Anatomy
Lower Limb
A patient receives a deep laceration to his left leg while trying to escape an angry farmer through a barbed-wire fence. He is unable to dorsiflex his foot. Sensation is normal over the dorsum of the foot. Which of the following nerves has most likely been injured:
Answer:
The deep fibular nerve innervates the muscles in the anterior compartment of the leg which are responsible for dorsiflexion of the foot and extension of the toes. Sensation to the dorsum of the foot is most supplied by the superficial fibular nerve (except for the webspace between the 1st and 2nd toes, which is supplied by the deep fibular nerve).Deep Fibular Nerve
Anatomy / Lower Limb / Anterior Leg / Innervation of Lower Limb
Last Updated: 6th December 2020
The deep fibular nerve is a branch of the common fibular nerve.
Table: Anatomical Overview of the Deep Fibular Nerve
| Nerve | Deep Fibular |
|---|---|
| Nerve roots | L4 -L5 |
| Motor supply | Anterior compartment of leg |
| Sensory supply | Webspace between 1st and 2nd toes |
| Injury | Motor Loss: Loss of dorsiflexion of ankle and extension of toes, foot drop with high-stepping gait, weakness of foot inversion
Sensory Loss: Loss of sensation over webspace between 1st and 2nd toes |
Anatomical Course
Deep Fibular Nerve. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Function
It innervates the anterior leg (tibialis anterior, extensor hallucis longus, extensor digitorum longus, fibularis tertius) and the dorsal intrinsic muscles of the foot. It supplies skin over the webspace between the 1st and 2nd toes.
Table: Motor Supply of the Deep Fibular Nerve
| Muscle | Function |
|---|---|
| Tibialis anterior | Dorsiflexion and inversion of foot, support of medial arch of foot |
| Extensor hallucis longus | Extension of great toe and dorsiflexion of foot |
| Extensor digitorum longus | Extension of lateral four toes and dorsiflexion of foot |
| Fibularis tertius | Dorsiflexion and eversion of foot |
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/01/Cutaneous-Innervation-Leg.png)
Cutaneous Innervation of Lower Limb. (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 |
