Anatomy
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Upper Limb
Your consultant performs a thorough shoulder examination on a patient with suspected rotator cuff injury on his left side. He asks the patient to position his left arm in full medial rotation with the dorsum of his hand on the lower back. He then asks the patient to lift his hand away from his back against resistance. Which of the following muscles is being assessed:
Answer:
This is the lift-off test used to assess the subscapularis muscle. The test is positive if the patient has pain or weakness.Rotator Cuff Muscles
Anatomy / Upper Limb / Shoulder
Last Updated: 20th February 2019
The rotator cuff is a common name for the group of four distinct muscles and their tendons that provide strength and stability during motion of the shoulder. They are also referred to as the SITS muscle with reference to the first letter of their names:
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
Table: Function and Assessment of the Rotator Cuff Muscles
| Muscle (Innervation) | Function | Assessment |
|---|---|---|
| Supraspinatus (suprascapular nerve) | Initiation of abduction of arm to 15 degrees at glenohumeral joint | Empty Can Test: Position the patient with arms elevated to 90 degrees in the scapular plane, with the elbow extended, and full medial rotation and pronation of the forearm with thumbs pointing downwards. Ask the patient to resist the downward force being applied to the forearm. Test is positive if patient has pain or weakness. |
| Infraspinatus (suprascapular nerve) | Lateral rotation of arm at glenohumeral joint | Infraspinatus Test: Position the patient with the arm fully adducted, with the elbow flexed to 90 degrees. Ask the patient to resist the medially directed force being applied to the arm. Test is positive if patient has pain or weakness. |
| Teres minor (axillary nerve) | Lateral rotation of arm at glenohumeral joint | Hornblower’s Test: Position the patient with the arm elevated to 90 degrees in the scapular plane and the elbow flexed to 90 degrees. Ask the patient to laterally rotate the arm against resistance. Test is positive if patient has pain or weakness. |
| Subscapularis (subscapular nerves) | Medial rotation of arm at glenohumeral joint | Lift-off Test: Position the patient in full medial rotation with the dorsum of the hand on the lower back. Ask the patient to lift their hand away from their back against resistance. Test is positive if patient has pain or weakness. |
![By Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/12/Rotator-Cuff.png)
Rotator Cuff Muscles. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
