This study reported guided growth for caput valgum deformity and subsequent hip development. Ten children with unilateral hip dysplasia had guided growth by one eccentric transphyseal screw at age 9.1 years with minimum 2 years of follow-up. The first change was decreasing articulotrochanteric distance and then increasing physis tilt angle and head-shaft angle by 1.5 years. The center edge angle that was significantly less than the normal side (18.3 vs. 24.8°) preoperatively became comparable between both the hips 2 years later. Rebounding of physis inclination after screw back out suggested mechanical tethering, rather than permanent physis closure, resulted in morphologic changes in the femur. Level of evidence: Therapeutic study, level IV.