Anatomy
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Upper Limb
A patient presents with carpal tunnel syndrome. Which of the following is the most lateral structure in the carpal tunnel:
Answer:
The following structures pass through the carpal tunnel:- the four tendons of the flexor digitorum profundus (FDP)
- the four tendons of the flexor digitorum superficialis (FDS)
- the tendon of the flexor pollicis longus (FPL)
- the median nerve.
Carpal Tunnel
Anatomy / Upper Limb / Wrist and Hand
Last Updated: 10th April 2019
Table: Anatomical Boundaries and Contents of the Carpal Tunnel
| Anatomical Boundaries | Structure(s) |
|---|---|
| Roof | Flexor retinaculum |
| Carpal arch | Pisiform and hook of the hamate medially, tubercles of the scaphoid and trapezium laterally |
| Contents | Four tendons of flexor digitorum profundus, four tendons of flexor digitorum superficialis, tendon of flexor pollicis longus, median nerve |
Anatomical Boundaries
The carpal tunnel is formed by a deep carpal arch and a superficial flexor retinaculum.
The base of the carpal tunnel is formed medially by the pisiform and the hook of the hamate and laterally by the tubercles of the scaphoid and trapezium.
The flexor retinaculum is a thickened band of fibrous connective tissue on the volar aspect of the hand, which bridges the gap between these carpal bones and forms the roof of the carpal tunnel.
Contents
The following structures pass through the carpal tunnel:
- the four tendons of the flexor digitorum profundus (FDP)
- the four tendons of the flexor digitorum superficialis (FDS)
- the tendon of the flexor pollicis longus (FPL)
- the median nerve.
Free movement of the tendons in the carpal tunnel is facilitated by synovial sheaths, which surround the tendons. All of the tendons of the FDP and FDS are contained within a single synovial sheath with a separate sheath enclosing the tendon of the FPL. The median nerve lies anterior to the tendons in the carpal tunnel.
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/01/Carpal-Tunnel-3-Large-1-1024x576.jpg)
Carpal Tunnel. (Image modified by FRCEM Success. Original 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 |
