Association Between Cumulative G-force Exposure and Cervical Spine Degenerative Changes

Tuomas Keskimölö; Petteri Oura; Tuomas Honkanen; Jaakko Niinimäki; Roope Sovelius; Tuomo Leino; Jaro Karppinen

doi:10.1093/milmed/usae452

Association Between Cumulative G-force Exposure and Cervical Spine Degenerative Changes

Mil Med. 2024 Sep 23:usae452. doi: 10.1093/milmed/usae452. Online ahead of print.

Authors

Tuomas Keskimölö^{1

2}, Petteri Oura³, Tuomas Honkanen^{4

5}, Jaakko Niinimäki^{3

6}, Roope Sovelius⁴, Tuomo Leino^{5

7}, Jaro Karppinen^{6

8}

Affiliations

¹ Faculty of Medicine, University of Oulu, Oulu 90220, Finland.
² Research and Development Section, Centre for Military Medicine, Finnish Defence Forces, Helsinki 00290, Finland.
³ Medical Research Center Oulu, Oulu University Hospital, Oulu 90220, Finland.
⁴ Aeromedical Centre, Centre for Military Medicine, Finnish Defence Forces, Helsinki 00301, Finland.
⁵ Department of Leadership and Military Pedagogy, National Defence University, Helsinki 00860, Finland.
⁶ Research Unit of Health Sciences and Technology, University of Oulu, Oulu 90220, Finland.
⁷ Air Force Command Finland, Finnish Air Force, Tikkakoski 41161, Finland.
⁸ Oulu Regional Office, Finnish Institute of Occupational Health, Oulu 90220, Finland.

PMID: 39312403
DOI: 10.1093/milmed/usae452

Abstract

Introduction: Fighter pilots work in a unique environment and are subject to high G-force loads under simultaneous head movements. Neck pain is reported to be a common health problem among fighter pilots leading to time lost flying and flight duty limitations. The present study aimed to find out if differences in early military flight career G-force exposure levels could increase the risk for degenerative changes in the cervical spine.

Materials and methods: The study population consisted of 56 20-year-old Finnish Air Force male fighter pilot cadets, who underwent MRI of the cervical spine at baseline and after 5 years. During follow-up, the G-force exposure was measured using the individual Fatigue Index (FI) recordings. The FI data were collected from each flight with BAE Hawks and is determined by the number of times certain levels of G-forces are exceeded during the flights. The incidence or progression of each degenerative change was compared to individual FI values using Pearson correlation coefficients.

Results: The pilots flew on average 220 (±21) hours with high performance aircraft during follow-up, resulting in an average FI of 1.98 (±0.47). A statistically significant progression was found in intervertebral disc (IVD) degeneration sum score with no correlation to corresponding FI values. A statistically significant increase was also found in the prevalence of IVD herniations with a negative correlation with FI values. Other degenerative cervical spine changes did not progress or did not correlate with corresponding FI values.

Conclusions: The prevalence of IVD degeneration and IVD herniations increases in the early phases of fighter pilots' career. Only the incidence of IVD herniations correlated with FI values and the correlation was negative. The negative correlation may be attributed to avoidance behavior due to neck pain, which was not measured in our study, or other unmeasured confounding factors. This was the first study to compare individual G-force exposure levels to high-quality MRI data over a follow-up of several years. Finnish fighter pilots are known to report increasing cervical symptoms during the Hawk training phase, but longer follow-up periods are likely needed to determine the association between G-force exposure levels and cervical degenerative changes.