Among two hundred and twenty hemivertebrae in our files we performed over a period of eighteen years sixty nine hemivertebrae (HV) excision. Only H.V. with evidence of curve progression were operated on. The technique was a one stage anterior and posterior approach plus convex anterior and posterior arthrodesis plus convex posterior instrumentation using in the more recents cases a baby C.D.

Material: The location of the H.V. was thoraco-lumbar in twenty five cases, lumbar in twenty nine and lumbo-sacral in fifteen. Thirty two free, thirty six hemifused and only one fused H.V. were operated on. The sex ratio was 35 males and 34 females. Associarted malformations were numerous. If the rate of visceral associated malformations is rather the same whatever was the location of the H.V. ( 40% ) the number of associated spine malformations decrease from cranial to caudal ( 60% for thoraco-lumbar H.V. versus 13 % for lumbo-sacral H.V.) The mean age at surgery was 3Y 3M ( 1Y- 9Y) with a mean F.U. of 5Y ( 6M-18Y) for the 25 thoraco-lumbar H.V., respectively 3Y3M ( 1Y- 8Y3M) for the mean age at surgery and 5Y ( 1M-17Y5M) for the average F.U.for the 29 lumbar H.V. and 5Y1M (1M-10Y4M) for surgery and 7Y (1M-18Y3M) for F.U. for the remaining 15 lumbo-sacral H.V.

Results: 8 complications were encountered: 4 hardware failures, 1 sepsis, 1 transient paresthesia of the tibial nerve, 1 partial loss of power in the tibialis anterior and 1 valgus deformity following fibular bone grafting. For the 25 thoraco-lumbar H.V. the average scoliosis Cobb angle pre operatively was 38° ( 18°/ 75°) and at F.U. 24° ( 0°/ 76°) . The mean kyphosis Cobb angle was 24° ( -20°/ 54°) pre operatively and 25° (-16°/60°) at F.U. For the 29 lumbar H.V. the mean scoliosis Cobb angle was 35° (16°/58°) pre operatively and 10° (0°/38°) at F.U.The average kyphosis Cobb angle was -2°( -45°/20°) pre operatively and -6° (-42°/22°) at F.U. For the remaining 15 lumbo-sacral H.V. the average scoliosis Cobb angle was 30° (18°/40°) pre operatively and 13° (2°/32°) at F.U. The mean kyphosis Cobb angle was -22°(-54°/0°) pre operatively and -25°(-64°/-8°) at F.U. H.V. excision is in our opinion the best procedure to treat thoraco-lumbar,lumbar and lumbo-sacral H.V. as far as there is evidence of curve progression. The appropriate age to perform this kind of surgery is before three years of age.