What is Quadrilateral Space Syndrome?

Deltoid muscleQuadrilateral Space Syndrome is the term given to a rare nerve condition of the shoulder, which results in weakness and/or pain of the shoulder due to the compression of or injury to the axillary nerve and posterior humeral circumflex artery. Deltoid muscle, the main muscle in the shoulder is supplied with the axillary nerve.

What is Quadrilateral Space?

The word quadrilateral means a four-sided shape. Quadrilateral space is found on the upper back of the human body, where the shoulder and body meet. Muscles cover three sides of this space and a humerus, the long bone of the upper arm, covers the fourth side. Apart from these muscles, quadrilateral space also houses the axillary nerve and the posterior humeral circumflex artery. This space may close due to the compression of the artery and the nerve that occurs when the arm is in a throwing position. Moreover, a thick band of fibrous tissue present between the muscles of the quadrilateral space may also compress them.

Causes of Quadrilateral Space Syndrome:

  • Overuse and/or repetitive stress are one of the most common causes of this condition. This is seen in athletes who regularly participate in throwing (eg. Baseball pitchers) and swimming.
  • Another common cause of this shoulder condition is a dislocation of the shoulder.
  • A small axillary nerve or extra fibrous tissue bands may also lead to this condition.
  • An injury to the axillary nerve if mild is known as neuropraxia. Because the axillary nerve is short, even recovery from a severe injury is not difficult.
  • People carrying a heavy backpack are also at a higher risk of developing this syndrome as it may injure the axillary nerve.
  • Injury to the back of the shoulder caused by a blunt force may also lead to this condition.

Symptoms of Quadrilateral Space Syndrome:

  • Burning or dull pain in the back of the shoulder especially in the quadrilateral space is the most common symptom.
  • Elevated pain levels of the arm in the throwing position.
  • Numbness and/or tingling in the back of the shoulder and/or in the arm.
  • Fatigue and/or heaviness of the arm.
  • Tenderness in the affected area of the quadrilateral space.
  • Shrinkage of the deltoid muscle.

Diagnosis of Quadrilateral Space Syndrome:

Because shoulder pain could be a result of many other conditions, it is difficult to diagnose this syndrome. A complete medical history and physical examination are usually done. Physical examination comprises of testing and evaluating the shoulder strength, range of motion, and sensation and reflexes.

Also, the physician will ask questions such as regular shoulder related activity, possible physical trauma and the symptoms being experienced.

Some of the diagnostic tools include:

  • Arteriogram – This test involves the usage of a catheter through which a contrast dye is injected. Through “live X-ray” or “fluoroscopy” the distribution of the dye in the injected area is detected. Reduced flow, narrowing of the blood vessel and twisting of the axillary artery are the criteria to confirm the diagnosis.
  • MRI scans – Through this scan the extent of muscle wasting of the deltoid and other muscles involved can be identified. With the help of magnetic waves, bones and tissues in the form of thin slices can be seen.
  • EMG or Electromyelogram – This diagnostic tool is very useful in detecting this syndrome and several other peripheral injuries in the shoulder region. In this procedure, small needle electrodes are inserted into the muscles to check the functioning of the muscles.
  • CTA or Computed Tomography Angiography – Using special X-rays, problems in the arteries and/or veins of the quadrilateral space are identified with this diagnostic tool.
  • Axillary nerve block – In this procedure, an anesthetic such as lidocaine is injected into the axillary nerve area where the symptoms are prominent. If the pain in the injected area reduces rapidly soon after the injection, it is considered a positive diagnosis.

Treatment for Quadrilateral Space Syndrome:

Available treatment options are classified as Non-operative/Non-surgical and Operative/Surgical.

  1. Non-surgical – This option includes resting the shoulder, treating it with hot and/or cold packs, taking non-steroidal anti-inflammatory drugs such as naprosyn and ibuprofen, changing the sport mechanics and undergoing physical therapy. Shoulder stretching exercises and cortisone injections to reduce pain and inflammation in the affected area are suggested.
  2. Surgical – This option is recommended in patients who do not show any improvement after trying out non-surgical options for a period of six weeks.

Decompression is a type of surgery in which the extra band of fibrous tissue in the quadrilateral space, which is responsible for the compression of the axillary nerve, is surgically removed or clipped.

Rarely, during surgery the axillary nerve may get cut or stretched. Injury caused in this way is known as neurotomesis. The injured portion of the nerve is usually repaired by replacing it with a nerve graft. This is done by making a small incision in the back of the shoulder.

Complications After Treatment:

Patients suffering from Quadrilateral Space Syndrome may experience complications after getting treatment in the form of non-surgical or surgical alternatives.

  • Non-surgical complications may include inability to continue the throwing action and constant pain in the shoulder region.
  • Surgical complications may comprise of injury to the axillary nerve, stiffness and inability to return to the previous level of activity i.e.. prior to injury.

Quadrilateral Space Syndrome can be prevented by warming up or stretching the shoulder muscles before practice (for athletes and sports people).

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