Abstract:[Objective] To compare the clinical results of closed reduction and fixation in human position with above-knee hip spica cast versus standard hip spica cast for developmental dysplasia of the hip in infants. [Methods] A retrospective study was performed on 6~18 month-age 121 children who received closed reduction and external fixation in human position with hip spica cast in our department from January 2010 to December 2018. According to the results of communication with the parents of the infant, 58 infant (76 hips) were fixed with above-knee cast (AK group), while the other 63 cases (80 hips) had standard hip spica cast used (SD group). The clinical and imaging data of the two groups were compared. [Results] The early redislocation rate was 11.8% (9/76) in the AK group, whereas 2.5% (2/80) in the SD group, which proved statistically significant between them (P<0.05). All children with redislocation were changed to open reduction, and were excluded from further evaluation of this study. There were no significant differences in fluoroscopy times, time in plaster, and incidence of pressure sores between the two groups (P>0.05). All the children were followed up for (5.3±2.0) years on an average, and there was no sig- nificant difference in the time to start standing and to walking after the plaster removed between the two groups (P<0.05). Radiographically children in both groups got significant improvement in T?nnis grades at the latest follow-up compared with those pre-treatment (P<0.05). In addition, the Severin grade and center-edge angle (CE) in both groups remained unchanged at the latst follow-up compared with those just after cast removal (P>0.05), whereas acetabular index (AI) increased significantly over time in both groups (P<0.05). At any corresponding time points, there were no significant differences in T?nnis grade, Severin grade, CE and AI between the two groups (P<0.05). At the latest follow-up, the femoral head necrosis rate was 14.9% (10/67) in the AK group, while 16.7% (13/78) in the SD group, which was not statistical-ly significant (P>0.05). [Conclusion] Closed reduction and fixation with hip spica cast is an effective treatment for DDH in 6~18 monthage infant, the above-knee hip spica cast has higher risk of early redislocation than the standard hip spica cast. Key words: developmental dysplasia of the hip, closed reduction plaster fixation, human position, above-k