Hand & Wrist Conditions: Nerves, Injuries & Deformities

• The flexor retinaculum attaches to the Scaphoid tubercle, Trapezium tubercle, Hook of hamate, and Pisiform.
• Lateral tendons of the Anatomical Snuffbox are the abductor pollicis longus and extensor pollicis brevis.
• The medial tendon of the Anatomical Snuffbox is the extensor pollicis longus.
• The scaphoid is the floor of the Anatomical Snuffbox and the radial artery is contained within.

Tunnel of Guyon

• Located between the pisiform and hook of hamate, covered by the pisohamate ligament.
• The ulnar nerve is contained within.

Distal Radioulnar Joint

• Synovial, pivot joint type.
• The articulating surfaces are the ulnar notch of the radius articulating with the head of the ulna.
• Weak capsular strength
• There are no interosseous ligaments, increasing the mobility, and is important for full ROM of the wrist.

Radiocarpal Joint

• Synovial, ellipsoidal joint type.
• The articulating surfaces are the distal end of the radius articulating with the proximal surface of the scaphoid and lunate.
• Weak capsular strength.
• Radial Collateral ligaments limit excessive adduction/ulnar deviation of the wrist, and originate from the radial styloid process to the tubercle of the scaphoid and trapezium.
• Radiocarpal ligaments, palmar ligaments control extension with greater strength with dorsal ligaments controlling flexion.

Ulnomeniscotriquetral Joint

• Synovial, ellipsoidal joint type.
• The articulating surfaces are the meniscus (triangular piece of fibrocartilage distal to ulnar head) articulating with the proximal surface of the triquetrum.
• Weak capsular strength
• Ulnar Collateral ligaments limit excessive abduction/radial deviation of the wrist, and runs from the ulnar styloid process to the triquetrum and hamate.
• The Meniscus prevents direct articulation of the ulna and triquetrum, preventing extension of the ulna
• The Disc extends from the ulnar side of the distal radial articular surface to the ulnar styloid process.
• The Disc acts as a major stabilizer and cushion for the wrist joint, and can be damaged with forced extension and pronation.

Functional Anatomy

• The midcarpal joint is located between the proximal and distal rows of carpals, which increases mobility, and is important for full ROM of the wrist.
• The UMT (Ulnocarpal) involves 1° of supination and pronation, The Radiocarpal and Ulnocarpal include 2° of flexion-extension and radial deviation-ulnar deviation.
• Osteokinematics of the Distal RU is 1 degree of freedom with Supination and pronation.
• Osteokinematics of the Radiocarpal & Ulnocarpal (UMT) is 2 degrees of freedom with Flexion-Extension, Radial Deviation-Ulnar Deviation
• The Head of the ulna is convex.
• The Carpals (scaphoid, lunate, triquetrum) equal convex
• The Radius and meniscus equal concave
• The Ulnar notch of the radius is concave
• The resting position of the Distal RU is 10° supination
• The resting position of the Radiocarpal & Ulnocarpal (UMT) is neutral, slight ulnar deviation
• The resting position of the Midcarpal is Neutral, or slight Flexion with Ulnar Deviation
• The closed pack position of the Distal RU is 5° supination
• The closed pack position of the Radiocarpal & Ulnocarpal (UMT) is full extension.
• The closed pack position of the Midcarpal is extension with Ulnar Deviation.
• The Capsular pattern of Restriction in the Distal RU is extreme rotation.
• The Capsular pattern of Restriction in the Radiocarpal & Ulnocarpal (UMT) is limitation that is equal in all directions.
• The Capsular pattern of Restriction in the Midcarpal is Flexion equals Extension.
• ROM Supination is 0-90° firm, pronation (0-70/90°) firm/hard
• ROM Flexion is 0-80° firm
• ROM Extension is 0-70° firm/hard
• ROM Radial Deviation is 0-20° firm/hard
• ROM Ulnar Deviation-0-30° firm/hard

TFCC

• The TFCC is the Triangular fibrocartilage complex
• The TFCC includes the disc of the UMT, it is an important structure for stability of the wrist
• The TFCC injury is most aggravated by extension with pronation (under load)
• The TFCC is poorly vascularised and has slow healing

Wrist Biomechanics

• The wrist complex includes the distal radioulnar joint, radiocarpal joint, and midcarpal joint.
• The radiocarpal joint includes the articulation between the TFCC and the carpals because it acts as an extension of the ulna and the UMT joint.

Flexion-Extension Mechanics

• The axis of Flexion-Extension is the capitate.
• Flexion occurs primarily at the midcarpal joint, and extensions primarily occurs at radiocarpal joint.
• Radiocarpal Closed Pack (Full extension) is caused by asymmetry of scaphoid movement, relying on movement of lunate on scaphoid
• The closed pack increases risk of injury that includes the most common fractured carpal, the scaphoid; and the most common dislocated bone, the lunate (palmar direction). Both are at risk of avascular necrosis. dorsal glide proximal carpals help mob to increase finger flexion. palmar glide proximal carpals help mob to increase finger extension.

Radial-Ulnar Deviation Mechanics

• The axis of deviations is the capitate.
• movement is opposite and convex-on-concave.
• In Ulnar deviation, proximal and distal row of carpals do radial glide.
• In radial deviation, proximal and distal row of carpals do ulnar glide.

Hand Biomechanics

• The mobility between the rows of carpals is important for full ulnar deviation or radial deviation.
• There is 1 longitudinal arch per digit, and is most important through digit 3 and the capitate.
• There are 2 transverse arches: The transverse carpal arch and the transverse metacarpal arch
• The transverse carpal arch runs through the distal row of carpals, sometimes called the proximal transverse arch.
• The transverse metacarpal arch runs through the head of the metacarpals, sometimes called distal transverse arch consisting of heads of the metacarpals.
• The focal point is MC 3, capitate and lunate
• Only index finer flexes in sagittal plane, all others flex in oblique plane towards scaphoid.
• The wrist provides a stable base for the hand, and its position controls the length of the extrinsic hand muscle.
• Movements of the wrist are usually in reverse of the movements of the fingers and reinforce external muscles.
• The wrist extensors activates to stabilise wrist and prevent long finger flexors from simultaneously flexing the wrist while in finger flexion.
• Wrist flexors activate to stabilise the wrist while in finer extension
• Long finger extensors can function more effectively.
• As grip strength increases, extensors slacken which allows a favorable strong contraction
• Greatest interphalangeal flexion force occurs in ulnar deviation and neutral flexion-extension.
• Weakest interphalangeal flexion force occurs when the wrist is in full flexion due to the length to generate force.

Dorsal Digital Expansion

• The Dorsal Digital Expansion originates on posterior, medial, lateral surfaces of proximal phalanges 1 through 5.
• Extrinsic tendons are ED & EPL, and intrinsic tendons are lumbricals and interossei.
• Trifurcation on dorsal aspect.

Prehension (grip)

• Power grips involve object contact with palm and are isometric.
• Precision Grip involves object not contacting the palm and is isotonic.
• Grabbing usually involves median/ulnar nerves, and release involves the radial nerve.

Swan Neck

• Swan Neck is when the MCPs are in Flexion, PIPs are in Extension, and DIPs are in Flexion
• Muscle contracture causes or tearing volar plate at the PIP joint, also found from rheumatoid arthritis or post trauma.

Boutonniere

• Boutonniere is when the MCPs are in Extension, PIPs are in Flexion, and DIPs are in Extension
• Rupture of central slip at PIP of Dorsal Digital Expansion, rheumatoid arthritis or post trauma.

Deformities

• Dupuytren's Contracture is a contracture of palmar fascia including skin, it affects the MC digits 4 and 5, and the MCP and PIP joints have fixed flexion deformity.
• Heberden's Nodes are arthritic changes on dorsal surfaces of DIPs
• Bouchard's Nodes are arthritic changes on dorsal surfaces of PIPs
• Ulnar Drift with RA involves changes in MCP and resulting pull on long tendons
• Radial Drift with OA
• Z deformity of thumb, MCP Flexion, IP Hyperextension due to RA or hereditary
• Mallet Finger is when Distal phalanx is flexed, and results from rupture or avulsion of extensor tendon at distal insertion.

Neurological Deformities: Ulnar Nerve (C8-T1)

• Bishop's Hand aka Benediction Hand (Magee) is in resting position.
• Loss of ulnar lumbricals leads to digits 4 & 5 resting in a position opposite to the lumbricals' action.
• Claw Hand (Rattray) in resting position
• It is the same as Bishop's hand, but said to have some abduction of digits 4 & 5.
• Froment's Sign is in active position.
• The Loss of adductor pollicis (innervated by the ulnar nerve) leads to compensatory recruitment of flexor pollicis longus (innervated by median nerve).

Neurological Deformities: Median Nerve (C5-T1)

• Ape Hand (Magee, Rattray) in resting position
• The Thenar muscle wasting causes the thumb to rest in line with the other digits and inability to oppose or flex thumb.
• Oath Hand (Rattray) in active position
• Attempts to make a fist are unsuccessful
• The ulnar digits 4 & 5 flex but median digits 1, 2, 3 do not and looks similar to previous deformaties.

Neurological Deformities: Combined Median Nerve (C5-T1) & Ulnar Nerve (C8-T1)

• Claw Fingers (Magee) in resting position
• Loss of finger flexors leads to resting finger extension deformity that stops cupping of the hand.

Neurological Deformities: Radial Nerve (C5-T1)

• Wrist Drop (Rattray) aka Drop Wrist (Magee) in resting position.
• Loss of extensors leads to flexed wrist and finger posture with inability to extend wrist or fingers.

Pathologies

• Carpal Tunnel Syndrome involves median nerve compression due to decreased space in tunnel or increased size of contents inside tunnel, which may be due to external pressure on the wrist, and important to differentiate pronator teres as an alternate compression site of the median nerve.
• Dupuytren's Contracture affects the palmar fascia with 3 layers (longitudinal, transverse, vertical), an idiopathic condition causing sign and symptoms of a tender, thick, nodular palmar fascia with MCP & IP joints stuck in flexed position due to fascial shortening, where palmaris longus indirectly affected.

Skier's Thumb / Gamekeeper's Thumb

• A UCL sprain of the first MCP joint in between a highly mobile saddle joint (CMC) and a very ridid hinge joint (IP) and is vulnerable to instability.
• UCL dysfunction may be from acute trauma such as forceful abduction or radial deviation of the thumb away from the palm to the the CMC, may lead to laxity in the radial of the tomb.
• 1st CMC OA is common in older adults and causes pain and relative instability of the 1st CMC (due to capsular laxity)
• De Quervain's
• Scaphoid fracture or dislocation, if trauma occurred at the onset of symptoms
• Radial nerve irritation

Fractures & Dislocations

• Colles Fracture (Dinner Fork) involves the radius fragment displaced dorsally just proximal to wrist from FOOSH, and complications such poor union and reflex sympathetic dystrophy.
• Galeazzi Fracture involves radius fracture with dislocation of distal radioulnar joint with complications of nerve damage.

Trigger Finger

• Thickening of flexor tendon sheath (FDS)
• Nodules developing along affected tendon, usually beginning at the MCP just distal to the palm crease
• Sticking of finger in flexed position > cannot return to extended position,
• Painful snapping sensation
• The nodules are palpable and a click, catch, or lock is often observed or palpated during flexion-extension. Movement is considered painful, but there needs to be a full ROM to do its job.

Finger Arthritis

• Both RA mainly affects the MCPs with RA typically presenting as hypermobile due to destruction of the joint capsule over time from chronic inflammation
• OA presents better prognosis than RA with OA typically presents as hypomobile and mainfests in Bouchard's nodes on the PIPs and Heberden's nodes on the DIPs
• Both may present with ulnar drift primarily at the MCP
• Overall hand function can be severely reduced including grip and pinch

DeQuervain's Syndrome

• There are 3 syndromes of radial wrist pain in Table 16-13
• Affects Abductor pollicis longus & extensor pollicis brevis that includes Tenosynovitis (inflammation of tendon sheath)
• Repetitive ulnar-radial deviation and forceful gripping contribute to this condition
• Identification and modification of the provoking movement are beneficial to treat

TFCC Injury

• TFCC injuries are one of the most common causes of ulnar wrist pain
• Most are traumatic FOOSHs with hyperextension or a rotation injury. However, slow onset through repetitive stress is also possible
• Pain worse with weight bearing or carrying heavy objects along with weight bearing, and ROM

Home Care

• Strengthen weak muscles and stretch short muscles.
• Think about isolating intrinsic hand muscles (wrist movement from extrinsic possible)
• Think about creative ways to strengthen different finger and movements

Test your knowledge of common hand and wrist conditions, including nerve injuries (ulnar, radial, median), ligament sprains, and deformities. Questions cover symptoms, affected nerves, and expected postures associated with these conditions.