Wrist / Hand Complex Flashcards
Wrist (Carpus) Complex
The radiocarpal and midcarpal joints
Major contribution of the Wrist Complex
-Control length-tension relationship in the multiarticular hand muscles
-Allow fine adjustment of grip
Wrist muscles designed for …
balance and control vs force production
Radiocarpal joint composed of:
Proximally:
Radius
Radioulnar disc
Distally:
Scaphoid
Lunate
Triquetrum
Radiocarpal joint articulation
Scaphoid w/ lateral radial facet
Lunate w/ medial radial facet
Triquetrum w/ triangular fibrocartilage complex TFCC)
Midcarpal joint composed of:
Scaphoid
Lunate
Triquetrum
Trapezium
Trapezoid
Capitate
Hamate
Wrist complex
Biaxial
Flexion/extension around coronal axis
Radial / Ulnar Deviation around A-P axis
Radiocarpal joint surface is…
Oblique and angles slightly volarly and ulnarly
Normal angle inclination: 23 deg (Ulnar)
11 deg (Volar)
Palmer / Volar Ligaments
-Palmer Radiocarpal Ligament
-Radial Collateral Ligament
-Palmer Intercarpal Ligament
-Transverse Carpal Ligament
Dorsal Ligaments
-Dorsal Radiocarpal Ligament
-Dorsal Intercarpal Ligament
-Ulnar Collateral Ligament
Importance of the Scaphoid
-Greatest mobility of the proximal carpal bones
-Acts as a link between the proximal and distal carpal rows
Triangular Fibrocartilage Complex (TFCC)
-Articulates with triquetrum and partially with the lunate
-Radioulnar disc is a continuation or the articular cartilage of the radius
Wrist Movement
Open packed-neutral between flex/ ext
Closed packed-full ext and radial deviation
Wrist flexion Normal Range
65-85 deg
Wrist Extension Normal Range
60-85 deg
Radial deviation Normal Range
15-21 deg
Ulnar deviation Normal Range
20-45 deg
Volar Wrist Musculature
6 muscles cross volar surface of wrist and contribute to wrist flexion
PL, FCR, FCU, FDS, FDP, FPL
Carpal Tunnel
FDS tendons
FDP tendons
FPL tendon
Median nerve
Dorsal Wrist Musculature
9 muscles cross the dorsal aspect of wrist and contribute to wrist extension
Extensor retinaculum provides 6 distinct compartments for these muscles
Compartment 1 and 2
(dorsal)
- APL, EPB
- ECRB, ECRL
Compartment 3 and 4
(dorsal)
- EPL
- ED, EI
Compartment 5 and 6
(dorsal)
- EDM
- ECU
Flexion/Extension
Carpals on radius = convex on concave
Opposite roll and glide
Flexion; scaphoid tends to move with the distal carpal row with the proximal row following
Extension initiated by distal carpal row
Radial/ Ulnar Deviation
*Ex: With Radial Deviation
-Carpal complex slides ULNARLY
on the radius
-Flexion of PROXIMAL carpal rows
-Extension of DISTAL carpal rows
-Full Radial Deviation puts the radiocarpal and midcarpal joints in close-packed
FOOSH
(Fall on an Outstretched Hand)
Most common trauma to the radiocarpal joint
Kienbock’s Disease
-Avascular necrosis of the lunate
-Usually seen in relation with ulnar negative variance
-Due to abnormal force distribution across the radiocarpal
Ulnar Positive Variance
-POSITIVE variance: often seen after a distal radius fx with healing in a shortened position
-Present with pain at end range ulnar deviation / pronation
Dorsal Intercalated Segmental Instability (DISI)
-injury to ligaments stabilizing lunate + scaphoid
-Scaphoid (flex), lunate (extend)
-Subluxation of scaphoid occurs with compressive loading of wrist
Volar Intercalated Segmental Instability (VISI)
-lunate and triquetrum lose ligamentous stability
Scapholunate
Advanced Collapse
Wrist (SLAC)
-Degenerative changes at the radioscaphoid joint
-progression to intercarpal joints
-capitate can eventually sublux
Hand Complex
Comprised of:
-5 digits
-19 bones distal to the carpus
Digits include:
-Carpometacarpal joint (CMC)
-Metacarpophalangeal joint (MP)
-2 interphalangeal joint (IP); proximal and distal
-Thumb has only one (IP)
Extrinsic Muscle Group of Thumb
FCL, EPL, EPB, AbPL
Intrinsic Muscle Group of Thumb
OP, FPB, AbPB, AdP, 1ST palmar interossei
Thumb Structures
1st CMC Joint
Saddle joint with 2 DOF
Flex/ ext
ABd/ ADd
Primary function is opposition = abd followed by flex followed by add
Almost all Prehension;
Fine motor and grasp
CMC arthritis
-Most common pathology
-Trapezium and 1st metacarpal affected due to degenerative changes
-Pain with prehension
Common elective surgery of the hand
CMC - Deep Transverse Metacarpal Ligament
-Base of metacarpal and distal carpal row
-Spans btw 2nd and 4th metacarpal heads
-Helps w/ CMC stab and limits abd
Blends with ant. joint capsule of e/digit
-Prevents entrapment of the FDP with MCP flex and maintains the interossei in a position dorsal to the ligament
CMC - Opponens Digiti Minimi (ODM)
-only muscle to exclusively impact movement of a CMC joint
-flex and rotate the 5th metacarpal along it long axis
Acts on CMC joint ALONE
Palmer Arches of Hand
Proximal, distal and longitudinal arches
Allow palm and digits to conform to objects being held
-Max surface contact
-Greatest stab
-Increasing sensory feedback
Metacarpophalangeal
(MCP) Joints
2 DOF:
Flex/ ext
ABd/ ADd
Metacarpal head -convex
Base of prox phalanx -concave
Reinforced by Deep Transverse Metacarpal Ligament
Flexion/ extension of MCP joint
Flexion- volar roll and volar glide of phalanx on MC
Extension- dorsal roll and dorsal glide of phalanx on MC
Interphalangeal (IP)
Joints
Synovial hinge joint
1 DOF
Volar plates reinforce IP joint capsules
IP ligaments
Collateral lig. proper -taut with MCP flex
Accessory collateral lig. -taut with ext
What other functions IP ligaments have?
Stability to MCP and IP during AROM
Stability with varus and valgus stress
Volar plate
reinforces IP joint capsule
improves stab
limits hyperext.
Sagittal Bands
Help to stabilize the volar plates over the 4 MC heads
Connects volar plate to the extensor digitorum communis tendon and extensor expansion
Anatomical pulleys of the fingers and thumb
5
Extrinsic Finger Flexors
FDS-more torque at MCP jt than FDP
FDP-more active than FDS/flexes all 3 jts of fingers/more superficial at PIP than FDS
Intrinsic Finger
Musculature
Dorsal and Palmar Interossei
DABs and PADs
Lumbricals
FPB-palmar interossei
AbDM-dorsal interossei
Intrinsic Finger
Musculature
ED, EI, EDM
Extensor Mechanism formed by:
EDC, EIP and
EDM tendons
Extensor hood
Central Tendon
Lateral Bands
Terminal Tendon
Triangular lig
Oblique retinacular lig
Sagittal bands
Extensor Mechanism Influence on MCP
and IP Joint Function
ED contracts=tension created on sagittal bands
ProPhalanx rolls and glides dorsally on MC
Interossei, dorsal, volar, lumbricals help IP extension
Functional Position of the Hand
Wrist in slight extension 20deg
Slight ulnar deviation 10deg
Fingers moderate flexion at MCP 45deg and PIP jts 30deg
Slight flexion at DIP jts
2 categories of Prehension
Power Grip: involves full hand
Precision Handling: utilizes finger and thumb
Power grip - Cylindrical
-Finger flexors primary
-FDP main contributor
Power grip - Spherical
-Similar to cylindrical
-Fingers in more ABd.
-Interossei more active in this grip
Power grip - Hook grip
-FDS, FDP,
-No thumb involvement
-Often allows greater endurance
Power grip - Lateral prehension
-static hold of an object btw 2 fingers
Precision Handling - Tip to Tip
-Similarities in muscle activity to pad to pad
-Requires more joint flexion for tip to tip contact
Precision Handling - Pad to Pad
-Opposition of pad of thumb to pad of finger
-80% prehension handling in life
-FDP, APB, FPL among others active
Precision Handling - Pad to Side
-Key/lateral grip
-ADP, FPD, OP
