Anatomy
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Thorax
A 47 year old presents to ED complaining of left hand pain. She has recently fractured her left clavicle which was treated conservatively. On examination her left hand is cold and pale and you cannot palpate a pulse at the wrist. Which of the following structures has most likely been affected:
Answer:
The patient most likely has arterial thoracic outlet syndrome due to compression of the left subclavian artery at the thoracic inlet secondary to the clavicle fracture.Thoracic Inlet
Anatomy / Thorax / Thoracic Inlet
Last Updated: 27th February 2020
The thoracic inlet is bordered anteriorly by the manubrium of the sternum and the first costal cartilages, laterally by the first ribs and posteriorly by the body of vertebra T1.
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/01/Thoracic-inlet.png)
Thoracic Inlet. (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
At the thoracic inlet, the superior aspects of the pleural cavities lie on either side of the entrance to the mediastinum, extending approximately 2 - 3 cm above rib I and the costal cartilage into the neck.
Relations of Key Structures
The thoracic inlet is traversed in the median plane by (from anterior to posterior):
- the sternohyoid muscle
- the sternothyroid muscle
- the thymic remnants
- the inferior thyroid veins
- the trachea
- the recurrent laryngeal nerves (in the tracheo-oesophageal sulcus)
- the oesophagus
- the thoracic duct (displaced slightly to the left)
- the longus colli muscles
- the anterior longitudinal ligament.
To the left, it is traversed by (from anterior to posterior):
- the left brachiocephalic vein
- the left vagus and left phrenic nerves
- the left common carotid artery and the left subclavian artery.
To the right, it is traversed by (from anterior to posterior):
- the right brachiocephalic vein
- the right vagus and right phrenic nerves
- the brachiocephalic trunk.
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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 |
