Patellar Instability: Diagnosis Management

Pictorial and detailed description of patellar instability with sign and symptoms and how to diagnose , what investigations you should go with and how to approach with treatment options . I have presented this slide in my 2nd year junior residency in orthopedics at LLRM medical college Meerut and got good reviews for it
After getting it read you will definitely understand the topic.

1. Patellar Instability
Allison K Perry
Bhargavi Maheshwer
Steven F DeFroda

Journal of Bone And Joint Surgery
(Nov 2022 Vol 10 issue 11)


Dr Nitin (Junior Resident)

2. Introduction
Patellar instability is a potentially devastating diagnosis with high recurrence rate
upto 71%
Return to preinjury level of sport 67% without surgery
After index instability episode, patients with a patellar dislocation have nearly 7
fold increased risk of recurrence

3. Risk Factors
General Factors
Ligamentous laxity
Previous traumatic event
Miserable Malalignment syndrome
Anatomic Factors
Patella Alta
Trochlear Dysplasia
Increased TT TG and TT PCL distance
Patellar Dysplasia
Excessive patellar tilt
Dysplastic VMO
Overpull of lateral structures:ITB, vastus
lateralis

4. Recurrence risk factors
Younger Age
Previous contralateral patellar dislocation
Skeletal immaturity
Lateral patellar tilt
Increased TT-TG distance
Patella alta
Trochlear Dysplasia

5. Classification
Acute - single episode after significant trauma
Almost always lateral
Recurrent- Repeated occasional dislocation
Occurs at interval pf weeks or months
Habitual - Patella dislocates every time the knee is flexed
(Critical Angle- Angle of flexion at which patella dislocates)

6. Patellofemoral Joint Stabilizer
Static
Shape of patella
Shape of femoral sulcus
Joints capsule
Retinaculum
Ligaments MPFL

7. Dynamic
Quadriceps Muscle
Vastus medialis obliqus




During full extension to 30° flexion main stabilizer MPFL
Beyond 30° main stabilizer trochlear bony anatomy
(Medial patellotibial and medial patellomeniscal ligament serve as secondary
stabilizer beyond 45°)

8. Examination
After an instability episode,lower limb
alignment,hypermobility and gait should be
assessed
Patellar height in seated position: high/low
riding patella

Dynamic patellar tracking :Positive J sign
:Patella move laterally on active knee
extension from flexed position.
hard/jumping snap - severe Dysplasia
Or soft glide - Malalignment

9. Q Angle Angle between line of action of patella and quadriceps tendon
Male >15°
Female>20° indicate greater lateral force

10. Q angle measured at 20° flexion
•Lateral Subluxation pf patella in full extension can give rise false low value
•External tibial torsion in full extension can increase the apparent Q angle

11. Factors Increasing Q Angle
Genu Valgum
Excessive femoral anteversiom
External tibial torsion
.lateral Tibial Tuberosity

12. Beighton Score
>4 out of 9 indicate ligamentous laxity
•passive little finger dorsiflexion >90°
•passive thumb opposition to flexor
aspect of the wrist
• Elbow Hyperextension >10°
•knee Hyperextension >10°
• Ability to flatten both palms on floor
with extended knee and flexed hip

13. Patellar Glide test
Patella is divided into 4 longitudinal
quadrants
Patella is displaced medially
Medial displacement of one quadrant or
less is suggestive of excessive
retinaculum tightness
If displacement ≥ 3 quadrants- Possible
injury to lateral or medial patellar stabilizer

14. Patellar Grind test
Pressure over patella
Displace it medially, laterally, superiorly
and inferiorly in the trochlear groove
Positive Test: Anterior knee pain with a
pathologic condition of Patellpfemoral
joint

15. Rotational profile of staheli
Craig Test (Femoral anteversion) normally 10-15°
Thigh foot angle (rotational deformity of tibia) >30°
Foot progression angle (ntoe gait)

16. Fairbanks apprehension test

Patellar tilt test: knee in 20 degree flexion
Inability to raise patella with thumb and finger
to the horizontal plane or slightly past indicates
excessive lateral retinacular tightness

17. Shape of patella
Wiberg classification of patellar shape.

18. Symptoms
Pain around knee aggregated on walking uphill/downhill or stairs
Feeling of insecurity and knee cap giving away
Patellar crepitation
Knee swelling

19. Investigations
Xray AP view
Xray knee lateral
Xray axial view
CT Scan
MRI
(MRI >CT)

20. Xray lateral view
Blumensaat Line

21. Insall Salvati index
Blackburn peel Ratio
Caton Deschampe index

22. AXIAL VIEW

23. Trochlear Dysplasia
Dejour’ Classification (True lateral view) Shape of trochlear Groove

24. Crossing Sign
The point at which the line of trochlear floor crosses the anterior contour of lateral
femoral condyle
As the crossing sign move inferiorly- More assymetrical condyles and more severe
trochlear Dysplasia
Trochlear Bump
>3mm abnormal

25. Sulcus Angle > 145° and trochlear depth< 4mm - Trochlear Dysplasia
Congruence angle > 16° - patellar Subluxation

26. CT Scan
TT TG Distance
(>20 mm is suggest Malalignment)

27. Patellar Tilt
Normal <20

29. MRI
Useful in assessment
of bony,cartilaginous
and ligamentous
lesions
eg MPFL
Associated chondral
injuries

30. MRI vs CT
MRI TT-TG values were 4.16 mm less than CT measurement
TT-PCL distance can be measured on MRI with excellent reliability
TT PCL >24 mm abnormal
(Represent true
tibial tubercle
lateralisation)

32. Treatment
Aim
Decrease swelling and relieve pain
Enhance restraints
Painfree ROM
Address the Pathoanatomy causing Dislocation

33. Acute Dislocation
Conservative
Immobilization for 6 Weeks : Stiffness
Immediate mobilization with brace : recurrence
Surgery indicated for: 1 osteochondral fractures
2 Loose bodies
3 Athlete with high level activity
MPFL reconstruction +VMO Repair
A systematic review of meta-analysis comparing nonoperative and operative management found that surgery have lower
rate of recurrent dislocation but does not improve functional outcome
A recent RCT demonstrated - MPFLR 6.7% instability rates
Non operative - 41.9% instability rates

34. Recurrent Dislocation
Surgery
No single universal surgical procedure

Choice of surgery depends on
Pathological anatomy
Patient demand
Skeletal maturity

35. Lateral release
Medial repair
MPFL reconstruction
Trochleoplasty
Proximal realignment procedure
Distal realignment procedure
(Patellar dislocation recurrence may occur after surgical stabilization 8.4% upto 5
years postop)

36. MPFL Reconstruction
Autograft/Allograft
•Gracils
•Semitendinosus
•Patellar
•Quadriceps
Adequately tensioned

(Note- MPFL insert between Adductor tubercle and medial epicondyle on femur
And some other its fibers insert on quadriceps tendon as in addition to patella)

37. Complications of MPFLR
Patellar fracture ( Transpatellar bone tunnel - provide greater stability than suture
repair but increase risk of iatrogenic fracture and other complication rate)
Postoperative instability
Flexion loss
Pain
Overall complication rate 26%

38. Tibial tubercle transfer
Elmslie-Trillat Technique
(Distal realignment procedure)
Lateral Retinacular release
Medial capsular reefing
Medial transposition of anterior tibial
tubercle
C/I varus knee, degenerative medial
compartment,medial Menisectomy
Fulkerson Technique
Anteromedialisation technique
Decrease contact pressure on lateral
and central trochlea and increase on
medial trochlea

39. Proximal realignment procedure

Done in skeletally immature individual
Lateral Retinaculum and capsule released
Quadriceps tendon split and suture to patella

40. Trochleoplasty
Indications
J sign with TT TG distance >20
mm
Dome shaped trochlea

Reduces risk of dislocation but
does not halt the progression of
arthritis

41. Summary
Presence of a preoperative J sign is predictive of recurrent instability after
operative management
Nonoperative treatment with patellar bracing and therapy best for primary patellar
dislocations
Aspiration of effusion acutely allows patient to regain quadriceps strength and
control
Loose body - arthroscopic removal / fixation +/- medial repair
Primary repair indicated when there is extensiveextensive medial side injury,
femoral avulsion of MPFL and avulsion of VMO

42. In case of recurrence treatment should be directed at correcting underlying
pathological condition
No role of isolated lateral release for patellar instability
MPFLR the choice of recurrent instability with or without trochlear Dysplasia with
normal TT TG distance and normal patellar height
Distal realignment- Choice for increased TT TG distance and patella alta
( standard medialisation of TT- Normal patellar height and trochlear anatomy and
increased TT TG
Distalisation- added if there is concomitant patella alta
Anteromedialisation of TT- Lateral and/or distal patellar facet Chondrosis)