After orthopaedic surgery, there is a greater risk of wound infection in patients whose wounds are closed with metallic staples than with sutures.
Our meta-analysis showed no significant difference between the two closure methods with respect to wound discharge, inflammation, necrosis, dehiscence, or allergic reaction.
We consider, however, that only one study had acceptable methodological quality.1
The remaining evidence base presented considerable methodological limitations, including not justifying sample sizes based on a power calculation, poorly blinding patients and assessors to the method of wound closure, not adequately following up patients over a reasonable period of time, and poorly detailing the allocation method to the two groups.
While it might be difficult to blind assessors to the method of wound closure, particularly within the initial postoperative month, blinding of patients is logistically possible.
Accordingly, such limitations should be considered in the design of future studies to improve the evidence base.
Comparison with other studies
Factors that have been cited as important in the choice of wound closure after orthopaedic surgery have included the ease and speed of closure, the level of patients’ discomfort, the complication rate, the final cosmetic result, and the cost.2
Early studies had suggested that the incidence of wound infection might be reduced with staples because of the mechanism of fixation.
Johnson et al19
and Stillman et al20
suggested that skin stapling might cause less damage to the wound’s defences than non-absorbable sutures.
This was based on the principle that the presence of a foreign material might compromise the immune response.
Furthermore, Pickford et al suggested that as staples do not penetrate the incision but cross the incision site, this might prevent the introduction of foreign material.21
Our findings, however, suggested the contrary—namely, that wounds closed with staples rather than sutures have four times the risk of infection.
Whether this is a consequence of the clip being metallic rather than vicryl or nylon material or whether the tension developed through a mattress suture closure is superior to that of staples in reducing the incidence of opening the wound during mobilisation remains unclear.
Our conclusion was reached, however, after application of the statistical method for the whole evidence base and was significant for hip surgery but not knee surgery.
The rationale for this has been postulated by Khan et al,1
who pointed out that knee wounds are considerably longer than hip wounds and are subjected to more mobility as they are covered by less tissue.
As only 88 patients have been assessed in relation to knee wound closure with staples compared with sutures, this observation remains underpowered at present.
It remains unclear as to whether there was a difference in cosmetic result between wounds closed with sutures or staples after orthopaedic surgery.1 17
As the present included studies did not analyse the results based on different comorbidities, age, or skin type, we do not know whether patients with difference skin types might present with differing outcomes—for example, Afro-Caribbean patients are more susceptible to hypertrophic and keloid scarring.22
Previous studies have examined the clinical outcomes of skin closure with continuous or subcuticular interrupted suture techniques for repair of episiotomy or second degree perineal tears23 24 25
and vascular surgery.26 27
Most orthopaedic studies used interrupted subcuticular suture techniques for wound closure, while only two studies adopted a continuous suture technique.910
There were no substantial differences in the trends in results between these two studies and the other studies included in this review As this has yet to be empirically studied, it is therefore unclear whether the method of suture closure is a confounding variable with respect to the rate of complications, the patients’ reported satisfaction for cosmetic results, and the discomfort reported through the removal of suture material.
Graham et al28
proposed that deposition of wound collagen is directly related to wound oxygenation and perfusion.29 30
They reported more favourable blood perfusion characteristics in wounds closed with staples rather than sutures, in addition to a significantly higher blood contact in the wound at seven days compared with the suture group (P=0.
We found that the incidence of wound infection was greater with staples than with sutures.
Therefore, our findings do not confirm those of Graham et al,28
as oxygen perfusion might be associated with wound infection and necrosis.
The influence of oxygen perfusion in hip wounds and knee wounds, which was assessed in the study of Graham et al,28
Murphy et al suggested that poor results with staples were attributable to poor technique in staple placement.9
The accuracy of suture or staple closure and choice of closure method can have an effect on the accuracy of coaptation of the dermal margins.
Poor technique can lead to suboptimal healing.10
This might cause oozing wound edges and delay in healing and increase the potential for infection.8 9
Superficial infection in hip and knee arthroplasty is a worrying clinical sign because of the risk of the infection spreading through the dermal layers to the implant.
With the increased pressure on surgical time, and the advances in non-medical staff taking extended roles in wound closure, such considerations might be important when considering outcomes within each institution.
Metal staples have been regarded as a more expensive option for wound closure,9 10
though costs could be reduced by reduced theatre time and ease of clip removal compared with suturing wounds.
This might prove to be false economy, however, as the consequences of a deep infection for the patient are substantial through the increased costs associated with medical care and admission to hospital.31
Furthermore, as the number of dressing changes was greater in those who underwent skin stapling, and as a specific staple remover is required, the overall cost of the staples and applicator is mitigated by savings in dressing costs.
Although Singh et al estimated the cost effectiveness of these two closure methods,2
no formal cost-benefit analysis has been undertaken.
One study assessed patients’ satisfaction1
and reported no significant difference between the groups.1
Stockley and Elson10
and Singh et al2
reported that staples were invariably more painful to remove than sutures.
The relative discomfort of staple removal compared with suture removal has been previously cited in the non-orthopaedic literature.32 33 34
Secondly, some authors have suggested that there might be greater satisfaction for surgeons in using staples than sutures.
The time saving benefits of staples might have a psychological effect on surgeons and theatre staff, particular after a long operation.9 10 35
Given the difference in the incidence of superficial wound infection, and the limited empirical evidence for patients’ or surgeons’ preference for staple closure, there is insufficient evidence to justify the use of staples over sutures.
Our findings can be directly generalised only to orthopaedic hip and knee arthroplasty surgery.
Different methods of skin closure, however, have been assessed in other surgical procedures, such as scalp lacerations.
While stapling has been shown to be faster and less expensive than suturing in the repair of uncomplicated scalp lacerations in children and adults, no differences in complication rates, including infection, have been shown.36 37 38
Similarly, there was no significant difference in complications after abdominal wound closure.39
In this specific population, however, stapling resulted in poorer cosmetic scores than suturing in transverse abdominal wounds.39
Ranaboldo and Rowe-Jones reported that wound pain and requirement for analgesia was significantly lower in patients whose laparotomy wounds were closed with sutures compared with staples.40
Finally, a systematic review of methods of skin closure in caesarean section reported that use of absorbable subcuticular sutures resulted in less postoperative pain and yielded a better cosmetic result than staples.41
While there seems to be consensus that staple closure is faster than suture closure, there remains some variation between studies for cosmetic results and pain outcomes.
There seemed to be no significant difference in complication rates, including wound infection, between caesarean wounds closed with sutures compared with staples, contrary to our findings.
By re-evaluating this issue with well designed randomised controlled trials it will be possible to compare the findings of orthopaedic to other surgical procedures.
Strengths and limitations
We found no significant difference in the presentation of inflammation for wounds closed with sutures rather than staples, which was unexpected given the differences exhibited between methods for infection.
This outcome, however, was assessed in only two studies with small cohorts so the lack of a statistical difference might have been because of type II statistical error.42
We also noted considerable heterogeneity, possibly as a consequence of the small number of patients reviewed, so it might be inappropriate to use these results based on the current pooled analysis.
Further study of the effect of inflammation as an outcome with large sufficiently powerful samples is therefore indicated to assess whether this outcome measure differs between orthopaedic wounds closed with sutures compared with staples.
A major limitation within the literature was that none of the studies differentiated between superficial and deep wound infections in their results.While superficial wound infections might be problematic for the patient, these will usually resolve with antibiotics. In contrast, a deep wound infection has a considerably greater impact, particularly in arthroplasty surgery, and requires extensive debridement, wound wash-out, prosthesis revision surgery, and, potentially, amputation.
The evidence base poorly presented important demographic details for their cohorts.
For example, only three studies provided data on patients’ age.
Accordingly, we could not assess whether this was an important variable between the two groups.
Similarly, the studies poorly presented details regarding patients’ medical history, use of steroids, weight, and body mass index, which might also have been confounding variables.
Propensity scoring methods would compensate for potential differences in important characteristics.43
As only Khan et al1
and Shetty et al4
concealed patient allocation, allocation bias might have affected findings because the patient’s clinical presentation might have influenced the surgeon’s choice of methods before randomisation.
Concealed randomisation should therefore be considered in the design of future research to prevent such bias.
Only the study of Khan et al can be judged as methodologically well designed and appropriately reported.1
The remaining papers reviewed had considerable limitations.
Given that Khan et al’s cohort constituted 19% of the total meta-analysis cohort,1
the weaker studies might have considerably affected our results.
Accordingly, we recommend that further well designed randomised controlled trials are conducted to further examine the results of this meta-analysis.
After this, orthopaedic surgeons will then be able to justify their use of closure method by using a more rigorous evidence base than is currently available.
Finally, nearly all identified papers compared the outcome of method of wound closure in hip surgery.
We did not find any studies assessing the effect of different methods in spinal surgery, only one study was identified on the effects of knee surgery, and only Murphy et al’s study included patients who had undergone upper limb surgery.9
The limited evidence, particularly in upper limb surgery, might reflect a predominance of suture closure after elbow, wrist, and hand surgery.
The clinical justification for this might be on ease of sutured closure compared with staples in hand surgery or on an improved cosmetic result with sutures.