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Biomechanics Lecture 06

Structure, Movement and Injuries of Hand and Wrist

Movements of the Wrist

  • Sagittal and frontal plane movements
  • Rotary motion
  • Flexion
  • Extension and Hyperextension
  • Radial Deviation
  • Ulnar Deviation

 Structure of the Wrist

What are the radiocarpal joints?

  • condyloid articulations between the        radius and the three carpal bones
  • (these joints comprise the wrist)

Most wrist motions occurs at radiocarpal joint

  • Sagittal plane and frontal plane movements.
  • Closed pack position is in extension with radial deviation

What is the function of the retinacula at the wrist?

(these fibrous bands of fascia form protective passageways through which tendons, nerves, and blood vessels pass)

Lumbricals

Movements at the Wrist

What muscles contribute to flexion at the wrist?

  • flexor carpi radialis
  • flexor carpi ulnaris
  • palmaris longus

assisted by:

  • flexor digitorum superficialis
  • flexor digitorum profundus

What muscles contribute to extension at the wrist?

  • extensor carpi radialis longus
  • extensor carpi radialis brevis
  • extensor carpi ulnaris

assisted by:

  •  other wrist extensor muscles

Flexor carpi radialis and extensor carpi radialis longus and brevis à Radial deviation

Flexor carpi ulnaris and extensor carpi ulnaris à Ulnar deviation

Joint Structure of the Hand

  • Carpometacarpal (CM)
  • Metacarpophalangeal (MP)
  • Interphalangeal (IP)

Structure of the Joints of the Hand

What are the carpometacarpal joints?

  • the carpometacarpal joint of the thumb is a saddle joint
  • the other carpometacarpal joints are gliding joints

What are the intermetacarpal joints?

(irregular joints between the metacarpals that share joint capsules with the carpometacarpal joints)

What are the metacarpophalangeal joints?

  • condyloid joints between the rounded distal heads of the metacarpals and the concave proximal ends of the phalanges.
  • these joints form the knuckles of the hand.
  • Close packed position for MP joint is flexion and opposition

What are the interphalangeal joints?

(the proximal and distal interphalangeal joints of the fingers and the single                      interphalangeal joint of the thumb are all hinge joints)

  • Close pack position is full extension.

Movements of the Hand

What motions are permitted at metacarpophalangeal joints 2-5?  

  • flexion
  • extension
  • abduction
  • adduction
  • circumduction

THUMB is a different  from others??

Passive Tension in Extrinsic muscles

  • When the hand is relaxed and wrist moves from full wrist flexion to extension àDIP 12˚-31˚ and PIP 19˚-70˚ of flexion

 

Ø  Extrinsic Flexor Muscles of hand are more than twice as strong as the strongest extrinsic extensor muscles.

Ø  Strongest of extrinsic flexor muscles are flexor digitorum profundus and superficialis, contributing 80% of all flexion forces.

Movements of the Hand

Which muscles are responsible for motions of the hand?  

  • there are nine extrinsic muscles with attachments both proximal and distal to the wrist
  • there are ten intrinsic muscles with   both attachments distal to the wrist
  • CM Joints allow large ROM because similar to ball and socket joint

o   Digits 2-4 constrained by ligaments

  • MP joints allow flexion, extension, abduction, adduction and circumduction for digits 2-5
  • IP joints allow flexion and extension
  • Extrinsic Muscles
  • Intrinsic Muscles

INJURIES

 

Tendon Injuries

  • Jersey Finger- grabbing something and tearing the flexor tendon.
  • Mallet Finger- hitting something with the tip of a finger and causing the extensor tendon to tear.
  • Boutonniere deformity- extensor tendon injury affecting two joints of the finger.  It is an injury to the central tendon on top of the finger.

–     It may appear as a “jammed finger” that cannot be extended from the PIP joint.

–     Treatment should be in an extended position so the tendon can heal.

Boxer’s Fracture

  • Boxer’s Fracture is a term used for a fracture of one of the metacarpal bones of the hand. Classically, the fracture occurs transversely across the neck of the bone, after the patient strikes an object with a closed fist. Alternate terms include scrapper’s fracture or bar room fracture.

De Quervain’s Disease

  • It’s a  is a tendinitis condition.

“ painful inflammation of tendons on the side of the wrist at the base of the thumb. These tendons include the extensor pollicis brevis and the abductor pollicis longus. ”

  • The pain, which is the main complaint, gets worse with abduction of the thumb, grasping action of the hand and an ulnar deviation of the wrist.
  • Thickening and swelling can also be present

Carpal Tunnel Syndrome

  • Carpal tunnel syndrome (CTS) is a medical condition due to compression of the median nerve as it travels through the wrist at the carpal tunnel.
  • The main symptoms are pain, numbness, and tingling, in the thumb, index finger, middle finger, and the thumb side of the ring fingers. Symptoms typically start gradually.

Common Injuries of the Wrist and Hand

Sprains and strains fairly common, due to breaking a fall on hyperextended wrist

Certain injuries characteristic of sport type

–     Metacarpal fractures and football

–     Ulnar collateral ligament and hockey

–     Wrist fracture and skate/snowboarding

–     Wrist in non-dominant hand for golfers

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