Examination of the Shoulder Muscles

Courtesy: Prof Nabil Ebraheim, University of Toledo, USA

Scapular & Shoulder Muscle Examination

Overview

The transcript discusses injuries to several nerves arising from or related to the brachial plexus and the resulting muscle weakness and clinical findings.

The major structures covered are:

• Long thoracic nerve – serratus anterior
• Spinal accessory nerve – trapezius/lateral scapular winging comparison
• Suprascapular nerve – supraspinatus and infraspinatus
• Thoracodorsal nerve  -latissimus dorsi
• Upper and lower subscapular nerves – subscapularis
• Lower subscapular nerve – teres major
• Axillary nerve – teres minor
• Quadrangular space and axillary nerve entrapment

1. Long Thoracic Nerve

Roots

C5, C6, C7

Muscle supplied

Serratus anterior

Injury produces

Medial winging of the scapula

Paralysis of serratus anterior allows the medial border of the scapula to become displaced away from the thoracic cage.

2. Medial Winging of Scapula

Characteristic findings described are:

• Medial border becomes prominent
• Scapula is elevated
• Direction of winging is medial
• Winging becomes more prominent during forward flexion of the arm

Clinical test

Wall push-up test

The patient performs a wall push-up to demonstrate serratus anterior weakness.

Brachial plexus significance

The speaker also states that medial scapular winging may occur as part of a:

Preganglionic / preclavicular brachial plexus injury

3. Medial vs Lateral Scapular Winging

The transcript gives an important comparison.

Feature	Medial winging	Lateral winging
Nerve	Long thoracic	Spinal accessory
Main muscle implicated	Serratus anterior	Not specifically named in this segment
Scapular position	Elevated	Depressed
Direction of winging	Medial	Lateral
Worsened by	Arm flexion	Arm abduction
Relative frequency	More common	Less common
Important history	May occur with brachial plexus injury	Previous posterior-triangle neck surgery

Exam Pearl

Long thoracic – medial winging – flexion worsens it

Accessory nerve – lateral winging – abduction worsens it

4. Suprascapular Nerve

The transcript repeatedly says “subracibular/subracapular,” but the described anatomy clearly corresponds to the suprascapular nerve.

Origin

Upper trunk of brachial plexus

Muscles supplied

• Supraspinatus
• Infraspinatus

5. Course of Suprascapular Nerve

At the suprascapular notch, the transcript describes:

• Suprascapular artery – above transverse scapular ligament
• Suprascapular nerve – below transverse scapular ligament

Memory aid

Artery above, nerve below.

The nerve then continues toward the spinoglenoid notch, giving branches to supraspinatus and infraspinatus.

6. Site of Compression Determines Muscle Involvement

This is one of the most important concepts in the transcript.

Compression at Suprascapular Notch

A proximal compression affects:

• Supraspinatus
• Infraspinatus

Resulting in:

• Decreased shoulder abduction
• Loss/weakness of external rotation with the arm by the side

Compression at Spinoglenoid Notch

A more distal compression affects:

Infraspinatus only

Therefore:

Loss/weakness of external rotation

without the proximal supraspinatus involvement described above.

High-Yield Localization

Compression site	Muscle involvement
Suprascapular notch	Supraspinatus + infraspinatus
Spinoglenoid notch	Infraspinatus only

7. Spinoglenoid Notch Compression

The speaker associates spinoglenoid notch compression with:

• Volleyball players
• Ganglion cyst
• SLAP tear

The important functional consequence is infraspinatus weakness.

The speaker describes infraspinatus as the:

Primary external rotator when the arm is by the side.

8. Thoracodorsal Nerve

Muscle supplied

Latissimus dorsi

The transcript describes latissimus dorsi as a broad muscle of the back, partially covered by trapezius.

Roots stated

C6, C7, C8

Origin of nerve

Posterior cord

The thoracodorsal nerve is described as arising between the upper and lower subscapular nerves.

9. Testing Latissimus Dorsi

The transcript describes testing the muscle against resistance so that its muscle belly can be:

• Seen
• Palpated

The exact movement is transcribed as “abduction,” but this should be treated cautiously because the supplied source does not clearly preserve the intended maneuver.

10. Subscapularis

Nerve supply

Upper and lower subscapular nerves

Origin of nerves

Posterior cord of brachial plexus

Roots stated

C5, C6, C7

The transcript gives three clinical tests for subscapularis:

1. Lift-off test
2. Lift-off lag test
3. Belly-press test

11. Lift-Off Test

Technique

• Place hand behind the lower back.
• Ask patient to actively lift the hand away from the back.

Positive test

Inability to lift the hand away from the lower back.

This indicates subscapularis weakness and raises suspicion of a subscapularis tendon tear.

12. Lift-Off Lag Test

Technique

• Examiner passively holds the patient’s hand away from the lumbar region.
• Examiner releases the hand.
• Patient attempts to maintain the position.

Positive test

Patient cannot keep the hand away from the back.

This suggests subscapularis tendon dysfunction/tear.

13. Belly-Press Test

Technique

• Patient presses palm against abdomen.
• Wrist should remain in a neutral position.

Positive test

The patient cannot maintain the maneuver without:

• Flexing the wrist, and/or
• Allowing the elbow to fall posteriorly

This indicates subscapularis dysfunction.

14. Teres Major

The transcript’s “tis measure/the major” corresponds to teres major.

Nerve supply

Lower subscapular nerve

The lower subscapular nerve arises from the:

Posterior cord

Examination

The speaker describes testing the muscle against resistance while observing and palpating its muscle belly.

The precise movement is not sufficiently clear in the transcript to reconstruct beyond this.

15. Posterior Shoulder Anatomical Spaces

The lecture then uses teres major and teres minor to introduce the important spaces in the posterior shoulder.

It mentions:

• Quadrangular space
• Triangular space
• Triangular interval

The quadrangular space lies between the teres major and teres minor region.

16. Quadrangular Space

Structures specifically mentioned within the quadrangular space are:

• Axillary nerve
• Posterior humeral circumflex artery

Clinical implication

Vague posterior shoulder pain in this region may indicate:

Axillary nerve entrapment in the quadrangular space

17. Teres Minor

Anatomy stated

Teres minor is described as a narrow muscle arising from the posterolateral scapula and inserting onto the:

Greater tuberosity of the humerus

Nerve supply

Posterior branch of the axillary nerve

The transcript also notes that the axillary nerve provides cutaneous innervation to the lateral shoulder region.

18. Infraspinatus vs Teres Minor

The transcript makes a clinically useful distinction according to arm position.

Position	Main external rotator emphasized
Arm by the side	Infraspinatus
Arm abducted	Teres minor

This distinction forms the basis of the clinical testing described.

19. Hornblower’s Test

Used to assess:

Teres minor strength

Technique

1. Patient and examiner standing.
2. Elevate arm to approximately 90°.
3. Flex elbow to 90°.
4. Ask patient to externally/laterally rotate the shoulder.
5. Apply resistance.

Positive test

Weakness and/or pain with resisted external rotation

suggests teres minor dysfunction.

High-Yield Nerve–Muscle–Clinical Finding Table

Nerve	Origin/roots stated	Muscle	Important finding/test
Long thoracic	C5–C7	Serratus anterior	Medial winging; wall push-up
Suprascapular	Upper trunk	Supraspinatus + infraspinatus	Abduction + ER weakness
Thoracodorsal	Posterior cord; C6–C8 stated	Latissimus dorsi	Resisted muscle testing
Upper/lower subscapular	Posterior cord; C5–C7 stated	Subscapularis	Lift-off, lag, belly press
Lower subscapular	Posterior cord	Teres major	Resisted testing
Axillary – posterior branch	—	Teres minor	Hornblower’s test

Localization Pearls

Scapular winging

Medial winging
– Long thoracic nerve
– Serratus anterior
– Worse with forward flexion
– Wall push-up

Lateral winging
– Spinal accessory nerve
– Worse with abduction
– Consider previous posterior-triangle neck surgery

Suprascapular nerve

Suprascapular notch lesion
– Supraspinatus + infraspinatus
– Abduction + external rotation affected

Spinoglenoid notch lesion
– Infraspinatus only
– External rotation affected

Posterior shoulder

Quadrangular space
– Axillary nerve + posterior humeral circumflex artery
– Entrapment may produce posterior shoulder symptoms

Key Take-Home Points

• Long thoracic nerve = C5–C7 – serratus anterior – medial scapular winging.
• Medial winging is demonstrated with a wall push-up and worsens with arm flexion.
• Lateral winging is associated with spinal accessory nerve injury and may follow posterior-triangle neck surgery.
• Suprascapular nerve arises from the upper trunk and supplies supraspinatus and infraspinatus.
• At the suprascapular notch: artery above, nerve below the transverse scapular ligament.
• Suprascapular notch compression – supraspinatus + infraspinatus.
• Spinoglenoid notch compression – isolated infraspinatus involvement.
• Thoracodorsal nerve supplies latissimus dorsi.
• Upper and lower subscapular nerves supply subscapularis.
• Subscapularis is assessed with lift-off, lift-off lag and belly-press tests.
• Lower subscapular nerve supplies teres major.
• Posterior branch of axillary nerve supplies teres minor.
• Hornblower’s test – teres minor.
• Quadrangular space – axillary nerve + posterior humeral circumflex artery.

Exam Pearls

Long thoracic – Serratus anterior – Medial winging

Accessory nerve – Lateral winging

Suprascapular notch – Supra + Infra

Spinoglenoid notch – Infra only

Subscapularis – Lift-off + Belly press

Teres major – Lower subscapular nerve

Teres minor – Axillary nerve – Hornblower

Infraspinatus – ER with arm by side

Teres minor – ER with arm abducted