Mediocarpal art, Os pissiformis art and sulcus et canalis carpi

Question 1

Mediocarpal artriculation

Answer 1

• Proximal rox of carpal bones (excluding os pisiformis) are joined with the distal row of carpal bones
• On the radial side the artricular head is created by os scaphoideum, the joint pit is created by little planes on os trapezium, os trapezoideum and on the ulnar side (medially) by os capitatum
• On the ulnar side the joint head is formed by os capitatum and os hamatum, the joint pit is created by little planes on os scaphoideum, os lunatum and os triquetrum
• Joint slit has a transverse”S” shape
• Carpal bones connected by lig. intercarpea dorsalia, palmaria et interossea (missing between os trapezium and os trapezoideum)

Question 2

Joint capsule and cavity of the mediocarpal joint

Answer 2

• Joint capsule is attached to margins of joint surfaces
• Mediocarpal joint cavity communicates with the joint cavity of art. metacarpophalangeales II.-V. (reason why there is no interosseal ligament between os trapezium and os trapezoideum

Question 3

Ligamentum radiocarpeum palmare et dorsale and ligamentum ulnocarpeum palmare et dorsale

Answer 3

• Ligamentum radiocarpeum palmare et dorsale runs from processus styloideus radii onto palmar and dorsal sides of carpal bones
• Ligamentum ulnocarpeum palmare et dorsale instead run from the processus styloideus ulnae

Question 4

Radiate carpal ligament

Answer 4

• Group of about 7 fibrous bands
• Diverge in all directions on the palmar surface of the carpal bones
• Majority of the bands radiate from the capitate bone to the scaphoid, lunate, and triquetral bones

Question 5

Ligamentum arcuatum carpi dorsale and ligamentum arcuyatum carpi palmare

Answer 5

• The dorsal arcuate lig. runs from dorsal side of os scaphoideum onto the dorsal side of os triquetrum
• The palmar one is just on the palmar side

Question 6

Radiocarpal artriculation and mediocarpal artriculation functional unit

Answer 6

• Ellipsoidal joint
• Movement alond two axis: palmar/dorsal hand flexion and ulnar/radial hand duction
• Combining both movement types results in circular movements (circumduction)

Question 7

Os pisiformis artriculation

Answer 7

• Joint surfaces are on the os pisiformis and on the central side of os triquetrum
• Joint capsule attached to margins of joint surfaces
• Ligamentum pisohamatum runs from os pisiforme to hamulus ossis hamati
• Ligamentum pisometacarpeum - joins the pisiform to the base of the fifth metacarpal bone (sometimes also the 4th)
• Os pisiforme is a sesamoidal ossicle in the tendon of the m. flexor carpi ulnaris

Question 8

Sulcus et canalis carpi

Answer 8

• Eminentia carpi radialis - tuberculum ossis scaphoidei and tuberculum ossis trapezii protrude into the palm on the radial side
• Eminentia carpi ulnaris - projection on the ulnar side formed by hamulus ossis hamati and os pisiforme
• Sulcus carpis, a concave sulcus on the palmar side, is bridged by a strong fibrous retinaculum - retinaculum flexorum, which connects both eminentiae carpi
• This creates the canalis carpis through which the flexor tendons of the hand and fingers as well as the n. medianus pass into the palm