Courtesy: Prof Nabil Ebraheim
The ability to flex the fingers consists of a system of flexor muscles in the forearm and their tendons are inserted into the bones of the fingers. A flexor tendon injury can cause loss of flexion (bending) of the fingers or thumb.
Anatomy
•Flexor digitorum profundus tendon : inserted into the distal phalanx
•Flexor digitorum superficialis tendon : inserted into the middle phalanx.
These retinacular structures keep the flexor tendons in place during flexion of the fingers. A1,A2,A3,A4. A2 & A4 pulleys are necessary to ensure efficient flexion of the fingers.
Flexor tendon injury zones
•Zone I: distal to superficialis insertion
•Zone II: fibroosseous tunnel : A1 pulley to zone I
•Zone III: carpal tunnel to A1 pulley
•Zone IV: carpal tunnel
•Zone V: prxiaml to carpal tunnel
Testing for injury
•Check the integrity of the profundus tendon : Kepp the PIP of the finger extended and see if the patient can flex the DIP.
•Check the integrity of the superficialis tendon: keep the other fingers extended and then see if the patient can flex the PIP joint of the involved finger.
•When multiple slips of the superficialis tendon are cut, identify the tendons properly. The superficialis tendons of the long and ring fingers are volar at the wrist.
Flexor digitorum profundus tendon avulsion (jersey finger)
•75% involving the ring finger
•Minimal clinical symptosm
•Get an x-ray for bony avulsions
Leddy classification
Type I
•Tendon retraction into the palm
•Re-insert the tendon into P3 within 7-10 days to avoid contracture and necrosis of the tendon
•Neglected injuries: DIP arthrodesis, staged reconstruction.
Type II
•Tendon retraction to the PIP level, can be inserted up till 6 weeks.
•May include a small bony fragment
Type III
Large bony fragment blocks proximal retraction FDP at the A4 pulley.
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