Computed Tomographic Measurements of the Sulcus Angle of the Femoral Trochlea in Small-Breed Dogs with and without Medial Patellar Luxation

Abstract

Trochleoplasty is often performed in dogs with medial patellar luxation (MPL); however, the current guidelines on when to perform a trochleoplasty in dogs are vague. The sulcus angle (SA) is used to assess the femoral trochlear morphology in humans. The aim of this study is to describe a method to measure the SA and other parameters of trochlea morphology in dogs using computed tomography. First, we searched for a suitable measuring location for the SA. Transverse images of the femurs were obtained as perpendicular planes to the tangent of the femoral trochlea which was 0 to 60 degrees (every 5 degrees) to the anatomical axis of the femur. The deepest point of the femoral trochlea was found in the transverse images perpendicular to the tangent of the femoral trochlea which was at 15 degrees to the anatomical axis of the femur. The SA and the other parameters of femoral trochlea morphology were measured at the deepest point of the femoral trochlea. The SA of the stifle joints with grade 3 and 4 MPL was significantly higher than the SA of stifle joints not affected by MPL. There was no significant difference in the SA between dogs affected by grade 1 and 2 MPL and dogs not affected by MPL. Further studies are needed to establish whether the SA can be used as selection criteria for trochleoplasty.

Computed tomographic measurements of the femoral trochlea in dogs with and without medial patellar luxation

“…4,28 When comparing our results with the radiographic study of Garnoeva, 8 similar data in terms of mean FTGA in SB dogs without MPL were found, as Garnoeva reported a mean FTGA value of 125 . On the contrary, in the CT study of Sasaki and coauthors, 15 a greater FTGA (135 ± 8 ) was found in SB dogs without MPL. We believe that a plausible explanation to such discrepancy relies on the trochlear position where the FTGA measurement was performed.…”

“…We accept our first hypothesis, as in this study the overall FTGA in dogs without MPL was smaller compared to MPL dogs, similarly to what other authors have recently reported. 8,14,15 Among SB and MLB populations, we discovered a mean FTGA of 128 ± 4.7 in SB and 119 ± 5.6 in MLB with cutoff values of 134 and 128 respectively. These data slightly differ from human literature, which suggests that a normal trochlea has an average sulcus angle of 138 ± 6 , while dysplastic trochleae have a sulcus angle >145 .…”

“…In our study, the FTGA was measured in two trochlear points in the proximal half of the trochlea, that did not include the very proximal part of the femoral trochlea. Similarly, Sasaki and colleagues 15 measured the FTGA in the proximal half of the femoral trochlea, but in a more proximal position. Nicetto et al 11 and Yasukawa and coauthors 14 showed that the FTGD is decreased in the very proximal area of the proximal trochlear half.…”

“…11,12 The benefits of the broad availability of radiographs and ease for performing a skyline view of the femoral trochlea are counteracted by the threedimensional complexity of the trochlea morphology, which changes in proximodistal direction. 7,14,15 Moreover, from the authors' perspective, when performing the skyline radiographic projection, it is difficult to select and analyze one specific point of the trochlear groove. As a result, it would be necessary to perform multiple radiographs with a different degree of stifle flexion, although this will probably increase the sedation time and costs.…”

“…To the authors' knowledge, CT was used in two studies to evaluate the FTGD and trochlear ridge orientation using angular measurements in SB. 14,15 A shallower femoral trochlear groove in MPL dogs compared to dogs without MPL, was observed proportionally to the MPL grade. Both studies were performed in small breed (SB) dogs.…”