Intra- and Inter-observer Variability of Measurements of the Laxity Index on Stress Radiographs Performed with the Vezzoni-Modified Badertscher Hip Distension Device

Quantifying the Stress in Stress Radiographs to Determine Sufficient Laxity of the Coxofemoral Joint: A Canine Hip Dysplasia Cadaveric Study

OBJECTIVE

 While it has been known for a long time that laxity in the hip joint is the primary cause of degenerative changes later on in canine hip dysplasia, limited data are available on the fundamental characteristics that define the procedure used to quantify this. The aim of this study was to evaluate the force-laxity relation to assess the repeatability of repeated cycles of stress on the hip joint and determine the force necessary tomeasure a sufficient proportion of laxity present in hip joints.

MATERIALS AND METHODS

 Thirty-four canine cadavers underwent a radiographic protocol including stress radiographs with increasing force using the Vezzoni modified Badertscher distension measuring device (VMBDmD). Three dogs underwent five repeat examinations. The laxity index (LI) and osteoarthritis were scored.

RESULTS AND CONCLUSION

 The curves and the maximal LI (LImax) were not significantly influenced by osteoarthritis, weight, gender, and side. The position of the VMBDmD influenced the curve but not the LImax. The force-laxity curve itself and the LImax were repeatable, which indicated that it did not cause permanent damage to the joint and also confirmed the practicability of the procedure. Ninety percent of hip joints reached sufficient laxity at a force of 95.32 N, which is realistically achievable. Further studies are necessary before extrapolating these results to patients and to further enlighten the biomechanics of stress radiographs.

Development and validation of a device to measure the force applied to the coxofemoral joint during stress radiography for early diagnosis of canine hip dysplasia

Hip dysplasia is a common orthopaedic condition in dogs and stress radiography is the best diagnostic tool for early diagnosis. Objective force guidelines are lacking, leaving room for errors and fraud during screening. Our objective was to develop an accurate and validated measuring device that allows quantification of the applied force in vivo in real-time during stress radiographic imaging. A two-step approach was followed. First, four load cells were incorporated in the original Vezzoni Modified Badertscher Distension Device (VMBDD) and a dedicated computer program was developed. In vitro evaluations of the accuracy demonstrated a trueness of 0.19 N (0.1%FS) and precision of 0.26 N (0.2%FS) for the individual loadcells. The trueness and precision of the assembled VMBDmD were 0.02 N (0.02%FS) and 0.52 N (0.38%FS). Secondly, the modified device was tested on several cadavers. The device was similar in use as the VMBDD, did not interfere with radiographic acquisition, gave the operator real-time feedback, and linked the force with the radiograph. Altogether, we describe the accuracy of the VMBDmD and have evaluated its use in cadavers. We saw that the device successfully quantified and stored the applied force in real-time during stress radiography.

Radiographic Diagnosis of Hip Laxity in Rottweilers: Interobserver Agreement at Eight- and Twelve-Months of Age

Hip laxity is one of the predisposing factors of canine hip dysplasia. The early diagnosis of hip laxity allows veterinarians to prevent the participation of dysplastic dogs in breeding programs, which could lower the disease's prevalence due to its genetic background. Furthermore, it allows them to plan preventive/therapeutic procedures for mild/near-normal hips to reduce the symptoms of the disease at older ages. A reliable screening program must be repeatable and reproducible, and intra- and inter-observer studies can help us to determine the best methods. In this study, we aimed to evaluate the radiographic parameters used for the early diagnosis of hip dysplasia in Rottweilers at 8 and 12 months of age with five observers to assess the interobserver agreements. According to our findings, there were high interobserver agreements at both ages for the quantitative values, such as the center edge angle (CEA), dorsal acetabular rim slope (DARS), distraction index (DI), and Norberg angle (NA), whereas we recorded from poor to moderate agreements for the qualitative values, such as the grading of the dorsal acetabular rim (GDAR), grading of the degenerative joint disease (GDJD), location of the center of the femoral head (LCFH), and sclerosis of the cranial acetabular rim (SCAR).

Acetabular Coverage Area Occupied by the Femoral Head as an Indicator of Hip Congruency

Accurate radiographic screening evaluation is essential in the genetic control of canine HD, however, the qualitative assessment of hip congruency introduces some subjectivity, leading to excessive variability in scoring. The main objective of this work was to validate a method-Hip Congruency Index (HCI)-capable of objectively measuring the relationship between the acetabulum and the femoral head and associating it with the level of congruency proposed by the Fédération Cynologique Internationale (FCI), with the aim of incorporating it into a computer vision model that classifies HD autonomously. A total of 200 dogs (400 hips) were randomly selected for the study. All radiographs were scored in five categories by an experienced examiner according to FCI criteria. Two examiners performed HCI measurements on 25 hip radiographs to study intra- and inter-examiner reliability and agreement. Additionally, each examiner measured HCI on their half of the study sample (100 dogs), and the results were compared between FCI categories. The paired t-test and the intraclass correlation coefficient (ICC) showed no evidence of a systematic bias, and there was excellent reliability between the measurements of the two examiners and examiners’ sessions. Hips that were assigned an FCI grade of A (n = 120), B (n = 157), C (n = 68), D (n = 38) and E (n = 17) had a mean HCI of 0.739 ± 0.044, 0.666 ± 0.052, 0.605 ± 0.055, 0.494 ± 0.070 and 0.374 ± 0.122, respectively (ANOVA, p < 0.01). Therefore, these results show that HCI is a parameter capable of estimating hip congruency and has the potential to enrich conventional HD scoring criteria if incorporated into an artificial intelligence algorithm competent in diagnosing HD.

Imaging diagnosis of canine hip dysplasia with and without human exposure to ionizing radiation

Hip dysplasia (HD) is one of the most common hereditary orthopaedic diseases in dogs, with serious implications for the quality of life of the affected animals. Radiographic screening is essential for the selection of breeding stock in some at-risk breeds, and radiography is also used in the diagnosis of clinical HD cases. A definitive diagnosis of HD is based on radiographic examination, and the most commonly used view is the ventrodorsal hip extended projection, sometimes in combination with various hip stress-based techniques. Radiographic images require high quality positioning and dogs are usually anesthetized and often manually restrained to facilitate optimal positioning. The 'as low as reasonably achievable' (ALARA) principle used in human radioprotection is not always fulfilled in veterinary practice, except in the UK, where human exposure to ionizing radiation in veterinary medicine is strictly regulated. While each dose of ionizing radiation is small, doses accumulate over a lifetime, which can eventually result in substantial radiation exposure. Therefore, manual restraint should be avoided and mechanical immobilization, sedation or general anaesthesia should be used. This review examines the biological effects of human exposure to ionizing radiation and common sources of veterinary exposure. The diagnostic quality of imaging methods for the diagnosis of canine HD is compared between manually restrained and hands-free dog positioning. Hands-free radiographic techniques are available to assess hip laxity, degenerative joint changes and hip osseous structure while preserving image quality, and can be used to select animals for breeding or for the diagnosis of HD.

Analysis of a Laxity Index Database and Comparison with the Fédération Cynologique Internationale Grades of This Population

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.

Canine hip dysplasia screening: Comparison of early evaluation to final grading in 231 dogs with Fédération Cynologique Internationale A and B

OBJECTIVES

This study aimed to verify if a significant difference exists between parameters in the early evaluation of normal and near-normal hip joints, to evaluate the influence of age and breed on the parameters, and to clarify the usefulness of a total score for differentiating between Fédération Cynologique Internationale (FCI) grade A and B hips.

METHODS

A total of 231 dogs were classified according to whether they had FCI A or B hips at adulthood, with measurements obtained at 14-28 weeks of age. The total score was calculated by the summation of the following quantitative parameters: angle of subluxation (AS), angle of reduction (AR), laxity index (LI), and dorsal acetabular rim slope (DARS). Logistic regression analysis was performed to establish the probability of the study population to develop an FCI B hip based on the total score. This was repeated for the highest score in combination with the worst-rated hip and once more for breeds.

RESULTS

No correlation between age and the parameters was found in the cohort, or for FCI A and B. The values of all the parameters were significantly lower in the FCI A group than in the FCI B group (AR: 4.42° ± 6.0° vs 7.62° ± 7.2°; AS: 0.45° ± 1.9° vs 1.55° ± 3.8°; LI: 0.32 ± 0.1 vs 0.36 ± 0.1; DARS: 3.30° ± 1.8° vs 3.77° ± 1.9°; TS: 11.47 ± 8.3 vs 16.65 ± 10.9). Labrador Retrievers and Golden Retrievers showed significant differences between parameters for both FCI grades. The range, where FCI A and B hips can be predicted on the basis of the total score, was different when assessed for the entire cohort, Labrador Retrievers, and Golden Retrievers.

CLINICAL SIGNIFICANCE

Our results show that even in normal and near-normal hips, the parameters significantly differed in the early evaluation. Moreover, cutoff values should be set for different breeds in the prediction of the FCI grade during early evaluation for a better breeding selection regarding canine hip dysplasia, one of the most common orthopedic diseases among large and giant breed dogs.

Comparison of Reliability of Norberg Angle and Distraction Index as Measurements for Hip Laxity in Dogs

OBJECTIVE

 The main purpose of the study was to compare reliability of measurements for the evaluation of hip joint laxity in 59 dogs.

MATERIALS AND METHODS

 Measurement of the distraction index (DI) of the PennHIP method and the Norberg angle (NA) of the Fédération Cynologique Internationale (FCI) scoring scheme as well as scoring according to the FCI scheme and the Swiss scoring scheme were performed by three observers at different level of experience. For each dog, two radiographs were acquired with each method by the same operator to evaluate intraoperator-reliability.

RESULTS

 Intraoperator-reliability was slightly better for the NA compared with the DI with an intraclass correlation coefficient (ICC) of 0.962 and 0.892 respectively. The ICC showed excellent results in intraobserver-reliability and interobserver-reliability for both the NA (ICC 0.975; 0.969) and the DI (ICC 0.986; 0.972). Thus, the NA as well as the DI can be considered as reliable measurements. The FCI scheme and the Swiss scoring scheme provide similar reliability. While the FCI scheme seems to be slightly more reliable in experienced observers (Kappa FCI 0.687; Kappa Swiss 0.681), the Swiss scoring scheme had a noticeable better reliability for the unexperienced observer (Kappa FCI 0.465; Kappa Swiss 0.514).

CLINICAL SIGNIFICANCE

 The Swiss scoring scheme provides a structured guideline for the interpretation of hip radiographs and can thus be recommended to unexperienced observers.