Posterolateral Rotatory Instability
Definition
Radius rotates externally in relation to the ulna
- posterior displacement of the radial head relative to the capitellum
- in flexion
Anatomy LCL
Radius rotates externally in relation to the ulna
- posterior displacement of the radial head relative to the capitellum
- in flexion
Throwing injury
- seen in the throwing athlete
- repetitive microtrauma / valgus stress
- develop laxity
Initially
- lose velocity / accuracy
Develop medial pain
40% ulna nerve symptoms
90% fusion rates
Lose70% sagittal plane ROM
Non union rates up to 12%
Decreased gait speed
Poor mobility over uneven surfaces
First generation (late 70s early 80s)
Results
Attempt to reduce outliers in all 3 planes of the knee
- improve alignment
- theoretically improve survival and outcomes
Image based
Pre-op CT
- uncommon
- resource heavy
1. Always resurface
2. Never resurface
3. Selectively resurface
Controversial
- literature divided on issue
Historically
- poor outcomes due to poor implant design
- now improved designs
- non resurfacing also improved due to better design and improved techniques in regard to tracking and rotation
UKA is intended to be load sharing
- correct to neutral or slight varus
HTO is a load-shifting / load-sparing procedure
- over correct into valgus
Advantages UKA
1. Rapid rehabilation
Meniscectomy
- resect 30%
- increases contact pressures 3.5 x
- shock absorbing capacity reduced to 20% normal
Results of partial & total meniscectomy are very poor in children
- meniscectomy in children is a last resort
- repair amenable tears
- treat others non-operatively
- only real indication for meniscectomy is locked knee not amenable to repair
Adolescent apophyseal avulsion
- treat non operatively
- unless displaced > 2 cm
Adult
- soft tissue avulsion
Usually associated with sporting activities
- skiing
- water skiing
Violent contraction
- knee extended
- hip flexing
Usually young patients
- 15 - 40
15% compound
High velocity injury
- MBA
- MVA
- pedestrian v car
- fall from height
EMST principles
- need for transfusion not uncommon