Standing sagittal alignment of the whole axial skeleton with reference to the gravity line in humans

Abstract

Human beings stand upright with the chain of balance beginning at the feet, progressing to the lower limbs (ankles, knees, hip joints, pelvis), each of the spinal segments, and then ending at the cranium to achieve horizontal gaze and balance using minimum muscle activity. The details of the alignment and balance of the chain, however, are not clearly understood, due to the lack of information regarding the three‐dimensional (3D) orientation of all bony elements in relation to the gravity line (GL). We performed a clinical study to clarify the standing sagittal alignment of whole axial skeletons in reference to the GL using the EOS slot‐scanning 3D X‐ray imaging system with simultaneous force plate measurement in a healthy human population. The GL was defined as a vertical line drawn through the centre of vertical pressure measured by the force plate. The present study yielded a complete set of physiological alignment measurements of the standing axial skeleton from the database of 136 healthy subjects (a mean age of 39.7 years, 20–69 years; men: 40, women: 96). The mean offset of centre of the acoustic meati from the GL was 0.0 cm. The offset of the cervical and thoracic vertebrae was posterior to the GL with the apex of thoracic kyphosis at T7, 5.0 cm posterior to the GL. The sagittal alignment changed to lordosis at the level of L2. The apex of the lumbar lordosis was L4, 0.6 cm anterior to the GL, and the centre of the base of the sacrum (CBS) was just posterior to the GL. The hip axis (HA) was 1.4 cm anterior to the GL. The knee joint was 2.4 cm posterior and the ankle joint was 4.8 cm posterior to the GL. L4‐, L5‐ and the CBS‐offset in subjects in the age decades of 40s, 50s and 60s were significantly posterior to those of subjects in their 20s. The L5‐ and CBS‐offset in subjects in their 50s and 60s were also significantly posterior to those in subjects in their 30s. HA was never posterior to the GL. In the global alignment, there was a positive correlation between offset of C7 vertebra from the sagittal vertical axis (a vertical line drawn through the posterior superior corner of the sacrum in the sagittal plane) and age, but no correlation was detected between the centre of the acoustic meati‐GL offset and age. Cervical lordosis (CL), pelvic tilt (PT), pelvic incidence, hip extension, knee flexion and ankle dorsiflexion increased significantly with age. Our results revealed that aging induces trunk stooping, but the global alignment is compensated for by an increase in the CL, PT and knee flexion, with the main function of CL and PT to maintain a horizontal gaze in a healthy population.

The Large Individual Differences in the Range of Hip Joint Motion Rather Than Lumbar Spine Motion Affect Dynamic Spinopelvic Rhythm

“…We believe that the allowable range of proper spinal alignment varies depending on individual spinopelvic rhythm. In recent years, the total sagittal alignment from the cervical vertebra to the ankle has gradually become an important topic, and three-dimensional alignment analysis is also progressing 37) . Hence, it is necessary to study the relationship between spinal sagittal alignment and quality of life with consideration for dynamic factors.…”

Identification of optimized rod shapes to guide anatomical spinal reconstruction for adolescent thoracic idiopathic scoliosis

“…After all‐level facetectomy within the instrumentation level, with the exception of the lowest intervertebral segment to avoid pseudoarthrosis at this site, two titanium alloy rods with identical measurements were bent to guide the postoperative anatomical thoracic kyphosis, without reference to the intraoperative coronal alignment of the AIS deformity. For the postoperative anatomical thoracic kyphosis, the apex was anticipated to be located at T6–T8 because the anatomical apex of the thoracic kyphosis is located at these levels . The rod shapes were split into two shapes.…”

3D geometric morphometric analysis of variation in the human lumbar spine

“…Nevertheless, there is a number of studies investigating different adult populations and applying different methodologies, which did not find sexual dimorphism neither in lordosis (Hasegawa et al, ; Jentzsch et al, ; Kalichman, Li, Hunter, & Been, ) nor in the wedging of the vertebral segments (Fazzalari, Manthey, & Parkinson, ). Legaye, Duval‐Beaupère, Hecquet, and Marty () even found a greater mean lordotic angle in males than in females.…”