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- Author or Editor: Gail K. Smith x
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Summary
Biplanar radiography was used to study normal growth of the left and right radius in 5 Beagles and growth of the left radius alone in 15 additional Beagles. We explored the applicability of this radiographic method in veterinary medicine by measuring the contribution to total radius length from each growth plate. Spherical tantalum markers (0.5 mm) were embedded in the proximal epiphysis, diaphysis, and distal epiphysis of each dog's radius at 10 weeks of age. Simultaneous biplanar radiographic views were obtained every 4 weeks until skeletal maturity was documented. A three-dimensional coordinate system was constructed allowing for measurement of growth (in millimeters). Resolution of the measuring system was 0.074 mm. Mean ± sem length of the skeletally mature Beagle's radius, as measured from proximal epiphyseal bead to distal epiphyseal bead, was 95.33 ± 1.07 mm. The percentage of contribution to the total radius length from the proximal and distal growth plates was 36.76 and 64.73%, respectively, with 95% confidence interval of 2.29%. The percentage of contribution to radius length from the distal radial growth plate increased for each consecutive time segment, with the distal radial physis contributing 61.75% from 10 to 14 weeks of age and increasing to 70.22% from 22 to 26 weeks of age. Significant growth was not observed after 26 weeks of age. The period of most rapid growth was between 10 and 14 weeks of age.
Biplanar radiography was accurate and precise in quantifying the relative contribution of the proximal and distal growth plate to radius length in Beagles. The method is applicable in veterinary research or clinical medicine for monitoring of axial and angular growth: physiologic, iatrogenic, or pathologic.
Abstract
Objective
To investigate the in vitro load/displacement characteristics of the hip joints in dogs as a function of joint position.
Sample Population
10 hip joints from 5 healthy dogs.
Procedure
A material test system was used to generate load/displacement curves for each joint. Joints were mounted in a custom-designed jig that held the joint in fixed anatomic orientations while plotting displacement and corresponding applied loads. All hips were cycled between 40 N of compression and 80 N of distraction. Each hip was tested at 10° increments from 30° flexion to 70° extension.
Results
When the hips were in a neutral orientation (approximately a standing position), load/displacement curves were characteristically sigmoidal (tri-phasic), indicating that, in this position, displacement was not highly dependent on load. The curves had a central low-stiffness region in which most of the lateral displacement took place. In contrast, when hips were positioned at the extremes of flexion and extension, this central, low-stiffness region was less distinct, and load/displacement curves were more linear, indicating a proportional relation between load and displacement. The load/displacement curve of 1 hip joint in the study deviated markedly from the others in a pattern consistent with cavitation of the synovial fluid.
Conclusions
When the hip joint is positioned in a neutral position, load-displacement behavior is sigmoidal, whereas when the hip joint is in an extended position, load/displacement behavior is more linear.
Clinical Relevance
Establishing load/displacement behavior of the hip joints in dogs was an important exercise in establishing the position for and estimating the repeatability of a clinical stress-radiographic method for quantitating joint laxity in dogs. (Am J Vet Res 1997;58:1078–1082)
SUMMARY
Ten coxofcmoral joints from 5 dog cadavers were used to study the effect of coxofcmoral positioning on passive hip laxity. A material test system was used to measure lateral translation when force was between 20 N of compression and 40 N of distraction. Using the orthogonal coordinate system imposed in this study, neutral position was empirically defined at 15° of extension and 10° of abduction, relative to the plane of the pelvis, and no internal or external rotation of the femur. The hips were mounted in a custom-designed jig that allowed 1 rotational degree of freedom (ie, either flexion extension, adduction/ abduction, or internal/external rotation), while holding the other 2 constant. Lateral translation of the hips was tested at 10° intervals from 30° of flexion to 70° of extension, 40° of adduction to 60° of abduction, and 30° of internal rotation to 40° of external rotation. Lateral displacement was maximal at 10° of extension, 20° of abduction, and 10° of external rotation, approximating the neutral coxofcmoral position during stance. As the hips were rotated into extreme positions, the amount of lateral displacement occurring with the same applied load decreased significantly to 32.0 to 65.3% of the maximal displacement. Determining the position of the hip associated with maximal passive laxity in vitro is essential to the design of a precise and accurate clinical stress-radiographic method to quantitate joint laxity in dogs. Our results confirm earlier work that passive hip joint laxity is at a maximum with the hip approximately in a neutral weight-bearing position.
Abstract
Objective
To determine the association between longitudinal bone growth and concentrations of growth hormone (GH) and insulin-like growth factor-I (IGF-I) in serum from prepubertal dogs.
Animals
6 male 14-week-old German Shepherd Dogs.
Procedure
Blood was obtained every 30 minutes for 14 consecutive days. Concentrations of GH and IGF-I in serum were determined, using a canine-specific radioimmunoassay and conventional radioimmunoassay after acid-ethanol extraction, respectively. Simultaneous biplanar radiography was performed daily to measure bone growth. Spectral analysis was used to estimate specific features of GH secretion during an extended period. Multiple linear regression with different lag times between independent and dependent variables was used to determine the strongest predictors of bone growth.
Results
The power spectra of GH concentrations in serum had a primary peak at a frequency of 0.02 cycles/h or a periodicity of 50 h/cycle. A significant determinant of longitudinal bone growth was a lag time of 1 day in concentration of GH in serum. The relationship between IGF-I concentration in serum and bone growth was not significant.
Conclusions
The primary frequency of GH secretion is outside the time frame of a single day and the concentration of GH in serum is a primary determinant of bone growth.
Clinical Relevance
A better understanding of the components of bone growth provide discernment to improved diagnosis and treatment of abnormal bone growth. (Am J Vet Res 1998;59:1608-1612)
Summary
A 3-year prospective study of large-breed dogs (4 months to 3 years of age) was conducted to evaluate the influence of radiographic positioning and age on coxofemoral joint (hip) laxity, subjective hip score, and development of degenerative joint disease (djd). The dogs (n = 142) were breeder- or client-owned and represented 14 breeds. With dogs under heavy sedation, hips were radiographed in the standard hip-extended position and in the new compression/distraction position at 4, 6, 12, 24, and 36 months of age. The standard hip-extended radiographic view was evaluated by 3 methods: subjective evaluation by a board-certified veterinary radiologist (WHR), according to the standard 7-point Orthopedic Foundation for Animals (OFA) scoring scheme (OFA/WHR); joint laxity quantitation, using the Norberg angle (NA) method; and subjective scoring by a veterinary orthopedic surgeon for radiographic evidence of djd. The hips in the distraction radiographic view were evaluated for passive hip laxity, as measured by use of a unitless distraction index (di).
Results of the study indicated that at a specific age (4, 6, 12, 24, or 36 months), all methods of hip evaluation correlated with each other at a moderate level (P < 0.05). The strength of contemporaneous correlation tended to increase with age of evaluation. Longitudinally, the between-method correlations were usually significant (P < 0.05), but not at a sufficiently high level to permit reliable between-method prediction. Prospective intraclass (within-method) statistical analysis of the various hip-scoring methods indicated that di was superior to NA and OFA/WHR in comparability of score over time. The intraclass correlation coefficient ranged from 0.55 to 0.91 for di in contrast to 0.40 to 0.78 for NA, and 0.06 to 0.39 for OFA/WHR over the age intervals of the study. For reference, the highest Kappa of 0.39 for the subjective OFA/WHR scoring reflected a maximal level of agreement between time intervals, only slightly better than chance. The associated large error questions the predictive use of the 7-point, subjective hip-scoring scheme, particularly prior to the age of 2 years.
Summary
A study was done to determine whether radiographic-distraction measurement of coxofemoral joint (hip) laxity at 4 and 8 months of age can serve as a predictor of hip dysplasia in older Labrador Retrievers. The method of Smith, Biery, and Gregor was used for radiologic examination of hips and for evaluation of radiographs. Mean (± sem) distraction laxity (ie, distraction index) for 10 adult disease-free dogs was 0.29 ± 0.05, whereas a group of 8 dogs with dysplastic hips had mean distraction index of 0.60 ± 0.10 (P < 0.05). Mean distraction index at 4 months of age for 11 pups of 4 litters from matings between dogs with normal hips was 0.39 ± 0.07, and was 0.54 ± 0.04 for 31 pups of 7 litters from matings between dogs with hip dysplasia. The distraction index and, thus, joint laxity at that age was significantly (P = 0.0351) different for the 2 groups. The distraction index at 4 months correlated positively with the distraction index at a later age at necropsy (r = 0.43; P = 0.0289). Distraction index < 0.4 at 4 months of age predicted normal hips in 88% of cases and distraction index ≥ 0.4 predicted hip dysplasia in 57% of the dogs. Logistic regression modeling indicated that the odds of a hip being normal decreased with increasing distraction index, and thus, with increasing joint laxity. The logistic regression models provided a reasonable mathematical description of the data. Based on the logistic model of the data, distraction indexes between 0.4 and 0.7 at either 4 or 8 months of age were not associated strongly enough with evidence of disease to be clinically reliable in predicting, on an individual basis, the outcome for dysplastic hip conformation when dogs were older. Index > 0.7 was associated with high probability for developing dysplastic joints and distraction index < 0.4 predicted normal hips with high probability.
Abstract
Objective
To evaluate in vivo repeatability of the distraction index method of evaluating hip joint laxity in dogs.
Animals
31 two-year-old Labrador Retrievers.
Procedure
Each dog was anesthetized and radiographically evaluated for hip joint laxity 4 times: twice by an experienced examiner and twice by an examiner who had no previous knowledge of or training in the technique prior to the first day of testing. Distraction indices (DI) were determined from the radiographs and intraclass correlation coefficients were calculated to evaluate the repeatability of DI measurements between and within examiners.
Results
Intraclass correlation coefficients were high (range, 0.85 to 0.94). Lower limits of the 95% confidence intervals for the intraclass correlation coefficients ranged from 0.75 to 0.89.
Conclusions
Between- and within-examiner repeatabilities of DI measurements were high, suggesting that the technique is clinically reliable.
Clinical Relevance
Distraction index is a reliable measure of hip joint laxity and a good predictor of the risk of development of degenerative joint disease associated with hip dysplasia in dogs. Establishment of high repeatability of DI measurements suggests that the stress-radiographic method may be used by multiple examiners with the expectation of comparable and consistent results. (Am J Vet Res 1997;58:1076–1077)
Summary
Passive laxity of the coxofemoral joints, as measured quantitatively by radiographing the joints under stress, has been shown to be an accurate measure of the risk for developing degenerative joint disease (djd) of the coxofemoral joints. Seventy-four Rottweilers between 12 and 40 months old were evaluated subjectively for radiographic evidence of djd, using the ventrodorsal view of the pelvis with the coxofemoral joints fully extended and the knees internally rotated (standard hip-extended view). Effect of age, sex, weight, and distraction index on the risk of developing djd was evaluated by use of a logistic regression model. Results were compared with those from a group of German Shepherd Dogs. Results indicated that in Rottweilers the distraction index was the only statistically significant predictor of the risk of developing djd of the coxofemoral joint. When German Shepherd Dogs were included in the model, they had a significantly greater risk of developing djd than did Rottweilers. This finding provides further support for the theory that there are differences in disease susceptibility among breeds and emphasizes the need to develop disease susceptibility curves for all breeds affected by hip dysplasia to facilitate accurate, scientifically based recommendations for breeding or treatment.
Abstract
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 hipextended 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 ≤ 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. ( J Am Vet Med Assoc 2004; 224:542–546)