Trapezius Triangle Sign

The Trapezius Triangle Sign is a valuable clinical assessment technique for evaluating potential trapezius muscle dysfunction or spinal accessory nerve injury. This distinctive physical examination finding provides important diagnostic information that helps clinicians differentiate between various shoulder pathologies and neural compromises affecting the upper back and shoulder complex.

Anatomical Basis

The trapezius muscle, one of the largest superficial muscles in the posterior thorax, plays a critical role in scapular positioning and shoulder movement. Innervated primarily by the spinal accessory nerve (cranial nerve XI), the trapezius contributes significantly to arm elevation and scapular stabilization during overhead activities. When either the muscle itself or its neural supply becomes compromised, characteristic movement patterns emerge that can be objectively assessed through specialized clinical tests.

See Also: Trapezius Muscle Anatomy

How to Perform the Trapezius Triangle Sign?

The Trapezius Triangle Sign is elicited through a specific testing sequence. The patient is positioned prone on an examination table with both arms initially elevated to approximately 120 degrees. From this position, the patient is instructed to maximally elevate both upper extremities. In normal shoulder function, the patient should achieve full elevation without compensatory movements from other body segments.

However, in the presence of trapezius dysfunction or spinal accessory nerve pathology, the affected side demonstrates a distinctive triangular configuration. This triangular space forms between the patient’s arm, trunk, and the examination table as the individual attempts to compensate for weakness by extending the lumbar spine. This compensatory mechanism creates only an illusion of proper arm elevation while actually revealing the underlying muscular or neural deficit.

Clinical Significance

The severity of trapezius muscle or spinal accessory nerve impairment can be estimated by measuring the angle formed between the patient’s trunk and arm during the test. Typically, in cases of significant pathology, this angle approaches approximately 90 degrees. The examiner must often assist the patient in achieving the starting position, as any additional movement beyond this point would primarily result from spinal extension rather than true scapulothoracic or glenohumeral motion.

This clinical sign carries particular importance in differentiating primary trapezius dysfunction from other shoulder girdle pathologies. For instance, practitioners should note that patients with serratus anterior weakness might also exhibit medial scapular winging during this maneuver, requiring careful assessment to determine the primary source of dysfunction.

Differential Diagnosis

When a positive Trapezius Triangle Sign is observed, clinicians should consider several potential underlying causes:

Spinal accessory nerve injury, which may occur iatrogenically during surgical procedures in the posterior triangle of the neck, represents a common etiology. Traumatic injuries, compression neuropathies, and neuralgic amyotrophy (Parsonage-Turner syndrome) may also present with this clinical finding.

Primary trapezius muscle pathology, including myofascial pain syndrome, strain injuries, or inflammatory myopathies, can similarly produce positive findings during this examination.

The observed movement pattern assists clinicians in distinguishing trapezius dysfunction from other shoulder girdle abnormalities such as rotator cuff pathology, scapular dyskinesis, or thoracic outlet syndrome.

Clinical Applications

Early recognition of trapezius dysfunction through the Trapezius Triangle Sign allows clinicians to implement targeted rehabilitation strategies. These might include trapezius strengthening exercises, scapular stabilization protocols, and neuromuscular reeducation techniques to address the specific deficit.

In cases of suspected spinal accessory nerve injury, prompt identification through this clinical sign can lead to appropriate electrodiagnostic testing (EMG/NCS) to confirm the diagnosis and determine the extent of neural compromise.

For patients undergoing neck dissection procedures or other surgeries with risk to the spinal accessory nerve, pre- and post-operative assessment using the Trapezius Triangle Sign provides valuable objective data regarding functional outcomes and recovery trajectories.

Prognostic Implications

The severity of the Trapezius Triangle Sign correlates with functional limitations in overhead activities, lifting capabilities, and overall shoulder function. Patients with significant positive findings often report difficulty with occupational tasks, recreational activities, and even basic activities of daily living that require arm elevation above shoulder height.

Serial assessment of this clinical sign throughout a rehabilitation program offers objective evidence of progress and functional improvement. As trapezius function recovers, the triangular configuration diminishes, and normal scapulohumeral rhythm gradually returns.

The Trapezius Triangle Sign serves as an essential component of comprehensive shoulder and upper back examination, providing clinicians with valuable insights into neuromuscular function and movement quality. Through careful assessment and interpretation of this distinctive clinical finding, healthcare professionals can develop more precise diagnostic impressions and implement targeted therapeutic interventions for patients with trapezius dysfunction.

Resources

• Magee DJ. Orthopedic Physical Assessment. 7th ed. Elsevier; 2020. https://www.elsevier.com/books/orthopedic-physical-assessment/magee/978-0-323-67262-5
• Petty NJ, Moore AP. Neuromusculoskeletal Examination and Assessment: A Handbook for Therapists. 5th ed. Churchill Livingstone; 2019. https://www.elsevier.com/books/neuromusculoskeletal-examination-and-assessment/petty/978-0-7020-6720-4
• Vastamäki M, Kauppila LI. Etiologic factors in isolated paralysis of the trapezius muscle. Journal of Shoulder and Elbow Surgery. 2016;25(8):e232-e239. https://doi.org/10.1016/j.jse.2016.02.023