From Lateral Ankle Sprain to Above-Knee Amputation: A Unique Case Report of Group A Streptococcus Necrotizing Soft-tissue Infection.

Introduction: Necrotizing fasciitis, also referred to necrotizing soft-tissue infection (NSTI), is an infrequent entity that results in orthopedic consultation. It is a rapidly spreading typically associated with a contaminated wound that spreads rapidly along fascial planes resulting in significant morbidity and mortality. However, it is a rare occurrence that such pathology occurs in an atraumatic fashion, which is without a wound through the skin.

Case Report: A 33-year-old female with no significant medical history presented to a walk-in orthopedic clinic with increasing ankle pain after a lateral ankle sprain 2 days prior. Patient denies any fevers, chills, shortness of breath, numbness, tingling, paresthesia, or any additional trauma since the initial ankle sprain. The patient was afebrile, maintaining oxygenation, normotensive, but tachycardic to just over 100. Physical examination was only significant for moderate swelling and ecchymosis about the lateral malleolus. X-rays and venous ultrasound were negative for any associated pathology. After a period of observation, the patient acutely decompensated with a significant increase in pain in the lower leg on passive stretch, an increase in compartment firmness and a worsening tachycardia up to the 120's. The patient was taken emergently for fasciotomies for presumed compartment syndrome. The patient was hemodynamically unstable during the case and transferred to the intensive care unit where she continued to decompensate, requiring multiple vasopressors. The affected extremity became necrotic at the level of the foot and her hemodynamic instability continued, causing a return to the operating room for an emergent guillotine above-knee amputation. The patient progressively stabilized and underwent a formal above-knee amputation 2 days later. Cultures obtained during the second case were positive for Group A Streptococcus.

Conclusion: This case highlights the variable presentation of NSTIs as well as has having a high index of suspicion to ensure this highly morbid and fatal disease process is diagnosed expeditiously. This case is also unique in that it developed without any obvious wounds and that monomicrobial Group A Streptococcus was the culprit, while most NSTIs are polymicrobial.