Types

A list of the most common injuries to the shoulder girdle includes:

• Fractures of the sternum
• Dislocations and fracture dislocations of the sternoclavicular joint
• Fractures of the shaft of the clavicle
• Fractures of the outer end of the clavicle
• Acromioclavicular separation
• Fractures of the acromion process
• Fractures of the coracoid process
• Fractures of the blade of the scapula
• Fracture of the tip of the shoulder blade
• Fractures of the neck of the glenoid
• Fractures of the glenoid
• Glenohumeral dislocation
• Fracture of the greater tuberosity
• Head-splitting fracture of the humeral head
• Fracture of the neck of the humerus
• Fracture dislocation of the glenohumeral joint

Fractures of the sternum are usually caused by impact against the front of the chest such as that caused by the steering wheel in a motor vehicle accident. Even if they are quite displaced these fractures are likely to heal without causing a problem. The impact is in a dangerous area, however, and a sternal fracture may be an indication that vital structures in the chest may also be damaged.

Dislocations and fracture-dislocations of the sternoclavicular joint may be caused by an impact on the region of the joint. Lateral compression may also be transmitted up to the joint and force the clavicle to dislocate either in front or behind the sternum. A fragment of the clavicle or the sternum may be broken off as the dislocation occurs. Dislocation behind the sternum may cause serious problems with pressure on vital structures such as the windpipe or the large blood vessels close to the heart. Patients with this injury may be transferred to a tertiary center for treatment. The injury is rare and may be quite unstable. The region is more familiar to chest surgeons than most orthopaedic surgeons and it is advisable to have back up from a team capable of dealing with the possibility of damage to large vessels.

A fracture of the shaft of the clavicle is a common injury and is often caused by a direct impact on the mid-portion of the clavicle. It can also be caused by a bending force - a force pushing the shoulder back can result in a mid-shaft fracture of the collarbone with the outer part angled back. This can be an open fracture as the sharp end of the broken bone cuts through the skin. Mid-shaft clavicle fractures can also be the result of a fall on the outstretched hand. The force is transmitted up to the collarbone as the link between the arm and the rest of the skeleton. Fractures of the shaft of the collarbone have a good reputation for healing and are often treated nonoperatively.

Fractures of the outer end of the clavicle are nearly always caused by a downward blow on the shoulder. The arm and shoulder blade are forced downwards breaking the collarbone near its joint with the shoulder blade. This injury is unstable - usually all the ligaments connecting the collarbone to the shoulder blade are disrupted as well. The weight of the arm continues to pull the fracture ends apart. Mobility at the fracture site makes it unlikely to heal. For this reason this fracture is usually treated by surgery.

Acromioclavicular separation is usually also caused by a downward blow on the shoulder. In this instance the some or all of the ligaments tear but the bone is intact. There is often significant deformity at the joint with the clavicle sticking up like a piano key. The outcome of this injury depends on the degree of ligament damage. When some ligaments are intact the joint will regain its stability and function well. This outcome may also occur with more complete ligament tears but it is less predictable. Treatment of high grade tears is controversial since the outcome from nonoperative treatment may be quite satisfactory; earlier methods of surgical treatment had a high incidence of complications. With modern methods of fixation surgical treatment has become more popular.

Fractures of the acromion process may be result of a blow on the tip of the shoulder. The area is also the point of attachment of the strong triceps muscle so an avulsion fracture may occur. Unless the fracture is severely displaced it is unlikely to compromise function of the shoulder joint. Most often this fracture can be treated nonoperatively but on occasion it will be treated by opening up the fracture site surgically, replacing the fragment and fixing it in place with a screw. This procedure is referred to as an open reduction and internal fixation (ORIF).

Fractures of the coracoid process are nearly always an avulsion fracture. The muscles that bend the elbow take origin from this point of bone. If they are contracting to bend the elbow when the load suddenly is increased and the elbow is straightened anyway, the muscles may pull off their point of attachment. Usually this can be treated non-operatively.

Fractures of the blade of the scapula are usually caused by blows on the back of the scapula, often in the context of multiple trauma. The injury itself may be quite spectacular with extensive star shaped fracture patterns, but healing almost always occurs without intervention. A large degree of displacement can be tolerated without loss of function. The main function of the blade of the scapula is as a site of attachment of muscle. On rare occasions the healed scapula is so distorted that the normal gliding motion of the scapula against the ribs is affected and the shoulder blade may catch as it moves over the ribs.

Fracture of the tip of the scapula is usually an avulsion fracture. Powerful muscles attach to the lower tip of the scapula. These muscles act to either rotate or stabilize the scapula against the chest. Since most of the muscles that move the arm attach to the scapula, one important function of the muscles that go between the rib cage and the scapula is to hold the blade still. They tend to "lock" and clamp the scapula to the chest wall. In this situation, if a force on the arm is enough to move the scapula back away from the chest wall, the muscle attachment to the tip is pulled off. Bracing your arm before impact may result in this injury. Usually it can be treated non-operatively.

Fractures of the neck of the glenoid occur as a result of lateral compression forces. A blow on the side of the shoulder is transmitted through the head of the humerus to the glenoid. More rarely a fall to the side with the arm out to the side may result in the same type of injury. A very forceful dislocation of the glenohumeral joint might also cause this injury, but fractures of the rim of the glenoid are more common in that situation. Fractures of the neck of the glenoid are also associated with fractures of the blade of the scapula. In most situations the injury can be treated nonoperatively.

Fractures of the glenoid occur due to the same type of force that breaks the neck of the glenoid. More commonly, a glenoid fracture occurs when the shoulder dislocates and a fragment of the joint goes with it. A fracture involving the glenoid results in an irregular portion of the joint surface. Unless it is perfectly reduced after the dislocation is back in joint, the fragments are usually treated by surgery (ORIF). Some surgeons may elect to manage this fracture with arthroscopic surgery.

Glenohumeral dislocation results from the shoulder (glenohumeral) joint being twisted beyond its limits. The most common position causing this dislocation is excessive abduction and external rotation - with the elbow level with or above the shoulder the hand is forced back; the shoulder forward, out of joint, by a "crank-shaft" action. Dislocation backwards also occurs. Sometimes the dislocation has been reduced at the scene of the accident and the fracture is an indication that there has been a dislocation. Damage to the axillary nerve occurs quite commonly with anterior dislocation. It is important to look for weakness of the triceps muscle and numbness over the side of the shoulder after a dislocation or suspected dislocation, as these are signs of injury to this nerve.

Related Document: A Patient's Guide to Shoulder Dislocations

Fracture of the greater tuberosity is an avulsion fracture. By itself it occurs from over-action of two of the rotator cuff muscles - the supraspinatus and infraspinatus. More commonly it happens when there is an anterior dislocation of the glenohumeral joint. One important function of the rotator cuff muscles is to resist dislocation. If the dislocation happens anyway, despite the pull of these muscles, they may pull off a chunk of bone at their point of attachment - the greater tuberosity. After the dislocation has been reduced the shoulder needs to be re-x-rayed to determine the position of the greater tuberosity fragment. If it is still significantly displaced it will interfere with abduction and rotation of the glenohumeral joint. In these cases it should be replaced in its position and fixed (ORIF).

Head-splitting fracture of the humeral head only occurs when the glenohumeral joint is dislocated. In a violent dislocation the head of the humerus may be driven against the edge of the glenoid splitting a portion of the head off. This injury creates two serious problems. The split fragment has lost its blood supply and the fracture has damaged the joint surface of the head of the humerus. After the dislocation is reduced, it is unusual for the floating fragment to stay in the correct position. Usually this injury must be treated by surgery either to remove the loose piece or to fix it back in position. A lesser version of this injury where the humeral head is only dented is very common after a dislocation. This dent in the humeral head is called the Hill Sachs Lesion and rarely needs treatment.

Fracture of the neck of the humerus is one of the most common fractures of the shoulder girdle. It usually occurs as a result of a fall on the outstretched hand with the force being transmitted up to the shoulder. It is a common fragility fracture in the elderly occurring in combination with osteoporosis. The injury can also occur in younger people as a result of more severe forces - motor vehicle accidents, falls from a height, and collisions in sports. The pattern of fracture in the region of the neck of the humerus can be quite variable. The simplest pattern is a transverse fracture through the neck region. More complex fractures involve other portions of the proximal humerus as well as the transverse fracture. If both the greater and lesser tuberosities are broken off, the blood supply of the head of the humerus is threatened. Because of the variety in severity, there are a number of potential ways to treat a fracture of the neck of the humerus ranging from symptomatic treatment only through closed reduction, closed reduction with pin fixation through the skin, ORIF, up to shoulder replacement in selected cases.

Fracture and dislocation of the glenohumeral joint is rare. It usually results from high energy trauma with a severe blow to the side of the shoulder. The head of the humerus is driven out of joint and is broken off the shaft of the humerus as well. This injury also has a high incidence of injury to nerves. Since an the intact humerus is used as a lever arm to reduce most shoulder dislocations a fracture dislocation is difficult to put back in joint. Very frequently it requires an operation to reduce the dislocation and fix the fracture. Even at surgery reducing the humeral head back into joint can be difficult. The joint surface of the humeral head is often damaged in this fracture pattern and it is a challenge to make the shattered bone stable again. Strictly speaking glenoid rim fractures and greater tuberosity fractures may also be fracture dislocations but they have a very different pattern and outcome.