Evaluation of the Norberg Angle Threshold: A Comparison of Norberg Angle and Distraction Index as Measures of Coxofemoral Degenerative Joint Disease Susceptibility in Seven Breeds of Dogs

The Role of Femoral Head Size and Femoral Head Coverage in Dogs with and without Hip Dysplasia

The subject of hip dysplasia in dogs is still current and preoccupies both animal owners and veterinarians. Major factors affecting the development of the disorder are hip laxity and incongruent joints. Many studies on etiology, pathogenesis, and early diagnosis have been performed to reduce prevalence and select healthy dogs for breeding. The purpose of the present study was to investigate a possible relationship between dysplasia and femoral head area (FHA), femoral coverage by the acetabulum (CFH) and cranio-caudal distance of the dorsal acetabular rim (CrCdAR). Radiographs of a total of 264 skeletally mature dogs with similar physical characteristics (German wirehaired pointers (GWP), German shepherd dogs (GSD) and Labrador retrievers (LAB)) presented for routine hip dysplasia screening were recruited for the study. FHA, CFH and CrCdAR were measured and related to dysplasia status. Evaluations of FHA (p = 0.011), CFH (p < 0.001) and CrCdAR length (p = 0.003) measurements revealed significant interactions between breed, sex and FCI scores, so they had to be assessed separately. The results revealed that FHA tends to decrease as the hip dysplasia score worsens. There was no significant relationship between FHA and dysplasia assessment. FHA is breed-specific and is larger in normal and near-normal male (p = 0.001, p = 0.020) and female (p = 0.001, p = 0.013) GWP compared to GSD, respectively. FHA is greater in normal male GWP (p = 0.011) and GSD (p = 0.040) compared to females. There was a significant and strong positive correlation between FHA and CrCdAR in all breeds and sexes. Additionally, FCI scoring had a medium (GWP, GSD) to strong (LAB) negative correlation with CFH.

Joint laxity in canine hip dysplasia assessed using the hip flexed not distracted ventrodorsal view

OBJECTIVES

The ventrodorsal hip extended standard view is conventionally used for radiographic screening of canine hip dysplasia. However, because the ventrodorsal hip extended standard view minimises hip joint laxity, several alternative views have been proposed. Our aim was to evaluate a new ventrodorsal hip flexed and not distracted view to assess joint laxity, by comparing it with the ventrodorsal hip extended standard and ventrodorsal hip flexed and distracted views.

MATERIALS AND METHODS

Between April 2013 and March 2017, all dogs referred to the University of Naples "Federico II" for the diagnosis of canine hip dysplasia were studied using the ventrodorsal hip extended standard, ventrodorsal hip flexed and not distracted and ventrodorsal hip flexed and distracted views. The Norberg angle and the laxity index were measured for each view.

RESULTS

Overall, 102 dogs, 67 males and 35 females, mean age 15 months, were included. The mean (±standard deviation) Norberg angles were 99.77° (±10.42°), 89.29° (±14.32°) and 91.80° (±13.50°) for the ventrodorsal hip extended standard, ventrodorsal hip flexed and not distracted and ventrodorsal hip flexed and distracted views, respectively. The mean (± standard deviation) laxity indices were 0.19 (± 0.14), 0.39 (± 0.25) and 0.36 (± 0.21), respectively. The ventrodorsal hip flexed and distracted and ventrodorsal hip flexed and not distracted views had lower Norberg angle and higher laxity index values compared with the ventrodorsal hip extended standard view. The ventrodorsal hip flexed and distracted and ventrodorsal hip extended standard views are in strong agreement for the measurement of both Norberg angle and laxity index, as confirmed by Bland-Altman analysis and the intraclass correlation coefficient.

CLINICAL SIGNIFICANCE

The ventrodorsal hip flexed and distracted and ventrodorsal hip flexed and not distracted views obtained with the hip in a neutral position reveal joint laxity better than the ventrodorsal hip extended standard view. Unlike the ventrodorsal hip flexed and distracted view, the ventrodorsal hip flexed and not distracted view does not require human operators or special devices for positioning the dog. The wide age range of the dogs enrolled might have influenced the laxity index measurements, since capsular fibrosis in older dogs reduces laxity.

Assessment of the medium- to long-term radiographically confirmed outcome for juvenile dogs with hip dysplasia treated with double pelvic osteotomy

OBJECTIVE

To assess the medium- to long-term radiographically confirmed outcomes in juvenile dogs with hip dysplasia (HD) that did and did not undergo double pelvic osteotomy (DPO).

STUDY DESIGN

Retrospective case-controlled.

ANIMALS

Twenty-six dogs with HD that were candidates for DPO; 22 dogs underwent DPO (16 bilateral, six unilateral); four dogs did not.

METHODS

Initial and follow-up radiographs of DPO candidates (2011-2017) that did and did not undergo surgery were reviewed, and the British Veterinary Association and Kennel Club Hip Dysplasia Scheme score (BVA-HD), osteoarthritis score (OAS) and laxity index score (LI) were determined. Baseline and follow-up BVA-HD, OAS, and change in radiographically confirmed scores were compared by using analysis of variance for correlated samples.

RESULTS

There was no significant difference in BVA-HD or OAS between surgically treated and nonsurgically treated cohorts at baseline. Follow-up radiographs (median, 49 months) revealed that most (34/38) hips had a BVA-HD ≤10 after DPO, while four of eight hips from the nonsurgical cohort had BVA-HD >10. Follow-up BVA-HD and OAS were lower in hips after surgery (BVA-HD median 2.15, interquartile range [Q1-Q3] 1.3-4.1; OAS median 1.9, Q1-Q3 1.1-4.1) compared with the nonsurgically treated cohort (BVA-HD median 11.4, Q1-Q3 8.1-17.5, P < .01; OAS median 7.0, Q1-Q3 5.1-13.4, P < .01). Seven hips with an LI >1 had no radiographically confirmed progression of osteoarthritis after DPO.

CONCLUSION

Double pelvic osteotomy prevented radiographically confirmed progression of osteoarthritis in the medium- to long-term. Laxity index score > 1 was not a contraindication for DPO in this study.

CLINICAL SIGNIFICANCE

Double pelvic osteotomy prevents progression of radiographically confirmed features of osteoarthritis in juvenile dogs with HD.

Combining canine mesenchymal stromal cells and hyaluronic acid for cartilage repair

Cell therapy and tissue engineering have been intensively researched for repair of articular cartilage. In this study, we investigated the chondrogenic potential of canine adipose-derived mesenchymal stromal cells (ASCs) combined to high molecular weight hyaluronic acid (HA) in vitro, and their therapeutic effect in dogs with chronic osteoarthritis (OA) associated with bilateral hip dysplasia. Canine ASCs were characterized after conventional 2D culture or 3D culture in HA, showing adequate immunophenotype, proliferation and trilineage differentiation, as well as chondrogenesis after cultivation in HA. ASC/HA constructs were used to treat 12 dogs with OA, sequentially assigned to control, ASC and ASC/HA groups. Animals were examined for clinical, orthopedic and radiological parameters. Lameness at walk and pain on manipulation were reduced in the ASC group and mainly in the ASC/HA group. Range of motion and detection of crepitus on hip rotation and abduction improved similarly in all groups. For articular edema, muscle atrophy, Norberg angle values and radiographic analyses, there were no variations throughout the period. These results indicate that ASC/HA constructs are safe and may be an effective therapeutic tool in treating canine chronic osteoarthritis, which should be confirmed with larger studies and additional clinical parameters.

Evaluation of Radiographic Coxofemoral Measurements in Boerboel Dogs

This study compares the coxofemoral parameters used for the detection of hip dysplasia in humans with Norberg angles in Boerboel dogs. Twenty adult Boerboel dogs of both sexes (mean weight: 54.0 ± 7.54 kg) were used. They were premedicated with Xylazine (0.5 mg.kg−1) and induced with a propofol (4 mg.kg−1) injection. Extended antero-posterior radiographs of the hip were obtained with a digital X-ray machine. Linear Femoral Overlap (LFO), Norberg Angle (NA), Sourcil Sector Angle (SSA), Center Edge Angle (CEA) and Acetabular Index Angle (AIA) were determined. The inter- and intra-observer variability were calculated from inter- and intra- class correlation coefficient using the analysis of variance (ANOVA). Fischer’s exact test was used to define the statistically significant difference in measurements between sexes and hip dysplasia status. A significant difference was set at P < 0.05. The intra-observer agreement was high for NA and CEA, moderate for AIA, but low for SSA and LFO, while inter-observer agreement was high for NA and CEA, moderate for LFO and AIA, but very low for SSA. There was no significant (P < 0.05) difference in the measured parameters between male and female Boerboels, however, NA and CEA were significantly (P < 0.05) lower in Boerboels with hip dysplasia than those with normal hips. The CEA does not have advantage over NA for radiographic screening of dogs with hip dysplasia.

Juvenile Pubic Symphysiodesis

In properly selected dogs, juvenile pubic symphysiodesis improves joint congruity, decreases hip laxity, and can reverse or prevent progression of degenerative joint disease in the hips. To be effective, surgery must be done at a young age and in hips that are only mildly to moderately lax. Juvenile pubic symphysiodesis is best viewed more as a preemptive procedure than as a strictly therapeutic one. Dogs considered to be at risk for hip dysplasia should be screened with Ortolani testing at 12 weeks of age, with further imaging and perhaps surgery to follow for those who have a positive Ortolani sign.

Associations between early radiographic and computed tomographic measures and canine hip joint osteoarthritis at maturity

OBJECTIVE

To evaluate associations of measures assessed by radiography, 2-D CT, and 3-D CT of the hip joints of immature dogs with osteoarthritis in the same joints at maturity.

ANIMALS

46 hound-type dogs from a colony predisposed to osteoarthritis.

PROCEDURES

Images of hip joints (1/dog) were obtained at 16, 32, and 104 weeks of age. Radiographic measures included Norberg angle, distraction index, and osteoarthritis score. Two-dimensional CT measures included acetabular index, percentage of femoral head coverage, and center edge, horizontal toit externe, acetabular anteversion, and ventral, dorsal, and horizontal acetabular sector angles. Three-dimensional CT measures were femoral head and neck volume, femoral neck angle, and femoral head and neck radius. Differences among measures at 16 and 32 weeks in dogs with different osteoarthritis scores at later time points, relationships among variables at each time point, and relationships of single and combined measures with the presence of osteoarthritis at 104 weeks were evaluated.

RESULTS

The 16- and 32-week distraction index, center edge angle, dorsal acetabular sector angle, horizontal acetabular sector angle, percentage of femoral head coverage, acetabular index, and Norberg angle and the 32-week femoral neck angle varied significantly with osteoarthritis severity at 104 weeks. Presence of osteoarthritis in mature dogs was most strongly associated with 16-week combined measures of distraction index and center edge angle and 32-week combined measures of dorsal acetabular sector angle and Norberg angle.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in hip joint morphology associated with radiographic signs of osteoarthritis were detectable as early as 16 weeks of age and varied with osteoarthritis severity in adult dogs. The use of combined hip joint measures may improve early identification of dogs predisposed to hip joint osteoarthritis.

EFFECTS OF PELVIC AND FEMORAL POSITIONING ON CANINE NORBERG ANGLE MEASUREMENTS AND TEST–RETEST RELIABILITY: A COMPUTED TOMOGRAPHY-BASED SIMULATION STUDY

Canine hip dysplasia is a common disease in dogs, often diagnosed by using the Norberg angle (NA), an index for the laxity of the hip joint. Measurement of the NA can be affected by the pelvic and femoral positioning during imaging, the effects and test–retest reliability of which have not been documented. To bridge the gap in knowledge, computed tomography data from 11 Labrador Retriever dogs were obtained and used to generate synthetic ventrodorsal radiographs of the hip for NA measurements via a perspective projection model. Twenty-five synthetic radiographs of the hips were generated at positions defined by combinations of five pelvic tilt angles (-20° to 20° at 10° intervals) and five femoral elevation angles (from full extension to 40° at 10° intervals). For each radiograph, the NA was measured three times by each of the two experienced veterinarian examiners. It was found that both the increase in caudal pelvic tilt and femoral elevation increased the measured NA, although the intra- and inter-examiner reliability was very good for a given hip position. The current results suggest that careful positioning of the pelvis and femur during radiographic imaging is critical for accurately measuring the NA, and thus the laxity of the hip, for the clinical diagnosis of hip dysplasia.

Evaluation of the effect of pelvic tilt in the coronal plane on the Norberg angle measured in ventrodorsal radiographic views of a canine hip joint bone model

OBJECTIVE

To determine the effect of pelvic tilt on the Norberg angle (NA) measured in ventrodorsal radiographic views of a hip joint in a canine femoral-pelvic bone model.

SAMPLE POPULATION

Radiographic views of a femoral-pelvic bone model with 1 articulated hip joint (without evident laxity).

PROCEDURES

The bone model was placed on a radiography table. With the joint fully extended, the pelvic coronal plane was tilted from 0° in 5° increments caudally and cranially to a maximum of 30° in each direction (femoral frontal plane was maintained parallel with the radiograph cassette); a digital ventrodorsal radiographic view was obtained at each tilt position. In each image, the NA was measured 3 times by 2 observers (operators). The effect of pelvic tilt on the NA was evaluated by use of a repeated-measures analysis; within-and between-operator variances were also assessed.

RESULTS

Within-operator repeatability was excellent for assessments of hip joint NAs in radiographic views obtained when cranial or caudal tilt was applied to the femoral-pelvic model; replicate measurement variation was < 2.5% (coefficient of variation < 5%). Mean NA values determined by the 2 operators in cranial or caudal tilt views did not differ. Mean between-operator difference in caudal tilt measurements was -0.55° (95% confidence interval, -1.69° to 0.59°) and in cranial tilt measurements was -0.13° (95% confidence interval, -1.33° to 1.06°). Cranial or caudal pelvic tilt did not affect measurement of the NA.

CONCLUSIONS AND CLINICAL RELEVANCE

Model-derived results indicated that pelvic tilt during acquisition of ventrodorsal radiographic views of the hip joints of a dog should not affect measurement of the NA.

Distraction index as a risk factor for osteoarthritis associated with hip dysplasia in four large dog breeds

OBJECTIVE

To determine if age, breed, gender, weight or distraction index (DI) influenced the risk of radiographic osteoarthritis (OA) of canine hip dysplasia (CHD) in four common dog breeds; the American bulldog, Bernese mountain dog, Newfoundland and standard poodle.

MATERIALS AND METHODS

This was a cross sectional prevalence study with 4349 dogs. Canine hips were evaluated using 3 radiographic projections: the hip-extended view, the compression view and the distraction view. The hip-extended view was examined for the presence of OA. The PennHIP distraction view was utilized to calculate the DI. For all breeds, a multiple logistic regression model incorporating age, weight, gender, and DI was created. For each breed, disease-susceptibility curves grouping dogs on the basis of age were constructed. Receiver-operating characteristic (ROC) curves were developed for each breed regardless of age.

RESULTS

For all breeds, DI was the most significant risk factor for the development of OA associated with CHD. Weight and age were also significant risk factors in all four breeds, but gender was not.

CLINICAL SIGNIFICANCE

Results from this study support previous findings, that irrespective of breed, the probability of radiographic OA increases with hip joint laxity as measured by the DI. Breed-specific differences in this relationship, however, warrant investigation of all breeds affected by CHD to determine inherent dependency of hip OA on joint laxity. Such findings guide veterinarians in helping dog breeders to make evidence-based breeding decisions and in informing dog owners to implement preventative treatments for CHD for dogs found to be at risk.

Interobserver agreement in the diagnosis of canine hip dysplasia using the standard ventrodorsal hip-extended radiographic method

OBJECTIVES

To determine the agreement between observers and to investigate the effect of observer experience in diagnosing canine hip dysplasia and providing final scoring of hips using the standard ventrodorsal hip-extended radiographic method. The agreement of the final scoring, with a presumed correct assessment based on the Norberg angle, is also investigated.

METHODS

Thirty observers were requested to read 50 ventrodorsal hip-extended radiographs of 25 dogs according to Federation Cynologique International criteria. Groups of experienced (nine members) and inexperienced (21 members) observers were used.

RESULTS

For providing the distinction between dysplastic versus non-dysplastic dogs, the average interobserver agreement was 72 per cent and was significantly higher (P<0.0001) than the score that could be expected by chance without any agreement between observers. For providing the final score (A, B, C, D or E), an average interobserver agreement of 43.6 per cent was found. In the experienced group, an agreement score of 76 per cent was found for the distinction between AB versus non-AB and an agreement score of 81 per cent was found for the distinction between C versus non-C. The agreement score was significantly higher (P<0.0001) for the experienced group than for the inexperienced group in all cases. Agreement between the presumed correct assessment based on the Norberg angle and the observer's evaluation was low (P=0.35), irrespective of whether the observers were experienced (71.8 per cent correct assessments) or inexperienced (69 per cent correct assessments).

CLINICAL SIGNIFICANCE

Although interobserver agreement is low, observer experience increases agreement.

Influence of borderline hip dysplasia on joint kinematics of clinically sound Belgian Shepherd dogs

OBJECTIVE

To detect changes in joint kinematics of clinically sound dogs with or without radiographically detectable borderline hip dysplasia (HD).

ANIMALS

20 Belgian Shepherd Dogs (Malinois; mean +/- SD age, 2.75 +/- 1.32 years) with no clinical signs of HD.

PROCEDURES

Kinematic gait analysis was performed in Malinois walking on a treadmill. On the basis of results of radiographic examination for HD and in accordance with guidelines established by the Fédération Cynologique Internationale, dogs were assigned to group 1 (no radiographic signs of HD; 8 dogs) or group 2 (borderline HD; 12 dogs). Ground reaction forces and weight distribution among limbs and differences between groups were evaluated. Maximal sagittal angle during the stance and swing phases, the time at which they were detected, and angle velocities were calculated for joints of the hind limbs.

RESULTS

Ground reaction forces revealed no differences between groups. Dogs in group 1 had significant changes (earlier time for maximal flexion of the hip joint and less flexion and less range of motion of the stifle joint), compared with results for dogs in group 2. Maximal angle velocity of the stifle and tarsal joints was significantly lower during the swing phase in group 1 than in group 2.

CONCLUSIONS AND CLINICAL RELEVANCE

This study revealed that dogs with borderline HD had altered joint kinematics. Our data provide basic kinematic values for clinically sound and affected dogs and can be used to investigate the long-term effects for subclinical radiographic changes of the hip joints of dogs.