5, d.f. = 1, P = 0·22).

On average, the length of hospital stay for patients who developed blisters was 8 days compared with 7 days for patients who did not develop blisters. The two types of dressing performed equally well in terms of ease of application and removal and patient comfort assessments (median = 4).

Discussion

This prospective, controlled trial compared a widely used central pad dressing with a newer hydrofibre dressing in the setting of acute wounds left to heal by primary intention. Advantages of the hydrofibre dressing over other dressing types have already been established in the setting of chronic wounds and wounds left to heal by secondary intention. The results of one comparative study in patients undergoing total hip arthroplasty demonstrated increased wear time for hydrofibre over ‘standard’ dressing as a result of a reduction in the leakage of blood and exudates out of the hydrofibre dressing – on the basis of these results, there was a shift in clinical wound practice in 60/80 orthopaedic centres in Sweden favouring the use of hydrofibre dressing (6). Another prospective study demonstrated that modern hydrofibre dressing, in the setting of acute surgical wounds left to heal by secondary intention, was more cost effective than traditional ribbon gauze and proflavine – evidenced by improvement in patient quality of life and the facilitation of an earlier discharge from hospital, resulting in clinical staff spending less time on wound management (9).

Hoekstra et al. (10) studied the physical properties of the hydrofibre dressing (Aquacel) in rat partial thickness wounds focusing on the acute inflammatory infiltrate of PMN and macrophages in the wound and dressing. They compared Aquacel to tulle gauze. They found that the Aquacel fibres in the dressing absorb the exudate and swell. PMNs were captured in the dressing and remained active there, resulting in a reduced number of PMNs in the wounds when compared with tulle dressing. A fibrin layer formed between Aquacel and the wound creating a physical barrier. Macrophages infiltrated the wound bed and could not be detected in the Aquacel dressing. They conclude that the use of Aquacel dressing seems to facilitate the physical separation of the defence function of the PMNs and the repair function of the macrophages which lead to reduction of the inflammatory response.

In this study, both the hydrofibre and central pad dressings performed well in terms of ease of application/removal and patient comfort; however, amongst patients in the hydrofibre group, the mean number of times that dressings required changing prior to five postoperative days was significantly reduced. This has two main effects: firstly, less nursing time is required; and secondly, because the dressing is disturbed less often, this aids the healing process by reducing the risk of infection (11).

The importance of patient education, especially in patients undergoing total knee replacement who can see their dressing at all times, should also be born in mind as a part of wound care. Two patients in this study became concerned by the ‘soaked’ appearance of their hydrofibre dressings and assumed that the dressings needed changing because they were not aware that this is the normal appearance of the dressing.

Postoperative blisters require additional dressing changes, take extra nursing time and delay patient discharge. Patients experience discomfort and are at increased risk of developing local infections related to impaired skin integrity (1). With any minor wound sepsis, the risk of developing deep joint sepsis is approximately 2·5–3% (12). Central pad dressing have been associated with blisters in previous studies (3). In this study, twice as many patients in the central pad group developed blisters compared with the hydrofibre group. Patients who developed blisters experienced discomfort and stayed in hospital for an average of 1 day longer than patients who did not develop blisters.

A potential advantage of the hydrofibre dressing is the reintroduction of the concept that sterile dressing can be left without daily changes. This may reduce the potential to introduce infection at dressing changes.

Conclusion

Hydrofibre dressings have a potential role and should be considered in the management of acute lower limb wounds left to heal by primary intention in joint arthroplasty. The benefits of the hydrofibre dressing in terms of reduced blistering and hence patient comfort and also in leaving the dressing undisturbed for longer time which helps in reducing wound handling were clearly demonstrated. This may have long‐term implications on prevention of wound infections. Further trials are needed to confirm such theory.

Acknowledgements

ConvaTec supplied the Aquacel^® dressings used in this study.