This study was performed at Assiut University, Assiut, Egypt. Anterior distal femoral hemiepiphysiodesis (ADFH) using intra-articular plates for the correction of paediatric fixed knee flexion deformities (FKFD) has two main documented complications: postoperative knee pain and implant loosening. This study describes a biomechanical analysis and a preliminary report of a novel extra-articular technique for ADFH. Sixteen femoral sawbones were osteotomized at the level of the distal femoral physis and fixed by rail frames to allow linear distraction simulating longitudinal growth. Each sawbone was tested twice: first using the conventional technique with medial and lateral parapatellar eight plates (group A) and then with the plates inserted in the proposed novel location at the most anterior part of the medial and lateral surfaces of the femoral condyles with screws in the coronal plane (group B). Gradual distraction was performed, and the resulting angular correction was measured. Strain gauges were attached to the plates, and the amount of strain (and equivalent stress) over the plates was recorded. This technique was then applied to 9 paediatric FKFDs of different aetiologies. The preoperative FKFD and the amount of subsequent angular correction were measured. The amount of angular correction was higher in group B at 5, 10-, and 15-mm of distraction (p<0.001). The maximum and overall stresses measured throughout the distraction process were higher in group A (p<0.001). The mean FKFD improved from 24 ± 9° preoperatively to 9 ± 7° after 10 ± 3° months (p<0.001). The correction rate was 1.81 ± 0.65° per month. During ADFH, the fixation of the eight plates in the coronal plane at the anterior part of the femoral condyles may produce greater correction and lower stresses over the implants as compared to the conventional technique. Preliminary results from our initial series seem to support the effectiveness of this technique with respect to the degree of angular correction achieved

Purpose. The correction obtained in the coronal plane knee deformity using guided growth was assessed in children with sick physes (Height<1SD of the normal children) to define the limits of this technique in sick physis. Methods. We retrospectively assessed deformity correction following guided growth using 8 plates in children with coronal plane deformity and metabolically abnormal physis- renal rickets in 6 and bone dysplasias (multiple epiphyseal dyspasia, spondyloepiphyseal dysplasia, metaphyseal dysplasia, mesomelic dysplasia, chondrodysplasia punctata) in 10 children aged 2 to 14 years. Lateral distal femoral angle(LDFA) and medial proximal tibia(MPTA) angles were serially assessed after eight plate application as a day care procedure. We noted correction achieved rate of correction, complications and additional surgical procedures. Fischer's exact test and multiple regression analysis was done to assess the effect of modifiers. Results. Sixteen children mean aged 7.8 years (2–14 years) with 9 boys and seven girls were followed for a mean of 16.125 months. Deviations from normal MPTA(n=6) were a mean of 11.82(range 8.4–16.9) and from normal LDFA(n=15) a mean of 13.96 (range 5.7–35.1). Mean rate of correction was 0.8°(range 0.1–2.65) per month in dysplasia group and 1.09°(range 0.5–1.6)per month. Complete correction was achieved in 2 out of 6 in renal and 4 out of 10 in dysplasia group. Complication included backing out of screw (1), suboptimal screw placement (2) in dysplasia group and stiffness of the knee (1). Multiple regression analysis found sex, severity of deformity >15° and duration of follow up to be not significant, however, age less than 6 years had a significantly higher chance of deformity correction(P=0.001). Conclusion. The rate of deformity correction with eight plates for guided growth is very variable even within the same patient in dysplasia group, chondrodyspalsia and SED having very slow correction rates. The deformities however correct completely before the age of 6 years irrespective of etiology. Bone dysplasias and metabolic causes require further study to understand their growth pattern and possibilities of relapse