Review Question - QID 260

Injection of 175ml of saline will diagnose 99% of knee arthrotomies.

Clinical evaluation alone to determine if a periarticular laceration has penetrated the joint can often be incorrect. A Saline Load Test (SLT) is an effective methods to detect intraarticular penetration. New studies have shown addition of methylene blue does not improve the diagnostic value of the saline load test. The use of a CT scan can be helpful, especially in the presence of intra-articular air.

Voit et al. investigated the sensitivity of the clinical exam and a saline load test in 50 consecutive patients with periarticular lacerations suggestive of joint penetration. In 14 there was leakage of fluid on saline load test. In six of these patients, the clinician had judged there was no traumatic arthrotomy based on physical exam and clinical history. They therefore concluded performing a saline load test is important adjunct and the clinical exam alone can not be relied on to detect traumatic arthrotomies.

Nord et al. found that the volumes of saline that were needed in order to effectively diagnose 75%, 90%, 95%, and 99% of the knee arthrotomies were 110, 145, 155, and 175 mL, respectively. They also found that an inferomedial injection location required significantly less fluid than a superomedial injection location did.

Metzger et al. studied 58 patients that underwent saline load test with about 100ml of saline injected (methylene blue 29, normal saline 29). They found that the false-negative rate was 67% (methylene blue 69%, normal saline 66%). They concluded the addition of methylene blue does not improve the diagnostic value of the saline load test.

Konda et al. performed a study evaluationg the role of CT scan versus saline load test. They found that the sensitivity and specificity of the CT scan to detect traumatic arthrotomy was 100%. In a subgroup of 37 patients that received both a CT scan and the conventional saline load test, the sensitivity and specificity of the CT scan was 100% compared to 92% for the saline load test (p<0.001).

Incorrect Answers:
Answer 1: Addition of methylene blue to the saline load test does not increase the sensitivity of the test. (Metzger et al.)
Answer 2: Injection of 110ml of saline will diagnose 75% of knee arthrotomies. (Voit et al.)
Answer 4: A inferoeromedial injection location requires significantly less fluid than a superomedial injection location (Nord et al.)
Answer 5: Physical exam performs worse than the conventional saline load test to detect traumatic knee arthrotomies