Rote memorize this info. Then answer the questions at the end. No pain no gain.
Boutonniere finger deformity
- PIP flexion with DIP hyperextension.
- Common in rheumatoid arthritis.
- Frequent causative injury is blow to the dorsal aspect of a bent finger at the middle phalanx.
- Leads to disruption of the extensor central slip (part of the extensor tendon that attaches to the middle phalanx), resulting in forced flexion of the PIP joint. The lateral slips (bands) then move to the volar/anterior aspect of the finger. Yes, that sounds absurdly confusing, but what you need to memorize is this:
- Treatment is splinting of the finger with the PIP joint in extension for 4-6 weeks, but if surgery is performed, it involves “relocation of the lateral bands dorsally.”
Swan neck deformity
- DIP flexion with PIP hyperextension.
- Common in rheumatoid arthritis.
- Frequent causative injury is blow to the tip of the finger resulting in disruption of the terminal extensor tendon. May start as a mallet finger (mere forced flexion of the DIP) that leads to volar plate laxity and hyperextension of the PIP.
- Treatment is with splinting for 6-8 weeks.
Mallet finger
- DIP flexion due to extensor tendon injury from forceful blow to the fingertip.
- Tip can be passively extended but cannot maintain position.
- Is a cause of swan-neck deformity if not splinted.
Jersey finger
- DIP extension due to flexor digitorum profundus tendon injury.
- Most often seen in sports where the player grabs an opponent’s jersey with the fingertips while he or she runs away.
- Occurs in the ring finger in 75%.
- Treatment is usually surgical.
Ulnar claw / claw hand
- Ulnar nerve injury at the level of the palm, leading to loss of function of the medial two lumbricals.
- Since the lumbricals flex the MCPs and extend the PIP and DIPs, paralysis results in extension at the MCPs and flexion at the PIP and DIPs.
- The flexion in the PIP and DIPs is due to unopposed action of the flexor digitorum profundus and superficialis.
- Seen in cyclists / motorcyclists due to chronic compression by handlebars.
Hand of benediction (Pope’s blessing)
- Median nerve injury at the level of the elbow resulting in inability to flex the 1st through 3rd fingers when asked to make a fist.
- Caused by loss of function of the lateral two lumbricals, flexor digitorum profundus/superficialis, flexor pollicis longus/brevis, and opponens pollicis.
- Frequently confused with ulnar claw because they look similar.
Anterior interosseous syndrome
- Inability to make the “OK sign” by touching the tips of the thumb and index fingers together.
- Palsy of the flexor digitorum profundus of the 2nd and 3rd digits (cannot flex DIPs), as well as flexor pollicis longus (PIP of thumb), all of which are innervated by the anterior interosseous branch of the median nerve.
- Caused by various types of trauma above and below the elbow, e.g., supracondylar fractures with hemorrhage into deep musculature; open reduction of forearm fractures.
Ape hand
- Loss of function of opponens pollicis, leading to an inability to oppose (thumb to pinky) and appose (thumb to other fingers).
- Usually due to injury to recurrent branch of median nerve (but ulnar nerve innervates opponens pollicis in 20%).
- Thenar eminence wasting is characteristic longer term sequela.
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