Abstract
Introduction
Clinical examination for stability in knee replacement involves the anterior drawer test. This test has been used to help in the diagnosis of flexion instability when used at 90 degrees and midflexion instability at 30 degrees. We sought to determine the inter-rater reliability of this test when compared to motion capture data.
Methods
10 subjects with previous knee repalcement were examined by four orthopedics knee repalcement surgeons in one setting. Each surgeon evaluated each subject in random order and was blinded from the results of the other surgeons. Each surgeon performed an anterior drawer test at 30 and 90 degrees and graded the instability as 0–5mm, 5–10mm or >10 mm. Anterior posterior translation was measured using motion capture.
Results
At 30 degrees, the agreement between AP subjective rater score and measured AP laxity was poor for 3 of the 4 raters (Κ for observer A,B,C,D: 0.00, 0.0256, 0.5263, 0.3103). At 90 degrees, the agreement was also poor for 3 of the 4 raters (Κ for observer A,B,C,D: 0.0843, 0.6552, 0.2187, 0.0385). Inter-rater reliability was poor at 30 degrees for both the subjective rater score (Κ = 0.21, SE = 0.12, p = 0.0337) and the measured AP laxity (Κ=0.18, SE=0.1, p=0.0427). Inter-rater reliability was also poor at 90 degrees for both the subjective rater score (Κ = 0.04, SE = 0.10, p = 0.3568) and the measured AP laxity (Κ = 0.05, SE = 0.09, p = 0.2906).
Conclusion
The anterior drawer test has poor inter rater reliability at both 30 and 90 degrees. It is unclear if this is from differences in technique of the examiners or form differences in pain or quadriceps function of the subjects. Instability should not be diagnosed strictly by this test and should involve a complete clinical picture of the patient.
