Transcript Medial Patellar Luxation

Veterinary Specialists Of South
Florida Presents…
Medial Patellar Luxation
VETERINARY SPECIALISTS
OF
SOUTH FLORIDA
Dr. Kelly Alford
“Penny”
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Signalment
o 6 yo FS Yorkie
Presenting Complaint
o Weight bearing lameness on the RH limb
History
o No trauma
o Other dogs in home
o Non-painful
o Otherwise healthy
Physical Examination
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BAR, mm = p/m, CRT < 2 sec’s
Vital signs wnl
H/L auscultation wnl
MPL
• Grade I on the left stifle
• Grade IV on the right stifle
Partial or full tear of the CCL in the right
stifle
Rest of PE unremarkable
Treatment
 Penny
presented 8 days later for
surgery
 PE – unchanged
 Blood work:
 CBC/Chemistry
○ Unremarkable
Surgery
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Surgery
 Arthrotomy
○ Partial CCLR
○ Medial meniscal release
 Imbrication of the joint capsule
 Lateral suture
 Imbrication of the lateral retinaculum

Post – Op
 Home on Tramadol, Rimadyl and Simplicef
 Strict cage rest
Patellar Luxation
Femoropatellar instability
 Leads to displacement of the patella
from the trochlear groove
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 Medial, lateral or proximal
>75% cases are medial (small & large
dogs)
 50% bilateral
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Pathophysiology
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Associated musculoskeletal
abnormalities:
 Medial displacement of the quadriceps
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muscle group
Lateral torsion of the distal femur
Lateral bowing of the distal 1/3 of the femur
Femoral epiphyseal dysplasia
Rotational instability of the stifle joint
Tibial deformity
Pathophysiology
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Medial malalignment of the
quadriceps muscles
 Retards distal femoral physis growth
 Less pressure on the lateral aspect allows
accelerated growth
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Lateral bowing of the distal femur
Abnormal growth while the physes are active
Tibial deformities
 Medial displacement of the tibial tuberosity, medial
bowing of the proximal tibia, lateral torsion of the
distal tibia
Articular Cartilage
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Responds to change in pressure
 Increased pressure: retards growth
 Decreased pressure: accelerates growth
Abnormal trochlear groove
 Near normal to absent
 Patella produces a physiologic pressure on the articular
cartilage that retards cartilage growth
 Continued pressure from the patella is responsible for the
development of the normal depth of the trochlear groove
 If no pressure is exerted, the trochlea fails to gain proper
depth
Grading System
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Severity classified into grades:
 I: patella manually luxated when
stifle is in extension, spontaneous
luxation rare
 II: intermittent luxation with a nonpainful, “skipping” lameness
 III: permanent luxation that can be
reduced manually
 IV: permanent, non-reducible
luxation
Signalment
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Dogs >>> cats
Toy and miniature dog breeds
Higher incidence:
 Miniature and toy poodles, Yorkshire terriers,
Pomeranians, Pekingese, Chihuahuas and Boston
terriers
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Age – generally after 4 months of age
Females 1.5: 1 over males
Clinical Presentation

History
 Intermittent weight-bearing lameness
 Holds leg up – flexed position
 Grade IV – severe lameness & gait
abnormalities
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PE Findings
 Vary depending on severity
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Laboratory Findings
 Non specific
Diagnostics

Radiographs
 Grade I-II
○ May show the patella within the trochlear
sulcus or displaced medially
 Grade III-IV
○ Show the patella displaced medially
 Full limb radiographs may show varus or
valgus deformities and torsion of the tibia
and femur
Differential Diagnosis
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CCLR
 Concurrent in 15-20% of cases
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Avulsion of the tibial tubercle
Hip luxation/FHO
 Shortens limb d/t laxity of quadriceps mechanism
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Rupture of the patellar tendon
Avascular necrosis of the femoral head
Malunion & malalignment of fractures of femur
or tibia
 May result in displacement of the quadriceps muscle
group
Treatment
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Conservative management
 Older
 Asymptomatic
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Surgical management
 Young
 Lame
 Active growth plates
Surgery
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Numerous techniques described:
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Tibial tuberosity transposition
Medial restraint release
Lateral restraint reinforcement
Trochlear groove deepening
Femoral osteotomy
Tibial osteotomy
Antirotational sutures
Transposition of the origin of the rectus femoris
Combination of techniques most effective
 Soft tissue and orthopedic
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Primary abnormality is biomechanical
Soft Tissue
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Release of the medial
retinaculum
 Stabilizes patella in groove
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Reinforcement of the lateral retinaculum
 Imbrication of the joint capsule
Quadriceps release
 Anti-rotational suture
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Trocheoplasty
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Deepening of the trochlear groove:
 Trochlear wedge or block recession
 Trochlear chondroplasty
 Trochlear sulcoplasty
Tibial Tuberosity Transposition
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Realigns the extensor mechanism
 Realigns the attachment of the patellar
ligament
Femoral Osteotomy
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Severe skeletal deformities
 Varus bowing of the distal femur
 Medial torsional deformity of the proximal
tibia
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Goal
 Realign the stifle joint
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In conjunction with previous procedures
CCLR
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Quadriceps mechanism
 Secondary stabilizer of the stifle joint for
cranial drawer
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Chronic luxation
 Increased stress on the CCL
 Eventual rupture
Post-operative care
Soft padded bandage
 Restricted exercise
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 6 weeks
 Physical rehabilitation
 Leash walks
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Gradual return to normal activity
 Over 6 weeks
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Radiographs at 6-8 weeks
 Assess healing of the tibial crest transposition
Prognosis
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Grade I-III
 Excellent after surgical correction
 DJD
 Reluxation
○ 50% of cases
○ Grade I

Grade IV
 Guarded
 Multiple surgeries
 Corrective osteotomies
“Penny” - outcome
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4 days post-op
 Bandage removal
 Placing weight when standing
 Emphasized restricted activity
○ Owner let Penny off leash in lobby
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3 weeks post-op
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Acutely lame after jumping off couch
Seemed okay at recheck to owner
Walking well, placing weight on all 4 limbs
No instability detected on palpation
References
Fossum, TW. Small Animal Surgery. 3rd
edition, Elsevier, 2007, pp 1289-1297.
 Tilley, LP, Smith, FW. Blackwell’s FiveMinute Veterinary Consult: Canine &
Feline. 4th edition, Blackwell, 2007, pp
1036-1037.
 Slatter, D. Textbook of Small Animal
Surgery. 3rd edition, Saunders, 2002, pp
2122-2126.
 Johnston, S. Patella Luxation. SAMS 5345
Lecture, 2008.
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