Transcript Patellar Instablity-Beicker

Patellar Instability
Clint R Beicker MD
June 5, 2015
Please note change from program
Objectives
• Review the anatomy and biomechanics of the
MPFL and structures that provide patellofemoral
stability
• Discuss the management of the first-time patellar
dislocation
• Review surgical treatment of recurrent patellar
instability and expected rehabilitation and return
to activity
A common problem
• Incidence of primary patellar dislocation is 5.8
cases / 100,000 population
• 43 cases / 100,000 population in children
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Peak incidence at age 15
Highest risk of acute dislocation
(and recurrence) is females age 10-17
• Acute patellofemoral dislocation is
most common acute knee disorder
in children and adolescents
• 2nd most common cause of
hemarthrosis in adolescent knee
• Redislocation rates range from 20-55 %
Patellar stability
• Osseous component
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Trochlear morphology
Bony Alignment
• Dynamic component
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Extensor Mechanism function
• Static/Ligamentous component
• MPFL
Medial Patellofemoral Ligament
Patellar stability
MPFL Anatomy
• Runs in layer 2 on the medial
aspect of knee
• Origin: 1.9 mm anterior / 3.8
mm distal to adductor tubercle
• Insertion: superior 2/3rds of
patella
– Broad insertion over 28 mm over
superior patella
• Average length 59.8 mm
Medial patellofemoral ligament (MPFL )
• Primary restraint to patellofemoral
instability at 0-30 degrees of flexion
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Provides over 50% of medial restraint
to patella
Tensile strength = 208 N
• Tear occurs at femur (66%),
patella (13%) and midsubstance (21%)
• Once patella is engaged in the
trochlear groove, lateral patellar facet
provides primary resistance force
Evaluation
Exam
• Assess overall limb alignment
• Assess generalized ligamentous laxity
• Tenderness
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patella, along MPFL, at femur
Crepitance
Effusion
Patellar Glide test
Patellar apprehension sign
Patella tilt
J sign
J Sign
Evaluation
Radiographs
• AP, lateral, Merchant views
• Fractures
• Trochlear dysplasia
• Crossing sign
• Dejour classification
• Patellar height
• Caton-Deschamps
• Blackburne-Peel
• Insall-Salvati
• Patellar tilt
• Patellar position/subluxation
Evaluation
Radiographs
• AP, lateral, Merchant views
• Fractures
Evaluation
Radiographs: AP, lateral, Merchant views
• Trochlear dysplasia
Crossing sign
Evaluation
• Trochlear dysplasia
Evaluation
• Radiographs: AP, lateral, Merchant views
CT/MRI
• TT-TG (anterior tibial tubercle – trochlear
groove) distance
• Originally via CT
• Can do via MRI
• underestimates TT-TG by 3-4
mm)
• Value >20 mm is strong
predictor of instability
Advanced Imaging Evaluation
When to get an MRI
• Large knee effusion
• Recurrent dislocation
• Fracture on xray
• Clinical concern
-*Up to 95% incidence of
cartilage lesions on MRI
*Nomura et al – Arthroscopy – 2003
All Patellar Dislocations
are not the same
because the underlying anatomy is not the same
Management of the 1st time dislocator
Can We Predict Recurrence?
Nonoperative treatment for first time dislocation
(222 pts)
• 62 % successs rate overall (38% redislocation)
• The worst combination:
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31 % success if open physis and trochlear dysplasia
• 51% of patients with recurrence required surgery
Have we improved our outcomes?
• Hawkins et al – 1986 – AJSM
• 27 patients with acute dislocations treated either
operatively with MPFL +LR (7 pts) or non-operatively
(20 pts)
“Although the incidence of recurrence among those
individuals can be decreased [with surgery], at least
30% to 50% of all patients having sustained a
primary patellar dislocation will continue to have
symptoms of instability and/or anterior knee pain.”
• 2,000 patients in meta-analysis
• Conclusion: Operative treatment after 1st patellar dislocation
results in lower recurrence (29% vs 34%) but does not affect
functional outcome score
Not all patellar dislocations are the same
Non-operative management
• Immobilization
• Closed chain exercises –
-quad (VMO) strengthening
-gluteal strengthening
-core strengthening
• Patellar taping
Patellar stabilization surgery
• Nearly 30 different surgical procedure exist…
Post-operative Rehab
Thank You