Size
2 x as strong as ACL
About the same length as ACL 38 mm
Cross sectional area 150% of ACL
13 mm diameter (thicker)
2 Bundles
1. Anterolateral
- most important
- double the size of the posteromedial
- tight in flexion
- try to reconstruct this bundle
LHB primary function is humeral head depressor
Also accelerate / decelerate arm in overhead sports
Biceps problems usually occur with other pathology
- rotator cuff / instability
3 main problems
1. Degeneration
Second most common hindfoot after calcaneal fractures
Aviators Astragalus
Fall from height
- hyper-dorsiflexion injury
- neck of talus strikes the anterior tibia
More than half surface covered by articular cartilage
- medial articular wall straight
- lateral articular wall curves posteriorly
Mallet
- DIP flexed
- MTP / PIPJ neutral
Hammer
- PIP flexion
- DIPJ neutral / extended
Simple - MTP not involved
Complex - MTP hyper-extended
Claw
- PIPJ and DIPJ flexed
- MTPJ hyperextended
Curly toe
- PIP and DIP flexion
Able to achieve relatively high level of function after STJ fusion
- previously believed that isolated STJ fusion should not be performed
- believed that triple arthrodesis was operation of choice for hindfoot
- STJ fusion has superior result with less stress on AJ
Average loss of DF 30% / PF 10%
Position of hindfoot determines flexibility of transverse tarsal (CCJ & TNJ) joints
- imperative that fusion be positioned in ~ 5o valgus
6th compartment
- fibro-osseous tunnel overlying 1.5 cm to 2.0 cm of distal ulna
- held tight by the extensor carpi ulnaris tendon sheath
- the extensor retinaculum passes around the ulna to insert on the palmar aspect of the carpus
- extensor retinaculum is a separate structure from the ECU tendon sheath
Forced supination, palmar flexion, and ulnar deviation
Nerve supply
- C7, C8, T1
- nerve picks up some branches of C7 from the lateral cord
Origin
- direct continuation medial cord
- runs between the brachial artery and the vein in the arm
- behind MCNFA
Arm
- pierces the medial intermuscular septum to run in posterior compartment
- runs anterior to the triceps
Elbow
Avascular necrosis & subsequent disintegration of lunate
50-75% history of trauma
Occasionally seen in sickle cell / steroid use
Trauma disrupting vascularity
- single incident with disruption of blood supply
Dorsal Intercalated Segmental Instability / CID
Scapholunate joint
- C shaped
- 2-3 mm thick dorsally with transverse fibres
- thin palmar
Dorsal extrinsic ligaments
- V shaped, onto trapezium
Extremely uncommon
Stability provided by joint capsule /costoclavicular & interclavicular ligaments
Recurrent instability uncommon
Many apparent dislocations in adolescents may be growth plate injuries
-will remodel without treatment
If OA from chronic dislocation may resect SCJ