Evaluation of Hindlimb Deformity and Posture in Dogs with Grade 2 Medial Patellar Luxation during Awake Computed Tomography Imaging while Standing

Abstract

Objective The aim of this study was to determine the degree of bone deformities and hindlimb postural abnormalities in a standing position in awake Toy poodles with and without grade 2 medial patellar luxation (MPL) using high speed 320-row computed tomography (CT). Methods The limbs with grade 2 MPL (MPL-G2 group) and without any orthopaedic disorders (control group) were imaged in a standing position, without sedation or anaesthesia, using CT. In MPL-G2 group, images were obtained when the patella was luxated (G2-L group) and reduced (non-luxation, G2-NL group). Bone morphologies of the femur and tibia were quantified three-dimensionally. Hindlimb standing posture was evaluated by measuring femoral rotation and abduction angles, tibial rotation angle, metatarsal rotation angle, foot rotation angle, angle between the femoral anatomical axis and the mechanical axis of hindlimb and stifle joint line convergence angle. Results There were no significant differences in bone morphologic parameters between the MPL-G2 group (5 limbs) and the control group (6 limbs). In the G2-NL group, there were no significant hindlimb postural abnormalities. In contrast, in the G2-L group, significant hindlimb postural abnormalities including external rotation of femur, internal rotation of tibia and foot, external rotation of tarsal joint, large stifle joint convergence angle, genu varum and toe-in standing were observed. Conclusion Dogs with grade 2 MPL have no bone deformities but show abnormal standing posture when the patella is luxated.

Untitled

“…Using this technology, investigators from Japan studied Toy Poodles with grade two medial patellar luxation while the dogs were awake and standing. 1 Their studies indeed confirmed that these dogs lacked any significant bone deformity. However, with the patella medially luxated, there were marked standing postural abnormalities of the hindlimb.…”

“…These included external rotation of femur, internal rotation of tibia and foot, large stifle joint convergence angle, genu varum and toe-in standing in dogs with a grade two medial patellar luxation. 1 The genu varum stance was associated with 30 degrees of internal rotation of the tibia, relative to the distal femur. Clinically this 'bow-legged' stance could be mistaken for distal femoral varus and a medial deformity of the tibial tuberosity.…”

“…This study contributes to understanding of the pathophysiology of medial patellar luxation. 1 But it is unclear if medial luxation of the patella is responsible for the femorotibial rotary subluxation, or if the reverse is true. Full details of this study are available in this issue of the journal.…”

Early Surgical Management of Medial Patellar Luxation in Juvenile Dogs

“…5 Medial patellar luxation typically accompanies varus deviation of the distal femur, valgus of the proximal tibia, external torsion of the tibia and malposition and incorrect development of the quadriceps musculature. 6…”

“…5 Medial patellar luxation typically accompanies varus deviation of the distal femur, valgus of the proximal tibia, external torsion of the tibia and malposition and incorrect development of the quadriceps musculature. 6 Classically, surgical correction of medial patellar luxation is recommended in adult patients without active physeal lines or young adults who are close to skeletal maturity. 3,7 However, maintenance of bone deformities while the physeal lines remain open and functional can generate even more pronounced bone deviations, culminating in the progressive worsening in these patients.…”