anatomy and biomechanics of foot

ANATOMY AND BIOMECHANICS OF FOOT

Presenter : Dr. SYED IMRAN

Chair person : Dr. RUPAKUMAR C.S.

Dr. SRINIVAS DEEP URS

INTRODUCTION The human foot is a complex structure

adapted to allow orthograde foot stance and locomotion.

It is the only part which is in regular contact with the ground.

ANATOMY :

1) Bones2) Joints3) Ligaments4) Arches5) Muscles

TARSUS Seven tarsal bones Larger to support and distribute weight Tarsus and metatarsus arranged to

form intersecting longitudinal and transverse arches.

TALUS Link between foot and leg through

ankle joint. Head : Directed distally and inferomedially Long axis is inclined inferomedially to

articulate with proximal navicular surface

Plantar surface has 3 articular areas

TALUS

The most posterior is largest,slightly convex and rests on a shelf like medial projection,the sustentaculum tali.

Neck : Constricted part Long axis is directed downwards,

forwards, medially. Neck-body angle is 150

Body Cuboidal and has five surfaces Superior surface : Articulates with tibia Wider anteriorly than posteriorly Inferior surface : Articulates with calcaneum Medial surface : Articulates with M.malleoli Lateral surface : Articulates with L.malleoli Posterior surface : Small

VASCULAR SUPPLY :

Tenous due to lack of muscle attachments

Extra-osseus supply from posterior tibial,doraslis pedis, peroneal Arteries.

A of tarsal canal anastomose with A of tarsal sinus to form a vascular sling under talar neck.

a- Laterally A of tarsal sinus b- A of tarsal canal c- Deltoid branches

ATTACHMENTS ON TALUS

Neck : Capsular ligament of ankle joint, dorsal talonavicular ligament.

Lower non-articular part gives attachment to deep fibers of deltoid ligament.

CALCANEUM Largest tarsal bone Projects posterior to tibia and fibula to act as a short lever for calf muscles. Six surfaces Vascular Supply : Medial and lateral calcaneal Arteries

ATTACHMENTS ON CALCANEUM : Middle rough area on posterior surface

receives insertion of tendocalcaneus and plantaris

Lower area is covered with dense fibrofatty tissue and supports body weight.

Lateral part : Origin on extensor digitorum brevis, attachment of inf extensor retinaculum, stem of bifurcate ligament.

Plantar Surface : Origin of abductor hallucis, flexor digitorum brevies. Attachment of Plantar aponeurosis.

Origin of abductor digiti minimi Medial margin of sustentaculum tali

and gives attachment to Spring ligament ant , tibialis posteriorly in middle , deltoid ligament , talocalcaneal ligament posteriorly.

NAVICULAR : Boat shaped Medial side between talus and cuneiforms Distal surface 3 facets Proximal surface articulates with talar head Dorsal surface rough for attachment of

ligaments Plantar surface is non-articular.

ATTACHMENTS ON NAVICULAR Tuberosity receives insertion of tibialis

posterior Plantar surface provides attachment to

spring ligament Calcaneonavicular part of bifurcate

ligament is attached to lateral surface.

CUBOID Lateral bone of distal row Between calcaneus proximally and

fourth and fifth metatarsals distally Dorsal surface is rough for attachment

of ligaments Medial surface is articular for Lat.

Cuneiform and non-articular.

ATTACHMENTS OF CUBOID Lateral surface occupies tendon of

peroneus longus Poseromedial part of plantar surface

provides insertion to a slip of tibialis posterior and origin of flexor hallucis brevies.

Non-articular part of medial surface provides attachment to lateral limb of bifurcate ligament.

CUNEIFORMS Wedge like articulate with navicular

proximally and bases of first to third metatarsals distally

Medial largest , intermediate smallest Dorsal surface of lat and intermediate

cuneiforms form base of wedge, wedge is reversed in med cuneiform,which is prime factor in shaping transverse arch.

MEDIAL CUNEIFORM Proximal surface has a piriform facet

for navicular Distal surface has a large kidney

shaped facet for base of first metatarsal

Medial surface is rough and subcutaneous

ATTACHMENTS Tibialis anterior on anteroinf surface of

M.Cuneiform Part of peroneus longus inserted on lat

surface Intermediate cuneiform attachment to

part of tibialis posterior Plantar surface of lat cuneiform

receives a slip of tibialis posterior and part of flexor hallucis brevies.

METATARSALS Lie distal in foot and connect tarsus

and phalanges Have shaft, proximal base and distal

head Convex dorsally and concave on

plantar aspects

FIRST METATARSAL Shortest and thickest Gives attachment to tibialis anterior tendon medially and peroneus longus tendon on plantar aspect Origin to first dorsal interosseus muscle

SECOND METATARSAL Longest Base has four articular facets Because of its length and steep

inclination and position of base, it is at risk of stress overload and avasular phenomena.

Third MTP is relatively stiff and predisposes to stress fracture

PHALANGES 14 phalanges Two in hallux, three in other toes Much shorter than hand Compressed from side to side

ANKLE JOINT Complex, three-bone joint It consists of the tibial plafond (including the

posterior malleolus articulating with the body of the talus), the medial malleolus, and the lateral malleolus.

The dome itself is wider anteriorly than posteriorly, and as the ankle dorsiflexes, the fibula rotates externally through the tibiofibular syndesmosis, to accommodate this widened anterior surface of the talar dome.

STABILITY OF ANKLE Passive : Medial and lateral ligaments,

bony contours and capsular attachments

Dynamic stability by gravity , muscle action and ground reaction forces.

Stability requires continuous action of soleus and gastronemius.

TALOCALCANEAL JOINT Ant and post articulations between

talus and calcaneum “ Subtalar joint ” Post articulation is talocalcaneal joint Ant articulation is

talocalcaneonavicular joint

Inversion by Tibialis ant and posterior Eversion by Peroneus longus,brevies and tertius

LIGAMENTS Ankle stability is conferred by bony

architecture and ligaments supporting ankle joint

1.Syndesmotic ligaments2.Medial collateral ligaments3.Lateral collateral ligaments

SYNDESMOTIC LIGAMENTS

LATERAL COLLATERAL LIGAMENTS Ant talo-fibular ligament Calcaneo fibular ligament : Resists

inversion Post talofibular ligament : Strongest

and prevents posterior and rotatory subluxation of talus

MEDIAL COLLATERAL LIGAMENTS Deltoid ligament : Superficial and deep part Superficial fibers arise from medial malleolus

and they attach into navicular, the neck of the talus, the medial border of the sustentaculum tali, and the posteromedial talar tubercle. The tibiocalcaneal ligament is the strongest component of the superficial layer of the deltoid ligament, and it is responsible for resisting eversion of the calcaneus.

Deep layer of the deltoid ligament is the primary medial stabilizer of the ankle joint. It is a short, thick ligament

The strongest fibers insert on the medial surface of the talus.

This ligament is virtually inaccessible from outside the joint, and it cannot be repaired unless the talus is displaced laterally or if the medial malleolus is inverted distally through fracture or osteotomy.

ARCHES OF FOOT Medial longitudinal arch : Ligaments resposible for stability Most imp is Plantar aponeurosis, Spring

ligament Flexor hallucis longus, flexor digitorum

longus,abductor hallucis. Tibialis ant and post : Inverting and

adducting

MEDIAL LONGITUDINAL ARCH

Medial Longitudinal Arch continued

Muscular SupportIntrinsic

Abductor HallucisFlexor Digitorum Brevis

Extrinsic Tibialis PosteriorFlexor Hallucis LongusFlexor Digitorum LongusTibialis AnteriorFlexor Digitorm Longus

LATERAL LONGITUDINAL ARCH Lateral part of plantar aponeurosis ,

long and short plantar ligaments Peroneus longus tendon

Lateral Longitudinal Arch continued

Muscle SupportIntrinsic

Abductor Digiti MinimiFlexor Digitorum Brevis

Extrinisic Peroneus Longus, Brevis & Tertius

TRANSVERSE ARCH Bases of 5 metatarsals , cuboid and

cuneiforms Stability by ligaments bind cuneiform

and metatarsal bases and peroneus longus tendon.

Ligament SupportIntermetatarsal LigamentsPlantar Fascia

Muscle SupportAll intrinsic musclesExtrinisic

Tibialis PosteriorTibialis AnteriorPeroneus Longus

PLANTAR FASCIA The plantar fascia is a strong fibrous aponeurosis that runs from the calcaneus to the base of the phalanges. It supports the arches and protects structures in the foot.

MUSCLES

Superficial LayerAbductor HallucisAbductor Digiti MinimiFlexor Digitorum Brevis

Middle Layer Quadratus Plantae Lumbricals

Deep LayerFlexor Hallucis BrevisAdductor Hallucis

Transverse and Oblique Heads

Flexor Digiti Minimi

Interosseus LayerPlantar InterosseiDorsal Interossei

BIOMECHANICS Most of motion of foot occurs at three

synovial joints1. Talocrural joint2. Subtalar joint3. Mid-tarsal joint Most of motion occuring in hind foot

Normal motion of the ankle joint is predominantly in the sagittal plane

Axis of the ankle joint as passing approximately 5 mm distal to the tip of the medial malleolus and 3 mm distal and 8 mm anterior to the lateral malleolus . a continuously changing axis of rotation. In dorsiflexion, the axis is inclined downward and laterally, whereas in plantar flexion, the axis is inclined downward and medially.

Plantarflexion (PF) and dorsiflexion (DF) occur about a mediolateral axis running through the ankle joint. The range of motion for plantarflexion and dorsiflexion is approximately 50° and 20°, respectively.

During dorsiflexion of the ankle, the intermalleolar distance increases approximately 1.5 mm as the fibula rotates externally and displaces laterally.

With the deltoid ligament, it contributes to the rotational stability of the talus Stability of the ankle joint in stance appears to be conferred mostly by articular congruity

The axis of rotation for the subtalar joint runs obliquely from the posterior lateral plantar surface to the anterior dorsal medial surface of the talus

Obliquity of axis

Pronation1. Eversion in frontal plane2. Abduction in Transverse plane3. Dorsiflexion in Sagittal plane Supination is opposite

Prime function of the subtalar joint is to absorb the rotation of the lower extremity during the support phase of gait. With the foot fixed on the surface and the femur and tibia rotating internally at the beginning of stance and externally at the end of stance, the subtalar joint absorbs the rotation through the opposite actions of pronation and supination

Midtarsal joints consist of calcaneocuboid joint and talonavicular joint.

Each joint has an axis of rotation that runs obliquely across the joint. When the two axes are parallel to each other, the foot is flexible and can freely move. If the axes do not run parallel to each other, the foot is locked in a rigid position.

Movement at the midtarsal joint depends on the subtalar joint position. When the subtalar joint is in pronation, the two axes of the midtarsal joint are parallel, which unlocks the joint, creating hypermobility in the foot.

This allows the foot to be very mobile in absorbing the shock of contact with the ground and also in adapting to uneven surfaces

During supination of the subtalar joint, the two axes run through the midtarsal joint converge. This locks in the joint, creating rigidity in the foot necessary for efficient force application during the later stages of stance.

The motion at the midtarsal joint is unrestricted from heel strike to foot flat

The midtarsal joint becomes rigid and more stable from foot flat to toe-off in gait as the foot supinates

BIOMECHANICS WHILE STANDING In standing, half of the weight is borne

by the heel and half by the metatarsals. One third of the weight borne by the metatarsals is on the first metatarsal, and the remaining load is on the other metatarsal heads

Lateral longitudinal arch relatively flat and limited in mobility it is lower than the medial arch, it may make contact with the ground and bear some of the weight in locomotion, thus playing a support role in the foot.

Dynamic medial longitudinal arch. It is much more flexible and mobile than the lateral arch and plays a significant role in shock absorption upon contact with the ground.

BIOMECHANICS WHILE WALKING At heel strike, part of the initial force is

attenuated by compression of a fat pad positioned on the inferior surface of the calcaneus. This is followed by a rapid elongation of the medial arch that continues to maximum elongation at toe contact with the ground

The medial arch shortens at midsupport and then slightly elongates and again rapidly shortens at toe-off . Flexion at the transverse tarsal and tarsometatarsal joints increases the height of the longitudinal arch as the metatarsophalangeal joints extend at pushoff . The movement of the medial arch is important because it dampens impact by transmitting the vertical load through deflection of the arch

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