Management of bow legs in children: A primary care protocol

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Original Research

Management of bow legs in children: A primary care protocol

J Fam Pract. 2017 May;66(5):E1-E6

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References

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Results

The mean walking age for those diagnosed with physiologic genu varum was 10 months (95% CI, 9.8-10.4), which is significantly younger than the 12 months of age (at the earliest) typical of toddlers in general (P<.001). There was no significant difference between the walking age of male and female children diagnosed with genu varum (P=.37).

Of the children presenting with the primary complaint of bow legs, 6% subsequently developed Blount’s disease. These patients presented at a mean age of 20.9 months and were diagnosed at a mean age of 23.9 months. Following the Blount’s disease diagnosis, we initiated therapy in all cases (3 surgical, 7 bracing).

Physiologic genu varum patients presented at a mean age of 16.4 months, with only 3.23% presenting at older than 23 months. On average, physiologic genu varum patients presenting before 24 months of age showed measurable varus correction 5 months after presentation and achieved varus resolution 7.3 months after presentation (TABLE 1). Assuming the patient population is normally distributed, we can be 95% confident that 95% of physiologic genu varum patients presenting before 18 months of age will show measurable varus correction by 24 months and will resolve without intervention by 30 months (TABLE 2). Patients presenting between 18 and 23 months of age should show measurable varus correction by 30 months and resolution by 36 months (TABLE 3).

Discussion

Primary care physicians have the ability to differentiate physiologic genu varum from pathologic forms of bow legs with a thorough history, physical exam, and radiographic examination, if necessary^1,2,13 (TABLE 4^{1,7,8,10,12,14,18-20,22,24,27}). Several approaches to differentiating Blount’s disease and physiologic genu varum have been described in the literature.^{1,4,7,8,10,14,22,23}

The average age at which children begin to walk independently is between 13 and 15 months.^5,18,29-31 Recently, it has been suggested that the range be expanded to include 12 months of age.³⁰ The association between early walking (at 10-11 months)^12,20,22 and Blount’s disease is generally accepted in the orthopedic literature.^{1,4,7,10,19-22} However, some authors have suggested early walking also contributes to genu varum.^{1,5,8,10,18,28} The mean age of independent walking for children with physiologic genu varum suggested in the literature (10 months) was confirmed in our study and found to be significantly younger than the average for toddlers generally.^1,22 Early walking is clearly associated with both physiologic genu varum and Blount’s disease, but no direct causation has been identified in either case. An alternative means of differentiating these entities is needed.

Primary care physicians can differentiate physiologic genu varum from pathologic forms of bow legs with a thorough history, physical exam, and radiographic examination (if needed).Radiographic examination of the knee is essential to the diagnosis of Blount’s disease as well as other, less common causes of pathologic bow legs (skeletal dysplasia, rickets, traumatic growth plate insults, infections, neoplasms).^1,8,14,19 The common radiologic classification of staging for Blount’s disease is the Langenskiöld staging system, which involves identification of characteristic radiographic changes at the tibial physis.^{5,8,14,15,18,22,24}

The fingerbreadth method, which requires no special equipment, accurately detected differences in varus angulation and tracked the normal pattern of lower limb angular development.Sequential measurement of genu varum is most useful in differentiating between physiologic and pathologic processes. Physiologic genu varum, an exaggeration of the normal developmental pattern, characteristically resolves and evolves into physiologic genu valgum by 3 years of age.^1,6-11 The pathophysiology of Blount’s disease is believed to be related to biomechanical overloading of the posteromedial proximal tibia during gait with the knee in a varus orientation. Excess loading on the proximal medial physis contributes to varus progression.^{4,10,14,20,25,27} Patients with Blount’s disease progress with varus and concomitant internal tibial torsion associated with growth plate irregularities and eventually exhibit premature closure.^{1,10,14,18,20,23,24,26} In the months prior to Blount’s disease diagnosis, increasing varus has been reported.^4,7,10,19 Varus progression that differs from the expected pattern indicates possible pathologic bow legs and should prompt radiologic evaluation and, often, an orthopedic referral.^{3,4,7-9,12,13,21}