This is what surgeons live for. The adrenaline rush of life and limb saving surgical intervention. Orthopaedic emergencies are rare and can be life and limb threatening without prompt intervention. For the USMLE, you should know of the open fracture, compartment syndrome, necrotizing fasciitis, and septic arthritis.

Open fracture is the current terminology that replaced the now antiquated “compound fracture.” In an open fracture, the bone either poked through the skin or the skin lacerated or degloved over the fracture. The risk of infection and amputation increases with the amount of soft tissue disruption, and multiple classifications have been developed for open fracture to help guide complex management. Fortunately, management is simplified for the USMLE. If you see an open fracture, the most important next step is prompt administration of intravenous antibiotics. Most (defect less than 10cm) can be treated with a first-generation cephalosporin such as cefazolin for common gram-positive skin flora. More complex injury patterns require the addition of an aminoglycoside such as gentamycin or high dose penicillin such as piperacillin for gram negative organisms. Other scenarios you may encounter are farm injuries, that should be treated with the addition of penicillin and water injuries that should be treated with the addition of a fluoroquinolone to treat organisms such as Aeromonas. The next step is irrigation and debridement in the operating room with bony stabilization – this can be accomplished with external fixation or internal fixation depending on the extent of the injury. In summary, if you see an open fracture, give IV antibiotics and proceed to the operating theatre for irrigation, debridement, and fracture reduction with either external or internal fixation.

Compartment syndrome is serious and can occur after high energy fractures, after crush injury, and with thrombus and sudden revascularization of ischemic tissue. The incidence of compartment syndrome is also higher in open fractures due to the energy required to inflict both. You may recall the 5 P’s of compartment syndrome:

1. Pain out of proportion to exam
2. Paresthesias
3. Palpable swelling
4. Paralysis
5. Peripheral pulses absent

The most sensitive and specific of these P’s is pain out of proportion to exam. This can be elicited effectively by passively stretching toes or fingers, which decreases compartment volume and causes severe pain. Paresthesias are common in compartment syndrome but are not sensitive nor specific. Palpable swelling is true of nearly every fracture and not specific to compartment syndrome. Paralysis and peripheral pulses absent are late findings in compartment syndrome and portend a poor prognosis and possible need for amputation. If compartment syndrome is suspected, the treatment is emergent fasciotomy.

Necrotizing fasciitis is devastating and can result in loss of limb or life if treatment is delayed or the diagnosis is missed. Symptoms of necrotizing fasciitis include rapid progression of abscess or cellulitis, severe pain, high fevers, chills and rigors, tachycardia, and potentially hypotension. The physical exam may show skin bullae, ischemia, edema, induration, erythema, and, most importantly for the USMLE, subcutaneous emphysema from gas producing organisms. The diagnosis of necrotizing fasciitis is clinical. No lab test or image will diagnose it. However, if you are unsure of the diagnosis, then CT or x-ray showing subcutaneous gas may be useful. The LRINEC score is also used by some to aid in the diagnosis when physical examination alone cannot convince you to proceed to the OR. You will not be asked to calculate the LRINEC score on exams, but should have a functional understanding of its utility. What LRINEC says is that patients with extremely elevated CRP, leukocytosis, anemia, hyponatremia, acute renal insufficiency, and hyperglycemia have a higher probability of necrotizing fasciitis. It makes sense if you think about it. The microbial etiology of necrotizing fasciitis is typically polymicrobial (90%), some are caused by group A beta-hemolytic Streptococcus (5%), the marine cases are caused by Marine Vibrio vulnificus, and the remainder are caused by MRSA. Regardless of the etiology, the treatment of necrotizing fasciitis is emergency radical debridement with initiation of broad-spectrum antimicrobials.

The septic joint can be difficult to distinguish from other inflammatory arthritides. All present with acute pain, swelling, and warmth. The majority present with fever and inability to bear weight or range the joint due to pain. Risk factors for septic arthritis include old age, diabetes, rheumatoid arthritis, cirrhosis, HIV, recent bacteremia, IV drug use, and recent surgery on that joint. The joint can become infected by bacteremic spread, direct inoculation, or contiguous spread from adjacent osteomyelitis. It is important to distinguish septic arthritis early as prompt treatment can reduce the risk of cartilage destruction or worsening infection, sepsis, and amputation. When septic joint is suspected, arthrocentesis with cytology, crystals, gram stain, and culture is indicated. A cell count of greater than 50,000 nucleated cells is diagnostic of septic arthritis. Less than 30,000 suggests against septic arthritis. In that case, crystal analysis can point you to gout, think negatively birefringent crystals, or pseudogout, think positively birefringent rhomboid crystals. It’s important to distinguish these conditions. The treatment of gout and pseudogout is medical pain management. The treatment of septic arthritis is irrigation and debridement and broad spectrum intravenous antibiotics.