Bone Dysplasias

Definitions

Dysplasia is taken to mean a generalised disorder of bone or cartilage.
Most dysplasias are familial but the individual patient may be the first in the family to be affected.
Some dysplasias are not generalised affecting only one side or one limb, eg dyschondroplasia, dysplasia epiphysialis hemimelica and melorrheostosis.
Joint laxity is associated with connective tissue dysplasias such as Ehlers-Danlos syndrome, Marfans syndrome, Morquios disease and osteogenesis imperfecta.
Generally radiological examination of three body regions will give a good indication of the extent of skeletal involvement and the likely diagnosis. AP hand, AP pelvis and hips and a lateral view of the lumbar spine.

Dysplasia:

Used to describe a generalised developmental disorder of bone or cartilage.

Dysostosis:

Used to describe changes affecting a single bone or segment of the skeleton.

Malformation:

Denotes a primary abnormality of development.

Deformity:

Refers to a change in structure of a previously normal bone.

Short Stature:

Height that is at the lower end of the normal range for a persons normal peers.

Dwarf:

Refers to a pathological diminution in stature and may be either

Proportionate (midget) eg, Hurler's disease, hypophosphatasia, hypophosphataemia and severe varieties of osteogenesis imperfecta
Disproportionate (short limb or short trunk) eg, achondroplasia, hypochondroplasia, diastrophic dwarfism and chondroectodermal dysplasia
Short limb dwarf may be further subdivided depending on the site of maximal shortening
1. Mesomelic (central portion)
2. Acromelic (distal portion)

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Classification

Several different classifications of bone dysplasias have been published. Rubin grouped the skeletal dysplasias according to the anatomic distribution of bone changes. This is the currently favoured method of classification
Rubin P. Dynamic classification of bone dysplasias

Epiphyseal Dysplasias
1. Epiphyseal hypoplasias
  1. Failure of articular cartilage; spondylo-epiphyseal dysplasia
  2. Failure of ossification of centre; multiple epiphseal dysplasia
2. Epiphyseal hyperplasia
  1. Excess of articular cartilage; dysplasia epiphsealis hemimelica
Physeal Dysplasias
1. Cartilage hypoplasias
  1. Failure of proliferating cartilage; achondroplasia
  2. Failure of hypertrophic cartilage; metaphyseal dysostosis
2. Cartilage hyperplasias
  1. excess of proliferation cartilage; hyperchondroplasia
  2. excess of hypertrophic cartilage; enchondromatosis
Metaphyseal Dysplasias
1. Metaphyseal hypoplasias
  1. Failure to form primary spongiosa; hypophosphatasia
  2. Failure to absorb primary spongiosa; osteopetrosis
  3. Failure to absorb secondary spongiosa; craniometaphyseal dysplasia
2. Metaphyseal hyperplasias
  1. Excessive spongiosa; hereditary multiple exostosis
Diaphyseal Dysplasias
1. Diaphyseal hypoplasias
  1. Failure of periosteal bone formation; osteogenesis imperfecta
  2. Failure of endosteal bone formation; idiopathic osteoporosis
2. Diaphyseal hyperplasias
  1. Excessive periosteal bone formation; progressive diaphyseal dysplasia
  2. Excessive endosteal bone formation; hyperphosphataemia

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History & Examination

Common presenting complaints are shortness of stature, deformities of the skull, flat or long bones, pain or pathological fractures.
Pain however is not usually a feature of bone dysplasia, but may be a feature of metabolic bone disease.

Assessment of stature:: Measure height® growth charts
Measure upper and lower segments® ratio US/LS (usually 1.7:1 at birth® unity in late childhood)
Arm span usually approximates height

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Connective Tissue Disorders

Over 150 conditions exist in the family of heritable disorders of connective tissue with a prevalence ranging from 1/10,000 to 1/150,000
Classification

Disorder of fibrous elements such as osteogenesis imperfecta, Ehlers-Danlos, and Marfans
Disorders of proteoglycan metabolism such as the mucopolysaccharideoses
Osteochondrodysplasias such as achondroplasia, spondyloepiphyseal dysplasia and metaphyseal dysplasias
Inborn errors of metabolism that secondarily affect connective tissue such as homocystinuria and alkaptonuria

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Epiphyseal Dysplasias

Multiple epiphyseal dysplasia

Characterised by late appearance of epiphysis, knobbly joints, stubby digits and minimal shortness of stature.

Inheritance

Autosomal Dominant
Prevalence 10-15 / million
Age at diagnosis 1-2 years (later in milder cases)

Clinical Features

First suspected due to delayed walking
Normal intelligence

X-Rays

Delayed development and irregular epiphyses
Epiphyses are flattened (in the hips looks like Perthes)

Pathology

Disordered development of epiphseal ossification centres
Articular cartilage becomes irregular® early OA
Number of epiphyses involved varies
Femur & Humerus common sites
Skull facial bones & pelvis are normal

Differential

Bilateral Perthes (other epiphyses affected)

Treatment

Symptomatic
CPM may help joint congruity
Total joint replacements once OA bad

Prognosis

normal life expectancy

Dysplasia epiphysealis hemimelica

Inheritance

unknown

Incidence

Extremely rare less than 1 / million
Age at diagnosis -early Childhood
Male : Female 3:1

Clinical Features

Becomes evident in early childhood® bony lump or stiffness
Usually unilateral involvement with one limb and only half of the epiphysis
Common sites the tarsus, distal femur & proximal tibia
Irregular bony masses protrude form the epiphysis
70% present with deformity

X-Rays

Irregular often multi centric bony protrusion develops from the affected epiphysis
Similar to an exostosis but originates from the epiphysis not the metaphysis

Pathology

Similar to an osteo-cartilaginous exostosis
Either a cartilage capped pedunculated mass or irregular expansion of the articular surface

Treatment

Excision if interferes with function

Prognosis

Usually stops growing at skeletal maturation
Malignant change has not been reported
Normal life expectancy

Spondylo epiphseal dysplasia

Classification

Congenita (severe form)
Tarda (mild form)

Inheritance

Congenita:: Autosomal dominant (most are sporadic)
Tarda:: X linked recessive
Prevalence: Congenita 1-2 / million
Tarda 3-4 / million
Age at diagnosis: Congenita 3-4 years
Tarda 5-10 years
Male : Female: Tarda males only

Clinical Features:(Congenita)

Associated with severe coxa vara and disproportionate short stature, abnormal epiphyses and vertebra plana
Femoral head ossification not until 5 years
Vertebrae are flattened throughout and pear shaped
Associated CDH
Odontoid malformation® atlanto-axial instability
Scoliosis and kyphosis develops in late childhood early adolescence
Other abnormalities associate (TEV, hernia, myopia cleft palate)
(Tarda)
Flattened vertebrae and inter vertebral discs
Posterior spinal hump
Back pain at age 5-10 years
Proximal femur & humerus minimally involved

X-Rays

Posterior wedging of vertebrae
Platyspondyly
Un ossified femoral heads until adolescence
Hypoplasia of odontoid

Pathology

Disorder of Type II collagen

Treatment:(Congenita)

Atlanto-axial instability most serious problem
Coxa vara may require osteotomy
(Tarda)
Conservative, most deformities usually not severe

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Mucopolysaccharide disorders

1. Morquios Disease (Mucopolysaccharidosis IV)

Incidence

Commonest of Mucopolysaccharidosis

Inheritance

Autosomal Recessive
Age at diagnosis 12-18 months

Clinical Features

Features become increasingly obvious with age
Dorso-lumbar kyphosis usually first feature, occasionally thoraco-lumbar kyphosis
Spine is normal at birth and until 2 years® universal platyspondyly
Knock knees and pes valgus also a feature
Short trunk dwarfing with normal intelligence
Hypoplasia and occasional absence of the odontoid process
Generalised joint laxity® joint instability and genu recurvatum
Epiphseal deformation, elongation
Central constriction of metacarpals & phalanges® short stubby fingers
Wide spaced eyes and corneal clouding develops in childhood
Tire easily with poor physical endurance
Manubrio-sternal angle of 90o

X-Rays

Vertebral bodies are ovoid early® platyspondyly later
Hypoplasia or absence of odontoid® instability
Epiphyses are broad and flattened and long bones short and curved
Acetabular dysplasia & coxa vara or valga
Metatarsals and metacarpals shorter & thicker than normal
Thorax becomes barrel shaped

Pathology

Deficiency of N-Ac-Gal-6-sulphate sulphatase

Laboratory tests

Excessive excretion of keratin sulphate in urine

Treatment

No specific treatment
Occipito cervical fusion may be required
Other deformities corrected if difficulty walking

Prognosis

May live many years
Early degenerative joint disease develops
Death may occur before the age of 20 due to chest infections or cardiac complications

2. Hurlers Disease (Mucopolysaccharidosis I)

Inheritance

Autosomal recessive

Incidence

Relatively common
Age at diagnosis 3-6 months

Clinical Features

Appears normal at birth
Develops abnormal facies and enlarged head (Gargoylism)
Mental retardation is striking
Chronic rhinitis and noisy mouth breathing
Large tongue, thick lips and open mouth
Flexion contracture of joints not uncommon
Clouding of the cornea

X-Rays

Similar features to Morquios
Marked localised kyphosis between age of 1 & 2
Gibbus at level of hypoplastic vertebrae (usually L2 or L1)
Coxa valga is marked
Acetabular roof is shallow and flared iliac wings
CDH or CSH common
Ribs narrow posteriorly and broad anteriorly
Long bones also broad one end and narrow at the other

Pathology

Deficiency of ?-L iduronidase
Cells have abnormal mucopolysaccharide deposits

Laboratory tests

Increased urinary excretion of dermatin & heparin sulphate

Treatment

No specific treatment
Atlanto axial instability may require stabilisation
Treat CDH or CSH in conventional manner

Prognosis

Most die in childhood before the age of 10 years

3. Hunters Syndrome (Mucopolysaccharidosis II)

Inheritance

X linked recessive

Incidence

Said to be 1/5 of Hurlers ?
Age at diagnosis again 3-6 Months
All Male

Clinical Features

Similar to Hurlers
No clouding of the cornea
Mental retardation occurs later and is less severe
Deafness occurs in 50%
X-Rays Similar to Hurlers Syndrome

Pathology

Deficiency in enzyme sulfo-iduronate sulphatase

Laboratory tests

Increased excretion of heparin and dermatin sulphate

Treatment

No specific treatment

Prognosis

Most survive into the 3rd decade
Some may have a normal life span
Patients usually succumb to cardiac disease & pulmonary hypertension

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Physeal Dysplasias

Achondroplasia

Most common type of dwarfism. Characterised by short limbs and bulging cranium due to disordered enchondral bone formation.

Inheritance

Autosomal dominant.
Most affected individuals do not reproduce® 90% cases are sporadic
Risk of second dwarf from normal parents almost zero
Amongst dwarfs risk® 75 - 100% if both and 50 - 100% if one parent affected (depending if parent Aa or AA)
Increased age of father® increased risk of dwarf

Incidence:

0.5 - 1.5 / 10,000
Age at diagnosis -Features obvious at birth

Male : Female

1:1

Clinical Features

Rhizomelic short limbs (greatest in proximal segments)
Sitting height usually around 10th percentile
Brachycephalic skull
Face broad and prominent forehead with depressed nasal bridge
Exaggerated lumbar lordosis
May be increased thoracic kyphosis (33% of patients)
Hands are short and broad and all digits same length with trident deformity of fingers
Lower limbs often bowed
Hands do not reach the buttocks but may be able to kiss feet with knees extended
Intelligence usually normal or above average
Obesity is a problem
Dental crowding and ear problems secondary to bone overgrowth

X-Rays

All long tubular bones are affected
Metaphysis is widened but the epiphysis is normal
Fibula may be longer than the tibia
Growth plates are centrally notched or "V" shaped
Iliac wing is squared off
Pelvic inlet typically "Champagne Glass" shape
Short femoral neck
Decreasing inter pedicular distance from L1 to L5
Pedicles also short® canal stenosis in 40 - 50%
Foramen Magnum small and funnel shaped
Can be diagnosed in utero by U/S

Pathology

Block of interstitial cartilage production® failure of the proliferating cartilage of the physis and cartilage cells produced by the epiphyses fail to line up properly and undergo degeneration
Relative lack of cartilage formation and normal palisade arrangement of cartilage cells of the physis
Normal periphery of physis with flaring of the metaphysis and normal membranous ossification
Periosteal bone formation is unaffected

Differential

Hypochondroplasia (skull normal)
Diastrophic dwarfism (club foot, scoliosis, cauliflower ear and hitch-hikers' thumb)
Chondroectodermal dysplasia (distal limb segments more than proximal, cardiac disorders & polydactyly)
Spondyloepiphyseal dysplasia, associated with grossly distorted large proximal joints, a normal skull and irregular platyspondyly

Treatment

No specific treatment. May require spinal decompression or corrective osteotomy of lower limb deformity. ? place of limb lengthening

Prognosis

Near normal life expectancy

Hypochondroplasia

Inheritance

Autosomal dominant

Incidence

Similar to achondroplasia
Age at diagnosis 5-6 years
Male : Female 1:1

Clinical Features

Short stature becomes evident at 5-6 years
Flexion deformity of knees & elbows develops
Ligamentous laxity and genu varum

X-Rays

Similar to achondroplasia but less severe

Pathology

A mild form of achondroplasia

Treatment

No specific treatment

Enchondromatosis (Olliers' disease)

Characterised by circumscribed masses of cartilage arranged in linear fashion in the interior of bones.
Olliers' disease refers to a condition where the enchondromata are distributed unilaterally.

Inheritance

This is a non hereditary developmental defect

Incidence

Rare ? real incidence
Usually evident early in childhood

Clinical Features

Great variation in distribution and extent of condition
LLD a common feature
Genu valgum may also be present
Hands involved may® grotesque swelling of digits
Bowing of long bones also a feature
Haemangiomas a common extra-skeletal manifestation
Marffucci's disease when in association with multiple haemangiomata
Increased pain or growth in adult life® ? malignant change

X-Rays

Usually more extensive than clinical impression
Elongated, longitudinal radiolucent streaks
Involves the metaphysis & epiphysis of long bones
Epiphysis usually not involved until after skeletal maturity
Pathological # may occur
Spotty calcification may be present in the tumours

Pathology

Hamartomatous proliferation of cartilage cells originating from within the bone as well as the cambian layer of periosteum
Masses of cartilage arranged as small ovoid or round collections separated by bony septa
Histology similar to that of an isolated enchondroma with hyper cellular tissue
Sarcomatous change may occur (1 -5%)

Treatment

Correction of LLD & other deformities

Prognosis

Normal life expectancy if no sarcomatous change

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Metaphyseal Dysplasias (hypoplasias)

Hypophosphatasia

Genetically determined inborn error of metabolism.

Inheritance

Autosomal recessive
Rare adult form is autosomal dominant

Incidence

? Rare
Age at diagnosis is variable

Classification

Congenital form® baby still-born or dies soon after birth
Tarda form® becomes evident around 6 months old
Mild adult form® results in osteomalacia

Clinical Features

(Congenita)
Usually dies of respiratory failure in neonatal period or stillborn
(Tarda)
Failure to thrive
Bossing of the skull
Bowing of the ribs
Flaring of the ends of long bones
Fractures and angular deformities
Short stature
Lose deciduous teeth early due to caries from poor enamel
(Mild adult form)
Presents with osteomalacia or # with delayed healing

X-Rays

Demineralisation of the entire skeleton (severity dependant on type)
Widening of the physis with irregularities extending into the metaphysis
Fractures and deformities of long bones
Renal calcinosis may be evident

Pathology

Deficiency of alkaline phosphatase
Disturbance of mineralisation and defective ossification of cartilage
Histology resembles Rickets with abundant un-mineralised osteoid

Laboratory tests

Hypercalcaemia (may® renal calculi)
Serum Phosphorus is normal
Increased excretion of phosphorylethanolamine and inorganic pyrophosphate
Decreased excretion of hydroxy proline

Differential

Various types of Rickets
Severe congenital form differentiate from osteogenesis imperfecta

Treatment

Correction of deformity
Enzyme replacement of no long term benefit
Do not give Vit D as® increased hypercalcaemia

Prognosis

If survives childhood condition usually improves with increasing maturation of the skeleton

Osteopetrosis

Characterised by failure of bone resorption due to a deficiency of osteoclasts.

Inheritance

Congenita (autosomal dominant)
Tarda (autosomal recessive)

Incidence

? Congenita is rare
Tarda is common
Age at diagnosis in congenita evident in the first months of life and in the Tarda form may remain asymptomatic

Clinical Features

(Congenita)
Obliteration of the marrow® pancytopenia, bleeding, anaemia
Failure to thrive
Hepatosplenomegally
Cranial nerve & optic nerve palsies
Pathological # and osteomyelitis is common (esp in mandible)
(Tarda)
Often remains clinically silent often an incidental finding

X-Rays

Increased density of bone
Os-in-os (bone within a bone) is a feature seen in childhood but fades in adolescence
Adolescent and adult vertebrae® sandwiched appearance with bands of increased density adjacent to the end-plates

Pathology

Failure of bone resorption
Increased numbers of osteoclasts but defective function
Decreased response of osteoclasts to PTH
Decreased collagenase activity
Failure of remodelling® splaying of metaphysis
Healing of ostepetrotic bone may be quiet slow

Laboratory tests

CBP to monitor pancytopenia

Treatment

Relief of foramenal compression
Control of anaemia & infections

Prognosis

Death usually occurs in the second or third decade due to infection or haemorrhage in the congenita type
Tarda form compatible with normal life expectancy

Hereditary multiple exostosis

Condition characterised by multiple cartilaginous and bony exostoses protruding from bones preformed in cartilage.

Inheritance

Autosomal dominant

Incidence

About 9 / million
Rrarely evident before 2 years
Male : Female 7:3

Clinical Features

Usually manifested in childhood, (not evident at birth)
Affects long bones of limbs most commonly
Usually around the knee, proximal femur & humerus, distal radius & ulna
Relatively short limbs
Tibia valga is a frequent finding
Coxa valga is present in about 25% and is associated with acetabular dysplasia

X-Rays

Multiple exostosis
Bone area involved is often much larger than in solitary lesions
Vary in size and number
Almost always point away from the physis

Pathology

Similar to a single osetochondroma
Cartilage cap usually thicker
If cap more than 1cm thick or base more than 8cm suspect chondrosarcomatous change
Rate of malignant transformation about 2% overall (Jaffe)
Per lesion incidence not more than than solitary lesions (0.25%)

Treatment

Excision indicated when painful or if interferes with joint or muscle function, results in pressure on nerves or vessels or causes deformity
Chondrosarcomatous change treat as for isolated tumour (usually occur around the pelvis)

Prognosis

Have normal life expectancy unless® malignant change

Osteopathia striata

Characterised by striations in the metaphyseal regions of cancellous bone.

Inheritance

Autosomal dominant

Incidence

0.1 / million

Clinical Features

Clinically asymptomatic
No pathological significance
Association with sclerosis and thickening in base of skull

X-Rays

Usually bilateral, symmetrical involvement of one bone or entire skeleton
Striations are parallel to long axis of bone
May extend into the epiphysis
In pelvis® fan like "sunburst" arrangement

Treatment

No specific treatment

Prognosis

Normal life expectancy

Osteopoikilosis

Characterised by dense ovoid or circular spots in cancellous bone.

Inheritance

Autosomal dominant

Incidence

0.1 / million
Affects men and women equally
May be noticed at birth or develop during skeletal growth

Clinical Features

Asymptomatic
Occasionally associated with hereditary multiple exostosis
Usually seen in metaphyseal and epiphseal region
Most common in tarsal and carpal bones
Rarely seen in diaphysis
10 - 20% associated with dermatofibrosis lenticularis disseminata (small whitish yellow fibrous dermal & subcutaneous nodules)
Predisposition to keloid formation and scleroderma like lesions

X-Rays

3-5mm ovoid or circular lesions in the metaphysis / epiphysis
Do not affect either the cortex or contour of the bone

Treatment

No specific treatment required

Prognosis

Of no pathological significance
Some enlarge, some get smaller and some disappear

Melorrheostosis (from Greek; melos = member & rhein = flow)

Inheritance

Not established
Congenital disorder affecting bones & other tissues

Aetiology

Thought to be an abnormality in embryogenesis
Problem with limb bud formation in 4th - 7th postovulatory week

Incidence

1 / million
Usually evident in infancy

Clinical Features

Pain in affected bones is the main feature
Joint contracture® rigid deformity present in all patients
Onset of pain usually follows several years after development of joint contracture and contractures progress during childhood
Peri articular ectopic bone
Limb length inequality present in almost all cases
May be peripheral neuropathies due to pressure

X-Rays

Radiopacity in longitudinal streaks along the axes of long bones (wax flowing down a candle)
Children sclerosis is endosteal, and in flat bones
Adults sclerosis is periosteal® streaks on outside of diaphysis

Pathology

Long bones most commonly involved but may be any
May be monostotic, polyostotic or monomelic
Histopathological examination® osteosclerosis & fibrosis
Bone formation exceeds normal destruction
Bone marrow may be fibrous or fatty
Muscles are oedematous and fibrosis of skin & subcutaneous tissue is common
Soft tissue calcification, especially peri articular and vascular tumours are associated

Differential

Pyogenic osteomyelitis (monostotic)
Arthrogryposis in children (not painful)
Scleroderma

Treatment

Management of limb deformities difficult
Hazards of surgery need to be stressed
Relief of pain and prevention of deformity by splinting and soft tissue release

Prognosis

Gloomy prognosis

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Metaphyseal Dysplasias (hyperdysplasias)

1. Metaphyseal Dysplasia (Pyles dysplasia)

Characterised by thickening of the medial end of the clavicles, pubis and ischium.

Inheritance

Autosomal recessive

Clinical Features

No clinical implication except incidence of genu valgum with thickening medial end of clavicles, pubis and ischium, some sclerosis of the skull vault may be evident
Marked Erlenmeyer flask flaring of long bone (esp. femurs, proximal tibias & fibula) and may develop a LLD or stress # due to increased bone fragility

Treatment

Nil specific but may require corrective osteotomy

Prognosis

Normal life expectancy

2. Cranio-metaphyseal dysplasia

Inheritance

Autosomal dominant (common mild form)
Autosomal recessive (uncommon severe form)

Incidence

Age at diagnosis (severe form) infancy

Clinical Features

(severe form)
Distortion or jaw and facies secondary to sclerotic thickening of the skull
Metaphyseal Erlenmeyer's flask deformity
Mal-occlusion of teeth
Cranial nerve palsies

3. Metaphyseal chondrodysplasia

Characterised by dwarfing, and improper mineralisation of the shafts of bones in the metaphyseal region.
May be associated with pancreatic endocrine deficiency, intestinal malabsorption, Hirschsprings disease, and chronic lymphopenia & neurtopenia.

Jansen Type

Inheritance: Autosomal dominant
Incidence: less than 0.1 / million
Age at diagnosis -severe short stature evident at birth
Clinical Features: Wide spaced exophthalmic eyes
Dwarfing
Short limbs (most marked in distal segments)
Angular deformity of metaphyseal / diaphseal junction
Delayed appearance of epiphysis
X-Rays Bulbous expansion of the metaphysis
Metaphysis is irregular, mottled and fragmented

Schmid Type

Inheritance: Autosomal dominant
Incidence: More common & less severe than Jansen type
Age at diagnosis 3-5 years
Clinical Features: Moderate shortness of stature
Skeletal changes develop after beginning weight bearing
Growth of long bones is inhibited
Coxa vara
Tendency to get SFCE
Genu varum & waddling gait
The epiphysis is normal
X-Rays Splaying, irregularity and cupping of the metaphysis
(similar to rickets)
Femoral neck shaft angle is decreased
Treatment: Nil specific
Corrective osteotomies for deformities

Spahr-Hartmann Type

Inheritance: Autosomal recessive
Clinical Features: Severe bow legs is the principle feature

McKusick Type

Inheritance: Autosomal dominant
Clinical Features: Sparse, short, brittle hair and excessive joint laxity
Ankle deformity secondary to unusual length of fibula (hind-foot in varus, mid-foot & forefoot in valgus)
Dwarfing may be marked and the epiphyses are normal
X-Rays Lateral spine vertebrae are oval persisting into childhood
Resembles the Schmid Type

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Diaphyseal Dysplasias

Osteogenesis imperfecta

A connective tissue disorder characterised by osteoporosis, fragile bones, dentinogenesis imperfecta, deafness, blue sclera, ligamentous hyper mobility, herniae and they bruise easily.

Classification

(Sillence 1981)
Congenita (recessive)
Tarda (dominant)

Type	Qualifying Suffixes	Inheritance	Clinically
I A&B (1/30,000)	Congenita (tarda)	Autosomal dominant	Dentinogenesis imperfecta may be a feature (Types A without & B with) Distinctly blue sclera throughout life Presenile hearing loss in 40% Fractures at birth in 10% Kypho-scoliosis in 20%
II (1/62,000)	Congenita	Autosomal recessive	Blue sclera Extreme bone fragility Often intrauterine or neonatal death
III (Rare)	Congenita (tarda)	Autosomal recessive	Sclera bluish at birth but normalises Sever bone fragility and deformity Smallest of all OI patients Often sever kyphosis / scoliosis Death usually in infancy
IV A&B (? Rare)	Congenita (tarda)	Autosomal dominant	Dentinogenesis imperfecta may be a feature (Types A without & B with) Normal sclera or becomes normal Difficult to differentiate from Type III

Clinically

Dependant on type and severity
Short stature, limb deformities and broad skull
May have blue sclera, scoliosis, ligament laxity and tendency to bruise easily
Coxa vara, bowing of the femur and tibia, knock knees, valgus feet and dislocation of the radial head are all fairly common

X-Rays

Typically multiple fractures of various age
Angular deformities and bent bones
If severe multiple rib #'s limit respiration
Defective sub periosteal bone formation® thin bone with normal width of physis
Popcorn calcifications evident in metaphysis resolve after skeletal maturity

Wormian bones

Detached portions of the primary ossification centres of the adjacent membrane bones. Should be more than 10 to be significant, and should measure 6mm x 4mm. Arranged in a mosaic pattern. (Claus Wormius, Danish anatomist)
Also seen in Cleido-cranial dysplasia, Pyknodysostosis, Hypophosphatasia and Hypothyroidism
Vertebrae initially bi-concave® wedge #'s
Scoliosis develops in about 40%
Osteoporosis & feathering of trabeculae in milder forms
Erlenmeyer flask appearance in some & trumpet in others
Coxa vara & acetabular dysplasia is common
Basilar invagination into base of skull may occur
Hyperplastic callus formation may occur® appearance of osteogenic sarcoma (M more than F, and the sclera is white)

Pathology

Defective Type I collagen maturation beyond reticulin fibre stage
Single gene disorders that affect the structure and biosynthesis of Type 1 collagen give rise to a varieties of Osteogenesis imperfecta and more than 70 mutations in the genes that encode the chains of Type 1 collagen have been identified and are associated with defective cross linking
Mild phenotypes may blend with common disorders such as osteoporosis
Histologically bone is characterised by larger areas of osseous tissue devoid of an organised trabecular or lamellar pattern with the bone being much more characteristic of woven or primitive bone
Osteoblasts have normal or increased activity but fail to produce or organise collagen
Affects both enchondral & membranous bone formation
Osteoclasts are normal and increased in number
The physis is usually broad & irregular
Secondary ossification centres® delayed maturation
Fractures heal at the normal rate but with abnormal bone
Blue sclera is caused by the thinness of the collagen layer
Changes occur in the skin, ligaments, tendons, sclera and inner ear and the condition is associated with numerous other congenital malformations, particularly cardiac and hip anomalies.
Dentinogenesis imperfecta® enamel of the lamina dura is relatively normal but the teeth have an amber, yellowish-brown or translucent bluish-gray colour because of improper deposition of dentine

Laboratory tests

Serum calcium and phosphorus are normal
Alkaline phosphatase may be increased

Differential

Hypophosphatasia (low alkaline phosphatase in serum)
Achondroplasia ( no increased bone fragility)

Treatment

No specific treatment
Aim to provide and maintain function
Splintage of #'s with minimal immobilisation
Intra-medullary fixation (kebab)
Plaster immobilisation for fractures carries the added disadvantage that osteoporosis is increased and it is possible to enter into a vicious circle
Associated with difficulties during anaesthetics due to small size of thorax and poor respiratory function, larger size of the tongue relative to the jaw, small size® small blood volume

Prognosis

Congenital severe forms die in utero or soon after birth
Few live through puberty
Milder forms may have a near normal life expectancy

Type I

Inheritance

Autosomal dominant

Incidence

1 / 30,000 (commonest type)
Age at diagnosis birth to early childhood

Classification

IA No dentinogenesis imperfecta
IB Dentinogenesis imperfecta

Clinical Features

Osteoporosis® abnormal bone fragility
Distinctly blue sclera throughout life
Presenile hearing loss affects about 40%® need hearing aids (otosclerosis or nerve compression)
In 10% fractures present at birth, rest in infancy or childhood
Short stature of post natal onset usually falling between 2 and 3 standard deviations below the mean
Joint hyper laxity and skeletal deformities
About 20% of the adults in this group have kypho-scoliosis and in the remainder there is progressive loss of height resulting from platyspondyly and kyphosis

Type II

Inheritance

Autosomal recessive

Incidence

1 / 62,000

Clinical Features

Blue sclera
Extreme bone fragility
Often intra-uterine death
Born with multiple bony deformities
Facial appearance is typical with marked lack of ossification of the whole cranial vault which by palpation consists of numerous small plates of bone

Prognosis

Death in perinatal period or early infancy (intra-cranial haemorrhage)

Type III

Inheritance

Autosomal recessive

Incidence

Extremely rare
Age at diagnosis evident at birth or early infancy

Clinical Features

Bluish sclera at birth but becomes less blue with age
Severe bone fragility® deformity
Deformity of long bones skull and spine
Present congenitally or in early infancy with fractures
The smallest of all patients with OI if they survive
High childhood mortality and further mortality in the third decade because of complications of severe kypho-scoliosis
Codfish flattening of vertebrae

Prognosis

May survive into adult life
Death often due to the complications of severe scoliosis

Type IV

Inheritance

Autosomal dominant

Incidence

? Incidence, rare

Classification

IVA No dentinogenesis imperfecta
IVB Dentinogenesis imperfecta

Clinical Features

Normal sclera or if bluish at birth becomes normal
Bone fragility of varying severity
Hearing impairment less common than in Type I
Difficult to differentiate from Type III

Progressive diaphyseal dysplasia (Engelmann's disease)

Inheritance

Autosomal dominant

Incidence

Rare less than 1 / million
Age at diagnosis 1-2 years
Male more than Female

Clinical Features

Wasting of muscles and weakness
Delays in walking or running® presentation
Also pain or weakness of affected limbs
Delayed puberty and hypo-gonadism, dry hard skin, dental caries, ocular proptosis, anaemia and hepatosplenomegally may develop

X-Rays

Fusiform swelling / expansion of diaphysis of long bones
Affects middle 1/3 and spreads proximally & distally
Cortical surface becomes irregular
Medullary canal becomes almost obliterated

Laboratory tests

Alkaline phosphatase & urinary hyroxyproline may be increased
Hypocalcaemia and hyperphosphataemia
Positive calcium balance may be present

Differential

Polyostotic fibrous dysplasia
Multiple enchondromatosis
Juvenile Pagets
Heavy metal poisoning
Ewings sarcoma

Treatment

No specific treatment
NSAIDs may help pain
Steroids may help if NSAIDs fail

Cranio diaphyseal dysplasia

Clinical Features
Mental retardation
Cranial nerve palsies
Diaphysis of long bones thickened and irregular
X-Rays Thickening of skull & long bone diaphysis
Pathology
Progressive thickening of all parts of the skull
Prognosis
Main problems are neurosurgical & maxillo-facial

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Other Dysplasias and Related Conditions

Diastrophic Dwarfism

Inheritance

Unknown pathogenesis

Clinical Features

Severe dwarfism (rhizomelic, short limbs)
Often misdiagnosed as achondroplast
Associated with scoliosis and kypho-lordosis, equino varus deformities of feet, multiple joint contractures (hip, elbow, knee) and hip dislocation and acetabular dysplasia
Also associated with spinal stenosis, scoliosis and kyphosis, atlanto-axial instability
Cauliflower ears, cleft palate and hitch-hikers thumb

X-Rays

Short and thick long bones
Distorted flattened epiphyses® late ossification
Spina bifida occulta of the cervical spine in almost its entirety and cervical kyphosis

Cleidocranial dysplasia

Characterised by deficient or imperfect ossification of bones formed in membrane (clavicles, cranium). Also affects pelvis & bones of hands & feet.

Inheritance

Autosomal dominant (1/3 sporadic)

Incidence

? true incidence
Usually evident in first 2 years of life

Clinical Features

Large head relatively small face, drooping shoulders & narrow chest
One or both clavicles may be affected (usually middle or lateral 1/3, rarely the medial 1/3)
When bilateral can touch shoulders in front
Frontal, parietal and occipital bossing
Pelvic involvement nearly always symmetrical
May be muscular deficiencies associated with clavicle defect
Coxa vara may be a feature

X-Rays

Ossification of cranial portion of skull, not base affected
Multiple wormian bones
Pelvis® wide symphysis, rami improperly fused
Widening of SI joint
Spina bifida occulta in thoracic & lumbar spine
Ossification of tarsal & carpal bones delayed
Terminal phalanges hypoplastic
Extra epiphysis at proximal ends 2nd - 5th metacarpals & metatarsals

Pathology

? exact cause ?Failure of ossification of midline junction of bones

Treatment

Little if any functional defect
Coxa vara if present may require osteotomy

Pyknodysostosis

Inheritance

Autosomal recessive

Clinically

Short stature
Skull dysplasia with failed closure of sutures, hyoplastic jaw and Wormian bones
Hypo / dysplastic clavicles
Acro-osteolysis terminal phalanges
Koilonychia nails and recurrent fractures

Fibrous dysplasia

A benign fibro-osseous pathologic entity of undetermined aetiology
Characterised by expanding fibro osseous tissue in the interior of affected bones and is predominantly a lesion of the growing skeleton
Called a dysplasia because of the observed inherent lack of normal osteoid production leading to the formation of primitive fibre bone trabeculae

Incidence

Exact incidence unknown (not rare)
Male : Female 1:3
Not hereditary, all reported cases sporadic

Classification

Monostotic
Polyostotic
Polyostotic associated with endocrine abnormalities

Albrights disease:: Skin pigmentation
Polyostotic fibrous dysplasia
Precocious puberty (usually female)

Clinical Features

May be asymptomatic and present incidentally or with endocrine dysfunction
Almost any bone may be affected
Most common Femur, tibia, humerus, rib or facial bone
May® pain & limp if neck of femur involved
Polyostotic form usually more obvious with segmental involvement leading to pain, LLD, bowing of long bones & other deformities, coxa vara (shepherds crock deformity)
Pathological # not uncommon
May involve facial bones
Non skeletal manifestations: Abnormal cutaneous pigmentation (coast of Maine, irregular outline) evident in ~ 35% of cases
(Polyostotic) Hyperthyroidism, Cushings, acromegaly, hyperparathyroidism, and hypophosphataemic rickets
Endocrine dysfunction is almost restricted to females though a few cases of hyperthyroidism have been seen in males (sexual precocity, diabetes mellitis or hyperthyroidism)
Sexual precocity seen in ~ 20% of cases® grow more rapidly but early fusion of growth plates® short stature

X-Rays

Generally long bone lesions tend to involve the metaphysis and spread towards the diaphysis
Typical ground glass appearance of lesions
Cortex may be thinned by endosteal erosions but there is always a thin shell of cortex (unless® fracture)
Multi-locular appearance but the lesions are unicameral
In long bones lesions are usually metaphyseal extending into the diaphysis
CT demonstrates ground glass appearance of matrix
Bone scan® increased uptake

Investigations

May have an elevated alkaline phosphatase but not related to extent or activity of disease
Other biochemical parameters are normal

Pathology

Exact cause?® disorder of postnatal cancellous bone maintenance where normal bone undergoing physiologic lysis is replaced by an abnormal proliferation of fibrous tissue
Developmental abnormality of bone forming mesenchyme
Primitive fibrous tissue proliferates in bony medulla ? arrest of bone maturation
Bone is distorted with a smooth external surface
Medullary cavity replaced by gray-white tissue of rubbery consistency which is usually gritty on palpation
Histology® fibrous / collagenous tissue with poorly oriented fibre / bone trabeculae formed by osseous metaplasia of fibrous tissue. Multi-nuclear giant cells (3 - 20 nuclei) & foam cells may be seen with irregular spicular masses of bone lying in the fibrous matrix
The cells are well-spindled and the nuclei are elongated and densely chromatic with considerable amounts of intercellular collagen
There is a lack of osteoblasts lining the bony trabeculae
Bone is usually primitive (woven) in type rather than lamellar and coarse fibred containing numerous large lacunae with young cells
Small masses of cartilage are often found in about 10%
Histology® appearance of alphabet soup
Periosteal reaction to fracture is normal but endosteal callus formation is poor
Malignant transformation occurs in less than 0.5%
Increased pain or sudden progression ? Malignancy (osteosarcoma most common form)

Differential

Secondary hyperparathyroidism (Brown tumour)
Solitary bone cyst
Solitary or multiple enchondromata
Fibrous defects / non ossifying fibroma
EG
Neurofibromatosis
Paget's disease
ABC

Treatment

Indicated in pathological #, deformity or significant pain
Biopsy may be necessary for correct diagnosis
Lesions may recur after surgery
If using bone grafts use cortical struts as cancellous bone® become dysplastic

Prognosis

Spontaneous regression of lesions has never been observed
Lesions progress in childhood but stabilise with skeletal maturity
Pregnancy may stimulate activity in fibrous dysplasia
May® skeletal deformity
Sarcomatous change occurs in a very low number of cases
Recurrence rate in the Mayo clinic series was 21% for all methods of treatment of monostotic fibrous dysplasia as opposed to 36% for all methods of treatment of polyostotic fibrous dysplasia

Fibrodysplasia ossificans progressiva (Myositis Ossificans Progressiva)

Inheritance

Autosomal dominant (most sporadic)
Usually evident before 10 years
Male : Female 4:1

Clinical Features

Occasionally features evident at birth
Short hallux and thumb evident at birth
Egg shaped swellings appear first in neck, dorsal trunk & shoulder girdle which may be fluctuant with crepitus or hard from the outset
Associated with low grade fever
Torticollis is a common presenting complaint
Involvement of limbs distal to knees & elbows is rare
Does not involve smooth or cardiac muscle
X-Rays Columns of extra-skeletal bone of varying density

Pathology

Defect of connective tissue (myositis is a misnomer)
Progressive calcification® ossification of fascia, aponeurosis, ligaments, tendons, and connective tissue of skeletal muscle
Marked interstitial oedema is a feature

Differential

Congenital muscular torticollis (thumb & toe normal)
Dermatomyositis
Treatment
No specific treatment
Unable to alter course of disease
Prognosis
Steady progression of contracture, muscle wasting etc
Periods of acute exacerbation & remission
Leads to total disability

Nail patella syndrome

Characterised by abnormalities of nails, elbows and knees

Inheritance

Autosomal dominant
Linked to gene for ABO blood group

Clinical Features

Nail dystrophy most severe in thumbs (present in 98%)
Little finger rarely affected
Thumb nail may be absent, bifid or hemiatrophic
Absence or hypoplasia of patella
May present with recurrent dislocation
Associated hypoplasia of lateral femoral condyle
Increased carrying angle & hypoplasia of lateral side of elbow which may result in subluxation of radial head
Two types of pelvic dysplasia are associated "Iliac horns" (present in 75%) and prominence of ASIS

Treatment

No specific treatment
May require quads-plasty or realignment

Marfans disease

Inheritance

Autosomal dominant (variable expression)

Incidence

About 3 / 100,000
(25 - 30% appear to be new mutations)

Clinical Features

Tall stature ( more than 182cm) with disproportionate long limbs
Lower segment length more than upper segment
Arm span usually exceeds total height
Long thin face with normal intelligence
Elongated digits
Dislocation of lens and extreme myopia and strabismus is associated
Cardiac abnormalities also associated eg mitral valve prolapse (80%) and aortic dilatation, dissection and rupture are common
Pectus excavatum
Ligamentous laxity and joint hyper mobility® pes valgus & genu recurvatum
Patella alta® tendency to dislocation
Thumb protrudes beyond ulna border of clenched fist
Hernias are common
Scoliosis present in 50% of cases, often painful, early onset & rapid progression and spondylolisthesis is also common
Diagnostic Criteria

Positive family history
Cardiac disease (dilation of ascenting aorta & mitral valve prolapse)
Dislocation of lens (upwards and outwards)
Musculo-skeletal anomalies (scoliosis, ligamentous laxity, flat foot, spondylolisthesis, pectus excavatum etc)

Pathology

Defect in fibrilin component of elastin® reduced tensile strength

Treatment

No specific treatment, orthopaedic measure directed towards scoliosis, & joint laxity (pes valgus & patella dislocations)

Homocystinuria

Aetiology

An inborn error of methionine metabolism due to the deficiency of the enzyme cystathionine synthase

Inheritance

Autosomal recessive
Results in increased cystine in fibrilin® defect® similar features to Marfans

Clinical Features

Similar to Marfans but with mental retardation and joint stiffness rather than laxity and contracture of fingers is a feature
Pes cavus and scoliosis (30%), also kyphosis, genu valgum and dislocation of the lens (but downwards and inwards)

Investigation

Cyanide-nitroprusside in urine to detect homcystinuria in neonatal period

Treatment

High doses of Vitamin B6 (effective in about 50% of patients)
Low methionine diet and antithrombodic doses of aspirin are currently used

Acrocephalosyndactyly (Aperts disease)

Characterised by premature closure of cranial sutures and complex syndactyly of the hands and feet.

Inheritance

Autosomal dominant

Clinical Features

Head is peaked and vertically elongated
Exophthalmos secondary to increased ICP
Syndactyly of digits may be complete or partial

Treatment

Neurosurgical® skull osteotomy & interposition

Ehler's Danlos Syndrome

Inheritance

Autosomal dominant with wide variance in expression
Extensive genetic heterogenicity

Aetiology

Uncommon familial disorder of connective tissue relating to a genetic defect in Type I collagen
There are a number of genotypes related to this condition (11)
Results in joint and skin hyperextensibility, easy bruising, increased joint mobility and abnormal tissue fragility

Clinically

All patients have soft fragile skin and a tendency to form tissue paper scars
Associated with hypermobile joints and hernias
There are several distinct types but further heterogeneity is obvious within each group
Patients bruise easily
Narrow maxilla and hypermobile ears
Mitral valve prolapse and dilation of aortic root or sinus may occur
Associated with severe talipes equino varus, ocular and gastrointestinal anomalies
Wounds heal slowly and prolonged haemorrhage may follow trauma
Serious complications may arise from ruptured aneurism

Pseudarthrosis

Tibia

Between 40% and 80% are associated with neurofibromatosis

Incidence

Estimated to be 1 per 190,000 live births

Aetiology

Exact cellular mechanism is not known and despite a definite clinical relationship with neurofibromatosis a cellular cause and effect has not been proven

Proposed theories include;: Neurofibromatosis
Fibrous dysplasia
"Hamartomatous" tissue
Abnormal blood supply
Abnormal growth and maturation of bone
Proliferative constricting fibrous tissue ring about the lesion

Classification

Crawford

Type I:: Anterior bowing with increased cortical density
Type II:: Anterior bowing with a failure of tubulation and narrowed, sclerotic medullary canal
Type III:: Anterior bowig with a cystic lesion or prefracture
Type IV:: Anterior bowing with a frank fracture and pseudarthrosis usually involving the tibia and fibula

Boyd

Type I:: Anterior bowing and defect in the tibia at birth associated with other congenital abnormalities
Type II:: Anterior bowing and hour glass constriction of the tibia® spontaneous fracture by 2 years is the most frequent variety and is associated with neurofibromatosis
Recurrence is common
Type III:: Pseudarthrosis develops through a congenital cyst
Type IV:: Pseudarthrosis develops in a sclerotic segment of bone without narrowing® stress fracture
Type V:: Pseudarthrosis of the tibia occurs with a dysplastic fibula® pseudarthrosis of one or both bones (prognosis similar to Type II)
Type VI:: Pseudarthrosis occurs in association with an intra osseous neurofibroma or schwannoma (rare)

Clinically

About half are evident at birth, the remainder usually become evident by the age of 2 years
Present with anterior bowing of the tibia shortly after birth or acute fracture
Bowing is usually antero-lateral but may be antero-medial
Characterised by deossification of a weight bearing long bone, bending, pathologic fracture and inability to form normal callus in healing
At least half the cases are associated with neurofibromatosis, cafe au lait spots being common
The tibia in the lower 2/3 is the most commonly affected bone and the left slightly more frequently than the right
The fibula is also frequently involved and other long bones are not excluded (clavicle and radius particulary but having more than one bone involved in any one patient is extremely rare)
The limb and foot are often shorter than normal

Pathology

Inability to replace bone that is lost
Histologically the area of the pseudarthrosis, or the area immediately surrounding the lesion usually has the appearance of dense cellular, fibrous connective tissue with variable cartilaginous areas and sclerosis of bone ends
In some cases the tissue has the characteristics of fibrous dysplasis
Sometimes there is sufficient fibro-osseous metaplasia to stimulate normal repair but when weight-bearing is resumed the bone that has been formed melts away and refracture occurs® deformity
Formation of a false joint® term pseudarthrosis
Microscopically® monotonous pattern of purposeless fibrocytes, the spindle cells are rather small and there is little evidence of organisation into a pattern of trabeculation, collagen formation is usually ample but there is little attempt to form osteoid
There appears to be no defect in mineralisation if normal osteoid can be produced
Cartilage formation is entirely lacking or very scant

Treatment

Bowing of the tibia pre fracture or a pre pseudarthrosis lesion is best treated initially with a total contact orthosis which may delay or prevent a fracture and frank pseudarthrosis from developing
Operation
Paterson (1984) technique® rod & bone graft with electrical stimulation® 75% union (average time to union 7.2 months)
Boyd® double onlay bone graft
Free vascularised fibular graft
Bone transportation (Ilizarov technique)

May require amputation if unable to achieve a stable functional limb without deformity (about 50% of the patients with neurofibromatosis® amputation)
Leg length inequality is common and there may be a need for contralateral epiphyseodesis or rarely ipsilateral lengthening

Prognosis

50% of fractures will heal with firm internal fixation (IM nail prefered) and autogenous bone graft, the use of electrical stimulation after the first surgical procedure is controversial but the younger the child the less likely the fracture is to heal
If re-grafting is considered essential then electrical stimultion should be used
If failure of union ensues despite at least two of the above surgical efforts then microvascular transplantation is justified
Tendency for the condition to improve on skeletal maturity

Clavicle

Postulated to be related to the location and effect of the subclavian artery but is also related to neurofibromatosis
Failure of ossification of medial and lateral ossification centres of the clavicle (medial centre for inner 2/3, lateral for the outer 1/3)
All reported cases have been on the right side
Not related to birth trauma and associated with little functional dissability

Clinically

Painless lump
May have a shoulder droop
There is often asymmetry of axillary folds

X-Rays

No callus
Rounded bone ends

Treatment

Usually not indicated
If for functional or cosmetic reasons® bone graft and internal fixation

Proximal Femoral Focal Deficiency

(Aitken 1969)
Spectrum of abnormalities ranging from minimal hypoplasia of the femur to near total absence of the femur
Deficiencies may include LLD, malrotation of the proximal femur, instability of the hip joint and inadequacy of the proximal hip and thigh musculature

Classification

Class A: Represents the fullest expression of development, A femoral head is present with an adequate acetabulum and a very short femoral segment and pseudarthrosis present at the sub-trochanteric level.
At maturity a bony connection is present between the shaft and head of femur but in some cases pseudarthrosis is present in the femoral neck which does not heal
Class B: Femoral head is present in an adequate acetabulum, the femur is short, usually a bone tuft on the proximal femur. At maturity there is no connection between the head and proximal end of the femur
Class C: Characterised by a severely dysplastic acetabulum, there is no femoral head and the femur is short
Class D: Absence of the femoral head and acetabulum and the markedly deformed and shortened femoral shaft is not associated with a proximal tuft

Clinically

Characteristically shortened bulky thigh held flexed and abducted
Hip rotated externally
The incidence of associated anomalies in these children is high (68.9% in Aitkens' series) and longitudinal deficiency of the ipsilateral fibula is the most common concurrent anomaly

Investigation

MRI may demonstrate the presence of tissue not visualized on plain radiographs

Treatment

Reconstruct or amputate
No attempt at reconstruction made in patients with class C or D involvement
Early operation is recommended to prevent displacement of a pseudarthrosis and to encourage healing
1950 Van Nes described a procedure of osteotomising the tibia and rotating the distal tibial segment 180 degrees to change the arc of ankle joint motion in a manner that would simulate the knee action in a below the knee stump
Must have a stable hip and a femur that places the ipsilateral ankle at the level of the contra lateral knee
Children with bilateral PFFD generally walk quite well without any form of prosthetic restoration and surgical procedures almost always detract from their ambulatory independence rather than benefit them unless they have severe foot deformities
The treatment of these patients must be individualized on the basis of the limb length discrepancy, adequacy of the proximal musculature, degree of malrotation of the femur and stability of the proximal joint

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