Recurrent dislocation of Patella

Recurrent dislocation of the patella occurs episodically as the force is generated, and disturbs the patellofemoral kinematics.

Important terms:

• Medial patella-femoral ligaments
• Trochea hypoplasia
• Patella Alta
• TT-TG ( Tibial tuberosity- Trochlear groove )

Definitions:

1. Congenital Patella dislocation occurs since birth
2. Acute patella dislocation is an acute con
3. Old unreduced patellar (permanent) dislocation, where dislocation is chronic and persists with all knee movement
4. Recurrent patellar dislocation: episodic
5. Habitual patellar dislocation occurs during each movement of flexion of the knee
6. Patella subluxation

In recurrent dislocation

Features:

With the increased number of dislocations

• Apposing aspects of patella eroded and thinned
• Lateral femoral condyle
• The medial capsular structure will become stretched
• The patellar tendon becomes elongated
• Patella ride is high, re-displacement occurs with more incredible case

The predisposing factor for dislocation

1. Genu valgum
2. Shallow lateral femoral condyle
3. Elongated patella tendon (high riding-patella Alta)
4. Deficient Vastus medialis
5. Tight lateral structures
6. External tibial torsion
7. Internal femoral torsion
8. Lateral insertion of the patella
9. Medial condyle laxity
10. Deformed patella (shallow patella groove)
11. Abnormal attachment of iliotibial tract on the patella
12. Soft tissue abnormality:
    1. Hyperlaxity of soft tissue
    2. Cerebral Palsy, Downs syndrome
    3. CTD

On examination:

Genu valgum

Squinting of patella

Q-angle

Patella Apprehension test (30 degrees of flexion: gently push laterally: apprehension)

Patella tilt test

Patella tracking: J-sign

Roentgenographic finding

Views:

1. PA in 45-degree flexion
2. True lateral
3. Merchant view

Lateral View

Blumensant’s line:

The lower border of the patella lies typically at the line projected forward from the intercondylar notch

In patella Alta, the patella is well above the line

PA view

Valgus angle

Q angle is measured

The angle formed by the line of pull of quadriceps and vertical line measures less than 20 degree

Angle >20 degrees: predispose to lateral displacement of the patella

Tangential patellar view

1. Lateral tilting: increase in joint interval beneath medial patellar facet
2. Subluxed patella
3. Shallow lateral femoral condyle
4. Medial femoral condyle: degenerative changes over the surface that are opposed to the medial patella facet
5. The osteochondral fragment is usually present over the medial border of the patella
6. Patellofemoral arthritis
7. Sulcus angle: N: <144 degrees

                         If >144 degrees, its called dysplastic trochlea

Treatment Options

Conservative

• Patella tapping
• Gluteal strengthing exercises
• Closed chain quadriceps exercises (1^st correct external malalignment: eg. Genu valgum)

Surgery

• Align quadriceps apparatus to a more medial position
• Broadly divided into
  • PROXIMAL REALIGNMENT PROCEDURE
  • DISTAL REALIGNMENT PROCEDURE

And combined given by D.P. Bakshi

Types of surgical procedures are determined by following anatomical/ pathological features

1. Isolated lateral release of extensor retinaculum is never sufficient
2. In genu-valgum, correction of deformity can correct the problem
3. High-riding patella:
   1. In skeletally mature : (Hauser) distal transfer of tibial tuberosity( C.I. in growing child)
   2. In skeletally immature: medial transposition of the patella tendon
4. Trochlea dysplasia: Trochleoplasty/ Albee’s operation
5. No, skeletal deformity: Construction of medial patella-femoral ligament and lateral release done

Procedures for recurrent dislocation of the patella

Hauser Operation

Tibial tubercle and attached patella tendon, transplanted medially and distally

• Fulkerson’s osteotomy: Variant of Hauser

Anteromedial transfer of tibial tuberosity

Goldthwaite-Roux operation

Patella’s tendon is split longitudinally and the lateral half is drawn medially are attached to the inner border of the patella tendon

Tendon transplantation

The inner hamstring attaches to the inner border of the patella

Albee’s Operation

 When lateral femoral condyle is shallow

Osteotomy is done at the lateral femoral condyle in the frontal plane

Anterior fragment of bone elevated and maintained by bone graft

Simple Imbrication

The inner third of the capsular covering is freed from the patella and imbricated over lateral 2/3^rd

Elmslie-Trillant Procedure

MPFL reconstruction and medialization (tibial tubercle osteotomy then medialized) + distalization as patella is high