4.9g Limb Deficiency: Longitudinal Postaxial (Fibula, Ulna, Fifth Ray) (Q71.30, Q71.5, Q72.30, Q72.6)

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Postaxial limb deficiency is characterized by absence or hypoplasia of the fifth toe/finger (sometimes also including the fourth toe/finger) with or without absence/hypoplasia of the fibula or ulna (see Fig. 4.40). Radiographs are strongly recommended to confirm the findings and characterize the bony anomalies.

Fig. 4.40. Longitudinal postaxial

Relevant ICD-10 codes

Q71.5 Longitudinal reduction defect of ulna
Q72.6 Longitudinal reduction defect of fibula
Absence of fibula
Q71.30 Congenital absence of finger(s) with remainder of hand intact
Q72.30 Congenital absence or hypoplasia of toe(s) with remainder of foot intact

Note: Avoid using the generic Q71, Q72 or Q73 codes for longitudinal postaxial limb deficiencies. These generic codes include otherlimb reduction defects.

When using Q71.30 – congenital absence of finger(s) with remainder of hand intact – or Q72.30 – congenital absence or hypoplasia of toe(s) with remainder of foot intact – be sure to denote which fingers and toes are affected to be able to differentiate from transverse terminal defects.

Diagnosis

Prenatal. Longitudinal postaxial limb deficiencies might be diagnosed or strongly suspected prenatally. However, they can be missed. The distinction from other limb deficiencies is difficult and error-prone. For this reason, a prenatal diagnosis should always be confirmed postnatally.

When this is not possible (e.g. termination of pregnancy or unexamined fetal death), the programme should have criteria in place to determine whether to accept or not accept a case based solely on prenatal data.

Postnatal. The newborn examination can identify a longitudinal postaxial limb deficiency and distinguish it from other limb deficiencies (e.g. longitudinal postaxial defects). An accurate and complete diagnosis requires a detailed physical examination aided by radiography to characterize completely the bony anatomy.

Clinical and epidemiologic notes

Absence or hypoplasia of the ulna typically affects only one arm. With complete absence of the ulna, there is often a marked flexion deformity of the elbow. The hand can be straight or angulated to the ulnar side of the wrist.

Ulnar deficiency is less common than radial deficiency. Ulnar hypoplasia is often associated with radioulnar synostosis (fusion of the radius and ulna), absence of the postaxial digits (fourth and fifth fingers) and fibular deficiency.

Some associations and syndromes described with postaxial defects include the following:

femur-fibula-ulna complex, characterized by the unilateral absence or hypoplasia of the ulna, femur and fibula;
ulnar-mammary syndrome (a genetic condition), characterized by deficiencies of the ulna, fibula and postaxial digits; hypogenitalism; and absence of one or both breasts/nipples; and
Miller syndrome, in which facial differences are associated with postaxial deficiencies of the upper limb.

Distinguishing longitudinal postaxial defects from other limb reduction defects is important because these conditions have different causes and associated anomalies. With careful clinical and radiological examination, the diagnosis of longitudinal postaxial limb deficiencies is possible.

The reported prevalence of postaxial limb deficiencies is approximately 0.45 per 10 000 births.

Inclusions

Q71.30 Congenital absence of finger(s)
Q71.5 Longitudinal reduction defect of ulna
Q72.30 Congenital absence or hypoplasia of toe(s) with remainder of foot intact
Q72.6 Longitudinal reduction defect of fibula

Exclusions

Q71.31 Absence or hypoplasia of thumb
Q71.4 Longitudinal reduction defect of radius
Q71.6 Congenital cleft hand
Q72.31 Absence or hypoplasia of first toe with other digits present
Q72.5 Longitudinal reduction defect of tibia
Q72.7 Split foot

Checklist for high-quality reporting

Checklist for high-quality reporting
Longitudinal Postaxial Defects – Documentation Checklist
Describe in detail, including: Limbs involved. Note each segment involved for each limb affected – describe what is deficient or absent. Indicate involvement of ulna, fibula, fourth–fifth finger, fourth–fifth toe, and others. Laterality – right, left, bilateral. Document specialty consultations (e.g. genetics, orthopaedics). Use Fig. 4.35 to distinguish longitudinal postaxial defects from other subtypes of limb deficiencies. Describe procedures to assess further additional malformations and, if one or more is present, describe these. Describe procedures to assess syndromes. Distinguish from other longitudinal and transverse limb deficiencies (e.g. longitudinal preaxial). Take and report photographs: Very useful; can be crucial for review. Take and report radiographs: Crucial for review and classification, at times even more than photographs. Report whether specialty consultation(s) done, and if so, report the results.

Suggested data quality indicators

Suggested data quality indicators
Category	Suggested Practices and Quality indicators
Description and documentation	Review sample for documentation of key descriptors: Take and attach radiographs and photographs – essential for review and correct classification. Specify which limbs are involved and laterality. Specify affected segments (hand, forearm, foot, leg). Specify affected bones.
Coding	Track and minimize cases coded with generic ICD-10 RCPCH codes: Q71, Q72, Q73.
Clinical classification	Syndromes are not frequent in longitudinal postaxial defects. A high proportion of syndromes suggests misclassification with preaxial limb deficiencies
Prevalence	Prevalence is around 0.45 per 10 000 births. A much higher or lower prevalence suggests misclassification with other limb deficiencies.
Key visuals	Distinguishing longitudinal postaxial defects from longitudinal preaxial defects (side-by-side comparison):