Top Ten Adult Manifestations of Childhood Hip Disorders





Congenital, developmental, and acquired conditions of the pediatric hip frequently present with sequelae in the adult. There is substantial overlap in the end-stage results of these pathologic conditions, including osseous changes, chondral/labral injuries, and premature osteoarthritis. This review discusses the top 10 etiopathogeneses of pediatric hip conditions and presents associated dysmorphisms in the adult on an illustrative, multimodality, case-based template. Quantitative imaging metrics and the role of advanced imaging techniques are reviewed. The ultimate goal is enhanced understanding of the expected evolution of childhood hip pathologic conditions and their associated complications for general radiologists.


Key points








  • Pediatric hip pathologic conditions arise from various etiopathogeneses but frequently display common morphologic and functional outcomes.



  • Specific radiographic views and quantitative imaging metrics are useful for assessing mechanics and congruity of the hip joint.



  • Altered joint mechanics in the adult arising secondary to pediatric hip pathologic conditions can result in labral and chondral injury with premature osteoarthritis.




Introduction


To accurately assess the hip, the practicing radiologist should have familiarity with its anatomic components and the standard imaging techniques used to visualize them. The hip is a ball-in-socket joint with the femoral head articulating within the acetabulum. The femoral head and acetabulum are lined with hyaline cartilage to absorb shock and decrease friction during articulation. The fibrocartilaginous labrum attached to the bony acetabular rim both stabilizes the hip and seals in joint fluid to promote even load-bearing. Any incongruence in femoral head-acetabular articulation can promote uneven cartilage wear and weight-bearing and premature cartilage breakdown. Both femoral head dysplasia and acetabular dysplasia can result in pathologic weight-bearing, early breakdown of articular cartilage, labral loading and injury, proliferative bone formation leading to CAM (an abbreviation for “camshaft,” an automotive analogy describing the shape, which the femoral head and neck resembles) and pincer impingement, and premature osteoarthritis. These pathologic outcomes are common endpoints for a wide variety of different pediatric hip pathologic conditions.


This review discusses the top 10 etiopathogeneses of pediatric hip conditions and presents associated dysmorphisms in the adult on an illustrative, multimodality, case-based template. Quantitative imaging metrics and the role of advanced imaging techniques are reviewed. Imaging discussion is supplemented with case presentations, key radiology pearls, and discussion of treatment modalities. The ultimate goal is enhanced understanding of the expected evolution of childhood hip pathologic conditions and their associated complications for general radiologists.


Imaging techniques and normal anatomy


Five basic radiographic views are generally sufficient to accurately evaluate the adult hip: the anterioposterior (AP), lateral, frog-leg-lateral, Dunn, and false profile views ( Fig. 1 ). Radiographic technique for each of these views is summarized in Table 1 . Frequently referenced anatomic hip landmarks are summarized in Fig. 2 . Specific imaging metrics frequently used for quantitative analysis of plain radiographs of the hip are summarized in Table 2 . Excellent pictorial summaries of these metrics have been previously published. A summary of several of the more advanced imaging modalities commonly used to evaluate the adult hip is summarized in Table 3 .




Fig. 1


Hip radiograph projections: AP ( A ), lateral ( B ), frog-leg ( C ), Dunn ( D ), and false profile ( E ).


Table 1

Radiograph technique








































Projection Patient Position Tube Position Clinical Utility Quantitative Radiographic Metrics
AP Supine
Hips 15° internal rotation
Beam perpendicular to table at 120 cm
Crosshairs centered between PS and ASIS
Acetabular morphology Acetabular depth
Acetabular version
Acetabular index (sharp index)
Tonnis angle
LCEA (angle of Wiberg)
Femoral head sphericity
Femoral head lateralization
Congruency
False profile Standing
Symptomatic hip against cassette
Symptomatic foot parallel to cassette
Pelvis 65° to cassette, facing beam
Beam perpendicular to patient at 102 cm
Crosshairs centered on femoral head
Acetabular morphology ACEA (angle of Lequesne)
Congruency
Lateral Supine
Contralateral hip and knee flexed 80°
Symptomatic hip 15° internal rotation
Beam parallel to table 45° to symptomatic limb
Crosshairs centered on femoral head
Proximal femur Femoral head sphericity
Femoral head neck offset congruency
Frog-leg lateral Supine
Ipsilateral knee flexed 30°–40°
Symptomatic hip abducted 45°
Heel against contralateral knee
Beam perpendicular to table at 102 cm
Crosshairs centered between PS and ASIS
Proximal femur Femoral head sphericity
Femoral head neck offset
Alpha angle a
Congruency
Dunn Supine
Symptomatic hip and knee flexed 90°
Symptomatic hip abducted 20°
Beam perpendicular to table at 102 cm
Crosshairs centered between PS and ASIS
Proximal femur Femoral head sphericity
Femoral head neck offset
Congruency

Criteria for technical adequacy: coccyx in line with pubic symphysis; iliac wings, obturator foramen, and teardrops symmetric; upper border of pubic symphysis to tip of coccyx 1 to 3 cm.

Abbreviations: ACEA, anterior center edge angle; ASIS, anterior superior iliac spine; OA, osteoarthritis; PS, pubic symphysis.

a Approximate; true angle traditionally measured on cross-sectional oblique CT or MR imaging.




Fig. 2


Hip anatomic landmarks on an AP pelvic radiograph: posterior acetabular rim (violet); anterior acetabular rim (purple); teardrop (red); iliopectineal line (yellow); ilioischial line (green); acetabular sourcil (edges marked by light blue and yellow circles).


Table 2

Hip imaging metrics (hip pathologic condition by morphology)




















































































Imaging Modality Normal Clinical Significance (Abnormal) Common Pertinent Hip
Pathologic Conditions
CAM deformity
Alpha angle Axial MR imaging or CT <55⁰ CAM deformity LCPD
SCFE
Intraarticular osteoid osteoma of hip
AIIS avulsion
Femoral head neck offset Any lateral radiograph >0.17 CAM deformity LCPD
SCFE
Intraarticular osteoid osteoma of hip
AIIS avulsion
Pincer deformity, acetabular dysplasia
LCEA AP radiograph 25°–40⁰ Decreased: structural instability
Increased: pincer impingement
DDH
PFFD
Charcot hip
Inflammatory/infectious arthritis
LCPD
ACEA AP radiograph 20°–45⁰ Decreased: structural instability
Increased: pincer impingement
DDH
PFFD
Charcot hip
Inflammatory/infectious arthritis
LCPD
Acetabular depth AP radiograph Floor of acetabulum does not abut/cross ilioischial line on AP radiograph Pincer impingement Infectious/inflammatory arthritis
Femoral head lateralization AP radiograph >10 mm Structural instability DDH
Charcot hip
Acetabular index (Sharp index) AP radiograph <45⁰ Structural instability DDH
PFFD
Charcot hip
LCPD
Tonnis angle AP radiograph 0°–10⁰ Increased: structural instability
Decreased: pincer impingement
DDH
PFFD
Charcot hip
LCPD
Joint alignment
Acetabular version AP radiograph 13°–20⁰ anteversion Pincer impingement SCFE
Femoral version Axial MR imaging or CT 8°–14⁰ anteversion Excessive retroversion risk factor for poor outcomes after corrective FAI surgery DDH
FAI
SCFE
Joint congruity
Femoral head sphericity AP and lateral radiograph Any portion of femoral head >2 mm beyond standard Mose template Joint wear and early OA DDH
PFFD
Charcot hip
LCPD
Infectious/inflammatory arthritis
IHC

Abbreviations: ACEA, anterior center edge angle; FHC, femoral head center.


Table 3

Summary of basic and advanced hip imaging modalities




















Imaging Modality Views/Sequences Clinical Utility
Plain radiograph AP
Lateral
Frog-leg lateral
Dunn
False profile
Evaluate acetabular and femoral morphology and congruence
Preoperative and postoperative assessment
Routine surveillance imaging
CT Axial, coronal, and sagittal views
3D modeling
Assess complex fractures and hip dysmorphologies
Preoperative planning with automated hip measurements
Assessment of hip version
MR imaging Conventional 3 T imaging: dedicated hip coils, parallel imaging, isotropic MR
MR arthrography, ± traction
Biochemical MR imaging: dGEMRIC, T2 and T2*, T1 rho, Na+ mapping
3D modeling
Virtual ROM analysis
Open MR imaging (functional imaging)
3D printing
Advanced metal suppression
MR fingerprinting
Assessment of cartilage and labral injuries
Biochemical cartilage mapping (dGEMRIC, T2/T2*, T1 rho, Na + mapping)
Automated analysis of joint parameters, for example, alpha angle via 3D modeling
Subject-tailored preoperative virtual planning
Dynamic ROM simulation
Real time in vivo functional imaging

Abbreviations: AP, anterior posterior; dGEMRIC, delayed gadolinium-enhanced MR imaging of cartilage; Na + , sodium; ROM, range of motion.


Two scenarios are generally encountered when evaluating adult hip disease arising secondary to childhood hip pathologic conditions in daily clinical practice:




  • The disease process and pathophysiology are known, in which case the radiologist is following hip morphology for interval change.



  • The disease process is unknown, and the radiologist is evaluating hip morphology to assist in diagnosis of the underlying pathologic condition.



It is most helpful, therefore, to organize commonly encountered hip pathologic conditions by both morphology ( see Table 2 ) and etiopathogenesis ( Tables 4 and 5 ).



Table 4

Hip pathologic conditions by etiopathogenesis: developmental/congenital






























Etiopathogenesis Pathophysiology/Mechanism Imaging Features Abnormal Imaging Metrics Possible Operative Findings
Developmental/congenital
DDH Lateralized femoral head
Acetabular undercoverage
Coxa valga
Femoral lateralization
Hip subluxation
AD
Premature OA/cartilage damage
LCEA/ACEA
Acetabular index
Tonnis angle
Periacetabular osteotomy
Femoral varus osteotomy
Hip resurfacing arthroplasty
Total hip arthroplasty
PFFD


  • Abnormal mesenchymal development




    • Dysmorphic femoral head



    • Shortened femur




  • Loss of developmental acetabular molding

Coxa vara
Femoral head deformity
Proximal femoral deficiency
AD
LCEA/ACEA
Acetabular index
Tonnis angle
Various femoral lengthening procedures
Charcot hip a Sensory/autonomic neuropathy
Insensate bone imperceptible trauma
Hyperemia bone breakdown
Femoral head deformity
Femoral lateralization
Pseudoarticulation
AD
Premature OA/cartilage damage
Acetabular index
Acetabular depth
Tonnis angle
Total hip arthroplasty

General assessment of the above includes AP and lateral radiographs, MR imaging (cartilage/labral assessment), and CT (3D bone morphology, operative planning, and so forth).

Abbreviations: ACEA, anterior center edge angle; AD, acetabular dysplasia; OA, osteoarthritis.

a Congenital neuropathic hip most frequently related to spina bifida, Chiari malformations, and syringomyelia.



Table 5

Hip pathologic conditions by etiopathogenesis: acquired
















































Etiopathogenesis Pathophysiology/Mechanism Imaging Sequela Abnormal Imaging Metrics Possible Operative Findings
Acquired
LCPD Loss of blood flow to femoral head
AVN
Relative CAM deformity
Femoral head deformity
CAM deformity
AD
Premature OA/cartilage damage
LCEA
Acetabular index
Femoral head neck offset ratio
Alpha angle
Femoral varus osteotomy
Periacetabular osteotomy
Femoral neck lengthening
Innominate osteotomy
Shelf procedure
SCFE


  • Anterior/lateral slippage of femoral neck




    • Pathologic stress a



    • Pathologic physeal weakness b




  • Relative CAM deformity

Femoral head deformity
CAM deformity
Premature OA/cartilage damage
Acetabular version
Femoral head neck offset ratio
Alpha angle
Femoral head pinning
Proximal femoral osteotomy
Femoral head/neck osteochondroplasty
Infectious/inflammatory arthritis


  • Inflammatory change/hyperemia




    • Premature triradiate/physeal closure



    • Femoral head erosion/AVN



    • Acetabular deformity




  • Possibly idiopathic (eg, JIA)

Femoral head deformity
Femoral lateralization
Coxa vara/valga
Leg length discrepancy
AD
Joint ankylosis/heterotopic bone
Premature OA/cartilage damage
Femoral head sphericity
Tonnis angle
Acetabular index
Femoral head extrusion index
Pelvic acetabuloplasty
Femoral varus/valgus osteotomy
Epiphysiodesis with contralateral leg lengthening
Trochanteric arthroplasty
Total hip arthroplasty
IHC Idiopathic rapid destruction of hip cartilage Symmetric joint space narrowing
Periarticular osteopenia
Acetabular protrusion
Joint ankylosis/heterotopic bone
Premature OA/cartilage damage
Acetabular depth
Acetabular index
Tonnis angle
Total hip arthroplasty
Osteoid osteoma of the hip


  • Benign bone tumor




    • Reactive hyperemia



    • Bone proliferation


Lucent nidus with surrounding sclerosis (minority of intraarticular cases)
Coxa valga
Widening of femoral neck (CAM deformity)
Premature OA/cartilage damage
Alpha angle
Femoral head neck offset ratio
Osteochondroplasty
Traumatic avulsion Repetitive stress (athletics)
Direct trauma
AIIS hypertrophy, malunion, or nonunion
Heterotopic bone formation
CAM deformity
Alpha angle (concurrent CAM deformity)
Femoral head neck offset ratio
AIIS osteochondroplasty
Femoral head/neck osteochondroplasty

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Aug 15, 2020 | Posted by in GENERAL RADIOLOGY | Comments Off on Top Ten Adult Manifestations of Childhood Hip Disorders

Full access? Get Clinical Tree

Get Clinical Tree app for offline access