Redefining global spinal balance: normative values of cranial center of mass from a prospective cohort of asymptomatic individuals.

STUDY DESIGN

Prospective radiographical analysis of cranial center of mass (CCOM), C2, and C7 plumb lines in young and elderly asymptomatic individuals.

OBJECTIVE

To establish a normal range for craniosagittal balance for both young and elderly asymptomatic individuals.

SUMMARY OF BACKGROUND DATA

Global sagittal balance must account for the position of the head in relation to the spine and pelvis. The C7 plumb line defines thoracolumbar sagittal balance and has been shown to have significant impact on patient outcomes. However, the C7 plumb line fails to take into consideration the position of the head in relation to the pelvis.

METHODS

A total of 100 asymptomatic 20- to 40-year-old patients and 100 asymptomatic 60- to 80-year-old patients were enrolled. Standing plain radiographs of 14 × 36 in were obtained. CCOM, C2, and C7 plumb lines were drawn and measured from the superoposterior endplate of S1.

RESULTS

A total of 78 asymptomatic 20- to 40-year-old patients and 62 asymptomatic 60- to 80-year-old patients had adequate radiographs. The mean plumb line values in the 20- to 40-year-old patients and 60- to 80-year-old patients, respectively, were as follows; CCOM 9.0 mm (SD, 31.5 mm) and 41.2 mm (SD, 35.7 mm); C2 -2.7 mm (SD, 32.7 mm) and 32.1 mm (SD, 33.6 mm); and C7 -16.4 mm (SD, 31.5 mm) and 10.6 mm (SD, 27.8 mm). One-way analysis of variance and Student t tests confirmed that these mean plumb line values were significantly different between young and elderly patients (P < 0.001). The change at each level over time was highly correlated with the other levels (r > 0.97; P < 0.001) as did the degree of change between groups (r > 0.90, P < 0.001).

CONCLUSION

Spinopelvic alignment in conjunction with CCOM has increased our understanding of spinal balance by including the head and may better represent true global spinal balance. CCOM is an easily measured parameter by using the nasion-inion technique.