Shoulder presentations are uncommon (about 0.5% of births) as usually towards the end of gestation either the head or the buttocks start to enter the upper part of the pelvis anchoring the fetus in a longitudinal lie. It is not known in all cases of shoulder presentation why the longitudinal lie is not reached, but possible causes include bony abnormalities of the pelvis, uterine abnormalities such as malformations or tumors (fibroids), and other tumors in the pelvis or abdomen can also lead to a shoulder presentation. Other factors are a lax abdominal musculature, uterine overdistension (i.e. polyhydramnios), multiple gestation, placenta previa, a small fetus, or a fetus with some abnormality. Further, if the amniotic fluid sac ruptures the shoulder or arm may become wedged as a shoulder presentation.

A shoulder presentation refers to a malpresentation at childbirth where the baby is in a transverse lie (its vertebral column is perpendicular to that of the mother), thus the leading part (the part that enters first the birth canal) is an arm, shoulder, or the trunk. While a baby can be delivered vaginally when either the head or the feet/buttocks are the leading part, it usually cannot be expected to be delivered successfully with a shoulder presentation unless a cesarean section (C/S) is performed.

Shoulder dystocia is a specific case of obstructed labour whereby after the delivery of the head, the anterior shoulder of the infant cannot pass below, or requires significant manipulation to pass below, the pubic symphysis. It is diagnosed when the shoulders fail to deliver shortly after the fetal head. Shoulder dystocia is an obstetric emergency, and fetal demise can occur if the infant is not delivered, due to compression of the umbilical cord within the birth canal. It occurs in approximately 0.3-1% of vaginal births.

The major concern of shoulder dystocia is damage to the upper brachial plexus nerves. These supply the sensory and motor components of the shoulder, arm and hands. The ventral roots (motor pathway) are most prone to injury. The cause of injury to the baby is debated, but a probable mechanism is manual stretching of the nerves, which in itself can cause injury. Excess tension may physically tear the nerve roots out from the neonatal spinal column, resulting in total dysfunction.

- Klumpke paralysis

- Erb's Palsy

- Fetal hypoxia

- Fetal death

- Cerebral palsy

- Maternal post partum hemorrhage (11%)

- Vaginal lacerations and 3rd/4th degree tears, extended episiotomies

- uterine rupture

In the vertex presentation the head is flexed and the occiput leads the way. This is the most common configuration and seen at term in 95% of singletons. If the head is extended, the face becomes the leading part. Face presentations account for less than 1% of presentations at term. In the sinicipital presentation the large fontanelle is the presenting part; with further labor the head will either flex or extend more so that in the end this presentation leads to a vertex or face presentation. In the brow presentation the head is slightly extended, but less than in the face presentation. The chin presentation is a variant of the face presentation with maximum extension of the head.

Non-cephalic presentations are the breech presentation (3.5%) and the shoulder presentation (0.5%).

Factors that predispose to face presentation are prematurity, macrosomia, anencephaly and other malformations, cephalopelvic disproportion, and polyhydramnios. In an uncomplicated face presentation duration of labor is not altered. Perinatal losses with face presentation occur with traumatic version and extraction and midforceps procedures Duff indicates that the prevalence of face presentations is about 1/500–600., while Benedetti et al. found it to be 1/1,250 term deliveries.

Face presentations are classified according to the position of the chin (mentum):

- Left Mento-Anterior (LMA), Left Mento-Posterior (LMP), Left Mento-Transverse (LMT);

- Right Mento-Anterior (RMA), Right Mento-Posterior (RMP), Right Mento-Transverse (RMT);

Several symptoms are common but not specific:

- Dull, throbbing, ache in the joint which can be brought on by very strenuous exertion or simple household chores.

- Difficulty sleeping due to shoulder discomfort. The SLAP lesion decreases the stability of the joint which, when combined with lying in bed, causes the shoulder to drop.

- For an athlete involved in a throwing sport such as baseball, pain and a catching feeling are prevalent. Throwing athletes may also complain of a loss of strength or significant decreased velocity in throwing.

- Any applied force overhead or pushing directly into the shoulder can result in impingement and catching sensations.

Signs and symptoms of a dislocation or rotator cuff tear such as:

- Significant pain, which can sometimes be felt past the shoulder, along the arm.

- Inability to move the arm from its current position, particularly in positions with the arm reaching away from the body and with the top of the arm twisted toward the back.

- Numbness of the arm.

- Visibly displaced shoulder. Some dislocations result in the shoulder appearing unusually square.

- No bone in the side of the shoulder showing shoulder has become dislocated.

A SLAP tear or SLAP lesion is an injury to the glenoid labrum (fibrocartilaginous rim attached around the margin of the glenoid cavity). SLAP is an acronym for "superior labral tear from anterior to posterior".

The main causes of obstructed labour include: a large or abnormally positioned baby, a small pelvis, and problems with the birth canal. Abnormal positioning includes shoulder dystocia where the anterior shoulder does not pass easily below the pubic bone. Risk factors for a small pelvis include malnutrition and a lack of exposure to sunlight causing vitamin D deficiency. while problems with the birth canal include a narrow vagina and perineum which may be due to female genital mutilation or tumors.

Obstructed labour, also known as labour dystocia, is when, even though the uterus is contracting normally, the baby does not exit the pelvis during childbirth due to being physically blocked. Complications for the baby include not getting enough oxygen which may result in death. It increases the risk of the mother getting an infection, having uterine rupture, or having post-partum bleeding. Long term complications for the mother include obstetrical fistula. Obstructed labour is said to result in prolonged labour, when the active phase of labour is longer than twelve hours.

The main causes of obstructed labour include: a large or abnormally positioned baby, a small pelvis, and problems with the birth canal. Abnormal positioning includes shoulder dystocia where the anterior shoulder does not pass easily below the pubic bone. Risk factors for a small pelvis include malnutrition and a lack of exposure to sunlight causing vitamin D deficiency. It is also more common in adolescence as the pelvis may not have finished growing. Problems with the birth canal include a narrow vagina and perineum which may be due to female genital mutilation or tumors. A partograph is often used to track labour progression and diagnose problems. This combined with physical examination may identify obstructed labour.

The treatment of obstructed labour may require cesarean section or vacuum extraction with possible surgical opening of the symphysis pubis. Other measures include: keeping the women hydrated and antibiotics if the membranes have been ruptured for more than 18 hours. In Africa and Asia obstructed labor affects between two and five percent of deliveries. In 2015 about 6.5 million cases of obstructed labour or uterine rupture occurred. This resulted in 23,000 maternal deaths down from 29,000 deaths in 1990 (about 8% of all deaths related to pregnancy). It is also one of the leading causes of stillbirth. Most deaths due to this condition occur in the developing world.

Bone fractures can occur during a difficult delivery. Fracture of the clavicle is the most common birth injury.

Conduplicato corpore is a condition that occurs during birth if the fetus is quite small and the pelvis is large. Spontaneous delivery may occur despite persistence of the abnormal lie. In such cases, the fetus is compressed with the head forced against the abdomen. A portion of the thoracic wall below the shoulder thus becomes the most dependent part, appearing at the vulva. The head and thorax then pass through the pelvic cavity at the same time, and the fetus, which is doubled upon itself (Conduplicato Corpore), is expelled. Such a mechanism is obviously possible only in the case of very small infant and occasionally when the second preterm fetus in a twin pregnancy is born.

The brachial plexus is the bundle of nerves that runs from the neck to the hand and controls the motion of the arm and hand. The brachial plexus may be stretched and damaged during a difficult delivery. In minor cases, the nerves heal and full use of the hand and arm is recovered. In more severe cases, the child may suffer permanent nerve damage and may not have full use of the shoulder, arm, or hand. Brachial plexus injuries occur in 1-3 children per 1,000 live births.

"See Erbs Palsy and Klumpke’s Palsy."

Posterior dislocations are uncommon, and are typically due to the muscle contraction from electric shock or seizure. They may be caused by strength imbalance of the rotator cuff muscles. Patients typically present holding their arm internally rotated and adducted, and exhibiting flattening of the anterior shoulder with a prominent coracoid process.

Posterior dislocations may go unrecognized, especially in an elderly patient and in the unconscious trauma patient. An average interval of 1 year was noted between injury and diagnosis in a series of 40 patients.

A strain is a type of acute injury that occurs to the muscle or tendon. Similar to sprains, it can vary in severity, from a stretching of the muscle or tendon to a complete tear of the tendon from the muscle. Some of the most common places that strains occur are in the foot, back of the leg (hamstring), or back.

A Bankart lesion is an injury of the anterior (inferior) glenoid labrum of the shoulder due to anterior shoulder dislocation. When this happens, a pocket at the front of the glenoid forms that allows the humeral head to dislocate into it. It is an indication for surgery and often accompanied by a Hill-Sachs lesion, damage to the posterior humeral head.

The Bankart lesion is named after English orthopedic surgeon Arthur Sydney Blundell Bankart (1879 – 1951).

A bony Bankart is a Bankart lesion that includes a fracture in of the anterior-inferior glenoid cavity of the scapula bone.

A sprain is a type of acute injury which results from the stretching or tearing of a ligament. Depending on the severity of the sprain, the movement on the joint can be compromised since ligaments aid in the stability and support of joints. Sprains are commonly seen in vulnerable areas such as the wrists, knees, and ankles. They can occur from movements such as falling on an outstretched hand, or a twisting of the ankle or foot.

The severity of a sprain can also be classified:

Grade 1: Only some of the fibers in the ligament are torn, and the injured site is moderately painful and swollen. Function in the joint will be unaffected for the most part.

Grade 2: Many of the ligament fibers are torn, and pain and swelling is moderate. The functionality of the joint is compromised.

Grade 3: The soft tissue is completely torn, and functionality and strength on the joint is completely compromised. In most cases, surgery is needed to repair the damage.

Humeral avulsion of the glenohumeral ligament (HAGL) is defined as an avulsion (tearing away) of the inferior glenohumeral ligament from the anatomic neck of the humerus. In other words, it occurs when we have disruption of the ligaments that join the humerus to the glenoid.

HAGL tends to occur in 7.5-9.3% of cases of anterior shoulder instability. Making it an uncommon cause of anterior shoulder instability.

Avulsion of this ligamentous complex may occur in three sites: glenoid insertion (40%), the midsubstance (35%) and the humeral insertion (25%).

In over 95% of shoulder dislocations, the humerus is displaced anteriorly. In most of those, the head of the humerus comes to rest under the coracoid process, referred to as sub-coracoid dislocation. Sub-glenoid, subclavicular, and, very rarely, intrathoracic or retroperitoneal dislocations may also occur.

Anterior dislocations are usually caused by a direct blow to, or fall on, an outstretched arm. The patient typically holds his/her arm externally rotated and slightly abducted.

A Hill-Sachs deformity is an impaction of the head of the humerus left by the glenoid rim during dislocation. Hill-Sachs deformities occur in 35%-40% of anterior dislocations. They can be seen on a front-facing X-ray when the arm is in internal rotation. Bankart lesions are disruptions of the glenoid labrum with or without an avulsion of bone fragment.

Damage to the axillary artery and axillary nerve (C5,C6) may result. The axillary nerve is injured in 37% making it the most commonly injured structure with this type of injury. Other common, associated, nerve injuries include injury to the suprascapular nerve (29%) and the radial nerve (22%). Axillary nerve damage results in a weakened or paralyzed deltoid muscle and as the deltoid atrophies unilaterally, the normal rounded contour of the shoulder is lost. A patient with injury to the axillary nerve will have difficulty in abducting the arm from approximately 15° away from the body. The supraspinatus muscle initiates abduction from a fully adducted position.

Dead arm syndrome starts with repetitive motion and forces on the posterior capsule of the shoulder. The posterior capsule is a band of fibrous tissue that interconnects with tendons of the rotator cuff of the shoulder. Four muscles and their tendons make up the rotator cuff. They cover the outside of the shoulder to hold, protect and move the joint.

Overuse can lead to a buildup of tissue around the posterior capsule called hypertrophy. The next step is tightness of the posterior capsule called posterior capsular contracture. This type of problem reduces the amount the shoulder can rotate inwardly.

Over time, with enough force, a tear may develop in the labrum. The labrum is a rim of cartilage around the shoulder socket to help hold the head of the humerus (upper arm) in the joint. This condition is called a superior labrum anterior posterior (SLAP) lesion. The final outcome in all these steps is the dead arm phenomenon.

The shoulder is unstable and dislocation may come next. Dead arm syndrome will not go away on its own with rest—it must be treated. If there is a SLAP lesion, then surgery is needed to repair the problem. If the injury is caught before a SLAP tear, then physical therapy with stretching and exercise can restore it.

It is common among baseball pitchers as they age, and it can also occur with quarterbacks in football and handball players also as they age.

Subacromial bursitis often presents with a constellation of symptoms called impingement syndrome. Pain along the front and side of the shoulder is the most common symptom and may cause weakness and stiffness. If the pain resolves and weakness persists other causes should be evaluated such as a tear of the rotator cuff or a neurological problem arising from the neck or entrapment of the suprascapular nerve. The onset of pain may be sudden or gradual and may or may not be related to trauma. Night time pain, especially sleeping on the affected shoulder, is often reported. Localized redness or swelling are less common and suggest an infected subacromial bursa. Individuals affected by subacromial bursitis commonly present with concomitant shoulder problems such as arthritis, rotator cuff tendinitis, rotator cuff tears, and cervical radiculopathy (pinched nerve in neck).

Impingement may be brought on by sports activities, such as overhead throwing sports and swimming, or overhead work such as painting, carpentry, or plumbing. Activities that involve repetitive overhead activity, or directly in front, may cause shoulder pain. Direct upward pressure on the shoulder, such as leaning on an elbow, may increase pain.

The most common symptoms in impingement syndrome are pain, weakness and a loss of movement at the affected shoulder. The pain is often worsened by shoulder overhead movement and may occur at night, especially if the patient is lying on the affected shoulder. The onset of the pain may be acute if it is due to an injury or may be insidious if it is due to a gradual process such as an osteoarthritic spur. The pain has been described as dull rather than sharp, and lingers for long periods of a time, making it hard to fall asleep at night. Other symptoms can include a grinding or popping sensation during movement of the shoulder.

The range of motion at the shoulder may be limited by pain. A painful arc of movement may be present during forward elevation of the arm from 60° to 120°. Passive movement at the shoulder will appear painful when a downwards force is applied at the acromion but the pain will ease once the downwards force is removed.

Types of breech depend on how the baby’s legs are lying.

- A frank breech (otherwise known as an extended breech) is where the baby’s legs are up next to its abdomen, with its knees straight and its feet next to its ears. This is the most common type of breech.

- A complete breech (flexed) breech is when the baby appears as though it is sitting crossed-legged with its legs bent at the hips and knees.

- A footling breech is when one or both of the baby’s feet are born first instead of the pelvis. This is more common in babies born prematurely or before their due date.

In addition to the above, breech births in which the sacrum is the fetal denominator can be classified by the position of a fetus. Thus sacro-anterior, sacro-transverse and sacro-posterior positions all exist, but left sacro-anterior is the most common presentation. Sacro-anterior indicates an easier delivery compared to other forms.

Symptoms may occur immediately after trauma (acute) or develop over time (chronic).

Acute injury is less frequent than chronic disease, but may follow bouts of forcefully raising the arm against resistance, as occurs in weightlifting, for example. In addition, falling forcefully on the shoulder can cause acute symptoms. These traumatic tears predominantly affect the supraspinatus tendon or the rotator interval and symptoms include severe pain that radiates through the arm, and limited range of motion, specifically during abduction of the shoulder.

Chronic tears occur among individuals who constantly participate in overhead activities, such as pitching or swimming, but can also develop from shoulder tendinitis or rotator cuff disease. Symptoms arising from chronic tears include sporadic worsening of pain, debilitation, and atrophy of the muscles, noticeable pain during rest, crackling sensations (crepitus) when moving the shoulder, and inability to move or lift the arm sufficiently, especially during abduction and flexion motions.

Pain in the anterolateral aspect of the shoulder is not specific to the shoulder, and may arise from, and be referred from, the neck, heart or gut.

Patient history will often include pain or ache over the front and outer aspect of the shoulder, pain aggravated by leaning on the elbow and pushing upwards on the shoulder (such as leaning on the armrest of a reclining chair), intolerance of overhead activity, pain at night when lying directly on the affected shoulder, pain when reaching forward (e.g. unable to lift a gallon of milk from the refrigerator). Weakness may be reported, but is often masked by pain and is usually found only through examination. With longer-standing pain, the shoulder is favored and gradually loss of motion and weakness may develop, which, due to pain and guarding, are often unrecognized by the patient and only brought to attention during examination.

Primary shoulder problems may cause pain over the deltoid muscle intensified by abduction against resistance - the impingement sign. This signifies pain arising from the rotator cuff, but cannot distinguish between inflammation, strain, or tear. Patients may report that they are unable to reach upwards to brush their hair or to lift a food can from an overhead shelf.