Inclination and Anteversion Angles of the Femoral Head and Neck in the Dog Evaluation of a Standard Method of Measurement

The inclination and anteversion angles of the femoral head and neck in 30 mongrel dogs were determined using a radiographic biplanar technique. The angle of anteversion of the 30 necropsy specimens was measured directly and compared with the in vivo radiographic measurements.
The average value for the angles of anteversion, inclination, and corrected real angles of inclination were 31.3°, 148.8°, and 144.7°, respectively. Graphs were established using existing trigonometric relations to facilitate the analysis. The method used was found to be simple, reliable, and accurate. The mean difference between the indirect radiographic biplanar technique and direct measurements on isolated bones was ° 1.5°. The difference between the mean values of anteversion angles determined after radiographic biplanar technique and direct bone measurements was not significant (p > 0.05).     

Radiological and osteological study of the pelvic limbs in free‐ranging capybaras (Hydrochoerus hydrochaeris)

This study aimed to describe the radiographic anatomy and osteology and to evaluate angular radiographic measurements—Norberg angle, inclination angle and anteversion angle—of the pelvic limbs in free‐ranging capybaras. Twenty cadavers of free‐ranging capybaras (Hydrochoerus hydrochaeris), including five adults and 15 subadults, were studied. Ventrodorsal, craniocaudal, dorsoplantar and mediolateral radiographic views of the pelvic limbs were obtained. The radiographic features were described together with bone samples. The hip bone (os coxae), shaped like an isosceles trapezoid, was elongated and narrow with the presence of an oblong obturator foramen, sagittal ilial wing and rectilinear ilial body. The femoral shaft was relatively straight, while the greater trochanter was projected above the femoral head. No sesamoid bones of the gastrocnemius and popliteus muscles were observed radiographically or for those animals used in gross macroscopy. The fibula was located lateral and parallel to the tibia. Eight tarsal bones, four metatarsal bones and three digits were identified. The mean radiographic measurements included Norberg angle of 125.9°; respective angles of femoral inclination by the Hauptman B and Tomlinson methods of 139.9 and 141°; anteversion angle of the femoral head and neck of 29.80°. The bones of the pelvic limbs in capybaras have several anatomical characters and radiological features that are shared with members of the caviomorph superfamily Cavioidea. The radiographic angles measured in this study help characterize the functional morphology of this species.     

Biomechanical Evaluation of Acetabular Cup Implantation in Cementless Total Hip Arthroplasty

Objective: To report biomechanical properties of the Biologic Fixation System (BFX) acetabular cup impacted into a normal canine pelvis and to compare the effect of implant positioned to and beyond the medial acetabular wall. Study Design: In vitro cadaveric study. Animals: Hemipelves of mature, large‐breed dogs (n=6). Methods: For each dog, 1 hemipelvis was reamed to the depth of the acetabular wall (group A) and 1 was reamed an additional 6 mm after penetration of the medial cortex of the acetabulum (group B). The hemipelves were implanted with acetabular cups and loaded in compression through a matching femoral prosthetic component until failure. Specimen stiffness, and failure displacement, load, and energy were determined from load and displacement data and results between groups compared with a paired t‐test. Results: Mean failure load was greater in group A (3812 ± 391 N) than group B (2924 ± 316 N; P<.014). No other differences (P>.05) were observed between groups. Bone fracture (n=5) and cup displacement (1) occurred in group A whereas in group B there were 3 fractures and 3 cup displacements. Conclusions: Although medial placement of the BFX cup affected compressive failure loads, failure loads for both groups exceeded normal physiologic loads. Clinical Relevance: Medial positioning of the acetabular cup does not appear to compromise acetabular implant‐pelvic stability under normal physiologic loads. Because arthroplasty candidates often have abnormal acetabular architecture, mechanical properties of the cup placed in acetabula without a dorsal rim should be investigated.     

Radiographic measurements of the hindlimbs in crab‐eating foxes (Cerdocyon thous,Linnaeus, 1766)

Life expectancy of crab‐eating foxes in captivity is approximately 11 years, which favours the development of diseases including orthopaedic disorders. However, to understand disorders that may affect these animals, it is worth determining a normal range of measurements. Therefore, this study aimed to evaluate radiographic measurements of joint angles of the hindlimbs and the ratio of patellar ligament length to patellar length in healthy crab‐eating foxes. Fifteen captive crab‐eating foxes (Cerdocyon thous), eight males and seven females, aged more than 1 year old, weighing 5.5–7.9 kg were used. Anatomic and mechanical femoral joint angles were assessed in ventrodorsal radiographic views, and mediolateral views were taken to measure patellar ligament length and patellar length, and the tibial plateau angle. The right and left hindlimbs were evaluated. All measurements were conducted in triplicate by the same investigator. No statistically significant differences were observed between sides in the radiographic measurements. The anatomic lateral proximal femoral angle and the anatomic lateral distal femoral angle recorded mean values of 95.43° and 92.75°, respectively. The mechanical lateral proximal femoral angle and the mechanical lateral distal femoral angle recorded mean values of 93.39° and 96.75°, respectively. Inclination angles measured according to the Tomlinson, Hauptman A and Hauptman B methods were 133.80°, 147.32° and 128.63°, respectively. The tibial plateau recorded 18.77°, and the ratio of the patellar ligament length to the patellar length was 1.99. In conclusion, the collected data are important to characterize the normal values of crab‐eating fox limbs.     

Radiographic evaluation of acetabular component position in dogs

OBJECTIVE: To assess the usefulness of standard radiographic projections for determining acetabular cup position and to compare 2 radiographic methods for calculation of the angle of lateral opening of the acetabular cup. STUDY DESIGN: In vitro radiographic study. METHODS: Acetabular components were mounted on a custom-built inclinometer. The effect of varying the angles of lateral opening, inclination, version, and centering of the x-ray beam on the radiographic appearance of the cup was investigated. The angle of lateral opening was calculated trigonometrically after direct measurement and by means of computer-aided image analysis. RESULTS: Using a ventrodorsal radiograph, the computer-aided measurement of angle of lateral opening was accurate to within 5 degrees when the true angle of lateral opening was > or = 40 degrees. In the case of direct measurement, the calculated angle was accurate to within 5 degrees only when the true angle was > or = 60 degrees. An increasing angle of inclination was associated with reduced accuracy of calculation of the angles of lateral opening and version. Standard radiographic assessment of acetabular version and inclination was not found to be clinically useful. The displacement of the x-ray beam, which would cause significant error in the determination of lateral opening, is unlikely to be exceeded in practice. Cup size had no significant effect on the accuracy of the results. CONCLUSIONS: Computer-aided image analysis can be used to calculate angles of lateral opening to within 10 degrees throughout the range of acetabular positions seen in practice and is appropriate for postoperative documentation of cup position. The angles of inclination and version should be interpreted with caution.     

Acetabular ventroversion with double pelvic osteotomy versus triple pelvic osteotomy: a cadaveric study in dogs

Objective: To determine which of 3 different plate angles (20°, 25°, 30°) used in double pelvic osteotomy (DPO) would result in the most similar acetabular angle (AA) achieved with a 20° triple pelvic osteotomy (TPO) technique in dogs. Study Design: Experimental anatomic study. Animals: Cadaveric canine pelves (n=8). Methods: Transverse plane computed tomographic images of cadaveric pelves with intact sacroiliac joints, mounted in a custom jig, were made (baseline) and again after DPO (20°, 25°, 30°) and TPO (20°) and pelvic angles measured in 6 transverse planes. Pelvic angles of the 3 DPO techniques were compared with TPO using concordance correlation to determine which DPO angle resulted in an acetabular ventroversion angle closest to TPO. Results: Mean ± SD AAs were 32.89 ± 2.23 (baseline), 47.39 ± 4.39 (20° DPO), 51.43 ± 5.06 (25° DPO), 54.75 ± 4.38 (30° DPO), and 50.20 ± 5.76 (20° TPO). Concordance correlations for the AA compared with 20° TPO were 0.027 (baseline), 0.721 (20° DPO), 0.902 (25° DPO), and 0.593 (30° DPO). A concordance correlation of ≥0.8 indicates good correlation. Conclusions: A 25° DPO is most similar in acetabular ventroversion to 20° TPO (concordance correlation, 0.902).     

Comparison of radiographic and anatomic femoral varus angle measurements in normal dogs

Objective— To determine if the clinically practiced method of radiographic femoral varus angle (R-FVA) measurement is repeatable, reproducible, and accurate.
Study Design— Radiographic and anatomic study.
Animals/Sample Population— Normal Walker hound cadavers (n=5) and femora (n=10).
Methods— Cadavers were held in dorsally-recumbent and torso-elevated positions as 3 craniocaudal radiographs were made of each femur, by each of 2 different technicians. Femora were then harvested for direct measurement of anatomic femoral varus angle (A-FVA). R-FVA was measured on each radiograph by each of 3 examiners on 3 separate occasions. Intra-observer (repeatability) and inter-observer (reproducibility) variance in R-FVA measurement and the strength of relationship between R-FVA and A-FVA (accuracy) were determined.
Results— Mean (±SD) A-FVA was 5.2±2.1° (range, 2.4–8.2°). Mean (±SD) R-FVA was 5.8±1.0° (range, 2.7–9.6°). Intra-observer variance (range: 11–16%) and inter-observer variance (16%) were acceptable. The strength of relationship between measured R-FVA and A-FVA (maximum adjusted R²<0) was unacceptably low regardless of observer, patient position, or radiographic technician.
Conclusion— R-FVA measurement was repeatable and reproducible, but not statistically accurate in predicting A-FVA in these 5 normal Walker hounds. The detected inaccuracy may be real or the result of a selection bias for normal dogs obscuring the true relationship.
Clinical Relevance— R-FVA may not be an accurate method of femoral varus measurement in dogs with A-FVA<10°. Using Slocum's criteria for distal femoral osteotomy (R-FVA>10°), the procedure would not have been erroneously performed in any of the normal dogs of this study.     

Determination of Pelvic Limb Alignment in the Large‐Breed Dog: A Cadaveric Radiographic Study in the Frontal Plane

Objectives— To report a method for radiographic determination of the mechanical axis of the canine pelvic limb and its relationship to the joints and bone axes. To report reference ranges for the relationships between the axes of the pelvic limb and for joint position relative to the pelvic limb axis. Study Design— Cadaveric radiographic anatomic study. Animals— Pelvic limbs (n=101) from normal midsized to large breed dogs; tibiae (n=105) from dogs with cranial cruciate ligament disease (previous study). Methods— Extended full‐limb radiography was performed and images analyzed to determine: mechanical joint reference angles (femur, tibia), pelvic limb axis, tibiofemoral and metatarsotibial angle, mechanical axis—femur/metatarsus angle, and mechanical axis deviation (MAD) of the stifle/tarsus. Results— Mean mechanical angles were: lateral proximal femoral (103.7°±5.4°), lateral distal femoral (98.6°±2.5°), medial proximal tibial (92.2°±1.8°), medial distal tibial (95.9°±2.2°), tibiofemoral (9.1° varus ±2.8°), metatarsotibial (0.6° valgus ±2.1°). Mean mechanical axis—femur and—metatarsus angles were 5.6° (±1.7°) and 2.9° (±1.5°), respectively. Mean MAD of the stifle and tarsus were 3.6% (±1.1%) and 1.2% (±0.6%), respectively. Tibial angles were not different between dogs with and without cranial cruciate ligament disease. Conclusions— Mechanical axes of the canine pelvic limb and their relationship to the joints can be determined by full‐limb radiography. Clinical Relevance— Techniques and reference ranges may be useful for diagnosis, surgical planning, and postoperative assessment of pelvic limb deformities.     

Measurement of femoral angles in four dog breeds

Objective— To develop a standard method of measurement for femoral angles and report values for normal Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers.
Study Design— Retrospective evaluation of canine pelvis and femoral radiographs.
Sample Population— Radiographs of Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers (n=100 for each breed).
Methods— Anatomic lateral distal and proximal femoral angle, mechanical lateral distal and proximal femoral angle, and femoral angle of inclination were measured from radiographs.
Results— For the 4 breeds (Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers, respectively) anatomic lateral distal femoral angles were 97°, 97°, 94°, and 98°; mechanical lateral distal femoral angles were 100°, 100°, 97°, and 100°; anatomic lateral proximal femoral angles were 103°, 98°, 101°, and 96°; mechanical lateral proximal femoral angles were 100°, 95°, 97°, and 93°; and inclination angles were 134°, 134°, 132°, and 137°. Labrador Retrievers, Golden Retrievers, and Rottweilers had significantly higher values for both anatomic and mechanical lateral distal femoral angle than German Shepherds. Anatomic and mechanical lateral proximal angles were greatest for Labrador Retrievers and lowest for Rottweilers.
Conclusion— Anatomic and mechanical femoral joint angles vary between breeds of dogs.
Clinical Relevance— Values for femoral joint angles may be clinically useful for angular limb deformity diagnosis, treatment, and assessment.     

Influence of limb positioning and measurement method on the magnitude of the tibial plateau angle

OBJECTIVE: To evaluate the effect of limb positioning and measurement technique on the magnitude of the radiographically determined tibial plateau angle (R-TPA). STUDY DESIGN: In vitro study, R-TPA was determined by 6 blinded observers and image measurement software. ANIMALS: Five canine cadaver hind limbs. METHODS: The legs were positioned on a custom-made positioning device simulating a radiographic tabletop technique in lateral recumbency. True lateral positioning was defined by superimposition of femoral and tibial condyles on the radiographic projection. Radiographs were taken while the specimens were relocated in a proximal, distal, caudal, and cranial direction with respect to the radiographic beam. For each specimen, 25 different radiographic views were obtained and 6 blinded observers determined the radiographic TPA using 2 different methods. The conventional method used precise anatomic landmarks to determine the tibial plateau. To simulate osteoarthritic changes complicating identification of these landmarks, the tangential method estimated the tibial plateau as the tangent to the central portion of the tibial plateau. After periarticular soft tissue dissection the anatomic tibial plateau angle (A-TPA) was determined. The A-TPA and the R-TPA were compared. RESULTS: The R-TPA significantly decreased as limb position with respect to the X-ray beam changed from cranial proximal to caudal distal. The maximal mean radiographic R-TPA difference was 3.6 degrees with the first and 5.7 degrees with the second method. Regardless of the method used there was no significant difference between A-TPA and R-TPA in the true lateral position. In the peripheral positions, however, significant differences between anatomic and radiographic TPA were seen. CONCLUSIONS: Limb positioning influenced the radiographic appearance of the tibial plateau and the magnitude of the measured TPA. Cranial and proximal positioning of the limb relative to the X-ray beam leads to overestimation whereas caudal and distal positioning leads to underestimation of the TPA. CLINICAL RELEVANCE: True lateral positioning of the tibia defined by superimposition of the femoral and tibial condyles should be used for accurate TPA determination before tibial plateau leveling osteotomy.     

Use of radiographic measurements in the evaluation of dogs with medial patellar luxation

This prospective study used radiographic techniques to evaluate the inclination, Norberg, quadriceps and femoral varus angles, and the patellar position in dogs with developmental medial patellar luxation. The study also compared these measurements pre- and post-operatively to determine how they were affected by surgical procedures. Eighteen dogs with unilateral or bilateral luxation were used, and 4 groups were established according to luxation grade. Except for the quadriceps angle, there was no difference among the groups preoperatively. Significant differences for the quadriceps angle were observed between Grades 1 and 3, and between Grades 2 and 3. The Norberg and femoral varus angles and the patellar position showed no changes between pre- and postoperative groups. However, measurements of the preoperative quadriceps angle and postoperative inclination angle may be useful for evaluating dogs with grade-3 luxation. Further studies using other imaging techniques are required in dogs with severe grade-4 luxation due to the difficulty in obtaining a good radiographic position.     

Canine uncemented porous-coated anatomic total hip arthroplasty: results of a long-term prospective evaluation of 50 consecutive cases

OBJECTIVE: To evaluate the long-term clinical and radiographic results of a canine uncemented porous-coated anatomic (PCA) total hip arthroplasty (THA). STUDY DESIGN: Prospective study of consecutive clinical patients using survival analysis. ANIMALS: Forty-one dogs that underwent PCA THA; nine had bilateral PCA THA (50 prostheses). METHODS: Gait observation, orthopedic examination, and radiographic assessment were conducted before THA, 6 months after THA, and yearly thereafter. A zonal analysis system was used to document osseous changes in the femur and the acetabulum. Acetabular cup and femoral stem subsidence and migration, femoral canal fill, and implant orientation were measured. Survival analysis of the procedure was conducted. RESULTS: Long-term follow-up was available for 37 dogs (46 prostheses). The median follow-up was 63 months. Limb function was normal for 37 limbs and abnormal for 9 limbs because of dislocation (n = 3), lumbosacral disease (n = 2), degenerative myelopathy (n = 1), autoimmune disease (n = 1), brain tumor (n = 1), or osteosarcoma of the femur (n = 1). All prosthetic stems and cups were fixed by bone ingrowth fixation. Osteolysis was not observed. Bone infarction occurred in five femoral canals (four dogs). The 6-year survival rate for the procedure was 87% (95% confidence interval, 72%-96%). CONCLUSIONS: Long-term fixation of the uncemented PCA acetabular cup and stem is successful in dogs, and long-term clinical function is excellent.     

Measurement of the femoral neck anteversion angle in the dog using computed tomography

Simple and accurate limb and pelvic conformation evaluation using computed tomography (CT) can be useful in planning canine hip dysplasia (CHD) treatment and in helping to understand the pathogenesis of osteoarthritis and CHD. The objectives of this study were to describe a new method for femoral neck anteversion angle (FNA-angle) measurement in CT, and to compare it to the established radiographic standard biplanar method. The hips of 23 Estrela Mountain Dogs were evaluated using radiography and CT and their FNA-angles were determined by performing two CT examinations and with one radiographic measurement session. The intra-class correlation coefficient (ICC) was used to evaluate the repeatability (agreement between the two CT sessions, ICC=0.92) and reproducibility (agreement between each CT and radiographic session, ICC=0.91 in both cases) of the CT FNA-angle measurement method. This study suggests that CT FNA-angle measurement method is reliable and can be used in CT hip studies with confidence.     

RADIOGRAPHIC AND COMPUTED TOMOGRAPHIC DETERMINATION OF FEMORAL VARUS AND TORSION IN THE DOG

Diagnosis and quantification of femoral varus and femoral torsion using radiographs is technically challenging due to the difficulty in determining proper positioning. The purpose of this study is to describe a computed tomographic technique for determination of femoral varus and femoral torsion and to compare this technique, and standard radiography, to anatomic preparation, for the measurement of femoral varus and femoral torsion in normal dogs. Nine canine cadavers, visually and radiographically free of orthopedic disease of the hip and stifle joints, were utilized for analysis. Femoral varus was determined using a craniocaudal radiograph, a craniocaudal radiograph obtained after confirming accurate positioning using horizontal beam fluoroscopy, and computed tomography (CT). Femoral torsion (expressed as angle of version) was determined using an axial radiographic projection obtained from distal to proximal and CT. Each femur was dissected free of soft tissues, and direct determination of femoral varus and femoral torsion was performed using digital photographic images. All radiologic and photographic images were digitally measured to quantify the magnitude of femoral varus and femoral torsion. For femoral varus, no difference ( P =0.149) between the three different imaging techniques and the anatomic preparation was identified. For femoral torsion, no difference ( P =0.059) between the two imaging techniques and the anatomic preparation was identified. Well positioned radiographs and the described computed tomographic method are both as accurate as anatomic preparation for the measurement of both femoral varus and femoral torsion in normal dogs.     

Interobserver Variation in the Measurement of the Femoral Angle of Inclination

Ventrodorsal radiographs of the hips of 12 dogs were obtained. Copies of the radiographs were circulated to eight people with instructions for measurement of the angle of inclination of the femoral head and neck by two methods. A high degree of interobserver variation was found with both methods of measuring the angle of inclination.     

Evaluation of transpulmonary ultrasound dilution cardiac output in piglets: accuracy,precision and trending ability with room temperature injectate

ObjectiveTranspulmonary ultrasound dilution (TPUD) is a minimally invasive technique to measure cardiac output (CO) using a 1 mL kg^–1 isotonic 37 °C saline injectate indicator. The objective was to evaluate the performance of TPUD using a room temperature saline injectate.Study designProspective experimental trial.AnimalsA total of seven anesthetized male Yorkshire piglets.MethodsPiglets aged 1 month and weighing 7.7–9.0 kg were anesthetized with detomidine–ketamine–hydromorphone–isoflurane and a pulmonary artery flow probe (PAFP) placed via a median sternotomy. The thoracic cavity remained open during measurement of CO by PAFP and TPUD. The TPUD indicators of 1 mL kg^–1 0.9% saline at 37 °C and 20 °C were compared during infusions of phenylephrine and dobutamine, blood withdrawal and replacement. Bias, limits of agreement (LoAs) and percentage error (PE) between each iteration of PAFP and TPUD were measured with Bland–Altman plots. Trending ability via concordance, angular bias and radial LoA were compared.ResultsBland–Altman plots showed negligible bias with varying LoAs. PEs of 22% and 38% were found for 37 °C and 20 °C saline injectates, respectively. In the four-quadrant plots, the concordance rate was 94% and 100% for measurements obtained with 37 °C and 20 °C saline injectates, respectively. Angular bias for both were < ±5 °, with radial LoA < ±7 °.ConclusionsTPUD was accurate when using 1 mL kg^–1 of isotonic saline at 37 °C in a range of CO within 0.2–0.8 L minute^–1, and it reliably tracked positive and negative changes in CO. Room temperature (20 °C) indicator was less accurate but equally able to track direction of changes in CO.Clinical relevanceThe use of room temperature injectates allows an easy, readily available clinical application of TPUD CO monitoring while preserving the trending ability of the monitor.     

The Angle of Inclination of the Canine Femoral Head and Neck

Two different methods of measuring the angle of inclination of the femoral head and neck were made and compared on 108 dogs. Resultant angles were not related to age, sex, or breed. The angle of inclination is related to technique of measurement, positioning, and anteversion angle.     

Measurements of Femoral Neck-Shaft Angle in the Growing Beagle

The angles of inclination and anteversion were measured radiographically in 8 beagles, at 4-week intervals from 14 to 38 weeks of age, the time of radiographic physeal closure. Minimal changes in the femoral neck-shaft angles were observed during this observation period. The results indicate that surgical correction of altered femoral neck-shaft angles could be proposed at any time after 3 months of age in the beagle breed.     

The effects of femur and implant position on the radiographic assessment of total hip femoral implants in dogs

OBJECTIVE: To determine the effect of femur positioning and femoral implant placement on the radiographic assessment of total hip femoral implants in dogs. STUDY DESIGN: Cadaveric study. ANIMALS: Five canine femurs. METHODS: Five canine femurs were fitted with total hip implants, in predetermined locations, postmortem. Each femur was moved through a defined range of motion and radiographed at specific intervals. Radiographs were then digitized, and implant position was measured using previously described methods. Regression analysis was conducted to determine whether varied femoral position resulted in a consistent (linear) pattern of change in the value of each particular measurement. RESULTS: Change in the position of the femur relative to the film cassette caused significant variation in the perceived position of the implant. The placement of the implant within the femur determined which measurements were affected and to what degree. CONCLUSIONS: The information obtained from standard clinical radiographs and conventional methods of quantitative analysis does not consistently provide an accurate assessment of the placement of the femoral implant within the femoral canal. Such data cannot be used to correlate implant position with implant failure.