A 20-year-old collegiate football player is brought to the emergency department due to severe right knee pain following a hard tackle. He cannot bear weight on the right leg. Blood pressure is 142/90 mm Hg, pulse is 108/min, and respirations are 18/min. The right knee is deformed, swollen, and bruised; the lower leg is warm and soft, with a palpable dorsalis pedal pulse. Lateral x-ray of the knee reveals a posterior dislocation, as shown in the exhibit. Immediate reduction is performed under sedation. Which of the following is the best next step in management of this patient?

Question

A 20-year-old collegiate football player is brought to the emergency department due to severe right knee pain following a hard tackle.  He cannot bear weight on the right leg.  Blood pressure is 142/90 mm Hg, pulse is 108/min, and respirations are 18/min.  The right knee is deformed, swollen, and bruised; the lower leg is warm and soft, with a palpable dorsalis pedal pulse.  Lateral x-ray of the knee reveals a posterior dislocation, as shown in the exhibit.  Immediate reduction is performed under sedation.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d96a_458d_bc81_099239dc44b4_MD0003_00 This patient with severe knee pain and deformity after a hard tackle has a posterior knee dislocation (displacement of the proximal tibia posterior to the distal femur). This typically results from a direct blow to the proximal tibia and disrupts multiple ligaments (eg, cruciate, collateral), with possible injury to the neurovascular structures within the popliteal fossa. Injury to the popliteal artery is the most feared complication of any knee dislocation because the resulting lower leg ischemia can cause irreversible injury, requiring above-the-knee amputation. cruciate, collateral popliteal artery Management begins with immediate reduction of the dislocated knee. Given the risk of vascular (eg, popliteal artery) injury, this should be followed by a meticulous vascular examination that includes: Palpation of the popliteal and distal pulses Measurement of the ankle-brachial index (ABI) Duplex ultrasonography (if available) Because pulse examination alone is of limited accuracy in diagnosing vascular injury, obtaining and documenting the ABI are critical. The combination of normal pulses with an ABI >0.9 virtually excludes clinically significant vascular injury. Any signs (eg, diminished pulse, ABI ?0.9) of vascular injury warrant emergency imaging (eg, CT angiography) and vascular consultation. (Choice B) Arthrocentesis (ie, joint fluid aspiration) with synovial fluid analysis is commonly performed to evaluate for infection or crystals in an inflamed joint. It may also be performed for pressure relief of a severe effusion. Although this patient's knee is swollen from trauma, he has none of these indications for arthrocentesis. (Choice C) Peroneal nerve injury occurs in 20%-25% of knee dislocations. When signs of injury (eg, foot drop) are present, nerve conduction studies may help determine injury severity and direct treatment. This patient has no such signs. (Choice D) The posterior drawer test (ie, posterior force applied to the tibia while the knee is flexed) assesses the integrity of the posterior cruciate ligament (PCL), which typically prevents posterior displacement of the tibia relative to the femur. Because complete PCL disruption is required for posterior knee dislocation to occur, testing the PCL is unnecessary; the test would be positive and risks redislocating the knee. Educational objective: Knee dislocation can cause limb-threatening injury to the popliteal artery. Meticulous vascular examination, including measurement of the ankle-brachial index, is necessary for ruling out vascular injury. References: Knee dislocation: a case report, diagnostic vascular work-up, and literature review. (http://www.ncbi.nlm.nih.gov/pubmed/28321343) Can vascular injury be appropriately assessed with physical examination after knee dislocation? (http://www.ncbi.nlm.nih.gov/pubmed/26847454) Acute management of traumatic knee dislocations for the generalist. (http://www.ncbi.nlm.nih.gov/pubmed/26493970)

A 20-Year-Old Collegiate Football Player Is Brought to the Emergency