The Utility of Computer Tomography to Assess Acetabular Morphology in Morquio Brailsford Syndrome

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The Utility of Computer Tomography to Assess
Acetabular Morphology in Morquio - Brailsford
Syndrome

• Andrzej Borowski MD, Aaron G. Littleton BSc,
  Mihir M. Thacker MD, Leslie Grissom MD, William
  G. Mackenzie MD

EPOS/IFPOS Combined Meeting, Sorrento, Italy 2007
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Introduction

• Morquio - Brailsford syndrome (MS) is an
  inherited metabolic lysosomal storage disorder,
  one of the large groups of mucopolysaccharidosis
  (MPS).
• Alterations in connective tissue lead to abnormal
  formation and growth of the skeletal system.
• Hip dysplasia is common in these patients, yet
  little has been reported as to the location and
  severity of the acetabular deficiency in these
  patients.

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Aim

• The purpose of this study was to evaluate
  morphology (shape) of the acetabulum in Morquio
  Brailsford syndrome using two-dimensional CT
  scans.
• We set out to determine the location and extent
  of acetabular abnormalities by comparing our
  measurements to age-matched normal values.

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Methods
Acetabular Version Intersection of the
tangential line drawn from the anterior to the
posterior rim of the acetabulum and a
perpendicular line to a line connecting the
posterior ischia or triradiate cartilages.
Anteroposterior radiograph of a patient with
Morquios disease shows a severe dysplastic
acetabulum
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Methods
Posterior Acetabular Index The angle formed by
the intersection of a line drawn through the
anterior aspect of the triradiate cartilage and a
line drawn from the postero-lateral corner of the
triradiate cartilage to the posterior acetabular
rim.
Anterior Acetabular Index The angle formed by the
intersection of a line drawn through the anterior
aspect of the triradiate cartilage and a line
from the antero-lateral corner of the triradiate
cartilage to the anterior acetabular rim.
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Results

• The average acetabular anteversion angle was
  10.9 (range, 5-24) with a 4.6 average
  difference between our study population and
  age-matched normal hips.
• The average anterior acetabular index was 58.8
  (range, 50-70) with 10.6 average difference
  between our study population and age-matched
  normal hips
• The posterior acetabular index was 53.8 (range,
  35-70) with 3.8 average difference between our
  study population and age-matched normal hips.
• Calculated axial acetabular index ranged from 90
  to 133 (mean 112.6, 14.5 average difference
  from age-matched normal)

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Results

• The average femoral head coverage was 27.4
  (range, 0-60 sd 23.1) with a 54.7 average
  difference between our study population and
  age-matched normal hips.
• Although there are a limited number of patients,
  there is a high degree of variability in coverage
  with a standard deviation of 23.
• This can partially be explained by the fact that
  5 of the 14 hips had no femoral head coverage.
• Of those femoral heads that were located in the
  acetabulum, the average coverage was only 42.6.

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Discussion

• New imaging techniques and technology have
  greatly facilitated evaluation of hip morphology,
  leading to improvement in understanding and
  planning of surgical treatment in dysplastic
  hips.
• Computed tomography enables the surgeon to
  evaluate the global shape of the acetabulum and
  location of acetabular deficiency for the
  preoperative assessment and therefore is critical
  for selecting the appropriate procedure required
  for reconstruction of the acetabulum.

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Conclusion

• 2-D computer tomography of the hip in patients
  with Morquios disease demonstrated a severe
  dysplasia of the anterior acetabular wall as well
  as the roof of the acetabulum.
• The acetabular version, though was normal.
• Treatment of hip dysplasia in Morquio
  Brailsford syndrome should focus on increasing
  the overall depth of the acetabulum to better
  contain the femoral head.

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