ABSTRACT
The genetics of patellar luxation (PL) were investigated in Pomeranian dogs presented at the Small Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University. A cohort of 339 Pomeranian dogs, part of a four-generation pedigree of 842 Pomeranians, was screened for PL from 2006 to 2013. PL was present in 77% of the screened dogs, with 84% having bilateral and 16% unilateral luxation. Medial PL was more common (95%) than lateral PL (2%) or bidirectional PL (3%). The risk of PL was similar in male and female dogs (female:male relative risk 1.11, 95% CI 0.98-1.25). The heritability of PL in the screened population was 0.44±0.04 using a threshold model. A genome-wide association study of PL (48 cases and 48 controls) using a high-density SNP array indicated the possible involvement of 15 chromosomal regions, of which CFA05 and CFA32 remained associated in a larger study involving an additional 128 cases and 7 controls. Candidate genes in these regions may be involved in the pathogenesis of PL in Pomeranian dogs.
Subject(s)
Dog Diseases/genetics , Genetic Predisposition to Disease , Genome-Wide Association Study , Patellar Dislocation/veterinary , Animals , Dog Diseases/epidemiology , Dogs , Female , Male , Patellar Dislocation/epidemiology , Patellar Dislocation/genetics , Pedigree , Thailand/epidemiologyABSTRACT
INTRODUCTION: Medial patellar luxation is thought to be associated with a high proximal position of the patella in the trochlear groove. OBJECTIVE: To determine whether the ratio of patellar ligament length and patellar length (L:P) is influenced by the stifle angle (75°, 96°, 113°, 130°, and 148°) in small dog breeds and to compare the L:P ratio in dogs of three small dog breeds with and without medial patellar luxation. METHODS: A mediolateral radiograph of the stifle joint was used to measure the L:P ratio in the stifle joints of dogs of three small breeds with and without medial patellar luxation. The L:P ratio was evaluated at five stifle angles (75°, 96°, 113°, 130°, and 148°) in 14 cadavers (26 stifle joints) of small dog breeds in order to identify the best stifle angle to measure the L:P ratio. Then the mean ± SD L:P ratio was calculated for normal stifles and stifles with medial patellar luxation grades 1, 2, and 3 in 194 Pomeranians, 74 Chihuahuas, and 41 Toy or Standard Poodles. RESULTS: The L:P ratio was the same for all five stifle angles in the cadavers (p = 0.195). It was also not significantly different in the three breeds (p = 0.135), in normal and medial patellar luxation-affected stifles overall (p = 0.354), and in normal and medial patellar luxation-affected joints within each breed (p = 0.19). CLINICAL SIGNIFICANCE: We conclude that a proximo-distal patellar position is not associated with medial patellar luxation in Pomeranians, Chihuahuas, and Toy or Standard Poodles. Thus a longer patellar ligament length does not play a role in the pathophysiology of medial patellar luxation in these small dog breeds.
Subject(s)
Dogs/injuries , Patellar Dislocation/veterinary , Stifle/injuries , Animals , Dogs/anatomy & histology , Female , Male , Patella/diagnostic imaging , Patella/pathology , Patellar Dislocation/diagnostic imaging , Patellar Dislocation/etiology , Patellar Dislocation/pathology , Radiography , Species Specificity , Stifle/diagnostic imaging , Stifle/pathologyABSTRACT
Seven Pomeranians with bidirectional patellar luxation (BPL) were prospectively studied regarding aetiology and results of a new surgical technique. Radiographic evaluation of the ratio between patellar ligament length and patellar bone length revealed no differences between Pomeranians with bidirectional patellar luxation and healthy stifle joints. Functional rather than anatomic patella alta might be associated with bidirectional patellar luxation in Pomeranians. The surgical outcome of extended proximal trochleoplasty was good-to-excellent in 87·5% of the stifles and all dogs achieved functional recovery. There was only minimal radiographic progression of osteophyte formation at 48 weeks after surgery. To the authors' knowledge, this is the first report on bidirectional patellar luxation in small breed dogs and its successful surgical treatment.
Subject(s)
Dogs/injuries , Patellar Dislocation/veterinary , Animals , Female , Lameness, Animal/etiology , Lameness, Animal/surgery , Male , Patella/diagnostic imaging , Patella/surgery , Patellar Dislocation/diagnostic imaging , Patellar Dislocation/surgery , Radiography , Stifle/diagnostic imaging , Stifle/injuries , Stifle/surgeryABSTRACT
The prevalence of patellar luxation (PL) and genetic factors potentially involved in the disorder were investigated in Dutch Kooiker dogs. A cohort of 842 Kooiker dogs, the offspring of 195 sires and 318 dams, was screened for PL from 1994 to 2011. The cohort was included in a pedigree of 1737 Kooiker dogs comprising nine generations. PL was present in 24% of screened dogs, with unilateral and bilateral luxation being observed equally frequently. Medial PL was more common (61%) than lateral PL (32%) or bidirectional PL (7%). The frequency of PL was similar in male and female dogs, with a female:male relative risk of 1.15 (95% confidence interval, CI, 0.90-1.48). The heritability of PL in the screened population was 0.27 ± 0.07. Since the start of the screening programme, the prevalence of PL decreased from 28% to 19%. A genome-wide association study of PL with 48 cases and 42 controls suggested the possible involvement of a region on chromosome 3 (Praw = 1.32 × 10(-)(5), Pgenome = 0.142), but the involvement of this region could not be confirmed in a validation group. Breeding programmes for complex diseases, such as PL, would benefit from combining pedigrees, phenotypes and genotypes, i.e. from genomic selection, as is currently the method of choice for breeding of production animals.
Subject(s)
Dog Diseases/epidemiology , Dog Diseases/genetics , Genome-Wide Association Study/veterinary , Patellar Dislocation/veterinary , Polymorphism, Single Nucleotide , Animals , Breeding , Cohort Studies , Dog Diseases/pathology , Dogs , Female , Inheritance Patterns , Male , Patellar Dislocation/epidemiology , Patellar Dislocation/genetics , Patellar Dislocation/pathology , Prevalence , Species SpecificityABSTRACT
In a prospective study, the outcome of surgical correction of medial patellar luxation of 70 stifle joints in 55 Pomeranian dogs was evaluated. Trochlear block recession alone was performed in 46 stifle joints, or in combination with tibial tuberosity transposition in 24 stifle joints in cases with grade II, III or IV medial patellar luxation. Additional procedures were performed to restore lateral and medial retinacular function. The recurrence of patellar luxation and the degree of lameness were evaluated up to at least 16 weeks after surgery. The overall recurrence rate was 10%. The outcome of surgery was considered good for grade II luxation with a 100% success rate. Recurrent medial patellar luxation was diagnosed in approximately 11% of dogs with grade III and in 36% of dogs with grade IV luxation. The postoperative lameness score decreased significantly in comparison with the preoperative score at four weeks and thereafter until the end of the study.
Subject(s)
Dog Diseases/surgery , Patellar Dislocation/veterinary , Animals , Body Size , Dogs , Female , Male , Patellar Dislocation/surgery , Postoperative Complications/veterinary , Treatment OutcomeABSTRACT
There is a high incidence of patellar luxation (PL) in Pomeranian dogs from Thailand. DNA samples were collected from 59 dogs originating from 15 families. PL was present in 75% of the dogs with a male:female ratio of 1:1.95. Polymorphic microsatellites situated close to the COL6A1, COL6A3, COL9A1, COL9A2, and COL9A3 genes were analyzed for linkage to the phenotype. Sibling-pair analysis revealed that none of the collagen markers analyzed had a high non-parametric linkage score with the highest score, 1.56, for COL9A2 (P=0.07). The low LOD scores for these collagen genes indicated a non-involvement in the pathogenesis of PL in Pomeranians. An association study with a low density single nucleotide polymorphism (SNP) set indicated the possible involvement of a region on chromosome 7. The association of this region remained indicative when larger groups of 43 cases and 40 controls were compared (Chi square test P=0.01).
Subject(s)
Collagen/genetics , Dog Diseases/genetics , Genetic Linkage , Microsatellite Repeats , Patella/pathology , Polymorphism, Single Nucleotide , Animals , Collagen/metabolism , Dog Diseases/epidemiology , Dogs , Female , Incidence , Male , Phenotype , ThailandABSTRACT
OBJECTIVES: To measure radiographically the inclination angle (ICA), femoral varus angle (FVA), anatomical lateral distal femoral angle (aLDFA), and mechanical lateral distal femoral angle (mLDFA) in Pomeranian dogs with and without medial patellar luxation (MPL). MATERIALS AND METHODS: Stifles of 34 Pomeranian dogs were graded and allocated into three groups: normal, grades I-II MPL, and grade III MPL. Angle values were measured from craniocaudal radiographs of the hindlimbs by each of the three examiners on three separate occasions. RESULTS: Each of the three groups consisted of 15 stifles. Means ± SD for the ICA, FVA, aLDFA and mLDFA in the normal stifles were 136.46 ± 7.12°, 5.85 ± 3.18°, 95.21 ± 3.48° and 99.46 ± 4°, respectively. No significant differences (p>0.05) in the measured values for the ICA between groups were observed. The FVA, aLDFA and mLDFA values in grade III MPL group were significantly (p<0.05) greater than those in the other two groups. Significant differences in the three angles between the normal and grades I-II MPL groups were not observed. CLINICAL SIGNIFICANCE: Significant change of distal femoral varus exists in Pomeranian dogs with grade III MPL.