METHODS: Patients treated for Blount disease using external fixator from 2002 to 2016 were recruited for the study. We used Ilizarov and Taylor Spatial Frame (TSF) external fixator to perform simultaneous correction of all the metaphyseal deformities without elevating the tibia plateau. Surgical outcome was evaluated using mechanical axis deviation (MAD), tibial femoral angle (TFA), and femoral condyle tibial shaft angle (FCTSA).
RESULTS: A total of 22 patients with 32 tibias have been recruited for the study. The mean MAD improved from 95 ± 51.4 mm to 9.0 ± 37.7 mm (medial to midpoint of the knee), mean TFA improved from 31 ± 15° varus to 2 ± 14° valgus, and mean FCTSA improved from 53 ± 14° to 86 ± 14°. Mean duration of frame application is 9.4 months. Two patients developed pathological fractures over the distracted bones, one developed delayed consolidation and other developed overcorrection.
CONCLUSIONS: Correction of Blount disease can be achieved by gradual correction using Ilizarov or TSF external fixator with low risk of soft tissue complication. Longer duration of frame application should be considered to reduce the risk of pathological fracture or subsequent deformation of the corrected bone.
METHODS: Computed tomography (CT) scans of 100 normal adult knees, aged 18 years and above, were analysed using a 3-dimensional (3D) analysis software. All tibiae were first aligned to a standard frame of reference and then rotationally aligned to the tibial centroid axis (TCAx) and the transmalleolar axis (tmAx). MPTA was measured from best-fit planes on the surface of the proximal tibia for each rotational alignment. Diaphyseal bowing was assessed by dividing the shaft to three equal portions and establishing the angle between the proximal and distal segments.
RESULTS: The mean MPTA was 87.0° ± 2.2° (mean ± SD) when rotationally aligned to TCAx and 91.6° ± 2.7° when aligned to tmAx. The mean diaphyseal bowing was 0.1° ± 1.9° varus when rotationally aligned to TCAx and 0.3° ± 1.6° valgus when aligned to tmAx. The mean difference when the MPTA was measured with two different rotational alignments (TCAx and tmAx) was 4.6° ± 2.3°. No statistically significant differences were observed between males and females. Post hoc tests revealed statistically significant difference in MPTA between different ethnic sub-groups.
CONCLUSION: The morphology of the proximal tibiae in the disease-free Asian knee is inherently varus but not more so than other reported populations. The varus profile is contributed by the MPTA, with negligible diaphyseal bowing. These implications are relevant to surgical planning and prosthesis design.