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Background: A new-concept of non-osteotomy implant is advantageous in not only performing a surgery by applying the tensile force to the growth plate without osteotomy but also achieving a prompt recovery; it is expected to be effective in correcting the leg length discrepancy and angular deformity. Objectives: This animal experiment was performed to assess the effectiveness of a new-concept of non-osteotomy implant in correcting the leg length discrepancy and angular deformity by promoting the growth without suppressing it. Methods: To compare differences in changes in anthropometric measurements between preoperatively and postoperatively, the right and left sides of the femur served as the experimental group and the control group, respectively. In the right femur, two screws each were placed in the upper and lower part of the growth plate. For bilateral distraction, a spring was applied to both sides of the femur (experimental animals 9 and 10). For unilateral distraction, a spring was applied to the external side of the femur only (experimental animals 5, 7, 8 and 11). A CT was performed at a 4-week interval and CT scans were reconstructed 3-dimensionally the MimicsÒ Innovation Suite (Mimics and 3-matic; Materialize, Leuven, Belgium). The anatomical axis of the femur (AAF) is considered as a line that passes through the long axis of the femur through the medullary canal. The mechanical axis of the femur (MAF) is the line drawn through the centers of the femoral head and the intercondylar fossa. This was followed by measurement of time-dependent changes in the line and angle formed by the AAF and the MAF. In more detail, a 3-D registration was performed for CT scans of the femur at each time point, for which the lower part of the growth plate was matched and both the AAF and the MAF were used to form the plane. This was followed by 3-D orthogonal projection of both the AAF and the MAF on the plane postoperatively. Results: With bilateral distraction at a tensile force of 50 N and 100 N, the degree of changes in the length of the AAF at 1 month from baseline was higher on the right side as compared with the left side. This was also seen in the length of the MAF. Moreover, with unilateral distraction at a tensile force of 25 N and 50 N, the degree of changes in the angle formed by the AAF at 1, 2, 3, 4, 5 and 6 months from baseline was significantly higher on the right side as compared with the left side (P<0.05). This was also seen in the angle formed by the MAF. Conclusions: The current results confirm the biomechanical effectiveness of a new-concept of non-osteotomy implant in promoting the bone growth. But this deserves further prospective randomized controlled trials.