Hand and Fingers Region Neumann Chapter 8 SURFACE ANATOMY Wrist - Palm - Digits - OSTEOLOGY Metacarpals - Phalanges – ARTHROLOGY 1ST Carpometacarpal joint - the Carpometacarpal (CMC) joint of the thumb is _______________________. Osteokinematics _______________________: occurs nearly parallel to the palm, essentially in the FRONTAL PLANE. _______________________: 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 __________________ Moving surfaces Flexion and Extension follow the Rule of __________________ Moving surfaces CMC joints 2 – 5 are __________________ joints. Osteokinematics - Metacarpophalangeal joints – _______________________________. Metacarpal head is large articular surface, whereas articular surface of phalanx is much smaller. Osteokinematics: flexion, extension, abduction, & adduction. Arthrokinematics: Head of metacarpal bone is convex, proximal phalanx is concave; "like little knees" MCP joint of thumb has only about 50% of flexion allowed at MCP joints of fingers and is extremely limited in ab/adduction. Interphalangeal joints - _________________________________________. Uniaxial hinge joints Osteokinematics: flexion & extension only Arthrokinematics: 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 _______________________is present at this all MCPs and IPs o Volar plate is actually 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 _______________________ AND prevents pinching of long flexor tendons during flexion. Collateral ligaments o Reinforce medial and lateral sides of joints o Limits _____________________________________of MCPs & Prevents/Restricts it at IPs. Joint/Ligament Trauma - MUSCULATURE Muscles that originate outside the hand and act on it = _______________________muscles Muscles that originate inside the hand and act on it = _______________________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 Both muscles are dependent on wrist position for optimal function – maintenance of optimal length-tension. For optimal finger flexion, the wrist must be slightly extended. o Wrist flexion reduces efficiency of these muscles to ¼ what it is with wrist extension. WHY? Question: Why is DIP flexion almost always accompanied by PIP flexion? However, PIP flexion can occur without DIP flexion. 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 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 _____________________ nerve Lumbricales (1st and 2nd) Opponens pollicis Abductor pollicis brevis Flexor pollicis brevis Everything else is _________________ nerve SPECIALIZED TENDON STRUCTURES OF THE FINGERS EXTENSOR EXPANSION Formed by the tendons of the _______________________, the _______________________, & the _______________________ muscles. The Ext digitorum tendon flattens into a hood just distal to the MCP. Tendons of the Interosseous muscles blend with the extensor hood at this point. It immediately splits into 3 bands over the proximal phalanx. The central band inserts onto the middle phalanx. The 2 lateral bands cross the PIP and come together distally to insert on the distal phalanx. Because of this arrangement, only one extensor muscle of the fingers (Extens. Digitorum) is needed. Compare this to the flexor tendons. Lumbrical tendon blends with the lateral band (radial side). Tendon injuries and deformities: FLEXOR TENDONS The tendons of the Flexor Digitorum _______________________split into 2 parts & attach to each side of the middle phalange (to perform PIP flexion). The tendons of the Flexor Digitorum _______________________pass thru this split and attach to the distal phalange (to perform DIP flexion) ANATOMICAL SNUFF BOX Boundaries are tendons _______________________- abductor pollicis longus and extensor pollicis brevis; APL is most anterior _______________________- extensor pollicis longus _______________________– branches of radial artery and radial nerve, scaphoid, trapezium, 1st CMC joint. GET A GRIP 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? Suppose a person has a spinal cord injury that interrupts innervation that orginates below the level of the sixth spinal segment (below C6 nerve root). A person with this injury loses all innervation of the FDS and FDP. However, they retain some innervation to the wrist extensors. They can use the wrist extensors to elongate and develop passive force in the long finger flexors. However, the person cannot develop functionally useful levels of passive force in the flexor muscles IF they become too flexible. Therapists must teach the person to use the extremity without stretching the FDP and FDS. Decide how to instruct someone to bear weight on the upper extremities without elongating the finger flexors.
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