Patellar Instability in Children and Adolescents

Courtesy: Dr Nirav Pandya, MD, Chief of Paediatric Orthopaedics, UCSF, San Francisco

PATELLAR INSTABILITY

 

Epidemiology

• 8 cases / 100,000 in general population
• 43 cases / 100,000 in pediatric population!!!
• MOST COMMON ACUTE KNEE Diagnosis
• 2ND MOST COMMON CAUSE OF HEMARTHROSIS
• Age 15 is peak incidence
• Females age 10 – 17 = highest

ANATOMY: WHAT KEEPS THE PATELLA IN?

• Bones
• Alignment
• Trochlea
• Muscles
• Extensor mechanism
• Ligaments
• Medial patellofemoral ligament (MPFL)

ANATOMIC FUNCTION OF PATELLA

The primary functional role of the patella is knee extension. The patella increases the leverage that the tendon can exert on the femur by increasing the angle at which it acts

 

CASE PRESENTATION

15 year old. First time this has ever happened

Key Point is to Differentiate between a first time dislocator and a recurrent dislocator!

History

• Generally non-contact twisting injury
• “Something popped”
• 10% direct trauma (rare)
• Family history!!!
• Most spontaneously reduce
• Extension

 

Physical Exam

Physical Exam (Acute)

• Effusion
• Block to range of motion
• Tenderness over medial patella facet / lateral femoral condyle

Imaging studies

Look for :- fractures, Non reduced patella , Loose bodies

Radiographs :- AP, Lateral, Notch, Merchant / sunrise view

MRI After First Dislocation???

• Controversial
• Other ligament injuries
• Loose bodies
• High level athlete??

Initial Treatment

• Rule out other injuries
• Knee Immobilizer
• Crutches
• Refer to Ortho with in < 1 week

 

Treatment for I^st Time Dislocator

• Osteochondral Injury = Arthroscopy +/- ORIF
• No Osteochondral Injury = Physical Therapy

 

Non-operative Physical Therapy Management

1) Reduce pain

2) Reduce swelling

3) Restore range of motion

4) Restore quad muscle control

5) Improve soft tissue flexibility /mobility

6) Normalize gait

7) Control the knee through the hip/trunk/ankle

8) Restore neuromuscular control

9) Consider bracing

10) Return to sport

 

Reduce swelling

• Number one priority
• Knee joint effusion = quadriceps muscle inhibition
• Treatment options: RICE, electrical stimulation, manual therapy, taping, vasopneumatic compression

 

Reduce pain

• Pain also plays a role in the inhibition of muscle activity observed with joint effusion
• Pronounced quadriceps inhibition (30-76%) in group without afferent nerve block during surgery
• Treatment options: cryotherapy, analgesic medication, PROM, E-stim

 

Restore range of motion

• Early knee ROM vs. immobilization?
• Maenpaa et al. found 3x higher re-dislocation rate in early ROM group, but higher rates of stiffness in immobilization group
• General consensus = short period of immobilization for pain/swelling to subside then begin ROM exercises ASAP

 

Restore quad muscle control

• The VMO CAN NOT be preferentially activated and strengthened
• Biofeedback training and taping may improve VMO onset timing only
• Focus on quad strengthening as a whole
• Arcs of motion to reduce stress
• Open Knee Chain: 90 – 45 degrees
• Closed Knee Chain: 0 – 45 degrees

 

Improve soft tissue flexibility/mobility

Is excessive lateral pressure syndrome(ELPS) present?

These are the features of ELPS

• Lateral tilted and/or shifted patella
• Decreased medial glide
• Medial patellofemoral ligament pain
• IT band/lateral retinaculum tightness

Treatment of ELPS: Emphasis muscle flexibility of quads, hamstrings, gastrocnemius, and IT band/TFL

 

Normalize gait

• Typically patient will have a flexed knee gait pattern
• Must reduce joint swelling, restore quad strength, and normalize soft tissue flexibility
• Consider retrograde cone walking as an exercise

 

Control the knee through the hip(Core)….

Gluteus Medius

• Side-lying hip abduction – 81%
• Single leg squat – 64%
• Lateral band walk – 61%

 

Gluteus Maximus

• Single limb squat – 59%
• Single limb dead lift – 59%
• Multi-directional lunges – 41-49%

 

…the trunk….

• The “core” is a multi-layer structure that moves the spine in all planes of motion
• Pre-activates to counterbalance trunk motion and regulate lower extremity postures
• Main goal is to control the center of mass of the body

 

..and the ankle!

• Foot pronation culprits
• Rearfoot/forefoot varus
• Limited ankle DF
• Plantarflexed 5st ray
• Posterior tibialis muscle control
• Ankle proprioception
• OTC foot orthotics necessary?
• 78% improved after 12 weeks

 

Restore neuromuscular control

• Dynamic balance training
• Cutting and pivoting maneuvers
• Acceleration/deceleration drills
• Plyometric and landing strategies
• Smith et al. found 3 activities perceived to be the greatest risk factors for patellar dislocation:” Cutting maneuvers, change of direction, and running on uneven ground

 

Consider bracing

• Controversy exists in the effectiveness of knee braces with a patella buttress following patellar dislocation
• Psychological benefits
• Pain reduction
• Proprioceptive feedback
• Protection
• Neuromuscular patterning

 

Return to sport criteria

1. No pain/instability/effusion
2. Full ROM
3. At least 90% limb strength symmetry (Biodex isokinetic testing)
4. Excellent dynamic stability

• Y -Balance Test < 5% diff, above norms, ant reach < 4cm diff
• Noyes 4 Hop test < 10% diff

5. Low risk on movement screen from Motion Analysis Lab
6. Psychological readiness (Pedi-IKDC self-assessment tool)

 

Motion analysis and sports performance lab

• Isokinetic muscle testing
• Drop jump test
• Cutting
• Deceleration
• Lateral shuffle
• Triple leg hop
• Step down
• Peak vertical impact test

 

Recurrent Dislocator: History

• Mechanism of injury (high vs. low)
• Prior physical therapy (how much)
• Compliance with Home Exercise Program
• Bracing
• Is it dislocating or subluxing?
• ED reduction or spontaneous reduction

Physical exam :- Look for cause of recurrent dislocation.

Imaging :- Plain radiographs and MRI

 

Recurrent Dislocator: Treatment

Depends On:

1. Patient Activity Goals
2. Failure of Conservative Management
3. Chondral Changes / Arthritis
4. Anatomic Area Affected
5. Skeletal Maturity

 

TREATMENT

1) Femoral Anteversion

• Internal Rotation > External Rotation
• More than 25 degree anteversion or asymmetric side-to-side differences
• Treatment –> Femoral osteotomy

2) Genu Valgum – Treatment —> Guided Growth / Osteotomy

3) Patellar Apprehension and J sign From 0 to 30 degrees MPFL, 30 – 70 degrees trochlea,> 70 is notch

3a. Medial Patellofemoral Ligament – Treatment —> Reconstruction

3b. Trochlear Dysplasia –  Treatment  —> Trochleoplasty,  +/-MPFL

3c. Lateralized Tibial tubercle – Treatment –> Tubercle transfer (only when done growing)

3d.  Patella alta – treatment – Treatment —> Tubercle Distalization (only when done growing)

4) Tight lateral retinaculum – Treatment –> Lateral release

 

MPFL RECONSTRUCTION PROTOCOL

• Immediately after surgery
• Toe Touch Weight Bearing with brace locked in extension with use of crutches
• RICE
• Pain control/medications
• Restore quad activation
• ROM 0-60 degrees
• Maintain full knee extension
• Calf pumps for circulation

2-6 weeks after surgery

• Increase ROM 10 degrees each week for goal of 90 degrees by end of 6 weeks
• WBAT with brace locked in extension
• Patellar mobilization (avoid lateral glides)
• LE and core strengthening – CKC knee exercises superior
• Dynamic balance exercises
• Soft tissue mobilization

 

6-12 weeks after surgery

• Progression to full ROM allowed
• Discontinue crutches and brace – Must have good SL squat to 30 degrees
• Emphasis on return to run criteria
• Safe to begin squatting/lunging past 90 degrees knee flexion at 8 weeks post-op

 

Return to Run Program

This program is designed to make sure that you are well enough to return to your sport. When you can complete ALL of these tasks below without pain, swelling, or limping you may return to your sport activities.

You may begin this program when you can perform…

• 20 Calf Raises
• 20 Single Leg Squats (45° knee flexion)
• 10 Lunge Backward Step
• Side Planks – 30 seconds each side
• 20 Squats
• 10 Lunge Forward Step
• Front planks with alternating hip lift – 30 sec.

Walking Test:

• Treadmill walk at 1% incline for 10 minutes at fastest speed (just short of jogging). No pain or limping.

Step and Hold:

• Must perform 20 small leap steps from the uninvolved limb to the involved limb. Step should be at least the distance of the patient’s normal stride length with gait.

Straight Ahead Running:

• 10 minute – 1:1 walk to slow jog
• Add I minute walk and I minute jog each running session if no pain

 

12-16 weeks post-op

• May begin straight ahead running

– Must pass return to run program

– Quadriceps peak torque deficit < 25%

• Double leg plyometrics (begin jump program)
• Advanced balance/proprioception exercises
• Agility drills in sagittal plane only

 

16-24 weeks post-op

• Single leg plyometrics
• Multi-planar agility drills with progressive increase in velocity and amplitude
• Sport specific drills
• Return to sport at 24 weeks if criteria met
• Quadriceps peak torque deficit < 15%
• Low risk on motion analysis screen

 

Return to sport criteria

1. No pain/instability/effusion
2. Full ROM
3. At least 90% limb strength symmetry (Biodex isokinetic testing)
4. Excellent dynamic stability

• Y-Balance Test < 5% diff, above norms, ant reach < 4cm diff
• Noyes 4 Hop test < 10% diff

5. Low risk on movement screen from Motion Analysis Lab
6. Psychological readiness (Pedi-IKDC self-assessment tool)

 

Dislocation Summary

1. Patellar dislocations are common injury in the pediatric population
2. Differentiate 1st time vs. recurrent
3. Bony, muscular, and ligament constraints to dislocation
4. Most 1st time dislocators = Physiotherapy
5. Recurrent dislocators = think what anatomical factors are causing dislocation + MRI
6. Femoral anteversion and valgus are missed
7. MPFL is main constraint from 0 -30, trochlea from 30 – 70
8. Position of tibial tubercle can lead to need for treatment (too lateral, too high)
9. Examine for tight lateral retinaculum