Examination of Proximodistal Patellar Position in Dogs with the Stifle at Full Extension

Abstract

Objective The aim of this study was to determine the factors related to functional patella alta, with which the proximodistal patellar position exceeds the reference range of healthy small dogs proximally when the stifle is at full extension. Study Design Mediolateral-view radiographs of dogs weighing less than 15 kg were obtained and classified into the medial patellar luxation (MPL) and control groups. The reference range of the proximodistal patellar position was determined from the control group. In both groups, a patellar position exceeding this reference range proximally was considered functional patella alta. Multiple logistic regression analysis was performed to examine the factors related to functional patella alta. A receiver operating characteristic (ROC) curve was made for each factor. Results Overall, radiographs of 127 stifles of 75 dogs were obtained. Eleven stifles in the MPL group and one stifle in the control group were determined to be functional patella alta. The factors associated with functional patella alta included a greater full extension angle of the stifle joint, longer patellar ligament, and shorter femoral trochlear length. The full extension angle of the stifle joint had the biggest area under the ROC curve. Conclusion Mediolateral radiographs of the stifle joint in full extension are clinically important in dogs with MPL because some dogs might have a proximally positioned patella that is recognizable only when the stifles are extended.

Diagnostic value of patellofemoral parameters in small breed dogs with medial patellar luxation: a tangential X-ray study

“…In canine orthopaedics, ROC analysis has been used to evaluate parameters related to developmental diseases, such as hip dysplasia (Gaspar et al, 2016) and medial elbow coronoid disease (Hersh-Boyle et al, 2021). In dogs with patellar luxation, only the cutoff values of femoral trochlear morphological parameters (Longo et al, 2023) and indices of proximodistal patellar position (Murakami et al, 2023) have been reported.…”

“…In human medicine, there are numerous studies on patellofemoral diagnostic imaging parameters, and the use of ROC analysis to outline those that seem most relevant in the diagnosis of patellar instability (Ridley et al, 2016;Prakash et al, 2016;Geraghty et al, 2022;Kim & Parikh, 2022). To date, in dogs, ROC analysis data on sensitivity, specificity, and cut-off values have been reported only for trochlear groove morphometric parameters in small and large breeds (Longo et al, 2023) and proximodistal patellar position indices (Murakami et al, 2023); however, there are no data on parameters of patellar morphology and patellofemoral alignment. This information seems valuable, as lameness affecting the opposite limb might have been missed in cases of bilateral MPL.…”