CanadiEM Frontline Primer

CanadiEM Frontline Primer – MSK – Extremity Soft Tissue Abnormalities

In Medical Concepts by Afsheen MeharLeave a Comment

Can’t Miss Diagnoses

  • Necrotizing Fasciitis
  • Toxic Shock Syndrome
  • Venous Thromboembolism (e.g. DVT)
  • Peripheral Arterial Occlusion
  • Abscess
  • Tendon Rupture
  • Cellulitis
  • Burns (including chemical)
Common Diagnoses:
  • Sprains
  • Strains
  • Neuropathies


Points to focus upon


To note and document; Tetanus status, anticoagulation, surgical manipulation if any.
Ask about recent intercurrent febrile illnesses.
May have “pain out of proportion” or localized hypoesthesia.


Check for peripheral pulses (they are the vital signs of the extremities!) – if absent, consider peripheral vascular disease.
CAUTION – Absent pulses, paresthesias, pallor, pulselessness may be signs of vascular occlusion (arterial clot) or compartment syndrome (e.g. from crush injury, recent fracture reduction, etc.)

For Infections:
– Look for “portals of entry” for infection (abrasions, recent surgery)
– Check joints for any involvement
– Examine for rapidly spreading rash, purulence, bullae, blisters, crepitus.

CAUTION Nec Fasc patients break all the rules:
– They may look surprisingly well.
– They may NOT have any overlying cellulitis/rash
– They may have a flat affect (known as “La Belle Indifference”).

Approach to Purulent SSTI
Approach to Non-Purulent SSTI

Clinical Decision Tools


DO NOT DELAY SURGICAL INTERVENTION IF SUSPECTING NEC FASC. Definitive Management is surgical debridement.

  • CBC, BUN, Cr, Lytes, Glucose, VBG,
  • Consider Blood Cultures PRIOR TO antibiotics
  • C-reactive protein (CRP)
  • Consider joint aspiration


Check your specific hospital guidelines for specific local antibiotic resistance as well as dosing and duration.
In general, if you are considering a biopsy or aspiration, it is best to do this before starting antibiotics for best lab results. However, please use clinical judgement and if the patient is unstable, save the life over the limb.

General aspiration locations:
Shoulder- debated image guided vs Posterior approach
Elbow- Radial triangle
Wrist- Dorsal above lister’s tubercle
Hip- Image guided
Knee- Anterior medial or lateral to patella
Ankle- Anteromedial or anterolateral.

Necrotizing Fasciitis

1. Surgical Debridement
2. While awaiting OR to be ready, consider empiric antibiotic therapy:
One of [ Meropenem 1 g IV q8h OR Piperacillin-tazobactam 3.375 g IV q6h PLUS

One of [Vancomycin 15 mg/kg q12 h IV OR Linezolid 600 mg IV q12h OR Clindamycin 600 mg IV) PLUS

AGAIN, DO NOT DELAY SURGICAL INTERVENTION IF SUSPECTING NEC FASC. Definitive Management is surgical debridement.

Purulent SSTI

Severe Purulent SSTI

  • IV Piperacillin/Tazobactam and Vancomycin; or
  • Oral or IV Clindamycin (same bioavailability); or
  • IV Linezolid

Mild/Moderate Purulent SSTI: Choose one or combination

  • Oral TMP/SMX; or
  • Oral or IV Clindamycin; or
  • Oral Doxycycline

Of note, if no overlying cellulitis or comorbid conditions, Choosing Wisely Canada recommends discussing the use of antibiotics with patients as the benefits conferred by antibiotics may not outweigh the risks associated with their use.

Non-Purulent SSTI

Severe non-purulent SSTI:
1. IV Piperacillin/Tazobactam AND Vancomycin AND IV Clindamycin (if concern for necrotizing infection)

Mild/Moderate non-purulent SSTI:
1. Oral Cephalexin; OR
2. IV Cefazolinn; OR
3. Oral or IV Clindamycin
See notes below

– Consider oral antibiotics whenever possible. 5-7 days. Usually, first-generation cephalosporin (e.g. cephalexin) to start.
– If progressing despite antibiotics or signs of systemic infection, consider IV cephalosporins.
– If allergic (anaphylaxis) to cephalosporins, may consider Clindamycin as an alternative therapy (Bonus: it has same bioavailability both PO or IV, so go ahead a treat PO – just ask patient to also start probiotics since they may get antibiotic-related diarrhea).

Recommended reading, videos, and podcasts

Would you like to read more MSK topics? Read about common fractures or joint pain.

This is part of the CanadiEM Frontline Primer. An introduction to the primer can be found here. To return to the Primer content overview click here.

This post was copyedited and uploaded by Evan Formosa.

Afsheen Mehar

Dr. Afsheen Mehar is a resident physician at the University of Toronto in the RCPSC Emergency Medicine Training Program. Her greatest passions are medical education, POCUS and austere medicine. She holds an RDMS certification in ultrasound.

Geoffrey Comp

Emergency medicine physician in Phoenix, AZ. Creighton University School of Medicine/Maricopa Medical Center core residency faculty. Interest in medical education and developing various ways to teach emergency medicine. Clinical Assistant Professor - University of Arizona College of Medicine Phoenix.

Teresa Chan

Senior Editor at CanadiEM
Emergency Physician. Medical Educator. #FOAMed Supporter, Producer and Researcher. Chief Strategy Officer of CanadiEM. Associate Professor, Division of Emergency Medicine, Department of Medicine, McMaster University.

Colm McCarthy

Colm completed his residency at McMaster University in orthopaedic surgery along with a 5 month fellowship in orthopaedic trauma surgery. He will be having a second fellowship in hip and knee reconstruction at the Brigham and Women’s Hospital. He enjoys collaborative work, medical education, and physical advocacy.