Upper-Extremity Anatomy, Biomechanics & Neurophysiology Review

31 question-and-answer flashcards covering upper-extremity anatomy, biomechanics, neurophysiology, and clinical rehab concepts derived from the lecture notes.

Which ulnar variance increases ulnar-side wrist compression and risk of TFCC injury?

Ulna plus (ulna longer than radius).

How is the 20 % hand-borne compressive load dispersed during closed-chain elbow extension?

Via the TFCC → interosseous membrane, aided by muscle contraction, up to the humerus.

Beyond binding radius to ulna, how does the central band of the interosseous membrane protect the humeroradial joint during powerful flexion plus pronation/supination near full extension?

It distributes large myogenic compression forces generated by proximal pull of the radius, limiting stress on the capitulum.

Minimum combined pronation–supination ROM needed for most ADLs (with ~120° elbow flexion)?

≈30° pronation and 30° supination (60° total).

Primary supinators when tightening a screw with a flexed elbow and why the biceps helps so much:

Supinator and biceps brachii; biceps attaches to the radial tuberosity and via the bicipital aponeurosis, letting it generate strong supination in flexion.

Small posterior muscle that stabilizes the elbow and prevents capsule pinching during extension:

Anconeus.

Nerve most vulnerable to a blow on the posteromedial elbow causing ring- and little-finger paresthesia:

Ulnar nerve (superficial in a bony/myofascial tunnel).

C7 myotome lesion chiefly compromises which elbow/forearm actions?

Elbow extension and forearm pronation.

Profunda brachii artery: first brachial branch—supply area and accompanying nerve?

Supplies posterior compartment of arm and travels with the radial nerve.

Cerebellar region for gross limb movement coordination that, when damaged, causes dysmetria but spares fine motor skills:

Spinocerebellum.

Role of basal ganglia direct (Go) vs. indirect (No-Go) pathways in wrist/hand motion:

Direct pathway facilitates desired movement initiation; indirect pathway suppresses unwanted movement, keeping the hand still.

Inability to judge an object’s weight despite intact light touch indicates loss of which cortical sensation and processing area?

Barognosis interpreted in the secondary somatosensory cortex (and association areas).

Mechanism of reciprocal inhibition during voluntary elbow flexion:

Type Ia afferents from the agonist activate interneurons that inhibit α-motor neurons to the antagonist.

Arthrokinematics of the ulna on the humerus during elbow flexion (concave-on-convex rule):

Ulna rolls and glides anteriorly (same direction as the motion).

Primary structural source of humero-ulnar joint stability:

Tight fit between the trochlea and trochlear notch.

Bony check that limits full elbow extension:

Olecranon process contacting the olecranon fossa.

Radial collateral (lateral) ligament resists which force and blends with what structures?

Resists varus; splits to blend with the annular ligament of the radius and supinator crest of the ulna.

Ulnar variance associated with lunatomalacia and lunotriquetral hypermobility after FOOSH:

Ulna minus (ulna shorter than radius).

How the anterior deltoid contributes to elbow extension during a closed-chain push-up:

By producing horizontal adduction/shoulder flexion that, in the closed chain, is coupled with elbow extension torque.

Clinical reason to emphasize minimal ROM needed for ADLs in rehab planning:

Ensures treatment priorities let patients regain essential task performance even when full normative ROM is unattainable.

Condition that markedly increases biceps brachii activity and the anatomical basis:

Elbow flexion combined with forearm supination; biceps inserts on the radius and via bicipital aponeurosis, enabling dual flexor–supinator action.

Combined cerebellar & basal ganglia contributions to controlled elbow/forearm movement:

Cerebellum refines smoothness/accuracy; basal ganglia handle initiation, timing, and termination.

Proximal radioulnar arthrokinematics during open-chain pronation/supination:

Convex radial head spins within the concave radial notch and annular ligament.

Motor control problems of initiation, timing, and stopping movements point to dysfunction in which circuit?

Basal ganglia motor circuit.

Elbow flexor with greatest CSA that works regardless of forearm position:

Brachialis.

How the interosseous membrane + muscle activity protect the radiohumeral joint from high compression:

Muscle contractions pull the radius proximally; the membrane transmits and disperses that load to the ulna/humerus, relieving the capitulum.

Movements that tighten the anterior MCL vs. the lateral (ulnar) collateral ligament:

MCL-anterior: valgus, extension, flexion. LCL: varus, external (supination) rotation, flexion.

Typical site where the brachial artery bifurcates into radial and ulnar arteries:

Within the cubital fossa.

Cerebellar region most critical for precise, fine, distal voluntary hand movements (e.g., playing piano):

Cerebrocerebellum.

Arthrokinematics at the distal radioulnar joint during open-chain supination:

Concave ulnar notch of the radius rolls and glides posteriorly (same direction) on the convex ulnar head.