CHAPTER 7 Wrist and Hand

Introduction The wrist and hand are composed of multiple joints. The wrist fine-tunes hand position. The hand contains palm and fingers.

Fingers are referred to as digits, of which there are five per hand. Introduction Fingers are referred to as digits, of which there are five per hand. The hand is a complex multipurpose organ. Prehension Sense organ Expression and nonverbal communication

Bones—Wrist Distal ulna Not in direct contact with carpal bones (triangular fibrocartilage complex; TFCC) Three parts: Ulnar styloid process Fovea Pole

Bones—Wrist Distal radius Primary forearm bone of wrist Features Dorsal surface tubercle—redirect pull of extensor pollicis longus (EPL) Radial styloid process Ulnar notch

Bones—Wrist Carpal bones Categorized into proximal and distal rows Capitate—occupies central position Scaphoid—most commonly fractured carpal Lunate—most frequently dislocated carpal Pisiform—serves as attachment for flexor carpi ulnaris (FCU) Hamate—unique hook feature

Bones—Hand Metacarpals Base articulates with carpal bones and adjacent metacarpals. The shaft is slightly curved with a palmar concavity. The head articulates with the base of proximal phalanx.

Bones—Hand Phalanges Thumb—two: proximal and distal Digits 2–5—three: proximal, middle, and distal Base—biconcave Distal heads—bicondylar

Joints—Wrist Radiocarpal joint Biconcave distal radius and convex proximal row TFCC Attaches to distal radius and ulna Apex attached to triquetrum Part of flexion/extension; radial and ulnar deviation occur at this joint Recommend inserting Figure 7-5

Joints—Wrist Midcarpal joint Formed by proximal and distal rows Additional amounts of flexion/extension; radial/ulnar deviation Recommend inserting 7-4

Carpometacarpal joints (2–5) Joints—Hand Carpometacarpal joints (2–5) Metacarpal bases 2–5 articulate with one another. There is minimal motion of the second and third. Fourth and fifth have significant motion. Third acts as a stable pillar about which hand rotates.

Carpometacarpal joints—first Joints—Hand Carpometacarpal joints—first Saddle Thick but loose capsule Motions include: Flexion/extension Abduction/adduction Opposition/reposition Recommend inserting Figures 7-8A, B, C

Metacarpophalangeal joints Joints—Fingers Metacarpophalangeal joints Condyloid with two degrees of freedom Flexion/extension; abduction/adduction Convex heads of metacarpals—3/4 covered with articular cartilage Concave bases of phalanges—volar plates

Interphalangeal joints Joints—Fingers Interphalangeal joints Digits 2–5—proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints Thumb—one interphalangeal joint Hinges—one degree of freedom Flexion/extension

Joints—Soft Tissue Supporting Structures Ligaments of the wrist Complex ligaments—cover all aspects of wrist Extrinsic—radius, ulna, or metacarpals to carpals Flexor and extensor retinacula—Carpal Tunnel Syndrome on flexor side Intrinsic—between carpal bones only V-shaped ligament No ligaments between capitate and lunate

Joints—Soft Tissue Supporting Structures Ligaments of the hand and fingers Medial and lateral collaterals Taut in flexion—assist with ability to grip Loose in extension—allow abduction/adduction Deep transverse carpal ligament Attaches to heads of metacarpals 2–5

Joints—Soft Tissue Supporting Structures Ligaments of the hand and fingers Thumb Two sesamoids attached to volar plate Several ligaments attached Sesamoid mechanism facilitates pinch precision

Muscles Wrist extensors Common origin—lateral epicondyle With elbow >15°— anterior to elbow axis Primary wrist extensors: Extensor carpi radialis brevis (ECRB)—extensor carpi radialis longus (ECRL)—extensor carpi ulnaris (ECU) Extensor digitorum Wrist extension when fingers extended

Muscles Wrist flexors Common origin—medial epicondyle With elbow flexed, may aid in elbow flexion Primary muscles Flexor carpi radialis (FCR)—FCU—flexor digitorum superficialis (FDS)—flexor digitorum profundus (FDP)—Palmaris Longus (PL)—FPL—APL

Radial/ulnar deviation Muscles Radial/ulnar deviation Deviation occurs in frontal plane about an A-P axis. Muscles (either flexors or extensors) that are further from axis will assist with respective deviation. Wrist extensors and flexors work synergistically.

Muscles—Extensor Mechanism Tendinous system Three bands—central (one); lateral (two) Retinacular system Extensor hood Flexor pulleys

Motions—Wrist Osteokinematics Radial deviation—bony end feel Midcarpal and radiocarpal each responsible for 1/2 A-P axis through capitate Ulnar deviation—firm end feel Midcarpal responsible for 1/3 Radiocarpal responsible for 2/3

Motions—Wrist Osteokinematics Flexion Extension 50° at radiocarpal joint; 35° at midcarpal Extension 50° at midcarpal joint; 35° at radiocarpal Axis for flexion/extension also passes through capitate

Motions—Wrist Arthrokinematics Convex proximal row on concave ulna Roll and glide in opposite directions Wrist extension—posterior roll; anterior glide Arthrokinematics similar at midcarpal joint Close-packed position—full wrist extension

Osteokinematics—metacarpophalangeal (MCP) joints (2–5) Motions—Fingers Osteokinematics—metacarpophalangeal (MCP) joints (2–5) ~90° of flexion; extension is variable depending on individual and whether motion is active or passive. End feels are typically firm for both flexion and extension. Close-packed position = full flexion.

Osteokinematics—MCP joints (digits 2–5) Motions—Fingers Osteokinematics—MCP joints (digits 2–5) ~20° of abduction/adduction can occur when MCP joints are extended. Little or no abduction/adduction with MCP joints in flexion due to Closed Packed Position.

Osteokinematics—MCP joints (thumb) Motions—Fingers Osteokinematics—MCP joints (thumb) Hinge joint Flexion = 45–60° Extension = 0–20° Small amount of side-to-side motion with thumb in slight flexion Allows for fine-tuning grasp

Motions—Fingers Osteokinematics—proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints Hinge joints Flexion = 120° Extension = 0° (unless hyperlax) Resting position (for both MCP and IP joints) 20° of flexion Close-packed position Full extension (thumb); full flexion (2–5)

Arthrokinematics—MCP and IP joints Motions—Fingers Arthrokinematics—MCP and IP joints Roll and glide in the same direction True for both flexion/extension and abduction/adduction motions In loose-packed position (20°)—large joint play motions are possible

Functional Movements of Wrist and Hand Types of grasp Power grip Incorporates entire hand Is used for gross grasping activities Is involved in holding an object between partially flexed fingers and palm while thumb provides counterpressure Different types of power grips—see Table 7–4

Functional Movements of Wrist and Hand Types of grasp Precision grip Is used for accuracy and refinement; object manipulation Thumb abducted—ready to oppose Different types of precision grips—see Table 7–5

Functional Movements of Wrist and Hand Strength of grip Males grip strength (100#) on average 2× greater than females of similar age. Studies vary, but overall, ~6% stronger grip on dominant side.

Functional Movements of Wrist and Hand Grasping Finger flexion occurs with the wrist stabilized in extension. Grip is significantly weakened if wrist flexion occurs. Influenced by passive insufficiency of wrist extensors and active insufficiency of wrist flexors Optimal wrist position during grasp = 20–35° extension with slight ulnar deviation.

Functional Movements of Wrist and Hand Abduction/adduction digits 2–5 Away from midline = abduction; toward = adduction Midline—through middle finger Occurs at MCP joints when extended Abduction coupled with extension; adduction with flexion

Balanced Forces Thumb Mobility Carpometacarpal (CMC) joint = a saddle joint that enhances mobility Motions: flexion/extension; abduction/adduction; opposition and reposition

Summary Wrist and hand as a complex organ with many responsibilities Balance of extrinsic and intrinsic muscle activity Functional position of wrist (20–35° of extension); ability of injury to affect optimal wrist position