Ossification of the Ligamentum Flavum in a Nineteenth-Century Skeletal Population Sample from Ireland: Using Bioarchaeology to Reveal a Neglected Spine Pathology

Jonny Geber,Niels Hammer

doi:10.1038/s41598-018-27522-x

Abstract

Ossification of the ligamentum flavum of the spine (OLF) is rarely reported in individuals of European ancestry. It has, however, been observed in archaeological skeletons from Europe. The aim of this study was to revisit OLF rates, utilising a mid-nineteenth-century skeletal sample from Ireland. The hypothesis was that the OLF prevalence rate was similar to studies on non-Europeans. Spines from 345 individuals were analysed, and the extent of OLF recorded on the cranial and caudal attachment sites of each vertebra using the following classification system: Grade 0 (no change); Grade 1 (<2 mm); Grade 2 (2–4 mm); Grade 3 (≥4 mm). OLF was observed at prevalence rates of 83.6%. There was no disparity in prevalence based on sex, except for individuals aged 36–45 years at death in which the male rate was higher. Advancing age was a determining factor in the OLF occurrence with an onset in young adulthood (18–25 years), and most severe grades occurring over the age of 25 years. OLF coincides with spinal osteoarthritis, spondylosis deformans and Schmorl’s nodes in both sexes, and with intervertebral osteochondrosis in females. The results of this study indicate that OLF is likely to be an understudied rather than rare condition in European populations.

Highlights

Ossification of the ligamentum flavum of the spine (OLF) is rarely reported in individuals of European ancestry
Based on the published clinical literature, OLF appears to be exceptionally rare in populations with predominately European ancestry
One may speculate that OLF is a neglected condition in individuals of European ancestry, e.g. due to a more predominant focus on clinical and radiological pathologies such as hip and knee arthritis and peripheral vascular disease

Summary

Introduction

Ossification of the ligamentum flavum of the spine (OLF) is rarely reported in individuals of European ancestry. It has, been observed in archaeological skeletons from Europe. Cervical and lumbar manifestations have been described[33,34], and single-level ossification is reported more often than multi-level manifestation[6] Both intrinsic and extrinsic factors have been postulated as the cause of OLF. Based on the published clinical literature, OLF appears to be exceptionally rare in populations with predominately European ancestry. This article is reporting on OLF in archaeological skeletal remains (Fig. 1) from a mid-nineteenth-century (AD 1847–1851) population sample from Kilkenny City, Ireland, and the prevalence and frequency rates are discussed in conjunction with clinical reports of OLF. Using the skeletal sample from Kilkenny, the existence of OLF is quantified, using a macroscopic recording methodology adapted for archaeological human remains from which the following hypotheses are formed:

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