Increased Prevalence of Ossification of Posterior Longitudinal Ligament and Increased Bone Mineral Density in Patients with Ossification of Nuchal Ligament

Potential Link between Ossification of Nuchal Ligament and the Risk of Cervical Ossification of Posterior Longitudinal Ligament: Evidence and Clinical Implication from a Meta-Analysis of 8429 Participants

OBJECTIVE

The aim of the present paper was to evaluate the strength and the magnitude of the association between ossification of the nuchal ligament (ONL) and the risk of cervical ossification of the posterior longitudinal ligament (COPLL) and to determine whether there is a direct association or whether COPLL is a consequence of shared risk factors.

METHODS

Medline, Web of Science, Cochrane Library, and Embase databases were searched for studies evaluating the association of COPLL-ONL published before July 2020. Eligible studies were selected based on certain inclusion and exclusion criteria. Two investigators independently conducted the quality assessment and extracted the data, including study designs, countries, patients' age, gender, body mass index (BMI), and the risk of COPLL between individuals with and without ONL. A meta-analysis of homogenous data, a sensitivity analysis, a publication bias assessment, and a subgroup analysis were performed using Stata 12.0 software.

RESULTS

A total of 10 cohort studies involving 8429 participants were incorporated into this analysis. Pooled results demonstrated a statistically significant association between the presence of ONL and the increased COPLL risk (odds ratio [OR] 3.84; 95% confidence interval [CI] 2.68-5.52, P < 0.001). Furthermore, subgroup analyses indicated that this association was independent of study design (6.36-fold in case-control studies vs 3.22-fold in cross-sectional studies), sex (6.33-fold in male-female ratio >2.5 vs 2.91-fold in male-female ratio <2.5), age (4.28-fold in age ≥55 years vs 3.45-fold in age <55 years), and BMI (3.88-fold in BMI ≥ 25 kg/m² vs 2.43-fold in BMI < 25 kg/m² ), which also indicated that obese, older male patients with ONL had a higher risk of OPLL. Moreover, combined two articles revealed that patients with larger-type ONL had a significantly higher risk of long-segment COPLL compared with controls (OR 1.86; 95% CI 1.41-2.47, P < 0.001).

CONCLUSION

This is the first meta-analysis to demonstrate a strong and steady association between ONL and higher risk of COPLL. This association was independent of sex, age, and BMI. Considering that ONL is generally asymptomatic and easily detectable on X-ray, our findings implied that ONL might serve as an early warning sign of the onset of COPLL and provide clinicians an opportunity for early detection and early intervention.

Ossification of Posterior Longitudinal Ligament of Cervical Spine Among Omani Patients Referred for CT Scan at a Tertiary Care Hospital in Oman

Objectives

We sought to evaluate the proportion of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine and associated factors among Omani patients.

Methods

We reviewed the cervical spine computed tomography (CT) scans of all patients referred to the Radiology Department, Sultan Qaboos University Hospital, from 2011 to 2017. Descriptive statistics were employed to determine the proportion of OPLL. We used the chi-square test to determine the association of age, gender, and diabetes mellitus with OPLL.

Results

A total of 843 patients aged ≥ 20 years were included in the study. The proportion of OPLL was 2.7% and was more frequent in men (3.2%) than women (1.9%). The male to female ratio of OPLL was 1.7:1.0. OPLL occurrence was significantly more in non-diabetic patients (p < 0.001). No significant association was found between OPLL with gender (p = 0.281) and age (p = 0.878).

Conclusions

The observed proportion of OPLL in this single-center study is relatively low, but the finding is important as the condition can eventually lead to debilitating neurologic outcomes affecting the patient's quality of life. OPLL occurrence was significantly more in non-diabetic patients, which necessitate further research on OPLL in a larger sample across Oman.

Radiographic Features and Correlation Analysis of Location of Ossification in Patients with Cervical Ossification of the Posterior Longitudinal Ligament Combined with Ossification of the Nuchal Ligament

OBJECTIVE

To investigate the incidence, distribution characteristics, and radiographic features of the ossification of the posterior longitudinal ligament (OPLL) combined with ossification of the nuchal ligament (ONL) and to analyze the correlation between the location of ONL and degree of ossification in patients with cervical OPLL.

METHODS

From January 2010 to December 2016, the clinical data of 217 patients with cervical OPLL were reviewed retrospectively. Type and location of OPLL and ONL were determined on computed tomography images and lateral radiograph films. For patients with the local type of ONL, the segment with the largest spinal canal occupation ratio (COR) of OPLL was determined on cross-sectional computed tomography slices. The correlation between the location of ONL and segment with the largest COR of OPLL was evaluated.

RESULTS

Of the 217 patients with cervical OPLL, 118 patients (54.4%) had OPLL combined with ONL (92 male and 26 female patients). The incidence of ONL was almost 1.4 times greater in males than in female patients (P = 0.03). C5-C6 (49.5%) was the segment at which ONL occurred most. Of 60 patients with the local type of ONL, 34 patients' ONL was located at the segment with largest COR of OPLL. The matching ratio was the largest (77.8%) when the type of OPLL was locally circumscribed (P = 0.003).

CONCLUSIONS

The incidence of ONL was 54.4% in patients with cervical OPLL, and male patients were affected more than female patients. ONL occurred most in segment C5-C6. The location of local-type ONL commonly corresponded to the segment with the largest COR of OPLL when type of OPLL was circumscribed.

Factors associated with bone metabolism in patients with cervical ossification of the posterior longitudinal ligament accompanied with diffuse idiopathic skeletal hyperostosis

INTRODUCTION

Diffuse idiopathic skeletal hyperostosis (DISH) and ossification of the posterior longitudinal ligament (OPLL) are both characterized as ossification in paravertebral ligaments and sometimes present simultaneously, however, the bone metabolism in patients with cervical OPLL accompanying/not accompanying DISH has not well been studied. Thus, a retrospective analysis was performed to understand any differences in bone metabolism in these patients.

METHODS

Male patients who underwent surgery for OPLL were divided into two groups based on the presence or absence of DISH (OD and O group, respectively). Patients with cervical spondylosis comprised the control group (CS group). Bone mineral density (BMD) and bone metabolism factors were compared among the groups.

RESULTS

The OD and O groups had significantly higher body mass indexes (BMIs) than did the CS group. Morphologically, the number of continuous type of OPLL was high in the OD group whereas that of segmental type was higher in the O group. The OD and O group had greater BMD than the CS group. Both TRACP-5b and P1NP were tended to be lower in the OD group whereas Ca and P concentrations were similar level among the groups. Intact parathyroid hormone in OD group was significantly higher than CS group.

DISCUSSION

Patients with OPLL accompanying DISH had significantly higher BMD whereas they tend to be lower in bone turnover. Significantly higher i-PTH levels was found in the OD group and would be the characteristic blood marker, but further research on the relationship between DISH and PTH was necessary.

Evaluating Ossifications of the Nuchal Ligament with Cervical Computed Tomography

OBJECTIVE

The nuchal ligament (NL) extends from the external occipital protuberance and median nuchal line to the spinous process of the 7th cervical vertebrae. In this study, we evaluated the incidence, location level, and size of ossifications of the NL (ONL) in patients who underwent cervical computed tomography (CT) for various reasons.

MATERIALS AND METHODS

The present study included 481 patients (187 females and 294 males) who underwent cervical CT from February 2011 to November 2016 due to reasons such as trauma, cervical spondylosis, neck pain, and screening for metastasis. CT was performed using 2- or 8-slice scanners. Archive images of patients on picture archiving and communication system were retrospectively evaluated by two radiologists. The structures in bone density and form detected in NL were evaluated as nuchal ossification. ONL location levels, numbers, and dimensions were determined. The relationship between both sexes and age and the incidence of ONL was investigated.

RESULTS

ONL was detected in 44 patients (9.14%). The mean ages of patients with ONL and without ONL were 62.27±13.92 (23-86) and 41.78±20.76 (4-101) years, respectively. There was a statistically significant relationship between ONL and age (p<0.001). Thirty-six patients had one ONL, seven patients had two, and one patient had three. The most common ONL location was the C5 spinous process level (n=12) followed by the C6 spinous process level (n=8). The longest ONL in craniocaudal direction was 20.9 mm, and the shortest one was 3.1 mm.

CONCLUSION

ONL is a smooth-contoured ovoid or round bone structure extending parallel to the longitudinal axis that can frequently be observed as one or multiple occurrences with different sizes on cervical CT images.