Rotator Cuff Functions

Shoulder Joint Ligaments

5 principal ligaments also support this joint 3 of them, called the glenohumeral ligaments, are relatively weak and sometimes absent the other 2 are the coracohumeral ligament, which extends from the coracoid process of the scapula to the greater tubercle of the humerus, and the transverse humeral ligament, which extends from the greater to the lesser tubercle of the humerus and forms a tunnel housing the tendon from the long head of the biceps

Varus Shoulder

Angulation, bending or twisting away from the midline of the body

Valgus Shoulder

Bending or twisting towards the midline of the body

Rotator Cuff

Made up of four muscles that join together as tendons in your shoulder to form a thick covering at the top of the humerus (the bone in the upper arm). Each muscle originates on the shoulder blade (scapula) and connects to the humerus The rotator cuff has the important jobs of stabalizing the shoulder, elevating and rotating the arm, and ensuring the head of the humerus stays securely placed in the shoulder socket

Supraspinatus

Originates above the spine of the shoulder blade and inserts on the greater tuberosity of the humerus

Infraspinatus

Originates below the spine of the scapula, in the infraspinatus fossa, and it inserts on the posterior aspect of the greater tuberosity (the part of the bone that attaches to the corresponding muslce) of the humerus

Subscapularis

Originates on the anterior, or front surface of the scapula, sitting directly over the ribs, and inserts on the lesser tuberosity of the humerus

Teres Minor

Originates on the lateral scapula border and inserts on the inferior aspect of the greater tuberosity of the humerus

Shoulder is made up of 3 bones

Scapula (shoulder blade) Clavicle (collar bone) Humerus (arm bone)

Shoulder is made up of 3 joints

Glenohumeral (main joint) - comprises of a ball (humeral head) on a golf tee shaped joint (the glenoid of the scapula) Acromioclavicular Sternoclavicular

Deoltoid

The deltoid originates on the lateral aspect of the acromion and clavicle and then inserts on the lateral aspect of the humerus. Its major action is to abduct the arm (lift the arm out to the side of the body) as well as assist in forward elevation (lifting the arm out in front of the body).

Abducting or elevating the shoulder joint out to the side

These motions are performed by the supraspinatus

Similarities between Shoulders and Hips

both joints are classified as a "Ball & Scoket" joint

Posterior Circumflex Artery

branch of axillary artery that run lateral/posterior of humeral head supplies teres minor and deltoid

Glenoid cavity or Glenoid Fossa

part of the shoulder blade. It is a shallow, pyriform articular surface, which is located on the lateral angle of the scapula. It is directed laterally and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest This cavity forms the glenohumeral (ball and socket) joint along with the humerus. The humerus is held in place within the glenoid cavity by means of the long heard of the biceps tendon. This tendon originates on the superior margin of the glenoid cavity and loops over the shoulder, bracing humerus against the cavity. The rotator cuff also reinforces this joint more specifically with the supraspinatus tendon to hold the head of the humerus in the glenoid cavity

Differences between Shoulders and Hips

the humeral head articulates against the shallow depression of the glenoid fossa and not within a socket the shoulder is MUCH less constrained joint when compared to the hip the shoulder is the most mobile joint in the body though not a "load bearing" joint, the glenohumeral joint is subjected to high joint reactive forces during normal daily activities that meet and exceed 1x BW

Shoulder has one articulation

the relationship between the scapula (shoulder blade) and the chest wall

Biceps Brachii

the shoulder is mainly stabalized by the biceps brachii muscle on the anterior side of the arm one of its tendons arises from the long head of the muscle, passes through the intertubercular groove of the humerus, and inserts on the superior margin of the glenoid cavity it acts as a taut strap that presses the humeral head against the glenoid cavity 4 additional muscles help stabalize the shoulder joint (RTC muscles). RTC is fused to the joint capsule on all sides except the inferior

The bones of the shoulder are covered by several layers of soft tissues

the top layer is the deltoid muscle, a muscle just beneath the skin, which gives the shoulder a rounded appearance. The deltoid muscle helps to bring the arm overhead directly beneath the deltoid muscle is sub-deltoid bursa, a fluid-filled sac, analogous to a water ballon

Externally rotating the shoulder joint

The infraspinatus and teres minor muscles are responsible for this movement

Depressing the head of the humerus The subscapularis rotates the head of the humerus medially (internal rotation) and adducts it; when the arm is raised, it draws the humerus forward and downward. It is a powerful defense to the front of the shoulder-joint, preventing displacement of the head of the humerus.

The subscapularis muscle performs this additional function to allow the humerus to move freely in the shoulder joint during the elevation of the arm

Stabalizing the head of the humerus in the shoulder joint

The supraspinatus, infraspinatus, teres minor, and subscapularis muscles all work together to achieve this

Walch Glenoid Morphology

Type A - concentric wear, no subluxation of HH, well centered -A1: no or minor central erosion -A2: deeper central erosion, line connects anteriorly/posterior glenoid rims and transects humeral head Type B - biconcave glenoid, asymmetric glenoid wear and head subluxated posteriorly -B0: pre-osteroarthritic posterior subluxation of HH -B1: posterior joint narrowing (no posterior bone loss), osteophytes, subchondral sclerosis -B2: posterior rim erosion, retroverted glenoid -B3: mono-concave, posterior wear, at least HH subluxation > 70% OR retroversion > 15% Type C -C1: glenoid retroversion >25 degrees of erosion -C2: biconcave, posterior bone loss, posterior translation of HH Type D - glenoid anteversion or anterior HH subluxation (HH subluxation <40%)

Dislocations occur when the bones on opporsides of a joint do not line up. Dislocations can involve any of the 3 different joints:

a dislocation of the acromioclavicular joint (collar bone joint) is called a "seperated shoulder" a disclocation of the sternoclavicular joint interupts the connection between the clavicle and the breast bone (sternum) the glenohumeral joint (the ball and socket joint of the shoulder) can be dislocated toward the front (anteriorly) or toward the back (posteriorly)

Glenoid Labrum

a fibrocartiliginous structure rim attached around the margin of the glenoid cavity in the shoulder joint (ball and socket). However, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball'. The socket is deepened by the glenoid labrum, stabilizing the shoulder joint

Acromion

an extension of the scapula that forms the high point of the shoulder. Together with the coracoid process it extends laterally over the shoulder joint. The acromion is a continuation of the scapular spine, and hooks over anteriorly

Shoulder - fracture locations

commonly involve the clavicle (collar bone), proximal humerus (top of the upper arm bone), and scapula (shoulder blade)

Humeral Head Sizing - Recreating the Sphere

humeral arthroplasty should resotre natural anatomy humerous is roughly defined as a sphere on the humeral shaft sphere defined by: apex of humeral head, lateral boarder of greater tuberosity at insertion site of supraspinatus, medial calcar if implant looks more like an egg, humerus is overstuffed you want maximal coverage without overhang superiorly

Humeral Head Sizing

humeral head selected should closely mimic anatomic head size multiple factors to consider when selecting correct humeral head implant - coverage of the osteotomy surface (head diameter), humeral head height (joint tension), goal is to recreate a humeral sphere

Axillary Nerve

inferior to Glenoid (A/P) support the function of teres minor, deltoid & long head of triceps supports skin sensation scares low volume surgeons

Coracoid Process

is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula (hence: coracoid, or "like raven's beak"). Pointing laterally forward, it, together with the acromion serves to stabalize the shoulder joint It provides attachment for tendons of the biceps brachii and other muscles of the arm

Humeral Version in Anatomic Shoulder

position humeral stem within humerus to restore anatomic alignment targeting humeral retroversion of 30 degrees with a possible range of 15-40 degrees humeral stem placement should match resection humeral retroversion alignment options: -epicondylar axis/forearm reference -freehand cut -resection surface reference -bicipital groove reference

Humeral Head Sizing - Head Height

recreate proper height of humeral head relative to greater tuberosity 5-8mm superior to the greater tuberosity (use eccentric heads to adjust) can also reference pectoralis major attachment (56mm superior +/- 5mm)

Deoltoid Tuberosity

The deltoid tuberosity of the humerus lies proximally about a third of the way to the elbow and provides an attachment point for the deltoid muscle. The deltoid is a triangular muscle with three attachment points: the humerus, the clavicle, and the scapula.