Basic Science of FootProf. P. Bala subramaniamSingapore

Basic Science of FootNew knowledge has come into diagnosis and surgery of ankle and footArthroscopic and endoscopic anatomy, joint replacement, sports medicine and sports injuriesUnlearn and relearn new knowledge. some old knowledge and concepts still important

Pathological conditions of the foot

Foot : general principlesHighly specialized for weight bearing, shock absorption and locomotion.

Arches of foot built on structural engineering principles for transmission of forces and shock absorption.

Foot : general principlesTwo extreme modes of function

1. as a rigid structure when the 26 bones of the foot are converted into a single unit eg. ballet dance on point , kicking

2. as a supple structure. eg. climbing a tree

Foot: general principlesSpeed and power push the feet to extreme limits. Kinematic chain with the leg powered by extrinsic and intrinsic muscles loss of kinematic and structural restraints affect ankle and foot stability Dynamic & static stability of feet The whole foot is wrapped up in specialized skin and deep fascia

Skin of foot on dorsum : lax and thin, poor blood supply.Sole :a weight bearing cushion for toes, MT heads, and heel : fat padsHeel structure : 18mm thick padding cover the tuber calcaneusHeel pads contain specialized fat in MICRO and MACRO chambers

Skin of foot: dorsum & sole

Heel structureThe cup ligament attached to periosteal layer of calcaneum by a series of tough septa that form a U-system.Septa seal off chambers with fatFlow of fat within chambers for shock absorption; running , jumping 10x BWAging & overuse : septa breakdown to confluent cavities loss of shock absorption , painful heel

Heel structure

Deep fascia of footSpecial arrangements a. planter aponeurosis :truss & windlass b. 9 compartments of foot c. retinacula to strap tendonsPlanter aponeurosis extends from calcaneum to planter aspect of p.phalanx Is a truss-like structure across longitudinal arch . A cable between heel & toes

Planter aponeurosis ctdIt locks tarsal joints together by a windlass mechanism at the MTP attachment of the fascia when the proximal phalanx is dorsiflexed.Combined truss and windlass mechanism raise the arches of foot , lock the joints and make a single unit of multiple bones and joints

Deep fascia: Retinacula of footSuperior extensor retinaculumInferior extensor retinaculumFlexor retinaculumSuperior peroneal retinaculumInferior peroneal retinaculumThickened restraining bands that hold tendons in position and form pulleys within which tendons slide when they change direction at ankle

Deep fascia:Peroneal retinacula

Deep fascia of foot

Muscles of the footFoot :a jointed / lever system powered by muscles --- the extrinsic and intrinsic muscles.Extrinsic muscles are in extensor, flexor and lateral compartments of leg.Intrinsic muscles: 4 layers of musclesA balanced plantigrade foot necessary to achieve its functions

4 layers of muscles of soleFirst layer: : abdh,fdb,abddm, pl apon, lat & medial pl digital nerves ( med& lat planter nerve & vessels)Second layer: quadratus planti from fdl, 4 lumbr, fdl crosses fhl, tib post to navicularThird layer : fhb, addh, fdm, lat pl art & nerveFourth layer : 3 pl interossei , 4 dorsal int

Muscles of the foot extrinsic and intrinsic

Dorsum of footExtensor digitorum brevis muscle & ehbAbsent in 10%L5 nerve root supply, PID wasting of edbAnatomic door to bony structuresElevate its origin, sinus tarsi TC,TN,CC jtTib ant, EHL, artery & nerve, EDL ,PTSurgical approach to ankle & foot

Blood supply and venous drainageArterial supply very peripheralFrom anterior tibial & posterior tibialAnt. tibial gives rise to dorsalis pedis, ant & lat maleolar arteriesArterial supply of foot from dorsalis pedis, arcuate artery, dorsal metarsal arteries , digital arteries , lateral pl artery, medial plantar artery

Venous drainageSuperficial and deep groupDeep veins accompany the arteriesMost of them contain valvesPerforating veins connect both Blood flow is from superficial to deepMuscle pumpDVT ---incompetenceLong saph to femoral, short to popliteal

Nerve supply of footPeroneal nerve to extensor and lateral compartmentsTibial nerve to flexor compartmentHas a neuromuscular mechanism for posture & balance even with a small base of supportCutaneous supply saphenus, ant tibial , musculocutaneus & sural nerveRoot value : L4,L5,S1, S2, referred pain

Nerve supply of foot

Biomechanics of footComplex and different from those of ankle.The necessity of foot- to- floor stability dictates that the foot itself must independently adapt a variety of conditionsLoss of kinematic & structural restraints affect ankle & foot stability & produce malalignment of ankle joint surfaces

Biomechanics of foot Its intricate construction, complex dynamic organization provide for shock absorption, stability and propulsion of body.

It successfully performs this task by forming a kinematic chain with the legFoot must be stable for function. Stability mechanism of foot depends on arches of the foot, muscle control and sensory feed back.

Biomechanics of footStability of foot depends on the 3 archesLateral arch , lower and shorter composed of calcaneum, cuboid and lateral 2 rays. This system is the more stable and weight bearing portion of the arches It carries the larger & higher medial arch consisting of calcaneus, talus, navicular, cuneiforms and 3 medial rays

Biomechanics of footTransverse arch : configured by the shape of midtarsal bones cuneiforms, & cuboid and the bases of metatarsals.

Longitudinal arch is not intrinsically stable owing to the shape of bones . Stabilized by heavy ligamentus structures surrounding the joint

Biomechanics of foot

Biomechanics of foot

Planter aponeurosis and biomechanics of footTruss like structure across the longitudinal arch; like a cable between heel and toes.windlass mechanism through proximal phalanx attachment of fascia; dorsiflexion of toes shortens the truss , raises the arch and making it a single unit of multiple bones & joints

Foot functionally divided into three sectionsHind foot talus & calcaneus. Responsible for most of motion in footMidfoot -- navicular, cuneiforms & cuboid. Responsible for medial & lateral column stabilityForefoot 5MT , 6 weight bearing contactsCompeting issues of stability & mobility Load evenly distributed over the foot during weight bearing50% thru subtalar joint to calcaneum50% equally among the 6 points of contact of ff

Fore foot

1st ray: halux valgusIntermetatarsal angle 8-9 degrees valgus angle of 1st MTP jt 30-35 degreesAdductor hallucis Mcbride proceduresesamoid ridge on the planter surfaceDisplacement into inter-metatarsal spaceLess weight bearing on 1st ray transfer metatarsalgia

Fore foot ctd2nd ray: base of MT recessed in between the cuneiforms rigid , stress #3rd web space: planter digital neuroma5th metatarsal: stress fracture , peroneous brevis inserted into base Soft tissue support for forefoot alignment mainly of dense ligaments between the lesser metatarsals

Hind footCalcaneum: articular surface for talus & cuboidSustentaculum tali supports neck of talusFHL courses beneath sustentaculum taliAchilles tendon inserted into posterior aspect of tuberosity. Bohlers angle 20-40 deg. assess the posterior facet in calcaneal #sGissanes angleCT anatomy in calcaneal #s

TalusBody, neck and head.60% articular, vas accessDefines ankle & subtalar motionAnchors medial column of foottalar dome articulates with tibial plafondInferiorly with the calcaneusLaterally with malleoliHas no muscle attachmentTwo bony processes. Posterior & lateral #

Foot disorders : hind foot

MidfootNavicular, cuneiforms and cuboidTalonavicular & calcaneocuboid jointsTarsometatarsal jt (Lisfrancs injury) Functionally the weight bearing position of forefoot depends on proper alignment of this joint complexTib post inserted to tuberosity of navicularTib ant inserted to medial cuneiform

Foot: tarsal coalition

Special anatomy for Ankle arthroscopy : portals: anterior, lateral, middle, ?posterior.Impingement, osteophytes, loose bodies, arthroscopic arthrodesisAnatomy thru the scope: looking at structures within the jt from insideHindfoot endoscopy: ostrigonum, posteroir impingement

Basic science of foot for sportsWalk, run, jump, hop, dance, kick, forward movement, side to side movement.Subject to great ground reaction forcesSpeed & power , overuse soft tissues & bonesNormal, rigid, or floppy feet. archTendons & bursae, bones joints, ligaments

Summary basic science of footGeneral principles of foot structure & functionSkin of foot: sole a weight bearing cushionDeep fascia specialization 3Powered by extr and intr muscles: BalanceVascular and nerve supplyBiomechanics of footArthroscopic & endoscopic anatomyAnatomy for sports medicine & sp. injuries