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Describe the deep fascia with its modifications and functions. Add a note on compartment syndrome.

Anatomy · 1st Professional — Pre-Clinical

Deep fascia is a dense, inelastic sheet of fibrous connective tissue that invests the muscles and deeper structures of the body.

Contains no fat, unlike the superficial fascia
Absent over the face, external ear, penis and scrotum — where mobility of skin matters more than restraint

Modification	Description	Examples
Intermuscular septa	Extend from the fascia to bone, dividing the limb into compartments	Medial and lateral septa of the arm and thigh
Retinacula	Thickened bands holding tendons close to the bone	Flexor and extensor retinacula of the wrist and ankle
Sheaths	Tubular investments of vessels and nerves	Carotid sheath, axillary sheath, femoral sheath
Aponeuroses	Flattened tendons of insertion	Palmar and plantar aponeuroses, bicipital aponeurosis
Pulleys	Redirect the line of pull of a tendon	Trochlea for superior oblique; flexor pulleys of the fingers
Interosseous membrane	Between two bones	Radio-ulnar and tibiofibular; also a syndesmosis

Confines muscles into compartments, so contraction is efficient and directed
Provides additional attachment for muscle fibres
Assists venous and lymphatic return — the "muscle pump" works because the fascia is inelastic, so contraction compresses the deep veins
Holds tendons in position and prevents bowstringing
Forms a barrier limiting the spread of infection, and directs it along defined planes
Maintains the shape of the limb; carries proprioceptive nerve endings

Fascia	Region	Note
Fascia lata	Thigh	Thickened laterally as the iliotibial tract; has the saphenous opening
Clavipectoral fascia	Pectoral region	Encloses subclavius and pectoralis minor
Thoracolumbar fascia	Back	Gives origin to latissimus dorsi and transversus abdominis
Pretracheal and prevertebral fascia	Neck	Define the deep cervical spaces
Bucco-pharyngeal fascia	Pharynx	Retropharyngeal space lies behind it
Cribriform fascia	Saphenous opening	Pierced by the great saphenous vein and lymphatics

The cardinal sign is pain out of proportion to the injury, worsened by passive stretch of the muscles
Peripheral pulses are usually present — the pressure needed to stop capillary flow is far below systolic; a palpable pulse never excludes it
The other features — paraesthesia, pallor, paralysis, pulselessness — are late and unreliable
Treatment is urgent fasciotomy, dividing the deep fascia along the length of the compartment

Volkmann ischaemic contracture is the end result of an untreated compartment syndrome in the forearm, classically after a supracondylar fracture

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