Background: Medial patellar luxation (MPL) is one of the commonest orthopaedic diseases in small dog breeds. Although the bone deformities associated with canine medial patellar luxation are described in numerous studies, the pathogenesis of the condition is still disputable. What is more, there is no categorical evidence that luxation of the patella is associated to a shallow trochlear groove as no objective method for determination of trochlear depth and shape has been proposed. The aim of the present study was to evaluate the depth and shape of femoral trochlear groove on radiographs obtained from healthy dogs and dogs affected with grade II and grade III MPL.Materials, Methods & Results: A total of 45 dogs (33 with MPL and 12 healthy) from 4 small breeds (Mini-Pinscher, Pomeranian, Chihuahua and Yorkshire terrier) were included in the study. After deep sedation, stifle radiographs were obtained in tangential projection (skyline view). The dogs were positioned in ventral recumbency, the examined stifle bent as much as possible, and the central beam focused on the patella between femoral condyles. Six morphometric parameters associated with the onset of trochlear dysplasia similar to those used in human medicine were measured: trochlear sulcus angle (SA), lateral and medial trochlear inclination angles (LTI; MTI), trochlear groove depth (TD), patellar thickness (PaT) and the ratio between trochlear depth and patellar thickness (PaT/TD). The non-parametric Mann-Whitney test was used for evaluation of differences between healthy joints and those affected with grade II and III MPL. The association between measured variables was evaluated via the Spearman’s rank-order correlation. TD was greater in healthy joints as compared to those affected with MPL grade II and III (P < 0.001). In healthy stifles, PaT value exceeded significantly (P < 0.01) that in joints with grade III MPL. The TD/PaT ratio was significantly greater in healthy joints vs both those with grade II (P < 0.01) and grade III MPL (P < 0.001). In healthy joints, there was a significant negative relationship (rho –0.508; P = 0.0113) between SA and TD: smaller sulcus angles corresponded to deeper trochleas. This correlation was even stronger in joints with patellar luxation (rho –0.723; P < 0.0001). The LTI and MTI showed a very strong positive correlation in healthy joints (rho 0.854; P < 0.0001) and at the same time, lack of significant association in joints affected with MPL (rho 0.163; P = 0.327 for grade II MPL and rho 0.175; P= 0.448 for grade III MPL) was demonstrated. The altered trochlear shape and depth were more pronounced in joints with grade III MPL. As MPL grade increased, the SA became statistically significantly greater. In grade III MPL it was accompanied with considerably reduced trochlear depth, medial trochlear inclination angle and trochlear depth/patellar thickness ratio. Discussion: Five of the measured morphometric parameters for radiographic detection of trochlear dysplasia in dogs were found to be important in the evaluation of trochlear morphology in dogs. The obtained results indicated the presence of trochlear dysplasia in dogs with MPL. A 3-stage classification system for assessment of abnormal trochlear development in small dog breeds: mild; moderate and severe trochlear dysplasia, was proposed. The occurrence of shallow trochlear groove and medial femoral condyle’s hypoplasia could be accepted as signs of mild and moderate trochlear dysplasia. The pre-operative measurements of these parameters could improve surgical planning and decisions-making.Keywords: medial patellar luxation, trochlear dysplasia, trochlear depth, small dog breeds.
The aim of the present study was to compare the results from measurements of anatomical and mechanical angles of the femur and tibia by means of two diagnostic imaging methods – conventional radiography and computed tomography in normal dogs and dogs with medial patellar luxation (MPL). The study was done with 16 dogs (23 joints) from four small breeds (Mini-Pinscher, Chi-hua-hua, Yorkshire Terrier and Pomeranian). The results showed statistically significant differences between both imaging techniques in the values of mechanical lateral proximal femoral angle (mLPFA) and anteversion angle (AA) in joints with grade II MPL and in the anatomical lateral and medial distal femoral angles (aLDFA, aMDFA) and AA in grade III MPL. In healthy dogs, both methods differed considerably with regard to values of mechanical medial proximal and mechanical lateral distal femoral angles (mMPFA, mLDFA), the mechanical cranial proximal tibial angle (mCrPTA) and the quadriceps angle (Q-angle).
The aim of this study was to evaluate post-operative range of motion of stifle joints in dogs affected with medial patellar luxation in order to compare two surgical techniques: trochlear wedge recession vs. trochlear block recession. The study was done with 67 joints from 54 small breed dogs (21 Mini-Pinschers, 16 Chihuahuas, 11 Pomeranians and 6 Yorkshire terriers). From these, 31 joints underwent wedge recession surgery and the other 36: block recession surgery. In wedge recession surgery, trochlear groove deepening was done by removal of a V-shaped wedge, whereas in block recession, the wedge was rectangular. Block recession is suggested to provide a deeper and wider trochlea with preservation of the major part of the articular cartilage. The results suggested that both trochleoplasty techniques resulted in reduction of joint range of motion and improvement of limb alignment at the first post-operative month.
A clinical case of non-union in a cat after open fracture repair by intramedullary ostheosynthesis of the radius was described. The patient was presented with non-weight bearing lameness, fistulas with purulent discharge, swelling and severe pain. During the surgical revision, after bone sequestrum removal, the bone defect was filled with cancellous and cortical bone autografts. Osteosynthesis with a modified external bone fixator, made of Duracryl ® Plus -a rapidly self-curing metacrylate polymer -and 6 Kirschner wires passing perpendicularly through both radial cortices was performed. The post-operative period was smooth, and after 23 weeks the external fixator was removed. Radiography showed very good bone healing, with excellent clinical result. The use of the ulna as a donor bone was very convenient because it allowed collecting a cortical graft of larger size. The extremely light model of external bone fixator provided adequate strength of fixation elements and proved to be an efficient and not expensive technique for osteosynthesis in cat with non-union fractures of the distal radius and ulna.
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