Hand and Fingers Region

Hand and Fingers Region Neumann Chapter 8

SURFACE ANATOMY (PALMAR) [F IG 8-3]

 Wrist - prox & distal wrist creases  Palm - thenar crease; prox & distal palmar creases  Digits - prox, middle, & distal digital creases

OSTEOLOGY

 Metacarpals - 5; named started in the thumb side Phalanges – 5 Proximal, 5 Distal, 4 Middle

ARTHROLOGY, OSTEOKINEMATICS, ARTHROKINEMATICS [FIG 8-9 THRU 8-17]

1ST Carpometacarpal joint - the Carpometacarpal (CMC) joint of the thumb is biaxial, saddle joint.  Osteokinematics  Flexion & Extension: occurs nearly parallel to the palm, essentially in the FRONTAL PLANE.  Abduction & Adduction: occurs nearly perpendicular to the palm, essentially in the SAGITTAL PLANE.  Opposition: Flexion & Abduction contribute the most to opposition of the thumb.  Arthrokinematics  Abduction and Adduction follow the Rule of Convex Moving surfaces  Flexion and Extension follow the Rule of Concave Moving surfaces

CMC joints 2 – 5 are plane, nonaxial joints.  Osteokinematics -

[See Figs 8-9, 8-20 thru 8-30 for MCP & IP jts] Metacarpophalangeal joints – 5 biaxial condyloid joints  Metacarpal head is large articular surface, whereas articular surface of phalanx is much smaller.  Osteokinematics:  flexion, extension, abduction, & adduction.  MCP joint of thumb has only about 50% of flexion allowed at MCP joints of fingers and is extremely limited in ab/adduction.  Arthrokinematics:  Head of metacarpal bone is convex, proximal phalanx is concave; "like little knees"

Interphalangeal joints - 1 IP joint, 4 PIP joints, 4 DIP joints  Uniaxial hinge joints  Osteokinematics: flexion & extension only  Arthrokinematics: same at MCP jts o some argument regarding application of convex/concave rule so just disregard the rule and do A-P glides for joint mobilization (addresses both flexion and extension)

JOINT REINFORCEMENT  Volar (palmar) plates are present at this all MCPs and IPs o Volar plate is plate of fibrocartilage which is attached to distal bone and thins out proximally to attach to joint capsule and proximal head. o Inner surface of volar plate provides additional articular surface. o Plate restricts hyperextension, prevents pinching of long flexor tendons during flexion.  Collateral ligaments o Reinforce medial and lateral sides of joints o Limits abduction and adduction of MCPs & Restricts it at IPs. Joint/Ligament Trauma -

MUSCULATURE  Muscles that originate outside the hand and act on it = Extrinsic muscles  Muscles that originate inside the hand and act on it = Intrinsic muscles

Extrinsic Hand Musculature

FLEXORS  Flexor pollicis longus – flexes IP & MCP joint  Flexor digitorum superficialis (FDS) – flexes MCP & PIP jts.  Flexor digitorum profundus (FDP) – flexes MCP, PIP, & DIP jts. o Related to Grip: Wrist flexion reduces efficiency of FDS & FDP to ¼ what it is with wrist slightly extended. WHY?

Extensors/ ABD:  Extensor digitorum – extends MCP, PIP, & DIP jts. 2 – 5  Extensor digiti minimi – extends MCP, PIP, & DIP jt.  Extensor indicis – extends MCP, PIP, & DIP jt.  Extensor pollicis longus – extends IP and MCP  Extensor pollicis brevis – extends MCP  Abductor pollicis longus – abducts 1st CMC joint

Intrinsic Hand Musculature (Fig 8-24, 8-49)

MUSCLE-TENDON CONTENTS OF THE PALM ,  Tendons and tendon sheaths of the Flexor digitorum superficialis & Flexor digitorum profundus  4 Lumbrical muscles  Arise from tendons of FDP inserts into extensor hood on radial side  Extends IP joints and flexes MCP joints – Referred to as table-topping.  Adductor pollicis (web space) – adducts 1st CMC joint

THENAR EMINENCE  Tendon of flexor pollicis longus  Abductor pollicis brevis – abducts MCP joint  Flexor pollicis brevis – flexes MCP joint  Opponens pollicis – opposition of 1st metacarpal

HYPOTHENAR EMINENCE  Abductor digiti minimi – abducts MCP joint  Flexor digiti minimi brevis – flexes MCP joint  Opponens digiti minimi – opposes 5th metacarpal

INTEROSSEOUS REGION  Interosseous Muscles  3 Palmar Interossei - adduct digits 2, 4, & 5 toward the middle digit (3) ; Remember " 3 PAD"  Dorsal Interossei: abduct digits 2, 3, & 4 from the mid line of the hand; Remember " 4 DAB"

INNERVATION TO INTRINSIC MUSCLES OF HAND Median nerve (L.O.A.F.)  Lumbricales (1st and 2nd) , Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis Everything else is ulnar nerve

INDEPENENT STUDY: 1. Intrinsic-plus and Extrinsic-plus positions of the hand (Neumann pg 276, Fig 8-50)

2. Ulnar nerve lesion and resulting clawing of digits 4-5 (Neumann pg 278, Fig 8-52)

3. Anatomical Snuffbox (boundaries and contents)

4. Specialized Flexor and Extensor Tendon Anatomy of the Fingers (Gross notes, Neumann, etc..) a. Appreciate how/why there is only 1 primary extensor of the fingers but are 2 flexors (compare/contrast)

Tendon injuries and resulting deformities: (Fig 8-57 & 8-60)  Boutonniere deformity: torn/avulsed central tendon (band) from middle phalanx

 Mallet finger deformity: torn/avulsed distal extensor tendon (lateral bands) from distal phalanx

 Swan neck deformity: 1. slack or subluxed (posteriorly) lateral bands OR 2. jt degeneration (RA) OR 3. volar plate detachment at PIP (hyper-extens deformity) OR 4. chronic mallet finger can progress to a swan-neck.

Descriptions of different ways of grasping objects (Fig 8-55) Prehension – the grasping of an object between any two surfaces of the hand; the thumb may or may not participate. Prehension can be divided into 2 categories:  Power Grip  3 Types of Power Grip  Cylindrical Grip  Spherical grip – with more abduction of fingers  Hook grip – never includes the thumb but may include the palm. Can be sustained for long periods of time.  NOTE: Passive hand closure with wrist extension is known as Tenodesis. Tenodesis can also be used for cylindrical grasp. Release of tenodesis grip is accomplished by relaxing wrist extensors and allowing gravity to flex the wrist. Explain how this is possible?

Precision Handling – the placement of an object between the fingers or finger and thumb. The palm is NOT involved.  3 types of precision handling o Pad-to-pad: opposition of the pad of the thumb to the pad of the finger o Tip-to-tip: opposition of the tip of the thumb with the tip of the finger. Most precise form of grasp o Pad-to-side: opposition of pad to the thumb with the side of the finger – usually the index finger.

REVIEW QUESTIONS  The flexor digitorum superficialis attaches distally on which phalangeal bone? in which digits? Where does the flexor digitorum profundus attach distally?

 Are the flexor carpi radialis tendon and the ulnar nerve in the carpal tunnel?