Prevalence of ossification of the posterior longitudinal ligament (OPLL) in the Pacific populations in Auckland, New Zealand: A retrospective multicentre study

Introduction

Primary objective was to investigate the prevalence of ossification of the posterior longitudinal ligament (OPLL) in a mixed demographic region, especially in the Pacific Island population. Secondary objective was to investigate the prevalence of diabetes mellitus and cervical diffuse skeletal hyperostosis (DISH) in patients with and without OPLL.

Methods

Using the local picture archiving and communication system (PACS), cervical spine computed tomography (CT) examinations over a 2-month period were retrospectively assessed for the presence of OPLL. Basic demographic data were recorded—gender, age, ethnicity, presence of cervical DISH and the presence or absence of diabetes mellitus.

Results

A total of 1692 CT examinations were included in the study. The distribution of the ethnic groups was 57.3% European, 12.09% Pacific peoples, 11.9% Māori, 11.53% Asian, 0.95% Middle Eastern/Latin American/African and 6.3% not specified. Overall, 47 cases of OPPL were identified (2.78%). The prevalence of OPPL in the Pacific ethnic groups was significantly higher than the European ethnic group 8.4% versus 0.6%, P < 0.05. The prevalence of OPLL was also significantly higher in the Asian (6.9%) and Māori (3.6%) than in the European ethnic group, P < 0.05. A significantly higher proportion of the patients with OPLL had underlying diabetes 20/47 (42.6%) compared with the study population 196/1692 (11.6%), P < 0.05. Seven cases of OPPL (14.9%) had associated cervical DISH, which was significantly higher compared with the study group (23/1692), P < 0.05. Using the Japanese Ministry of Health and Welfare classification system⁴, segmental type was the most common (34/47, 72.3%), followed by mixed (14.9%) and continuous types (12.8%).

Conclusion

The prevalence of OPLL is significantly higher among the Pacific populations in Auckland. There is also increased prevalence in the Asian and Māori populations.