This document discusses the case of a 17-year-old female with recurrent bilateral patellar dislocation. Examination revealed features of bilateral patellar subluxation with trochlear dysplasia. Recurrent patellar dislocation has a high recurrence rate and requires a multifactorial treatment approach. Surgical options discussed include MPFL reconstruction, tibial tubercle transfer, trochleoplasty, and femoral derotational osteotomy, but there is no consensus on the best procedure. Treatment must be individualized based on the patient's anatomy and injury characteristics.

1. Recurrent Patellar
Dislocation
Dr Asish Rajak
Fellow Sports Medicine And Arthroplasty

2. Case
• 17 yr Female
• Recurrent bilateral patellar dislocation
• Left : 5-6 episode in last 2 yrs
• Right : 1 episode , non traumatic 2 yrs back
• Pain on going up and downstairs

3. On examination
• Bilateral knee: ROM full and painless
• Apprehension test + bilaterally
• Patellar grind test + bilaterally
• Facet tenderness absent
• Ligamentous laxity present

4. Evidence of patellar subluxation is seen on both side

5. Feature of Trochlear dysplasia

6. Feature of Trochlear dysplasia

7. Borderline TT-TG distance

8. No evidence of Patella alta or baja seen . Insall
salvati ratio of 1.12(left) and 1.06 (rt)

9. • Conclusion: Features of Bilateral patellar
subluxation with trochlear dysplasia

10. • Average annual incidence of primary patellar
dislocation: 5.8 cases per 100,000
• higher for younger and more active population
• Complications :
– articular cartilage injuries
– osteochondral fractures
– recurrent instability
– pain
– decreased activity, and
– patellofemoral arthritis

11. Recurrent patellar dislocation
• Recurrence: 15% to 80%
• After a second dislocation : chance of continued
episodes of patellofemoral instability >50%
• Multifactorial problem
• Patellar stability : relies on
– limb alignment
– osseous structure of the patella and trochlea
– integrity of static and dynamic soft-tissue constraints

13. • Management : difficult
– heterogeneous patient population
– variety of technically challenging surgical
techniques
– a lackof long-term and robust clinical outcome
studies

14. Clinical evaluation
• A detailed history of the dislocation events:
– age, skeletal maturity, sex, overallactivity level of the
patient
– the activity and position of the knee at the time of
dislocation
– previous dislocation events
– All prior treatments, including bracing, physical
therapy, and surgery should be reviewed
• Important to understand the patient’s
expectation for the return to sports, particularly
for an in-season athlete

15. • General ligamentous laxity: the Beighton
hypermobility score
• A valgus appearance on standing: often results
from limb alignment abnormalities
– Increased femoral anteversion
– hyperpronation of the foot
– external tibial torsion
• Muscle imbalance or weak
musculature:dynamic instability

16. • Vastus medialis obliquus bulk: evaluated and
quantified
• Range of motion and lower-extremity strength:
compare bilaterally
• Palpable defect: along the medial retinaculum
or medial patellofemoral ligament (MPFL)
• Tenderness over the MPFL origin(Bassett sign)
• Patellar tracking should be examined and
“J” sign noted
• Glide test
• Apprehension test

17. Diagnostic Imaging
• Plain radiography:
– Standard anteroposterior weight-bearing
radiographsof both knees
– posteroanterior weight-bearingradiographs made
with the knee at 45˚ of flexion: assessment of the
coronal alignment of the tibiofemoral joint and
the presence of arthrosis
– Standing long-leg anteroposteriorradiograph: if
there is any concern for coronal malalignment

18. – True lateral radiograph in 30˚ of knee flexion :
trochlear morphology, patellar height, patellar tilt,
and the presence of arthrosis
– True lateral radiographs may alsoidentify
trochlear dysplasia
• crossing sign
• evidence of a supratrochlear spur
• a double contour, which denotes a hypoplastic medial
condyle

19. • Insall – salvati index(1/2)
• Caton- Deschamps
index(3/4)
• Blackburn peel index
(5/6)

20. Dejour classification of trochlear
dysplasia

21. • The Merchant view, made with the knee
flexed 45˚ and the beam inclined 30˚ distally
– assess patellar tilt
– patellar subluxation
– trochlear dysplasia

24. • High-resolution, axial, computed tomographic
(CT) images: accurately characterize the
morphology of the trochlea and assess
femoral and tibial torsion.
• If concern about the risk of radiation
exposure with CT scanning: magnetic
resonance imaging (MRI) will often suffice

25. • Relative rotation : assessed via measurement
of the tibial tubercle-trochlear groove (TT-TG)
distance
• averages 8 to 10 mm in pediatrics
• ATT-TG distance of ≥20mm is highly
associated with patellar instability

27. MR imaging
• Most useful for evaluating the soft-tissue
restraints of the patellofemoral joint and the
chondral surfaces.
• Mainly MPFL injury:
– medial femoral condyle should be carefully evaluated
– adjacent soft-tissue damage(VMO edema/ avulsion)
• In acute injury: cartilage damage, bone bruising
• Also helpful in assessing patellar height in terms
of patellar trochlear index

28. • Patellotrochlear index: ratio of trochlear
articular cartilage to patellar articular cartilage
on the MRI sagittal slice at the midline of the
knee with the leg in extension
– Values of <12.5% and >50% indicate patella alta
and patellabaja, respectively
– More clinically relevant tool to measure patellar
height in patients with trochlear dysplasia
• MRI-based estimates of TT-TG distance
underestimate the distance by an average of
3.8 mm compared with CT-based estimates

29. Treatment : non operative
• Nonoperative treatment for first time lateral
acute patellar dislocation
• For recurrent dislocation : within a sporting
season with a desire to continue to participate
• bracing or McConnell taping and gradual
resumption of full motion and strength before
the return to play
• Hinged knee braces or lateral stabilization brace :
enhance the patient’s sense of stability
• Physical therapy: focus on strengthening the
vastus medialis obliquus and gluteal musculature
in order to improve patellar stability

31. MPFL reconstruction
• Most important restraint to lateral patellar
displacement from 0 to 30˚ of flexion is the MPFL
• Advantage of reconstruction: replacement of the
torn or stretched ligament with a collagen-
containing graft rather than imbrication of
stretched or compromised tissues
• femoral attachment of the MPFL has received
much more scrutiny than the patellar attachment

32. • Main focus on
– femoral tunnel position localization
– graft isometry
– confirmation with radiographic parameters
• femoral tunnel malposition : leads to graft
anisometry graft laxity / excessive
patellofemoral compression forces
• A femoral tunnel placed too far proximally :graft
laxity in extension and excessive graft tension in
flexion

33. Radiographic guidelines developed by Schottle et al.
and Stephen et al. to aid in femoral fixation

34. • Thaunat and Erasmus: introduced the concept
of so-called favorable MPFL anisometry/or
graft isometry from 0 to 30˚ of knee flexion
– the native MPFL function by protecting against
lateralpatellar dislocation in extension where the
graft is isometric and under tension
• Graft tension - measured intraoperatively,
comparison with the contralateral knee

35. • Koh and Stewart- suggested that the
reconstruction should permit 1 cm of lateral
translation in full extension or the equivalent of
two quadrants of lateral deviation with a firm end
point
• don’t disrupt the physis or perichondral ring
with femoral tunnel or socket drilling
– slightly less anatomic MPFL reconstruction can be
performedwithout drilling
• Most common adverse events- recurrent
apprehension, arthrofibrosis, pain and clinical
failure and patellar fracture

36. Trochleoplasty
• 85% of individuals with recurrent
patellofemoral instability have trochlear
dysplasia
• Indication:
– Aberrant patellar tracking (identified by a J sign on
clinical examination and a TT-TG distance of >10
mm)
– abnormal trochlear morphology

37. • Requirement-
– normal or nearly normal trochlear articular cartilage
– prior correction of any rotational malalignment
• Several different trochleoplasty procedures ,
technically demanding
• postoperative complications:
– iatrogenic cartilage damage, patellar incongruence,
overcorrection, arthrofibrosis and advanced arthrosis

38. Tibial Tubercle Transfer
• Medialization of the tibial tubercle decreases the
resultant lateral force vector acting on the patella and
consequently increases patellofemoral stability
• Indication: Recurrent instability associated with
– patella alta
– abnormal patellar tracking secondary to external tibial
torsion relative to the trochlear groove
– TT-TG distance of >15 mm anda Caton-Deschamps ratio of
>1.4
• Mainly two types
– Medial tibial tubercle transfer (Elmslie-Trillat procedure)
– anteromedialization of the tibial tubercle (Fulkerson
procedure)

39. • Selected plane of the osteotomy needs to be
individualized for each patient
• Contraindication:
– Skeletal immaturitywith an open tibial apophysis
– history of medial dislocations and patellofemoralarthrosis
• Postoperative TT-TG goals should be 9 to 15 mm
• A long osteotomy performed to maximize the surface
area and provide sufficient length for safe fixation with
a minimum of two screws to control both rotation and
translation
• obliquity of the osteotomy also customized to address
the individual deformity

41. • Complications :
– symptomatic hardware
– Fracture of the proximal part of the tibia
• Osteotomies can be combined with MPFL
reconstruction, trochleoplasty, or lateral
retinacular release as well as cartilage
restoration

42. Femoral Derotational Osteotomy
• Unrecognized excessive femoral anteversion
alters the forces across the patellofemoral joint,
with a greater laterally directed force vector.
• Cause of recurrent patellar instability and the
etiology of the failure of initial instability
treatment.
• done if an anteversion >20˚
• proximally in the intertrochanteric region or
distally in the supracondylar region

43. Algorithmic Approach with Graded
Recommendations

45. • Most of the time, combination of surgery is
required
• failure after surgery for recurrent instability,
– both residual anatomic abnormalities and
technical errors should be assessed and corrected.

46. Conclusion
• majority of investigators recommended
– recurrent lateral patellar instability should be
addressed surgically
• No clear consensus on a consistent surgical
algorithm
• Further study with larger sample size is
recommended.

47. References
• Weber AE, Nathani A, Dines JS, et al. An Algorithmic Approach to the
Management of Recurrent Lateral Patellar Dislocation [published
correction appears in J Bone Joint Surg Am. 2016 Jun 15;98(12):e54]. J
Bone Joint Surg Am. 2016;98(5):417-427. doi:10.2106/JBJS.O.00354
• Campbells’ Operative Orthopaedics 12th Edition
• Duerr RA, Chauhan A, Frank DA, DeMeo PJ, Akhavan S. An Algorithm
for Diagnosing and Treating Primary and Recurrent Patellar
Instability. JBJS Rev. 2016;4(9):01874474-201609000-00003.
doi:10.2106/JBJS.RVW.15.00102
• Zaffagnini, S., Dejour, D., & Arendt, E. A. (Eds.). (2010).
Patellofemoral Pain, Instability, and Arthritis. doi:10.1007/978-3-642-
05424-2

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