Quadrilateral Space Syndrome

Topic updated on 12/19/14 3:39pm
  • Axillary nerve and posterior humeral circumflex artery compression in the quadrilateral (quadrangular) space  
  • Epidemiology
    • incidence
      • rare and often misdiagnosed as subacromial impingement
    • demographics
      • 20-40 years old
    • location
      • most commonly affects the dominant shoulder
    • risk factors
      • overhead movement athletes (e.g. basketball)
      • contact or throwing sports
  • Pathophysiology
    • mechanism of injury
      • compression and reduction of quadrangular space due to
        • iatrogenic (tight fibrous bands, muscular hypertrophy)
        • paralabral cysts (most commonly inferior labral tears)
        • trauma (scapular fracture, shoulder dislocation)
        • benign or malignant masses
    • pathomechanics
      • greatest amount of compression occurs when the arm is positioned in the late cocking phase of throwing (abduction and external rotation)
  • Prognosis
    • long-standing cases often causes atrophy/weakness of teres minor and deltoid 
  • Quadrangular space
    • location 
      • lateral to triangular space and medial to triangular interval 
    • boundaries
      • superior - subscapularis and teres minor
      • inferior - teres major
      • medial - long head of triceps brachii
      • lateral - surgical neck of the humerus
    • contents
      • axillary nerve (C5 nerve root, posterior cord) 
      • posterior circumflex humeral artery
  • Symptoms
    • poorly localized pain of the posterior/lateral shoulder
      • often worse at night
      • worse with overhead activity or late cocking/acceleration phase of throwing 
    • non-dermatomal distribution of paraesthesia along the lateral shoulder and arm
    • shoulder external rotation weakness
  • Physical examination
    • inspection
      • may see atrophy of the teres minor and deltoid
    • palpation
      • point tenderness over the quadrangular space
    • motion and strength
      • external rotation weakness with the arm abducted in throwing position
      • pain exacerbated by active and resisted abduction and external rotation of the arm
    • neurological examination
      • usually normal
      • have mild sensory changes in the axillary nerve distribution
  • Radiographs
    • recommended views
      • shoulder series (AP, lateral, axillary views)
    • findings
      • usually normal
      • used to rule out pathologic entities
  • MRI
    • indications
      • often used to rule out rotator cuff pathology
    • findings
      • may show atrophy of teres minor (axillary innervation) q
      • may show compression of the quadrilateral space  
      • may show inferior paralabral cyst associated with labral tear 
  • Arteriogram
    • may shows lesion in posterior humeral circumflex artery
  • EMG
    • indications
      • used to confirm diagnosis
    • findings
      • will show axillary nerve involvement
  • Nonoperative
    • NSAIDS, activity restriction, physiotherapy
      • indications
        • first line of treatment 
      • techniques
        • glenohumeral joint mobilization and strengthening
        • posterior capsule stretching
        • massage
      • outcomes
        • most people improve with 3-6 months of nonoperative treatment
    • diagnostic lidocaine block 
      • indications
        • will help to confirm diagnosis
      • technique
        • inject plain lidocaine directly into the quadrilateral space 
        • starting point is 2 to 3 cm inferior to the standard posterior shoulder arthroscopy portal
      • outcomes
        • positive if no point tenderness or pain with full ROM of the shoulder following injection
  • Operative
    • nerve decompression
      • indications
        • failure of nonoperative management 
        • significant weakness and functional disability
        • decompression of space-occupying lesion
      • techniques
        • open release of quadrilateral space +/- arthroscopic repair of labral tear
Surgical Techniques
  • Open Quadrilateral Space Decompression
    • approach
      • lateral decubitus position
      • 3 - 4 cm incision over the quadrilateral space
      • identify posterior border of deltoid and reflect superolateral
      • expose fat in quadrilateral space between teres minor and teres major
    • technique 
      • identify the axillary nerve by using the humeral neck as reference
      • avoid cutting the posterior circumflex artery
      • free any fibrous lesions adhering to the nerve
      • ensure the nerve is completely free of compression by moving the arm into abduction and external rotation 
    • postoperative care
      • immediate sling for comfort
      • early pendulum exercises to avoid new adhesions
      • progress to full active ROM with supervised physiotherapy


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Qbank (3 Questions)

(OBQ10.233) A 24-year-old patient complains of vague right shoulder pain. On physical exam the patient is noted to have weakness with external rotation. EMG findings are consistent with quadrilateral space syndrome. Along with the deltoid, what other muscle is affected? Topic Review Topic

1. Teres major
2. Teres minor
3. Pectoralis major
4. Supraspinatus
5. Subscapularis

(OBQ09.72) A professional baseball pitcher develops shoulder pain, weakness and lateral arm paresthesias in his throwing arm. Selected MRI images of the right shoulder are shown in Figures A and B. What is the diagnosis? Topic Review Topic
FIGURES: A   B        

1. Parsonage-Turner syndrome
2. Long thoracic neuritis
3. Quadrilateral space syndrome
4. Internal impingement
5. External impingement

(OBQ08.133) An MRI of the shoulder in a patient with chronic quadrilateral space syndrome is most likely to show which of the following? Topic Review Topic

1. Increased intra-capsular volume
2. Loss of intra-capsular volume
3. Fatty atrophy of the infraspinatus
4. Fatty atrophy of the teres minor
5. Fatty atrophy of the latissimus dorsi



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