Circles are Pointless - Angles in the assessment of adult hip dysplasia are not!

Transcription

1 Circles are Pointless - Angles in the assessment of adult hip dysplasia are not! Poster No.: C-1964 Congress: ECR 2014 Type: Authors: Keywords: DOI: Educational Exhibit S. E. West, S. G. Cross, J. Adu, S. G. Flanagan; London/UK Developmental disease, Congenital, Diagnostic procedure, Plain radiographic studies, Musculoskeletal system, Musculoskeletal bone /ecr2014/C-1964 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 15

2 Learning objectives Learning Objectives: Is this normal? Figure 1: AP x-ray of adult female pelvis - normal? In this presentation, we aim to enable you to answer this question and interpret this radiograph correctly. To enable the radiologist to recognize and detect the signs of developmental dysplasia of the hip in the mature adult pelvis, in particular before the onset of degenerative changes. To appreciate there is a narrow window for patients with hip dysplasia where newer hip preservation procedures can be performed with excellent results. These results are directly linked to the degree of degenerative changes that have already developed. Therefore early recognition and diagnosis is essential. There are several key angles that are important in assessing the adult pelvic x-ray with suspected hip dysplasia. We will illustrate these and thus providing useful tools for the radiologist to aid in interpreting these films. Images for this section: Page 2 of 15

3 Fig. 1: AP x-ray of adult female pelvis - is this normal? Page 3 of 15

4 Background What is DDH in the adult? Developmental dysplasia of the hip is a condition where the femoral head and acetabulum have not developed normally. There is a spectrum ranging from complete dislocation to insufficient coverage of the femoral head. Whilst many patients are identified and successfully treated in childhood there is a small proportion that present in adulthood. They fall in to 2 main groups: 1) treated in childhood but new onset of symptoms in adulthood due to a persisting abnormality. 2) completely missed in childhood and presenting for the first time as an adult. Table 1 lists the risk factors for hip dysplasia. There is an 8:2 female to male ratio [1] It is more commonly unilateral but can be bilateral in 20% of cases [2]. It can account for significant pain and morbidity in a young patient population, initially due to labral pathology and then as a result of degenerative change. Table 1 Risk factor Female>male Breech position First born Oligohydroaminos Positive family history Connective tissue disorders associated with hyperlaxity Why is it important for the radiologist to know the radiographic features of hip dysplasia in the adult? Hip preservation procedures for hip dysplasia are predominantly focused on using osteotomies around the acetabulum to reorient the shallow acetabulum (Peri-acetabular osteotomy or PAO) and thus provide a better load-bearing surface for the patient. This restores previously abnormal biomechanics that would otherwise lead to degenerative changes [3]. Page 4 of 15

5 There are multiple studies that show that the outcomes of these procedures are strongly linked to the degree of degenerative change that has already developed by the time the patient presents for surgery [4-6]. This is independent of patient age. Millis et al showed that patients with grade 2 tonnis cartilage changes who underwent a PAO were 2.2 times more likely to need a hip replacement than those with grades 0 or 1 [5]. If this narrow therapeutic window is missed and degenerative changes are already established the only option left to the patient is to undergo a total hip replacement, which at a young age is far from ideal. The radiologist is very often the first hospital specialist the patient encounters. Many of these patients present to their GP with symptoms related to their hip and are sent for plain radiographs of the pelvis. The report the GP receives can have a significant impact on the subsequent path the patient takes. Findings and procedure details There are several angles around the acetabulum that can be measured to help assess for hip dysplasia. There are cases where changes are obvious (figure 2), especially if the patient has undergone surgery in childhood, or has grossly dysplastic changes. The aim is not to point out the obvious but to allow identification of the more subtle cases. It is this subgroup that can have significant symptoms pre-arthritis and now have surgical options open to them, thus avoiding prolonged morbidity secondary to pain and the need for a total hip replacement at a young age. Figure 2- AP pelvis radiograph showing bilateral aspherical and flattened femoral heads. There is decreased joint space bilaterally with acetabular and femoral sclerosis and subchondral cysts indicating advanced degenerative changes. Angle of Weiberg or Lateral centre edge angle: This is evaluated on the plain AP film of the pelvis and gives an indication as to how well covered the femoral head is and its degree of lateralization. Normal is degrees with an angle less than 20 degrees being diagnostic for DDH. The angle is measured by taking a vertical line through the centre of the femoral head and another line through the lateral edge of the sourcil (the superior weight bearing zone Page 5 of 15

6 of the bony acetabulum). Figure 3 shows the plain x-ray and figure 4 shows the same x-ray, this time labelled. Figure 3- AP pelvis radiograph Figure 4 - AP pelvis radiograph. There is abnormal remodelling of the lateral aspects of the femoral heads bilaterally with significant reduction in the lateral central edge angle bilaterally, diagnostic for DDH. The femoroacetabular joint spaces are preserved. An os acetabula is present on the left (an Os acetabula, a calcified part of the labrum, is associated with poorer outcome after PAO surgery [7]. Incidental note is made of osteitis pubis. Acetabular angle of Sharp: This is a measure of how shallow the acetabular roof is. It is measured by taking the inferior aspect of the tear drop and drawing a line horizontally and then a further line from the same point to the most lateral edge of the sourcil. It should measure between degrees with anything large indicating a shallow acetabulum and dysplasia. This is illustrated in figure 5-7. Figure 5: Same patient as in figures 3 and 4 showing bilaterally increased acetabular angles of Sharp. Figure 6 - AP radiograph of pelvis Figure 7 - AP radiograph of pelvis. There is upward sloping of the left, superior acetabulum, with lateralization of the femoral head. The joint spaces are preserved. The acetabular angle of sharp is widened on the left to 42.7 degrees and marginally wider on the right. Although not marked on this radiograph the lateral centre edge angle of this patient on the right is 9 degrees and the left 23 degrees. Tonnis angle or acetabular index: This is a marker of the obliquity of the weight bearing zone of the acetabulum. It is sometimes referred to as the 'horizontal toit extreme angle. It is measured by taking a horizontal line from the most medial point of the acetabular sourcil and then from this Page 6 of 15

7 point to the most lateral point. It should not be greater than 10 degrees. This is illustrated in figure 8. Figure 8 - AP radiograph of same patient as in figures 6 and 7. The acetabular index is marked on the left side and is increased to 24 degrees. Studies have show the inter and intra-rater reliability of measurement of these angles is poor, particularly in the smaller angles where the margin for error is greater [8]. We feel that they are still a useful tool in providing objective measurements to the general radiologist in assessing the AP radiograph of the pelvis in young patients with hip pain. Images for this section: Page 7 of 15

8 Fig. 2: Figure 2 - AP pelvis radiograph showing bilateral aspherical and flattened femoral heads. There is decreased joint space bilaterally with acetabular and femoral sclerosis and subchondral cysts indicating advanced degenerative changes. Fig. 3: AP pelvis radiograph Page 8 of 15

9 Fig. 4: AP pelvis radiograph. There is abnormal remodelling of the lateral aspects of the femoral heads bilaterally with significant reduction in the lateral central edge angle bilaterally, diagnostic for DDH. The femoroacetabular joint spaces are preserved. An os acetabula is present on the left (an Os acetabula, a calcified part of the labrum, is associated with poorer outcome after PAO surgery [7]. Incidental note is made of osteitis pubis. Page 9 of 15

10 Fig. 5: Same patient as in figures 3 and 4 showing bilaterally increased acetabular angles of Sharp. Page 10 of 15

11 Fig. 6: AP radiograph of pelvis Page 11 of 15

12 Fig. 7: AP radiograph of pelvis. There is upward sloping of the left, superior acetabulum, with lateralization of the femoral head. The joint spaces are preserved. The acetabular angle of sharp is widened on the left to 42.7 degrees and marginally wider on the right. Although not marked on this radiograph the lateral centre edge angle of this patient on the right is 9 degrees and the left 23 degrees. Page 12 of 15

13 Fig. 8: AP radiograph of same patient as in figure 5. The acetabular index is marked on the left side and is increased to 24 degrees. Page 13 of 15

14 Conclusion Hip dysplasia is a condition that can cause significant morbidity in a young adult population. Surgical procedures are available to correct the deformity and improve the biomechanics of the hip that can otherwise lead to degenerative changes and the need for joint replacement. These changes are strongly linked to the degree of arthritis that has already developed with the higher success rates being in those with no or minimal changes. The radiologist plays a vital role in the early detection of the radiographic changes seen in this group and can have a significant impact on the clinical path the patient progresses on. We have illustrated the radiographic changes that can be seen in the pre-degenerative changes group and provided objective tools to assess these. Personal information Dr Sophie West MBBS BSc. MSc. MRCS Department of Radiology Royal London Hospital Whitechapel E1 1BB sophie.pinder@doctors.org.uk References 1. Sewell MD, Rosendahl K, Eastwood DM. Developmental dysplasia of the hip. BMJ2009;339:b Lewis K, Jones DA, Powell N. Ultrasound and neonatal hip screening: the five-year results of a prospective study in high-risk babies. J Pediatr Orthop1999 Nov-Dec;19(6): Troelsen A. Surgical advances in periacetabular osteotomy for treatment of hip dysplasia in adults. Acta Orthop Suppl Apr;80(332):1-33. Page 14 of 15

15 1. Clohisy JC et al. Pericaetabular Osteotomy: A systematic review of the literature. Clin Orthop Relat Res (2009) 467: Millis MB et al. Periacetabular Osteotomy for Acetabular Dysplasia in Patients Older than 40 Years: A Preliminary Study. Clin Orthop Relat Res (2009) 467: Biedermann R et al. Complications and patient satisfaction after periacetabular pelvic osteotomy. International Orthopaedics (SICOT) (2008) 32: Troelsen A et al. Medium-term outcome of periacetabular osteotomy and predictors of conversion to total hip replacement. J Bone Joint Surg Am Sep;91(9): Engesaeter IO et al. Radiological findings for hip dysplasia at skeletal maturity. Validation of digital and manual measurement techniques. Skeletal Radiol DOI /s Page 15 of 15