Multivariate analysis of morphometric characteristics to evaluate risk factors for cranial cruciate ligament deficiency in Labrador retrievers

Objectives: To determine the combination of conformation characteristics of the pelvic limbs of Labrador Retrievers that best discriminates between limb at risk to develop cranial cruciate ligament (CCL) disease and limbs at low risk using radiographs, computerized tomography (CT) images, and dual‐energy X‐ray absorptiometry (DEXA). Study Design: Cross‐sectional clinical study. Animals: Twelve clinically normal and 9 unilaterally CCL‐deficient Labrador Retrievers. Methods: The pelvic limbs of normal dogs were considered as non‐predisposed to CCL disease and the contralateral limbs of CCL‐deficient dogs as predisposed. Conformation variables, obtained from femur and tibial radiographs, pelvic limb CT images and DEXA studies, of predisposed pelvic limbs were compared with the conformation variables from pelvic limbs of the low‐risk group. An ROC curve analysis was used to assess the discriminating properties of conformation variables for several combinations. Results: We determined that a combination of tibial plateau angle (TPA) and femoral anteversion angle (FAA) measured on radiographs was optimal for discriminating predisposed and non‐predisposed limbs for CCL disease in Labrador Retrievers. Conclusions: Assessing predisposition to CCL disease with a combination of conformational measurements is better than using univariate parameters. In the future, TPA and FAA may be used to screen dogs suspected of being susceptible to CCL disease.     

Distribution of power across the hind limb joints in Labrador Retrievers and Greyhounds

OBJECTIVE: To quantify angular excursions; net joint moments; and powers across the stifle, tarsal, and metatarsophalangeal (MTP) joints in Labrador Retrievers and Greyhounds and investigate differences in joint mechanics between these 2 breeds of dogs. ANIMALS: 12 clinically normal dogs (6 Greyhounds and 6 Labrador Retrievers) with no history of hind limb lameness. PROCEDURE: Small retroreflective markers were applied to the skin over the pelvic limb joints, and a 4-camera kinematic system captured data at 200 Hz in tandem with force platform data while the dogs trotted on a runway. Breed-specific morphometric data were combined with kinematic and force data in an inverse-dynamics solution for stance-phase net joint moments and powers at the stifle, tarsal, and MTP joints. RESULTS: There were gross differences in kinematic patterns between Greyhounds and Labradors. At the stifle and tarsal joints, moment and power patterns were similar in shape, but amplitudes were larger for the Greyhounds. The MTP joint was a net absorber of energy, and this was greater in the Greyhounds. Greyhounds had a positive phase across the stifle, tarsal, and MTP joints at the end of stance for an active push-off, whereas for the Labrador Retrievers, the only positive phase was across the tarsus, and this was small, compared with values for the Greyhounds. CONCLUSIONS AND CLINICAL RELEVANCE: Gross differences in pelvic limb mechanics are evident between Greyhounds and Labrador Retrievers. Joint kinetics in specific dogs should be compared against breed-specific patterns.     

Comparison of tibial plateau angle between clinically normal Greyhounds and Labrador Retrievers with and without rupture of the cranial cruciate ligament

OBJECTIVE: To compare tibial plateau angle (TPA) between Greyhounds without damage to the cranial cruciate ligaments and Labrador Retrievers with and without damage to the cranial cruciate ligaments. DESIGN: Clinical study. ANIMALS: 87 client-owned dogs and 15 research colony Greyhounds. PROCEDURE: Standing position, horizontal-beam radiography was performed on Greyhounds and unaffected Labrador Retrievers to determine standing TPA. Lateral radiography of the stifle joint was performed on all dogs to determine traditional TPA. Age and body weight were recorded for unaffected and affected Labrador Retrievers. RESULTS: Greyhounds had mean standing TPA of 1.56 degrees and mean traditional TPA of 22.50 degrees. Unaffected Labrador Retrievers had mean standing TPA of 3.52 degrees and traditional TPA of 27.97 degrees. Affected Labrador Retrievers had mean traditional TPA of 25.55 degrees. No significant difference was found in mean standing TPA between Greyhounds and unaffected Labrador Retrievers. Standing TPAs in Greyhounds and unaffected Labrador Retrievers were not significantly different from a plane drawn parallel to the ground. Significant differences in traditional TPAs were detected among all 3 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Greyhounds had mean traditional TPA of 22.50 degrees; similar angles should be considered normal for dogs. Although affected Labrador Retrievers had mean traditional TPA that was significantly greater than that of Greyhounds, the steepest TPA was found in unaffected Labrador Retrievers. Because Greyhounds and unaffected Labrador Retrievers had similar standing TPAs, we conclude that although TPA may be associated with damage to the cruciate ligaments, many dogs with a steep TPA do not develop cruciate ligament disease.     

Effect of conformation of the distal portion of the femur and proximal portion of the tibia on the pathogenesis of cranial cruciate ligament disease in dogs

OBJECTIVE: To evaluate mediolateral radiographic views of stifle joints to identify conformational differences between athletically sound dogs and dogs with cranial cruciate ligament disease (CCLD). SAMPLE POPULATION: Radiographic images of 50 stifle joints of 43 dogs with surgically confirmed CCLD and 50 stifle joints of 38 dogs without clinical signs of stifle joint disease. PROCEDURES: Mediolateral radiographic views of stifle joints were obtained, and long axes of the femur, tibia, and femoral condyles were measured. Angles between long axes of the femur and femoral condyle and between long axes of the femur and tibia were measured. Circles were drawn representing the joint surface of femoral condyles (circle 1), area of contact on the tibial plateau (circle 2), and femoral trochlea (circle 3). Radii of circles 1, 2 (line F), and 3 were measured. Distances between midpoints of circles 1 and 2 (line K) and between midpoint of circle 2 and most cranial aspect of the tibial tuberosity (line G) were measured. To evaluate differences in conformation that could lead to CCLD, quotients derived from measurements were created for comparison; angles were compared between dog groups. RESULTS: Significant differences were found in the quotients created by the lengths of lines G and F and lines G and K between dogs with and without CCLD. CONCLUSIONS AND CLINICAL RELEVANCE: No anatomic differences were detected in the distal portion of the femur between dogs with and without CCLD. Development of the tibial tuberosity and shape (convexity) of tibial condyles may be relevant in the pathogenesis of CCLD.     

Biomechanics of tibial plateau leveling of the canine cruciate-deficient stifle joint: a theoretical model

OBJECTIVE: To evaluate the effect of tibial plateau leveling on the biomechanics of the canine stifle. STUDY DESIGN: Analysis of a 3-dimensional (3-D) anatomically accurate theoretical model of the canine stifle. METHODS: A 3-D, 3-segment mathematical model of the normal canine stifle was modified to simulate the effect of rotation of the tibial plateau during tibial plateau leveling osteotomy (TPLO). The model examined the normal stifle, the stifle with a tibial plateau angle (TPA) of 0 degrees, and the stifle with a TPA of 5 degrees. Analysis of the models at 10 consecutive equally spaced positions during the stance phase yielded data such as ligament forces and joint reaction forces at each position. RESULTS: Rotation of the tibial plateau to a TPA of 0 degrees almost eliminates forces in the cranial cruciate ligament (CCL) throughout the stance phase. Rotation to a TPA of 5 degrees did not, however, substantially decrease the load in the CCL. Both procedures increased the load in the caudal cruciate ligament (CaCL). CONCLUSIONS: Cranial tibial thrust (CTT) is converted into caudal tibial thrust when the TPA is 0 degrees ; however, rotating the plateau to a TPA of 5 degrees does not eliminate the CTT. CLINICAL RELEVANCE: The TPLO procedure performed as currently recommended (rotating the tibial plateau to a TPA of 5 degrees) may not eliminate the CTT, but only reduce it. Both TPLO procedures evaluated here were found to increase the load in the CaCL.     

Effect of tibial plateau leveling on cranial and caudal tibial thrusts in canine cranial cruciate-deficient stifles: an in vitro experimental study

OBJECTIVES--To investigate the effect of tibial plateau leveling (TPL) on tibial subluxation and tibial axial rotation; to determine the minimal tibial plateau rotation (MinTPR) angle that provides stifle stability; and to evaluate caudal cruciate ligament (CaCL) strain following tibial plateau rotation in cranial cruciate ligament (CrCL)-deficient stifles. ANIMALS--Fifteen canine cadaver hind limbs. METHODS--Tibial subluxation was measured from lateral radiographs in intact, loaded stifles and after sequential CrCL transection, MinTPR, TPL, and CaCL transection. The MinTPR angle was determined using a custom-made hinge plate and compared with the TPL angle. Tibial axial rotation was evaluated in CrCL-deficient stifles before and after TPL. Finally, CaCL strain was recorded in intact, loaded stifles, and following MinTPR, TPL, and tibial plateau over-rotation (MaxTPR) using a force probe. RESULTS--Cranial tibial subluxation in CrCL-deficient stifles was eliminated with TPL. Tibial plateau rotation, however, induced caudal tibial subluxation, which significantly increased from MinTPR to TPL before and after CaCL transection. The MinTPR angle was 6.5 degrees +/- 0.9 degrees less than the TPL angle (P <.05). Tibial internal rotation decreased significantly after TPL in CrCL-deficient stifles. Finally, CaCL strain increased with increasing tibial plateau rotation. CONCLUSIONS--This study suggests that, during stance phase, TPL transforms cranial tibial thrust into caudal tibial thrust, thereby stabilizing the stifle in the cranio-caudal plane via the constraint of the CaCL. The increase in CaCL stress, which results from tibial plateau rotation, could predispose the CaCL to fatigue failure and therefore would caution against tibial plateau over-rotation.     

Are sound dogs mechanically symmetric at trot? No, actually.

A two-year-old, sound Labrador Retriever was determined to be 'right hind limb dominant' by comparison of total hind limb moments of support using inverse dynamics. Net joint moments at the hip, tarsal and meta-tarsophalangeal joints were larger on the right side. Vertical joint reaction forces at the stifle were larger on the right, and horizontal stifle joint reaction forces were smaller on the right. The crus segment was more cranially inclined on the right side through most of stance, but the angle of the resultant stifle joint reaction force vector against the long axis of the crus segment was identical between the right and left sides. The cranially inclined crus segment orientation on one side, coupled with the larger vertical joint reaction force, may result in an internal asymmetry in stifle joint mechanics, although the effects of this on cruciate ligament stresses remain to be determined.     

Radiographic measurement of canine tibial angles in the sagittal plane

Objective— To describe a method for radiographic measurement of the mechanical joint angles of the tibia in the sagittal plane and report reference ranges for a population of dogs with cranial cruciate ligament disease, and specifically for Labrador Retrievers.
Study Design— Retrospective evaluation of radiographs.
Animals— Canine tibia (n=150) of dogs evaluated for cranial cruciate ligament disease; 104 tibiae were from Labrador Retrievers, 46 tibiae were from other medium- to large-breed dogs.
Methods— Medial-lateral radiographs were used to establish anatomic landmarks and measure the mechanical cranial distal tibial angle (mCrDTA) and mechanical caudal proximal tibial angle (mCaPTA).
Results— For all tibiae mean mCrDTA was 81.6° and mCaPTA, 63.6°. For Labrador Retriever tibiae mean mCrDTA was 81.7° and mCaPTA, 63.8°. For non-Labradors, means mCrDTA was 81.5° and mCaPTA, 63°. Labrador Retrievers were significantly younger than non-Labradors in our study population. No significant differences were noted between Labrador Retrievers and non-Labradors for mCrDTA or mCaPTA and correlations between mCrDTA and mCaPTA were neither strong nor significant.
Conclusion— A method was established for radiographic measurement of mechanical joint angles of the canine tibia in the sagittal plane. Reference ranges are reported for a population of Labrador Retrievers and a population of non-Labradors with cranial cruciate ligament disease.
Clinical Relevance— Measurement method and reference ranges provided for mechanical tibial angles may be used to aid in diagnosis, surgical planning, and postoperative critique for hindlimb angular deformities.     

Inclination of the patellar ligament in relation to flexion angle in stifle joints of dogs without degenerative joint disease

OBJECTIVE: To measure the angles between the patellar ligament and the tibial plateau and between the patellar ligament and the common tangent at the tibiofemoral contact point (TFCP) throughout the full range of motion of the stifle joint in dogs and determine the flexion angles at which the patellar ligament is perpendicular to the tibial plateau or to the common tangent. SAMPLE POPULATION: 16 hind limbs from cadavers of 9 adult dogs without radiographically detectable degenerative joint disease. PROCEDURES: Mediolateral radiographic views of the stifle joints from full extension through full flexion were obtained (10 degrees increments). Angles between the tibial and femoral long axes (beta), between the patellar ligament and the tibial plateau gamma), and between the patellar ligament and the common tangent at TFCP (alpha) were measured. Data were analyzed via simple linear regression. RESULTS: In canine stifle joints, angles gamma and alpha decreased linearly with increasing flexion (angle beta). The patellar ligament was perpendicular to the tibial plateau and perpendicular to the common tangent at the TFCP at 90 degrees and 110 degrees of flexion, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: By use of the conventionally defined tibial plateau, data suggest that at approximately 90 degrees of flexion in stifle joints of dogs, shear force in the sagittal plane exerted on the proximal portion of the tibia shifts the loading from the cranial to the caudal cruciate ligament. Analyses involving the common tangent at the TFCP (a more anatomically representative reference point) identified this crossover point at approximately 110 degrees of joint flexion.     

Effect of trotting velocity on work patterns of the hind limbs of Greyhounds

OBJECTIVE: To quantify the effects of trotting velocity on joint angular excursions, net joint moments, and powers across the hind limb joints in Greyhounds. ANIMALS: 5 healthy Greyhounds with no history of lameness of the hind limbs. PROCEDURES: Small reflective markers were applied to the skin over the joints of the hind limbs, and a 4-camera kinematic system was used to record positional data at 200 Hz in tandem with force platform data while the dogs trotted on a runway at slow, medium, and fast velocities. Breed-specific morphometric data were combined with kinematic and force data in an inverse-dynamics solution for net joint moments and powers at the hip, stifle, tarsal, and metatarsophalangeal joints. RESULTS: Angle, moment, and power patterns at the various joints were conserved among the 3 velocities. With increasing velocity, moments and powers at the tarsal, stifle, and hip joints during the stance phase were increased in amplitude, whereas amplitudes during the swing phase were not. The main contributors to increased velocity were the hip extensors and stifle flexors during the early part of the stance phase and the tarsal extensors during the late part of the stance phase. CONCLUSIONS AND CLINICAL RELEVANCE: Increases in trotting velocity in Greyhounds do not alter the basic patterns of work and power for various joints of the hind limbs, but local burst amplitudes during the stance phase increase incrementally.     

Noninvasive determination of body segment parameters of the hind limb in Labrador Retrievers with and without cranial cruciate ligament disease

OBJECTIVE: To determine mass, center of mass (COM), and moment of inertia (ie, body segment parameters [BSPs]) of hind limb segments by use of a noninvasive method based on computerized tomography (CT) in Labrador Retrievers with and without cranial cruciate ligament (CCL) disease and to provide regression equations to estimate BSPs of normal, CCL-deficient, and contralateral hind limbs. ANIMALS: 14 clinically normal and 10 CCL-deficient Labrador Retrievers. PROCEDURES: Bone, muscle, and fat areas were identified via CT. Mass, COM, and moment of inertia were determined on the basis of tissue densities in the thigh, crus, and foot segments. Regression models were developed to determine predictive equations to estimate BSP on the basis of simple morphometric measurements. RESULTS: The thigh and crus of CCL-deficient limbs weighed less than in contralateral segments. Thighs weighed less in CCL-deficient than in normal limbs. The thigh moment of inertia was less in CCL-deficient than in contralateral limbs. The crural COM was located more distally in normal limbs, compared with other limbs. Predictive equations to estimate BSP varied by parameter, body segment, and limb status. CONCLUSIONS AND CLINICAL RELEVANCE: BSPs of the thigh and crus varied with segment and status of the hind limb in Labrador Retrievers with or without CCL disease. Equations to estimate BSP on the basis of simple morphometric measurements were proposed, providing a basis for nonterminal studies of inverse dynamics of the hind limbs in Labrador Retrievers. This approach may offer new strategies to investigate the pathogenesis of nontraumatic joint diseases.     

Kinematic gait analysis of the hind limb after tibial plateau levelling osteotomy and cranial tibial wedge osteotomy in ten dogs

This study identifies and compares the kinematic gait changes occurring in tibial plateau levelling osteotomy (TPLO) and cranial tibial wedge osteotomy (CTWO) limbs after transection of the cranial cruciate ligament (CrCL). Ten, healthy, adult beagle dogs were assigned to TPLO (five dogs) and CTWO (five dogs) groups. Hind limb kinematics were assessed, while dogs were trotted at speeds ranging from 2.0 to 2.3 m/s. The animals were evaluated preoperatively (prior to TPLO and CTWO surgery) and at both 8 and 12 weeks after surgery. Two-dimensional evaluation was synchronized to obtain the three-dimensional coordinates using the APAS motion analysis software. Gait patterns were assessed by measuring stifle, tibiotarsal joint angles and stifle joints angular velocity. Stifle and tibiotarsal joint functions were not affected by TPLO surgery, but stifle and tibiotarsal joint angles were changed, following CTWO surgery, compared with their preoperative values. The angular velocity patterns of CTWO were characterized by increased stifle joint extension velocity from the middle to end swing phase and decrease in the peak velocities (flexion) during swing phase. None of these changes was observed in the stance phase after the CTWO surgery. These kinematic results showed that dogs that underwent a CTWO procedure were more likely to have significantly hyperextended gait patterns of the swing phase postoperatively than the dogs that had a TPLO procedure for repair of a ruptured CrCL.     

Angle between the patellar ligament and tibial plateau in dogs with partial rupture of the cranial cruciate ligament

OBJECTIVE: To measure the angles between the patellar ligament and the tibial plateau and between the patellar ligament and the common tangent at the tibiofemoral contact point (TFCP) in stifle joints of dogs with partial rupture of the cranial cruciate ligament (CrCL) for comparison with data obtained for stifle joints in dogs with intact CrCLs. SAMPLE POPULATION: 60 stifle joints of 54 dogs with surgically confirmed partial CrCL rupture. PROCEDURES: Mediolateral radiographic views of the stifle joints were obtained, and the angles between the patellar ligament and the conventionally defined tibial plateau (angle gamma) and between the patellar ligament and the common tangent to the TFCP (angle alpha) were measured at incidental stifle joint flexion (angle beta) by 2 independent observers. Data underwent linear regression analysis and were compared with findings in joints of dogs without degenerative joint disease. RESULTS: In stifle joints of dogs with a partial rupture of the CrCL, angles gamma and alpha were 5 degrees and 2 degrees larger than each corresponding angle in healthy canine joints. At 100 degrees of flexion, the patellar ligament was perpendicular to the conventionally defined tibial plateau. At 110 degrees of flexion, the patellar ligament was perpendicular to the common tangent at the TFCP. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, stifle joints with partially ruptured CrCLs have marginally larger angles between the patellar ligament and the tibial plateau, compared with joints with intact CrCLs; at equivalent angles of flexion, comparatively greater shear force affects the CrCLs in stifle joints with partial CrCL ruptures.     

The effect of tibial plateau angle on ground reaction forces 4-17 months after tibial plateau leveling osteotomy in Labrador Retrievers

OBJECTIVE: To assess the relationship between postoperative tibial plateau angle (TPA) and ground reaction forces (GRFs) in Labrador Retrievers at least 4-months after tibial plateau leveling osteotomy (TPLO) surgery. STUDY DESIGN: A retrospective longitudinal study. ANIMALS: Thirty-two Labrador Retrievers with unilateral cranial cruciate ligament disease that had TPLO and concurrent meniscal surgery. METHODS: TPA and GRFs were measured pre- and > or = 4 months postoperatively. Preoperative GRFs, preoperative TPA, duration of injury, postoperative TPA and degree of rotation were each compared with postoperative GRFs using correlation analysis. Dogs were also grouped by postoperative TPA and compared using 1-way analysis of variance (ANOVA). Postoperative function was compared with meniscal release/meniscectomy, patient age, sex, body weight and follow-up time using ANOVA. RESULTS: No significant relationship was found between preoperative GRFs, preoperative TPA, duration of injury, postoperative TPA, degree of rotation, or meniscal release/meniscectomy and postoperative function. Mean preoperative GRFs for all dogs were 28.8 +/- 9.5 for peak vertical force (PVF) and 9.3 +/- 3.1 for peak vertical impulse (VI). Mean postoperative GRFs for all dogs were 40.4 +/- 5.0 for PVF and 14.1 +/- 1.9 for VI. CONCLUSIONS: No statistically significant relationship was found between postoperative TPA and GRFs after TPLO > or = 4 months after surgery, where the postoperative angle was between 0 and 14 degrees. No significant relationship was found between the preoperative TPA and postoperative function. CLINICAL RELEVANCE: Limb function in Labrador Retrievers was not affected by postoperative TPA and re-operation for cases with a postoperative TPA between 0 and 14 degrees is not recommended.     

Reliability of goniometry in Labrador Retrievers

OBJECTIVE: To evaluate the reliability of goniometry by comparing goniometric measurements with radiographic measurements and evaluate the effects of sedation on range of joint motion. ANIMALS: 16 healthy adult Labrador Retrievers. PROCEDURE: 3 investigators blindly and independently measured range of motion of the carpus, elbow, shoulder, tarsus, stifle, and hip joints of 16 Labrador Retrievers in triplicate before and after dogs were sedated. Radiographs of all joints in maximal flexion and extension were made during under sedation. Goniometric measurements were compared with radiographic measurements. The influence of sedation and the intra- and intertester variability were evaluated; 95% confidence intervals for all ranges of motion were determined. RESULTS: Results of goniometric and radiographic measurements were not significantly different. Results of measurements made by the 3 investigators were not significantly different. Multiple measurements made by 1 investigator varied from 1 to 6 degrees (median, 3 degrees) depending on the joint. Sedation did not influence the range of motion of the evaluated joints. CONCLUSIONS AND CLINICAL RELEVANCE: Goniometry is a reliable and objective method for determining range of motion of joints in healthy Labrador Retrievers.     

Synovial tumours in dogs

The morphological characteristics, breed predispositions, site predilections and behaviour of three of the most common types of synovial tumours were discussed. Synovial histiocytic sarcoma represents 50% of synovial tumours, occurring in breeds predisposed to histiocytic sarcoma, and has a poor prognosis. Their histological appearance is similar to histiocytic sarcomas occurring elsewhere. The stifle is the most common site; dogs with ruptured cranial cruciate ligament are predisposed. Synovial cell sarcoma represents 15% of synovial tumours in dogs. They have non-specific spindle cell morphology, and can only be distinguished using cytokeratin immunohistochemistry, which will label a small percentage of the spindle cells. Amputation is often curative, but metastases can occur. Synovial myxoma represents 20% of synovial tumours in dogs. They have a characteristic morphology of myxomatous nodules filling the joint cavity and sometimes extending into the surrounding tissues, including bone. Labrador Retrievers and Doberman Pinschers are predisposed, and the stifle and digit are the most common sites. Prognosis is good; even with incomplete excision some dogs survive years without progression or metastasis. Histopathological examination of synovial tumours is essential to determine the course of treatment, and prognosis.     

Use of the proximal portion of the tibia for measurement of the tibial plateau angle in dogs

OBJECTIVE: To determine whether the canine tibial plateau angle (TPA) can be accurately measured from lateral radiographic views of the stifle joint that include only the proximal portion of the tibia. SAMPLE POPULATION: 282 lateral radiographic views of the stifle joint from 128 dogs. PROCEDURE: 236 radiographs were obtained from 102 dogs with no stifle joint disease, and 46 were obtained from 26 dogs with cranial cruciate ligament rupture. Radiographs were digitized. Tibial plateau angles were determined by measuring the angle between the intersection of the tibial plateau slope line and perpendiculars to 4 tibial axes. The gold standard TPA was based on a reference axis that used the entire length of the tibia and was determined by the line connecting the midpoint of the tibial intercondylar eminence and the center of the talus. Tibial plateau angle1, TPA2, and TPA3 were based on tibial axes that were determined by use of only the proximal portion of the tibia. RESULTS: TPA determined on the basis of the shortest proximal reference axis (TPA1) was not accurate. However, as the length of the reference axis increased, reliability of the TPAs obtained from proximal reference axes improved, and their correlations with the gold standard TPA increased (r = 0.78, 0.86, and 0.92 for TPA1, TPA2, and TPA3, respectively). Equations obtained by regression analysis allowed estimation of the gold standard TPA with some degree of accuracy. CONCLUSIONS AND CLINICAL RELEVANCE: Use of a proximal reference axis to calculate TPA may be an alternative to a calculation based on the full-length axis.     

Stifle joint osteoarthritis at the time of diagnosis of cranial cruciate ligament injury is higher in Boxers and in dogs weighing more than 35 kilograms

Osteoarthritis is a ubiquitous disease in dogs. The purpose of this retrospective study was to characterize the severity and distribution of osteoarthritis (OA) within the joint and to identify differences among dog breeds in the severity of OA in the cranial cruciate ligament (CCL)‐deficient stifle joint. Radiographs of 240 stifles from 51 Boxers, 66 German Shepherds, 100 Labrador Retrievers, and 23 Siberian Huskies with confirmed CCL rupture were included. Radiographs of the stifle joint were evaluated and OA severity was graded at 33 sites within and around the joint, and patella alta was graded as present or absent for a potential total stifle OA score of 100. Osteophyte size was correlated to OA severity score. Total OA scores were calculated and compared within and between breeds globally as well as at each joint site. Dogs weighing >35 kg had a higher total OA score than those weighing <35 kg. Osteoarthritis scores were highest at the apical patella, proximolateral tibia, and sesamoid bones, corresponding to the proximal, lateral, and caudal aspects of the joint, respectively. No statistically significant differences were found among the mean OA scores of various stifle joint regions. Boxer dogs had a higher total OA score than other breeds. We concluded that dogs have a consistent distribution pattern of OA within the stifle joint after CCL injury. Radiographic OA is more severe in the proximal, lateral, and caudal aspects of the joint. Boxers had more severe OA than the other breeds evaluated in the study.     

Radiographic assessment of the progression of osteoarthrosis in the contralateral stifle joint of dogs with a ruptured cranial cruciate ligament

The formation and progression of osteoarthrosis in the unaffected contralateral stifle joints of 14 dogs with a unilateral cranial cruciate ligament rupture were monitored radiographically in terms of a global score and the scores for 10 parameters specific for the stifle joint. The dogs were examined initially and six and 12 months later by three observers, and the variability between the observers' scores was also assessed. The score for osteophytes at the tibial attachment site of the ligament was the most reliable parameter, and that for the increase in femoropatellar joint space was the least reliable. In the contralateral stifle joints there were significant increases after six and 12 months in osteophyte formation caudal to the tibial plateau, and in subchondral sclerosis of the tibial plateau and of the long digital extensor muscle groove. These three parameters progressed more regularly during the disease process than the other parameters. The global osteoarthrosis score of the contralateral stifle joint was an important risk factor for sustaining a rupture of the cranial cruciate ligament in that joint during the next six months.     

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.