Objective This study aimed to analyse the distribution of the laxity indices (LI) in a dog population, to compare the LI with the Fédération Cynologique Internationale (FCI) grades and to search for differences of LI between breeds.

Study Design The database was composed of all dogs presented to the University Hospital of the Faculty of Veterinary Medicine in Ghent for obligatory hip screening between January 2016 and February 2019, and all patients presented to orthopaedic consultation between January 2017 and January 2019 for a complaint of hindlimb lameness, which underwent both a standard extended ventrodorsal radiograph of the hips and a stress radiograph revealing hip joint laxity. The latter was obtained by means of the Vezzoni-modified Badertscher distension device and the LI was calculated. For each dog of the population, the LI was then compared with the FCI grade.

Results The LI values ranged between 0.15 and 1.04, with a mean of 0.46. The LI and the FCI grade increased together, and showed a moderate-to-good correlation. There was a highly significant overall difference in the mean value of LI per FCI grade group (p < 0.001). The mean LI of the Labrador Retrievers was slightly but significantly lower than the mean LI of the Golden Retrievers (p < 0.01).

Conclusion The LI calculated on a stress radiograph taken with the Vezzoni-modified Badertscher distension device shows a good correlation with the FCI grade assigned on a standard extended ventrodorsal projection. A wide range of passive hip joint laxity exists in dogs considered to be phenotypically normal based on the FCI grading method.

目的 本研究旨在分析犬群松弛指数 (LI) 的分布，将 LI 与 Fédération Cynologique Internationale (FCI) 等级进行比较，并寻找不同品种之间 LI 的差异。

研究设计 该数据库由 2016 年 1 月至 2019 年 2 月期间在根特大学兽医学院医院进行强制性髋关节筛查的所有狗组成，所有患者在 2017 年 1 月至 2019 年 1 月期间接受骨科咨询，投诉后肢跛行，经过标准的髋部扩展腹背侧 X 光片和显示髋关节松弛的应力 X 光片。后者是通过 Vezzoni 改进的 Badertscher 扩张装置获得的，并计算了 LI。对于种群中的每只狗，然后将 LI 与 FCI 等级进行比较。

结果 LI 值介于 0.15 和 1.04 之间，平均值为 0.46。LI 和 FCI 等级一起增加，并显示出中等至良好的相关性。每个 FCI 等级组的 LI 平均值存在非常显着的总体差异 ( p  < 0.001)。拉布拉多犬的平均 LI 略低于金毛猎犬的平均 LI（p  < 0.01），但显着降低。

结论 在使用 Vezzoni 改良的 Badertscher 扩张装置拍摄的应力 X 光片上计算出的 LI 与标准扩展腹背投影上指定的 FCI 等级具有良好的相关性。根据 FCI 分级方法，被认为表型正常的狗存在范围广泛的被动髋关节松弛。