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What is the most common instability pattern in the elbow?
Posterolateral rotatory instability.
What is an Osborne-Cotterill lesion?
An avulsion injury of the posteroinferior capitellum most commonly seen in patients with chronic posterolateral rotatory instability.
What is the main static lateral stabilizer of the elbow?
The lateral ulnar collateral ligament (LUCL).
What is the main stabilizer against valgus stress?
The anterior part of the ulnar (medial) collateral ligament.
Findings:
- elbow joint effusion
Bones:
- posterolateral subluxation of the radial head in relation to the capitellum
- mild bone marrow oedema of the anterior and posterior radial head and the posterior capitellum
- peripherally sclerosed osseous fragment with mild proximal marrow oedema distal to the medial (ulnar) epicondyle, and several smaller ones posterior to the capitellum consistent with old avulsions
Ligaments:
- partial tear of the lateral ulnar collateral ligament (LUCL)
- partial tear of the radial collateral ligament (RCL)
- a tear of the posterior bundle of the ulnar collateral ligament (UCL)
Muscles and tendons:
- a musculotendinous strain of the extensor carpi ulnaris origin
- myotendinous injury of the flexor digitorum superficialis muscle
- myotendinous injury of the brachialis muscle
- a tear of the insertion of the anconeus muscle
- unremarkable distal biceps tendon
Impression:
- Multi-ligament injury of the elbow joint with posterolateral subluxation of the radial head and Osborne-Cotterill lesion compatible with a posterolateral rotatory instability pattern.
- Myotendinous injuries of the brachialis and flexor digitorum superficialis muscle.
- Old avulsion fracture of the medial epicondyle suggestive of an old elbow injury possibly an old dislocation.