- Discussion:
- most commonly presents at 14 to 36-months;
- bowleg deformity in children w/ short stature & may indicate skeletal dysplasia;
-
developmental knee alignment:
- normal knee alignment progresses from 10-15 deg of varus at birth to maximal valgus
angulation of 10-15 deg at age of 3-3.5 yrs;
- neutral alignment:
- neutral femoral-tibial alignment occurs at 12-14 months old;
- Greene: neutral femoral-tibial alignment at 14 months old;
- Exam:
- degree of varus& tibial torsion are specifically measured & recorded;
- a practical method of following the varus deformity is to trace the outline of the child's
legs on the paper cover the examination table;
- the parents can hold on to this until the next visit;
- alternatively, hold the child's ankle together and measure the distance between the knees;
- knee motion and ligamentous instability are also assessed;
- in older child w/ untreated infantile tibia vara, mild laxity of LCL is common,
but 14-36 mo. old child w/ this condition usually has ligamentous stability
that is within normal limits;
- Radiographs:
- physiologic bowing typically show flaring and bowing of tibia and femur in a symmetric fashion
and is normal in children < 2 years of age (maximal at about 18 mo);
- physiologic genu valgum, or knock knees, develops next, w/ maximal deformity
occurring at 3 years of age;
- gradual correction to ultimate alignment of slight genu valgum occurs by 9 years
of age in the great majority of patients;
-
ref:
-
Physiological bowing and tibia vara. The metaphyseal-diaphyseal angle
in the measurement of bowleg deformities.
- Differential Dx:
- Physiologic Bowing:
- most common cause of genu varum;
- becomes most apparent during the second year;
- involves both the femur and the tibia;
- can be assocated with
internal tibial torsion;
- some orthopaedists will attempt to diminish this type of varus w/ casting;
- references:
-
Normal limits of knee angle in white children--genu varum and genu valgum. ³
- Distal tibial deformity in bowlegs.
WW Robertson Jr.
J. Pediatric Orthopaedics.
Vol 7. 1987. p 324.
-
Blounts Disease:
- Trauma:
-
Osteogenesis Imperfecta
-
Osteochondroma
-
Hypophosphatemic rickets:
- its sex-linked dominant inheritance may lead to early diagnosis;
- short stature & genu varum are apparent;
- ht at initial dx is usually <10 % & always< 25th
- abnormal genu varum is seen in 95 % of these pts;
- characterized by widening or rachitic-like changes at physis;
- low serum phosphorus levels distinguish hypophosphatemic rickets from metaphyseal chondrodysplasia;
-
Metaphyseal chondrodysplasia:
- an inherited disorder of bone growth that also causes bowing of lower extremities;
- characterized by widening or rachitic-like changes at physis;
- in the Schmidt subtype (most common), the height and limb alignment are w/in norml limits at birth,
but genu varum persists & retarded growth is seen in preschool yrs;
- low serum phosphorus levels distinguish hypophosphatemic rickets from metaphyseal chondrodysplasia;
Normal limits of knee angle in white children--genu varum and genu valgum. ³
Use of the Metaphyseal-Diaphyseal Angle in the Evaluation of Bowed Legs.
Tibia vara caused by focal fibrocartilaginous dysplasia.
Three case reports.
SN Bell et al.
JBJS. 67-B (5). 1985. p 780-784.
Varus deformity of the distal end of the femur secondary to a focal fibrous lesion.
CA Vallcanera et al.
Pediatric Radiology. Vol 24. 1994. p 74-75.
The development of the tibiofemoral angle in children.
P. Salenius and E. Vankka.
JBJS Vol 57-A. 1975. p 259-261.
Genu varus and valgus in children.
CE Shopfner and CG Coin.
Radiology. Vol 92. 1969. p 723-732.
Variability of the Metaphyseal-Diaphyseal Angle in Tibia Vara: A Comparison of Two Methods.
