• Main theme is that primate upper extremity anatomy represents the requirements of stability exchanged for mobility. The sacrifice of stability for mobility leads to many clinically relevant problems (shoulder and elbow instability, fractures, tendonitis, compressive neuropathies, shoulder impingement)
• Evolutionary Examples:
• Extremities: our limbs extend out more than other comparable species and have a better range of motion due to better development
• shoulder: articulations between clavicle, sternum, scapula; enlargement of the coracoid, scapular spine, and acromium; Broad infraspinatous fossa; large deltoids Þ all developments lead to a better range of motion
• elbow: maximum articular congruity; stability in extension (due to olecranon process), mobility in flexion, suspensory locomotion, 10° -13° valgus (bent outward from midline)

• Typically occurs during a backward fall onto an outstretched hand Þ causes collateral ligament injury.
• Recurrent dislocations are uncommon. Although there is frequently a loss of motion.
• Treatment: atraumatic reduction (put it back in position), early mobilization and physical therapy (to reduce fibrous scarring)

• 98% of all shoulder dislocations are TRAUMATIC and ANTERIOR
• Recurrent dislocations are virtually certain in young people (94% recurrence < age 20, 10% > 40)
• Shoulder dislocation vs. Shoulder separation ("shoulder pointer")
• Separation: recall that the acromioclavicular and the coracoclavicular ligament attach the lateral end of the clavicle to the acromion and coracoid process of the scapula. A separation in either of these ligaments allows the clavicle to displace superiorly and protrude (hence "shoulder pointer").
• Dislocation: recall that no tendons support the fibrous capsule of the shoulder joint INFERIORLY; hence making it the weakest area of the rotator cuff. A dislocation typically occurs when the joint is abducted tilting the head of the humerus on to the inferior portion of the capsule. A hard blow to the humerus drives it from the glenoid cavity usually stripping the fibrous capsule and the glenoid labrum from the anterior aspect of the glenoid cavity. The humerus comes to rest anteriorly because of the strong flexor and abductor muscles of the shoulder pulling it up.
• Treatment: atraumatic reduction, brief immobilization followed by PT, surgery for recurrence

• Can result from compression, stretch, or friction of ulnar, radial, and median nerves.
• Assault upon the following nerves can result in:
• Ulnar Þ most common in athletes (throwers); attributed to tensile forces where the nerve passes posterior to the medial epicondyle of the humerus
• Anterior interosseous (branch of the Median nerve)Þ Pronator syndrome
• Posterior interosseous (branch of the Radial nerve) Þ Lateral epicondylitis
• Median Þ Carpal tunnel syndrome

• Results from compression within the Carpal canal (holds the median nerve)
• Seen in patients 30-60 years old; women/men (5:1)
• Clinical Manifestations: Parasthesia (palmar surface); weakness (thenar muscles); thenar atrophy (recurrent branch of median nerve)
• Clinical tests (signs):
• Tinel’s sign: a positive sign produces a sensation of tingling or of "pins and needles" felt in the distal extremity of a limb when percussion is made over the site of an injured nerve. For Carpal, the percussion is made on the median nerve over the carpal tunnel and radiates sensation over the area of the index finger.
• Phalen’s sign
• EMG (used to comfirm decreased conduction velocity)
• Treatment: Night splinting, steroid infection, surgical decompression (division of the flexor retinaculum), success rates related to worker’s compensation or litigation status

• Results from inflammation of the common extensor attachment of the superficial extensor muscles of the forearm
• Clinical Manifestation: pain and point tenderness near the lateral epicondyle of the humerus, repetitive grasping in pronation
• Clinical tests (signs): supinate and lift Þ no pain; pronate and lift Þ pain
• Treatment: Non-operative (rest, anti-inflammatory meds, stretching)

Subacromial Impingement Syndrome – shoulder joint

• Impingement: encroachment upon the rotator cuff by the subacromial arch (supraspinatous tendon)
• Syndrome: self-perpetuating process of cuff impingement, cuff dysfunction.
• Clinical presentation: Positional, postural shoulder pain, functional problems, weakness
• Causes:
• Intrinsic Þ degenerative changes in tendons of rotator cuff (typically infraspinatous or supraspinatous), attritional wear, vascular Impairments
• Extrinsic Þ outlet stenosis, inflammation, or Loss of Depressor function (the supraspinatous functions by depressing the head of the humerus during abduction. When this is malfunctioning the head of the humerus can elevate abnormally and apply pressure to the subacromial bursa and tendons) Þ friction on rotator cuff leads to inflammation
• Treatment: nonsurgical (NSAID’s, Cortisone injection)

• Orthograde (upright) posture permits transmission of forces along the vertebral column and weight bearing joints.
• Clinical manifestations: lower back pain, degenerative arthritis (hips, knees, lumbar spine), foot problems (plantar fascitis, bunions, etc.)