Wrist & Hand Biomechanics PDF

Orthopedic Treatment FT400 PT600 Wrist & Hand Module Section 2 - Biomechanics Wrist Complex 3 Joints form the wrist complex Distal Radio-Ulnar Radio-Carpal* MidCarpal Radio-carpal includes articulation between the TFCC disc and the carpals (ulnomeniscotriquetral joint) I...

Orthopedic Treatment FT400 PT600 Wrist & Hand Module Section 2 - Biomechanics Wrist Complex 3 Joints form the wrist complex Distal Radio-Ulnar Radio-Carpal* MidCarpal Radio-carpal includes articulation between the TFCC disc and the carpals (ulnomeniscotriquetral joint) In other words, we count them as one functional unit Orthopedic Treatment 400FT/600PT - VCMT Flexion & Extension Mechanics Primary axis for flex-ext is through the capitate Flexion primarily occurs at the midcarpal joint Extension primarily occurs at the radiocarpal joint Orthopedic Treatment 400FT/600PT - VCMT Closed Pack Position of Wrist Supinatory Twist There is slight supination in the wrist with extension. This “screw home” movement is needed for the wrist to achieve full close pack position for intrinsic stability. Closed pack (max stability) helps with performing functional activities involving force transmission from the hand to the forearm – walking on all fours, pushing a heavy object The carpal bone responsible for this twist is scaphoid Orthopedic Treatment 400FT/600PT - VCMT Closed Pack Position of Wrist Moving from Flexion to Extension In flexion, the distal and proximal rows are in loose packed position. Moving from flexion to extension, the carpals must glide anteriorly As the wrist reaches neutral, the distal row stops moving To allow continued movement of the proximal row, the scaphoid does a small supinatory twist, locking the scaphoid and distal row into CPP Once the distal row and scaphoid are close-packed, movement continues at the prox row. Orthopedic Treatment 400FT/600PT - VCMT Closed Pack Position of Wrist Clinically, Movement between the lunate and the scaphoid must occur to allow the final stage of Extension The scaphoid creates an asymmetry, resulting in a supinatory twist – this causes a twist in the capsules and ligaments creating the close pack position on full extension So if somebody is struggling with full wrist extension, scaphoid joint play is probably indicated For athletes that spend time on their hands, scaphoid joint play is probably indicated Orthopedic Treatment 400FT/600PT - VCMT Closed Pack Position & Injury As with most joints, close-pack position (extension) is most susceptible to injury. Scaphoid = most commonly fractured carpal Lunate = most commonly subluxed or dislocated (palmarly) Orthopedic Treatment 400FT/600PT - VCMT Radial & Ulnar Deviation Mechanics Axis of movement is through the capitate UD has greater range - the triquetrum clears the ulnar styloid process more easily than the scaphoid tubercle clears the radial styloid process during RD Carpal movement Both RD and UD involve movement at the radiocarpal and midcarpal joints - there is a slight rotary motion involved Orthopedic Treatment 400FT/600PT - VCMT Radial & Ulnar Deviation Mechanics Carpal movement during deviations 1. During Radial Deviation Proximal row (in reference to the RC joint) moves into Pronation Ulnar glide Flexion Distal row (in reference to the MC joint) moves into Supination Ulnar glide Extension 2. During Ulnar Deviation *Ulnar deviation yields the opposite movements* Orthopedic Treatment 400FT/600PT - VCMT Orthopedic Treatment 400FT/600PT - VCMT Functional Arches All the arches work for a common purpose of improving the functional ability of the hand Structurally, the arches are 1 longitudinal (per finger) 1 transverse carpal 1 transverse metacarpal All of the arches are concave palmarly. Orthopedic Treatment 400FT/600PT - VCMT Longitudinal Arch(es) The longitudinal arch consists of each finger and its corresponding carpal bone. These arches are centered around their MCP joints. The long finger and the capitate form the focal point. Orthopedic Treatment 400FT/600PT - VCMT Transverse Arches The Transverse Carpal (Proximal transverse) arch formed by the distal row Each of the carpal bones move independently of each other. Proximal row is more mobile than distal The distal row centers around the capitate and provides less movement (due to its articulations with the metacarpals) The Transverse Metacarpal (Distal transverse) arch Formed by the heads of the metacarpals. The third metacarpal, the capitate, and lunate are the center point. It is relatively flat at rest; the curvature considerably increases with strong clenching of the fist or thumb to pinky opposition Orthopedic Treatment 400FT/600PT - VCMT Cascade Sign Only the index ray flexes in the sagittal plane while the other fingers flex toward the scaphoid Orthopedic Treatment 400FT/600PT - VCMT Cupping & Flattening Cupping of the hand involves finger flexion Cupping = improves hand mobility for functional use Flattening of the hand involves finger extension Flattening = used to release objects Orthopedic Treatment 400FT/600PT - VCMT Length-Tension Relationships The wrist provides a stable base for the hand, and its position controls the length of the extrinsic muscles to the digits Muscles of the wrist movement serve 2 important functions: 1.) Provide fine adjustment of the hand into its functioning position 2.) And once this position has been achieved, they stabilize the wrist to provide a stable base for the hand *Key: movements of the wrist are usually in reverse of the movements of the fingers and reinforce the action of the extrinsic muscles of the fingers Orthopedic Treatment 400FT/600PT - VCMT Length-Tension Relationships Finger flexion Finger flexion = wrist extensors activate to stabilize wrist, preventing the long finger flexors from simultaneously flexing the wrist Finger extension Finger extension = wrist flexors activate so that the long finger extensors can function more effectively. Orthopedic Treatment 400FT/600PT - VCMT Length-Tension Relationships Impact on hand function - dexterity Changes in wrist position > extrinsic muscle length changes > force exertion changes Appropriate length-tension relationship is therefore crucial for optimal function Extreme example: try to write with full wrist flexion Impact on hand function - grip strength As grip strength increases, wrist extensors slacken allowing a favorable shortening of the flexors to achieve a strong contraction Greatest interphalangeal flexion force= ulnar deviation and neutral flexion-extension Orthopedic Treatment 400FT/600PT - VCMT Dorsal Digital Expansion aka Extensor Mechanism A broad, flat aponeurotic band of tissue composed of extrinsic extensor tendon and sheath posteriorly, and by the tendons of the interosseous and lumbrical muscles anteriorly Originates at posterior, medial, and lateral sides of prox phalanges, D1-5 Inserts at posterior sides of distal phalanges, D1-5 Extrinsic Tendon - The extrinsic tendons (ED and EPL) exert force at the MCP Intrinsic Tendon - The intrinsic tendons (Lumbricals and Interossei) are extensors for the IP joints, D2-5 only Orthopedic Treatment 400FT/600PT - VCMT Dorsal Digital Expansion aka Extensor Mechanism Orthopedic Treatment 400FT/600PT - VCMT  Power Precision Prehension Grip The musculoskeletal function of the hand lies in its ability to grip objects There are 4 types of prehension: pinch, encircle, push or adhere Usually, an animal will present with only one type of prehension Humans have all types because of the Prehension is categorized into 2 groups: opposable thumb power and precision Orthopedic Treatment 400FT/600PT - VCMT Prehension - Power Grip A forceful act with flexion at all fingers (D1-5) The thumb is the stabilizer to the object being held between the fingers and the palm – clamping action of the fingers pushing the object against the palm and countered by the thumb The 2 ulnar fingers flex across toward the thenar eminence The thenar and hypothenar act as buttresses as the fingers flex around the object to be grasped With all power grips the hand is kept stable and power movements are produced by either radial or ulnar deviation of the wrist (i.e. hammering), supination and pronation of the wrist, and elbow extension Orthopedic Treatment 400FT/600PT - VCMT Prehension - Power Grip There are varieties of power grips Cylindrical Spherical Hook Fist A power grip is a result of a sequence of opening the hand, positioning the fingers, approaching the fingers to the object and maintaining a static phase (ISOMETRIC contraction) which constitutes a grip Orthopedic Treatment 400FT/600PT - VCMT Prehension - Precision Grip Lacks a static phase Is dynamic/isotonic The object is picked up by the fingers and thumb but is not in contact with the palm Sensory surfaces of the digits are used for maximum sensory input to influence delicate adjustments Varieties of precision grip Palmar pinch Lateral pinch (opposition) Tip prehension (the finest and most precise grip easily upset by any disease of the hand) Orthopedic Treatment 400FT/600PT - VCMT Prehension Comparison Power Precision All 5 digits Digits 1-3 only Includes Ulnar side of hand Does not include Ulnar side of hand Object contacts palm Object in digits Isometric/Static Isotonic/dynamic Orthopedic Treatment 400FT/600PT - VCMT Grip Innervation Precision grip activity is mainly performed by the median side of the hand and is used when accuracy, precision and control are required. Power grips rely on the interaction of the median and ulnar side of the hand. As implied, this grip is used whenever strength or force is needed. Orthopedic Treatment 400FT/600PT - VCMT Wrist & Hand Observation History Location* MOI*- FOOSH or other trauma, degenerative change, RSI Nature Onset* Pain/10 Quality* Referral/Radiating*- nerve involvement or TrPs Systemic- diabetes, arthritis, pregnancy Timing*: Certain time of day? Certain activity? Underlying- age, occupation, hobbies, lifestyle factors, etc Orthopedic Treatment 400FT/600PT - VCMT Swan Neck Deformity Deformity in the fingers MCP Flexion PIP Extension DIP Flexion Cause contracture of the intrinsic muscles tearing of the Volar plate Usually seen with RA or post trauma Orthopedic Treatment 400FT/600PT - VCMT Boutonniere Deformity Deformity in the fingers MCP Extension PIP Flexion DIP Extension Cause Rupture central slip of DDE (aka dorsal hood aka extensor mechanism) Usually seen with RA or post trauma Orthopedic Treatment 400FT/600PT - VCMT Dupuytren’s Contracture Contracture of the palmar fascia As a result there is a fixed flexion deformity of the MCP and PIP joints Usually seen in digits 4 & 5 with skin also being adhered to the fascia Note: this is connective tissue, it is not neuromuscular Orthopedic Treatment 400FT/600PT - VCMT More Hand Deformities Heberden’s (DIP) and Bouchard’s (PIP) nodes – arthritic changes on the dorsal surfaces Orthopedic Treatment 400FT/600PT - VCMT More Hand Deformities Ulnar drift (RAU) - due to the changes in the MCP and resulting pull on the long tendons. Seen with RA Radial drift (OAR) seen with OA Orthopedic Treatment 400FT/600PT - VCMT More Hand Deformities “Z” deformity of the thumb CMC Flex MCP Hyperext IP Flex Hereditary association or RA Mallet Finger Distal phalanx rests in a flexed position Results from a rupture or avulsion of the extensor tendon (at distal insertion) Orthopedic Treatment 400FT/600PT - VCMT Peripheral nerve lesions Radial Nerve Ulnar Nerve Median Nerve Functional ROM The thumb is the most important digit where as the ring finger has little significance or influence A way to test wrist and hand functionality is with grips: power and precision Orthopedic Treatment 400FT/600PT - VCMT AROM All movement should be observed with the most painful movements performed last FLEXION- most of the movement occurs in the midcarpal joint and less occurs at the radiocarpal joint (30˚) EXTENSION – most of the movement occurs in the radiocarpal joint and less occurs at the midcarpal joint RADIAL DEVIATION – primarily occurs at the midcarpal joint ULNAR DEVIATION – primarily occurs at the radiocarpal joint Orthopedic Treatment 400FT/600PT - VCMT PROM & End-feel End-feels Flexion/Extension RC = firm (tissue stretch) Radial/Ulnar Deviation = hard (bone to bone or UMT) MCP Flex/Ext = firm/hard PIP Flx/Ext = firm/hard DIP Flx/Ext = firm/hard Orthopedic Treatment 400FT/600PT - VCMT RROM Note: If pt complains that isotonic contraction is painful and symptomatic. These movements should also be tested if needed. Orthopedic Treatment 400FT/600PT - VCMT Neurological Nerve Root Dermatome, Myotome (C6-T1) Reflex testing: 1. C5 – Biceps 2. C6 – Brachioradialis 3. C7 – Triceps Orthopedic Treatment 400FT/600PT - VCMT Referred Pain Common! It is important to remember that pain may be referred to the wrist and hand from the cervical or upper thoracic spine, shoulder and elbow. Rarely do the wrist and hand refer pain up the limb. Orthopedic Treatment 400FT/600PT - VCMT Special Tests Refer to the riveting PDF on Canvas Orthopedic Treatment 400FT/600PT - VCMT