Injuries

Question 1

Claw hand

Answer 1

injury to ulnar nerve near elbow, between 2 heads of flexor carpi ulnaris

paralysis of medial half FDP –> inability to flex 4th/5th digits at DIP joints
paralysis of lumbricals –> inability to flex at MP joints

permanent extension of 4th/5th digits

Question 2

humeral shaft fracture

Answer 2

radial n. damage
functional loss of posterior forearm m.
inability to extend wrist and digits

triceps brachii (extension of forearm) normal bc innervated at origin of m. (above humeral shaft)

Question 3

mallet finger

Answer 3

lateral band tears (inserts on distal phalanx)

unopposed pull from flexor digitorum profundus –> flexes finger at DIP

Question 4

boutonniere deformity (button hole)

Answer 4

central band tears

lateral bands are pulled anteriorly to PIP
flexes digit at PIP, extends digit at DIP