Multiple Hereditary Exostosis


Genu Valgum OCMultiiple OCBowed forearms OC




Hereditary Multiple Exostosis (HME)


Heritable skeletal dysplasia characterised by multiple osteochondromas








AD with variable penetrance (96%)


90% of HME associated with mutation in EXT1 or EXT2 gene

- part of proteoglycan synthesis

- requires a second genetic hit to create the disease


Malignant Transformation




Fei J Bone Oncol 2018

- systematic review

- incidence of chondosarcoma 4%

- 75% between age 20 - 40

- 56% pelvis and proximal femur


Danger areas / central

- pelvis / proximal femur

- scapula / proximal humerus




Van der Woude et al Skeletal Radiol 2023

- total body MRI in 355 patients with HME

- 9/366 (2.5%) MRIs found suspicious lesions that ultimately were chondrosarcomas

- all in flat bones (pelvis / ribs / scapula)




Commonly presents as skeletal deformity, such as Madelung deformity


Lower limbs

- mildly short stature

- eg length discrepancies

- valgus knees / valgus ankle

- common peroneal compression


Upper limb

- scapular winging

- forearm bowing / ulnar deviation of wrist / loss of pronation / supination


Spinal stenosis


Multiple OsteochondromasMultiple Osteochondromas





- coxa valga

- neck short & broad


Mult OC hipHip Osteochondroma


Knee - genu valgum


Genu Valgum OCMultiiple OCMultiple OC



- valgus

- fibular shortening with valgus distal tibia

- wedge-shaped distal tibial epiphysis

- leads to valgus talar tilt in abnormal mortise


Ankle mult OC 1Ankle mult OC 2



- ulnar shortening / radial bowing / ulnar deviation of wrist

- can get radial head dislocation / carpal slip


Osteochondroma ElbowOsteochondromas Forearm 1Osteochondromas Forearm 2


Osteochondromas WristOsteochondromas Wrist LateralMulti OC wrist




Exostoses tend to be more disorganised with bosselated cartilage cap




Surgical Indications


Symptomatic osteochondromas - nerve impingement

Biopsy suspicious lesions

Growth deformity - bowing / leg length discrepancy




Knee valgus OCOsteochondroma Knee Lateral




Clement et al Knee 2014

- 172 patients with HME

- 90% had exostosis around the knee

- 20% had valgus deformity

- 15% had FFD deformity




1.  Multiple case reports of pseudoaneuryms and vascular complications with knee osteochondromas


2.  Excision of osteochondromas may cause rapidly developing deformity


Denduluri et al J Paediatri Orthop B 2016

- excision of medial proximal tibial osteochondroma in 3 patients with HME

- developed genu valgum as a result




Guided growth / temporary hemi-epiphysiodesis



Guided growth


Guided growth valgus HMEGuided growth 2 HME


Kang et al J Paediatr Orthop 2017

- 15 cases of MHE with genu valgum

- treated with hemi-epiphyseal stapling

- 67% satisfactory corrections

- correction slower than idiopathic valgus correction (1.5 years v 1 year)




Osteochondromas Valgus KneeOsteochondromas Knee Osteotomy 2Osteochondromas Knee Osteotomy AP






Zhang et al J Child Orthop 2021

- 61 children, mean age of 10

- 50% had ankle valgus

- correlates with osteochondromas lateral tibia / medial fibula


Surgical options


Guided growth



Temporary screw epiphysiodesis


Rupprecht et al J Paediatr Orthop 2015

- 12 patients with HME and ankle valgus

- average age of 12, average tibio-talar tilt 13 degrees

- treated with temporary medial malleolar screw epiphysiodesis for 24 months

- excellent corrections

- 43% rebounded > 5 degrees after screw removal, treated by repeated eiphysiodesis


Ilizaroz / Osteotomy


Olfram et al J Orthop Traumatol 2008

- correction of ankle valgus in 5 patients ilizarov

- average correction 18 degrees








Coxa valga

Hip subluxation


Guided growth


Hung et al J Paediatr Orthop 2023

- 12 patients with HME and coxa valga / hip subluxation

- guided growth improved neck shaft angles and epiphyseal angles




Osteochondromas Forearm 1Osteochondromas Forearm 2




Jo et al J Hand Surg Am

- 53 pediatric patients with HME

- 10% incidence of radial head dislocation




Prevent radial head dislocation / radial slip

? improve function




Excision of local osteochondromas

Ulnar lengthening


Ulnar lengthening


Vogt et al J Paediatr Orthop 2011

- 12 children mean age of 10 with HME

- external fixator ulna lengthening

- no change on radial head dislocation / carpal slip

- no functional improvement except radial abduction


Li et al J Orthop Surg Res 2020

- 17 forearms mean age 10

- Ilizarov distraction osteogenesis of the ulna average 4 cm

- improved pronation and elbow flexion

- unable to reduce radial head dislocation




Roach et al JBJS Am 2009

- 43 patients with HME evaluated with spine MRI

- 68% had spinal osteochondromas

- 27% had lesions encroaching on spinal canal

- all asymptomatic