Anatomy and biomechanics of wrist joint Understanding motions occurring at wrist joint and different possible mechanisms of injury

1. Wrist Joint
Dr. Shweta Kotwani; Pediatric Physical Therapist
BPTh (MUHS); MPT (Neuro,MUHS); LASHS-U.K.
Fellowship Dip.(Peds.Rehab.; Clinical Neuro.Sc.)

2. Objectives
• To identify the structure of the wrist.
• To describe joint motions occurring at the wrist, including
physiological and accessory movements, muscle actions.
• To understand the stability mechanism of the wrist and the
possible mechanisms of injury.

3. • The Wrist
– Distal radius and ulna, eight carpal bones, and the bases of
five metacarpals
– The carpal bones lie in two transverse rows
• The proximal row contains (lateral to medial) the scaphoid,
lunate, triquetrum, and pisiform
• The distal row holds the trapezium, trapezoid, capitate, and
hamate

5. Normal Range of Motion (ROM)
Flexion 0-65°-85°
Extension 0-60°-85°
Ulnar Deviation 0-15°-21°
Radial Deviation 0-20°-45°
Biaxial ellipsoid joint with -
1. Flexion-Extension around frontal axis & sagittal plane
2. Radial-Ulnar deviation around sagittal axis & frontal plane

6. • Wrist consists of two compound joints
1. Radiocarpal joint
2. Midcarpal joints

7. Radiocarpal Joint
• It is formed by radius and radioulnar disc as part of TFCC
proximally and by scaphoid, lunate and triquetrum distally
• It is a condyloid (ellipsoid) type of synovial joint.
• the carpal aspect presents two convexities transverse
convexity and antero-posterior convexity.
Ellipsoid Joint

9. Triangular fibrocartilage complex (TFCC)
The TFCC is essentially comprised of the
-triangular fibrocartilage disc
-radioulnar ligament
-ulnocarpal ligament
The primary function of the TFCC is to improve joint
congruency and to cushion against compressive
forces
The TFCC transmits about 20% of the axial load from the hand
to the forearm

12. Articulating surfaces
• Ulnar negative variance-
Short ulna in relation to radius at distal end
• Ulnar positive variance-
Distal ulna is long in relation to distal radius
Ulnar variance and thickness of triangular
fibrocartilage complex have an inverse
relationship

14. • Mid Carpal Joints
Forms compound articulation between proximal and distal rows
of carpal bones with exception of pisiform bone.
• Proximal row- scaphoid, lunate, triquetrum
• Distal row- trapezium, trapezoid, capitate, hamate
• Plane joints that allow gliding motion, but assist with
wrist motions.

16. Ligaments of the Wrist Complex
• The joint capsule and ligaments contribute to the stability of the
wrist.
• Volar Carpal Ligaments
1. Volar (Palmar) Radiocarpal Ligament
2. Ulnocarpal Ligament
• Dorsal Carpal Ligaments
1. Dorsal Radiocarpal Ligament
2. Dorsal Intercarpal Ligament
• Ulnar Collateral Ligament
• Radial Collateral Ligament
• Intrinsic Ligaments
1. Scapholunate interosseous ligament
2. Lunotriquetral interosseous ligament

19. Kinematics
• Flexion/Extension of the Wrist

20. Radial/Ulnar Deviation of the Wrist

21. • Flexion
• palmaris longus,
• flexor carpi ulnaris,
• flexor carpi radialis,
• flexor digitorum superficialis.
• Extension
• extensor carpi radialis longus and brevis,
• extensor carpi ulnaris,
• extensor digitorum.
• Ulnar deviation
• extensor carpi ulnaris
• flexor carpi ulnaris
• Radial deviation
• abductor pollicis longus,
• flexor carpi radialis,
• extensor carpi radialis longus and brevis.
Muscles

22. Fracture of the Scaphoid
• In the event of a blow to the wrist (e.g falling on an
outstretched hand), the scaphoid takes most of the
force.
• The scaphoid has a unique blood supply, which
runs distal to proximal. A fracture of the scaphoid can
disrupt the blood supply to the proximal portion – this
is an emergency. Failure to revascularise the scaphoid
can lead to avascular necrosis, and future arthritis for
the patient.
• The main clinical sign of a scaphoid fracture is
tenderness in the anatomical snuffbox.
Clinical Implication

23. Fracture of scaphoid

24. Anterior Dislocation of the Lunate
• This can occur by falling on a dorsiflexed wrist.
The lunate is forced anteriorly, and compresses
the carpal tunnel, causing the symptoms of carpal
tunnel syndrome.
• This manifests clinically as paraesthesia in the
sensory distribution of the median nerve and
weakness of thenar muscles. The lunate can also
undergo avascular necrosis, so immediate
clinical attention to the fracture is needed.

25. Kienbock’s disease
• Avascular necrosis of lunate
• Associated with ulnar negative variance
• Stiffness of the wrist and tenderness directly
over lunate

26. MRI of a wrist with Kienbocks disease showing loss of blood supply to the
lunate in a patient with a short ulna

27. Wrist instability
Intercalated segmental instability
• Dorsal intercalated segmental instability (DISI)
• Volar intercalated segmental instability (VISI)

28. DISI- lunate assumes an extended
posture
VISI-
lunate+triquetrum= extension
Scaphoid= flexion

29. TFCC TEAR
• Fall on dorsiflexed and ulnar deviated wrist
• Gymnasts are at risk as they put a lot of
pressure on their wrist
• Pain at the base of small finger side of the
wrist
• Loss of grip strength
• Positive ulnar variance predisposes to injury
• Rx- splint/cast, ultrasound

31. Scapholunate ligament injury
• FOOSH injury
• Pain & swelling on dorsum of wrist
• Separation between scaphoid and lunate is
seen on radiograph
• Wears the joint and in next 5-10 years a
pattern of arthritis called scapholunate
advanced collapse (SLAC) occurs
• Watson’s test

32. SLAC Wrist
Separation
between scaphoid
and lunate
causing the
capitate to sublux
dorsally

33. References
• Joint structure and function: A comprehensive
analysis; fifth edition; cynthia norkin, pamela
levangie
• Clinical Relevance: Injuries to the Wrist Joint By
Gilo1969 (Own work) [CC-BY-SA-3.0], via
Wikimedia Commons
• Sussex hand surgery: condition included
scapholunate ligament injury

34. Thank you