| Canine patellar luxation is a disease in which the patella comes out of the trochlear groove due to genetic or traumatic factors.It is also one of the most common hind limb diseases in small animal clinics.According to the position of patellar prolapse,it can be divided into medial luxation and lateral luxation.Medial luxation is more common than lateral luxation,especially in small dogs.At present,the diagnosis of canine patellar luxation mainly relies on clinical symptoms and general clinical examinations.It has a comprehensive clinical grading standard,but lacks a imaging diagnosis grading method,which makes it impossible to realize risk assessment and early diagnosis.In order to fill the gaps in the imaging diagnosis method of c PL and better understand the regularity of it,this study focused on healthy and MPL small dogs from an animal hospital in Wuhan from December 2019 to March 2021.We performed cone-beam CT scans on the dog’s knee joints,and statistically analyzed the patellofemoral joint CT parameters(trochlear parameters,patellofemoral anatomical parameters,and patellofemoral force line parameters)of dogs that met the inclusion criteria with independent sample t test to discuss the value of these parameters in the diagnosis.Then we draw the ROC curve of the tested dog,calculate the critical value of the relevant parameter according to its Youden index,and analyze the accuracy of the diagnosis index.According to the clinical grading standard,the dogs with patellar luxation are divided into groups.We used a simple correlation analysis method to assess the correlation between each CT parameter and the grade of patellar luxation,and finally determined the difference and range of each CT parameter in different patellar luxation groups through single-factor analysis of variance.1.Based on the analysis of cone beam CT scan images of the knee joint of 73 healthy small dogs and 78 small dogs with medial patellar luxation from December 2019 to March 2021,this study found: In the trochlear parameters,the trochlear groove angle is extremely different between the healthy control group and the patellar luxation group(p<0.01).The trochlear groove angle range of healthy dogs is 130.73°±4.60°.When the trochlear groove angle>138.82°,its Youden index is the largest.At this time,the area under the ROC curve of the trochlear groove angle for the diagnosis of patellar luxation is0.914,the specificity is 100%,and the sensitivity is 74.1%.The lateral trochlear groove tilting angle is significantly different(p<0.01)between the healthy control group and the patellar luxation group,the range of healthy dogs is 23.58°±2.98°.When the lateral trochlear groove tilting angle is less than 19.30°,the Youden index is the largest.At this time,the area under the ROC curve is 0.869,the specificity is 74.1%,and the sensitivity is 100%.The trochlear groove depth/the width of the trochlear ridge is significantly different between the healthy control group and the patellar luxation group(p<0.01),and the range of healthy group is 0.220±0.026.When the trochlear groove depth/the trochlear ridge width is less than 0.233,the Youden index is the largest.At this time,the area under the ROC curve is 0.686,the specificity is 92.6%,the sensitivity is 48.1%.Among the anatomical parameters of the patella,the thickness of the patella is significantly different between the healthy control group and the patellar luxation group(p<0.05).The thickness of the patella of healthy dogs is 5.09mm±0.93 mm.When the thickness of the patella is larger than 6.15 mm,the Youden index is the largest.At this time,the area under the ROC curve is 0.653,the specificity is 92.6%,and the sensitivity is 40.7%.Among the patella-femoral force line parameters,the patella tilting angle is significantly different between the healthy control group and the patellar luxation group(p<0.01).The patella tilting angle range of healthy dogs is 6.92°±0.85°.When the patella tilting angle is larger than 8.02°,The Youden index has the biggest numerical value.Meanwhile,the AUC is0.880,the specificity is 88.9%,and the sensitivity is 74.1%.The laurin angle is significantly different between the healthy control group and the patellar luxation group(p<0.01).The range of the Laurin angle of healthy dogs is 23.16°±2.59°.When the laurin angle is larger than 27.30°,the Youden index is the largest.At this time,the area under the ROC curve is 0.955,the specificity is 88.9%,and the sensitivity is 92.6%.The patella bisect offset angle between the healthy control group and the patellar luxation group is significantly different(p<0.01).The range of the patella bisect offset angle of healthy dogs is 88.55°±3.59°.When the patella bisect offset angle <85.45°,the Youden index is the largest.At this time,the AUC is 0.925,the diagnostic specificity is 81.5%,and the diagnostic sensitivity is 85.2%.2.According to the clinical grading standard of patellar luxation,78 cases of patellar luxation dogs were divided into 21 degree I cases,20 degree II cases,25 degree III cases and 12 degree IV cases.The correlation between the above parameters and the grade of patellar luxation was analyzed.We spotted that there was a remarkable correlation between the trochlear groove angle and the patellar luxation grades(|r|=0.581>0.5),a weak correlation between the trochlear groove depth/the width of the trochlear ridge and the patellar luxation grades(|r|=0.374>0.3),a weak correlation between the patella tilting angle and the patellar luxation grades(|r|=0.347>0.3),a significant correlation between the laurin angle and the patellar luxation grades(|r|=0.735>0.5),a strong correlation between the patella bisect offset angle and the patellar luxation grades(|r|=0.908>0.8).There is no correlation between other patellofemoral parameters and the grade of patellar luxation.The above parameters are subjected to a one-way analysis of variance between different grades of patellar luxation group,and it is found that the trochlear groove angle is significantly different between the different grades of patellar luxation groups(P<0.01),and as the grade of patellar luxation increases,the trochlear groove angle gradually increases.The laurin angle is significantly different between the different grades of patellar luxation groups(P<0.01),and as the grade of patellar luxation increases,the laurin angle gradually increases.The patella bisect offset angle was significantly different between different grades of patellar luxation groups(P<0.01),and as the grade of patellar luxation increases,the patella bisect offset angle shows a gradually decreasing trend.Conclusion:1.The trochlear groove angle,lateral trochlear groove tilting angle,trochlear groove depth/ trochlear ridge width,patella thickness,laurin angle,patella bisect offset angle and patella tilting angle are good indicators for diagnosing medial patellar luxation in small dogs.2.The trochlear groove angle,the laurin angle and the patella bisect offset angle are best indicators for the graded diagnosis of medial patellar luxation in small dogs.In healthy small dogs and small dogs with different grades of medial patellar luxation,the range of the trochlear groove angle is 130.91°±5.60°,134.72°±2.83°,136.66°±1.60°,140.35°±1.17° and 145.82°±1.35°,the range of lateral patella angle is 23.14°±3.46°,16.95°±1.99°,18.40°±1.49°,19.20°±0.84° and 21.37°±1.26°,the range of patella bisect offset angle is 89.22°±4.74°,85.09°±1.23°,82.36°±1.64°,78.65°±1.98° and 76.30°±1.27°. |
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