Fibrous Dysplasia

 

Fibrous Dysplasia PelvisFibrous dysplasia hip

 

Definition

 

Arrest in development of normal bone with weak fibro-osseous bone

 

Pathophysiology

 

Caused by somatic activating mutations in GNAS

 

Types

 

Spectrum of disease

- Monostotic (75%) - single bone affected

- Polyostotic (25%) - multiple bones affected

- McCune-Albright Syndrome

 

McCune - Albright Syndrome

 

Triad

1.  Fibrous Dysplasia

2.  Cafe-au-Lait Spots

- irregular "Coast of Maine"

3.  Hyperfunctioning endocrinopathies

- precocious puberty

- hyperthyroidism

- growth hormone excess

 

Malignant transformation

 

Osteosarcoma / fibrosarcoma / MFH / Chondrosarcoma

 

Increased risk in polyostotic disease / McCune-Albright Syndrome

 

Qu et al Medicine 2015

- 15 / 542 (3%) cases of FD had malignant transformation

 

Inheritance

 

Usually non genetic inheritance

 

Natural history

 

Usually diagnosed in children and adolescents

Remains relatively unchanged throughout life

 

Clinical

 

Bone pain

 

Long bones

- pathological fracture

- deformity / bowing

- limp

- leg length discrepancy

 

Craniofacial involvment

- slow growing painless masses

- cosmetic deformity / dental problems / vision and hearing loss

 

FD skull

 

X-ray

 

Fibrous dysplasia hipFibrous dyplasiaFD ankle

 

Intramedullary lucent diaphyseal lesion with 'ground glass appearance'

- thinned, slightly bulged cortex

- ± endosteal scalloping

- may have angular deformity / bowing

 

Coxa vara and Shepherd's Crook deformity of proximal femur

- Shepherd's Crook - anterior bowing of femur

- secondary leg length discrepancy

- pain, difficulty walking

 

FD hipFD hip 2

 

Sabre tibia

 

FD tibia 1FD tibia 2

 

Pathological fracture

 

FD humerus #

 

Spine involvement / scoliosis

 

Leet et al JBJS Am 2004

- 62 patients with polyostotic FD

- 40% had scoliosis

 

Berglund et al J Bone Mineral Res 2018

- 138 patients with fibrous dysplasia / McCune Albright syndrome

- 61% scoliosis

- 35% moderate to severe

- no effect of bisphosphonates in reducing curve progression

 

CT

 

Fibrous Dysplasia CTFD CT hip

 

Bone Scan

 

Skeletal survey - determine disease burden / polostotic

 

MRI

 

Low signal intensity T1 / High signal intensity T2

 

Fibrous dysplasia hipFD MRI 1FD hip MRI 2

 

Fibrous dysplasia hipFD hip MRIFD hip MRI 2

 

Histology

 

Fibrous tissue with irregular, randomly oriented bony trabeculae

 

Management

 

Multidisciplinary team

 

Orthopedics / Endocrinology / Dentistry

 

Bisphosphonates

 

Bertin et al Rev Endocr Metab Disord 2023

- systematic review and meta-analysis of bisphosphonates

- increased bone density and reduces bone pain

 

Surgical intervention

 

Indications

- deformity correction

- fracture prevention (>75% of cortical diameter)

- prevention deformity

- pathological fracture

 

Bone grafting

 

Bone grafting is of limited value with fibrous dysplasia

 

Guille et al JBJS Am 1998

- curettage and bone grafting of lesions

- 100% resorption of bone graft with recurrence of lesion

- osteotomy and fixation with reconstruction nail mainstay of treatment

 

Majoor et al CORR 2017

- cortical strut allograft for 30 patients with impending or fractures proximal femur

- 50% radiological resorption of graft

 

Corrective osteotomy / Intra-medullary nailing

 

Mainstay of treatment

 

Ippolito et al J Orthop Traumatol 2023

- 24 patients with 34 femurs and 14 tibias requiring intra-medullary nailing

- mean age 32

- osteotomy and deformity correction often required

- nonunion / delayed union / implant failure in 5 cases

 

FD 2FD 1

 

FD Humerus 1FD Humerus 2

 

FD Femur 1FD femur 3FD femur 2

 

FD Humerus 1FD Humerus 2

 

Proximal femur coxa vara and shepherds crook deformity

 

Ippolito et al JBJS Am 2015

- 11 cases

- initial osteotomy correction of coxa vara and fixation with hip plate

- later osteotomy and correction of shepherds crook / femoral bowing and insertion reconstruction nail

- improved pain and gait

- significant blood loss at both stages

 

Ippolito Surgical Technique

 

Kim et al Bone Joint J 2015

- 209 patients with FD of the proximal femur

- 12% developed osteoarthritis

 

Garceau et al Can J Surg 2020

- 10 hips in 9 patients with 6 year follow up

- osteotomy to correct coxa vara

- proximal femoral allograft used +/- strut allograft

- one revision due to poor bone stock and femoral implant subsidence

 

Fibrous Dysplasia Hip CT