Anatomy
Lower Limb
A 19 year old man self presents to the ED following a fight in a nearby street. He has sustained multiple stab wounds and lacerations to the upper thigh and buttocks. Imaging shows an injury to the obturator externus muscle. Which of the following movements is the patient most likely to find difficult:
Answer:
The obturator externus muscle primarily functions to laterally rotate the thigh at the hip joint.Medial Thigh Muscles
Anatomy / Lower Limb / Medial Thigh
Last Updated: 10th April 2019
There are five muscles in the medial compartment of the thigh (adductor longus, adductor brevis, adductor magnus, obturator externus, gracilis), which collectively adduct the thigh at the hip joint.
Table: Function and Innervation of the Medial Thigh Muscles
| Muscle | Function | Innervation |
|---|---|---|
| Adductor longus | Adduction and medial rotation at hip | Obturator nerve |
| Adductor brevis | Adduction at hip | Obturator nerve |
| Adductor magnus | Adduction and medial rotation at hip | Adductor part: Obturator nerve
Hamstring part: Sciatic nerve (tibial division) |
| Obturator externus | Lateral rotation at hip | Obturator nerve |
| Gracilis | Adduction at hip and flexion at knee | Obturator nerve |
Innervation
These muscles are all innervated by the obturator nerve (except for the hamstrings portion of the adductor magnus, innervated by the tibial division of the sciatic nerve).
Function
The adductor longus, brevis, and magnus are the prime adductors of the thigh at the hip joint and also assist in medial rotation.
The obturator externus muscle acts to laterally rotate the thigh at the hip joint.
The gracilis adducts the thigh at the hip joint and flexes the leg at the knee joint.
Testing of the medial thigh muscles can be performed with the patient lying supine and the knee straight. The patient is asked to adduct the thigh against resistance and the strength assessed (if the adductors are normal the proximal ends of the gracilis and adductor longus can easily be palpated).
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/01/Hip-Adductors.jpg)
Medial Thigh Muscles: Obturator Externus (yellow), Adductor Longus (red), Adductor Brevis (green), Adductor Magnus (blue). (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/01/Gracilis-295x1024.jpg)
Gracilis Muscle. (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 |
