PHALANGES OF THE FOOT

The phalanges are the long bones in the foot, distal to the metatarsals. The phalanges of the foot resemble that of the hand, but these are smaller in size & shafts particularly of proximal row are compressed from side to side. They are named as proximal, middle and distal phalanges; there are 2 in the great toe, 3 in all the other toes (but there can be only 2 phalanges in the little toe), hence there are 14 phalanges in total. The phalanges consist pf proximal base, shaft & distal head.

PROXIMAL PHALANGES

The proximal phalanges have a compressed shaft which is convex dorsally (above) & on the plantar side (below) is concave. The base is concave to articulate with the head of the associated metatarsals and forms the metatarsophalangeal joint. The head presents a trochlear surface to articulate the middle phalanx to form the interphalangeal joint.

MIDDLE PHALANGES

The middle phalanges are smaller than the proximal phalanges but, larger than the distal phalanges. The base forms proximal interphalangeal joint with proximal phalanges. The head forms distal interphalangeal joint which is a type of hinge joint forms with distal phalanges. The hinge joint allows flexion & extension movement which are provided by the plantar ligaments & also by medial and lateral collateral ligaments.

DISTAL PHALANGES

The distal phalanges are flat and small. They have a broad base to articulate the middle phalanges. The head is nonarticular & expanded. It has a rough and crescent shaped tuberosity present on the plantar surface of the head to support pads or pulp of the bone which is a weight bearing area.

MUSCLE ATTACHMENTS

The proximal phalanges have attachments of; lumbricals on the medial aspect of the 4 lateral phalanges and interossei on both the sides of 2^nd,3^rd & 4^th phalanges. The plantar interossei attaches on the medial side & on the lateral side there is attachment to abductor digiti minimi & flexor digiti minimi on the little toe. On the great toe there is attachment of abductor hallucis on the medial side and adductor hallucis on the lateral side.

The middle phalanges have attachments of flexor digitorum brevis on both the sides of the shaft at the plantar surface. On the dorsal side of the shaft there is attachment of extensor expansion. The fibrous flexor sheath is attached to the margins of proximal and middle phalanges of lateral 4 toes.

The distal phalanges have attachments of flexor digital longus and extensor digitorum longus on plantar and dorsal aspects respectively on the lateral four toes. Flexor hallucis longus and extensor hallucis longus are attached to plantar and dorsal surface respectively at the great toe.

VASCULAR & NERVOUS SUPPLY

The proximal phalanges get blood supply from the dorsal digital arteries. The middle phalanges are supplied by the dorsal and plantar digital arteries. The distal phalanges get blood supply from plantar digital arteries. All the phalanges are innervated by dorsal and plantar digital nerves.

OSSIFICATION

Ossification is the process of bone formation where cartilage is replaced by bone tissue through the activity of osteoblasts.

Each phalanx begins as a cartilaginous model and develops from a primary ossification center in the shaft. A secondary ossification center forms in the base.

Distal phalanges: Primary ossification centers appear between the 9th and 12th prenatal weeks. The secondary ossification center appears around the sixth year and fuses with the shaft by the eighteenth year.

Proximal phalanges: Primary ossification centers appear between the 11th and 15th prenatal weeks. The secondary ossification center appears around the second year and fuses with the shaft by the eighteenth year.

Middle phalanges: Primary ossification centers appear slightly later than the proximal phalanges. The secondary ossification center appears around the third year and fuses with the shaft by the eighteenth year.