The wrist
What is needed for functional ROM at the wrist?
- 10-15 degrees extension and 10 degrees of Ulnar deviation - wrist extension and ulnar deviation are the most important because they allow for max grip
Extrinsic Ligaments of the wrist
- connect carpals to radius or ulna Anterior: palmar radiocarpal ligament Lateral: Radial collateral ligament Medial: Ulnar collateral ligament Posterior: dorsal radiocarpal ligament Ulnocarpal complex Palmar Ulnocarpal ligament
ulnar deviation
- extensor carpi ulnaris and flexor carpi ulnaris act to stabilize in extension - if flexor carpi ulnaris is unopposed the wrist will be in flexed position which is not ideal position for gripping activities
radial deviation
- generate 15% greater isometric torque than ulnar deviation - extensor carpi radialis longus, extensor carpi radialis brevis, extensor pollicis longus, flexor carpi radialis, abductor pollicis longus, flexor pollicis longus - Extensor carpi radialis and flexor carpi ulnaris are synergists and antagonists to allow proper positioning for functional activities
carpal instability
- mechanical stability that will fail like a train derailment if there is compression from both ends; rotational collapse - lunate is the most frequently dislocated carpal bone - collapse can occur volarly or palmarly - will affect the muscles that cross the wrist due to alteration on the length tension relationship - due to ulnar tilt a pathological process such as RA that weakens ligaments will allow the carpal bones to drift ulnarly
Extrinsic Ligaments of the wrist: Dorsal Radiocarpal ligament
- radius to dorsal scaphoid and lunate - taut in full flexion; - guides the arthrokinematics
ROM Radial deviation
- same arthrokinematics as ulnar deviation - hamate and triquetrum seperate - increased tension in medial palmar intercarpal ligament and palmar radiocarpal ligament -most motion occurs at midcarpal joint as radius is a bony limit
Scaphoid stability
- scaphoid during flexion and extension moves with action limited by scapholunate ligament - any damage to this ligament affects stability of the wrist (often broken bone; does not have a great vascular supply)
Extrinsic Ligaments of the wrist: Palmar radiocarpal ligament
- separate from the joint capsule [radioscahpocapitate, radiolunate; radioschapolunate] - stronger and thicker than dorsal with tension at all position - maximally taut at full wrist extension
What is contained inside of the carpal tunnel?
-contains tendons of extrinsic flexors (except for Flexor carpi radialis) and median nerve
Where do the wrist flexors originate?
-originate at medial epicondyle
Midcarpal Joint
-proximal row: scaphoid, lunate, triquetrum, -distal row: trapezium, trapezoid, capitate, hamate; moves as fixed unit with MC also functions as foundation of transverse and longitudinal arches - no single joint capsule; intercarpal articulations and capsule
Extrinsic Ligaments of the wrist: Radial Collateral ligament
-radius to scaphoid, trapezium, and transverse carpal ligament; -taut with extension and ulnar deviation - more developed palmar laterally (additional lateral support of joint is supplied by AB pollicis longus and extensor pollicis brevis)
Wrist Function depends on...
-shoulder for stability -elbow to move to/form body - forearm to adjust position --->loss of function at wrist: cannot adjust with shoulder or elbow
Extrinsic Ligaments of the wrist: Ulnar collateral ligament
-ulna to triquetrum -limits radial deviation
Which extensor muscle is recruited first?
Extensor carpi radialis brevis first then extensor carpi ulnaris then extensor carpi radialis longus
Flexion, Extension, Radial deviation and ulnar deviation ROM
Flexion = 65-80 Extension = 60 -75 Radial Deviation = 0 - 20 Ulnar Deviation = 0 - 40
what are the primary digit flexors?
Flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus
ROM ulnar deviation
Radiocarpal: scaphoid, lunate and triquetrum roll ulnarly and slide radially Midcarpal: capitate rolls ulnarly and slides radially - full ROM triquetrum contacts the disc - wrist is stabilized by the compression of the hamate against the triquetrum - increased tension in lateral palmar intercarpal ligament and palmar ulnocarpal ligament controls the motion - equal motion at both joints
Triangular Fibrocartilage Complex
TFC is an articular radioulnar disc, triangular shaped fibrocartilage and fibrous attachments; that is compressible adding to wrist ROM - attached to palmar and dorsal capsular ligament to forma triangle - 80% of disc is avascular so it cannot heal - Functions as a part of the distal radius to transmit forces, reinforce the ulna side of the joint - TFCC binds the ends of the radius and ulna permitting the radius with attached carpals to rotate freely over fixed ulna - meniscus homologue fills the space of the ulnocarpal complex
What is the axis of motion of the wrist complex?
axis of motion is capitate. - motion occurs at radiocarpal and midcarpal simultaneously
What is the site of attachment for palmaris longus?
carpal tunnel
What limits radial deviation of the wrist?
carpals against the radial styloid process
What is the wrist complex made of?
composed of radiocarpal, midcarpal and intercarpal joints
Extinsic Ligaments of the Wrist: palmar ulnocarpal ligament
disc to lunate and triquetrm taut in wrist extension and ulnar deviation
Gripping activities
during griping activities hold wrist in 35 degrees of extension and 5 degrees of ulnar deviation to optimize the length tension relationship of finger flexors (allows up to 3x amount of grip strength)
When is contact greatest in the radiocarpal joint?
during wrist extension and ulnar deviation [closed pack postion]
What are the primary wrist flexors?
extensor carpi radialis longus extensor carpi radialis brevis extensor carpi ulnaris
what are the primary wrist extensors?
extensor digitorum, extensor indices, extensor digiti minimi, extensor pollicis longus
Extensor retinaculum
from styloid process of ulna to radius - prevents bowstringing of tendons
How does the pisiform bone affect flexor carpi ulnaris?
it acts as a sesamoid to increase its moment arm
which wrist bone is most frequently dislocated?
lunate
The wrist functions to..
maintain optimal length/tension relationship and adjust grip
What are the primary wrist flexors?
palmaris longus, flexor carpi radialis, flexor carpi ulnaris FCR and FCU also radially/ulnarlly deviate
In the midcarpal joint, where does most of the motion occur?
predominately in the medial compartment (capitate, hamate, scaphoid, lunate, triquetrum)
Radiocarpal Joint
proximal: radius, triangular fibrocartilage complex (TFCC), [accepts 20% of compressive force] distal: scaphoid, lunate, triquetrum (during full ulnar deviation)
ROM extension
radiocarpal joint: Lunate rolls dorsally on radius and slides palmarly midcarpal joint: capitate rolls dorsally on lunate and palmarly - both joints are convex moving concave - allows about 60 degrees of wrist extension - elongation of palmar radiocarpal, palmar capsule, and wrist and finger flexor muscles - closed packed position and most stabilized to allow weight bearing activities
ROM flexion
radiocarpal joint: lunate rolls palmarly on radius and slides dorsally midcarpal joint: capitate rolls palmarly on lunate and slides dorsally
What makes up the central column of the wrist?
radius, lunate, capitate, and 3rd MC
What ROM is required to complete ADLs?
require 40 degrees of sagittal motion; 10 degrees of RD and 30 degrees of UD
Intrinsic ligaments of the wrist
short, intermediate or long - short ligaments: stabilize and unite bones and allow them to work as a functional unit - intermediate and long ligaments: add stability and connect carpals --- intermediate: lunotriquetral, scapolunate, scapotrapezoid --- long: palmar and dorsal intercarpal
Position of the wrist alters..
the function of the hand
Which side of the carpal tunnel is concave?
the palmar side
Why is ulnar deviation increased?
the radius has an ulnar tilt
Why does the wrist have more flexion than extension?
the radius is tilted palmarly about 10 degrees resulting in more flexion than extension
How are the extensor muscles organized?
the tendons are housed in 6 separate tunnels
What acts as the roof to the carpal tunnel?
the transverse carpal ligament
Why is extensor carpi ulnaris active during active wrist flexion?
to stabilize the ulnar side of the wrist to keep wrist in neutral
What makes up the Ulnocarpal complex?
triangular fibrocartilage, ulnar collateral ligament, and palmar ulnocarpal ligament
In the wrist complex, what are the benefits of two joint working together?
two joints working together allow increased ROM with less exposed articular surface; less structural pinch at end range