Prominent exostosis in the occipital squama: an anatomical adaptation to biomechanical load

Enthesophytes are bony projections that arise from attachment sites of ligament, tendon or joint capsule to a bone. They are seen rarely in radiographic findings in young adults, as these bony adaptations are assumed to develop slowly over time. However, in my clinic I have frequently observed enlarged external occipital protuberance (EEOP) (up to 35.7 mm) in the radiographs of relatively young patients. Accordingly, the aim of the first part of this project was to assess the prevalence of an EEOP in a young adult population. That project involved a retrospective analysis of 218 lateral cervical radiographic studies of 18–30-year-old asymptomatic and mildly symptomatic participants. The external occipital protuberance (EOP) size was defined as the distance from the most superior point of the EOP (origin) to a point on the EOP that is most distal from the skull. To avoid ambiguity, the threshold for recording the size of an EOP was set at 5 mm, and an EOP was classified as enlarged if it exceeded 10 mm. Reliability testing was also undertaken. Results indicated that an EEOP was present in 41% of the total population, with 10% of all participants presenting with an EOP ≥ 20 mm. Furthermore, EEOP was significantly more common in males (67.4%) than in females (20.3%). The aim of the second study was to describe the distribution of EEOP in the different decades of life, and to assess the difference of EEOP distribution in terms of frequency and size between the different age groups in both genders. The second part of this project revealed that a combination of sex, the degree of forward head protraction (FHP) and age predicted the presence of EEOP (n = 1200, age 18–86). Results indicated that being a male and having increased FHP increased the likelihood of a participant presenting with EEOP, but paradoxically suggested that an increase in age (by decade) was linked to a decrease in enthesophyte prevalence and size. Our later findings provided a conundrum, as the frequency and severity of degenerative skeletal features in humans worsen typically with aging. The aim of third part of this project was to assess the involvement of genetic predisposition, inflammatory and/or mechanical influences in the development of large enthesophytes emanating from the EOP (14.5–30.5mm) in four teenage males. Importantly, the literature implies that large enthesophytes are exclusive to genetically predisposed individuals and to sufferers of spondyloarthropathies. This study included assessment of radiographs, MRI scans, blood-work, history, the SF-36 health survey, and the comparison of these data with historical controls from the relevant literature. During this analysis, known genetic markers (e.g. HLA-B27) were not detected by allele-specific primers, and both ESR and CRP tests were negative, with MRI analyses failing to detect active, localised inflammation at the EOP and surrounding structures. The health survey yielded normal parameters for all participants. Our data suggested that there is a link between mechanical load and the prevalence of EEOP, as all participants displayed large FHP values (> 40 mm), and interviews with participants and their parents indicated that in all cases posture-related concerns had existed since early childhood. The final part of this project evaluated whether the use of a simple home spinal traction device (Thoracic Pillow®) over a period of 12 weeks for a duration of 10 minutes per a day can bring positive changes to the sagittal cranio-cervical posture. Participants (n = 13, 18 – 36-year-old) were drawn from a previously studied mildly symptomatic population, all presenting with cranio-cervical malalignment and a considerable FHP. Sagittal cervical radiographs and SF36 health survey data were obtained pre- and post-intervention. Radiographic evaluation included standard measurements to assess changes in the sagittal cranio-cervical alignment and FHP (e.g. atlas plane line, vertical axis line, absolute rotation angle, relative rotation angle). The angle between the McGregor line and a horizontal line was utilised to measure the sagittal cranial posture. The SF36 health survey demonstrated positive changes throughout all tested domains. Importantly, all but the Change in Health and Role Limitation – Mental categories recorded large improvements (ES > 0.8). Participant log books indicated good participant compliance. Importantly, all participants, irrespective of the level of compliance, recorded postive changes in the SF36 Health Survey data. None of the participants indicated that they experienced any discomfort when using the Thoracic Pillow®. Furthermore, each of the key radiographic variables recorded significant moderate to large positive changes as a result of the intervention. Similarly, Chi-squared analyses indicated that post-intervention cervical sagittal spine configuration tended to become more lordotic (p = 0.007), with four of the participants shifting from a kyphotic to a lordotic presentation.Submitted in the fulfilment of the requirements of the degree of Doctor of Philosophy, University of the Sunshine Coast, 2019