SKIN 
 

March 2019     Volume 3  Issue 2 
 

Copyright 2018 The National Society for Cutaneous Medicine 146 

RISING DERM STARS® 
 

 
Tackling lower extremity surgical site infection in dermatologic surgery 
 
Neera R. Nathan, MD, MSHS1, Su Luo, MD and Suzanne M. Olbricht, MD 
 
1Department of Dermatology, Harvard Medical School, Boston, MA 
 

 
 
Background/Objectives: Surgical site 
infection (SSI) leads to excess healthcare 
costs and may contribute to increasing 
bacterial resistance rates due to use of 
antibiotics. SSI is the most common adverse 
event following dermatologic surgery,1 
especially when the procedure is performed 
on the lower extremity.2 There is a dearth of 
information about factors that contribute to 
SSI following lower extremity dermatologic 
surgery, and further, investigations about 
prevention.  
 
Methods and Results: In the first part of this 
study, we evaluated SSI rates following 
excision or Mohs surgery on the lower 
extremity using patient demographics, tumor 
characteristics, surgical approach and 
pathogenic organisms. Using a retrospective 
review of cases from the Lahey Clinic 
Department of Dermatology over a 15-month 
period, we demonstrated an SSI rate of 6.3% 
(21/332 cases). Of sites evaluated on the 
lower extremity, the lower leg was the most 
commonly infected area (70% of all cases, 
Figure 1). The predominant organism 
demonstrated on culture was 
Staphylococcus aureus, contained in 16 out 
of 21 cases; of which, two were Methicillin-
resistant Staphylococcus aureus. A complete 
or partial purse-string repair closure was 
significantly associated with increased SSI 
rate (p<.0001). Ten of the infected cases 
(47%) were repaired with a purse-string 

closure while only 7.5% of all cases utilized 
this repair. Advanced age, location of the 
tumor, defect size, type of suture used, and 
duration of surgery did not appear to be 
significantly related to SSIs and neither, 
reassuringly, did trainee participation. 
 
Given the predilection for SSI on the lower 
leg, we performed a prospective review of 
calamine and zinc oxide impregnated gauze 
wrap (Unna boot) applied post-procedure to 
see if this could reduce infection rates. An 
additional 410 cases over an 18-month 
period from our institution were analyzed. 
Unna boot was applied post-procedure in 70 
cases on the lower extremity (Table 1). Five 
of the 70 cases were complicated by 
definitive infection (7.1%), compared to 20 
(5.9%) cases that used standard dressings 
and home wound care (p=0.7829).  
 
Conclusion: While a purse-string closure is 
a good option to reduce the surgical defect 
area and time to heal lower extremity 
wounds, our study suggests that there is a 
significantly increased SSI rate with this 
technique. One putative explanation is that a 
purse-string closure without excised dog-
ears leads to greater tension and potential 
pressure necrosis in an area of already 
compromised blood supply. There was no 
significant difference between the rate of 
infection with and without Unna boot applied 
post-procedure. It is possible that selection 



SKIN 
 

March 2019     Volume 3  Issue 2 
 

Copyright 2018 The National Society for Cutaneous Medicine 147 

for patients with an increased risk of infection, 
including patients with venous stasis or 
limited ability to perform home wound care, 
was enriched in the Unna boot cohort. 
Further investigation is necessary to identify 
interventions that may help reduce the high 
infection rate following dermatologic surgery 
on the lower leg.  
 
The control of infections following 
dermatologic surgery has implications not 
only for our field, but for the health care 
system at-large. Thorough investigation of 
this topic will exemplify dermatology as a 
leader in preventing complications and good 
antibiotic stewardship.  
 
Figure 1. Site-specific infection rate following 
lower extremity dermatologic surgery. 
 

 
 
 
 
 
 
 
 
 

Table 1. Lower extremity dermatologic 
surgery infection rate with Unna Boot use. 

  
  
  

With Unna 
boot 

Without 
Unna boot 

 n 

Rate of 
infection 
% n  

Rate of 
infection 
% 

Total 
number of 
Exc or Mohs 70  

34
0  

Total 
suspected 
infections 10 14.30 40 11.80 
No Culture 4  17  
Negative 
culture 1  1   
Total culture-
proven 
infections 5  22   
Distinct 
events 5 7.10 

20
* 5.90 

 
*2 patients had 2 sites each excised on the 
ipsilateral leg and subsequently infected 
following the same visit.  
 

References: 
1. O’Neill, JL, Yee, YS, Solomon, JA, Patel, N, 

Shutty, B, Davis, SA, Robins, DN, 
Williford, PM, Feldman, SR, Pearce, DJ. 
Quantifying and characterizing adverse 
events in dermatologic surgery. 
Dermatol Surg 2013. 39(6): 872-878.  

2. Dixon, AJ, Dixon, MP, Askew, DA, 
Wilkinson, D. Prospective study of 
wound infections in dermatologic 
surgery in absence of prophylactic 
antibiotics. Dermatol Surg 2006. (32)6: 
819-826.