Presentation
High-speed motor vehicle collision. Large laceration to the left knee with clinical signs of subcutaneous emphysema.
Patient Data
Diffuse subcutaneous lucencies in keeping with subcutaneous emphysema.
Gas is noted to project over the suprapatellar bursa and deep to the patellar tendon, concerning for intra-articular involvement. The small cortical step of the medial femoral condyle suggests a focal fracture. Normal bony alignment.
Further evaluation with CT and orthopedic opinion is recommended.
Extensive subcutaneous emphysema reflects the distribution of the initial plain film.
A cutaneous defect is noted inferomedially to the patella, consistent with the described laceration and site of air entry.
Most of the gas is located deep to the anterior compartment of thigh, as well as deep to the patellar ligament. A few locules of gas are noted intra-articularly, demonstrating pneumarthrosis (axial, coronal, sagittal). The subcutaneous emphysema does not extend to the medial or posterior compartment of the thigh or the posterior compartment of the leg.
A small, mildly displaced osseous fragment is noted anterior to the medial femoral condyle (axial, coronal, sagittal). Mild associated joint effusion. No further bony injury identified. Normal alignment of the knee joint with mild.
Case Discussion
The patient suffered an open fracture to his left knee with extensive subcutaneous emphysema and intra-articular extension (pneumarthrosis).
He was taken to theater for a knee washout and closure. The small medial femoral condyle fracture was managed conservatively. He had an uncomplicated recovery and was discharged a few days later on a short course of oral antibiotics.
One of the main functions of fascia is to separate muscle groups and neurovascular structures of the limb, creating functional compartments. These compartments help to limit the spread of infection and fluid, in this case, gas. Typically, gas introduced into one fascial compartment will not track to another unless the fascial planes are disrupted, such as in trauma. Fortunately, there was no disruption to the fascial planes in this case.
A consequence of compartmentalisation of the limbs is that if pressure rises in a compartment (e.g. in uncontrolled bleeding or edema) it may compromise adjacent neurovascular structures. This limb-threatening condition is known as compartment syndrome and is a surgical emergency. The treatment is fasciotomy - surgical division of the fascia to relieve pressure in the compartment.
This case demonstrates the importance of knowledge and assessment of the muscular compartments for the extension of fluids like air, edema or blood in fractures and penetrating injuries of the limb.
Case courtesy of Dr Brigitte Russell.
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