Introduction Joint includes ulnohumeral joint radiocapitellar joint proximal radioulnar joint Elbow function crucial for activities of daily living acts as a lever arm when positioning the hand functions as a fulcrum for forearm lever ROM Functional ROM 30° to 130 flexion/extension total ROM is 0-150 degrees 50° supination/pronation Normal carrying angle normal valgus carrying angle 5-10° for males 10-15° for females this diminishes with flexion Axial loading in extended elbow 40% of weight is through ulnohumeral joint 60% of weight is through radiohumeral joint Osteology & Arthrology Osteology spiral groove the shaft for humerus has a spiral groove posteriorly (contains radial nerve) this lies approximately 13 cm proximal to the articular surface of trochlea distal flare the distal flare of humerus includes the medial and lateral epicondyles the flare accounts for half of the elbow joint trochlea is spool shaped and is located medially capitellum located laterally sublime tubercle the sublime tubercle on the ulna is where the anterior bundle of the medial ulnar collateral ligament attaches distally columns distal humerus contains medial and lateral column Arthrology axis and alignment anterior tilt the joint surface is anteriorly tilted approximately 30 deg relative to shaft of humerus varus/valgus 6 deg of valgus rotation internally rotated by 5 deg axis of rotation is centered at trochlea and capitellum it passes through anteroinferior medial epicondyle joint type pivot joint - the radiohumeral articulation is a pivot joint radial head is covered by cartilage for approximately 240 degrees the lateral 120 degrees contains no cartilage this is crucial for internal fixation of radial head fractures hinge joint - the ulnohumeral articulation is a hinge joint coronoid fossa coronoid fossa on distal humerus receives the coronoid tip in deeper flexion coronoid tip the coronoid tip has a buttress effect in the prevention of posterior dislocations capsule capsule is maximally distended at 70-80 deg of flexion distal attachment of anterior capsule is found 6 mm distal to tip of coronoid coronoid is an intra-articular structure Muscles of the Elbow Flexors biceps the distal biceps attachment is at the level of the radial tuberosity brachialis the attachment of the brachialis 11 mm distal to the tip of the coronoid brachoradialis Extensors triceps Ligaments & Stability of Elbow Primary static stabilizers ulnohumeral joint (coronoid) loss of 50% or more of coronoid height results in elbow instability medial (ulnar) collateral ligament (MCL) overview the MCL is composed of the anterior, posterior and transverse bundles the MCL provides resistance to valgus and distractive stresses anatomy origin anteroinferior aspect of medial epicondyle insertion sublime tubercle of medial coronoid process components anterior bundle of MCL most important restraint against valgus stresses radial head is second most important posterior bundle of MCL the posterior bundle forms the floor of the cubital tunnel primary restraint to valgus stress in maximal elbow flexion if this is contracted, flexion may be limited transverse bundle of MCL lateral collateral ligament complex (LCL) overview consists of the radial collateral ligament (RCL) lateral ulnar collateral ligament (LUCL) function primary restraint to varus and external stress during full arc of elbow motion origin posterior lateral epicondyle insertion crista supinatoris of proximal ulna accessory collateral ligament some believe that the the accessory collateral ligament and the radial collateral ligament contribute substantially to lateral elbow stability annular ligament provides stability to the proximal radioulnar joint anatomy the LCL arises from isometric point on lateral aspect of capitellum function optimal stability is conferred with an appropriately tensioned LCL repair Secondary static stabilizers radiocapitellar joint this functions as an important constraint to valgus stress the radial head provides approximately 30% of valgus stability this is most important at 0-30 deg of flexion/pronation capsule greatest contribution the capsule on stability occurs with the elbow extended origins of the flexor and extensor tendons Dynamic stabilizers includes muscles crossing elbow joint anconeus brachialis triceps biceps they provide compressive stability Nerve of the Elbow Musculocutaneous nerve origin lateral cord of the brachial plexus anatomy at elbow it exits laterally, distal to the biceps tendon it will terminate as the LABC (forearm), which is found deep to the cephalic vein innervation at elbow it supplies the biceps and brachialis the nerve runs between these muscles Radial nerve origin posterior cord of the brachial plexus anatomy at elbow it leaves the triangular interval (teres major, long head of triceps and humeral shaft) found in spiral groove 13 cm above the trochlea pierces lateral intermuscular septum 7.5 cm above the trochlea this is usually at the junction of the middle and distal third of the humerus lies between the brachialis and the brachioradialis distally it is located superficial to the joint capsule, at the level of the radiocapitellar joint Median nerve origin medial/lateral cords of the brachial plexus anatomy at elbow it courses with brachial artery, running from lateral to medial lies superficial to brachialis muscle at level of elbow joint innervation at elbow it gives branches to elbow joint it has no branches in upper arm Ulnar nerve origin medial cord of brachial plexus anatomy at elbow runs medial to brachial artery, pierces medial intermuscular septum (at the level of the arcade of Struthers) and enters posterior compartment it traverses posterior to the medial epicondyle through the cubital tunnel innervation at elbow it gives branches to elbow joint it has no branches in upper arm first motor branch to FCU is found distal to the elbow joint Blood Supply of Elbow Brachial artery is located medially in the upper arm it enters cubital fossa laterally contents-- biceps tendon (lateral), brachial artery, median nerve (medial) lateral border--brachoradialis medial border--pronator teres proximal border --distal humerus at the level of elbow it splits into the radial and ulnar arteries Principle branches superior/inferior ulnar collateral nutrient/muscular supratrochlear Kinematics Motion vectors flexion and extension the axis of rotation is found at the center of trochlea pronation (pronator teres and quadratus) & supination (biceps and supinator) the axis of motion is found at the capitellum through to the radial/ulnar heads this effectively forms a cone Joint reaction force there are large joint reaction forces due to short and inefficient lever arms around elbow (biceps inserts not far from center of rotation) this contributes to degenerative changes of the elbow Center of rotation (COR) is a line through isometric points on the capitellum about trochlea the axis of pronation / supination is a line drawn from capitellum, through radial head, to distal ulna Free Body Diagram Free body diagram demonstrate inefficiencies of elbow sum M = 0 5B = 15W B = 3W Static loads are close to body weight Dynamic loads are greater than body weight Arthrodesis Optimal position in a unilateral arthrodesis 90° of flexion 0-7° of valgus in a bilateral arthrodesis one elbow in 110 ° of flexion for feeding one elbow in 65 ° of flexion for perineal hygiene Diagnostic Injections Intra-articular injection best given in soft spot formed by lateral epicondyle the olecranon radial head