Updated: 2/12/2019

Osteochondroma & Multiple Hereditary Exostosis

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https://upload.orthobullets.com/topic/8020/images/Case D - dist tibia - xray b - Parsons_moved.png
https://upload.orthobullets.com/topic/8020/images/Case D - dist tibia - CT - Parsons_moved.png
https://upload.orthobullets.com/topic/8020/images/Histology C - cartilage cap - Parsons_moved.png
https://upload.orthobullets.com/topic/8020/images/MHE radial bowing_moved.jpg
https://upload.orthobullets.com/topic/8020/images/Histology A - primary trabeculae - Parsons_moved.png
https://upload.orthobullets.com/topic/8020/images/Histology B - active chondrocyte - Parsons_moved.png
Introduction
  • A benign chondrogenic lesion derived from aberrant cartilage from the perichondral ring that may take the form of 
    • solitary ostoechondroma
    • Multiple Hereditary Exostosis (MHE)
  • Epidemiology
    • incidence
      • the most common benign bone tumor
      • true incidence is unknown as many are asymptomatic
    • demographics
      • common in adolescents and young adults (tested ages: 9, 10, 12, 20, 24)
    • location
      • occur on the surface of the bone and often at sites of tendon insertion
      • common locations include
        • knee (proximal tibia, distal femur) 
        • proximal femur 
        • proximal humerus
        • subungal exostosis (occurs most often at hallux)  
  • Pathophysiology
    • solitary osteochondromas can arise because of
      • Salter-Harris fracture
      • surgery
      • radiation therapy (commonest benign radiation-induced bone tumor)
    • pathoanatomy
      • hamartomatous proliferation of bone and cartilage
      • possibly arise from growth plate cartilage that grows through the cortex by endochondral ossification under the periosteum
      • perichondral node of Ranvier defect may allow growth from the physis to extend from the surface
      • the stalk of the lesion is cortical and cancellous bone formed from ossified cartilage
  • Genetics
    • inheritance
      • autosomal dominant 
    • mutation
      • mutation in EXT gene affects prehypertrophic chondrocytes of growth plate 
      • loss of regulation of Indian hedgehog protein is currently being investigated in the pathogenesis of this disease
  • Associated conditions
    • secondary chondrosarcoma  
      • a malignant condition that results from malignant transformation of a solitary osteochondroma or MHE
      • most commonly a low-grade tumor (90%) 
      • epidemiology
        • occurs in older patients (tested ages: 50)
        • rare in the pediatric population (< 1%)
        • most common location of secondary chondrosarcoma is the pelvis
  • Prognosis
    • risk of malignant transformation is
      • <1% with solitary osteochondroma
      • ~5-10% with MHE develop secondary chondrosarcoma
Multiple Hereditary Exostosis (MHE)
  • Disorder characterized by multiple osteochondromas
  • Pathophysiology
    • mutations affect the prehypertrophic chondrocytes of the physis 
  • Genetics     
    • inheritance
      • autosomal dominant
    • mutation
      • caused by mutations in EXT1, EXT2, and EXT3 genes (tumor suppressor genes) 
      • individuals with the EXT1 mutation have a more severe presentation compared to patients with the EXT2 mutation including
        • higher rate of chondrosarcoma  
        • more exostoses
        • more limb malalignment with less forearm and knee range of motion
        • more pelvic and flatbone involvement
  • Prognosis
    • 5%-10% malignant transformation to chondrosarcoma in patients with MHE 
    • proximal lesions more likely to undergo malignant transformation than distal lesions
Presentation
  • Osteochondroma
    • symptoms
      • most lesions are asymptomatic
      • usually present with painless mass
      • may have mechanical symptoms or symptoms of neurovascular compression
      • they continue to grow until skeletal maturity
    • physical exam
      • palpable mass
      • may have mechanical symptoms secondary to mass
  • Multiple hereditary exostosis (MHE)
    • symptoms
      • limb deformities  
        • most common sites of deformity include the knee, forearm, and ankle  
          • femoral shortening and limb-length discrepancy
          • coxa valga
          • knee valgus (because of shortened fibula) and patellar dislocation
          • ankle valgus (because of shortened fibula) 
        • upper extremity deformities are well tolerated and lead to little loss of function
          • ulnar shortening
          • radial bowing and radial head dislocation
          • may be treated with exostosis excision, ulnar lengthening and radial closing wedge osteotomy
      • joint pain
        • may have symptoms of premature OA
    • physical exam
      • most common deformities include
        • ulnar shortening and radial bowing 
        • radial head dislocation
        • ulnar deviation of the hand
  • Secondary chondrosarcoma 
    • acute onset of pain in adults with MHE should raise suspicion for malignancy
Imaging
  • Radiograph
    • sessile (broad base) or pedunculated (narrow stalk) lesions found on the surface of bones
      • higher risk of malignant degeneration in sessile lesions
      • pedunculated lesions point away from the joint
    • continuity with native tissue
      • cortex of the lesion continuous with cortex of the native bone
      • medullary cavity of lesion continuous with medullary cavity of native bone  
    • cartilage cap is usually radiolucent and involutes at skeletal maturity
    • nodules of metaplastic cartilage can occur within the bursa over cartilage caps
  • CT or MRI
    • used to better characterize lesions
Histology
  • Characteristic histology
    • is similar to a normal physis with
      • cartilage cap consists of hyaline cartilage
      • well defined perichondrium around the cartilage cap
      • normal primary trabeculae 
      • linear clusters of active chondrocytes  
    • may have thin cartilage cap covers lesion 
      • only 2-3 mm thick 
      • thick cartilage caps imply growth but are not a reliable indicator of malignant degeneration in children
      • if cartilage cap becomes thicker as an adult, need to be concerned for chondrosarcoma transformation
Treatment
  • Osteochondromas
    • nonoperative
      • observation alone    
        • indications
          • asymptomatic or minimally symptomatic cases
    • operative
      • marginal resection at base of stalk, including cartilage cap  
        • indications
          • symptomatic lesions
            • lesion may cause inflammation to surrounding tissue
            • lesion may be cosmetically displeasing
        • try to delay surgery until skeletal maturity
  • Multiple hereditary exostosis (MHE)
    • nonoperative
      • observation 
        • indications
          • most patients do not require intervention prior to reaching skeletal maturity
    • operative
      • surgical excision of the osteochondroma
        • indications 
          • dislocated radial heads
          • loss of forearm rotation
        • outcomes
          • simple excision of the osteochondroma optimizes chance of improved motion 
  • Secondary chondrosarcoma
    • operative
      • wide surgical resection 
        • treat same as typical chondrosarcoma
Complications
  • Pseudoaneurysm of the popliteal artery in the popliteal fossa
    • other vascular complications 
      • vascular compression
      • true aneurysm
      • arterial thrombosis
      • venous thrombosis
  • Nerve compression
    • sciatic nerve 
    • common peroneal nerve
      • atrophy of anterior and lateral compartment muscles of the leg
    • radial nerve 
  • Tendon compression
    • lesions around the shoulder can give rise to 
      • rotator cuff impingement
      • subscapularis tear
      • bicipital tendinitis
  • Chondrosarcoma
    • in adults, cartilage cap >2cm is associated with increased chance of malignancy
    • mean age of diagnosis, 31yrs
      • seldom in 1st decade or after 5th decade of life
  • Bursa formation
  • Recurrence
    • 2-5% of cases after resection
    • Short-term X-ray surveillance is adequate unless symptomatic later 
Differentials & Groups
 
Surface lesions
 
May have similar chondrogenic histology
 
Treatment is Observation
Osteochondroma / MHE
 
 
 
Periosteal chondroma
 
 
   
Parosteal osteosarcoma
 
 
   
Periosteal osteosarcoma
 
 
   
Enchondroma / Olliers / Marfuccis    
 
   
Chondrosarcoma    
   
Paget's Disease
 
 
 
 
Enchondroma
 
 
 
 
NOF    
 
 
Fibrous dysplasia
 
 
 
 
Eosinophillic granuloma
 
 
 
 
 
IBank
  Location
Xray
Xray
CT
B. Scan
MRI
MRI
Histo(1)
Case A prox. fibula
 
 
Case B femur
 
 
Case C prox. femur
 
Case D tibia
 
Case E fibula
 
 
 
Case G humerus
 
 
Case H distal femur
 
 
 
 
(1) - histology does not always correspond to case 

 

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Questions (28)
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(OBQ09.71) A 19-year-old male has a heritable condition represented by the radiograph in Figure A. He visits a geneticist and genetic screening reveals he has a EXT 1 gene mutation. Counseling for the patient would include telling the patient that he is more likely to have all of the following compared to a patient carrying the EXT 2 gene mutation EXCEPT: Review Topic

QID: 2884
FIGURES:
1

More exostoses

5%

(65/1222)

2

More limb malalignment

2%

(19/1222)

3

Lower functional knee and elbow range of motion

3%

(40/1222)

4

Lower rate of sarcomatous transformation

82%

(1000/1222)

5

Higher rate of pelvic and flatbone involvement

7%

(89/1222)

ML 2

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(OBQ06.20) All of the following statements regarding hereditary multiple exostosis (HME) are correct EXCEPT? Review Topic

QID: 31
1

It is inherited in an autosomal dominant fashion

2%

(26/1490)

2

Mutations in HME affect the prehypertrophic chondrocytes of the growth plate

6%

(92/1490)

3

It is caused by mutations in either EXT1, EXT2, or EXT3 genes

2%

(30/1490)

4

Radiographically, the exostoses are in direct connection to the medullary cavity

9%

(135/1490)

5

Radiographically, the exostoses grow towards the physis

80%

(1193/1490)

ML 2

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PREFERRED RESPONSE 5
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(OBQ11.173) A 15-year-old boy presents with a painful mass over his great toe. It has been slowly growing over the past year. Clinical photograph and radiograph are shown in Figures A and B. What is the most appropriate treatment? Review Topic

QID: 3596
FIGURES:
1

Observation and shoe wear modification

1%

(11/1945)

2

Amputation

4%

(86/1945)

3

Osteotomy through the base of the tumor and local wound care

88%

(1713/1945)

4

Systemic chemotherapy

0%

(3/1945)

5

Radiotherapy and surgical excision

6%

(120/1945)

ML 1

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(OBQ10.131) An 18-year-old male presents with the radiographs shown in Figures A and B. Genetic work-up reveals a defect in the EXT-1 gene. What is his underlying diagnosis, and which mesenchymal tumor is he most at risk of developing? Review Topic

QID: 3184
FIGURES:
1

Multiple hereditary exostosis, chondrosarcoma

86%

(1743/2021)

2

Multiple enchondromatosis, hemangioma

1%

(17/2021)

3

Multiple hereditary exostosis, enchondroma

5%

(98/2021)

4

Multiple enchondromatosis, chondroblastoma

2%

(34/2021)

5

Multiple hereditary exostosis, osteosarcoma

6%

(126/2021)

ML 1

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PREFERRED RESPONSE 1

(OBQ10.254) Which of the following radiographs represent typical findings seen with a mutation of the EXT1, EXT2, or EXT3 genes? Review Topic

QID: 3351
FIGURES:
1

Figure A

2%

(37/2345)

2

Figure B

1%

(24/2345)

3

Figure C

4%

(89/2345)

4

Figure D

91%

(2145/2345)

5

Figure E

2%

(39/2345)

ML 1

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(OBQ10.80) A 15-year-old male presents with 7 months of pain at the region of the hallux lesion shown in Figure A and B. His primary care physician initially diagnosed the lesion as a wart and it was unsuccesfully treated with a topical salicylic acid preparation. A radiograph is shown in Figure C. What is the next step in management? Review Topic

QID: 3168
FIGURES:
1

Neoadjuvant chemotherapy followed by surgical excision with subsequent adjuvant chemotherapy

1%

(20/1890)

2

600-800 cgy irradiation

0%

(6/1890)

3

Observation with serial radiographs every 6 months

1%

(20/1890)

4

Nail removal and surgical excision of the lesion

97%

(1830/1890)

5

Hallux amputation

1%

(10/1890)

ML 1

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(OBQ12.69) Mutations in the tumor suppressor genes EXT1 and EXT2 gene leads to a condition characterized by which of the following images. Review Topic

QID: 4429
FIGURES:
1

Figure A

2%

(89/3638)

2

Figure B

85%

(3086/3638)

3

Figure C

6%

(212/3638)

4

Figure D

4%

(158/3638)

5

Figure E

1%

(41/3638)

ML 1

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(OBQ10.29) A defect of which of the following genes is associated with an increased risk of chondrosarcoma and is inherited in an autosomal dominant manner? Review Topic

QID: 3117
1

PHEX

3%

(94/2912)

2

PMP-22

6%

(161/2912)

3

SYT-SSX

7%

(214/2912)

4

GNAS-1

6%

(163/2912)

5

EXT-1

78%

(2269/2912)

ML 2

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(OBQ12.20) Which of the following radiographs (Figures A-E) is consistent with a disorder that is inherited in an autosomal-dominant inheritance pattern? Review Topic

QID: 4380
FIGURES:
1

Figure A

3%

(117/3790)

2

Figure B

9%

(324/3790)

3

Figure C

72%

(2741/3790)

4

Figure D

8%

(301/3790)

5

Figure E

7%

(257/3790)

ML 2

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(OBQ07.18) A 50-year-old man with known Multiple Hereditary Exostoses complains of new onset right hip pain and an enlarging mass. Radiographs are shown in Figure A. Which of the following pathology specimens (Figure B-F) most likely represents the pathologic lesion in this patient? Review Topic

QID: 679
FIGURES:
1

B

9%

(62/677)

2

C

5%

(35/677)

3

D

33%

(226/677)

4

E

42%

(283/677)

5

F

10%

(70/677)

ML 4

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(OBQ09.95) A 22-year-old female with hereditary osteochondromas has difficulty supinating and pronating her forearm. Radiographs are shown in Figure A. Which of the following procedures would most effectively improve forearm rotation in this patient? Review Topic

QID: 2908
FIGURES:
1

Combined radius and ulna corrective osteotomy

18%

(286/1585)

2

Radial shaft osteotomy

5%

(87/1585)

3

Radial head resection

2%

(31/1585)

4

Ulnar osteotomy and lengthening

15%

(235/1585)

5

Osteochondroma excision

59%

(937/1585)

ML 3

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(OBQ06.105) All of the following are true of multiple hereditary exostoses (MHE) EXCEPT? Review Topic

QID: 291
1

Autosomal dominant inheritance

7%

(33/471)

2

Caused by mutation(s) in the EXT1/EXT2/EXT3 genes

1%

(6/471)

3

Exostoses grow towards the joint in MHE but away from the joint in solitary osteochondromas

75%

(353/471)

4

The most common joint affected is the knee

5%

(25/471)

5

The rate of transformation to chondrosarcoma is less than 10% in MHE

11%

(54/471)

ML 2

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(OBQ08.225) Which of the following is NOT associated with the condition shown in figure A? Review Topic

QID: 611
FIGURES:
1

subluxation of the radiocapitellar joint

7%

(25/339)

2

limb-length discrepancy

12%

(40/339)

3

valgus defomity of the knee

5%

(17/339)

4

ulnar deviation of the wrist

8%

(26/339)

5

absence of the thumb

67%

(228/339)

ML 2

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PREFERRED RESPONSE 5
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