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What are 2 types of developmental hip lameness?
- hip dysplasia
- legg perthes disease
What are the clinical aspects of hip dysplasia? (5)
- developmental condition of the hip, characterized by laxity
- primary laxity leads to secondary osteoarthritis
- signs appear in animals >5-8 months old (may occur earlier with exceptionally severe disease)
- common in large breed/ working/ herding dogs
Dogs that develop _________ due to hip dysplasia are _________ at birth.
hip laxity and OA; structurally and functionally normal
Describe the difference between luxation and subluxation.
- luxation: complete loss of contact b/w articular suraces of the joint
- subluxation: still contact between articular surfaces of the joint, but it's not perfectly aligned
Why might you see a collapse of the joint space on radiograph with hip dysplasia?
proteoglycan depletion and collapse of space is associated with loss of cartilage thickness--> bone on bone contact across the joint
What are surgical options for hip dysplasia in immature dogs? (8)
- triple/ double pelvic osteotomy
- femoral neck lengthening
- intertrochanteric osteotomy
- sacro-iliac wedge
- juvenile pubic symphysiodesis
- denervation of the hip joint capsule (to relieve pain, not improve function)
- pectinal myectomy (rarely done- resection of this muscle on the medial aspect of the thigh)
What are surgical options for hip dysplasia in mature dogs? (7)
- *total hip replacement
- *femoral head and neck excision (FHO)
- excision arhtroplasty
- pectineal myectomy
- BOP shelf arthroplasty
- denervation of the hip joint capsule
What is the rationale behind using juvenile public symphasiodesis to manage hip dysplasia in immature dogs?
- this procedure modifies the conformation of dogs that are going to develop hip instability to destroy the potential of the pubic symphasis to spread as the pelvis grows
- closure of the pelvic symphasis results in acetabular rotation, which enhances femoral head capture
In what animals can we perform juvenile pubic symphasiodesis? What is the ethical concern?
- dogs between 12-16 weeks of age that will develop hip laxity d/t inherited dysplasia
- these dogs are genotypically dysplastic and SHOULD NOT BE BRED (consider simultaneous sterilization)
How is juvenile pubic symphasiodesis performed?
electrocautery applied to the pubic symphasis
What is a con of the juvenile pubic symphsiodesis procedure?
these dogs my not be able to abduct their hind limbs normally
Why isn't triple pelvic osteotomy used to treat dogs with significant hip instability?
the dog has to grow in order to modify the conformation of the hip; in dogs with severe instability, the acetabulum may never capture, so this is not used to treat dogs with significant instability
How is triple pelvic osteotomy performed?
- osteotomy of the pubis, ischium, and ilium allows rotation of the acetabulum to increase femoral head coverage
- use TPO plate to hold the pelvis in the rotated position
Why must a dog be under 10 months of age to be a candidate for triple pelvic osteotomy?
once the subchondral plate is developed, the plasticity of the joint is lost (will not remodel or change shape)
What is the angle of reduction?
the angle b/e the femur and the median plane at which the femoral head reduces with abduction (in animals with hip laxity)
What is the angle of subluxation?
the angle b/w the femur and the median plane at which the femoral head subluxates with adduction (in animals with hip laxity)
What are the requirements for an animal to be a candidate for triple pelvic osteotomy? (5)
- 5-10 months old
- minimal or no radiographic evidence of DJD
- good femoral head capture (positive clunk when you pop the hip back in (minimal grating/ crackling)
- angle of reduction <30 degrees (if you need to rotate it more than this, you will create significant mechanical lameness)
- angle of subluxation <10 degrees
What is the ethical dilemma with triple pelvic osteotomy?
early surgery is best to reduce the progression of OA, but there is the potential for spontaneous clinical improvement in many dogs
What is Legg Perthes disease? (5)
- non-inflammatory aseptic ischemic necrosis of the femoral head and neck
- primarily a disease of subchondral bone, in which subchondral lucencies develop and a large cavity develops--> ultimately cartilage collapses into that "sink hole"--> significant lameness
- signs appear at 3-8 months of age
- common in toy breeds and terriers
Why is there a level of urgency to repair acute femoral capital physeal fractures?
- normal distribution of blood from nutrient foramen does not cross the physeal line, ie. this entire area requires integrity of the capsule in order to be vascular; the longer you wait for repair, the more of these capsular blood vessels are destroyed—> avascular necrosis of the femoral head
- fix surgically within 4 days
What are clinical correlates of chronic femoral capital physeal fracture?
- related to early neuter and obesity in male cats
- apple-core remodeling of femora neck on radiograph
- primary repair is impractical--> treat by femoral head and neck excision
How do you diagnose infectious arthritis of the hip?
synoviocentesis showing neutrophilic inflammation +/- intracellular bacteria
Describe the clinical correlates of infectious arthritis of the hip. (3)
- usually hematogenous spread
- bacteria preferentially colonize osteoarthritic joints
- rule out endocarditis and discospondylitis
Femoral head and neck excision is used to address... (4)
legg perthes, hip dysplasia in mature dogs, septic arthritis, and chronic femoral capital physeal fractures
What is important to remember when performing femoral head and neck excision?
- must remove femoral head along the line connecting the medial border of the greater trochanter to the border of the lesser trochanter
- not removing enough neck will result in chronic lameness and the need for revision surgery
What are the limitations of FHO? (5)
- dogs >20-30kg may not do well
- decreased range of motion
- limb shortening and conformation change
- incomplete recovery of muscle bulk
- may lead to medial patellar luxation
What are primary synovial neoplasias? (3)
- histiocytic sarcoma
- synovial cell sarcoma
- synovial myxoma