Solitary osteochondroma

 

Osteochondroma ankleOsteochondroma kneeOsteochondroma UlnaOsteochondroma

 

Definition

 

Cartilage capped bony projection on the external surface of bone

 

Epidemiology

 

Most common benign bone tumour / 9% of all bone tumours

 

85% solitary

15% multiple / multiple hereditary exostosis

 

Etiology

 

? secondary to injury of growth plate

- defect in Perichondral Ring of La Croix

- results from herniation & separation of fragments of physis through the periosteal bone cuff 

 

More recent research suggests genetic mutation

 

Location

 

Any bone formed by endochondral ossification

Arises from cortex of long bone adjacent to physis

 

Most common location

- around knee (distal femur / proximal tibia / proximal fibula)

- proximal humerus

- hands and feet

 

More rarely scapula and spine

 

Natural History

 

Grows by endochondral ossification of enlarging cartilage cap

- no growth after skeletal maturity

 

Malignant Transformation

 

Low-grade chondrosarcoma

- isolated lesion < 1% 

- more common with central lesions

 

Suspicious features

- growth after maturity

- increased thickness of cartilage cap on CT / MRI - > 2 cm

- increasing pain

- increased calcification / bony erosion / lytic areas on xray

- septal enhancement after MRI with gadolinium

 

Bernard et al Radiology 2010

- MRI / CT of 64 benign osteochondromas and 34 secondary chondrosarcomas

- cartilage cap 2 cm or more 100% sensitive and 98% specific for secondary chondrosarcoma

 

OC malignantCT malignant OC

Malignant transformation of osteochondroma

 

Clinical

 

Often incidental finding

 

Bony lump - commonly noticed during adolescent growth spurt

 

Symptoms

- pain & tenderness - bursitis / tendon / neurovasular impingement

- decreased ROM

 

X-ray

 

Cortical and marrow continuity

 

Types

1. Pedunculated - has a stalk, points away from joint

2. Sessile - attaches to bone with a broad base

 

Pedunculated

 

Femoral OsteochondromaOC femur 1

 

Protuberant bony lesion arising adjacent to physis

- directed away from joint

- cortical bone and marrow space continuous

 

Sessile

 

Osteochondroma shoulder

 

CT

 

Cortex and medullary cavity of normal bone contiguous with osteochondroma

 

OC CT HumerusOsteochondroma CT

 

MRI

 

Cartilage cap iso-intense with hyaline cartilage

 

OC humerus 1Osteochondroma MRI

 

Osteochondroma shoulderOC humerus MRI 1OC Humerus MRI 2

 

Pathology

 

Gross

- surface covered with irregular cartilage

- osteochondroma has cortical and medullary bone

 

Osteochondroma Cartilage CapOsteochondroma Excised

 

Histology

- cap resembles disorganised physis

- irregular shaped underlying trabecular bone

- may contain calcified cartilage matrix

 

Management

 

Surgical Indications

 

1. Painful / symptomatic - bursitis / tendon impingement / neurovascular impingement

3. Restore joint motion

4. Correct deformity

5. Biopsy suspicious lesions

6. Central / pelvis / scapula - higher malignant transformation rate

 

Technique

 

Remove osteochondroma at the bony base

 

Results

 

About the knee

 

Osteochondroma irritating Pes anserinus

 

Typically causes bony mass or tendon impingement

- i.e. hamstring impingement at proximal medial tibia

 

Wu et al JBJS Am 2021

- excision of solitary osteochondroma around knee in 264 patients < 20 years of age

- 65% pedunculated / 35% sessile

- distal femur > proximal tibia > proximal fibula

- recurrence in 3/264 (1%)
 

Proximal humerus

 

Osteochondroma shoulder

 

Bae et al J Pediatr Orthop 2014

- 31 patients with proximal humerus osteochondromas

- anterior / lateral / posterolateral debulked 92%

- posteromedial debulked 68%

- recurrence 2/31 (6.5%)

 

Ankle

 

Osteochondroma ankleAnkel OC excision

 

Causes valgus deformity

 

Chin et al JBJS Am 2000

- 19 patients with solitary osteochondroma of distal tibia or fibula

- cause plastic deformity and pronation deformity

- distal tibia more symptomatic than distal fibula

- 4/19 recurred

 

Appy-Fedida et al J Foot Ankle Surg 2017

- trans-fibular approach for worsening valgus deformity in 10 cases

- good functional outcomes

- recurrence in 1 case

- 7/10 developed tibiofibular synostosis

 

Scapula

 

Typically on ventral surface

Causes winging / snapping with abduction

 

Prakash et al J Orthop Surg 2020

- medial parascapular approach to ventral osteochondroma

 

Talus

 

OC talus