Are staples or sutures better for closing the skin at cesarean delivery?

The rate of cesarean delivery in the United States reached its highest level yet— 31.8%—in 2007.¹ At more than 1.2 million procedures each year, cesarean delivery is the most common major surgery performed, but few studies have explored the techniques involved. Recent investigations have focused on whether it is advisable to close the peritoneum at the time of cesarean section,² how to perform and close the hysterotomy,³ and the timing of prophylactic antibiotics.^4,5 But we need more evidence to optimize outcomes.

Rousseau and colleagues have made a commendable effort to sift through one of the many unanswered questions regarding cesarean technique: What is the best skin closure? Their prospective, randomized, controlled trial compared staple closure with subcuticular closure using 4-0 Monocryl.

The authors did many things we have come to expect from clinical trials, including:

• a priori sample-size calculation to ensure adequate statistical power
• randomization by group of 8
• stratification of randomization by primary and repeat cesarean delivery
• assessment of wound cosmesis in a blinded, masked fashion.

They found a “statistically significant” difference in the pain score at 6 postoperative weeks between staples and sutures, with staples having the lower mean score (0.2 vs 0.5; P=.04). They also demonstrated shorter operative time for staple closure (32 vs 41 minutes; P<.001).

When such a study is published, it is easy to assume that the issue has been settled and to change or not change practice, depending on your existing technique—but that is often unwise. Every study has limitations. Even when statistically significant benefits are demonstrated, as they are in this study, it may not always be clear whether your patients match the patients in the study, or whether your technique matches what has been administered during the investigation.

In this case, a few problems need to be pointed out:

• Although the evaluation of cosmesis was by masked clinicians, assessment of the primary outcome—pain—was conducted by the patients themselves, who were not masked. One can easily see that awareness of a suture retained beneath the skin might bias a patient’s perception of pain and discomfort. It would be relatively easy to mask the type of closure—even from patients—on postoperative day 1, but masking would become much more difficult when the staples needed to be removed.
• The issue of statistical analysis can sometimes be dull, but is occasionally paramount in determining validity of a study. In this case, the primary outcome—the pain scale—was considered a continuous outcome and compared using a Student’s t-test. An important assumption in this test is that the data are normally distributed. However, the authors do not make it clear whether they tested the data for normalcy. Particularly at the 6-week evaluation, when the mean value was between 0 and 1 for both groups, it seems unlikely that the data were normally distributed. As a result, the difference in pain scores—0.2 vs 0.5—could have been driven by a few high values in one group. Statistically, this would have been easy to manage by changing the comparison to a Wilcoxon rank-sum test.

Despite these limitations, it does seem unlikely that the pain at 6 weeks would have been worse in the staple group.

These findings contrast those of another study of the same topic, which found less pain in the subcuticular suture group.⁶ In that unmasked study, subcuticular closure was determined to be more “cosmetically attractive” by the patients and their physicians. Again, one needs to be concerned about bias.