Radiographic hip joint phenotype of the Pembroke Welsh Corgi.

OBJECTIVE: To investigate the radiographic hip joint phenotype of the Pembroke Welsh Corgi. STUDY DESIGN: Prospective and retrospective cross-sectional study. ANIMALS: Pembroke Welsh Corgis (n = 399). METHODS: Ventrodorsal, hip-extended radiographs were evaluated for subluxation, osteoarthritis (OA), caudolateral curvilinear osteophytes (CCO), and circumferential femoral head osteophytes (CFHO) of PennHIP evaluated Corgis. Joint laxity was measured by distraction index (DI). RESULTS: All Corgis had DI > 0.30 (mean, 0.66), 6.8% had OA, 18% had subluxation, 22.3% had CCO, and 74.4% had CFHO. Higher DI increased the odds for subluxation and canine hip dysplasia (CHD) but not for OA, CCO, or CFHO. The presence of CCO increased the odds for OA by 4.6 times (P = .002) and 2.2 times (P = .01) for hip dysplasia. All dogs with OA had CFHO. The presence of CFHO increased the odds for subluxation by 8.7 times (p < .001) and 8.9 times (P < .001) for hip dysplasia. Subluxation increased the odds for OA by 15.4 times (P < .001). CONCLUSION: Corgis had a low frequency of conventional OA despite having hip laxity that has been shown to correlate with hip OA and hip dysplasia in large-breed dogs. The relationship between CCO and OA was similar to published findings in nonchondrodystrophic large-breed dogs and the CFHO was significantly associated with subluxation. Both CCO and CFHO are associated with hip dysplasia in this small chondrodystrophic breed.

Chronology of hip dysplasia development in a cohort of 48 Labrador retrievers followed for life.

OBJECTIVE: To determine the chronology of radiographic signs of canine hip dysplasia (CHD), specifically joint laxity and secondary osteoarthritis (OA). STUDY DESIGN: Longitudinal cohort study. ANIMALS: Paired littermates, 48 Labrador retrievers. METHODS: Conventional, ventrodorsal, hip-extended (HE) radiographs were evaluated yearly for CHD according to the subjective criteria of the Orthopedic Foundation for Animals (OFA). PennHIP screening was performed at 2 years of age to assess joint laxity by distraction index (DI). Histopathologic evaluation of coxofemoral joints was performed at the dogs' natural end of life. RESULTS: Coxofemoral subluxation, as identified on the HE radiograph occurred by 2 years of age and not thereafter. Accuracy of OFA-criteria scoring was poor: 55% of dogs scored "normal" at 2 years of age became radiographically dysplastic by the end of life (45% negative predictive value, NPV); 92% of the dogs scored as normal at 2 years of age had histopathologic OA of CHD (8% NPV). The DI predicted all 48 dogs to be susceptible to OA of CHD and 98% had radiographic or histopathologic OA by the end of life. CONCLUSION: OFA-criteria score was profoundly influenced by environmental factors, such as diet restriction and age, reducing its value as a selection criterion. DI measurements were not influenced by dietary treatment suggesting higher trait heritability.

Evaluation of the relationship between Orthopedic Foundation for Animals' hip joint scores and PennHIP distraction index values in dogs.

OBJECTIVE: To compare 2 screening methods for detecting evidence of hip dysplasia (Orthopedic Foundation for Animals [OFA] and PennHIP) in dogs. DESIGN: Diagnostic test evaluation study. Animals-439 dogs >or= 24 months of age that received routine hip joint screening from June 1987 through July 2008. PROCEDURES: Dogs were sedated, and PennHIP radiography was performed (hip joint- extended [HE], compression, and distraction radiographic views). The HE radiographic view was submitted for OFA evaluation. A copy of the HE radiographic view plus the compression and distraction radiographic views were submitted for routine PennHIP evaluation, including quantification of hip joint laxity via the distraction index (DI). RESULTS: 14% (60/439) of dogs had hip joints scored as excellent by OFA standards; however, 52% (31/60) of those had a DI >or= 0.30 (range, 0.14 to 0.61). Eighty-two percent of (183/223) dogs with OFA-rated good hip joints had a DI >or= 0.30 (range, 0.10 to 0.77), and 94% (79/84) of dogs with OFA-rated fair hip joints had a DI >or= 0.30 (range, 0.14 to 0.77). Of all dogs with fair to excellent hip joints by OFA standards, 80% (293/367) had a DI >or= 0.30. All dogs with OFA-rated borderline hip joints or mild, moderate, or severe hip dysplasia had a DI >or= 0.30 (range, 0.30 to 0.83). CONCLUSION AND CLINICAL RELEVANCE: Dogs judged as phenotypically normal by the OFA harbored clinically important passive hip joint laxity as determined via distraction radiography. Results suggested that OFA scoring of HE radiographs underestimated susceptibility to osteoarthritis in dogs, which may impede progress in reducing or eliminating hip dysplasia through breeding.

Effects of osteoarthritis on radiographic measures of laxity and congruence in hip joints of Labrador Retrievers.

OBJECTIVE- To determine effects of hip joint osteoarthritis on radiographic measures of hip joint laxity and congruence. DESIGN- Longitudinal study. ANIMALS- 40 Labrador Retrievers. PROCEDURES- Dogs were assigned to 2 groups based on radiographic evidence of osteoarthritis. Dogs in the osteoarthritis group were free of osteoarthritis at initial radiographic evaluation (t(1)) and developed osteoarthritis by a subsequent radiographic evaluation (t(2)). Dogs in the nonosteoarthritis group had no radiographic osteoarthritis at either evaluation. Hip joint laxity was quantified by use of the distraction index (DI) from a distraction radiographic view and use of the Norberg angle (NA) from a ventrodorsal hip-extended radiographic view. The compression index (CI) from a compression radiographic view was used as a measure of joint congruence (concentricity). RESULTS- Hip joint laxity (NA or DI) did not change over time in the nonosteoarthritis group. Mean hip joint laxity (NA and DI) for the osteoarthritis group was greater at t(1) than for the nonosteoarthritis group. With the onset of osteoarthritis, mean NA decreased significantly and mean CI increased significantly, but mean DI remained unchanged. CONCLUSIONS AND CLINICAL RELEVANCE- No radiographic evidence for compensatory hip joint tightening associated with osteoarthritis was detected. Hip-extended radiography revealed that hip joints got looser with osteoarthritis and NA decreased. Hip joint laxity (DI) on distraction radiographs was unchanged by the onset of osteoarthritis and remained constant in the osteoarthritis and nonosteoarthritis groups at both evaluations. However, the CI increased with osteoarthritis, as reflected in nonzero indices (incongruence). The CI may be a valid marker for early hip joint osteoarthritis.

External fixator clamp reuse degrades clamp mechanical performance.

OBJECTIVE: To determine the effects of clamp reuse for the Kirschner-Ehmer (KE); Securos; and the IMEX-SK clamp. STUDY DESIGN: Experimental bench test of mechanical properties. METHODS: Specially designed fixtures were used to mechanically test 18 clamps of each type with respect to 6 mechanical variables: fixator pin slippage, connecting bar slippage, fixator pin rotation, connecting bar rotation, and clockwise and counterclockwise clamp-bolt axis pivot. Each clamp was tested 6 times for each variable at 7.68 Nm of clamp-bolt tightening torque. RESULTS: were compared using repeated measures ANOVA. Results- For the IMEX-SK clamp, a significant degradation in the force required to cause slippage was found for connecting bar slippage and fixator pin rotation; however, this clamp also had a significant increase in the force to initiate slippage for clockwise clamp-bolt axis pivot with reuse. The Securos clamp had significant degradation in connecting bar slippage, connecting bar rotation, and fixator pin rotation whereas the KE clamp had significant degradation in connecting bar slippage only. CONCLUSIONS: All 3 external fixator clamp types degraded in 1 or more movement variables in their ability to resist motion with reuse. The IMEX and Securos clamps were more subject to degradation than the KE clamp and this may have clinical importance for fixator composite rigidity. CLINICAL RELEVANCE: Fracture-reduction stability is related to the ability to resist motion within a clamp. The unpredictable nature of degradation we found cautions against repeated use. Clinicians should consider reuse of external fixator clamps with the knowledge that repeated use degrades clamp mechanical performance.

Un-united medial epicondyle of the humerus: radiographic prevalence and association with elbow osteoarthritis in a cohort of labrador retrievers.

OBJECTIVE: To longitudinally characterize the radiographic appearance of un-united medial epicondyle (UME) of the humerus, evaluate UME association with osteoarthritis (OA) and consider its relevance to the elbow dysplasia complex. STUDY DESIGN: Longitudinal cohort study. ANIMALS: Labrador retrievers (n=48) from 7 litters. METHODS: Forty-eight same-sex littermates were paired for this lifetime feeding study. One of each pair was control-fed; the pair mate was fed 25% less than the control each day. Elbows of 46 surviving dogs were radiographed at ages 6 and 8 years, and/or at end-of-life (EOL). Elbow histopathology was done EOL, although UME lesions were not evaluated histologically. RESULTS: Seven dogs (15%) had UME, representing 5 litters; 4 were control-fed, 3 diet-restricted. Six (86%) dogs had unilateral lesions; 1 was bilateral. UME was evident on craniocaudal (CrCd) radiographic projections by 8 years in all dogs. UME was detected in only 1 elbow by mediolateral radiographic projection. Elbow OA frequency in UME affected dogs was not significantly different from the remaining study population. Histopathologic lesions were bilateral in dogs with unilateral UME. CONCLUSIONS: UME may be more common than previously thought. Most cases were unilateral and diet restriction had no effect on frequency. The CrCd view was critical for diagnosis. Elbow OA was not directly associated with UME. CLINICAL RELEVANCE: Infrequent diagnosis of UME could result from infrequent radiography and use of only the flexed lateral radiographic projection required by the Orthopedic Foundation for Animals for elbow screening. Like hip evaluations, screening for UME should be continued for life, until genetics are better understood. Lack of association between UME and elbow OA suggests that UME is not likely a component of elbow dysplasia.

A longitudinal study of the influence of lifetime food restriction on development of osteoarthritis in the canine elbow.

OBJECTIVE: To report the effects of age and lifetime calorie restriction on development and progression of osteoarthritis (OA) in elbow joints of Labrador retrievers. STUDY DESIGN: Longitudinal cohort study. ANIMALS: Labrador retriever dogs (n=48). METHODS: Puppies from 7 litters were allotted to 2 groups of 24 dogs each. Diet-restricted (DR) dogs received 25% fewer calories than control-fed (CF) pair mates. Elbow radiographs were taken at 6 and 8 years of age and end of life (EOL). Gross and histopathologic evaluations for OA occurred at EOL. RESULTS: There was no statistical difference in radiographic OA frequency between groups at any of the time points. Radiographic OA severity was greater for CF dogs at 6 years only (P<.05). There was no significant difference between feeding groups for histopathologic prevalence or severity of OA. Similarly, there were no differences in gross OA lesions between the groups (P>.05). Fragmented medial coronoid process, un-united anconeal process, and osteochondrosis were not present in any elbow. CONCLUSION: No differences in prevalence or severity of radiographic and histopathologic elbow OA were found between feeding groups. Diet restriction resulted in a 1.8-year extension in median lifespan but no additional incremental worsening of elbow disease. Evaluation at time points <6 years may have revealed larger differences in OA prevalence and severity between the dietary groups. CLINICAL RELEVANCE: These findings support calorie restriction as a clinical tool to slow progression of elbow OA.

Genetic improvement of hip-extended scores in 3 breeds of guide dogs using estimated breeding values: Notable progress but more improvement is needed.

Two hip quality phenotypes-a hip-extended score assigned by a board certified radiologist and the PennHIP distraction index-were analyzed to estimate genetic parameters and to calculate estimated breeding values used for selecting replacement breeders. Radiographs obtained at 12-18 months of age were available on 5,201 German Shepherd Dogs, 4,987 Labrador Retrievers and 2,308 Golden Retrievers. Obtained by fitting a two-trait model using Bayesian techniques, estimates of heritability for the hip-extended score were 0.76, 0.72, and 0.41 in German Shepherd Dogs, Labrador Retrievers, and Golden Retrievers, respectively, while estimated heritabilities for distraction index were 0.60, 0.66 and 0.59, respectively. Genetic correlations between the two hip quality measures were -0.28 in German Shepherd Dogs, -0.21 in Labrador Retrievers, and -0.29 in Golden Retrievers. Genetic selection for improved hip quality based upon the hip extended score phenotype began in 1980. Among first generation puppies, 34% of 273 German Shepherd Dogs, 55% of 323 Labrador Retrievers, and 43% of 51 Golden Retrievers had an Excellent hip extended score. After 8 generations of selection, mostly based on estimated breeding values derived from the hip extended score, over 93% of 695 German Shepherd Dogs, 94% of 528 Labrador Retrievers, and 87% of 116 Golden Retrievers received an Excellent hip extended score. With respect to PennHIP distraction index values among these same dogs, median values were at or above 0.30 for all 3 breeds meaning that half or more of dogs possessing the Excellent hip-extended-score phenotype remained susceptible to developing the osteoarthritis of canine hip dysplasia. Genetic improvement of the hip-extended-view phenotype to its desired biological endpoint left a surprising proportion of dogs expressing sufficient joint laxity to place them in an osteoarthritis at-risk state as they age. Only by directly applying selection pressure to reduce distraction index was marked reduction in joint laxity noted.

The effects of lifetime food restriction on the development of osteoarthritis in the canine shoulder.

OBJECTIVE: To report effects of age and lifetime food restriction on development and progression of shoulder joint osteoarthritis (OA) in Labrador retriever dogs. STUDY DESIGN: Longitudinal life-span, cohort study. ANIMALS: Labrador retriever dogs (n=48). METHODS: Littermates were paired (gender, weight) to make 24 pairs of genetically similar dogs. Each diet-restricted (DR) pair-mate was fed daily 75% of the same diet consumed by its control-fed (CF) pair-mate for life. Shoulders were evaluated radiographically at years 6, 8, and end of life (EOL). At EOL shoulders were evaluated grossly and by histopathology for OA. RESULTS: Radiographic evidence of shoulder OA was identified in 78% of dogs. Severity of radiographic shoulder OA at 6 (P<.03) and 8 years (P<.02) was significantly lower among DR dogs compared with CF dogs. Pooled gross evaluation results revealed 40 of 46 dogs had cartilage erosion on the caudal aspect of the humeral head. By EOL, 91% of dogs had histopathologic changes consistent with OA. CONCLUSION: There was a high overall prevalence of radiographic, gross, and histologic OA among dogs. Substantial disparity was found between radiographic evidence of OA (at EOL) and characteristic changes visible by gross and histologic examination. CLINICAL RELEVANCE: Radiographic evaluation correlates poorly with severity of shoulder joint pathology. The benefits of DR on shoulder OA are consistent with the demonstrated effect of DR in delaying species- and strain-specific diseases of aging.

Evaluation of a circumferential femoral head osteophyte as an early indicator of osteoarthritis characteristic of canine hip dysplasia in dogs.

OBJECTIVE: To determine the relationship between a circumferential femoral head osteophyte (CFHO) and osteoarthritis characteristic of canine hip dysplasia, and to ascertain whether CFHO, like osteoarthritis, varies between diet-restricted and control-fed dogs. DESIGN: Longitudinal cohort study. ANIMALS: 48 Labrador Retrievers. PROCEDURES: Dogs were paired by size, sex, and litter and assigned to 1 of 2 equal groups at 2 months of age. The control-fed group was fed ad libitum, and the diet-restricted group was fed 25% less on a pairwise basis of the same diet for life. The dogs' hip joints were radiographed yearly for life. Each radiograph was evaluated for radiographic signs of osteoarthritis characteristic of hip dysplasia and for the presence and severity of a CFHO. RESULTS: 41 of the 48 (85.4%) dogs had a CFHO, which was detected at a median age of 5.4 years, and 33 of those 41 (80.5%) developed radiographic evidence of osteoarthritis. Nineteen (79.2%) dogs in the diet-restricted group and 22 (91.7%) in the control-fed group had a CFHO at a median age of 9 and 3 years, respectively. Of the dogs with a CFHO, 12 (63.2%) in the diet-restricted group and 20 (90.0%) in the control-fed group developed radiographic evidence of osteoarthritis characteristic of hip dysplasia at a median age of 11 and 6.5 years, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated a relationship between the CFHO and subsequent development of radiographic signs of osteoarthritis. If a CFHO is present in Labrador Retrievers, it might be considered an early indicator of osteoarthritis.

Failure mode and bending moment of canine pancarpal arthrodesis constructs stabilized with two different implant systems.

OBJECTIVE: To compare failure mode and bending moment of a canine pancarpal arthrodesis construct using either a 2.7 mm/3.5 mm hybrid dynamic compression plate (HDCP) or a 3.5 mm dynamic compression plate (DCP). STUDY DESIGN: Paired in vitro biomechanical testing of canine pancarpal arthrodesis constructs stabilized with either a 2.7/3.5 HDCP or 3.5 DCP. SAMPLE POPULATION: Paired cadaveric canine antebrachii (n=5). METHODS: Pancarpal arthrodesis constructs were loaded to failure (point of maximum load) in 4-point bending using a materials-testing machine. Using this point of failure, bending moments were calculated from system variables for each construct and the 2 plating systems compared using a paired t-test. To examine the relationship between metacarpal diameter and screw diameter failure loads, linear regression was used and Pearson' correlation coefficient was calculated. Significance was set at P<.05. RESULTS: HDCP failed at higher loads than DCP for 9 of 10 constructs. The absolute difference in failure rates between the 2 plates was 0.552+/-0.182 N m, P=.0144 (95% confidence interval: -0.58 to 1.68). This is an 8.1% mean difference in bending strength. There was a significant linear correlation r=0.74 (P-slope=.014) and 0.8 (P-slope=.006) between metacarpal diameter and failure loads for the HDCP and 3.5 DCP, respectively. CONCLUSION: There was a small but significant difference between bending moment at failure between 2.7/3.5 HDCP and 3.5 DCP constructs; however, the difference may not be clinically evident in all patients. CLINICAL RELEVANCE: The 2.7/3.5 HDCP has physical and mechanical properties making it a more desirable plate for pancarpal arthrodesis.

Kinetic gait analysis of healthy dogs on two different surfaces.

OBJECTIVE: To determine the effects of 2 different, commonly used surfaces with different coefficients of friction on ground reaction forces in normal dogs. STUDY DESIGN: Prospective, observational, single cross-over study. ANIMALS: Dogs (n=10) with no gait abnormalities. METHODS: Dogs were acclimated to the force plate and 5 valid trials for each dog and each limb were recorded. Velocity and acceleration were tightly controlled. Each dog was tested on both surfaces sequentially in different sequences. Data analysis was done on peak vertical force, peak impulse, breaking and propulsion peak forces and impulses. Three-way repeated measures analysis of variance was used to separately evaluate the effect of floor type on force plate measures in fore and hind limbs, while controlling for side (left versus right) and experimental replicate. P-values<.05 were considered significant. Mean force and 95% confidence interval for the 6 variables analyzed for all limbs on each surface were calculated. RESULTS: There were no significant differences in ground reaction forces between the linoleum and the carpet surface for thoracic or pelvic limbs for all gait variables measured. There were no significant differences between each individual gait trial per dog between the right and left thoracic limbs trials nor differences between the right and left pelvic limb trials. CONCLUSIONS: Normal dogs had no change in their ground reaction forces on linoleum and carpet surfaces. CLINICAL RELEVANCE: Kinetic results from multi-center or comparative trials will not be affected by use of either linoleum or carpet surfaces.

Lifelong diet restriction and radiographic evidence of osteoarthritis of the hip joint in dogs.

OBJECTIVE: To evaluate the effects of diet restriction on development of radiographic evidence of hip joint osteoarthritis in dogs. DESIGN: Longitudinal cohort study. ANIMALS: 48 Labrador Retrievers from 7 litters. PROCEDURES: Forty-eight 6-week-old puppies from 7 litters were paired with littermates by sex and weight, and each pairmate was randomly assigned to 1 of 2 groups of 24 dogs each. Starting at 8 weeks of age, 1 group was fed ad libitum (control fed) and the other was fed 25% less (restricted fed) of the same diet for life on a pairwise basis. The dogs' hip joints were radiographed in the standard ventrodorsal hip-extended view at multiple intervals prior to 1 year of age and at annual intervals thereafter on the basis of birth anniversary. A board-certified radiologist unaware of group assignment scored the radiographs for evidence of osteoarthritis. RESULTS: Prevalence of radiographic evidence of hip joint osteoarthritis in all dogs increased linearly throughout the study, from an overall prevalence of 15% at 2 years to 67% by 14 years. Restricted-fed dogs had lower prevalence and later onset of hip joint osteoarthritis. Median age at first identification of radiographic evidence of hip joint osteoarthritis was significantly lower in the control-fed group (6 years), compared with the restricted-fed group (12 years). CONCLUSIONS AND CLINICAL RELEVANCE: Restricted feeding delayed or prevented development of radiographic signs of hip joint osteoarthritis in this cohort of Labrador Retrievers. Lifetime maintenance of 25% diet restriction delayed onset and reduced severity of hip joint osteoarthritis, thus favorably affecting both duration and quality of life. In addition, the data indicated that development of hip joint osteoarthritis was not bimodal in these dogs but occurred as a continuum throughout life.

Effects of electrostimulated acupuncture on ground reaction forces and pain scores in dogs with chronic elbow joint arthritis.

OBJECTIVE: To determine whether use of electrostimuluated acupuncture (ESA) would result in significant improvements in ground reaction forces and lameness scores in dogs with chronic elbow joint osteoarthritis secondary to elbow joint dysplasia. DESIGN: Randomized, controlled, crossover clinical trial. ANIMALS: 9 dogs with chronic forelimb lameness and radiographic evidence of elbow joint osteoarthritis. PROCEDURES: All dogs had a 3-week control acclimation period during which gait analysis was performed weekly. Dogs then received ESA once weekly for 3 weeks followed by a sham treatment once weekly for 3 weeks or received the sham treatment followed by ESA. Gait analysis was repeated prior to each treatment, and owners were asked to provide pain scores by use of a visual analog scale method. RESULTS: Treatment (control, acupuncture, or sham) did not have a significant effect on ground reaction forces for any limb. Owners of 8 of the 9 dogs were able to correctly guess the time period when ESA was delivered. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that ESA did not have any significant effects on severity of lameness, as determined by measurement of ground reaction forces, or severity of pain, as determined by visual analog scale pain scores, in dogs with chronic elbow joint osteoarthritis secondary to elbow joint dysplasia.

Estimates of prevalence of hip dysplasia in Golden Retrievers and Rottweilers and the influence of bias on published prevalence figures.

OBJECTIVE: To estimate prevalence of canine hip dysplasia (CHD) in Golden Retrievers and Rottweilers and identify sources of bias in published reports. DESIGN: Prospective study. ANIMALS: 200 clinically normal Golden Retrievers and 140 clinically normal Rottweilers between 24 and 60 months of age referred for hip evaluation (group 1) and 93 clinically normal dogs evaluated for Orthopedic Foundation for Animals (OFA) hip certification (group 2). PROCEDURE: Hip-extended pelvic radiographs from group 1 dogs were screened for CHD. Radiographs were evaluated twice; the first interpretation used an OFA-type subjective 7-point scoring system, and the second included the caudolateral curvilinear osteophyte as an additional sign of degenerative joint disease. The OFA submission rate of group 2 dogs was determined from the number of official reports returned from the OFA. RESULTS: Prevalence of CHD in Golden Retrievers ranged from 53% to 73% and in Rottweilers ranged from 41% to 69%. Among dogs referred for OFA evaluation, radiographs from 49 (53%) were submitted to OFA. Of submitted radiographs, 45 (92%) were normal; of radiographs not submitted, 22 (50%) were normal. Radiographs with normal-appearing hips were 8.2 times as likely to be submitted to the OFA. Compared with Golden Retrievers, Rottweiler radiographs were significantly more likely to be submitted for OFA certification. CONCLUSIONS AND CLINICAL RELEVANCE: Prevalence of CHD in these 2 breeds may be much higher than previously reported in the United States. Results suggest substantial bias in the OFA database, which causes lower estimates of prevalence of CHD.

Evaluation of a radiographic caudolateral curvilinear osteophyte on the femoral neck and its relationship to degenerative joint disease and distraction index in dogs.

OBJECTIVE: To determine prevalence of a radiographic caudolateral curvilinear osteophyte (CCO) on the femoral neck in various breeds and age groups of dogs and to evaluate its contemporaneous relationship with degenerative joint disease (DJD) and distraction index (DI). DESIGN: Cross-sectional prevalence study. ANIMALS: 25,968 dogs, including 3,729 German Shepherd Dogs, 4,545 Golden Retrievers, 6,277 Labrador Retrievers, and 1,191 Rottweilers. PROCEDURE: Data from the University of Pennsylvania Hip Improvement Program database were analyzed, including ventrodorsal hip-extended, compression, and distraction radiographs. The CCO and radiographic signs of DJD were considered independent events and were interpreted as either present or absent. Statistical methods were used to evaluate the CCO as a possible risk factor for DJD and assess its association with DI, as measured by use of distraction radiography. RESULTS: When all breeds were pooled, DJD was detected in 8.6% of dogs, and the CCO was detected in 21.6% of dogs. Among dogs with a CCO, 25.1% had radiographic evidence of DJD. Among dogs without a CCO, only 4% had DJD. Dogs with a CCO were 7.9 times as likely to have DJD as were those without a CCO. Additionally, DI, weight, and age were significant risk factors for the CCO. CONCLUSION AND CLINICAL RELEVANCE: Results confirm the contemporaneous association between the CCO and DJD and that passive hip laxity, as measured by use of the DI, is associated with both the CCO and DJD.

Risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk herniation in dogs: 229 cases (1994-2000).

OBJECTIVE: To assess risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk disease (IVDD) in dogs that had decompressive laminectomy without attempted prophylactic treatment of other disk spaces. DESIGN: Retrospective study. ANIMALS: 229 dogs. PROCEDURE: Medical records of dogs that had decompressive laminectomy without prophylactic fenestration for a first episode of IVDD and were available for follow-up were reviewed. Information on 7 clinical and 8 radiographic potential risk factors were recorded. RESULTS: Clinical signs associated with recurrence of IVDD developed in 44 (19.2%) dogs. Ninety-six percent of recurrences developed within 3 years after surgery. Recurrence developed in 25% of Dachshunds and 15% of dogs of other breeds combined. Number of opacified disks was a significant risk factor for recurrence. Risk increased with number of opacified disks in an almost linear manner; each opacified disk increased risk by 1.4 times. Dogs with 5 or 6 opacified disks at the time of first surgery had a recurrence rate of 50%. CONCLUSIONS AND CLINICAL RELEVANCE: When all likely episodes of recurrence are considered and a long follow-up period is achieved, true rate of recurrence of IVDD appears to be higher than in many previous reports. Dogs with multiple opacified disks at the time of first surgery should be considered a high-risk subpopulation.

Comparison of two radiographic techniques for evaluation of hip joint laxity in 10 breeds of dogs.

OBJECTIVE: To evaluate hip joint laxity in 10 breeds of dogs via 2 radiographic techniques. ANIMALS: 500 clinically normal dogs. DESIGN: Prospective study. PROCEDURE: Radiographs obtained via routine hip joint evaluations performed in sedated dogs of 10 popular breeds were randomly selected from a database. Measurements of distraction index (DI) and hip-extended index (HEI) on 1 hip joint radiograph randomly chosen from each dog were made. RESULTS: Mean age of dogs was 20.7 months. Mean HEI was 0.17 (range, 0.0 to 0.72) and mean DI was 0.44 (range, 0.07 to 0.96). Borzois had uniformly tight hip joints as judged by use of both methods and were considered the gold standard by which hip joint laxity was judged (all Borzois had DI < or = 0.32). Overall, DI was significantly greater than HEI. Within each breed, mean DI was always greater than mean HEI. Significant differences were detected among breeds for HEI; however, compared with DI, the magnitude of differences among breeds was less. CONCLUSIONS AND CLINICAL RELEVANCE: Distraction radiography detected the greatest range and magnitude of passive hip laxity in the 10 breeds of dogs. The difference in values between breeds known to have high prevalence of canine hip dysplasia and those in Borzois was greater for DI than for HEI. Breeds must be evaluated individually because of inherent differences in hip joint laxity.

Use of the caudolateral curvilinear osteophyte as an early marker for future development of osteoarthritis associated with hip dysplasia in dogs.

OBJECTIVE: To determine the relationship between the caudolateral curvilinear osteophyte (CCO) and osteoarthritis associated with hip dysplasia in dogs. DESIGN: Longitudinal cohort study. ANIMALS: 48 Labrador Retrievers from 7 litters. PROCEDURE: In each of 24 sex- and size-matched pairs fed the same diet, a restricted-fed dog was fed 25% less than a control dog for life. The dogs' hips were evaluated in the standard ventrodorsal hip-extended radiographic projection at 16, 30, and 52 weeks of age and then yearly for life. Histologic examination of hip joint tissues was performed on 45 dogs. RESULTS: Median age at death was 11.2 years. Adjusting for feeding group, dogs with a CCO were 3.7 times as likely to develop radiographic signs of osteoarthritis than those without a CCO. Stratified by diet, 100% of the control dogs with a CCO developed radiographic signs of osteoarthritis and 55% of restricted-fed dogs with a CCO developed radiographic signs of osteoarthritis. The CCO was the first radiographic change seen in 22 of 29 (76%) dogs with osteoarthritis. Overall, 35 of 37 (95%) dogs with a CCO had histopathologic lesions of osteoarthritis. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate a relationship between a CCO on the femoral neck and subsequent development of radiographic signs of osteoarthritis in Labrador Retrievers evaluated over their life span. A CCO is an important early radiographic indication of osteoarthritis associated with canine hip dysplasia.

Effects of diet restriction on life span and age-related changes in dogs.

OBJECTIVE: To evaluate the effects of 25% diet restriction on life span of dogs and on markers of aging. DESIGN: Paired feeding study. ANIMALS: 48 Labrador Retrievers. PROCEDURES: Dogs were paired, and 1 dog in each pair was fed 25% less food than its pair-mate from 8 weeks of age until death. Serum biochemical analyses were performed, body condition was scored, and body composition was measured annually until 12 years of age. Age at onset of chronic disease and median (age when 50% of the dogs were deceased) and maximum (age when 90% of the dogs were deceased) life spans were evaluated. RESULTS: Compared with control dogs, food-restricted dogs weighed less and had lower body fat content and lower serum triglycerides, triiodothyronine, insulin, and glucose concentrations. Median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that 25% restriction in food intake increased median life span and delayed the onset of signs of chronic disease in these dogs.