الفهرس 
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Abstract
Adolescent idiopathic scoliosis (AIS) is the most common form of pediatric scoliosis. It occurs between the ages of 10 to 18.
Surgical treatment is indicated to halt curve progression (especially curves beyond 450) and improve cosmetic appearance. The main goal of surgery is to achieve correction of deformity including rotation, a fusion of the structural deformity of the spine, which will prevent further progression. This subsequently aims to improve spinal alignment and balance.
Bilateral placement of pedicle screws at every level has commonly been used, and this method provides maximal rigidity to the scoliosis construct; however, it is possible that fewer screws are adequate. Decreasing implant density has the advantage of decreasing operative time, risk of screw malposition, and cost. These advantages need to be weighed in relationship to the ability to obtain and maintain correction. Therefore, whether low density (LD) or high density (HD) screw constructs are better for AIS patients remains a subject of debate.
Implant density is defined as number of implants per spinal level fused. The ideal metal density in AIS is unknown but would be the lowest metal density to achieve satisfactory patient outcomes without increased complications. This may vary between cases, we could not identify a level of metal density below which deformity corrections decline.
In our prospective study 30 Patients diagnosed with adolescent idiopathic scoliosis (AIS) treated by low density implants (less than 1.6 screw/level). They were evaluated by Whole spine X-rays PA standing, lateral & AP with bending to the left &right.We measured Cobb s angles in AP standing film pre-operative and postoperatively at 1, 3, 6,12 months.
This study showed that the mean age of patients was 13.3 years, we achieved correction of mean preoperative curve 60.47° degree to 19.1°degree (68.49 %) by low density implants constructs (1.23). And mean loss of correction 1,97° degree (5.09%) after 12 months follow up.
Conclusion: Implant density was not significantly related to coronal or axial curve corrections. Mild positive correlations with anchor density were found. Low implant density with longer fusion level achieves excellent curve correction and stability. So spine surgeons should consider the influences of implant density on correcting deformities when planning the distributions of implants preoperatively. Operative time, blood loss, risk and cost are decreased with the use of low screw density implants.