This case report describes a rare complication of a continuous popliteal nerve catheter (CPNC), where a 53-year-old woman developed a posterior thigh abscess secondary to the CPNC placed after surgery for a trimalleolar fracture. Despite removal of the catheter, her symptoms worsened with fever and increasing thigh pain. Imaging revealed a large abscess, requiring radical debridement of two-thirds of her posterior thigh compartment. Cultures grew methicillin-resistant Staphylococcus aureus. She required months of IV antibiotics and extensive physical therapy for recovery. The report reviews typical CPNC complications but highlights serious infection as rare, discussing this case and two similar reports where abscess developed secondary to MRSA from an ind

1. Thigh Abscess Secondary to Continuous Popliteal Nerve Catheter: A Rare Complication
Jennifer Gerres, DPM ; Megan Oltmann, DPM ; Michael Wheeler, DPM
1
2
2
Residents, Cleveland Clinic/Healthspan and Cleveland Clinic/Mercy Regional Medical Center
1
Abstract
The continuous popliteal nerve catheter (CPNC) is an increasingly popular
adjuvant therapy to reduce postoperative pain in lower extremity surgery. It has
few noted complications in the literature with serious infectious complications
reported at 0.25% to 0.75%. We present the rare case of a posterior thigh
abscess secondary to a CPNC, which requires multiple surgical debridements
and long-term IV antibiotic use. The literature review highlights complications
of the continuous popliteal nerve catheter with special emphasis upon infection
risk factors.
Introduction
A continuous popliteal nerve catheter (CPNC) comprises the percutaneous
insertion of a catheter adjacent to the sciatic nerve with a local anesthetic
infusion, which offers anesthesia and analgesia for multiple days.1 Unlike a
single bolus injection, which would last 8 to 24 hours, the CPNC is desirable
when a prolonged neural blockade would provide relief. Using a continuous
infusion, the need for general anesthesia is reduced2 as well as lessens the
patient’s postoperative opioid requirements.2-5 Furthermore, the CPNC is
associated with lower postoperative pain scores and reduced breakthrough
pain; and less nausea and vomiting, urinary retention, opioid-related side
effects, and sleep disturbances.1,2
Complications are rare in reported literature with catheter dislodgement,
catheter obstruction, or neuropathy the most common. Local infection of
peripheral nerve catheters ranges from 0 to 3% in the literature and serious
infection less than 1%.
Case Study
A 53-year-old non-diabetic female underwent open reduction with internal
fixation of a left trimalleolar fracture. Prior to surgery, a CPNC was inserted
for postoperative pain management (0.2% ropivicaine at 10ml/h), and the
patient received 1g cefazolin IV pre-and postoperatively. Despite the use of
oral opioids, the patient could not be weaned from the CPNC and remained
in hospital. Upon postoperative day 3, the patient began to complain of
generalized left thigh pain. Vital signs demonstrated a pulse of 100 and
oral temperature of 101°F Physical exam of the surgical incision did not
.
elicit malodor or purulence with the wound well-coapted. Peri-catheter
erythema was noted, but without induration or pain to the catheter site.
Lab work revealed a white count of 14.6, and urine and blood cultures
were negative for growth. Ultrasound of bilateral lower extremities was
negative for deep vein thrombosis; however, enlarged lymph nodes in the
left groin were observed.
2
Case Study
Discussion
With continued fever and no other infectious source determined, on postoperative day
4, the CPNC was removed without note of purulence or induration at the catheter
site. Erythema was still observed peri-catheter without improvement or worsening since
postoperative day 3.
Despite CPNC removal, the patient continued to exhibit fever and complained of chills,
sweats, and increasing left posterior thigh pain, specifically to the area of the catheter
insertion. On physical exam, inspection of the surgical wound did not reveal signs of
infection; however, upon assessment of the popliteal
nerve catheter site it was found to be erythematous
and painful to touch with frank induration. No crepitus,
fluctuance, or purulence was elicited. Lymph nodes of
the left groin were palpable. Computed tomography
demonstrated abscess (Figure 1) within the soft tissue
adjacent to the former CPNC site. The primary team
performed an incision and drainage of the CPNC site.
Two, 2cm incisions were made over the site and 5cc of
purulent material was expressed and sent for culture
and sensitivity. No undermining or tracking of the
tissue was noted. The patient began empiric therapy
of 1g vancomycin IV q12h and 3.375g piperacillintazobactam IV q6h until definitive cultures. Cultures demonstrated Methicillin-resistant
Staphylococcus aureus, and piperacillin-tazobactam was discontinued and rifampin
600mg PO q24h was added as adjuvant therapy.
However, 3 days after the incision and drainage with initiation of antibiotic therapy, fever
and leukocytosis persisted, and now on physical exam, the entirety of the posterior
thigh—from the popliteal fossa to the ischial tuberosity—was erythematous and
indurated. Magnetic resonance imaging showed widespread multiloculated abscess
(Figure 2) and diffuse edema to the left posterior
thigh compartment (Figures 3, 4, & 5). The patient
underwent emergency radical debridement of
the left thigh. A serpentine incision extended
from the ischial tuberosity to the proximal calf
of the posterior thigh. Two-thirds of the posterior
compartment as well as the medial and lateral
heads of the gastrocnemius were involved and
debrided or excised. Significant phlegmon was
noted along the course of the sciatic nerve. The
popliteal fossa was explored and the knee joint was
not breached. Negative wound pressure therapy
was applied to the wound until primary closure
could be performed. The patient experienced
hypovolemic shock and spent three days in surgical
intensive care where she received 6 units PRBCs and 2 units FFP
.
Post radical debridement, the patient remained afebrile and the leukocytosis resolved.
She underwent two negative pressure therapy dressing changes with further debridement
of non-viable tissue until the wound was primarily closed. Rifampin was discontinued
due to patient intolerance. Thirty-one days after initial admission for the ORIF of the
left trimalleolar ankle fracture the patient was discharged to a rehabilitation center on
a 6-week course of 1g vancomycin IV q12h. She underwent 9 months (3 months within
an acute rehab setting) of extensive physical and occupational therapy. At one year,
the patient continued to have discomfort when sitting for long periods, and ambulated
without difficulty or assistance. Radiographs of the trimalleolar fracture demonstrated
a well-healed fracture without periosteal reaction or loosening of fixation.
Interestingly, Capdevila and colleagues12 reported no abscess, local infection, or
colonization of 167 CPNCs with Staphylococcus aureus. Of those 112 CPNCs that were
colonized, 77.3% were colonized with coagulase-negative Staphylococcus and 18.1%
with gram-negative bacillus. None of the colonized catheters resulted in abscess
or infection. Staphylococcus aureus, specifically Methicillin-resistant S. Aureus, was
the infective agent in two reported cases of CPNC abscess.14-16 One case, described
by Compère et al.,14,15 of MRSA abscess occurred in a study of 400 patients with
CPNCs 15 days after the catheter was removed. In that patient, the duration of the
CPNC was 5 days. The patient required surgical debridement and IV vancomycin for
1 month. Tucker et al.16 described the case of posterior thigh abscess secondary
to MRSA infection, which presented 4 days after CPNC insertion. Like our case, the
catheter was removed, but symptoms worsened and a CT demonstrated an abscess
to the popliteal fossa. Not only was the duration of the CPNC similar to our case, but
poor pain control despite continuous infusion of local anesthetic and opioids may
have been an early sign of infection for a change in local pH can reduce anesthetic
efficacy. It is imperative under those circumstances to inspect the catheter site for
dislodgement, obstruction, or infection.
Figure 3
Figure 4
Figure 5
Discussion
The benefits of CPNC are well documented in the literature with lower patient reported
postoperative pain scores and decreased patient need for postoperative opioids most
significant. Singelyn et al.4 compared the CPNC to intramuscular injection of opioids and
to IV PCA morphine in the postoperative setting. Only 8% of those with the CPNC required
supplemental opioids; whereas, those with IM opioids and IV PCA morphine required 91%
and 100% supplementation respectively. The patients with CPNC also reported less nausea
and vomiting. In the study by White et al.,6 a prospective, randomized, placebo-controlled
study of continuous infusion of bupivacaine versus normal saline via a popliteal catheter
after a single bolus of bupivacaine, after 48 hours, a significant reduction in pain scores,
opioid use, and anti-emetic use was noted in the treatment group. This is further supported
by a similar study conducted by Elliot and colleagues2 who observed that after 72 hours while
the overall pain scores in both groups were low, those in the CPNC group had significantly
lower pain scores with a considerably less requirement for supplemental opioids.
Complications of peripheral nerve catheters include catheter dislodgement or obstruction,
leaking of infusate at catheter site, peri-catheter hematoma,1 and vascular rupture.7 Borgeat
and colleagues8 reported 2 cases of inflammation at the catheter site in 1001 patients that
underwent a continuous popliteal nerve catheter. No incidences of infection or neuropathy
were noted. When observed, the neuropathy is transient in nature9 with 41% of patients
experiencing some paresthesia,10 but persistent sensory deficit is reported at 1.91%.11
Localized inflammation of the peripheral nerve catheter varies between 0 to 13.7%, with
localized infection between 0 to 3%.9 However, bacterial colonization of the indwelling
catheter is high, 6 to 57%, depending on the location of the catheter.9,12 If colonization of
the catheter occurs, it is most likely Staphylococcus epidermidis12; however, if abscess or
infection occurs, the mostly like organism is Staphylococcus aureus.13 Our patient’s infective
organism was Methicillin-resistant Staphylococcus aureus.
Risk factors for CPNC infection include postoperative intensive care stay, catheter
duration of greater than 72 hours, absence of antibiotic prophylaxis13 and poor
aseptic technique.14 Other risk factors that have been described are male sex,
trauma, and contaminated local anesthetic solution. Of the risk factors defined, our
patient’s CPNC remained for 4 days. Pre-existing surgical site infection has not been
shown to increase risk of indwelling catheter infection.9,17 While lack of antibiotic
prophylaxis is a risk factor for infection, in multiple studies antibiotics were not
routinely given and no infection was reported.9,11 Lastly, to reduce the potential of
CPNC infection one must adhere to strict aseptic technique, use protective barriers
and skin disinfectants with an alcohol base, and remove the CPNC within 72 hours
of insertion.
In conclusion, while colonization of indwelling peripheral nerve catheters are
common, infections are rare with infection of CPNCs less than 1%. While it is
important to recognize the infectious potential of an indwelling catheter, our case is
the exception and the literature supports the use of CPNCs as a safe and beneficial
method of analgesia.
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