39: Exostosis and Ossicles - Bennett

Question 1

talar prominence is exaggerated with …

Answer 1

• prominence is exaggerated with STJ prontation; reduced with STJ supination
• talar prominence = produced by head of talus

Question 2

prominence located just distal to a possible talar head prominence, which is virtually unaffected by subtalar jt motion

Answer 2

navicular prominence

• most commonly due to accessory ossicle
• becomes apparent at age 9-11 radiographically

Question 3

three typical presentations of navicular prominence

Answer 3

type I: Represents a small ossicle just proximal to the navicular tuberosity, classified as a true sesamoid because it is within the tendon

type II: True accessory scaphoid appears radiographically as an extension of the navicular (its connection to the navicular is represented by a radiolucent zone which measures 1-3 mm.) The zone may be fibrous, cartilaginous, fibrocartilaginous, or partially osseous.

type III: Represents a true carnuate navicular or enlarged navicular tuberosity. (May be type II with an osseous bridge.)

Question 4

sugery options for navicular prominence

Answer 4

type I: removal of ossicle from tendon by tendon splitting approach or reflection of post tib from talonavicular jt capsule and then removing ossicle

type II: excision of mobile fragment using adequate osseous exposure and c-arm.

type III: expose talonavicular jt and supinate subtalar jt to protect talar head. resection of tuberosity following normal contour of bone

Question 5

what is dorsal bossing?

Answer 5

acquired disorder of the 1st tarsometatarsal joint

• presentation at 1st met-cuneiform jt may be medial or dorsal prominence
• may be secondary to hallux limitus or hallux valgus
• associated with charcot arthropathy

Question 6

classification of dorsal bossing

Answer 6

type I: dorsal exostosis formation at 1st met cuneiform secondary to intermittent compression of bone. assoc with forefoot valgus plantarflexed 1st ray

type II: 1st met cuneiform exostosis located circumferentially associated with arthritic component. pt may have hx arthritis

type III: dorsal exostosis of 1st met cuneiform with angular malalignment. dorsiflexed = tendon imbalance, hallux limitus; plantarflexed - pes cavus; adducted - hallux abducto valgus

type IV: dorsal exostosis of 1st met cuneiform and involves lis franc’s jt. assoc with arthritis w/i tarsometatarsal jt

type V: pseudo exostosis at 1st met cueniform secondary to pes cavus. results in shoe irritation

Question 7

what is an accessory bone of the foot?

Answer 7

accessory bones of the foot are either normal parts or prominences of the tarsal bones that are abnormally separated from the main structure

Question 8

review picture

Answer 8

review picture

Question 9

ossicle located at base of 5th metatarsal

Answer 9

os vesalianum

Question 10

accessory bone located inferior to peroneal groove of the cuboid

Answer 10

os peroneus

• encompassed w/i tendon of peroneus longus (acutually considered a sesamoid and functions to assist movement of peroneus longus)

Question 11

accessory boney process located on lateral process of posterior aspect of talus

Answer 11

os trigonum

• usually fuses with talus by age 18
• irritated by FHL

Question 12

name

Answer 12

os subfibulare

Question 13

name

Answer 13

os subtibiale

Question 14

name

Answer 14

accessory sesamoids