During the last decade or more, the anchors used for instrumentation in scoliosis surgery are predominantly transpedicular screws, according to Suk. The long term radiographical feature of screw fixation after scoliosis surgery is not previously studied.

A consecutive series of 81 cases with AIS operated on with an all screw construct has been studied by means of low dose CT postoperatively and at 2 years postoperatively. There were 67 females and 14 males, with a mean age of 18.3 ± 3 years.

In 26 / 81 (32 %) there were signs of loosing of one or more screws, at a maximum 3 screws. We observed loosened screws in the upper thoracic region in 16 cases, in the thoracolumbar 6 and in lumbar area in 4. Mean pre-op Cobb angle was 56 in cases of loosening and 53 of intact screw fixation (n.s.), the correction rate was 69% in loosened vs 70% among intact screws (n.s.). In males there were signs of loosening in 8/14 (57%) and in females 18/67 (27%). Among cases with loosening, 14% had suboptimal screw positioning postoperatively, in intact cases it was observed in 11% (n.s.). In the whole group there were signs of suboptimal screw positioning 12%. Clinically, 1 case had a loosened L4 screw replaced; and at all 21/26 had no complaints and 5/26 reported minor pain or discomfort. 1/26 had a minor proximal junctional kyphosis about 10°, in 3/26 there was a pull-out of some few mms. With plain radiography loosening could be observed in 11/26 cases; 5 were in the lumbar region.

In a consecutive series of 81 adolescents with idiopathic scoliosis who had underwent scoliosis surgery according to Suk, one third showed, 2 years after the intervention, some minor screw loosening, assessed by low dose CT. One patient had one lumbar screw replaced and only 5 patients reported minor discomfort. Males were more prone to develop screw loosening.

Study design

Retrospective study.