The case:
40-year-old man presented to the Emergency Department with a laceration after an iron bed frame fell on his knee 1 day prior. On exam, the patient had a horizontal 4-5 cm laceration on the anterior-medial aspect of his right knee with significant swelling and erythema around the joint. The wound appeared dirty, with purulent, foul smelling discharge and the knee was warm to palpation. Range of motion was limited due to pain. Radiographs were negative. Considering the overlying laceration and evidence of septic arthritis, antibiotics were administered, a CT was ordered, and the Orthopedics service was consulted. CT demonstrated no air within the joint, but the patient was taken the operating room for surgical I&D of his knee. Traumatic arthrotomy was confirmed intraoperatively.
Why it matters:
A traumatic arthrotomy occurs when a soft tissue injury penetrates into the joint capsule. It is important to have a high level of suspicion for this type of injury in anyone with a laceration over a joint, no matter the size, as missing this diagnosis can lead to the development of septic arthritis.
Diagnosis can be made in several ways. Using local anesthetic, the wound can be probed for intra-articular communication. Alternatively, an x-ray will sometimes demonstrate free air in the joint space. When physical exam and radiographs are equivocal, a saline load test can be performed at bedside. This procedure involves performing an arthrocentesis, depositing sterile normal saline into the joint, and observing for extravasation of the fluid through the open wound. If normal saline comes out of the wound, then the test is considered positive and there is likely joint involvement. There is a lot of discussion over the reliability of this test and the appropriate amount of normal saline that should be used (standard is 60 ml) (1). CT without contrast (using 2 mm slices) has been found to be a more sensitive than the saline load test and is less invasive for the patient. And in one study of 62 patients, the sensitivity and specificity of intra-articular air on CT scan was 100% (2). However, a case report similar to our case has been published that did not demonstrate intra-articular air on CT in a patient that had traumatic arthrotomy of the elbow (3).
In the end, the gold standard for determining the presence of a traumatic arthrotomy is through surgical exploration, so early orthopedic consult is recommended if there is any doubt.
Written by:
Dr. Adrian Robles, MD
Emergency Medicine, PGY-2
Cook County Health
Reviewed by:
Dr. Scott Sherman, MD
Associate Program Director
Cook County Health
References:
1. Browning, B. B., Ventimiglia, A. V., Dixit, A., Illical, E., Urban, W. P., & Jauregui, J. J. (2016). Does the saline load test still have a role in the orthopaedic world? A systematic review of the literature. Acta Orthopaedica Et Traumatologica Turcica, 50(6), 597–600.
2. Konda, S. R., Davidovitch, R. I., & Egol, K. A. (2013). Computed tomography scan to detect traumatic arthrotomies and identify periarticular wounds not requiring surgical intervention: an improvement over the saline load test. Journal of Orthopaedic Trauma, 27(9), 498–504.
3. Bunyasaranand JC, Foeger NC, Ryan PM. (2017). Traumatic elbow arthrotomy after motorcycle accident not evident on CT. BMJ Case Rep, Sept 27.