Shortened Humerus or Femur, Schemes and Mind Maps of Medicine

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Shortened Humerus or Femur

This guideline was updated in August 2015 by Dr Jay Marlow, with input from members of the New Zealand Maternal Fetal Medicine Network.

Background

The shorterned humerus and femur has been an ultrasound finding associated with a number of conditions, including aneuploidy. However, it is more than likely, in isolation, to be a variation of normal. In conjunction with other ultrasound features it could be an indication of an underlying pathology, aneuploidy or syndrome.

Objective

To provide a consistent approach for the accurate diagnosis and management of fetuses found to have a shortened humerus or femur at the 18-20 week scan.

Definition

Short femur or humerus

• measurement below 2.5 centile for gestational age
• measurement less than 0.91 of that predicted by measured BPD Isolated or associated with other anomalies

Differential Diagnosis

Short femur associations:

• Isolated (2/3)
  1. Normal variation or constitutional
  2. Early onset fetal growth restriction (FGR)

Shortened Humerus or Femur: August 2015

Ultrasound

Femur and humerus length

• measured with bone perpendicular to ultrasound beam
• with epiphyseal cartilages visible but not included in measurement
• measure other long bones

Assessment for other structural abnormalities, evidence of skeletal dysplasia or FGR

• Shortened long bones are an indication for detailed careful ultrasound assessment rather than invasive testing
• Uterine artery Dopplers
  • Bilateral notching +/- increase resistance is demonstrated in up-to 90% of cases with early onset FGR - Associated with an increased risk of abruption, pre-eclampsia and intrauterine fetal demise
• Suboptimal imaging may necessitate follow up repeat scans or referral to exclude other abnormality
• It is important that the patient is aware that repeat or tertiary scans are being requested because of suboptimal images, and not because of a soft marker identified on scan

Shortened Humerus or Femur: August 2015

Investigation

Consider referral to a Fetal Medicine Centre for tertiary assessment for:

1. Evaluation for other causes - Detailed survey for other structural abnormality - Markers for skeletal dysplasia and manage accordingly - Markers (including uterine artery Dopplers) for early onset FGR and manage accordingly - Assess risk for aneuploidy, and establish apriori risk 2. Calculation of aneuploidy risk for T - Individual likelihood ratios to apply to the apriori risk can be accurately calculated using the negative (ie absence of) and positive (presence of) LR for each marker. - This can be automatically calculated using the online tool: http://onlinelibrary.wiley.com/doi/10.1002/uog.12364/suppinfo 3. Offer counselling with consideration of advanced screening (ie NIPS) or amniocentesis if: - Adjusted risk > 1: - Other structural abnormality - Note: NIPS may not be appropriate here (favour invasive testing) - Other indicators of aneuploidy - Parents wish definitive testing for aneuploidy rather than screening (favour invasive testing)

• NB: NIPS is currently only available to the patient with an out-of-pocket cost in NZ

Shortened Humerus or Femur: August 2015