Four Lumbricals Radial two – Median; Ulnar two - Ulnar Three Palmar Interossei - Ulnar Four Dorsal Interossei - Ulnar Thenar muscles Opponens Pollicus - Median Abductor Pollicus Brevis - Median Adductor Pollicus - Ulnar Flexor Pollicus Brevis – Superficial (median); Deep (Ulnar)
All Ulnar Nerve Hypothenar muscles Opponens Digiti Minimi Abductor Digiti Minimi Flexor Digiti Minimi Brevis Palmaris Brevis
Have 5 Annular Pulleys A2 (on Proximal phalanx) and A4 (on middle phalanx) are major pulleys (attach to shafts of phalanges) A1, A3, A5 attach to palmar/volar plates of respective joints Also have 3 Cruciate pulleys (between A2 and A3; A3 and A4; A4 and A5) thinner fibers
Extensor assembly is made up of a tendinous system composed of thee distal tendons of attachment of the extensor muscles, lumbricals, interossei, and thenar and hypothenar muscles. Purpose of the assembly is to extend the digits in different positions of finger flexion. Over the proximal phalanx the extensor tendon (from extensor digitorum) divides into a central band and two lateral bands The central band inserts at the base of the middle phalanx. The two lateral bands rejoin over the middle phalanx and insert at the base of the distal phalanx.
Over the proximal phalanx the extensor tendon (from extensor digitorum) divides into a central band and two lateral bands The central band inserts at the base of the middle phalanx The two lateral bands rejoin over the middle phalanx and insert at the base of the distal phalanx
Hood slides forward here over proximal phalanx. During flexion the lateral bands move volarly.
Early – FDP and FDS and interossei muscles actively flex the joints Late – lumbricals still inactive, assembly (hood) moves over proximal phalanx
Early – extensor digitorum is extending at MCP joint Middle – Intrinsics (lumbricals and interossei) assist extension at the PIP and DIP joints Late – Assembly (Hood) slides back over MCP joint
At MCP joints the collateral ligaments are taut or stretched to prevent shortening and prevent flexion contractures At the PIP and DIP joints there is equal tension of collateral ligaments throughout the ROM, hence splinted in extension
Deformity results from loss of intrinsic muscle action and overaction of the extrinsic extensor muscles on the proximal phalanx of the fingers. Arches of hand disappear and hand becomes “flat”.
Power grip - hammer Spherical Cylindrical Precision grip – holding an egg; holding a baseball Power (key) pinch Lateral pinch Precision pinch – tip to tip; pulp to pulp Hook grip - suitcase
Mallet Finger - Tear of the extensor tendon from the attachment on the distal phalanx Swan Neck Deformity - MCP joint subluxes volarly and PIP extends as intrinsics contract Boutonniere Deformity - Central extensor slip and lateral bands migrate volarly; extends MCP (and DIP) and flexes PIP Zig Zag Deformities from Rheumatoid Arthritis DeQuervain’s Disease -tendinitis of thumb abductors at the radial styloid process abductor pollicus longus and extensor pollicus brevis - maybe a swelling in the area, tenderness Dupuytren’s Contracture - fibrous contracture of the palmar fascia
Loss of musculocutaneous = profound weakness of forearm flexion, extension and supination Statically – forearm is pronated and extended
Most wrist and extrinsics muscles originating in the area of the medial epicondyle
Wasting of thenar eminence. Thumb falls back into line with fingers as a result of pull of extensor muscles. Unable to oppose or flex thumb
In forearm = all flexor compartment EXCEPT FCU, ulnar half of FDP = Ulnar A median nerve palsy due to a wound on the palmar aspect of the wrist. This is causing wasting and paralysis of the thenar muscles. High injury can only pronate to midpoint =
FCU and Ulnar half of FDP Cutaneous branch The muscles paralyzed are the flexor carpi ulnaris, medial half of the flexor digitorum profundus, medial two lumbricals, all interossei and the adductor pollicis Injury to the nerve at or above the elbow results in paralysis of the medial half of the flexor digitorum profundus with the loss of flexion of the distal phalanges of the medial two digits. Flexion of the wrist joint will produce abduction due to the paralysis of the flexor carpi ulnaris. The hypothenar eminence muscles will be paralysed and the eminence may be wasted. Since the interossei are paralysed the patient will not be able to hold a sheet of paper between the fingers - loss of abduction and adduction. Adduction of the thumb is lost due to paralysis of the adductor pollicis muscle. The patient gets around this loss by strongly contracting the flexor pollicis longus to bring the terminal phalanx of the thumb against the index finger. The fourth and fifth MCP joints are hyperextended due to the loss of the lumbricals and interossei , while the interphalangeal joints of the same digits are flexed. The picture is that of a 'claw hand'. The sensory loss is to the palm and both palmar and dorsal aspects of the medial one and one-half digits. Injury to the nerve at the wirst spares the flexor carpi ulnaris and the flexor digitorum profundus so that wrist flexion is normal and the fourth and fifth interphalangeal nerves are even more flexed into a claw hand.
Can’t hold paper in “lateral pinch”. If ulnar nerve injury (maybe cubital tunnel), can’t hold, IP joint will flex. (As interossei won’t hold)
Posterior compartment of the arm Superficial branch = Cutaneous only
Most wrist and extrinsics muscles originating in the area of the lateral epicondyle
The patient has injured his upper arm, usually by sleeping with his arm over the back of a chair, and now presents holding the affected hand and wrist with his good hand, complaining of decreased or absent sensation on the radial and dorsal side of his hand and wrist, and of inability to extend his wrist, thumb and finger joints. With the hand supinated (palm up) and the extensors aided by gravity, hand function may appear normal, but when the hand is pronated (palm down) the wrist and hand will drop
Test = Resisted supination and resisted middle finger extension Confused with Lateral Epicondyilits 5 points of compression= Fibrous bands, vascular leash, ECRB, Supinator, At proximal or distal edge. The goal of surgery for radial tunnel syndrome is to relieve any abnormal pressure on the nerve where it passes through the radial tunnel. The surgeon begins by making an incision along the outside of the elbow and down the forearm, near the spot where the radial nerve goes under the supinator muscle. Soft tissues are gently moved aside so the surgeon can check the places where the radial nerve may be getting squeezed within the radial tunnel. The nerve can be pinched in many spots, so it is important to check all the areas that may be causing problems. Any parts of the tunnel that are pinching the nerve are cut. This expands the tunnel and relieves pressure on the nerve. At the end of the procedure, the skin is stitched together.
Extensor muscles of the wrist are paralyzed as a result of radial nerve palsy. Wrist and fingers can not be extended.
Mallet Finger - Tear of the extensor tendon from the attachment on the distal phalanx
Swan Neck Deformity - MCP joint subluxes volarly and PIP extends as intrinsics contract
Boutonniere Deformity - Central extensor slip and lateral bands migrate volarly; extends MCP (and DIP) and flexes PIP
Chronic synovitis – periarticular tissue strength is reduced resulting in destruction of mechanical integrity of joint (deformities) from the various forces acting on the joint.
DeQuervain’s Disease -tendinitis of thumb abductors at the radial styloid process abductor pollicus longus and extensor pollicus brevis - maybe a swelling in the area, tenderness
Fibrous contracture of the palmar fascia Most common in ring and little fingers
