Radiographic measurement of cranial tibial translation using a simple device in dogs

This study was designed to objectively quantify in vivo the cranial tibial translation in order to assess the integrity of cranial cruciate ligament (CrCL) in dogs. The hypothesis of this study was that changes in CrCL integrity would result in detectable changes in tibial translation. To carry out a validation of the translator device, data from injured stifles (PA, n=20), contralateral stifles (CO, n=20) and healthy stifles (HE, n=20) were compared estimating sensitivity, specificity, positive and negative predictive values, and accuracy of the diagnostic test. Medio-lateral radiographic projections were obtained in each stifle, before and during standard thrust force application (49 N, horizontal plane, cranial direction) to measure the absolute tibial translation (ΔS). ΔS was normalized (ΔN) to tibial width to get data regardless of dog’s size. A large discrepancy in ΔN values between HE (13.28±4.60, range 5.9-19.0) and PA (49.75±13.35, range 31.25-66.67) was observed. CO showed intermediate level of ΔN (20.62±8.00, range 8.57-38.78). Comparing PA with clinically healthy stifles (HE and CO), at the ΔN cut-off value (31.25%), a diagnosis of CrCL rupture could be issued with very high probability (95%). Comparing HE with CL, at the ΔN cut-off value (13.79%), although both not pathological, it was possible to obtain moderate levels of sensitivity, specificity, positive and negative predictive value, and accuracy. The translator device could be considered a useful tool to objectively quantify, in vivo, the cranial tibial translation in dogs. It could be used in case of CrCL rupture before surgery and during post-operatory follow-up.