Standard radiographs are unreliable for detecting mild tibial torsion following tibial plateau leveling osteotomy in dogs.

OBJECTIVE

To evaluate the diagnostic accuracy of standard postoperative radiographs for identifying mild tibial torsional malalignment (≤ 10°) following tibial plateau leveling osteotomy (TPLO) in dogs.

METHODS

Cadaveric hind limbs from medium- to large-breed dogs without radiographic evidence of stifle pathology were used in this ex vivo experimental study. Each limb underwent TPLO, and a custom 3-D-printed guide was used to induce tibial torsion at 0°, 5°, and 10° in internal and external directions. For each condition, mediolateral and caudocranial postoperative radiographs were obtained. Osteotomy lines and guide pins were digitally masked. Three board-certified small animal surgeons independently reviewed each set to assess the presence, direction, and degree of torsion.

RESULTS

7 hind limbs were used, with 5 sets of radiographs per limb and 35 total sets. Correct identification rates were low when both direction and magnitude were considered. Two surgeons correctly classified 3 of 7 limbs without torsion, and 1 surgeon classified 4 of 7 limbs. Only 1 surgeon correctly classified 3 of 7 limbs with 5° internal torsion; for all other conditions, no surgeon correctly classified more than 2 of 7 limbs. When only direction was considered, internal torsion was correctly identified in 2, 4, and 5 of 14 radiographic sets, and external torsion was correctly identified in 3, 3, and 0 of 14 sets.

CONCLUSIONS

Torsional malalignment of up to 10° following TPLO is challenging to detect radiographically, indicating plain radiographs are unreliable for assessing torsional alignment.

CLINICAL RELEVANCE: Standard orthogonal radiographs are not reliable for assessing mild torsional malalignment after TPLO.