Tools and Settings
Content
Questions and Tasks
Learning Outcomes: Students will be able to:
The wrist and hand are comprised of 29 bones, numerous joints, and over 30 muscles that perform a variety of complex movements. Included in these movements is thumb opposition, a unique characteristic that enables humans to grasp, manipulate, and use tools. In essence, the hand becomes the extension and expression of the brain. Because we walk upright, the joints of the upper extremity are free of weight bearing responsibility. This permits our hands to have increased mobility, allowing them to move freely through space and perform virtually any desired task.
Arches of the Hand: Enable the hand to close around the center of the hand, providing a more secure grasp.
Figure 1
Wrist Complex Joints
Movement at the wrist joint actually occurs at two joints, the radiocarpal joint and the midcarpal joint. For this reason, the wrist joint is often referred to as the wrist joint complex.
Located between the distal radius and radioulnar disc and the proximal row of carpals (scaphoid, lunate, and triquetrum).
Closed-Pack Position: Fully extended and radially deviated
Open-pack Position: Neutral and ulnar deviated
Located between the proximal row of carpal bones and the distal row of carpal bones and has a joint capsule separate from the joint capsule of the radiocarpal joint.
The ulna itself does not directly articulate with the carpal bones because of various soft tissue structures that exist there (i.e. articular disc), but does transmit approximately 20% of the load from the hand to the forearm when compression forces occur through the wrist.
Figure 2
Radiocarpal: Range of Motion
Flexion: 80° - Movement of the palm of hand toward the
anterior or volar aspect of the forearm.
Extension: 70° - Movement of the back of the hand toward the posterior or dorsal aspect of the forearm.
Radial Deviation: (abduction) 20° - Movement of the thumb side of hand toward the radial side of the forearm.
Ulnar Deviation: (adduction) 30° - Movement of the
little finger side of the hand toward the ulnar side of the
forearm.
Hand and Finger Joints
Carpometacarpal (arthrodial - triaxial)
2nd – located between the trapezoid and base of the 2nd metacarpal.
3rd – located between the capitate and base of the 3rd metacarpal.
4th – located between the hamate and base of the 4th metacarpal.
5th – located between the hamate and base of the 5th
metacarpal.
Note:
5th CMC joint occurs to allow for opposition
and reposition of the little finger.
1st Carpometacarpal (thumb – sellar or saddle):
Flexion: 40° (frontal plane)
Extension: 10° (frontal plane)
Abduction: 60° (sagittal plane)
Adduction: 10° (sagittal plane)
Medial Rotation: 45°transverse plane)
Lateral Rotation: 0° (transverse plane)
Opposition: a combination of the movements of flexion, abduction, and medial rotation that allow the thumb to oppose the other fingers.
Reposition: movement of the thumb back to the anatomical position.
The Palmar Aponeurosis
The deep fascia of the hand is continuous through the extensor and flexor retinacula with the antebrachial fascia. The central part of the palmar fascia – the palmar aponeurosis – is thick, tendinous, and triangular, and is continuous with the tendon of the Palmaris Longus (when present). The aponeurosis forms four distinct thickenings that radiate to the bases of the fingers and become continuous with the fibrous tendon sheaths of the digits. Many minute, strong skin ligaments (ligamentum retinacula cutis) extend from the palmar aponeurosis to the skin holding the skin close to the aponeurosis allowing only minimal sliding of the skin and thus promoting a firm grasp.
Figure 3
Wrist Joint Complex: Misc. Structures
The joint capsule is thickened and strengthened by the dorsal radiocarpal, palmar radiocarpal, radial collateral, and ulnar collateral ligaments.
This disc attaches to the distal end of the radius and ulna providing stability to the radiocarpal joint blending into the capsular and ligamentous structures of the wrist joint.
Attaches medially to pisiform and hook of the hamate, and laterally to scaphoid and trapezium forming the palmar border (roof) of the carpal tunnel. As a retinaculum if helps keep the flexor tendons from bowstringing during wrist flexion.
Attaches medially to the styloid process of ulna, trapezium, and pisiform bones, and laterally to the radial styloid process. As a retinaculum if helps keep the extensor tendons from bowstringing during wrist extension.
figure 5
Figure 6
Wrist Joint Complex: Ligaments
Located on the dorsal side of the wrist attaching from the dorsal surface of the distal radius to the carpal (scaphoid, lunate, triquetrum) bones. It functions to limit wrist flexion.
Located on the palmar side of the wrist attaching from the palmar surface of the distal radius to the proximal row of carpal bones. It functions to limit wrist extension.
Attaches from the styloid process of the radius to the scaphoid and trapezium. It functions to limit ulnar deviation.
Attaches from the styloid process of the ulna to the pisiform and triquetrum. It functions to limit radial deviation.
Figure 7
e
Figure 8
Carpal Tunnel
Located on the palmar surface of the wrist, the borders of the carpal tunnel are formed by the:
The structures that pass through the carpal tunnel are:
Note: all of the flexor tendons of the wrist and fingers pass through the carpal tunnel except for the Flexor Carpi Ulnaris, Flexor Carpi Radialis, and the Palmaris Longus.
figure 9
Carpal Tunnel Syndrome
A condition in which the median nerve that runs through the carpal tunnel is being compressed. This can be caused by inflammation, thickening of irritated tendons, or swelling that narrows the tunnel. This initially results in an alteration of sensation (tingling, numbness, and pain) to the palm side of the thumb, index and middle finger.
Worsening symptoms include muscle weakness, increased pain, decreased grip strength, and in chronic and/or untreated cases can cause muscle atrophy.
Figure 10
Guyon’s Canal Syndrome
A condition in which the ulnar nerve that runs through Guyon’s canal, located on the palmar side of the wrist and formed by two bones (pisiform and hamate) and the ligament that connects them, is being compressed. This initially results in a feeling of tingling in the little and ring fingers.
Symptoms may progress to a burning pain in the wrist and hand followed by decreased sensation in the little and ring fingers and even a gradual weakness in the intrinsic muscles of the hand making it hard to spread the fingers and pinch with the thumb.
Figure 11
The Dorsal Hood (Extensor Hood Mechanism)
The Dorsal Hood (also known as the Dorsal Hood Expansion or Extensor Hood Mechanism) is a fibrous aponeurotic expansion of the distal attachment of the Extensor Digitorum muscle on all four fingers. This structure serves as a moveable “hood” of tissue when the finger joints (both PIP and DIP) flex and extend. The Dorsal Hood originates on the dorsal, medial, and lateral sides of the proximal phalanx of each finger and splits into a central tendon and two lateral tendons. The central tendon inserts into the base of the middle phalanx. The two lateral tendons pass along the medial and lateral borders of the middle phalanx and converge to attach to the dorsal surface of the base of the distal phalanx.
It serves as an attachment site for the Lumbricals, Palmar Interossei, and Dorsal Interossei. As such, when these muscles contract, their “pull” is transmitted across the PIP and DIP joints causing them to extend. In addition, the extensor tendons of the Dorsal Hood are interconnected by fibrous bands known as juncturae tendinae (also known as intertendinous connections).
Figure 12
Figure 13
Muscles that Cross the Wrist
Wrist Flexors (Palmar Wrist):
Wrist Extensors (Dorsal Wrist):
Muscles of the Wrist – “Palmar Side”
Flexor Pollicis Longus
Origin:
Insertion:
Actions:
Nerve Innervation:
Figure 14
Flexor Carpi Radialis
Palmaris Longus
Flexor Carpi Ulnaris
Muscles of the Wrist – “Palmar Side” Continued
Flexor Digitorum Superficialis
Figure 15
Flexor Digitorum Profundus
Muscles of the Wrist – “Dorsal Side”
Extensor Carpi Ulnaris
Figure 16
Extensor Digiti Minimi
Extensor Digitorum
Muscles of the Wrist – “Dorsal Side” Continued
Extensor Indicis
Figure 17
Extensor Carpi Radialis Brevis
Extensor Carpi Radialis Longus
Extensor Pollicis Longus
Extensor Pollicis Brevis
Abductor Pollicis Longus
Intrinsic Muscles of the Hand – “Thenar” Muscles
Opponens Pollicis
Figure 20
Abductor Pollicis Brevis
Flexor Pollicis Brevis
Intrinsic Muscles of the Hand – “Hypothenar” Muscles
Flexor Digiti Minimi
Opponens Digiti Minimi
Abductor Digiti Minimi
Intrinsic Muscles of the Hand – “Intermediate” Muscles
Adductor Pollicis
Figure 21
Figure 22
Palmar Interossei
Dorsal Interossei
Lumbricals
Damage to the Median Nerve
Median Nerve Damage (Hand of Benediction)
Results from prolonged compression or injury to the Median nerve at the level of the elbow or upper arm. Results in an inability to flex the index and middle fingers. This is due to a loss of innervation to the 1 & 2 Lumbricles of the hand and the radial half of the Flexor Digitorum Profundus – supplied by the Median nerve. However, the Extensor Digitorum is left unopposed and continues to pull causing hyperextension at the MCP joints of these fingers. Typically only manifests when the person is asked to make a fist.
Figure 23
Damage to the Ulnar Nerve
Ulnar Nerve Damage (Ulnar Claw Hand)
A hand in ulnar claw position will have the 4th and 5th MCP joints hyperextended and the interphalangeal joints flexed towards the palm.
Figure 24
Damage to the Radial Nerve
Radial Nerve Damage (Wrist Drop)
Lack of innervation to the wrist extensors (The “E” in BEAST) would cause the wrist to drop when gravity acts upon it. The wrist flexors would be pulling against the denervated wrist extensors causing wrist flexion to occur. At the same time, the supinator muscle would also lack innervation and therefore the forearm would be pulled into a pronated position.
Figure 25
A Few Wrist and Hand Review Questions