CASE                               25                               

A 6-year-old boy with leg length difference presents to your clinic. He has a history of right distal femoral osteomyelitis at the age of 3. Full length radiographs demonstrate the left femur is 1.5 cm longer than the right.

What is the most predictable growth pattern disruption?

1. Postinfectious

2. Hemihypertrophy

3. Proximal femoral focal deficiency

4. Fibular hemimelia

5. Posttraumatic

The correct answer is (E). The most predictable growth disturbance is a post traumatic growth arrest at the physis (E). Postinfectious (A) and hemihypertrophy

(B) have unpredictable growth disturbance patterns. Proximal femoral focal deficiency (C) and fibular hemimelia (D) have deformities and deficiencies that can add to the leg length difference at maturity.

What is the appropriate treatment at this time?

1. Epiphysiodesis of the left distal femur

2. Hemiepiphysiodesis

3. Shortening osteotomy left femur

4. Lengthening right femur

5. Right shoe lift and observation

Discussion

The correct answer is (E). A 2- to 2.5-cm leg length discrepancy is treated with observation and a shoe lift. Epiphysiodesis (A) or shortening left femoral osteotomy (C) is reserved for predicted final discrepancies between 2 and 5 cm. Lengthening of the right femur (D) is reserved for predicted final discrepancies >5 cm. Hemiepiphysiodesis (B) is indicated with angular deformities of the leg.

What is the predicted leg length difference at maturity?

1. 6.5 cm

2. 7.8 cm

3. 8.8 cm

4. 9.0 cm

5. 10.5 cm

Discussion

The correct answer is (E). The physis of the lower extremity grow at these approximate rates per year: 3 mm for the proximal femoral physis, 9 mm for the distal femoral physis, 6 mm for the proximal tibial physis, and 5 mm for the distal tibial physis. The distal femoral physis consists of approximately 37% of the total limb growth. For a 6-year old with a distal femoral disruption, current 1.5-cm leg length difference, and estimated end of growth at the age of 16, he will have a 10.5-cm leg length difference ([10 years growth remaining × 9 mm/year] + 1.5 cm) at maturity. He should be followed closely because a large difference in leg lengths such as predicted here may require multiple procedures during growth to maintain a

<2-cm discrepancy.

The child returns at age 11 for follow-up. He has a predicted leg length discrepancy of 4.5 cm at maturity. His bone age is equal to his chronologic age as demonstrated by hand radiographs. What should his treatment consist of?

1. Epiphysiodesis of left femur

2. Lengthen right femur

3. Epiphysiodesis of left distal femur and lengthen right femur

4. Shorten left femur

5. Shoe lift and observe

Discussion

The correct answer is (A). For a 4.5-cm leg length discrepancy, epiphysiodesis of the long side (the left femur) is the recommended treatment. Lengthening of the

femur (B) is recommended for deformities >5 cm due to the complications associated with lengthening (pin tract infections, neurovascular stretch injuries) but these risks and alternatives should be discussed with the family. Dual procedures such as epiphysiodesis of the left distal femoral physis and lengthening of the right femur (C) are reserved for large deformities predicted >15 cm. Shortening of the left femur (D) greater than 4 cm leads to quadriceps weakness and difficulty with gait. Shoe lifts and observation are for discrepancies less than 2 to 2.5 cm. Hand radiographs using a Greulich and Pyle atlas is a method of confirming skeletal age for accurate timing of epiphysiodesis.

When should the epiphysiodesis be done?

1. Now

2. 11.5 years

3. 12 years

4. 12.5 years

5. 13 years

Discussion

The correct answer is (A). To obtain 4.5 cm of length from the contralateral femur at a rate of 9 mm per year, 5 years from the time of skeletal maturity must be used to correct the difference. Therefore, he should have the epiphysiodesis now in order to make up the 4.5-cm leg length inequality. The following differences can be accounted for by the other answers: 11.5 years (B) 4 cm, 12 years (C) 3.6 cm, 12.5 years (D) 3.1 cm, and 13 years (E) 2.7 cm. All options, however, will allow him to wear a shoe lift without anticipated complications.

Objectives: Did you learn...?

Common causes of leg length discrepancies in children? How to estimate final leg length discrepancies in children?

Treatment algorithm of treating leg length discrepancies in children?