Dynamics of atlantoaxial rotation related to age and sex: a cross-sectional study of 308 subjects

Abstract

Background context: Physiological ranges and dynamic changes of atlantoaxial rotation (ROT_C1/2), total cervical spine rotation (ROT_Cs) and the percentage of ROT_C1/2 from ROT_Cs (ROT_Cperc) for different age groups have not yet been investigated in a sufficiently sized cohort. Furthermore, it is not clear whether demographic variables such a sex, smoking status or diabetes affect ROT_C1/2, ROT_Cs and ROT_Cperc.

Purpose: Obtain physiological ranges of ROT_C1/2, ROT_Cs and ROT_Cperc for different age groups and determine their age-based dynamics. Investigate whether ROT_C1/2, ROT_Cs and ROT_Cperc are affected by sex, smoking status or diabetes.

Design: Observational cross-sectional study.

Patient sample: Patients undergoing elective CT examinations of the head and neck region between August 2020 and January 2022.

Outcome measures: Ranges of motion of ROT_C1/2, ROT_Cs and ROT_Cperc in degrees.

Methods: A total of 308 subjects underwent dynamic rotational CT examinations of the upper cervical spine. Patients were divided into three age categories A1 (27-49 years), A2 (50-69 years) and A3 (≥70 years). Category A3 was further divided into B1 (70-79 years) and B2 (≥80 years). Values of ROT_C1/2, ROT_Cs and ROT_Cperc were compared between all age groups, males and females, smokers and nonsmokers, diabetics a nondiabetics. Dynamics of ROT_C1/2, ROT_Cs related to age and sex were visualized using scatterplot and trendline models.

Results: ROT_C1/2 significantly decreased from group A1 (64.4°) to B2 (46.7°) as did ROT_Cs from A1 (131.2°) to B2 (97.6°). No significant differences of ROT_perc were found between groups A1-B2 with values oscillating between 49% and 51%. Smoking and diabetes did not significantly affect ROT_C1/2, ROT_Cs and ROT_Cperc, females had significantly higher ROT_Cs than males. Males and females demonstrated a different dynamic of ROT_C1/2 and ROT_Cs demonstrated by out scatterplot and trendline models.

Conclusions: Both ROT_C1/2 and ROT_Cs significantly decrease with age, whereas ROT_Cperc remains stable. Females demonstrated higher ROT_Cs and their decrease of ROT_C1/2 and ROT_Cs occurred in higher age groups compared to males. The functional repercussions atlantoaxial fusion are variable based on patient age and sex and should be taken into account prior to surgery.

Keywords: Age; Atlantoaxial fusion; Biomechanics; Functional exam; Joint; Range of motion; Rotation; Sex.