A, Vertebral growth on horizontal plane, four segments: AL, Anterior left; AR, anterior right; PL, posterior left; and PR, posterior right. B, Congenital posterior bar involving PL and PR; level of epiphysiodesis must be AL and AR. C, Anterior defect involving AL and AR; epiphysiodesis must involve PL and PR. D, Anterior excess of growth potential involving both AR and AL; epiphysiodesis must involve both AR and AL above and below. E, Congenital posterolateral bar involving PL only; epiphysiodesis must involve only AR. F, Excess (hemivertebra) growth involving only AR and part of PR; hemiepiphysiodesis must involve AR and PR.