Our findings concerning the influence of both sex and FHP on EOP size were anticipated. The strong association between males and robust cranial traits is acknowledged in the literature12,14,15,19, and may be attributed to increased craniocervical mass, muscle power and moment arm lengths19. The larger distribution of EEOP in the male population may also be explained by research suggesting that males are more likely to use handheld technology devices for time-consuming gaming and movie viewing, while females are more likely to engage in short duration social activities20,21, Furthermore, the synthesis of collagen in response to increased load on tissue was shown to be more moderate in females then males22. Not surprisingly, a more pronounced FHP, in both sexes, was correlated with an increase in age groups. Moreover, the mean FHP in our sample was recorded as 26 ±mm, a significantly larger value than the mean recorded in 1996 and prior to the “hand held technological revolution”23. Importantly, an increase in FHP increases mechanical load on the posterior craniocervical constituents24,25.

Repetitive and sustained mechanical load is required for robust adaptation to take place in tendon properties, as connective tissue adaptive response to load necessitates a slow process of matrix protein (collagen) production4,6,22. The development of EEOP may be attributed to, and explained by, the extensive use of screen-based activities by individuals of all ages, including children25,26,27, and the associated poor posture. Musculoskeletal disorders related to poor posture while using computers and tablets have been investigated extensively and were identified as a risk factor for the development of related symptoms at the neck, shoulders and forearms27,28,29,30. Furthermore, repetitive stress and aberrant posture were reported to be the most common biomechanical risk factors for work-related musculoskeletal disorders of the cervical spine31. Importantly, the use of tablet handheld devices was shown to trigger a higher activity level at the upper trapezius and cervical erector spinae26. Alarmingly, a survey of university staff and students revealed that participants spend an average of 4.65 hours/day using a hand held mobile device, and that 68% of the participating students reported neck pain32. These findings are expected as mechanical load on the cervical musculature was demonstrated to be 3–5 times greater when seated in flexed neck posture than in neutral spine position25. A recent systematic review reported that neck-related musculoskeletal conditions amongst mobile and hand-held device users are 17.3–67% more prevalent than any other region of the spine27. Obviously, postures that involve sustain forward head flexion or translation will provide similar mechanical stress to those experienced during mobile and hand-held device use. However, many activities involving these postures (e.g. bike riding using drop hand-bars, sleeping supine with a high pillow, etc.) have been prevalent for decades, and therefore cannot provide an explanation to the high prevalence of EEOP in our young adult population. Although the “tablet revolution” is fully and effectively entrenched in our daily activities, we must be reminded that these devices are only a decade old and it may be that related symptomatic disorders are only now emerging26,27.

While our findings concerning the influence of both sex and FHP on EOP size were expected, the interaction between age (defined by decade) and EOP size was unforeseen. Our findings contrast directly with reports highlighting the increase in prevalence of degenerative musculoskeletal features in general, and the magnitude of enthesophytes in particular, in aging populations1,8,17,33. Our results suggest that the younger age group in our study have experienced postural loads that are atypical throughout the other tested age groups. Similarly, the magnitude of the enthesophytes measured here highlights the substantial mechanical loads acting upon the EOP enthesis. To add perspective to our findings, the Achilles tendon enthesis is subjected to substantial loads due to its role in gait and weight bearing, however, Toumi et al.33 (n = 1080 males and females, age - 96-year-old) found an absence of large Achilles (dubbed the “premier entheses”) and plantar spurs in the under 40-year old male and female populations. Despite the Achilles tendon entheses being subjected to greater loading than the EOP entheses, it is intriguing that enthesophyte development at the latter appears to be more frequent, more prominent and occurring from early in age.

The greater prevalence of EEOP in our younger population may be explained by research indicating that entheseal development is more reliant on genetic factors during the early days and weeks after birth10. More importantly, subsequent development of the enthesis and entheseal transitional zones is determined by mechanical factors, such as repetitive trauma and excessive load acting at the insertion4,34. Conversely, enthesophyte formation and inflammation decrease markedly with mechanical load reduction2. The aforementioned suggests that excessive forces have been acting on the EOP of our young adult participants and these began during early childhood15. Considering our data and the literature on enthesophyte development we hypothesise that a key driver in the development of EEOP is the mechanical load acting on the enthesis due to poor posture and/or poor postural habits. Clearly, our findings should raise concern as morbidity and disability due to musculoskeletal disorders impose increasing physical, social and financial burdens on individuals and societies35,36,37,38,39. Accordingly, the mitigation of poor postural habit through prevention intervention may be prudent.

Clearly, the cross-sectional nature of this retroactive case study means that we are unable to draw direct causal links between EEOP formation and other issues such as poor posture and/or the use of mobile phones and other hand-held modern technologies. We acknowledge factors such as genetic predisposition and inflammation influence enthesophyte growth. Similarly, we acknowledge that most of our data were taken retrospectively from a clinician’s database of lateral cervical radiographs, with many individuals therefore originally seeking clinical advice and/or presenting with mild symptomology. Accordingly, despite our exclusion criteria, care should be taken to avoid over generalising these results to an asymptomatic general population. However, the high numbers of EEOP in the 18-30 age group suggests a potential avenue for prevention intervention through posture improvement education in this cohort.