FEMORAL TORSION – AN UNRECOGNIZED COMPONENT OF BLOUNT’S DISEASE

Abstract

Background: Blount’s original paper in 1937 described a case series of 28 patients with “Tibia Vara”. Since then various authors have attempted to describe in more detail the tibial and femoral deformities seen in this disease. It is still a poorly understood condition. This study describes the femoral rotational deformity that can occur in Blount’s disease.

Methods: Over a 2 year period, all patients with Blount’s disease seen in the Orthopaedic department of a regional hospital in South Africa were entered into a database. They underwent a review of their notes, a clinical rotational profile of their lower limbs and a CT scan of the femoral head/neck and distal femur. From this database we performed a cross sectional study. We then compared our results both to previously published controls for hip rotation and anteversion angles and with respect to the rotational profile, to a small cohort of 32 “normal” local children.

Results: A statistically significant increase in femoral anteversion in the affected legs was noted, with on average the femurs in Blount’s disease being 26 degrees more anteverted than previously published controls. A significant decrease in external rotation were also noted.

Conclusions: Our results suggest that the marked intoeing seen in many cases of Blount’s disease may be caused by internal femoral version, in addition to the well recognized internal tibial version. This study highlights the following issues:

1. A rotational profile should be part of the routine clinical assessment of all Blount’s cases.

2. A CT assessment of anteversion should be considered to quantify this accurately.

3. Overcorrection of the tibial internal version (to correct the added femoral version/torsion) should be considered when doing tibial osteotomies in cases with marked femoral internal version.

4. Some cases of Blount’s disease will require further correction of rotation, after corrective surgery around the knee, that included external rotation of the tibia. Persistent in-toeing may need a de-rotation osteotomy of the femur shaft.