Sites of Compression
Proximal
Arcade of Struthers
- thick myofascial band, 1.5-2cm wide
- present in 70%
- 8cm proximal to medial epicondyle
- from medial head of triceps to medial intermuscular septum, superficial to nerve
Medial intermuscular septum
- with subluxation, nerve may impinge on it
Medial head of triceps
- hypertrophied (body builders)
Medial epicondyle
Tardy ulna nerve palsy / cubitus valgus
- compression due to valgus deformity of the bone
- previous supracondylar / lateral condyle fracture
Cubital tunnel / Osbourne's ligament
Anatomy
- walls are humeral & ulna heads of FCU
- floor is MCL
- roof is Osbourne's fascia (continuation of fibro-aponurotic covering of epicondylar groove)
Nerve compression
- occurs in flexion as Osbourne's fascia tightens
- MCL bulges out and tunnel becomes flattened ellipse
FCU
Nerve passes intramuscular for ~5cm
- penetrates fascial layer to lie on FDP
- proximal and distal compression possible
Other
A. Lesions in the groove
- medial epicondyle fracture / arthritic spurs / HO
- lipomas / ganglia / osteochondromas / synovitis / rheumatoid nodule
- infection (TB, leprosy) /bleeding (haemophilia)
B. Conditions outside the groove
- external compression
- anomalous anconeus muscle
C. Subluxation / Dislocation from the groove
- laxity / traumatic tear of fibro-aponurotic roof