Objective The aim of this study was to evaluate the bone deformities of the distal femur of Toy Poodles with medial patellar luxation (MPL) using computed tomography.

Methods Computed tomography data from 37 stifles of Toy Poodles (16 normal, 10 grade 2 MPL and 11 grade 4 MPL) were analysed. For trochlear morphology, sulcus angle, medial or lateral trochlear inclination and trochlear angle were compared. For condylar morphology, distance between the apex of the medial or lateral trochlear ridge and the most caudal point of the medial or lateral femoral condyle (MC or LC), the length of the cranial/middle (anterior) part (MC(a) or LC(a')) and caudal (posterior) part (MC(p) or LC(p')) of distal femur and medial or lateral condyle width (MCW or LCW) were measured, and the ratios of medial-to-lateral condyles and anterior–posterior parts were compared.

Results Sulcus angle was significantly higher, and medial trochlear inclination was significantly lower in grade 4 MPL group than other groups. Lateral trochlear inclination was not significantly different among 3 groups. Trochlear angles at proximal trochlear groove were significantly lower in grade 4 MPL group than other groups. MC/LC, MC(a)/LC(a'), MC(a)/MC(p), and LC(a')/LC(p') were significantly lower in grade 4 MPL group than other groups; however, there were no significant differences in MC(p)/LC(p') and MCW/LCW among three groups.

Conclusion Hypoplasia of the cranial and middle rather than caudal compartment of the distal femur was the primary morphological abnormality in Toy Poodles with grade 4 MPL.

目的 本研究的目的是使用计算机断层扫描评估具有内侧髌骨脱位（MPL）的玩具贵宾犬股骨远端的骨骼畸形。

方法 分析了 37 只玩具贵宾犬（16 只正常，10 只 2 级 MPL 和 11 只 4 级 MPL）的计算机断层扫描数据。对于滑车形态，比较了滑车沟角、内侧或外侧滑车倾斜度和滑车角。对于髁突形态，内侧或外侧滑车脊的顶点与内侧或外侧股骨髁（MC 或 LC）的最尾点之间的距离，颅骨/中间（前）部分的长度（MC(a) 或测量了股骨远端的 LC(a')) 和尾（后）部分（MC(p) 或 LC(p')）和内侧或外侧髁宽度（MCW 或 LCW），并测量了内侧与外侧的比率髁突和前后部分进行了比较。

结果 4级MPL组脑沟角明显高于其他组，滑车内侧倾角明显低于其他组。3组间滑车侧倾角无显着差异。4级MPL组近端滑车槽滑车角明显低于其他组。4级MPL组的MC/LC、MC(a)/LC(a')、MC(a)/MC(p)和LC(a')/LC(p')显着低于其他组；然而，三组之间的 MC(p)/LC(p') 和 MCW/LCW 没有显着差异。

结论 4 级 MPL 玩具贵宾犬的主要形态异常是股骨远端颅骨和中部而不是尾部的发育不全。