What is Quadrangular Space Syndrome
Quadrangular space syndrome (QSS) arises from compression or mechanical injury to the axillary nerve (neurogenic quadrilateral space syndrome [nQSS]) and/or posterior circumflex humeral artery (PCHA) (vascular quadrilateral space syndrome [vQSS]) as they pass through the quadrilateral space (QS). The QS is bounded by the edge of the long head of the triceps medially, the medial edge of the surgical neck of the humerus laterally, the tendon of the teres major and latissimus dorsi muscles inferiorly, and the teres minor muscle or the scapulohumeral capsule superiorly (Brown et al. 2015).
Anatomy of The Quadrangular Space
What Causes Quadrangular Space Syndrome
Teres minor atrophy occurs either in isolation, associated with other rotator cuff muscle pathologies or in quadrilateral space syndrome. In the latter condition, compression of the axillary nerve is the likely cause; however, the anatomy of the nerve to teres minor and how this may relate to isolated teres minor atrophy have not been extensively investigated (Friend et al. 2010).
Anatomy of The Axillary Nerve
The axillary nerve has one main trunk before giving off the superolateral brachial cutaneous sensory branch and a branch to the teres minor, then continuing to supply the whole deltoid. More recently, The axillary nerve as possessing two posterior branches, one supplying the teres minor then continuing to become the superolateral brachial cutaneous nerve while the other supplies the posterior aspect of the deltoid muscle (Friend et al. 2010).
These variations in length correlated to the position of the bifurcation into anterior or posterior branches, namely specimens bifurcating earlier had a shorter axillary nerve trunk and a longer posterior branch of the axillary nerve. The course of the anterior branch within the deltoid muscle which supplies this muscle, the joint capsule and the skin (Friend et al. 2010).
The position of the axillary nerve bifurcation into anterior and posterior branches can vary, so It is feasible that such variations may alter the risk of nerve compression in the quadrilateral space (Friend et al. 2010).
Axillary Nerve Injury
Mechanism of Injury in Neural QSS
The neural QSS can also result from hypertrophy of the muscular boundaries, an atypical nerve course, bone spikes, or space-occupying lesions, such as glenoid labral cysts, paralabral cysts, ganglia, fracture hematoma, or humeral osteochondroma. Chronic fixed nerve compression permanently displaces internal nerve contents in transverse and longitudinal dimensions, leading to long-term damage of axons and myelin (Brown et al. 2015).
SIgns and Symptoms of Quadrangular Space Sydrome
Patients with QSS manifest with various symptoms. Neurogenic manifestations may include nondermatomal neuropathic pain, numbness, and weakness in the shoulder (usually posterior), often radiating down the arm. Vascular manifestations may include thrombosis, microembolism or macroembolism, digital or hand ischemia, and the full spectrum of signs and symptoms associated with acute ischemia such as pain, pallor, and absent pulses (Brown et al. 2015).
Signs and Symptoms of Vascular QSS
Vessel thrombosis and distal embolization can present with coolness, cold intolerance, pallor, and cyanosis of the upper extremity digit, with or without splinter hemorrhages (Brown et al. 2015).
Differential Diagnosis of Neural QSS
A differential diagnosis forNeural QSS includes suprascapular nerve entrapment and complex regional pain syndrome, overt shoulder trauma and iatrogenesis. C5 and/or C6 radiculopathy should also be ruled out, as found in the case of patient . Axillary nerve pathology can overlap with C5/C6 radiculopathy because the axillary nerve arises from the C5 and C6 nerve root (Brown et al. 2015).
Mechanism of Posterior Circumflex Humeral Artery (PCHA) Injury (Vascular QSS)
The mechanism of thrombosis of the PCHA in Vascular QSS involves repetitive trauma to the PCHA wall during AER. This is caused as a repetitive tension effect that stretches the PCHA as it travels through the tight QS and winds around the neck of the humerus, analogous to a taut stretched rubber band leading to intimal injury and weakening of the vessel wall. The repetitive pulley movement could lead to turbulent blood flow within the PCHA (Brown et al. 2015).
Signs and Symptoms of Vascular QSS
Vessel thrombosis and distal embolization can present with coolness, cold intolerance, pallor, and cyanosis of the upper extremity digit, with or without splinter hemorrhages (Brown et al. 2015)
Differential Diagnosis of Vascular QSS
Quadrilateral space syndrome can mimic a number of other neurovascular disorders, including those that involve thrombosis or aneurysm formation in other more proximal branches of the axillary artery, such as in arterial Thoracic Outlet Syndrome (TOS). In arterial TOS, the subclavian artery is compressed between the clavicle and the first rib or anatomic abnormalities such as a cervical rib or fibrous band (Brown et al. 2015).
Osteopathic Treatment of Quadrangular Space Syndrome
First of all manual therapy therapy approach (Osteopathy) is most likely not suitable for vascular QSS and for Neural QSS caused by an atypical nerve course, bone spikes, or space-occupying lesions, such as glenoid labral cysts, paralabral cysts, ganglia, fracture hematoma, or humeral osteochondroma, as discussed previously. These causes are likely to require a surgical intervention.
The Osteopathic treatment is focused on the hypertrophy of the muscular boundaries of the Quadrangular space Where both or either teres minor or triceps brachii are impinging the axillary nerve and increasing the mobility of the Glenohumeral Joint.
When to Refer
At least six months of conservative management is recommended before surgical intervention is performed.During this six-month period, treatment should include NSAIDs, therapeutic exercise, manual therapy, and restriction of activities that produce symptoms. Glenohumeral joint mobilization, rotator cuff and scapular strengthening, cross-friction massage, and posterior capsule stretching have been found to provide beneficial effects (Manske et al 2009). This could be performed by an Osteopath
Effectiveness of Osteopathic Treatment
The posterior capsule should be addressed as part of the cause of a dysfunctional arthrokinematic pattern of motion. A treatment plan to address this consideration may include posterior and inferior glide joint mobilization techniques. Stretching into horizontal adduction has also been reported to provide benefit. The findings of a recently reported randomized clinical trial suggest that a combination of posterior capsule stretching and posterior capsule joint mobilization produces better results than stretching alone
Fibrous bands and adhesions can form along the posterior band of the inferior glenohumeral ligament, which may produce symptoms associated with QSS. Friction massage and soft tissue mobilization can be applied to the area around the axillary nerve within the quadrilateral space, which has been reported to provide great benefit.
Both muscles could be treated with passive stretching of the shoulder in flexion and abduction reinforced with a finger/thumb/hand contact over the muscles to create a false insertion, temporarily. Alternative massage techniques to these muscles to may reduce the hypertrophy.
Evidence Base for Osteopathic treatment of Quadrangular Space Syndrome
Unfortunately, there is very little manual therapy evidence available for the treatment of Quadrangular Space Syndrome. For the purpose of this article, a boolean search had been performed on Google Scholar and Pubmed. Other databases could have been searched, however articles are more freely available on Google Scholar and Pubmed. There is currently a growing evidence available for manual therapy, there will evidence available in the future.
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Brown SA, Doolittle DA, Bohanon CJ, Jayaraj A, Naidu SG, Huettl EA, Renfree KJ, Oderich GS, Bjarnason H, Gloviczki P, Wysokinski WE, McPhail IR (2015). Quadrilateral space syndrome: the Mayo Clinic experience with a new classification system and case series. Mayo Clin Proc. Mar;90(3): 382-94
Friend J, Francis S, McCulloch J, Ecker J, Breidahl W, McMenamin P (2010). Teres minor innervation in the context of isolated muscle atrophy. Surg Radiol Anat. Mar;32(3): 243-9
Manske RC, Sumler A, ATC, and Runge J (2009). Quadrilateral Space Syndrome. FUNCTIONAL REHABILITATION ATT 14(2), pp. 45-47