Smith G K
Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104-6010, USA.
J Am Vet Med Assoc. 1997 May 15;210(10):1451-7.
The DI method was developed, at least in part, because of perceived variations among radiologists in regard to subjective hip scores assigned to radiographs. It also was recognized that the prevalence of CHD among many dog breeds was disturbingly high, despite efforts to lower the prevalence using subjective score as a selection criterion. The DI method was developed on the basis of results of mechanical testing of cadaver hip joints, which accomplished 3 principal objectives. First, it showed that when the hip joint is in the standard, hip-extended, internally rotated position, passive laxity is minimized. Second, it showed that passive laxity was maximized when the hip joint is in the neutral position. Third, it demonstrated the sigmoidal nature of the load/displacement curve for the hip joint in the neutral position, which suggested that high repeatability from examiner to examiner in regard to DI could be expected without the need to standardize applied force. The mean and range of DI were shown to vary from 1 breed to the next, but within an individual dog, DI appears to remain constant (within limits of scientific acceptability and clinical applicability) from 16 weeks of age. Passive hip laxity measured on the distraction view is, on average, 2.5 to 11 times greater than that measured on the standard, hip-extended radiographic view. Performance Borzois and Greyhounds, which have an extremely low prevalence of CHD, uniformly have tight hip joints (DI < 0.3), and mean DI for dog breeds that have a high prevalence of CHD is significantly greater than mean DI for Borzois and Greyhounds. However, individual dogs that have DI < 0.3, even though members of breeds prone to CHD, have a low risk of developing DJD. Some, but not all, dogs with DI > 0.3 will develop DJD by 3 years of age, and DI has been shown to be the principal risk factor for development of DJD. Susceptibility to development of DJD appears to be breed-specific. For example, given equivalent DI, German Shepherd Dogs are more at risk for developing DJD than are Rottweilers. Heritability of DI is higher than that of the subjective hip score; thus, selection pressure based on DI should result in faster genetic change than selection pressure based on subjective hip scores. Finally, the DI method has been performed on approximately 14,000 dogs, some of which were evaluated multiple times. It is apparent that this method is no more harmful than the standard, hip-extended radiographic method or palpation performed as part of a routine orthopedic examination.
开发 DI 方法至少部分原因是察觉到放射科医生在给 X 光片分配主观髋关节评分方面存在差异。人们还认识到，尽管努力将主观评分用作选择标准以降低患病率，但许多犬种中髋关节发育不良（CHD）的患病率高得令人不安。DI 方法是基于对尸体髋关节进行机械测试的结果开发的，该测试实现了 3 个主要目标。首先，它表明当髋关节处于标准的、髋关节伸展且内旋的位置时，被动松弛度最小。其次，它表明当髋关节处于中立位置时，被动松弛度最大。第三，它证明了中立位置髋关节的载荷/位移曲线呈 S 形，这表明无需标准化施加的力，不同检查者之间 DI 的重复性就很高。DI 的平均值和范围因品种而异，但在个体犬中，从 16 周龄起，DI 似乎保持恒定（在科学可接受性和临床适用性范围内）。在牵引视图上测量的被动髋关节松弛度平均比在标准的髋关节伸展 X 光视图上测量的大 2.5 至 11 倍。性能 患有 CHD 的患病率极低的灵缇犬和波索尔犬的髋关节均一致很紧（DI < 0.3），而 CHD 患病率高的犬种的平均 DI 明显高于灵缇犬和波索尔犬的平均 DI。然而，即使是易患 CHD 品种的个体犬，DI < 0.3 时患退行性关节病（DJD）的风险也很低。一些（但不是全部）DI > 0.3 的犬在 3 岁时会患上 DJD，并且 DI 已被证明是 DJD 发生的主要风险因素。DJD 发生的易感性似乎具有品种特异性。例如，在 DI 相同的情况下，德国牧羊犬比罗威纳犬患 DJD 的风险更高。DI 的遗传力高于主观髋关节评分；因此，基于 DI 的选择压力应比基于主观髋关节评分的选择压力导致更快的基因变化。最后，已对约 14,000 只犬进行了 DI 方法检测，其中一些犬接受了多次评估。显然，这种方法并不比标准的髋关节伸展 X 光方法或作为常规骨科检查一部分进行的触诊更有害。
