anatomy and biomechanics of foot
DESCRIPTION
ANATOMY AND BIOMECHANICS OF FOOT. Presenter : Dr. SYED IMRAN Chair person : Dr. RUPAKUMAR C.S. Dr. SRINIVAS DEEP URS. 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. - PowerPoint PPT PresentationTRANSCRIPT
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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