Popliteal Artery Pseudoaneurysm: An Unusual Complication of Tibial Traction
Traction pins are an essential tool in the orthopedic surgeon’s armamentarium. Historically a definitive treatment for some fractures, they are mainly used as a temporizing measure today. Despite their frequent use and relative simplicity, traction pins can have complications, many of which can be subtle and easily overlooked.
Here we report on an unusual complication that was difficult to diagnose but caused significant morbidity before being diagnosed and treated. Pseudoaneurysms can cause a range of symptoms and usually present as a painful, tender, pulsatile mass, but in this instance the popliteal artery pseudoaneurysm presented as chronic, painful lower extremity swelling. With diagnosis and treatment, the patient’s symptoms resolved. We discuss the complications associated with traction-pin placement.
After the coiling of the pseudoaneurysm, the calf swelling and pain slowly improved. At 12-week orthopedic follow-up, the patient was no longer using any pain medications, and she noted improvement in the right foot’s neuropathic symptoms. Serial casting was prescribed for the equinus contracture of the ankle. She was allowed to start weight-bearing on the right lower extremity. Radiographs at 12 weeks showed collapse of the superomedial aspect of the femoral head with surrounding sclerosis consistent with posttraumatic avascular necrosis.
At final orthopedic follow-up, about 16 weeks after surgery, the patient reported 0/10 pain. Sensation was noted as being intact throughout the right lower extremity but decreased in the tibial nerve distribution. Ankle range of motion was still limited, with 5° of dorsiflexion and 25° of plantar flexion. The hip was pain-free with flexion of 0° to 100°, 10° of internal rotation, and 20° of external rotation. Additional appointments were scheduled, but the patient did not follow up. Two years after initial injury, she returned to the ED for evaluation of rhinorrhea, and no orthopedic complaints were noted.
Discussion
Skeletal traction begins with the insertion of a wire or pin through a bone. It is extremely important to use proper technique in order to minimize the risks associated with pin insertion.3 Potential pitfalls involve the energy transferred into the bone during insertion, the incisions used to place the pin, and injury to surrounding neurovascular structures. For proximal tibial pins, standard technique dictates placing the pin in a lateral-to-medial direction 2 cm posterior to the tibial tubercle and avoiding the dense anterior cortical bone. At our institution, traction pins are placed with a power drill after the patient is given a local anesthetic or is placed under conscious sedation. Which type of anesthesia to use is based on the patient’s overall condition and on the ED attending physician’s willingness to administer conscious sedation.
The 2 most common types of tibial traction involve use of either a large Steinmann pin attached to a metal bow or a Kirschner wire (K-wire) placed under tension before traction. Which to use is the surgeon’s choice. Surgeons at our institution historically have used Steinmann pins. No studies have directly compared fine-wire and Steinmann-pin traction, but with this complication our institution is evaluating a change to tensioned wires. Compared with large Steinmann pins, fine-wire pins create less of a defect in the bone but also bend or break more easily if tension is not applied or if it fails. A fine wire with its smaller surface area may also cut more easily into osteopenic bone than a large-diameter pin would.
Proximal tibial traction typically is indicated for femoral shaft and acetabular fractures. Although the subcutaneous nature of the tibia makes for easier pin placement, the anatomy of the tibia can predispose this bone to complications. Its triangular shape can lead to intracortical rather than the preferred bicortical pin placement. Increased heat caused by intracortical placement can lead to osteonecrosis and even to damage of surrounding soft tissues. Green and Ripley4 found that chronic osteomyelitis typically resulted from intracortical placement of traction pins.
Injury to surrounding soft tissues, either from heat necrosis or from infection introduced through pin sites, can also have consequences. Pin-site infections increase with duration of treatment, though care seldom requires more than pin removal and antibiotics.5,6 More-invasive infections range from cellulitis surrounding the pin site to subcutaneous abscesses. There is 1 report of a Clostridium perfringens infection leading to death only 5 days after pin placement.7
Neurovascular structures are at risk with any orthopedic procedure. With proximal tibial pins in pediatric patients, the peroneal nerve, the anterior tibial artery, and the proximal physis are most at risk. The deep peroneal nerve and the anterior tibial artery run together deep to the anterior compartment, which places them at highest risk with pin insertion. The peroneal and tibial arteries run deep to the deep posterior compartment along with the tibial nerve behind the posterior cortex of the tibia, which makes injury less likely.8
Historically, long-bone fractures were often treated with traction. Kirby and Fitts9 reported on 342 transfixion pins and wires used in the treatment of 233 long-bone fractures between 1943 and 1945. Of the 305 pins/wires observed over the entire treatment period (average, 6 weeks), only 12 (3.93%) developed a complication. There were 4 loose K-wires, 1 broken wire, and 1 bow failure; Steinmann pins were involved in 1 infection and 2 transient peroneal nerve palsies; and 3 Roger Anderson pins loosened. Pin-tract drainage was not included as a complication if it did not also involve localized or general signs of inflammation. The 2 peroneal nerve palsies were associated with medial-to-lateral pin insertion creating a more posterior pin path.
