CASE                               26                               

A 2-year-old African-American girl presents with progressive bowing of her legs. On physical examination, she has asymmetric genu vara with a lateral thrust.

Radiographs demonstrate bilateral Langenskiöld stage II proximal tibial changes.

What treatment should this child undergo?

1. Gradual corrective proximal osteotomies with multiplanar frame

2. Hemiepiphysiodesis of the lateral proximal tibae

3. Valgus osteotomies of the proximal tibiae

4. Knee–ankle–foot orthoses (KAFO)

5. Observation

Discussion

The correct answer is (D). For Langenskiöld stage II changes in the proximal tibia for infantile Blount disease, which is the most common form of the disease, KAFO wear has been shown to improve the lower extremity deformity in children less than 3 years old with stage I and II changes. Valgus osteotomies of the proximal tibias are reserved for Langenskiöld stages II to VI changes in ages <3 years old, stages I to II changes in children >3 years old, or failure of KAFO treatment. Hemiepiphysiodesis has been attempted in younger children with uncertain results and is reserved for adolescent (>10 years old) Blount disease treatment. Gradual corrective osteotomies are reserved for the skeletally mature patient to limit neurovascular stretch injury. Observation is not recommended for Langenskiöld stage II infantile Blount disease.

She returns at age 3 for follow-up. What metaphyseal– diaphyseal angle (Drennan’s angle) is consistent with a 95% chance of progression?

1. Less than 5 degrees

2. 5 to 10 degrees

3. 12 degrees

4. 16 degrees

Discussion

The correct answer is (D). The angle between the metaphyseal beak, proximal tibial metaphysis, and perpendicular to the tibia at the physis is the metaphyseal–diaphyseal angle (Drennan’s angle). An angle of >16 degrees (answer D) is considered abnormal and has a 95% chance of progression. A Drennan’s angle of

<10 degrees has a 95% chance of resolving over time.

For a 3-year old who has progressive tibia vara despite KAFO treatment and a

Drennan’s angle of >16 degrees, what is the treatment?

1. Gradual corrective proximal osteotomies with multiplanar frame

2. Hemiepiphysiodesis of the lateral proximal tibia

3. Valgus osteotomies of the proximal tibia to neutral alignment

4. Valgus osteotomies of the proximal tibia with overcorrection

5. Continue knee–ankle–foot orthoses (KAFO)

Discussion

The correct answer is (D). As discussed, treatment for children with failure of KAFO treatment (progression of deformity), valgus osteotomies are the treatment of choice in this age group with approximately 10 degrees of overcorrection to decrease recurrence and decrease the load on the medial tibia (answer D). Anterior compartment releases are often performed to decrease the risk of compartment syndrome. Recurrence of the deformity decreases if the osteotomies are performed before age 4.

At her post-op visit, the family presents her 10-year-old sister with unilateral tibia vara. You would like to get a radiograph and the technician is having difficulty achieving a true AP.

What other rotational deformities are present in adolescent Blount disease?

1. Distal tibial varus

2. Internal tibial torsion

3. Recurvatum of the proximal tibia

4. Femoral valgus

Discussion

The correct answer is (B). Secondary deformities are present in Blount disease that often interfere with gait and obtaining a true AP radiograph. These include distal tibial valgus (not varus as in A), procurvatum of the proximal tibia (not recurvatum as in C), femoral varus (not valgus as in D), and internal tibia torsion (the correct answer B). With internal tibial torsion, the knee will be externally rotated on an AP radiograph with the foot pointed forward. The patella must be faced forward to obtain a true AP. Adolescent Blount disease is unilateral and presents in children older than 10 years of age. It is less common than the infantile form.

The family returns, and the 10-year-old sister has a metaphyseal–diaphyseal angle of 17 degrees and 8 degrees of varus at the femur.

What is her treatment?

1. KAFO

2. Hemiepiphysiodesis of the lateral proximal tibia

3. Hemiepiphysiodesis of the lateral proximal tibia and lateral distal femur

4. Osteotomy of the proximal tibia

5. Osteotomy of the proximal tibia and distal femur

Discussion

The correct answer is (C). At this stage, KAFO treatment (A) is not indicated, as indications are for children <3 years old with Langenskiöld stage I to II changes. Hemiepiphysiodesis of the lateral proximal tibia (B) would only correct the tibia and not the femoral varus. Osteotomies (choices D and E) are reserved for younger children or with gradual correction and multiplanar frame for the complex form of adolescent Blount disease. This is performed to decrease neurovascular stretch injury. Hemiepiphysiodesis of the lateral proximal tibia and lateral distal femur (C) is the appropriate surgical treatment, but 25% of these children may require corrective osteotomies in the future.

Objectives: Did you learn...?

Treatment for infantile Blount disease?

Indications for surgical correction of Blount disease? Secondary deformity in Blount disease?

Differences in infantile and adolescent Blount disease?