Understanding Mallet Finger and Boutonniere Deformity

This video tutorial reviews the structure and function of the extensor expansion, focusing on the extensor tendon and its interaction with intrinsic muscles. It explains the formation of the extensor hood and its division into middle and lateral slips, which are crucial for finger movement. The tutorial includes a cadaver dissection to illustrate these structures and discusses clinical presentations like mallet finger and boutonniere deformity, highlighting their causes and effects on finger joints.

What is the primary function of the extensor hood?

• To flex the fingers

• To protect the palm

• To provide support over the dorsum of the metacarpal phalangeal joint

• To attach muscles to the bone

How many slips does the extensor hood divide into?

• Four

• Two

• Three

• Five

Where does the middle slip attach?

• Base of the distal phalanx

• Base of the middle phalanx

• Base of the metacarpal

• Base of the proximal phalanx

What is the role of the lateral slips in the extensor expansion?

• They unite to form the terminal slip

• They protect the extensor tendon

• They attach to the base of the proximal phalanx

• They provide flexion to the fingers

What is the significance of the terminal slip in the extensor expansion?

• It allows for flexion of the fingers

• It attaches to the base of the distal phalanx

• It provides support to the wrist

• It connects to the metacarpal

What is a common result of a tear in the terminal slip?

• Mallet finger

• Boutonniere deformity

• Carpal tunnel syndrome

• Trigger finger

What happens to the PIP joint in a boutonniere deformity?

• It flexes

• It rotates

• It hyperextends

• It remains neutral

How do the lateral slips contribute to the boutonniere deformity over time?

• They migrate dorsally

• They become extensors of the PIP joint

• They become flexors of the PIP joint

• They remain unchanged

What is the clinical presentation of an extensor lag?

• The DIP joint is kept in a position of extension

• The DIP joint is kept in a position of flexion

• The PIP joint is hyperextended

• The MCP joint is flexed

Which joint is primarily affected in a mallet finger injury?

• DIP joint

• PIP joint

• MCP joint

• CMC joint