Radiological Sequelae of developmental dysplasia of the hip: a Review

Transcription

1 Radiological Sequelae of developmental dysplasia of the hip: a Review Poster No.: P-0037 Congress: ESSR 2012 Type: Scientific Exhibit Authors: S. G. Flanagan, J. Sarkodieh, K. Mcdonald, M. Ramachandran, R. Jalan; London/UK Keywords: Congenital, Treatment effects, Normal variants, Education, Ultrasound, MR, Conventional radiography, Anatomy, Pediatric, Musculoskeletal joint, Pathology, Dysplasias DOI: /essr2012/P-0037 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 21

2 Purpose Review the pathophysiology of DDH Outline the principles of neonatal screening using USS Outline radiological features of DDH Review complications arising from DDH Methods and Materials Introduction to DDH Developmental dysplasia of the hip (DDH) is an enitity encompassing a range of pathology including congenital dislocation of the hip (CDH), subluxation and degrees of joint instability. A broader definition is that of abnormal hip joint growth and development. This encompasses problems with osseous development and soft tissues such as the joint capsule. Epidemiology + risk factors Reported incidence rates vary between 1.5 and 20 per 1000 live births. There is an increased incidence in female children, breech presentation, first born children and conditions associated with oligohydramnios. There is a possible genetic predisposition to DDH in children of parents who were themselves affected. The left hip has been reported as more commonly involved and this may be secondary to the position of the intrauterine hip against the maternal sacrum, placing the joint in adduction. Hip adduction caused by swaddling of an infant in certain cultures has also been implicated as a risk. Page 2 of 21

3 Natural history Unstable hips detected clinically in neonates have a high rate of resolving by week 1 (>60%) and almost all will resolve by 2 months (88%). The remainder will have residual hip instability and may require treatment to avoid complications. Complications that arise from DDH result from joint instability and malalignment. There is a risk of subluxation and dislocation in the child and an increased incidence of early onset osteoarthritis. Results Principles of neonatal screening All neonates are routinely checked for hip instability by the clinical team. The classic tests are the Ortolani and Barlow manouvers, which involve stressing the joint to induce a 'clunk' of subluxation or reduction. Neonates at our unit who are clinically suspected to have an element of hip instability are referred for USS screening. High risk neonates (breech presenters etc) are also screened. USS is used in infants prior to femoral head ossification (<6months) as it allows assessment of the capsule and dynamic viewing of the joint during stress. beyond 6 months, plain films are used. USS screening involves cooperation between the sonographer and the orthopaedic surgeons. The child is scanned in the lateral position, and both hips are reviewed at rest and under stress. Page 3 of 21

4 Fig. 1: Normal USS anatomy A-Ilium B Acetabular labrum C-Gluteus muscles DCapsule E-Femoral head Various angles have been described to assess the position of the femoral head and relative morphology of the acetabulum. The Alpha angle is formed between the vertical cortex of the ilium and the acetabular o roof. Normal Alpha angle is >60. The Beta angle is derived from the ilium cortex and triangular labral fibrocartilage (the so o. called echogenic triangle). Normal Beta angle is <55 Page 4 of 21

5 Fig. 2: A= Alpha angle B= Beta angle At our institution, a more useful assessment is thought to be the degree of femoral head coverage. That is the percentage of the head lying within the bony acetabulum. Greater than 50% is considered normal. Page 5 of 21

6 Fig. 5: Normal hip coverage A= outside acetabulum, B= Within acetabulum. On plain film the femoral head position is assessed relative to the ilium and acetabulum. The degree of ossification is also reviewed, with delayed ossification being a feature of DDH. Several lines are employed in the formal assessment of the hip: Page 6 of 21

7 Fig. 3: A= Hilgenreiners line B= Perkins' line C= Acetabular angle D= Shenton's line Page 7 of 21

8 Hilgenreiners line is drawn horizontally through the top of both triradiadte cartilages. It is used as a reference for Perkin's line Perkin's Line lies perdendicular to Higenreiners lines, and intersects the lateralmost edge of the acetabulum. The normal position of the femoral head lies in the inferomedial quadrant of the lines. the Acetabular angle is formed by a line drawn tangential to the acetabular roof and o Hilgenreiners line. At birth it is normally <30 and is increased in DDH. Shenton's line follows the inferior border of the superior pubic ramus and continues smoothly along the inferomedial border of the proximal femur. Breaks in the line indicate migration of the proximal femur. Radiological features of DDH Diagnostic features of DDH rely on assessing the relationship of the femoral head and acetabulum, and the morphology of both. Page 8 of 21

9 Fig. 4: Right sided DDH, Proximal translation of the femur with an increased acetabular angle. Page 9 of 21

10 Fig. 9: Stress view USS, showing greatly reduced coverage of the femoral head and a shallow acetabulum. Page 10 of 21

11 Fig. 10: L sided DDH with delayed ossification of the femoral head relative to the normal side. The acetabulum appears shallow Page 11 of 21

12 Fig. 11: Coronal CT reformat- shows abnormal position of right proximal femur and delayed head ossification Complications Complications arise from the inherent instability of the joint. treatment is initially nonsurgical, with the aim to place the hip in joint and in abduction to encourage normal femoral head and acetabular development. This is achieved using a Pavlik harness or a hip spica cast. Page 12 of 21

13 Fig. 6: Dislocation is a common complication of DDH. The neo-articulation of the femoral head and ilium can be seen. Page 13 of 21

14 Page 14 of 21

15 Fig. 12: Following chronic dislocation, a pseudoarthrosis develops between the femoral head and the ilium. This weightbearing view demonstrates this. Fig. 13: Delayed presentation: The femoral head on the left is almost completely unossified. Note the dysplastic, shallow acetabulum Surgical treatment is reserved for those with delayed diagnosis or those in whom previous conservative measures have failed. Treatment involves the acetabulum, femur, soft tissues or a combination of the three. Osteotomies of the proximal femur aim to reduce the coxa valga or anteversion associated with DDH. Pelvic osteotomies aim to reduce the acetabular angle and increase the depth and coverage of the acetabulum. Page 15 of 21

16 Post operative complications include avascular necrosis and fracture. Fig. 7: Left DDH treated with pelvic osteotomy and proximal femoral osteotomy. Note the degree of coxa vara from the femoral osteotomy. Page 16 of 21

17 Fig. 14: Right DDH treated with pelvic osteotomy. There has been development of a degree of avascular necrosis, note the flattening of the femoral head Page 17 of 21

18 Fig. 15: Adult pelvis, DDH treated with childhood osteotomies. There is residual dysplasia of the acetabulum and a degree of flattening of the femoral head. Page 18 of 21

19 Fig. 16: MRI of the same patient as fig 16 Note the oedema within the acetabulum with a small osteochondral defect. The femoral high signal relates to the previous osteotomy Page 19 of 21

20 Fig. 8: Axial T1W MRI showing dysplasia of the left femoral head and post osteotomy appearance of the acetabulum. The head is abnormally positioned superio-laterally with a trace of oedema within the posterior hip Conclusion This poster illustrates the principle imaging features of DDH and outlines the appearances of complications in the untreated and post surgical groups. References Page 20 of 21

21 Clarke N, Reading I,et al; Twenty years experience of selective secondary ultrasound screening for congenital dislocation of the hip, 2012, Arch Dis Child doi: / archdischild American Academy of Pediatrics; Screening for Developmental Dyspasia of the hip: Recommendation Statement, 2006, Pediatrics; 117;898 Fujii M, Nakashima Y et al; Intraarticular findings in symptomatic developmental dysplasia of the hip, 2009, J Pediatr Orthop;29:9-13 Shorter D, Hong T et al; Screening programmes for developmental dysplasia of the hip in newborn infants, 2011, Cochrane Database Syst Rev;9:CD Personal Information Flanagan S.G, Sarkodieh J, McDonald K, Jalan R: Radiology Department, Barts and the London NHS Trust, London, UK Ramachandran M, Orthopaedic Department, Barts and the London NHS Trust, London, UK Page 21 of 21