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Humbyrd et al
fluoroquinolones and corticosteroids in the ESRD population explains, at least in part, the higher incidence of ATR in
this population. However, fluoroquinolone use did not seem
to be responsible for the higher ATR rates in the waitlisted
and transplant patients relative to the nonwaitlisted patients.
Approximately 70% of transplant recipients take corticosteroids for maintenance immunosuppression,10 and this
is likely one reason for the higher ATR incidence observed
among transplanted patients compared with nonwaitlisted
patients. It is unclear why the waitlisted patients exposed to
corticosteroids had an even higher incidence of ATR compared with transplanted patients. This is the only covariable
that was significantly different between these 2 populations.
It is possible that the combination of higher activity (compared with nonwaitlisted patients), dialysis, and corticosteroid use compounds risk.
A recent study showed that medical comorbidities were
associated with significantly higher risk of infection after
ATR repair, with an SSI incidence of 18% for those with a
comorbidity compared with 6% for those without.7 In our
study, the risk of SSI for patients with ESRD was low, with
a 30-day cumulative incidence of 6.5%. It is possible that
the patients in our cohort who underwent surgery were the
healthiest patients of the cohort, which may account for
their lower complication rate.
The biggest strength of our study is that we drew from a
large, representative sample of the target population using a
mandatory national registry. Patients with ESRD are eligible for Medicare regardless of their age, and approximately
60% use Medicare as their primary payer.29 Using a data
linkage between ESRD registrations and Medicare claims,
we were able to study all Medicare patients with ESRD
from 1999 through 2013. This study also has several limitations. First, we used administrative codes to ascertain outcomes. The validity of these administrative codes has not
been established. However, because our methods are similar to those of a previous study of the general population,8 it
is unlikely that the use of administrative codes would have
biased our findings. Second, data on some covariables such
as physical function and routine physical activity were
unavailable in our data source. Third, in an effort to limit
our analysis to acute injuries, we limited our analysis of
operative intervention to the first 14 days after ATR diagnosis. It is possible that this approach resulted in an underestimation of operative repairs of ATR. Finally, we ascertained
the incidence of SSI using ICD-9-CM code 998.59 (other
postoperative infection), which is the only code specific for
postoperative infection. It is possible that postoperative
infections were coded using different ICD-9-CM codes, and
our use of a code specific for SSI underestimates the true
infection rate.
We found notably higher ATR rates in the ESRD
population compared with previous studies of the general
population and the Medicare population. The rate for

dialysis-dependent patients not waitlisted for transplant was
almost half the rates for dialysis-dependent patients waitlisted for transplant and patients after transplant. White,
female patients and those with higher BMI were more likely
to sustain ATR. Patients with diabetes mellitus as the cause of
ESRD had higher rates of rupture than did patients with
ESRD from other causes. Patients with hypertension, congestive heart failure, cerebrovascular accident, chronic
obstructive pulmonary disease, cancer, atherosclerosis, current smoking, and inability to ambulate were less likely to
sustain ATR. Similar to the general population, patients with
ESRD treated with fluoroquinolones and/or corticosteroids
were more likely to sustain ATR than patients not treated with
these medications.
Most patients with ESRD with ATRs were treated nonoperatively, but those treated with surgery had SSI rates
similar to those of the general population. However, the
rates of operative treatment were quite low, making it likely
that only the healthiest and most active patients underwent
surgery. These results suggest that ESRD should be considered a risk factor when contemplating surgery but not an
absolute contraindication.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
ICMJE forms for all authors are available online.

Funding
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article: This
work was supported by the National Institute of Diabetes and
Digestive and Kidney Diseases (grants K24DK101828 to DLS
and F30DK095545). The data reported here were supplied by the
US Renal Data System. The interpretation and reporting of these
data are the responsibility of the author(s) and in no way should be
seen as an official policy or interpretation of the US government.

ORCID iD
Casey Jo Humbyrd, MD,

https://orcid.org/0000-0001-9623-4212

References
1. American Medical Association. Current Procedural
Terminology: CPT 2016. Chicago, IL: American Medical
Association; 2016.
2. Aucella F, Valente GL, Catizone L. The role of physical activity in the CKD setting. Kidney Blood Press Res. 2014;39(23):97-106.
3. Basic-Jukic N, Juric I, Racki S, Kes P. Spontaneous tendon
ruptures in patients with end-stage renal disease. Kidney
Blood Press Res. 2009;32(1):32-36.
4. Bradlow A, Thompson JF, Morris PJ, Watson NA. Multiple
spontaneous ruptures of tendons in renal transplant recipient.
BMJ. 1984;288(6414):364-365.

https://www.orcid.org/0000-0001-9623-4212

Table of Contents for the Digital Edition of Foot & Ankle International - July 2018