Orthotic Treatment of Infantile Tibial Vara

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Medscape Orthopedics. 1999;3(6) 

Orthotic Treatment of Infantile Tibial Vara

Infantile tibia vara is a developmental condition producing progressive varus deformity of the knee in young children. Early diagnosis is critical, since toddlers can have infantile tibia vara at an early stage instead of physiologic genu varum. Although uncommon compared with normal physiologic bowing, progressive deformities can result if it is not diagnosed early.

Physiologic genu varum exists in children up to 2 years of age. It is very important for physicians to differentiate between persistent physiologic varus and early infantile tibia vara, especially prior to 24 to 36 months of age. The role of bracing in treating this condition is unclear.

In 1982, Levine and Drennan[1] described the use of the metaphyseal-diaphyseal (MD) angle to distinguish between Blount's disease and physiologic varus. The metaphyseal-diaphyseal angle is the angle created by the intersection of a line through the transverse plane of the proximal tibial metaphysis with a line perpendicular to the long axis of the tibial diaphysis. This angle represents the degree of deformity of the proximal end of the tibia in a patient with clinical bow-leg deformity and permits early differentiation between infantile tibia vara and physiologic bow-leg, before the appearance of the radiographic changes of tibia vara. Levine and Drennan found that in 29 of 30 affected extremities with an initial metaphyseal-diaphyseal angle of more than 11.0 degrees, radiographic changes of tibia vara later developed. They concluded that an angle of more than 11.0 degrees is indicative of risk for progression.

In 1993, Feldman and Schoenecker[2] evaluated the accuracy of the metaphyseal-diaphyseal (MD) angle of the proximal aspect of the tibia for differentiating physiologic bowing from Blount disease. They compared this angle in 106 children (179 extremities) who had physiologic bowing with that in 19 children (32 extremities) who had Blount disease. The angle averaged 9 +/- 3.9 degrees for the patients who had physiologic bowing and 19 +/- 5.7 degrees for the patients who had Blount disease (P < 0.0000001). The authors noted that for Drennan angles > 16 degrees or < 9 degrees, the confidence interval of this diagnosis increases to 95%.

Yaghoubaian and colleagues performed a retrospective study to determine the efficacy of bracing in 2 groups of patients: (1) patients with an MD angle between 9 degrees and 16 degrees with a clinical risk factor for progression, and (2) those with an MD angle > 16 degrees. In addition, the authors attempted to identify risk factors associated with progression.

Indications for surgery include unresolved deformity at age 4 years and progression to a Langenskiold stage III.

Yaghoubaian and colleagues identified 110 lower extremities in 59 patients. The 38 patients (60 lower extremities) included in the study had tibia vara without traumatic, congenital, metabolic, or infectious etiologies. Those with a Drennan angle of < 9 degrees or an angle between 9 and 16 degrees with no clinical risk factors for progression were excluded. Risk factors including ligamentous instability, weight > 90th percentile, gender, and ethnic background were analyzed.

The MD angle, mechanical axis, and anatomic axis were measured at the initiation of bracing, at the discontinuation of bracing, and at the final follow-up. The orthosis prescribed was a KAFO producing a valgus force by a 3-point pressure system.

Of 60 lower extremities, 7 had an MD angle of > 16 degrees. Fifty-three lower extremities had an MD angle between 9 degrees and 16 degrees and a clinical risk factor for progression. The success rate of bracing was 90% (54/60). Patients with an MD angle > 16 had a success rate of 86% (6/7). Patients with an MD angle > 9 degrees and < 16 degrees had a success rate of 91% (48/53).

Of the 60 lower extremities studied, 54 had resolution with bracing, while 6 needed surgical intervention. The 2 groups were compared with regard to risk factors, the age at the initiation of bracing, the Drennan angle, and the mechanical and anatomic angles.

Weight > 90th percentile was a significant risk factor. Fifty-nine percent (32/54) of patients in the braced group were in > 90th percentile for weight. All (6/6) patients in the surgical group were in the 90th percentile for weight.

Ligamentous instability was also found to be a significant risk factor. Thirty-four percent (11/32) of patients in the braced group had ligamentous instability, while over 66% (4/6) of the surgical group had this condition.

The age at initiation of bracing was found to be significant. Patients in the braced group had an average age of 2.2 years at initiation, while that for individuals in the surgical group was 3 years.

Gender, ethnicity, and length of bracing were not found to be significant. In addition, the MD angle difference, the mechanical axis difference, and the anatomic axis difference were not found to be significant.

Bracing is recommended in patients younger than 3 years of age with MD angles > 16 degrees. Patients with MD angles between 9 degrees and 16 degrees with presence of ligamentous laxity or obesity are also recommended for bracing.

Made possible through an unrestricted educational grant from Smith & Nephew.

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