To determine whether methylene blue dye significantly improves the sensitivity of the saline load test for detection of a traumatic arthrotomy of the knee.
Orthopaedic department, tertiary care medical center.
Subjects scheduled for elective outpatient knee arthroscopy were prospectively enrolled and randomized to a normal saline group or a methylene blue group. A total of 58 subjects were enrolled (methylene blue 29, normal saline 29).
In the course of routine elective knee arthroscopy, a standard inferior lateral arthrotomy was created and then normal saline or methylene blue solution was injected while observing for fluid outflow from the arthrotomy site.
Main Outcome Measurements:
The volume of fluid injected at the time of outflow was recorded with 180 mL set as the maximum injection volume.
The false-negative rate was 67% (methylene blue 69%, normal saline 66%). In patients with a positive test, mean volume of injected fluid at outflow was 105 mL in the methylene blue group and 95 mL in the normal saline group (P = 0.61).
The sensitivity of the saline load test is unacceptably low. The addition of methylene blue does not improve the diagnostic value of the saline load test. Therefore, these results indicate that the saline load test, regardless of the inclusion of methylene blue, is not an accurate test for diagnosing small traumatic knee arthrotomies.
Level of Evidence:
Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.