Angular deformities of the limbs are one of the most frequent causes in pediatric orthopedic consultations. As in many other conditions in the infantile age (flat feet, rotational alterations, dysmetries, etc.) they are usually variants of normality and its transcendence resides in discovering when these parameters are out of normality.
During growth in healthy children there is a variation in the alignment of the limbs in the frontal plane that follows the following pattern:
- From birth to 2 years of age there is a varus configuration (bowlegs, where the knees are separated and the ankles touch each other).
- From the age of 2 years, the limbs begin to have the opposite disposition (valgus, legs in X, in which the knees touch and the ankles are separated) which decreases until around the age of 10 years in which the definitive physiological valgus of adults is acquired (+-7º).
These behavioral patterns are based on the description of the behavior of children of this age, and can be considered normal up to 2 standard deviations from the mean. Nor should the ages shown as a reference be taken as cut-off points that delimit the physiological from the pathological, but when an angular alteration is present, the important thing is to assess its magnitude and progression over time.
Genu varum
Genu varum should be considered physiological until 2-3 years of age. The persistence of this over the age of 3 years and especially the existence of asymmetry between the 2 legs should put us on the track to rule out pathological processes, as well:
- Blount’s disease: pathology that affects the growth plate of the proximal tibia and causes a progressive genu varum. Up to the age of 2 years it can be confused with the physiological genu varum of the infant, but from this age it is differentiated by the measurement of the Lévine metaphyseal-diaphyseal angle (angle 16º Blount disease).
- Metabolic diseases: the presence of a progressive varum forces us to rule out metabolic diseases such as rickets (although in our environment deficiency rickets are exceptional, those associated with alterations in the synthesis and function of Vitamin D, phosphates and renal function are more frequent), Mucopolysaccharidosis or Glycogenosis.
- Bone dysplasias: the great variability of these causes them to produce both genu varum and valgus. Thus, for example, varus is common in achondroplasia and valgus in multiple epiphyseal dysplasia.
Genu valgum
Ligamentous laxity and obesity are conducive to X-leg development. Asymmetric development or excessive symmetric valgus should rule out underlying pathology (especially proximal tibial fractures which often develop progressive valgus during healing, known as Cozen’s phenomenon, or in bone dysplasia).
Although knee valgus is a normal condition in the healthy adult, a valgus that exceeds normal limits may promote problems of gonarthrosis, patellar dislocation or patellar chondropathy in the future.
Treatment
In general, angular deformities do not usually require treatment, except for cases associated with pathological processes or those exceptional cases that may cause a problem during development or in adulthood.
Dennis-Brown or Atlanta splint orthotic devices have proven, despite their popularity in the past, to be ineffective in changing the natural evolution of angular deformities. Insoles or other similar devices, despite current advertising and fashion, also do not change the evolution of the process.
During growth, while the growth plate remains active, correction by blocking the unilateral growth plate (usually the medial femoral side in cases of valgus and lateral tibial in cases of varus) or hemiepiphyiodesis is an effective and surgically atraumatic solution.
At ages close to skeletal maturity it is sometimes not possible to perform this type of surgery and osteotomies are required, generally with the use of plates and screws, both tibial and femoral, depending on the existing deformity.
Rotational alterations of the limbs
Rotational alterations are, if possible, a more frequent consultation than frontal plane deviations. The rotation of the lower limbs is essentially conditioned by three segments:
- The femur: the femoral neck has at birth a forward deviation (femoral anteversion) of approximately 40º, which decreases with growth to the normal 20º in adults. The increased femoral anteversion conditions that, in order to produce a congruent articulation of the hip with the acetabulum, the entire lower limb rotates inward.
- The tibia at birth: it presents an approximately neutral tibial rotation, a rotation that changes to approximately 20-30º of external rotation.
- The foot: it is common that after birth, the foot presents (due to the intrauterine posture) a tendency for the toes to “look inwards” with respect to the ankle. This is usually a postural deformity that can be corrected spontaneously with exercise. More severe cases require orthotic treatment, with progressive casts or even surgery.
These 3 parameters have to be evaluated by means of the so-called Staheli Rotational Profile, in which the direction of gait with respect to a straight line is evaluated, as well as femoral anteversion, tibial rotation and forefoot adductus in a clinical manner.
When a child tucks the feet inward when walking, the objective is to assess which segment is the cause (femur, tibia or feet) and if the physiological evolution will allow the correction to occur spontaneously. It is exceptional that an angle of progression of the foot towards the internal part hinders ambulation or sports practice, and in cases where this is the case, it is indicated to wait for bone maturation to take place and at that moment to consider a defeating osteotomy of the affected segment.
Ambulation with the feet in external rotation is of greater importance, since the usual tendency is not towards improvement, but towards stabilization (even worsening) during development. An exaggerated external rotation can hinder ambulation, the practice of sports activities and increase the energy expenditure that both activities require. When these conditions are present, surgical correction (by means of tibial osteotomy, since an exaggerated external tibial rotation is usually required) must be evaluated.
Whenever a surgical correction is proposed, it must be assessed that there is no concomitant axial deformity (genu varum or valgus) and the exact rotation of the femur and tibia must be measured (for this purpose, a CT scan is mandatory), so that the rotation correction is also accurate.