Computed Tomographic Trochlear Depth Measurement in Normal Dogs

Abstract

Objectives The main purpose of this study was to describe the relationship between patellar maximal craniocaudal thickness and femoral trochlear groove depth in normal dogs and to valuate the intra-observer or inter-observer variability of maximal trochlear depth and maximal patellar craniocaudal thickness using computed tomography. Methods Trochlear groove depth and patellar maximal craniocaudal thickness of 40 limbs (20 dogs) were measured by three independent veterinarians using three-dimensional multiplanar reconstruction computed tomography images. The patellar maximal craniocaudal thickness/trochlear depth ratio was determined. Results The mean ratio of these stifles was 0.46 (range 0.24–0.70), meaning that the mean maximal depth of the trochlea was 46% of the mean maximal-patellar thickness. Clinical Significance A wide range of maximal–patellar–craniocaudal–thickness/maximal trochlear-depth ratio was found suggesting that breed studies should be performed to determine a breed-specific patellar-thickness/trochlear-depth ratio. To make decisions on when and where to perform a sulcoplasty during patellar luxation surgery, patella/trochlea thickness relationship should be measured for each breed with patellar tracking from stifle hyperflexion to stifle hyperextension.

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

“…In this study, we opted for CT rather than radiographs, since a CT standardized methodology to accurately perform measurements on the femoral trochlear groove has been established. 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.…”

“…In veterinary medicine, this projection has been described to evaluate the FTGD, 8,31 but it is not routinely used. In this study, we opted for CT rather than radiographs, since a CT standardized methodology to accurately perform measurements on the femoral trochlear groove has been established 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 three‐dimensional complexity of the trochlea morphology, which changes in proximodistal direction 7,14,15 …”

“…Computed tomography has lately shown a better measurement consistency for FTGD in terms of inter‐and intra‐rater agreement 11,12 . Specifically, a recent CT‐study introduced a standardized protocol for measuring the FTGD in five trochlear points equally distributed along trochlear sagittal length 11 .…”

“…7 Traditionally, the FTGD has been assessed intraoperatively by subjective visual inspection to evaluate whether the femoral groove requires a trochleoplasty to provide a deeper accommodation for the patella. 1 Radiographs, 8 ultrasound, 9,10 and computed tomographic (CT) [11][12][13] examinations were described for measuring the FTGD preoperatively. Radiographs are rarely reported in dogs to evaluate the FTGD, and neither inter-and interrater agreement nor accuracy were evaluated.…”

“…9 Computed tomography has lately shown a better measurement consistency for FTGD in terms of inter-and intra-rater agreement. 11,12 Specifically, a recent CT-study introduced a standardized protocol for measuring the FTGD in five trochlear points equally distributed along trochlear sagittal length. 11 In this study, the deepest FTGD was found in the proximal trochlear half, specifically in-between the 25% (point P25) and 50% (point P50) of the trochlear sagittal length.…”