[Correction of angular deformity of the knee in growing children by temporary hemiepiphyseodesis using the eight-plate].

AIM: Angular deformities of the lower extremity are considered as prearthrotic factors. Osteotomy is regarded as a way of corrective treatment. But this intervention is considered as complex and requires a special after-treatment. During childhood and with remaining growth, guided growth offers an elegant solution for this problem. Resulting in a temporary hemiepiphyseodesis, the eight-Plate offers an alternative technique besides the Blount staples and the definitive epiphyseodesis. We evaluated the effect of this device on the correction of angular deformities in children with different diagnoses and at different ages.

METHOD: Since 04/2006 22 patients with angular deformities of the lower extremities due to different diagnoses were treated at our department with the eight-Plate (42 eight-Plates). In this study we evaluated the outcome of 13 patients (26 eight-Plates) until the completed angular correction and removal of the eight-Plate. A special treatment after plate removal was not applied.

RESULTS: All patients improved their mechanical leg axis. The average age at implantation was 9.4 years (2.3-13.7 years). The average time until plate removal was 10.7 months (6-34 months). No hardware failures, extrusions, growth arrests, wound infections or other complications were observed. Two patients did not achieve the desired axis correction because of insufficient remaining growth potential. An additional surgical intervention was realised. The average correction of the study group regarding the mechanical axis deviation (MAD) was 22 mm (6-43 mm) and 10.6 degrees (5-27 degrees) regarding the angular correction of the mechanical lateral distal femoral angle (mLDFW). The mechanical medial proximal tibial angle (mMPTW) changed by 8.0 degrees (3-15 degrees).

CONCLUSION: In our opinion the eight-Plate seems to be a safe and reliable device for guided growth of angular deformities around the knee. The technique is easy to learn and the complication rate low compared to the staple technique. A special after-treatment is not needed and there is only minor operative trauma. At present there are only few data on long-term follow-up after plate removal until skeletal maturity. The definition of the ideal point in time for plate removal is still open.