Anatomy
Lower Limb
A 21 year old gang member presents to ED having been shot in the foot. Imaging shows severe damage to the base of the fifth metatarsal with damage to the muscle tendon attached here. Which of the following movements would you most expect to be affected:
Answer:
The fibularis brevis muscle tendon attaches distally to a tubercle on the lateral surface of the base of the 5th metatarsal. Damage to this muscle will result in weakened eversion of the foot. (N.B. the fibularis tertius muscle tendon also attaches to the dorsal aspect of the fifth metatarsal - this muscle also acts to evert the foot, and assists very weakly with dorsiflexion).Lateral Leg Muscles
Anatomy / Lower Limb / Lateral Leg
Last Updated: 31st May 2023
Table: Function and Innervation of the Lateral Leg Muscles
| Muscle | Function | Innervation | Distal Attachment |
|---|---|---|---|
| Fibularis longus | Plantarflexion and eversion of foot, support of lateral and transverse arches | Superficial fibular nerve | 1st metatarsal and medial cuneiform |
| Fibularis brevis | Eversion of foot | Superficial fibular nerve | 5th metatarsal |
Function
The fibularis longus and brevis act together to evert the foot. The fibularis longus also assists in plantarflexion of the foot and supports the arches of the foot (mainly the lateral and transverse arches).
Innervation
Both the fibularis longus and brevis are innervated by the superficial fibular nerve.
Attachments
Both tendons of the fibularis longus and brevis pass posterior to the lateral malleolus in a shallow bony groove before swinging forward to enter the lateral side of the foot. The fibularis brevis then curves forward across the lateral surface of the calcaneus to attach to a tubercle on the lateral surface of the base of the 5th metatarsal. The fibularis longus descends obliquely down the lateral side of the foot before swinging under the foot to cross the sole and attach to the inferior surfaces of the base of the 1st metatarsal and the medial cuneiform bones.
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/01/Lateral-Leg.jpg)
Lateral Leg Muscles: Fibularis Longus (red), Fibularis Brevis (green). (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 |
