Introduction and aim: It has been suggested that the sagittal spinal profile is partly hereditary. The relationship between the sagittal spinal profile and spinal biomechanics has also been established. In this study we test the hypothesis that the well-known familial trend in AIS may be explained by the inheritance of a sagittal spinal profile, that has been shown to make the spine less resistant to rotatory forces.

Materials and methods: Freestanding lateral radiographs of 51 parent couples of girls with severe progressive AIS (AIS group) and 102 age-matched controls (control group) were taken. Parents with manifest spinal deformities or spinal pathology were excluded, to avoid distorted sagittal images with unreliable measurements. Parameters of sagittal spinal profile and spinopelvic balance were semi-automatically calculated, and analyzed between the fathers of both groups, and between the mothers of both groups.

Results: In the fathers of the AIS group, the plumb line of T4 was significantly less posteriorly positioned relative to the hip axis, vertebrae T11-L2 were significantly less backwardly inclined, and a significantly flatter spine was found as compared to the fathers of the control group. No statistically significant difference was observed between the mothers of both groups.

Discussion and conclusion: The sagittal spinal profile of the fathers of scoliotic children was significantly flatter than the sagittal spinal profile of fathers of non-scoliotics. No difference was found in the sagittal spinal profile of the mothers of scoliotics as compared to mothers of nonscoliotics, possibly due to an inevitable normalization of the study population (exclusion of parents with spinal pathology) mainly in the mothers. Although, it is well known that scoliotic mothers have an increased risk of getting scoliotic offspring, this study indicates that fathers may contribute as well through their sagittal spinal profile to the inheritance of AIS.