Medial patellar luxation grade IV according to the Singleton system can be classified into skeletally immature and skeletally matured types.

OBJECTIVE: To determine the signalment and musculoskeletal morphology of small-breed dogs affected by medial patellar luxation (MPL) grade IV based on the age of the CT scan. ANIMALS: 40 small-breed dogs (54 limbs) with MPL grade IV. PROCEDURES: Dogs that had undergone corrective surgery for MPL grade IV and had performed CT of the hind limb before surgery were included. Signalment (age, body weight, sex, laterality, and breed) and concomitant cranial cruciate ligament rupture (CrCLR) were recorded. Femoral inclination angle, anatomical lateral distal femoral angle (aLDFA), femoral torsion angle, quadriceps muscle length to femoral length ratio (QML/FL), and patellar ligament length to patellar length were obtained by CT images. The dogs were categorized into 2 groups based on their age at the time of the CT scan, the skeletally immature group and the skeletally matured group. Signalment and group were included in the multiple regression analysis to determine the factors associated with each measurement parameter. A logistic regression analysis was conducted to determine the risk of CrCL concomitant with age. RESULTS: The multiple regression model demonstrated that the group was associated with the value of aLDFA and QML/FL. aLDFA was higher, and QML/FL was lower in group SI than in group SM. CrCLR was present in 5/54 limbs (9.2%), with a mean age of 70.8 months and it was associated with increasing age. CLINICAL RELEVANCE: In Singleton's classification, dogs classified as grade IV can be categorized into 2 groups based on musculoskeletal morphology and pathophysiology: the skeletally immature and skeletally matured types.

Evaluation of the quadriceps muscle length to femoral length ratio in small breed dogs with medial patellar luxation.

OBJECTIVE: To determine the quadriceps muscle length (QML) to femoral length (FL) ratio (QML/FL) and its associated factors in small breed dogs with medial patellar luxation (MPL) and to compare the differences in the QML/FL between MPL grades. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Small breed dogs (<10 kg) with MPL: 78 dogs (134 limbs). METHODS: Medical records and computed tomography (CT) images from 2008-2020 were reviewed. Furthermore, age, bodyweight, sex, laterality, MPL grade, femoral inclination angle (FIA), femoral torsion angle (FTA), anatomical lateral distal femoral angle (aLDFA), and patellar ligament length to patellar length ratio were included in the regression analysis to determine the factors associated with QML/FL. Each measurement parameter was compared among the four MPL grade groups. RESULTS: The final model demonstrated that the QML/FL increased with increasing age (p = .004) and decreased with increasing FTA and aLDFA (p = .015 and p < .001, respectively). The MPL grade IV group had a lower QML/FL than the grade I, II, and III groups (p = .002, p < .001, and p < .001, respectively). CONCLUSION: Among small breed dogs, those with MPL grade IV had a shortened QML associated with femoral deformities. CLINICAL SIGNIFICANCE: Noninvasive evaluation of the QML/FL improves our understanding of the length mismatch between the quadriceps muscle and the femur.

Segmental Femoral Ostectomy for the Reconstruction of Femoropatellar Joint in Dogs with Grade IV Medial Patellar Luxation.

OBJECTIVE: The aim of this study was to describe a new surgical method of segmental femoral ostectomy for the reconstruction of the femoropatellar joint (FPJ) in dogs with medial patellar luxation (MPL) grade IV. STUDY DESIGN: The medical records of six dogs that underwent segmental femoral ostectomy to reconstruct the FPJ for MPL grade IV were retrospectively reviewed. The data included breed, age, body weight, comorbidities, history of orthopaedic abnormalities, pre- and postoperative radiographic findings, morphological indicators measured on three-dimensional computed tomographic multiplanar reconstruction images, surgical methods and postoperative complications. OUTCOMES: Eleven hindlimbs with MPL grade IV in six dogs underwent segmental femoral ostectomy to reconstruct the FPJ with the four basic surgical procedures. Six stifle joints with femoral varus deformity were treated by closing wedge ostectomy and segmental ostectomy, while five stifle joints were treated by segmental ostectomy alone. The mean resected femoral length was 11.7 mm. The mean resected femoral length relative to the preoperative femoral length was 14.3%. The stability and congruity of the FPJ was markedly improved, with an increased range of motion in all dogs compared with their preoperative status. CONCLUSION: Segmental femoral ostectomy was a useful treatment method for MPL grade IV with shortened quadriceps muscle length relative to the femoral length. Reconstruction of the FPJ is important for recovery of limb function.

Effect of Limb Position on Measurements of the Quadriceps Muscle Length/Femoral Length Ratio in Normal Beagle Dogs.

OBJECTIVES: Dogs with patella alta reportedly have a shorter extensor mechanism than normal dogs. The present study aimed to measure the length of the extensor mechanism and to assess the effect of limb position on the quadriceps muscle length (QML)/femoral bone length (FL) ratio. STUDY DESIGN: Three-dimensional computed tomography images were taken of 12 Beagle dogs. Each dog underwent computed tomographic imaging 24 times with different limb positions. The QML/FL was measured on each image, along with the hip flexion-extension, hip abduction-adduction and stifle flexion-extension angles. Multiple regression analysis was used to determine the effect of these angles on the QML/FL. RESULTS: The QML/FL was increased with the hip extended (standardized partial regression coefficient 0.855 with linear plotting, 0.829 with log plotting) and with the stifle flexed (standardized partial regression coefficient 0.814 with linear plotting, 0.800 with log plotting). The partial regression coefficient of the hip abduction-adduction angle was small, indicating a small impact on the QML/FL. The 95% confidence range of the QML/FL with the hip extended and stifle flexed was 0.87 to 1.00 (mean ± standard deviation: 0.93 ± 0.03). CONCLUSION: The QML/FL was more influenced by joint angles when the hip was flexed or the stifle was extended. Hence, these positions should be avoided when evaluating the QML/FL so that the QML is less altered by slight positioning disparities.

Clinical Efficacy of Bone Reconstruction Surgery with Frozen Cortical Bone Allografts for Nonunion of Radial and Ulnar Fractures in Toy Breed Dogs.

OBJECTIVE: To evaluate the effectiveness of frozen cortical bone allografts (FCBA) in the treatment of severe radial and ulnar atrophic nonunion fractures. ANIMALS: Toy breed dogs with nonunion of radial and ulnar fractures (n = 15). METHODS: Severe atrophic nonunion fractures were treated with FCBA (eight infected and seven non-infected fractures). Radiographs obtained immediately after surgery, and 1, 2, 3, 6 and 12 months later were evaluated and scored for the periosteal reaction at the bone regeneration sites, the healing process in the bone connection areas at both the proximal and distal sites, and the bone remodelling process within the allografts. RESULTS: Improvements in the fracture-healing process and weight-bearing function were observed in all cases. Radiographic scores at the bone connection areas and within the allograft improved significantly over time (p < 0.05). There were not any significant differences in radiographic scores between the infected and non-infected groups. CLINICAL SIGNIFICANCE: Bone reconstruction with FCBA is effective in the treatment of radial and ulnar nonunion fractures associated with large bone defects, regardless of the infection status of the surgical site.