Internal and External Validity of THIRD Test for Hip Labral Tears

Abstract

BackgroundThe Hip Internal Rotation with Distraction (THIRD) physical examination technique is both sensitive and specific to determine hip labral tears. The THIRD test has shown better sensitivity and specificity than magnetic resonance angiography (MRA) when compared with arthroscopy and a negative predictive value that is 15 times higher than MRA. The aim of this study was to evaluate the noninvasive physical examination technique for internal and external validity, agreement with arthroscopy, and predictive value. MethodsCertified athletic trainers from 3 settings were extensively trained and validated. The athletic trainers then maintained a record of subjects with positive THIRD tests. The athletes shared their MRA study and operative report with the principal investigator. Agreement between the THIRD test and MRA to arthroscopic findings was compared, calculations of false-positive rates were performed, and internal and external reliability were evaluated. ResultsOf the 43 subjects enrolled, all subjects with reported positive THIRD test results also showed positive arthroscopic findings of a hip labral tear. MRA was negative in 4 of the 43 cases. Both internal and external validity were shown. The false rate for THIRD was 0% compared with MRA, which was 9%; this difference was statistically significantly (P = .014).