Quantitative evaluation of canine cranial cruciate ligament disease by stress radiography

BACKGROUND To establish a quantitative parameter reflecting displacement of the tibia relative to the femoral condyle in dogs with damage to the cranial cruciate ligament (CrCL).ANIMALS One hundred and forty-eight client-owned dogs with intact (n=34), partial rupture (n=43), or complete rupture (n=93) of the CrCL confirmed by arthroscopy of the stifle joint.PROCEDURES The Cranial Tibial Displacement Index (CTDI) was measured on mediolateral radiographs obtained in lateral recumbency with the tarsal and stifle joints at 90° of flexion. The sensitivity and specificity of the CTDI for assessment of CrCL damage was compared with that of the cranial drawer test, tibial compression test, fat pad sign, and radiographic OA score.RESULTS The mean CTDI (mean ±SD) scores were 0.5±0.1, 0.8±0.2, and 1.2±0.3 in the groups with an intact, partially ruptured, and completely ruptured CrCL, respectively; the differences between the three study groups were statistically significant (p<0.001). The sensitivity, specificity, and positive and negative predictive values of the CTDI for distinguishing damaged and intact CrCLs were 89.0%, 85.3%, 96.0%, and 65.9%, respectively.CONCLUSIONS AND CLINICAL RELEVANCE The CTDI, which quantifies cranial displacement of the tibia, could be an objective indicator reflecting the grade of CrCL damage. CrCL injury could be evaluated indirectly from the CTDI score, which may allow a minimally invasive early diagnosis of a ruptured CrCL.