Updated March 07, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

The glenoid is the socket of the ball-and-socket shoulder joint.  The glenoid is part of the scapula (shoulder blade), a thin, broad bone that sits behind the rib cage.  The scapula itself is mobile (its orientation shifts on your back with movement), and normal scapular motion is important for normal shoulder function. 

The glenoid is a projection of the outer side of the scapula.  The glenoid socket is not too deep (unlike the hip joint socket), rather, the glenoid socket is a shallow, almost flat part of the bone.

  The glenoid surface is covered by articular cartilage--the smooth lining of normal joints.  The socket of the glenoid is deepened by another type of cartilage, called the shoulder labrum, that surrounds the glenoid.  Without a normal labrum, the shoulder is prone to episodes of shoulder instability.  This often occurs when people tear the shoulder labrum, and are prone to shoulder dislocations.

Fractures of the glenoid are a relatively uncommon type of shoulder fracture.  Glenoid fractures most often occur when there is significant trauma to the shoulder, or as a result of high-energy sports injuries.  The two most common fracture patterns are:

• Glenoid Lip Fractures: Glenoid lip fractures occur when there is a shoulder dislocation or shoulder subluxation, and the ball comes out of the socket.  As the ball dislocates, it can push against the rim of the glenoid socket, causing a fragment of the bone to fracture.
  Treatment of a glenoid rim fracture is focused on restoring the normal contour of the shoulder socket to prevent recurrent instability (repeat dislocations) of the shoulder joint.  Surgical treatment is often considered for these injuries, especially when the fracture is out of position or if there is a large fragment of the glenoid bone.
  

• Genoid Fossa Fractures:  The glenoid fossa is the center portion of the socket.  Glenoid fossa fractures are much less common injuries, and often associated with severe trauma.  There is little data on the ideal treatment of these injuries, because they are so uncommon.  However, most surgeons agree that fracture management decisions must take into account both the fracture type and the patient's need.  More active patients with fractures that are not in proper position will most likely benefit from surgery to realign these injuries.

Glenoid Fracture Treatment

Treatment of glenoid fractures can be controversial as there have been very few studies to compare different treatment methods.  Because these are uncommon injuries, it is difficult to perform comparison studies as even specialized surgeons may only treat these types of injuries infrequently.

In general, it is agreed that if there is damage to the cartilage surface of the glenoid, then surgery is a reasonable treatment.  The goal of surgical treatment is to restore the alignment of the normal joint surface.  It is typical to repair the bone with small plates and/or screws to ensure that the bones heal in the proper position.

Rehabilitation after surgery to repair a glenoid fracture is focused on restoring normal mobility and strength to the shoulder joint.  Your surgeon may recommend a brief time of immobilization to allow the bones to begin to heal, but as soon as possible will begin range-of-motion exercises.  As the healing becomes stronger, you will progress to strengthening exercises of the shoulder.

Risks of surgical treatment includes infection, shoulder stiffness, nerve injury, and shoulder arthritis.  The reason people may develop arthritis of the joint is because of the trauma to the cartilage surface of the socket.  Even if surgery is performed to realign the damaged bone, the injury to the cartilage increases the chance of the development of arthritis.  People who sustain glenoid fractures are more likely to require shoulder replacement surgery later in life.

<sub>Sources:

Cole PA, et al. "Management of Scapular Fractures" J Am Acad Orthop Surg March 2012 vol. 20 no. 3 130-141.</sub>