· syn. Legg-Calve-Perthes disease, coxa plana, osteochondritis deformans juvenilis, pseudocoxalgia
· disorder of the capital femoral epiphysis in young children of unknown aetiology
· is an osteochondrosis characterised by avascular necrosis and disordered enchondral ossification
· described in separate publications in 1910 by Legg (Boston), Calve (France) and Perthes (Germany)
· incidence varies
· 1 in 1 200 in USA
· 1 in 12 000 in UK
· onset at age 4-8
· range age 1-14
· boys more common
· M:F 4:1
· bilateral in 10%
· abnormal birth presentation
· later-born children
· older parents
· lower SE group
· racial variation
· more common in Orientals, Eskimos, central Europeans
· less common in blacks
· unknown association
· involved children usually
· have low birth weight
· have growth lag (bone age lower than chronological age by 1-3 yrs)
· have delayed growth (are shorter)
· have disproportionate growth (smaller distal segments)
· exact cause unclear
· caused by disruption of blood supply to capital femoral epiphysis
· proposed causes are
· trauma to retinacular vessels
· transient synovitis with vascular occlusion secondary to increased intracapsular pressure
· venous obstruction with secondary intrepiphyseal thrombosis
· increased blood viscosity
· may be primary cartilagenous dysplasia
Initiation
· initially, ischaemic episode of unknown cause occurs
· renders entire capital femoral eiphysis avascular
· enchondral ossification in the preosseous epiphyseal cartilage and growth plate ceases temporarily
· articular cartilage nourished by synovial fluid and continues to grow
· results in smaller ossific nucleus but wider cartilage space
· revascularisation of the epiphysis and resumption of enchondral ossification occurs from the periphery
· new immature woven bone deposited on dead trabeculae
· avascular bone resorbed
· resorption exceeds deposition in subchondral area
· critical point reached and subchondral bone becomes weak and susceptible to pathological fracture
· pathological subchondral fracture occurs
· usually results from normal vigorous activity
· pain from fracture heralds clinical onset
Capital femoral epiphysis changes
· fracture typically begins in anterolateral aspect of epiphysis near physis
· greatest concentration of weight-bearing stress here
· fracture extends superiorly and posteriorly
· revascularised cancellous bone beneath subchondral fracture undergoes secondary ischaemic episode secondary to fracture
· area undergoes creeping substitution
· avascular bone slowly resorbed from periphery of area of second infarction
· replaced by vascular fibrous tissue
· eventually replaced by primary woven bone
Physeal changes
· blood supply to physis comes from epiphysis
· thus there are secondary ischaemic changes
· chondrocyte columns become distorted and do not undergo normal ossification
· result is excess of calcified cartilage in primary cancellous bone
· growth may be disturbed with premature closure of the physis
Metaphyseal changes
· four metaphyseal changes seen
· adipose tissue
· osteolytic lesions (circumscribed areas of unossified fibrocartilage)
· disorganised ossification
· extrusion of growth plate down sides of femoral neck
Femoral head changes
· potential for deformity of femoral head due to
· biological plasticity - during creeping substitution, femoral head can be moulded into round or flat shape
· asymmetrical growth - areas not undergoing resorption grow faster
· episodes of painful synovial reaction and consequent adductor contraction can lead to
· anterolateral subluxation of femoral head
· loss of hip ROM
· femoral head then subjected to excessive and unevenly distributed forces that can deform it
· results in flattening of the head or development of saddle-shaped deformity
· further anterolateral subluxation and extrusion can then occur
· continued growth along extruded growth plate along femoral neck and periosteal new bone formation along femoral neck lead to enlarged femoral head (coxa magna)
Femoral neck changes
· cessation of longitudinal growth means there is failure of femoral neck to grow
· result is short thick femoral neck (coxa breva)
· greater trochanter continues to grow from apophyseal plate
· high greater trochanter together with short femoral neck leads to functional coxa vara (no real change in neck-shaft angle)
· result is disturbance of hip abductors with Trendelenburg gait and positive Trendelenburg sign
· short femoral neck also leads to lower limb length discrepancy
Initial
· four signs
Cessation of growth of ossific nucleus
· due to lack of blood supply
· slight but progressive difference in size of involved epiphysis
Increased density of ossific nucleus
· nucleus radiodense
· physeal plate irregular
· metaphysis blurry
Increased medial joint space
· medial cartilage (joint) space appears larger because of continued growth of articular cartilage
Subchondral fracture
· subchondral radiolucent zone (crescent sign)
· extent of zone (and fracture) determines extent of subsequent capital femoral epiphyseal resorption
· duration of visibility varies with
· age of patient (3 months in age 4, to 9 months in age 10)
· extent of fracture
Fragmentation
· necrotic epiphyseal bone beneath subchondral fracture gradually and irregularly resorbed
· replaced by vascular fibrous tissue
· gives radiographic appearance of fragmentation
Reossification
· irregular process starting in subchondral area and progressing centrally
· eventually, newly formed areas of bone coalesce and capital femoral epiphysis regains normal strength
· normal bone density returns
Healed
· capital femoral epipysis completely reossified and femoral head is healed
· proximal femur left with any residual deformity
· radiological classifications
· plain AP and Lauenstein lateral (frog leg) x-rays used
· may classify
· phase (Waldenstrom)
· extent of femoral head involvement (Catteral, Salter-Thompson, Herring)
· end-result (Mose, Stuhlberg, Sundt)
A - evolutionary period
Initial stage
· epiphysis denser, patchy, more distal, uneven at margins
Stage of fragmentation
· epiphysis in pieces
B - healing period
· epiphysis becomes homogenous
· evidence of diffuse and extensive revascularisation
C - growth period
· normal growth and ossification of head
· postulated that extent of involvement of epiphysis directly proportional to extent of involvement of femoral head on x-ray
· relies on maximum extent of resorption (late in disease)
· problems
· significant intra-observer error
· group to which lesion assigned may not remain constant
Group 1
· 25% of head involved in anterocentral region
· no formation of sequestrum
· no metaphyseal reaction
· no subchondral fracture line
Group II
· 50% of head involved in anterolateral region
· sequestrum present with clear junction
· anterolateral metaphyseal reaction
· subchondral fracture line in anterior half
Group III
· 75% of head involved
· large sequestrum with sclerotic junction
· diffuse anterolateral metaphyseal reaction
· subchondral fracture line in posterior half
Group IV
· 100% of head involved
· central or diffuse metaphyseal reaction
· posterior remodelling
· only 2 statistically significant groups
· difference is presence or absence of intact lateral margin
· may shield epiphysis from collapse and deformity
· extent of subchondral fracture correlates completely with subsequent extent of maximal resorption
· subchondral fracture nearly always visible in early stages (first 4 months)
· thus classification can be applied early but may be difficult late
Group A
· Catteral 1 and 2
· less than 1/2 of femoral head involved
· viable lateral margin (lateral pillar present)
· good prognosis
Group B
· Catteral 3 and 4
· more than 1/2 of femoral head involved
· involved lateral margin (loss of lateral pillar)
· poorer prognosis
· lateral pillar classification
· sectors of femoral head derived by noting location of lines of demarcation between central sequesrum and remainder of epiphysis
· fragmentation occurs in distinct sectors or pillars
· lateral pillar - lateral 15-30% of head width
· central pillar - central 50% of head width
· medial pillar - medial 20-35% of head width
Group A
· no involvement of lateral pillar
· all become Stuhlberg I and II
Group B
· > 50% of lateral pillar height maintained
· outcome depends on age
· if < age 9
· almost all become Stuhlberg I and II
· if > age 9
· 30% become Stuhlberg II
· 70% become Stuhlberg III or IV
Group C
· < 50% of lateral pillar height maintained
· majority do poorly
· 30% become Stuhlberg II
· 70% become Stuhlberg III or IV
· quantifies degree of sphericity
· transparent template with concentric circles at 2 mm intervals placed on x-rays and centred over femoral head
· graded according to variance from perfect circle in either AP or lateral
· no variance rated good
· up to 2 mm variance rated fair
· 3 mm or more variance rated poor
· uses
· Mose grading
· size of femoral head
· length of femoral neck
· Sharp angle
· degree of femoral coverage
Class 1
· head normal
Class II
· head spherical
· evidence of one or more of
· coxa magna
· coxa breva
· increased Sharp angle
Class III
· head ovoid but not flat
Class IV
· congruous incongruity
· head flat
· acetabulum flat
Class V
· incongrous incongruity
· head flat
· acetabulum not flat
· shape of head on AP may be
· spherical
· ovoid
· cylindrical
· quadrangular
· initially said that most patients will
· have some pain
· lead normal lives
· at 20-40 yrs after onset of symptoms
· 80% are active and pain-free
· only 10% have THR
· only 40% have normal radiographs
· at 50 yrs after onset of symptoms
· 50% have disabling pain
· 40% have THR
· osteoarthritis 10x more prevalent than general population
Age of onset
· most significant factor
· the older the age, the worse the prognosis
· good prognosis if age < 6
· poor prognosis if age > 10
· found that
· if age < 5, all Stuhlberg I and II
· if age 5-9, any class I to V
· if age > 9, all Stulberg III to V
· related to amount of skeletal growth and thus skeletal remodelling available
· ability for acetabular remodelling continues to age 8
· bu poor results do occur in children < age 5 at onset of disease
Sex
· outcome less favourable in girls than boys
· reason unclear
· usually more extensive
· mature earlier so less remaining skeletal growth
Extent of involvement of femoral head
· the greater the extent, the worse the prognosis
· quantified by Caterall and Salter-Thompson classifications
· good outcome with Caterall I and II and Salter-Thompson A
Containment of the femoral head
· loss of containment due to
· extrusion
· subluxation
· asymmetric growth
· leads to worse prognosis
Range of hip movement
· the less the range, the worse the prognosis
· loss of hip ROM can be caused by
· hip irritability
· deformity of femoral articular surface
· loss of ROM prevents adequate remodelling of femoral head by acetabulum
Premature epiphyseal growth plate closure
· usually with severe epiphyseal involvement (Salter-Thompson B)
· damage to growth plate may lead to premature physeal closure
· femoral neck fails to grow in length and remodelling of femoral head limited
Catteral's 'head at risk' signs
· mark onset of deformity of femoral head
· signs are
· Gage sign (circumscribed area of defective ossification in lateral epiphysis and adjacent metaphysis)
· calcification lateral to epiphysis
· lateral subluxation
· diffuse metaphyseal reaction
· horizontal angle of physis
· most common presentation is insidious onset of limp
· may be intermittent ache in groin, anterior thigh or knee
· onset may be more acute
· may be history of trauma (usually mild)
· because symptoms mild, presentation usually weeks or months after onset
Antalgic gait
· shortened stance phase on affected side
· can be reflex inhibition of hip abductors with positive Trendelenburg test
Muscle spasm
· best detected by roll test
· patient relaxed and supine
· examiner rolls limb in and out detecting resistance at hip
· complete range of movement needs to be tested
· typical finding is mild limitation of movement
· esp. abduction and internal rotation (best seen prone)
· may be fixed flexion deformity
Proximal thigh atrophy
· result of disuse due to prolonged irritability and resultant loss of ROM
· best determined by measurement
Leg length discrepancy
· inequality indicative of significant head collapse
Short stature
· affected children usually short because of delayed bone age
· AP and frog-leg lateral views
· number of assessments made
· stage of disease
· extent of subchondral fracture
· degree of collapse
· sphericity
· extrusion (containment)
· may be useful to assess sphericity of articular surface early in resorption stage
· contour of partially resorbed ossific nucleus may not reflect articular contour
· may demonstrate hinge abduction
· hinge abduction occurs when adducted hip brought into abduction
· overgrown articular cartilage of femoral head bulges out from under lateral aspect of acetabular roof
· abduction produces impingement and causes hip to hinge at this point
· may be used to detect potential Perthes disease
· absence of uptake indicative of ischaemia or AVN
· difficult to interpret and quantify
· less accurate than plain x-ray
· extremely early diagnosis of little practical use
· helps define
· area of infarction
· femoral head contour
· does not involve radioactive dye or radiation
· role yet to be defined
· transient synovitis
· acute phase of bacterial infections of hip joint
· septic arthritis
· osteomyelitis
· Gaucher's disease
· sickle cell disease
· epiphyseal dysplasia
· avascular necrosis secondary to
· trauma
· treatment for CDH or SUFE
· is local, self-healing disorder
· most patients do not need treatment (60%)
· prevention of femoral head deformity
· prevention of secondary osteoarthritis
· interfere as little as possible with child's development
Restoration of movement
· joint movement
· enhances synovial nutrition and cartilage nutrition
· allows abduction of hip which allows positioning of uncovered anterolateral head in acetabulum
· hip irritability usually present after subchondral fracture
· decreased ROM may lead to contracture of adductors and psoas
· acute irritability overcome by
· strict RIB for 1-2 weeks using slings and springs
· progressive abduction
· maintenance of ROM may require
· active and passive ROM exercises
· adductor tenotomy
· most important indicator is range of abduction in extension
· satisfactory is 30o or 75% of unaffected side
Containment
· originally, treatment based on premise that avascular femoral head was physically soft and relied on relief of weight bearing
· treatments recommended long periods of complete and prolonged bed rest combined with weight-relieving devices, for 2-3 years
· found that none of these methods substantially decreased compressive forces across hip joint and caused significant complications
· now concept of containment developed
· to prevent deformities of diseased epiphysis, femoral head must be contained in depths of acetabulum
· equalises pressure on head
· subjects it to moulding action of acetabulum
· containment leads to
· more spherical femoral head
· more congruous joint
· decreased risk of early osteoarthritis
· two methods of containment
· nonoperative
· surgical
Observation only
· long-term studies have shown that children < age 6 generally have excellent prognosis regardless of degree of epiphyseal involvement
· observation appropriate for
· all children under age 6 at clinical onset
· children age 6 or older with Salter-Thompson group A involvement with no limitation of motion and no subluxation of hip
Intermittent symptomatic treatment
· for loss of ROM
· brief periods (1-2 weeks) of traction, springs and slings or crutches combined with abduction stretching exercises
Definitive early treatment
· indicated when
· age at clinical onset is 6 years or older AND
· Salter-Thompson group B involvement AND
· loss of containment seen on x-ray
· prerequisites
· good hip ROM
· no residual irritability
· round or nearly round femoral head
Late salvage
· indications
· femoral head deformity
· secondary osteoarthritis
· head contained by placing hip in abduction
· worn until reossification phase
· usually 6-18 months
Abduction cast
· Petrie cast
· long-leg casts to both lower extremities
· held in 30o abduction and 5o internal rotation and secured with 2 bars
· advantages
· desired position maintained
· compliance assured
· disadvantages
· cause stiffness in knees and ankles
· restricts mobility
· casts need frequent changing
Abduction brace
· best-known is Scottish Rite brace
· advantages
· lighter and less cumbersome
· better tolerated
· disadvantages
· expensive
· decreased compliance as can be removed
· advantages
· period of restriction less (< 2 months)
· containment permanent
· permanence of containment continues to enhance remodelling
· disadvantages
· risks of surgery
Varus osteotomy
Rationale
· seats head deeply in acetabulum
· removes vulnerable anterolateral portion from acetabular edge
· decreases joint forces on femoral head
· relieves venous hypertension
Prerequisites
· initial or fragmentation stage
· full ROM
· joint congruency
· ability to contain head in abduction and internal rotation
Technique
· varus closing medial wedge
· sufficient varus to permit entire ossified epiphysis to be covered by ossified acetabulum
· avoid excessive varus (<115o neck-shaft angle)
· keep greater trochanter distal to femoral neck
· derotation
· external rotation of distal fragment
· to enhance coverage
· held with plate
Advantages
· operation on affected side of joint
· technically less demanding
Disadvantages
· increase in leg length discrepancy
· potential coxa vara
· Trendelenberg gait
· requirement of removal of metal
· risk of fracture through screw-holes after removal
Innominate osteotomy
Rationale
· redirection of acetabulum provides better coverage for anterolateral femoral head
Prerequisites
· initial or fragmentation stage
· full ROM
· joint congruency
Technique
· Salter technique (as for CDH)
Advantages
· avoids disadvantages of femoral osteotomy
Disadvantages
· technically more difficult
· operating on normal side of joint
Combined
Rationale
· enlarged uncovered head cannot be contained adequately with either femoral or innominate osteotomy
Indications
· severe disease in older patients
Advantages
· provides containment
· avoids
· shortening
· Trendelenberg limp
Disadvantages
· major procedure
Indications
· significant femoral head deformity that
· prevents reduction into acetabulum
· produces hinge abduction
· failure of containment techniques
Muscle release and arthrotomy followed by abduction casts
· if head still in re-ossification phase
· may be able to achieve sufficient abduction so that deformed antero-lateral head can be reduced and entirely contained in acetabulum
· adductor tenotomy, iliopsoas release and arthrotomy performed
· Petrie cast for 3-4 months
Partial excision of femoral head
· in form of peripheral cheilectomy
· when containment not achieved with muscle release and arthrotomy
· extruded rim of cartilage and bone excised
· should be deferred until physis has closed
· raw cancellous bone may lead to joint stiffness and late osteoarthritis
Valgus osteotomy of femur
· alternative to cheilectomy
· indicated when x-ray indicates hip congruency better in adduction
Distal and lateral transfer of greater trochanter
· relieves Trendelenburg gait
· decreases pressure between femoral head and acetabulum
· methods as for other forms of secondary degenerative arthritis
· femoral osteotomy
· arthrodesis
· arthroplasty