Foot/Ankle/Lower leg Flashcards
What do you call the common accessory bone of the talus?
why does it form?
Os trigonum.
It sits posterior to the talus on the lateral foot radiograph and represents a failure of fusion of the lateral tubercle of the posterior process.
It is estimated to be present in ~7% of adults.
The ossicle usually forms between 7-13 years of age and fuses with the talus in a majority of patients, otherwise persisting as an os trigonum.

What attaches to the posterior process of the talus?
Posterior talofibular ligament. It attaches to the lateral tubercle of the posterior process

What runs under the posterior process of the talus?
Tendon of FHL - between lateral and medical tubercles

What structure wraps directly under the sustentaculum?
FHL tendon
What runs in the sinus tarsi? Name all structures.
- Interosseous talocalcaneal ligament
- cervical ligament
- medial, intermediate and lateral roots of the inferior extensor retinaculum
- artery of tarsal sinus
(artery of tarsal canal runs in the canal, which is the continuation of the sinus)

What parts of the talus articulate with the calcaneus?
Anterior, middle and posterior articular facets

Describe the blood supply to the talus. What is the main supply?
- Main blood supply is from the posterior tibial artery through the deltoid branches
- Peroneal artery has the least contribution
All 3 terminal arteries have a contribution though:
- posterior tibial a. (MAIN SUPPLY) - deltoid branch to BODY, artery of tarsal CANAL
- Anterior tibial/dorsalis pedis aa.–branch to dorsal head/neck, contributes to artery of tarsal SINUS
- perforating peroneal aa. - contributes to artery of tarsal SINUS - supply head/neck, lateral body

What is the Lisfranc ligament?
Interosseous portion of the oblique ligament from medial cuneiform to 2nd MT base
3 components of the lisfranc ligament complex:
Dorsal - IO - Plantar
IO is the strongest.
Fails - dorsal, plantar, then IO

What are the components of the Lisfranc ligament? which is the strongest one? weakest?
Dorsal (weakest), plantar and interosseous (strongest)
What is the Chopart joint?
The midtarsal joint, comprising the talonavicular & Calcaneocuboid joints
What are the ligamentous components of the ankle syndesmosis?
AITFL
PITFL
Interosseous membrane (IoM)
Interosseous ligament (IoL)
Inferior transverse ligament (ITL) (really just the distal fibrocartilagenous component of the PITFL)
What are the components of the deltoid ligaments of the ankle?
Superficial: - Tibionavicular & Tibiocalcaneal
Deep: - Anterior & posterior tibiotalar

What is an Os Navicular? What are the 3 types?
Accessory navicular.
Type 1: Sesamoid within the distal part of the tendon
Type 2: Attachment to the posterior tibialis tendon, separated by synchondrosis
type 3: enlargement of navicular

What benign structure can often be confused with a Lisfranc Injury?
Os intermetatarseum

What are the plantar layers of the foot?
4 layers:
1st:
- Abductor hallucis brevis
- Abductor digiti minimi
- Flexor digitorum brevis
- plantar fascia
2nd:
- Quadratus plantae
- Lumbricals
- FHL tendon
- FDL tendon
3rd:
- Flexor hallucis brevis
- Flexor digiti minimi brevis
- Adductor hallucis
4th:
- Dorsal interossei
- Plantar interossei
- (also tendons of peroneus longus and tib post)
1st layer (from medial to lateral):
Abductor Hallucis (medial)
Flexor Digitorum Brevis (Middle)
Abductor digiti minimi (lateral)
Plantar fascia
Specifics:
flexor digitorum brevis (=FDS) - medial plantar nerve. Flexes toes in any ankle position
Arises from the medial calcaneus and inserts into the sides of each middle phalanx excluding the great toe.
ABductor Hallucis - medial plantar nerve, great toe abduction
Arises from the medial calcaneus and flexor retinaculum and inserts into the medial base of the proximal first phalanx
ABductor digiti minimi - lateral plantar nerve. Abducts 5th toe.
Arises from the medial and lateral processes of the calcaneus deep to Flexor Dig Brevis. Inserts into the lateral side of the proximal phalanx of 5th toe.
2nd layer:
- consists of the long flexors
Tendon of Flexor digitorum longus (medial)
Tendon of Flexor hallucis longus (adjacent but crosses underneath to run most medial)
Quadratus planae AKA Flexor accessorius (Two heads coming off either side of the calcaneus)
Lumbricals (arises from FDL similar to the hand)
Specifics
Tendon of FDL (tibial nerve) enters the foot medial to FHL but then passes over it. It then splits into 4 and receives insertion from Flexor Accesorius. The tendons pass deep to FDB and give off the lumbricals (medially). Each tendon then enters the fibrous sheath of the lateral 4 toes each perforating the FDB to insert into the base of the distal phalanx (also medially)
Tendon of Flexor Hallucis Longus - Tibial nerve. Passes forward medial like a bowstring beneath the medial longitudinal arch. It is passed over by FDL and it gives off two strong slips to the medial two digits. It lies in a groove between two small sesamoid bones beneath the head of the first metatarsal and inserts into the distal phalanx of the large tow. It is invested by a synovial sheath throughout its whole course in the foot.
- Quadratus plantae (Flexor Accessorius) - lateral plantar nerve. Arises from the medial and lateral aspects of the calcaneus. The posterior part of the long plantar ligament is visible through the two heads. It converges and then inserts into the tendon FDL before it splits. Allows for flexion of the toes with the foot plantar flexed.
Lumbricals - arise from the tendon of FDL (like the lumbricals in the hand arise from FDS). Unlike their counterpart in the hand, they pass medially to the digit into which they insert. The tendons lie on the plantar aspect of the deep transverse metatarsal ligaments (similar to the hand lumbricals which lie volarly). They insert into the extensor expansions.
The medial (1st) lumbrical is unipennate with origin from the first tendon of FDL and attaches to the second digit medially. It is innervated by the medial plantar nerve
The lateral 3 lumbricals are all bipennate arising from both adjacent tendons and inserting medially into their respective extensor expansions
They all function to extend the interphalangeal joints while FDL are flexing the toes
*** Lumbricals innervated by the medial plantar and median nerve are Unipennate
*** Lumbricals innervated by the lateral plantar and ulnar nerve are multipennate.
3rd layer: Consists of 3 muscles. 2 act on big toe, one on small toe. Confined to the metatarsal area.
Flexor Hallucis Brevis (medial)
Adductor Hallucis brevis (middle)
Flexor Digiti Minimi Brevis (lateral)
Specifics
- Flexor hallucis brevis - medial plantar nerve. Has common origin but splits into two heads. Arises from the cuboid and the lateral cuneiform. It splits into two muscle bellies which are inserted BY WAY OF SESAMOID BONE into the medial and lateral sides of the base of the plantar, proximal great toe.
Adductor Hallucis brevis - Lateral plantar nerve. ADDucts and functions to maintain the transverse arch. Has two heads, Oblique and Transverse. The oblique head is large and wide, it arises from the long plantar ligament and the bases of the 2nd thru fourth metatarsals. The Transverse head is slender and has no bony origin. It arises from the deep transverse ligament and the plantar ligaments of the lateral MTP joints. The two heads unite before insertion into the proximal phalanx of the big toe.
Flexor digiti minimi Brevis - lateral plantar nerve. Arises from the base of the 5th MT and the adjoining fibrous peroneus longus. Lies along the 5th MT bone and inserts into the base of the proximal phalanx medially to the insertion of Abductor digiti minimi
4th layer: Consists of the Interossei
Interossei - Also follow the DAB and PAD rule, all are innervated by the lateral plantar nerve (similar to the ulnar in the hand). The important thing to remember is that the longitudinal axis of the foot is shifted medially as compared to the hand such that the axis lies thru the 2nd digit (not the third like the hand).
Like the hand the 3! plantar interossei are smaller and arise from the bone on the toe on which they act. The bulkier 4! dorsal interossei arise from 2 heads from the 2 MTs between which it lies.
The 3 plantar interossei adduct towards the second toe. Digits 3,4 and 5 each have a plantar interossei which pass dorsal to the deep transverse metatarsal ligament. The insert into the dorsal expansion as well as the proximal phalanges.
The 4 dorsal interossei abduct away from the second toe. As such, the 2nd dorsal interossei attaches to the medial second toe. The second to the lateral second toe. The third to the lateral third toe and the fourth to the lateral fourth toe. The also attach to the dorsal expansion as well as the proximal phalanges.
ACTION - their AD/ABduction function is not really important, more so is their ability to assist the lumbricals in extending the IP joints and flexing the MTP joints.
What are the muscles in the dorsal intrinsic compartment of the foot?
Extensor hallucis brevis (deep peroneal nn)
Extensor digitorum brevis (deep peroneal nn)

What is the Master Knot of Henry? Why is it important?
which of the two structures is dorsal/plantar?

Crossing between the FHL and FDL in the foot
Important as dividing it allows access to the deeper layers of the foot and because it can be a site of graft harvest (either FHL or FDL tendon transfers)
FHL is dorsal to FDL which is plantar
What are the compartments of the foot and their key structures?
Compartments:
- Calcaneal - QP, PostTib nn and aa, Med/Lat plantar nn
- Adductor - AD Hallucis
- Interossei - 4 interossei
- Medial - FHB, Abd Hallucis
- Lateral - ADM, FDM
- Superficial - FDL, lumbricals, FDB
HINDFOOT
1) Calcaneal
Quadratus plantae
Posterior tibial nerve, aa, vv
Lateral plantar nerve, aa, vv
medial plantar nn, aa,vv (sometimes in the superficial)
FOREFOOT
2) Interosseous x 4
interossei
3) Adductor
adductor hallucis
4,5,and 6 are FULL LENGTH
4) Medial
FHB
Abductor hallucis
5) Lateral
Abductor Digiti Minimi
Flexor Digiti Minimi
6) Superficial
flexor digitorum brevis
FDL
lumbricals
possibly the medial plantar nerve

What are the borders and contents of the tarsal tunnel?
Floor: talus, Calcaneus (sustentaculum tali, medial wall)
Roof: Lacinate ligament (flexor retinaculum)
Contents: TP, FDL, PT artery, vein, Tibial nerve, FHL “Tom Dick And Very Nervous Harry”
What is Baxter’s Nerve? What is it’s clinical significance?
What layer does it run in?
What mm does it innervate?
1st branch of the lateral plantar nerve It runs obliquely plantarly on quadratus plantae It’s a cause of medial heel pain if impinged (dDx of plantar fascitis)
Runs between layer 1 and 2 FDB (1) and QP (2)
Innervates ADM

Where does the Plantaris tendon insert? be specific.
Medial to the achilles tendon. It may be a part of the achilles tendon but it will still be on the medial side
Origin: posterolateral lateral femoral condyle.
What structures combine to form the Sural Nerve?
Medial and lateral sural cutaneous nerves
Lateral: branch of common peroneal nerve
Medial: branch of tibial nerve
What does the Sural nerve run with? On which side is the nerve?
Runs with short saphenous vein and it is lateral to it
Where does the superficial peroneal nerve pierce the fascia and become subcutaneous?
10-12cm proximal to the tip of the lateral malleolus



























