Presentation
History and Physical Examination
It is most helpful to ask the child with genu varum to stand with feet together and with equal weight on both legs. The intercondylar distance is easy to measure and demonstrate to the concerned parents. Observe the gait noting the foot progression angle and the presence or absence of a lateral thrust. In the prone position, measure the inward-outward hip rotation (femoral torsion) and the thigh-foot axis (tibial torsion).
In addition, examine the entire spine and record the stature of the child. Document the range of hip motion, including abduction in flexion and extension. Children with dysplasias or metabolic disorders may have coxa vara, limited hip abduction, and a positive Trendelenburg gait. They may also have ankle varus with medial thigh and calf creases.
Media Gallery
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Mechanical axis is measured on full-length weightbearing radiograph by drawing line from center of femoral head to center of ankle. Normally, it should bisect knee, with joint horizontal and parallel to ground. Genu varum is defined by medial displacement of mechanical axis. Shown here is tibia vara and slight lateral ligamentous laxity contributing to deformity.
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Three factors contributing to genu varum: femur varum, ligamentous laxity, and tibia vara. Mechanical axis is further deviated medially.
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If knee is divided into quadrants and variations of normal allowed for, mechanical axis should be neutral or at least fall within medial or lateral zone 1. Deviation into zone 2 is relative indication for surgical intervention, and zone 3 is obvious call for action. If physes are open, correction may be gained by guided growth; after skeletal maturity, only choice is corrective osteotomy.
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Anatomic angles are measured between joint surface of each bone and its respective shaft. Lateral distal femoral angle (LDFA) is normally 84°, and proximal medial tibial angle (MPTA) is 87°. On close-up view, one can measure joint convergence angle (normally 0°); this is defined by articular surface lines of femur and tibia. Lateral ligamentous laxity can contribute to varus malalignment.
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Tibia vara (Blount disease) is growth disturbance of proximal medial tibia that can present any time from infancy to adolescence. Natural history is one of inexorable progression, premature closure of upper medial tibial physis, lateral thrust, ligamentous laxity, and, ultimately, joint instability and degeneration. At age 5, guided growth would have been sufficient. After physeal closure, complex osteotomies are required.
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Hypophosphatemic rickets is disturbance in vitamin D metabolism that weakens physes through delayed ossification. Consequent deformities may progress despite careful medical management and bracing. Deformities are typically bilateral, involving both femur and tibia.
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Child wore her braces religiously, only to experience steady progression of deformities.
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At 2 years after guided growth of distal lateral femora and proximal lateral tibiae (and without further bracing), patient's legs are straight. She will be monitored as she continues to grow.
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This 7-year-old boy with Ollier disease presented with complex deformity including varus and outward torsional deformity of right tibia and progressive limb length discrepancy. Whereas guided growth could improve varus, it could not address other two issues. Therefore, he underwent osteotomy and callotasis with Taylor Spatial Frame.
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External fixator in place.
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This 4-year-old girl with Job syndrome, which includes immunoglobulin deficiency, had osteopenia and developed pathologic fracture of proximal tibia. She then drifted into progressive genu varum. It was felt that guided growth might not work in mechanically compromised environment.
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Patient underwent corrective osteotomy of upper tibia and fibula, supplemented with cast.
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Follow-up at age 10.
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Follow-up at age 12.
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At age 5, this boy presented with asymmetrical tibia vara (Blount disease). Treating surgeon employed guided growth on right and osteotomy of tibia/fibula on left.
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At 14-month follow-up, mechanical axis is neutral on right, and plate was removed. Mechanical axis was in medial zone 2; this was addressed by insertion of lateral eight-Plate.
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After additional 8 months of guided growth, leg straightened out, and plate was removed. Patient's limb lengths remain equal, and there has been no recurrence of angular deformity. Annual monitoring will continue until maturity: if there is any drift of mechanical axis, guided growth will be repeated.
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At 1 year after proximal tibial stapling to correct limb length inequality, this scanogram shows loosening of lateral staples with consequent iatrogenic varus of tibia. Physes are still open.
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Full-length view shows mechanical axis deviation into medial zone 2; this was not demonstrable on scanogram. Staples were removed and lateral ones replaced with eight-Plate.
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At 1 year after guided growth with eight-Plate, mechanical axis has been restored to neutral. At that time, eight-Plates were employed to accomplish pan-genu epiphysiodesis to correct patient's residual limb length inequality.
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This 20-month-old boy presented with waddling gait and hip pain. His father has same condition and had osteotomies of his tibias, femora, and hips during childhood. He anticipated similar treatment for his son.
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Standing anteroposterior (AP) radiograph demonstrates varus deformities at hips, knees, and ankles, with mechanical axis in medial zone 3 bilaterally. Traditional treatment would have included staged osteotomies of proximal and distal femora and of proximal and distal tibiae and fibulae, requiring x number of casts and hospitalizations.
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Presenting AIR (abduction, inward rotation) view of pelvis shows "triangular defect," which is essentially stress fracture, of each femoral neck. This would explain his hip pain and Trendelenburg gait.
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Sequential radiographs demonstrate neutralization of mechanical axis during 13 months following guided growth. This was performed as outpatient procedure, requiring no immobilization.
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Upon removal of pan-genu eight-Plates (2/07), additional plates were applied to greater trochanter in hope of gradually increasing neck-shaft angle and obviating need for proximal femoral osteotomies.
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Clinical photographs taken at age 20 months and at age 2 years 9 months.
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Whereas complication rate of guided growth with eight-Plates remains low, there have been isolated cases of broken screws. Each broken screw has been distal (metaphyseal) screw in heavy-set patient with Blount disease. Potential solutions are to insert solid 4.5-mm screw or to add second eight-Plate.
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