Hersheychapter 33

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Chapter 33: AnatomyNeuroanatomyAngiologyMyology

Arthrology

33



ANATOMY Neuroanatomy1. Femoral nerve:a. Formed from the ventral rami of lumbar nerve roots (L2, L3, and L4)b. Divides into anterior and posterior division (the posterior division gives riseto the saphenous nerve which supplies cutaneous innervation to the medial

leg and foot)

2. Sciatic nerve:a. Formed from the ventral rami of lumbar and sacral nerve roots (L4, L5, S1,S2, and S3)b. The largest nerve of the bodyc. Divides into its terminal branches, the tibial and common peroneal nerved. Supplies all musculature of the leg and foot (except 'for that supplied bythe saphenous nerve)

3. Common peroneal nerve (L4, L5, S1, S2):

a. One of 2 terminal branches of the sciatic nerve, and winds superficiallyaround the neck of the fibulab. Gives off the sural communicating near the head of the fibula, which joinswith a communicating branch of the tibial nerve to form the sural nervec. Terminal Branches:i. Deep peroneal nerve: This nerve runs with the anterior tibial artery(laterally) in the lower leg to give muscular innervation to the EDL, EHL, TA,peroneus tertius, EDB, and ends in the first interspaceii. Superficial peroneal nerve: In the distal 1 /3 of the leg, the nerve piercesthe anterolateral intermuscular septum and deep fascia to becomecutaneous, and divides into 2 branches, the medial and intermediate dorsal

cutaneous nerves before reaching the ankle. This gives innervation to theperoneus longus and brevis

4. Tibial nerve (L4, L5, S1, S2, S3):a. The larger of the 2 branches of the sciatic nerveb. Travels between the two heads of the gastrocnemius to leave the poplitealfossa, descends along the back of the leg with the posterior tibial artery andveinsc. The nerve lies medial to the blood vessels in the upper 1 /3 of the leg andlateral to them in the lower 1 /3 of the leg d. The nerve supplies thegastrocnemius, popliteus, tibialis posterior, FHL, and FDL

e. Terminates into medial and lateral plantar nerves at the level of thelacinate ligament (prior to this, gives off medial calcaneal branch)

5. Sural nerve (L5, S1,S2):a. Formed by union of medial sural cutaneous (tibial) and suralcommunicating branch of the lateral sural cutaneous of the commonperonealb. Pierces the deep fascia to become cutaneous at the upper mid-calf region,travels distally near the lateral side of the achilles with the small saphenous



vein, and passes forward below the lateral malleoluse. Becomes the lateral dorsal cutaneous nerve on the lateral aspect of thefoot

6. Saphenous nerve (L3,L4):a. This is the only nerve in the foot that originates from the lumbar plexus(comes off the posterior division of the femoral nerve and is its longestbranch)b. Travels with the greater saphenous vein along the medial side of the legc. It divides into 2 branches in the lower 1 /3 of the leg giving sensoryinnervation to the skin of the medial ankle and medial side of the foot (it mayreach distally as far as the metatarsophalangeal joint)

7. Deep peroneal nerve (L4, L5, S1):a. Travels with the anterior tibial artery and lies lateral to it in the footb. Divides into its terminal branches and passes into the dorsum of the foot inthe middle compartmentc. Its terminal branches are the lateral terminal nerve (passes across thetarsal area to innervate the EHB) and the medial terminal nerve (to the 1stinterspace) where this divides into 2 dorsal digital nerves (2nd dorsal digitalproper nerve & 3rd dorsal digital proper nerve)

8. Superficial peroneal nerve (L5, S1, S2):a. Primarily a cutaneous nerve with 2 terminal branches, the medial andintermediate dorsal cutaneous nervesb. Medial dorsal cutaneous nerve divides into a medial and lateral branch. These supply the medial side of the hallux, lateral side of the 2nd toe, andthe medial side of the 3rd toe.c. Intermediate dorsal cutaneous nerve divides into medial and lateralbranches. These supply the lateral side of the 3rd toe, medial side of the 4thtoe, lateral aspect of the 4th toe, and the medial aspect of the 5th toe

9. Lateral dorsal cutaneous nerve (S1, S2):a. A continuation of the sural nerve below the ankle, and communicates withthe intermediate dorsal cutaneous nerve, and divides into 2 branches (one tothe lateral side of the 5th toe, and the other anastomoses with branch of thesuperficial peroneal nerve)



10. Medial calcaneal nerve (S1, S2):a. Last branch given off by the tibial nerve before dividing into medial andlateral plantar nervesb. It perforates the lacinate ligament and divides into anterior and posteriorbranches (posterior branch supplies the heel)c. The anterior branch continues distally into the plantar aspect of the foot,where it anastomoses with the lateral calcaneal branch of the sural nervelaterally, anastomoses with the saphenous nerve anteromedially andanastomoses with the lateral and medial plantar nerves distally

11. Lateral Calcaneal Nerve (S1, S2):a. Given off before the sural nerve goes around the lateral malleolusb. Supplies the cutaneous innervation to the lateral aspect of the heel andsensory innervation to the lateral proximal aspect of the plantar surface of the foot



12. Medial plantar nerve (S3):a. Larger of the 2 terminal branches of the tibial nerve running in the 3rdcompartment of the lacinate ligamentb. Enters the foot at the porta pedis and emerges from between the abductorhallucis and FDL

c. Supplies the cutaneous innervation to the medial plantar aspect of themidfoot, abductor hallucis, FDBd. Its terminal branches are the 1st plantar digital nerve and 1st, 2nd and 3rdcommon plantar digital nerves



]

13. Lateral plantar nerve (S2, S3):a. Smaller of the 2 terminal branches of the tibial nerve, lying posterior to theposterior tibial artery, eventually lying medial to the lateral plantar arterywith which it travels into the plantar aspect of the foot b. The nerve passesthrough the porta pedis lying between the FDB and quadratus plantae.Between the FDB and abductor digiti minimi the nerve divides into its 2terminal branches, superficial and deep c. Superficial branch comes off themain branch at the level of the 5th metatarsal and supplies the flexor digitiminimi brevis, opponens digiti





minimi (when present), 3rd plantar interosseous, and 4th dorsal interosseousd. Deep branch follows along with the lateral plantar artery between the 3rdand 4th muscle layers (deep to the adductor hallucis and superficial to theplantar interossei) and supplies the transverse/oblique heads of the adductorhallucis, lateral 2 (or 3) lumbricales, and interosseous muscles of the 2nd and3rd intermetatarsal space (2nd and 3rd dorsal, 1st and 2nd plantar), and 1stdorsal interosseous

Angiology1. The arteries: Blood flows from the left ventricle of the heart, through theascending aorta, aortic arch, descending aorta, thoracic aorta, and abdominalaorta. In the lower abdomen, the aorta divides into paired common iliacarteries. Each common iliac artery divides distally into internal and external

iliac arteries. The external iliac artery becomes the femoral artery as itpasses under the inguinal ligament,a. Femoral artery: Courses through the medial thigh through the femoraltriangle into the adductor canalb. Deep femoral (profunda femoris): The last branch of the femoral arterybefore leaving the femoral trianglec. Popliteal: When the deep femoral crosses over the medial femur it thenbecomes the popliteal and continues to the lower border of the popliteuswhere it divides into anterior and posterior tibial (before its bifurcation itgives off a sural branch which is the only source of blood to thegastrocnemius)

d. Anterior tibial: Branches off the popliteal artery at the level of the solealline, travels into the anterior compartment of the leg, lies between the tibialisanterior and EDL muscle bellies in the proximal 1/3 of the leg. Immediatelyabove the the ankle joint the EHL tendon crosses over the anterior tibialartery and at this level the artery is found between the EHL and EDL. Theanterior tibial artery can terminate as the dorsalis pedis or becomesinsignificant before reaching the ankle joint, and if this happens, the dorsalispedis will be absent or arise as a branch of the perforating peroneal artery

NOTE* The 1st and 2nd dorsal interossei receive additional innervation fromthe deep peroneal nerve



i. Branches of anterior tibial artery

• Posterior recurrent tibial

• Anterior recurrent tibial

•

Muscular branches (to the tibialis anterior, EDL, EHL,peroneus tertius, and muscles of the deep posteriorcompartment of the leg)

• Anterior medial malleolar (superficial and deep branches)

• Anterior lateral malleolar (transverse portion meets withbranches from perforating peroneal; descending portionanastomoses with the descending retromalleolar branch of theperoneal artery)

e. Dorsalis pedis: Begins as it crosses the ankle joint continuous with theanterior tibia] artery, and gives off branchesi. Branches of the dorsalis pedis

• Medial branches (medial tarsal arteries)• Lateral branches (artery to the sinus tarsi, lateral tarsal, arcuate,anterior perforating, 4th dorsal metatarsal, and 1 st dorsal metatarsal artery)f. Posterior tibial: Branches off the popliteal artery at the level of the solealline, remains within the posterior compartment of the leg, runs superficial tothe tibialis posterior proximally and over the FDL distally as it descends intothe medial ankle into the 3rd compartment of the flexor retinaculum, andbifurcates into medial and lateral plantar arteries while in the 3rdcompartment deep to the muscle belly of the abductor hallucis



i. Branches of the posterior tibial artery

• Circumflex fibular

• Peroneal (gives off muscular branches, perforating branch,communicating branch, posterior peroneal, anterolateral transverse branch,collateral branch, and recurrent calcaneal branches)

• Nutrient artery (supplies the tibia)











crural fascia, and the intermuscular septum

• Insertion: Into the medial and plantar aspects of the medial cuneiform(90%) and the medial and plantar aspects of the base of the 1st metatarsal(10%)

• Vascular supply: Anterior tibial artery

• Innervation: Deep peroneal nerve

•

Functions: Statically in dorsiflexion of the foot on the leg, anddynamically to accelerate and decelerate the foot during gait, assist indorsiflexion at toe off, dorsiflex the 1 st ray during swing, resistsplantarflexion of the foot at heel strike, prevents excessive pronation duringswing, and supinates the midtarsal joint around its longitudinal axis prior toheel strikeii. Extensor hallucis longus:

• Origin: Anterior surface of the fibula at its middle half (medial to theorigin of the EDL) and the interosseous membrane

• Insertion: Inserts at the base of the distal phalanx of the hallux

• Vascular supply: Anterior tibial

• Innervation: Deep peroneal nerve• Functions: Statically it dorsiflexes the foot on the leg, extends thehallux, extends the distal phalanx on the proximal phalanx, and assists ininverting the foot. Dynamically, during stance it creates a "rigid beam effect"for the hallux by stabilizing the 1st MTPJ and the IPJ, and during swing it actsas the strongest dorsiflexor of the foot and accelerates the foot immediatelyafter toe off iii. Extensor digitorum longus:

• Origin: Lateral condyle of the tibia, upper 3/4 of the lateral condyle of the tibia, upper 3/4 of the anterior surface of the tibia, upper lateral part of the interosseous membrane, deep surface of the crural fascia, and theanterior peroneal septum

• Insertion: It divides into 4 tendons at various distances proximal to theankle joint, and sends a tendon to each lesser toe. Near the metatarsalheads, each tendon forms a membranous expansion (extensor hood) whichcovers the MTPJ dorsally and laterally and receives tendons of insertion fromthe lumbricales and interossei muscles to the lesser toes. Tendons to the2nd, 3rd, and 3rd toes receive tendons from the EDB on their lateral sides. The EDL tendons to each toe then divide into 3 parts distal to the extensorhood apparatus at the head of the proximal phalanx

• Vascular supply: Anterior tibial artery

•

Innervation: Deep peroneal nerve• Functions: Statically the EDL dorsiflexes the foot on the leg, extendsthe lateral 4 toes, and extends the phalanges of the toes upon each other.Dynamically, it stabilizes and accelerates the foot during gait, and during thepropulsive period of gait it helps create a "rigid beam effect" in each lessertoe by assisting the lumbricales in rigidly extending the IPJs duringpropulsion. During swing phase it assists in dorsiflexioniv. Peroneus tertius:

• Origin: From the lower border of the anterior surface of the fibula, and



adjoining portion of the interosseous membrane

• Insertion: On the dorsum of the base of the 5th metatarsal

• Vascular supply: Anterior tibial

• Innervation: Deep peroneal nerve

• Functions: Statically in flexion of the foot on the leg and eversion of thefoot. Dynamically it assists in dorsiflexion of the foot for clearance of the toes

during swing, and helps prevent excessive supination of the foot duringswingb. Muscles of the lateral compartment:i. Peroneus longus:

• Origin: From the head and upper 1/2 of the lateral surface of the fibula,the crural fascia, and the anterior/posterior septa

• Insertion: Posterolateral inferior angle of the base of the 1st metatarsal(90%) and the adjacent portion of the medial cuneiform (does give a slip thatgives origin to the 1st dorsal interosseous muscle)

• Vascular supply: Anterior tibial and peroneal arteries -Innervation:Superficial peroneal nerve

• Functions: Statically in plantarflexion of the foot on the ankle, eversionof the foot. Dynamically it is a stance-phase muscle by stabilizing the base of the 1st ray against the tarsal bones, stabilizes the 1st metatarsal headplantarly against the ground, resists the adductory force exerted on the firstray by the tibialis posterior, and assists (with the peroneus brevis) intransferring body weight from lateral to medial side of the forefoot duringpropulsionii. Peroneus brevis:

• Origin: from the lower 2/3 of the lateral surface of the fibula and theanterior/posterior personeal septa

• Insertion. Lateral aspect of the tuberosity of the 5th metatarsal

• Vascular supply: Peroneal artery

• Innervation: Superficial personeal nerve

• Functions: Statically it plantarflexes the foot on the leg and everts thefoot. Dynamically it is a stance phase muscle by assisting the peroneuslongus in producing an abductory stabilizing force on the foot duringmidstance and propulsion, stabilizes the lateral column during midstanceand propulsion, resists supination of the foot and external rotation of theleg by the calf muscles, provides a pronatory force at the subtalar andmidtarsal joints and assist the peroneus longus in transferring body weightfrom the lateral to the medial forefoot

c. Muscles of the posterior compartment (divided into superficial and deepcompartment)i. Gastrocnemius (superficial):

• Origin: The medial head (larger) of the gastrocnemius from theposterior portion of the medial condyle of the femur, the lower part of thesupracondylar line, and the posterior aspect of the knee joint capsule. Thelateral head from the posterior portion of the lateral condyle of the femur andthe lower part of the lateral supracondylar line



• Ins

ertion: Fuse with the soleus to form the Achilles tendon

• Vascular supply: Sural branch of the popliteal artery to each headentering the origin of the muscle

• Innervation: Tibial nerve

• Functions (swing phase): Prevents hyperextension of the knee, assistsin deceleration if the internal rotation of the leg toward the end of contact, toprevent torque forces from developing in the knee, assists in developingsupination of the STJ during midstance and early propulsion, and flexes theknee and lifts the heel to initiate propulsionii. Soleus (superficial):

• Origin: From the upper 1 /3 of the posterior portion of the fibula,posterior surface of the fibula, posterior portion of the head of the fibula,soleal line on the posterior surface of the tibia, and the middle 1 /3 of themedial border of the tibia

• Vascular supply: Posterior tibial artery, peroneal and sural arteries-Innervation: Tibial nerve

• Functions (stance phase): Stabilizes the lateral forefoot against theground during late contact and midstance, assists in decelerating knee

flexion, assists in decelerating STJ pronation and internal leg rotation at theend of contact, assists in extending the knee during midstance, assists inheel lift during propulsion by stopping ankle joint dorsiflexion

iii. Achilles tendon:

• The thickest and strongest tendon in the body in the lower 1 /4 of theleg. The fibers of the soleus are anterior to those of the gastrocnemiusproximally, and as the tendon passes distally, the gastrocnemius fibers takea lateral turn to become lateral to the soleus fibersiv. Plantaris (superficial):

• Origin: From the lateral supracondylar line of the femur, slightly medial

to the lateral head of the gastrocnemius• Insertion: Into the medial edge of the tendo Achilles -Vascular supply:Sural arteries


• Functions: Statically it flexes the leg on the thigh and plantarflexes thefoot on the leg. Dynamically, it assists the gastrocnemius in its functionduring locomotionv. Flexor digitorum longus (deep):

• Origin: From the posterior surface of the tibia below the popliteal line

NOTE* The tendon of the lateral head of the gastrocnemius may contain asesamoid bone (fabella)The soleus attaches to the medial 2/3 of the deep surface of the tendo- Achilles The plantaris is absent 7% of the timeThe tendo Achilles is 15 cm in length

The gastrocnemius passes across 3 joints (knee, ankle, STJ) The soleus passes across 2 joints (Knee and ankle)



and medial to the vertical line and from the fascia of the tibialis posteriormuscle belly

• Insertion: Into the middle of the bases of the distal phalanges of thelateral 4 toes plantarly

• Vascular Supply: Posterior tibial artery


•

Functions: Statically, plantarflexing the foot on the leg, flexes thelateral 4 toes upon their metatarsals, and flexes the phalanges of each toeuponeach other. Dynamically (stance phase) assists with deceleration of STJpronation and internal leg rotation during contact, assists with deceleration of the forward motion of the tibia during midstance, assists with STJ supinationand external leg rotation during midstance, assists with deceleration of ankle joint dorsiflexion (contributes to heel lift), maintains stability of the lesserdigits against the ground during propulsion, assists in plantarflexion of thefoot upon the leg during propulsion, and assists the abductor hallucis and FHLin supination of the MTJ about its oblique axis during early propulsion

vi. Flexor hallucis longus (deep):• Origin: From the lower 2/3 of the posterolateral portion of the posteriorsurface of the fibula, posterior peroneal septum, deep transverseintermuscular septum

• Insertion: Into the base of the distal phalanx of the hallux, plantarly

• Vascular supply: Peroneal and posterior tibial


• Functions: Flexes the hallux at the MTPJ and IPJ, and plantarflexes thefoot on the leg. Dynamically it assists with deceleration of the forwardmomentum of the tibia during midstance, assists with STJ supination andexternal leg rotation during midstance, assists in deceleration of forward

momentum of the tibia, maintains stability of the hallux against the groundduring propulsion, assists in posterior stabilization of the phalanges on eachother against the 1st metatarsal head, and assists the abductor hallucis andFDL with supination of the MTJ about its oblique axisvii. Tibialis posterior (deep):

• Origin: From the posteriomedial surface of the fibula, posterior surfaceof the interosseous membrane between the tibia and fibula, posterior surfaceof the tibia

• Insertion: Primarily onto the tuberosity of the navicular, however,insertions reach all the tarsal bones except the talus

•

Vascular supply: Sural, peroneal, and posterior tibial arteries-innervation: Tibial nerve

• Functions: Plantarflexes the foot on the leg and inverts the foot.Dynamically it is a stance phase muscle that decelerates STJ pronation andinternal rotation of the leg during the contact period, assists withdeceleration of forward momentum of the leg during the contact andmidstance periods, accelerates STJ supination and external rotation of the legduring midstance, assists in heel lift by decelerating forward motion of thetibia in ankle joint dorsiflexion



4. Plantar aponeurosis and plantar compartments of the foot:a. Plantar aponeurosis/Plantar fascia: Is divided in 3 portions (central, lateral,and medial)i. Central portion: Is the thickest and strongest, triangular in shape, with itsapex attached to the posteromedial portion of the tuberosity of thecalcaneus. It extends distally and separates into 5 bands. At the level of the

metatarsal heads, each band divides into a deep and superficial process.

b. Plantarcompartments of the foot: Are divided into medial, central and laterali. Central compartment: Is the largest and contains 4 fascial spaces

• Contains tendons of the FDL, tibialis posterior, peroneus longus, andFDB, flexor accessorius, 4 lumbricales, and adductor hallucisii. Medial compartment:

• Contains the tendons of insertion of the tibialis posterior and FHL andmuscle bellies of the adductor hallucis and FDBiii. Lateral compartment:

• Contains the abductor digiti minimi, flexor digiti minimi brevis, andopponens

5. Intrinsic muscles of the dorsum of the foot:a. Extensor digitorum brevis:i. Origin: From the tubercle at the lateral end of the calcaneal sulcus and

cervical ligamentii. Insertion: To the lateral side of the EDL to toes 2, 3, and 4. It runssuperficial to the dorsalis pedis arteryiii. Vascular supply: Dorsalis pedis (lateral tarsal branch/perforating peroneal)iv. Innervation: Lateral terminal branch of the deep peroneal and occasionallythe superficial peronealv. Functions: Extends toes 2, 3, and 4 and extends the phalanges on eachother. Dynamically it is a stance phase muscle that stabilizes the MTJsoblique axis in a pronatory direction during propulsion, and stabilizes the2nd, 3rd, and 4th metatarsals against the lesser tarsus in a posteriordirection, assists

the lumbricalesand EDL inextending the2nd, 3rd, and4th toes duringpropulsionb. Extensorhallucisbrevis: This is

NOTE* There are several aponeurotic structures in the distal forassociated with the superficial processes:a. Natatory ligament: Made up of 6-8 bands of transversely orieaponeurotic tissue deep to the superficial portion of the plantar aponeurosis. It divides the area between the web spaces and dein the plantar aspect of the metatarsal head regionb. Fasciculus aponeurotica transversumc. Sagittal septad. Vertical fiberse. Mooring ligaments

f. Superficial transverse metatarsal ligament



the medial portion of the EDB muscle bellyi. Origin: From the tubercle at the lateral end of the calcaneal sulcus andcervical ligamentii. Insertion: Onto the dorsal aspect of the proximal phalanx of the hallux orthe lateral aspect of the EHL tendoniii. Vascular supply: Dorsalis pedis (lateral tarsal branch perforating peroneal)iv. innervation: Lateral terminal branch of the deep peroneal, andoccasionally the superficial peronealv. Functions. Extends the hallux at the MTPJ and extends the distalphalanx on the proximal phalanx of the hallux. Dynamically the EHB is astance phase muscle that stabilizes the 1st metatatarsal against the lessertarsus during midstance and propulsion, and assists in stabilizing the halluxagainst the 1st metatarsal in a posterior and abductory direction

6. Intrinsic muscles of the plantar aspect of the foot:a. First layer (superficial):i. Abductor hallucis:

• Origin: Medial process of the calcaneal tuberosity, lacinate ligament,plantar aponeurosis

• Insertion: Mainly to the plantar part of the MTPJ joint capsule and themedial sesamoid

• Vascular supply: Medial plantar artery




• Functions: Statically it flexes and abducts the hallux. Dynamically(stance phase) it stabilizes the hallux in an abductory direction, assists instabilizing the proximal phalanx against the 1st metatarsal head,plantarflexes the 1st ray, and stabilizes the oblique axis of the MTJ in asupinatory direction during propulsion against the pronatory force of theground reactionii. Flexor digitorum brevis:

• Origin: Medial process of the calcaneal tuberosity, and the deep surfaceof the plantar aponeurosis

• Insertion: Into the medial and lateral portions of the plantar aspect of the middle phalanx of each lesser toe

• Vascular supply: Medial plantar artery

• Innervation: Medial plantar nerve

• Functions: Statically it flexes the lesser toes and flexes the middlephalanx upon the proximal phalanx. Dynamically (stance-phase) it stabilizesthe oblique axis of the MTJ in a supinatory direction, stabilizes the 2nd, 3rd,and 4th rays posteriorly and plantarly, plantarflexes the lesser rays duringpropulsion, assists the FDL in maintaining the stability of the lesser digitsiii. Abductor digiti quinti (minimi):

• Origin: Lateral process of the calcaneal tuberosity, plantar surface of the calcaneus, plantar aponeurosis

•

Insertion: The lateral side of the base of the proximal phalanx of the5th toe plantarly with the tendon of the flexor digiti quinti brevis

• Vascular supply: Lateral plantar artery

• Innervation: Lateral plantar nerve

• Functions: Statically it flexes and abducts the 5th toe. Dynamically(stance phase) stabilizes the 5th toe posteriorly, plantarly, and in anabductory directionb. Second layer:i. Quadratus plantae: Has 2 heads with the medial head being larger. The2 heads come together to form a sheet-like 4 sided muscle• Origin: The medial surface of the calcaneus (lateral head originates

anterior to the lateral process of the calcaneus on its plantar surface from thelong plantar ligament)

• Insertion: Attaches to the lateral aspect of the FDL tendon, before itdivides



• Functions: Statically it aids in flexing the 4 lateral toes by assisting theFDL. Dynamically it stabilizes the oblique axis of the MTJ in a supinatory

NOTE* Just proximal to the MTPJ the tendon to each toe divides longitudinally to allow passage of the FDL. It reunites to form a grooved channel for theFDL under the proximal phalanx, and then divides again at the head of the proximal phalanx into 2 tendons



direction during midstance and propulsion, stabilizes the tendons of the FDL,and stabilizes the lesser metatarsals

ii. Lumbricals: Are numbered 1-4 from medial to lateral

• Origin: 1 st from the medial margin of the FDL to the 2nd toe. 2nd fromadjacent sides of of the 1st and 2nd FDL tendons. 3rd from adjacent sides of 2nd and 3rd FDL tendons, 4th from adjacent sides of 3rd and 4th FDLtendonsInsertion: Into the medial aspect of middle of proximal phalanges

• Vascular supply: Plantar metatarsal artery

• Innervation: 1st lumbrical L5 and S1 (medial plantar nerve), the rest viaroots S1 and S2

• Functions: Statically they function to flex the 4 lesser toes, adduct thelesser toes toward the hallux and extend the phalanges of each toe.Dynamically they function to extend the IPJs of each lesser toe, assist instabilizing the proximal phalanx of each lesser toe against the ground

c. Thirdlayer:i. Flexor hallucis brevis: Has a "Y" shaped configuration

• Origin: Originates from the medial aspect of the plantar surface of thecuboid (stem), the lateral and plantar aspects of the 3rd cuneiform (lateralarm), peroneus longus sheath, (lateral arm), tibialis posterior to the 3rdcuneiform and cuboid (lateral arm), and tendinous slips of the tibialisposterior to the metatarsal bases (medial arm)

• Insertion: 2 heads of insertion into the plantar plate of the 1st MTPJ and

sesamoid area, then passes forward to insert with the tendon of the abductorhallucis into the base of the proximal phalanx

• Vascular supply: 1st plantar metatarsal artery

• Innervation: Medial plantar nerve

• Functions: Statically it aids the hallux in flexion. Dynamically (stancephase) it stabilizes the base of the proximal phalanx of the hallux against theground during propulsion, assists in stabilizing the entire hallux against theground, and assists in stabilizing the 1st, 2nd, and 3rd metatarsals at themetatarsocuneiform joints during propulsionii. Adductor hallucis: This consists of 2 different muscle bellies of origin(oblique and transverse heads)

• Origin: Oblique head from the medial sides of the shafts and bases of metatarsals 2-4, adjacent portions of associated cuneiforms, and peronealsheath. The transverse head originates from the deep transverse metatarsalligaments, plantar plates, joint capsules, and plantar metatarsal ligaments 3-5 MTPJs

• Insertion: Both heads insert by a common tendon which inserts into abony prominence on the inferolateral aspect of the base of the proximalphalanx of the hallux with the tendon of the lateral head of the FHB

NOTE* All intrinsic muscles of the 2nd layer are related to tendons of thewhich pass through it



• Vascular supply: 1 st plantar metatarsal artery

• Innervation: Deep branch of the lateral plantar nerve

• Functions: Statically flexes hallux. Dynamically the oblique head is astance-phase muscle that stabilizes the hallux in an adductory direction aswell as a posterior direction against the metatarsal head and assists instabilizing the proximal phalanx against the ground during propulsion. The

transverse head is a stance-phase muscle that prevents elongation of thedeep transverse metatarsal ligament, and transverse stability to the forefootat the MTPJs during propulsioniii. Flexor digiti quinti (minimi) brevis:

• Origin: From the base of the shaft of the 5th metatarsal, crest of thecuboid, and peroneal sheath

• Insertion: To the base of the proximal phalanx of the 5th toe laterallyand plantar (along with the tendon of the abductor digiti quinti)


• Innervation: Superficial branch of the lateral plantar nerve

• Functions: Statically it abducts and flexes the 5th toe. Dynamically it

functions as an interosseous muscle during gait



d. Fourth layer:i. Plantar interossei: Three in number

• Origin: 1 st from the base and medial surface of the shaft of the 3rdmetatarsal. 2nd medial surface of the shaft and plantar surface of the base of the 4th metatarsal. 3rd from the plantar aspect of the base and medialsurface of the shaft of the 5th metatarsal

• Insertion: 1st inserts into the 3rd toe medially near the base of theproximal phalanx, and the medial side of the 3rd MTPJ capsule. 2nd is intothe 4th toe medially near the base of the proximal phalanx, and the medialside of the 4th MTPJ capsule. 3rd inserts medially into the 5th toe near thebase of the proximal phalanx, and the medial side of the 5th MTPJ capsule

• Vascular supply: 2nd, 3rd, and 4th plantar metatarsal arteries


• Functions: Statically the plantar interossei aid in flexing the toes intowhich they are inserted and aid in extension of the IPJs. Dynamically theydraw the toes medially toward the 2nd digit

ii. Dorsal interossei: Four in number

• Origin: 1st from the adjacent surfaces of the first and secondmetatarsals. 2nd from the adjacent surfaces of the second and thirdmetatarsals. 3rd from the adjacent surfaces of the third and fourthmetatarsals. 4th from the adjacent surfaces of the fourth and fifthmetatarsals

• Insertion: 1st inserts into the membranous expansion of the EDL to the2nd toe and the medial side of the base of the proximal phalanx of the 2ndtoe. 3rd into the membranous expansion of the EDL to the 3rd toe and thelateral side of the base of the proximal phalanx to the 3rd toe. 4th into the

the membranous expansion of the EDL to the 4th toe, and the lateral side of the base of the proximal phalanx of the 4th toe

• Vascular supply: 2nd, 3rd, and 4th plantar metatarsal arteries

• Innervation: Lateral plantar nerves (superficial and deep)

• Functions: Statically they aid in flexing the toe to which they insert andin extending the IPJs. Dynamically these are stance-phase muscles thatstabilize the bases of the proximal phalanges posteriorly and transverselyagainst their metatarsal heads

7. Extensor hood expansion:a. It is a membranous sheet covering each lesser toe from the MTPJ to (andincluding) the distal phalangeal jointb. It receives contributions from the:i. EDL tendonii. Plantar and dorsal interossei tendonsiii. Tendons of the lumbricalesiv. EDB tendon (toes 2-4)v. Deep process of the plantar aponeurosisc. The hood apparatus provides a means for the EDL to extend the proximalphalanx without having a direct connection to it by controlling the actions of



the interossei and lumbricales musclesd. The hood apparatus is made up of 2 parts that are continuous with eachother, the sling and winge. The sling is more proximal, and the wing is more distalf. The action of the lumbricales and interossei of the phalanges is intergratedwith that of the EDL by the extensor apparatus attachments

Arthrology1. Tibiofibular joints: The tibia and fibula are joined in 3 areas proximal,distal, and crural interosseous

a. Proximal tibiofibular joint: A plane synovial joint between the facet on themedial aspect of the head of the fibula and the fibula facet on the lateralcondyle of the tibiai. Anterior superior tibiofibular ligamentii. Posterior superior tibiofibular ligamentb. Distal tibiofibular joint: A syndesmosis between the distal ends of the tibia

and fibulai. Interosseous tibiofibular ligamentii. Anterior inferior tibiofibular ligamentiii. Posterior inferior tibiofibular ligament

c. Crural interosseous membrane (middle tibiofibular joint): A sheet of fibrousconnective tissue between the interosseous borders of the tibia and fibulad. Functional anatomy of the tibiofibular joint:i. Motion is limited to slight rotation and gliding

ii. In ankle dorsiflexion, the talus is forced into the ankle mortise, separatingthe 2 bones (adding stability). Distal separation is limited by the fibroussyndesmosis of the distal joint and the crural interosseous membrane2. Ankle joint (talocrural): A modified ginglymus or hinged synovial joint.In addition to dorsiflexion/plantarflexion, a small amount of abduction/adduction as well as eversion/inversiona. Articular surfaces (superior concavity): The ankle mortisei. Distal end of the tibia (tibial plafond): wider anteriorly (produces stability instance)ii. Comma shaped facet on the lateral surface of the medial malleolusiii. Triangular shaped facet on the medial surface of the lateral malleolus iv

Anterior tibiofibular ligamentb. Medial collateral ligaments (deltoid): Fans out into one deep and 3superficial portions, with attachments to the talus, calcaneus, and naviculari. Anterior tibiofibular ligament: Deepestii. Posterior tibiofibular ligamentiii. Tibiocalcaneal ligament: Blends with the spring ligamentiv. Tibionavicular ligamentc. Lateral collateral ligaments: 3 subdivisionsi. Anterior talofibular ligament: Intracapsular, blends with the ankle joint





d. Fibrous capsule: Surrounds the ankle joint and is attached to the margins

of the articular surfaces



e. Synovial capsular membrane:i.Closely attached to the fibrous capsular membrane medially and laterallyii. Bulges are seen at the anterior tibiofibular ligament and parts of the lateralligamentiii. Synovial membrane is exposed near the medial malleolusiv. Loose fold of synovial membrane is present in the ankle mortise betweenthe articulation of the lateral malleolus and inferior surface of the tibia(allows for accommodation of the talar dome) f. Functional anatomy:i. Oblique axis of motion running from posteroinferolaterally toanterosuperomedially (pronatory/supinatory)ii. The axis changes as the foot moves with dorsiflexion and plantarflexion

3. Subtalar joint (anatomic): A modified ginglymus joint

NOTE* The "anatomic" STJ is defined as the synovial articulation between the posterior talar facet on the superior surface of the calcaneus and the posterior calcaneal facet on the inferior surface on the body of the talus. The

'functional" STJ includes the middle and anterior facetsThe anterior and middle facets of the calcaneus are part of thetalocalcaneonavicular, a separate Synovial joint.



a. Articular areas: The posterior facets are roughly triangular in shape. Thearticular surface of the the talus is concave, and the calcaneal surface isconvex alond its longitudinal axisb. Sinus tarsi: Formed by the articulation of the sulcus calcanei between theposterior and and anterior-middle facets of the calcaneus and the sulcus talion the inferior surface of the talar neck. It is wider laterallyc. Fibrous capsule: Completely surrounds the joint and reinforced by capsularligamentsd. Capsular ligaments:i. Posterior calcaneal ligament: "Y" shaped. Medial band forms a roof over thegroove for the FHL tendonii. Lateral talocalcaneal ligamentiii. Medial talocalcaneal ligamentiv. Anterior talocalcaneal ligamentv. Interosseous talocalcaneal ligament (ligament of the tarsal canal): Locatedwithin the tarsal canal and strengthens the STJ posteriorlyvi. Cervical ligament: Found laterally in the sinus tarsi, and resists supinationof the STJe. Functional anatomy:

• Most important STJ supinators are the tibialis anterior and tibialis

posterior• Most important pronators are the peroneus longus and peroneus brevis

• The long axis of the posterior talar facet of the calcaneus is at an angleof about 40° to the long axis to the foot

4. Talocalcaneonavicular joint: The head of the talus fits into a socketformed by the posterior articular surface of the navicular and the anteriorand middle talar articular facets of the calcaneus, as well as the plantarcalcaneonavicular ligament



a. Classification: A modified condylar joint (capable of gliding and rotatorymotion)b. Articular surfaces:i. Head of talus:

• Convex in all directionsii. Acetabulum pedis (joint socket):

•

Anteroinferior portion: Concave in all directions, and formed by theposterior surface of the navicular

• Posterior portion: Formed by the anterior and middle articular facets of the calcaneus

• Inferomedial portion: Formed by the plantar calcaneonavicular ligament

c. Capsular ligaments:i. Dorsal talonavicular ligamentii. Plantar calcaneonavicular ligament (spring): Important in supporting thetalar headiii. Calcaneonavicular portion of the bifurcate ligament: "Y" shaped with thestem attached to the calcaneus and one arm attached to the cuboid and theother arm to the naviculard. Synovial membrane: Lines the fibrous capsulee. Functional anatomy:i. Some gliding and rotational movements are possible, but the TCN jointcannot act independentlyii. Any motion at the STJ causes motion in the TCN joint. Additionally, motionbetween the talus and navicular also involves the C-C joint

5. Calcaneocuboid joint: Formed by the articulation of the posteriorsurface of the cuboid and the anterior surface of the calcaneusa. Classification: A saddle-shaped synovial jointb. Fibrous capsule: Surrounds the entire joint and has 3 capsular ligamentsi. Dorsal calcaneonavicular ligamentii. Lateral calcaneocuboid ligamentiii. Calcaneocuboid portion of the bifurcate ligamentc. Extracapsular ligaments:i. Long plantar ligament (long calcaneocuboid):

• Superficial and deep fibers

• Longest ligament in the foot

• Posterior fibers attached to plantar surface of the calcaneus and runsdistally to bases of metatarsals 2-5d. Synovial capsule: Lines the entire jointe. Functional anatomy: Has two axes of rotationi. One axis through the calcaneal process

NOTE* The articular area of the talar head is greater than the socket, and asa result, in normal anatomic position, the head protrudes slightly dorsally at the joint





b. Fibrous capsule: Each T-M synovial joint has its own capsulec. Capsular ligaments:i. Dorsal tarsometatarsal ligamentsii. Plantar tarsometatarsal ligamentsd. Inferior surface of the medial cuneiform to the base of the 1st metatarsali. Interosseous tarsometatarsal ligaments (attach the cuneiforms or cuboid tothe metatarsal bases)

• Medial interosseous ligament (LisFranc's ligament): Strongest, runsfrom the lateral surface of the medial cuneiform to medial surface of the 2ndmetatarsal base, and is important for stability of the T-M joint

• Intermediate interosseous ligament (2nd)

• Lateral interosseous ligament (3rd)

e. Function: Slight gliding motion of the lesser metatarsal on their adjacenttarsal bones

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