Flexor Tendon Injuries
Hisham M. Awan
Flexor carpi ulnaris
Flexor carpi radialis (FCR)
Flexor pollicis longus (FPL)
Flexor digitorum superficialis (FDS)
Flexor digitorum profundus (FDP)
Important anatomic relationships
FCR is the closest tendon to the median nerve in the forearm.
There are nine tendons (FDS ×4, FDP ×4, and FPL) and one nerve (median nerve) in the carpal tunnel.
FPL is the most radial tendon in the carpal tunnel.
In the forearm, wrist, and hand, the FDS tendons lie superficial to FDP. At the level of the metacarpophalangeal (MCP) joints, FDS splits and FDP becomes superficial. FDS slips rejoin at Camper Chiasm and insert on the middle phalanx. FDP inserts on the distal phalanx (Figure 34.1).
Composed of bundles of collagen fascicles surrounded by epitenon, a surface that is crucial for gliding
Arterial supply—vinculae from digital arteries
Prevents bowstringing of flexor tendon
A2 and A4 are most important in fingers.
Oblique pulley is most important in the thumb.
Mechanism of injury
Most commonly results from penetrating trauma or lacerations to the palmar aspect of the hand or volar wrist/forearm
Jersey finger (see Chapter 35)—avulsion of FDP insertion on the distal phalanx due to forceful distal interphalangeal (DIP) joint extension during FDP contraction
Penetrating trauma or laceration to palmar hand or volar wrist/forearm
Weak or absent flexion of digit
Assess wounds for foreign bodies, identify injured structures, evaluate for evidence of arthrotomy.
Assess digital cascade.
Digit with a flexor tendon injury is held extended at rest relative to other fingers.
Persistent extension at proximal interphalangeal (PIP) or DIP joints during passive wrist extension is indicative of flexor tendon injury.
▲ Passive wrist extension normally causes flexion at MCP, PIP, and DIP joints (tenodesis effect).
Strength/range of motion
Loss of active flexion of digit
Test FDS and FDP for each finger (Figure 34.2)
Given proximity of nerves and vessels to finger flexor tendons, concomitant neurovascular injuries are common.
Document a thorough examination at the time of injury.
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