Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Foot and Ankle Anatomy and Examination

Basics
Description
  • The major function of the foot and ankle is to allow even stress distribution between the foot and lower extremity during walking and running.
  • For adequate function, the foot must be plantigrade (i.e., rest evenly flat on the ground) and painless.
  • The muscles that control foot and ankle function include extrinsic (originating outside the foot) and intrinsic (originating within the foot) groups.
  • Extrinsic muscles: 4 groups of muscles and tendons (dorsiflexors, evertors, plantarflexors, and invertors):
    • Dorsiflexors:
      • Extensor tendons: Tibialis anterior, extensor digitorum longus, and extensor hallucis longus
      • Easily palpable crossing the ankle; can be lacerated by sharp objects
    • Evertors:
      • Peroneus longus and brevis
      • Situated on the lateral aspect of the leg
      • Tendons run posterior to the lateral malleolus.
      • Injury to tendon sheath can cause tendon subluxation over malleolus.
    • Plantarflexors and invertors:
      • Travel posteromedial to the ankle
      • The PTT, the main invertor, is prone to tenosynovitis and rupture in the adult, a condition leading to acquired flatfoot.
      • The extrinsic toe flexors include the flexor digitorum longus and flexor hallucis longus.
  • Intrinsic foot muscles include 1 dorsal layer and three plantar layers, all of which help to control toe motion.
  • An imbalance between extrinsic and intrinsic muscle strength can contribute to toe deformities such as mallet toes, claw toes, and hammer toes.
  • Foot and ankle bones are easily palpable.
    • The ankle joint:
      • Consists of the articulation between the distal tibia, fibula, and talus
      • Predominantly allows plantar- (40°) and dorsiflexion (20°)
      • Is supported by several ligaments:
        • Anterior and posterior tibiofibular ligaments stabilize the syndesmosis; if injured, high ankle sprain results.
        • The superficial and deep deltoid ligaments connect the medial malleolus to the hindfoot.
        • The ATFL, CFL, and PTFL support the lateral ankle; the ATFL commonly is injured in inversion ankle sprains.
    • The hindfoot:
      • Consists of the talus and calcaneus, which articulate at the subtalar joint
      • Allows inversion and eversion (40° arc of motion), which is important when walking on uneven surfaces.
      • The talus is covered almost completely with cartilage; its blood supply frequently is disrupted during subtalar dislocation or talar fracture, leading to AVN.
      • The calcaneus acts as a shock absorber; axial loading from a fall is a common mechanism of calcaneal fracture.
    • The midfoot:
      • Consists of 2 rows of bones:
        • Proximally, the navicular and the cuboid articulate with the hindfoot through the Chopart joint.
        • Distally, the 3 cuneiform bones and cuboid articulate with the metatarsals via the tarsometatarsal (Lisfranc) joint.
      • Ligaments attach all but the 1st and 2nd metatarsal bases to the adjacent metatarsals.
      • The strong Lisfranc ligament connects the 2nd metatarsal to the medial cuneiform.
    • The forefoot consists of the 5 metatarsals and 14 phalanges (2 phalanges in the hallux and 3 in each of the lesser toes).
  • The gait cycle consists of the stance and swing phases.
    • Stance phase: Heel strike, foot flat, toe-off:
      • Heel strike:
        • Tibialis anterior and long toe extensors are active.
        • The foot is pronated, which unlocks the Chopart joint, makes the midfoot flexible, and helps with energy absorption and load acceptance.
      • Foot flat:
        • Tibialis posterior and peroneals are active.
        • The leg rotates externally, which supinates and locks the midfoot and stabilizes the foot for weightbearing.
      • Toe-off:
        • Gastrocnemius-soleus complex is active.
        • Dorsiflexion of the toes tightens the plantar fascia (windlass mechanism), increasing the midfoot arch and locking the midfoot, which allows the foot to act as a lever during push-off.
    • Swing phase: Tibialis anterior and long toe extensors are active.
Diagnosis
Signs and Symptoms
History
  • Address the patient’s symptoms:
    • Mechanism of injury for acute trauma
    • Pain: Severity, location, quality, radiation, and alleviating/aggravating factors
    • Mechanical symptoms (locking/catching) and instability
    • Neurologic symptoms: Numbness, dysesthesia, paresthesias
  • Pertinent medical and surgical history:
    • Diabetes, neurologic disorders, vascular disease, inflammatory arthritides
    • Previous foot or leg surgery
  • Shoe wear
  • Occupation
  • Sport or recreational activities
Physical Exam
  • Physical examination findings of the involved extremity should be compared with those of the contralateral extremity.
  • Patient in standing position:
    • Evaluate the patient’s gait pattern and stance to assess ankle/foot alignment.
      • Viewed from behind, alignment of the hindfoot can be determined as varus, neutral, or valgus.
      • More lateral toes seen on the affected side than on the uninvolved foot is called the too-many-toes sign, and implies the presence of flatfoot with arch collapse and midfoot abduction.
      • Assess gait pattern for steppage (dropfoot), circumduction, scissoring, or antalgia.
    • Double- and single-limb heel rises allow for evaluation of dynamic foot function, including tibialis posterior strength, arch reconstitution, and balance.
  • Patient in seated position:
    • Vascular assessment:
      • Palpate the dorsalis pedis on the dorsum of the foot lateral to extensor hallucis longus, and the posterior tibial pulse behind the medial malleolus.
      • Examine for venous stasis, pitting edema.
    • Sensory and neurologic examination:
      • Dorsal foot (superficial peroneal nerve)
      • 1st dorsal web space (deep peroneal nerve)
      • Medial border of foot (saphenous nerve)
      • Lateral border of foot (sural nerve)
      • Plantar foot (tibial nerve)
      • Patient’s ability to feel the 5.07 Semmes- Weinstein monofilament on the plantar foot correlates with having protective sensation.
      • Check reflexes and evaluate for Babinski sign and clonus.
    • Motor examination: Test strength and palpate tendons.
      • Ankle dorsiflexion (tibialis anterior)
      • Ankle plantarflexion (gastrocnemius-soleus complex)
      • Eversion (peroneals)
      • Inversion in plantarflexion (tibialis posterior)
      • Flexion and extension of the distal phalanx of the great toe (flexor and extensor hallucis longus); evaluate active and passive motion.
      • Ankle plantar and dorsiflexion, with any hindfoot deformity passively corrected
      • Hindfoot inversion and eversion to assess subtalar motion
      • Chopart joint abduction/adduction while stabilizing the hindfoot
      • Assess Lisfranc joint with palpation and plantar- and dorsiflexion of the tarsometatarsal joints.
      • Assess motion at the MTP and toe joints.
    • Palpation:
      • Medial and lateral malleoli (fracture)
      • Ankle joint for tenderness, effusion (osteochondral lesion, synovitis)
      • PTT along its course posterior to the medial malleolus to insertion on navicular (tendinitis)
      • Navicular tuberosity ~2 cm distal and plantar to medial malleolus (accessory navicular, stress fracture, talonavicular pathology)
      • Achilles tendon and retrocalcaneal bursa along the posterior ankle and hindfoot for defects, nodules, thickening, swelling, and tenderness (tendinitis, tear)
      • Peroneal tendons posterior to the lateral malleolus to the brevis insertion on the base of the 5th metatarsal, and where the longus passes through the plantar groove of the cuboid (tendinitis, 5th metatarsal base fracture); also assess for tendon subluxation with foot circumduction.
      • Sinus tarsi ~1 cm distal to lateral malleolus (subtalar joint pathology)
      • Tenderness along the tip of medial or lateral malleolus (ligament sprain)
      • Tenderness between the tibia and fibula proximal to the ankle joint (syndesmosis injury)
      • Palpate the plantar fascia, originating at the base of the heel (plantar fasciitis, especially if tenderness is accentuated with toe dorsiflexion).
      • Base of the 2nd metatarsal (Lisfranc injury)
      • Plantar MTP joint of the great toe (sesamoiditis, sesamoid fracture)
      • Plantar lesser toe MTP joints (metatarsalgia)
      • Metatarsal interspaces (neuroma)
  • Specific tests and examinations:
    • Anterior drawer test (ankle instability):
      • Try to sublux the talus anteriorly from tibia.
      • Foot dorsiflexed stresses the ATFL.
    • Thompson test:
      • With the patient in the prone position, squeeze the posterior calf.
      • Loss of foot plantarflexion implies disruption of the Achilles tendon.
    • Coleman block test:
      • Helps determine if varus hindfoot deformity is flexible or rigid
      • The patient stands on a block with the 1st ray unsupported; if the hindfoot deformity corrects, then it is flexible.
    • Lesser toe deformities:
      • Assess the location of the calluses.
      • Assess if the deformity is correctable or not (flexible versus rigid).
      • Assess MTP joint stability with modified drawer test, trying to sublux and reduce proximal phalanx on metatarsal head.
    • Hallux valgus:
      • Assess the location of the calluses.
      • Assess tenderness over the medial eminence.
      • Assess MTP motion with the deformity corrected.
      • Assess for hypermobility of the 1st tarsometatarsal joint by stabilizing the lateral foot and attempting to translate the 1st metatarsal plantar and dorsal.
      • Assess for lesser toe deformities that could contribute to symptoms.
Tests
Lab
  • If concern for infection exists, consider obtaining ESR, C-reactive protein, and white blood cell count.
  • Joint aspirations should be sent for cell count, differential, Gram stain, evaluation for crystals, and culture.
Imaging
  • Plain radiographs:
    • If the patient has acute trauma, and fracture or dislocation is being considered, obtain nonweightbearing films.
    • If the patient is able to stand, then weightbearing radiographs should be obtained.
      • Standing radiographs show bony relationships in the physiologic state and are much more likely to reveal foot disorders than are nonweightbearing views.
    • Stress view radiographs help to evaluate indirectly the integrity of ligamentous structures.
  • CT is helpful for identifying and delineating fracture patterns and bony pathology, especially of the midfoot and hindfoot.
  • MRI helps to show soft-tissue disorders, including tendon and ligament pathology, soft-tissue lesions, subtle fractures, and infection.
  • Technetium-99m bone scans:
    • Useful for localizing problems when the complaint is vague or multifocal
    • Can help locate stress fractures, tumors, and other pathology
  • Indium-labeled white blood cell scans:
    • Useful for identifying infection
    • Combined with a marrow scan, can help differentiate infection and Charcot arthropathy
Miscellaneous
FAQ
Q: What anatomic structure causes a Tillaux fracture?
A: In adolescents, fusion of the distal tibial physis begins centrally and progresses medially. The lateral portion of the physis is the last area to fuse. The ATFL attaches to this part of the tibia. A twisting injury to the ankle at this stage of development can cause this ligament to avulse the unfused segment of tibial physis, with extension of the fracture into the ankle joint.
 
Q: What is the main blood supply to the talar body?
A: The artery of the tarsal canal, a branch of the tibial artery, is the main blood supply to the talar body. Branches of the dorsalis pedis and peroneal artery also provide limited blood supply to the talus. Injury to this vascular network can cause AVN of the talar body.

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