39 - Exostosis and Symptomatic Ossicles

Question 1

Medial foot prominences

Answer 1

Soft tissue: bursitis, tendonitis, neuritis, fibroma, granuloma, ganglionic cyst
o Play a big role in what type of symptoms occur
o Bursitis = inflammation of the bursa
o This will vary depending on the location and what anatomy is there
o Sometimes both bony and soft tissue structures will need to be addressed

Bone: arthritis, periosteal reaction, osteoma, congenital deformity, patho-mechanical deformity

Question 2

Talar prominence - medial aspect of the foot

Answer 2

• This is caused by PRONATION, foot “splays out”
• If you have supination, it “tucks” the talar head
  in and makes the talus less prominent
• Can also be caused by Charcot or flat foot
  in severe cases (radiograph on slides is Charcot)
• Prominence produced by the head of the talus
• Prominence is exaggerated with STJ pronation
• Prominence is reduced with STJ supination

Question 3

Navicular prominences

Answer 3

• The prominence is located just distal to a possible talar head prominence, which is virtually unaffected by subtalar joint motion
• With or without the presence of an accessory navicular
• The accessory navicular is the MOST COMMON accessory ossicle***
• Becomes apparent at age 9-11 radiographically
• THREE TYPICAL PRESENTATIONS

Question 4

Type I navicular prominence

Answer 4

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

Question 5

Type I navicular prominence

Answer 5

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

Question 6

Type I navicular prominence

Answer 6

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

Question 7

Conservative treatment for a talar prominence

Answer 7

o Functional orthoses (MOST COMMON)
o AFO
o Shoe modification
o Steroid injection (avoid tendinous areas due to tendon weakening and rupture)
o Steroids
o NSAIDs (calm down inflammation)
o Initially offloading and resting the foot is good to get swelling down before initiating the conservative treatment options (like NSAIDS), then you can assess the next step

Question 8

Surgical treatmet for a talar prominence

Answer 8

o Arthrodesis of the subtalar or midtarsal joint or both, tend to be the primary procedure of choice
o Adjunctive procedures may need to be considered: TN fusion, CC fusion, PCDO

Question 9

Conservative treatment for navicular prominence

Answer 9

o Initial treatment may consist of immobilization, Nsaids, & non-weight bearing
o Shoe modification and shielding the prominence
o If secondary to severe pronation, functional orthosis may reduce symptoms
o AFO

Question 10

Surgery for type I navicular prominence

Answer 10

o Involves removal of the ossicle from the tendon which is achieved by:
o Tendon splitting approach
o Reflection of the posterior tibialis from the talonavicular joint capsule & then removing the ossicle – if the posterior tibialis is compromised, may need to fuse joint
o May need to bring C-arm into the OR to locate the ossicle ***

Question 11

Surgery for type II navicular prominence

Answer 11

o Adequate osseous exposure so that the entire tuberosity is visualized
o Radiolucent zone not visualized
o Intro-op (Need to probe the area to find the mobile piece of bone)
o Use radiographs to isolate location]
o Excision of the fragment is performed
o May result in weakening of the tendon and capsule

Question 12

Surgery for type III navicular prominence

Answer 12

o Requires talonavicular joint exposure
o The subtalar joint should be supinated in order to protect the articular surface of the talar head
o Resection of the tuberosity is performed following the normal contour of the bone

Question 13

Dorsal bossing

Answer 13

COMMONLY CAUSES PAIN

• Dorsal bossing of the 1st tarsometatarsal joint is a common acquired disorder of the foot
• Presentation at the 1st met-cuneiform joint may be a medial or dorsal prominence
• ***May be secondary to hallux limitus or hallux valgus = MOST COMMON (pronating foot)
• Another etiological agent may be Charcot arthropathy

Question 14

Classification of dorsal bossing

** KNOW ALL OF THESE**

Answer 14

• Type I
• Type II
• Type III
• Type IV
• Type V

Question 15

Type I dorsal bossing

Answer 15

o Dorsal exostosis formation located at the 1st met. cuneiform
o Secondary to intermittent compression of bone
o Etiology: forefoot valgus plantarflexed 1st ray (flexible or semirigid)
o NOTE: no real arthritic changes are present here

Question 16

Type II dorsal bossing

Answer 16

o Characterized by 1st-met cuneiform joint exostosis located circumferentially (dorsal, plantar, medial) associated arthritic component of the joint itself
o Secondary to a history of trauma – patient may have a history of arthritis
o NOTE: ARTHRITIC CHANGES ARE PRESENT

Question 17

Type III dorsal bossing

Answer 17

o Characterized by dorsal exostosis of the 1st met.-cuneiform

Angular malalignment present:

• Dorsiflexed (tendon imbalance, hallux limitus)
• Plantarflexed (pes cavus)
• Adducted (hallux abducto valgus)

Question 18

Type IV dorsal bossing

Answer 18

o Characterized by dorsal exostosis of 1st met.-cuneiform and also involves Lis franc’s joint
o Associated arthritis within the tarsometatarsal joint
o Most common cause is Charcot arthropathy or any previous trauma

Question 19

Type V dorsal bossing

Answer 19

o Characterized by a pseudo exostosis at the 1st met-cuneiform – there is no actual exostosis – the deformity is secondary to pes cavus foot
o The position of the forefoot will accentuate the joint, resulting in shoe irritation

Question 20

Accessory bones of the foot

Answer 20

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

Common symptomatic ossicles
o	Os vesalianum
o	Os peroneus
o	Os trigonum 
o	Os tibiale externum

Question 21

Os vesalianum

Answer 21

• Located at the base of the 5th metatarsal
• Pain is usually characteristic in patients with an extremely large tuberosity
• In children pain tends to be related to activity
• In adults pain tends to be related to shoe gear irritation
• NEED to get contralateral x-rays

Question 22

Treatment for os vesalianum

Answer 22

• Initiate conservative care (shoe gear modification, etc.)
• Surgical intervention (use C-arm)
• Excision of fragment
• Possible re-attachment of peroneus brevis

Question 23

Os peroneus

Answer 23

• Accessory bone located inferior to the peroneal groove of the cuboid.
• Encompassed within the tendon of the peroneus longus
• Actually considered a sesamoid
• Functions to assist movement of the peroneus longus (acts as a fulcrum) - REMEMBER – sesamoids ALTER FUNCTION of the tendon ***
• Usually is not symptomatic

Question 24

Treatment of os peroneus

Answer 24

• Excision of ossicle
• Tendon repair
• Possible graft
• Tendon transfer

Question 25

Os trigonum

Answer 25

• Accessory boney process located on the lateral process of the posterior aspect of the talus
• Usually unites or fuses with the talus by age 18
• Irritation is usually caused by the flexor hallucis longus
• Secondary to prolonged activity, trauma

Question 26

Os subfibularae

Answer 26

Located under fibula

Question 27

Os subtibialae

Answer 27

Located under tibia

Question 28

Accessory sesamoids

Answer 28

• Located sub 2nd through 5th metatarsals
• Located within the long flexor tendons of each of these digits
• Never seen these sesamoids becoming problematic

Question 29

CASE STUDY I

Answer 29

• 32 year old male presents with a chief complaint of a painful left ankle of 6 months duration
• PMHx: HTN, ankle sprains
• Meds: lisinopril, advil
• NKDA
• Vascular: DP & PT +2/4
• Neuro: epicritic sensation intact
• Musculoskeletal: +5/5 extrinsic muscles , no talar tilt, no ankle instability
• Derm: no erythema, +edema lateral ankle

Treatment:
o Immobilization in Cam boot 4 weeks
o NSAIDs
o Physical therapy

Follow-up

• Patient returns 1 year later, with a new injury to the same location
• Conservative care initiated, patient unresponsive because they were incorporated within the capsular structures

Surgical intervention:
o Removal of accessory ossicle
o Brostrom of the lateral ankle (C-shaped incision over lateral malleolus)

No problems with ossicle following surgical repair

Question 30

CASE STUDY II

Answer 30

• 47 year old male with a chronic ulcer sub IPJ
• Approx. 2cm in diameter
• PMHx: DM w/ neuropathy, HTN, Hyperlipidemia
• Radiographs: Demonstrate an accessory ossicle sub IPJ
• Needed to be treated with surgical intervention
• Needed to surgically stabilize the toe because removal of ossicle resulted in instability
• Needed a flap to cover wound
• The area where the ulceration was eventually healed