Etiology: exact cause unknown.
1.Mechanical intrauterine stresses affecting hip development;
2.Avascular necrosis of selected areas of the proximal femoral physis/head and neck; &
3. Metabolic abnormalities -deficient production of or, a delay in the normal ossification process of the proximal femur
Pylkkanen proposed: proximal femoral deformity -the result of a primary ossification defect in the inferior femoral neck, on which physiologic shearing stresses (applied during weight-bearing)→ fatigue of the local dystrophic bone → progressive varus deformity.
Pathophysiology: -cartilaginous physis or ossification center defects of proximal femur leading to a.↓ed proximal femoral neck-shaft angle & b. vertical proximal femoral physis. (The coxa vara and vertical physis increases sheering forces of physis & compressive forces of inferior medial neck)
Clinical Features: usual presentation time- from start of ambulation to 6 years; parents complaining of- limping & shortening of leg of the child.
-Gait abnormalities, progressive & pain free.
-Unilateral involvement: limb-length discrepancy & Trendelenburg gait.
-Bilateral involvement: waddling gait abnormality,.
-The Trendelenburg sign:+nt.
– weak abductors, a prominent greater trochanter,
-↓ed abduction (due to a ↓ed articulo-trochanteric distance) &
-A decrease in internal rotation (due to ↓ed femoral anteversion or presence of true retroversion).
Radiography:- 1. X-ray-
Congenital coxa vara differentiated from other forms of coxa vara by the presence of an inverted Y-shaped lucency (formed by proximal physeal plate and a fragment of bone inferolateral to the physis; a contained area of abnormal calcification).
-Other findings: ↓ed femoral anteversion or even retroversion ; coxa brevis; &, sometimes a shallow oval acetabulum.
2. CT Scan with 3D-reconstructions: to see proximal femoral defect; femoral anteversion or retroversion & the amount of bone stock in the area (important for preop planning of Sx).
3. MRI: limited role- to see the widening of the growth plate & expansion of cartilage mediodistally between the capital femoral epiphysis & the femoral metaphysis.
TREATMENT: -No role of conservative treatment in progressive disease.
*No treatment needed if:
-No clinical symptoms on examination
-X-ray shows Hilgenreiner epiphyseal angle (HEA) < 45° (folow-up with periodic radiological evaluation)
-HEA =45-60° with no documented progression (follw-up to see any progression).
-A child with a clinical limp & HEA > 60°
-A child with a clinical limp & an HEA= 45-60° with documented progression of varus deformity
Goals of the treatment:
-Correction of the neck shaft angle (to a more physiologic level) & HEA < 35-40°
-Correction of femoral anteversion (or retroversion) to more normal value
-Ossification & healing of the defective inferomedial femoral neck fragment
-Reconstitution of the abductor mechanism.
-Amount of correction needed
-Associated procedures during surgery to aid in the osteotomy & decrease hip joint forces
-Optimal age for operation
*Surgery delayed until the child is 4 or 5 yrs old ( internal fixation easier).
Surgical Options:- 1. Subtrochanteric Valgus Osteotomy-e.g. Borden; to place the femoral neck & head in adequate valgus position with the shaft of femur. Fixation with blade plate/screw-plate.
2. Intertrochanteric Osteotomy– e.g. Pauwels Y-shaped & Langenskiöld valgus-producing osteotomies- minimal correction of retroversion.
-Immobilization in ‘Hip-spica Cast’ until complete union (upto 8-12 weeks).
-Regular follow-up to see any recurrence of the deformity, or, development of limb-length discrepancy (needs additional treatment)