Objective To reduce unnecessary orthopedic referrals by developing a protocol for managing physiologic bow legs in the primary care environment through the use of a noninvasive technique that simultaneously tracks normal varus progression and screens for potential pathologic bowing requiring an orthopedic referral.
Methods Retrospective study of 155 patients with physiologic genu varum and 10 with infantile Blount’s disease. We used fingerbreadth measurements to document progression or resolution of bow legs. Final diagnoses were made by one orthopedic surgeon using clinical and radiographic evidence. We divided genu varum patients into 3 groups: patients presenting with bow legs before 18 months of age (MOA), patients presenting between 18 and 23 MOA, and patients presenting at 24 MOA or older for analyses relevant to the development of the follow-up protocol.
Results Physiologic genu varum patients walked earlier than average infants (10 months vs 12-15 months; P<.001). Physiologic genu varum patients presenting before 18 MOA demonstrated initial signs of correction between 18 and 24 MOA and resolution by 30 MOA. Physiologic genu varum patients presenting between 18 and 23 MOA demonstrated initial signs of correction between 24 MOA and 30 MOA and resolution by 36 MOA.
Conclusion Primary care physicians can manage most children presenting with bow legs. Management focuses on following the progression or resolution of varus with regular follow-up. For patients presenting with bow legs, we recommend a follow-up protocol using mainly well-child checkups and a simple clinical assessment to monitor varus progression and screen for pathologic bowing.
Bow legs in young children can be a concern for parents.1,2 By far, the most common reason for bow legs is physiologic genu varum,3-5 a nonprogressive stage of normal development in young children that generally resolves spontaneously without treatment.1,6-11 Normally developing children undergo a varus phase between birth and 18 to 24 months of age (MOA), at which time there is usually a transition in alignment from varus to straight to valgus (knock knees), which will correct to straight or mild valgus throughout adolescence.1,6,7,9,10,12-17
The most common form of pathologic bow legs is Blount’s disease, also known as tibia vara, which must be differentiated from physiologic genu varum.8-10,15,18-24 The progressive varus deformity of Blount’s disease usually requires orthopedic intervention.1,10,23-26 Early diagnosis may spare patients complex interventions, improve prognosis, and limit complications that include gait abnormalities,4,8,10,27 knee joint instability,4,24,27 osteoarthritis,9,20,27 meniscal tears,27 and degenerative joint disease.19,20,27
Although variables such as walking age, race, weight, and gender have been suggested as risk factors for Blount’s disease, they have not been useful in differentiating between Blount’s pathology and physiologic genu varum.1,4,5,7,10,20,28 In the primary care setting, distinguishing physiologic from pathologic forms of bow legs is possible with a thorough history and physical exam and with radiographs, as warranted.1,2,15 More than 40% of genu varum/genu valgum cases referred for orthopedic consultation turn out to be the physiologic form,2 suggesting a need for guidelines in the primary care setting to help direct referral and follow-up. The purpose of this study was to provide recommendations to family physicians for evaluating and managing children with bow legs.
Materials and methods
This study, approved by the Internal Review Board of Akron Children’s Hospital, is a retrospective review of children seen by a single pediatric orthopedic surgeon (DSW) from 1970 to 2012. Four-hundred twenty-four children were received for evaluation of bow legs. Excluded from our final analysis were 220 subjects seen only once for this specific referral and 39 subjects diagnosed with a condition other than genu varum or Blount’s disease (ie, rickets, skeletal dysplasia, sequelae of trauma, or infection). Ten subjects with Blount’s disease and 155 subjects with physiologic genu varum were included in the final data analysis.
In addition to noting the age at which a patient walked independently, at each visit we documented age and the fingerbreadth (varus) distance between the medial femoral condyles with the child’s ankles held together. Parents reported age of independent walking for just 3 children with Blount’s disease and for 134 children with physiologic genu varum. Study variables for the genu varum data analysis were age of walking, age at presentation, age at varus correction, age at varus resolution, time between presentation and varus correction, and time between presentation and varus resolution. Varus correction is defined as any decrease in varus angulation since presentation. Varus resolution is defined as varus correction to less than or equal to half of the varus angulation at presentation. For inclusion in the age-at-resolution analysis, a child must have been evaluated at regular follow-up visits (all rechecks within 8 months).
To measure varus distance, we used the fingerbreadth method described by Weiner in a study of 600 cases (FIGURE).6 This simple technique, which requires no special equipment, accurately detected differences in varus angulation and tracked the normal pattern of lower limb angular development. The patient should be supine on the examination table with legs extended. With one hand, the examiner holds the child’s ankles together, ensuring the medial malleoli are in contact. With the other hand, the examiner measures the fingerbreadth distance between the medial femoral condyles. Alternatively, a ruler may be used to measure the distance. This latter method may be especially useful in practices where the patient is likely to see more than one provider for well child care.
We divided the genu varum subject group into 3 subgroups by age at presentation: 103 subjects were younger than 18 months; 47 were 18 to 23 months; and 5 were 24 months or older. We used the data analysis toolkit in Microsoft Excel 2013 to perform a statistical analysis of study variables. We assumed the genu varum population is a normally distributed population. We used a 95% confidence level (α=0.05) for all calculations of confidence intervals (CIs), student t-tests, and tolerance intervals. Based on the data analysis results, we developed a series of follow-up and referral guidelines for practitioners.