Epidemiology
Rare
Usually bilateral
Diagnosis age 3 and after
- patella ossifies
- abnormal gait
Etiology
Idiopathic
Syndromic - Down's / Larsen's / Arthrogryposis
Pathology
Persistent lateral patella dislocation
Trochlea dysplasia / hypoplastic lateral femoral condyle
Hypoplastic flat patella
Criteria
1. Permanent lateral patella dislocation
2. Limited active knee extension
3. Unrestricted passive knee ROM
4. Absence of the patella in the femoral trochlea groove at birth
Clinical
Toddler with abnormal gait
- fixed flexion knee
- valgus
- lateralized patella
Xray
Patella doesn't ossify until 3 years of age
Used from: Nguyen et al Cureus 2021
Ultrasound
Early, simple diagnosis
MRI
Need sedation
Used from: Pedrotti et al J Orthop Case Report 2021
Operative management
Timing
Early surgery - need time for PFJ to remodel
Technique
Roux-Goldthwaite and Modified Roux-Goldthwaite
Vumedi congenital patella dislocation video
Midline incision
- large lateral release
- VY quadriceps lengthening
- medial plication
- Goldthwaite procedure
Roux-Goldthwaite procedure
- detach lateral half of patella tendon and pass under medial half
- suture to tibia or MCL
Modified Roux-Goldthwaite procedure
- detach medial half of patella tendon
- suture to MCL
+/- medial hemi-epiphysiodesis to correct valgus
Results
- 80 cases of congenital patella dislocation treated with surgical realignment
- mean age 3 years
- redislocation rate 2%
- improvement in trochlea dysplasia post surgery / patella groove reformed