Statistics from Altmetric.com
A 24-year-old man without past medical history complains of left leg swelling and pain. Six weeks ago, he was kicked playing football and developed a non-displaced fracture of his mid-left fibula. He was immobilised and developed normal weight bearing after 4 weeks. Over the last 3 days, he developed pain, swelling, and inability to weight bear with his left leg along with some chills and sweats. On exam, all vital signs were normal but his left leg was warm, indurated, and red without fluctuence or discharge figure 1. The compartments were soft, but pain was illicited with calf compression. His distal neurovascular exam was intact except for a foot drop.
What is the differential diagnosis?
What are the key historical and clinical features of this case?
Ultrasound images are attached. Figure 1 is the unaffected leg. Figures 2 and 3 are the middle of the lateral compartment of the left leg. Figure 4 is the lateral compartment of the left leg. What do they demonstrate?
What are the stages of pyomyositis?
What are other considerations in a patient with pyomyositis?
1. The most common cause would be a muscle strain, but contusion, haematoma, cellulitis, deep vein thrombosis and fracture complication would also be possible. Less likely, but possible by history, are abscess, osteomyelitis and a deep space infection.
2. The key historical features include recent fracture, increasing pain with ambulation and chills and sweats. Recent fracture suggests the possibility of malunion, refracture due to strain, local infection and osteomyelitis; subsequent immobilisation increases the risk of deep vein thrombosis; pain with ambulation suggests possible large muscle involvement or extension into local joints; and sweats and chills raise concern for systemic inflammation. The presence of indwelling hardware would provide a nidus for infection. A rapidly progressive time course would be concerning, and increase your suspicion for necrotising fasciitis.
The key clinical findings include circumferential erythema, pain with calf compression and a foot drop. The circumferential erythema suggests either a superficial process of the dermal and epidermal layers, or spread across leg compartments and risk for extensive infection. Pain with calf compression raises concern for muscle or deep space involvement. The foot drop suggests either nerve involvement or elevated compartment pressures.
3. Ultrasound is a helpful adjunct in these cases as cellulitis may be difficult to differentiate from an abscess. Figure 2 demonstrates the echo texture of the dermal and muscle layers superficial to bone in the normal leg. Figure 3 demonstrate an extensive fluid pocket within the lateral compartment of the left leg, consistent with an abscess or other process such as myonecrosis. Figure 4 demonstrates fluid tracking behind the deep posterior compartment. Thus, these ultrasound images demonstrate a deep space infection involving the lateral muscle compartment of the leg that tracks along the fascial plane behind the deep posterior compartment. The extensive amount of debris and muscle breakdown suggests a morbid process, such as pyomyositis, fasciitis and so on, for which surgical debridement would be more appropriate than bedside incision and drainage in the emergency department (ED). Necrotising fasciitis is less likely, as the images do not demonstrate any air or gas which would be expected if the infection were this extensive. However, these images do not rule out necrotising disease.
4. Pyomyositis is characterised by three stages. Stage 1 is characterised by low-grade fevers and localised, crampy muscle pain. Swelling may or may not be present and there are no signs of abscess; thus, symptoms may be confused with a viral syndrome, or muscle strain. Stage 2 occurs about 2–3 weeks after the onset of symptoms, with worsening tenderness, fevers and clinical signs of abscess formation. Stage 3 involves systemic toxicity manifested by constitutional symptoms and eventually sepsis. In this case, the patient was moving from stage 2 to stage 3 pyomyositis.
5. Pyomyositis is often the result of haematogenous spread. Morbid aetiologies include endocarditis and causes of occult bacteraemia, which could cause septic emboli. Therefore, it is important to assess for the involvement of other organs. Patients with pyomyositis should also be assessed for causes of immune compromise, such as diabetes, HIV, renal failure, connective tissue disorders, steroid use and obstructions of lymphatic flow. As the causative flora may be mixed, depending on the underlying cause, initial antibiotic coverage should be wide spectrum until cultures are obtained and returned.
The patient was started on ceftriaxone for wide spectrum coverage, clindamycin for treatment of possible anaerobes and methicillin resistent staph aureus (MRSA), and vancomycin for double MRSA coverage. The patient was taken to the operating theatre where approximately 1 L of purulent, necrotic muscle was debrided from the lateral compartment, as well as approximately 250 cc from the posterior deep compartment. The area of pyonecrosis extended from 3 cm above the lateral malleolus to 3 cm distal to the fibular head. Cultures grew out methicillin sensitive staph aureus (MSSA), and the patient was discharged with a wound vac to complete a 1-month course of bactrim and rifampin. He is currently undergoing physical therapy, and is scheduled to have reconstructive surgery of the leg in 3 months.
Competing interests None.
Provenance and peer review Commissioned; internally peer reviewed.
Patient consent Obtained.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.