The Clinical Significance of Ossification of Ligamentum Nuchae in Simple Lateral Radiograph : A Correlation with Cervical Ossification of Posterior Longitudinal 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.

Association between ossification of the posterior longitudinal ligament and ossification of the nuchal ligament in the cervical spine

OBJECTIVES

To investigate the association between ossification of the posterior longitudinal ligament (OPLL) and ossification of the nuchal ligament (ONL) in terms of incidence and size.

METHODS

This retrospective study evaluated 297 patients who underwent CT of the cervical spine (C-spine). Two radiologists worked in consensus. The incidence of OPLL from patients with and without ONL was compared using Chi Square tests. The mean lengths of ONL from patients with and without OPLL were compared using Student t-test. The correlations between the length of ONL and the presence of OPLL and between the length of ONL and the length of OPLL were analyzed with Pearson correlations.

RESULTS

We found that OPLL occurred more frequently in patients with ONL than in patients without ONL (odd ratio = 2.524, p = 0.037); however, the mean length of ONL did not differ significantly patients with and without OPLL (p = 0.874). We found no significant correlation between the length of ONL and the length of OPLL (p = 0.233).

CONCLUSION

The presence of ONL was associated with the presence of OPLL. The length of OPLL and ONL showed no correlation.

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.

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.

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

Objective

There are also few studies demonstrating the relationship between ossification of nuchal ligament (ONL) and ossification of posterior longitudinal ligament (OPLL). We compared the prevalence, location, and type of OPLL between patients with ONL and matched patients without ONL.We also compared the bone mineral densities (BMDs) between the 2 groups.

Methods

total of 124 cervical ONL patients were enrolled in this study. The control group of 124 patients was matched with 124 patients with ONL by age and sex on a 1:1 basis to minimize confounding factors. We reviewed the prevalence, location, and type of OPLL in both groups.

Results

The prevalence of OPLL was almost 2.5 times greater in patients with ONL than those without ONL. The mean value of BMD in patients with ONL was greater at the lumbar spine (L1-L4) than in patients without ONL. The mean T score of the lumbar spine was 0.25±1.68 in the patients with ONL and -0.73±1.64 in the patients without ONL.

Conclusion

The prevalence of OPLL in patients with ONL was significantly higher than in patients without ONL. Because ONL is innocuous and may be seen more readily than OPLL on simple cervical radiographs, clinicians should consider the possibility of coexisting OPLL when ONL, especially extensive ONL, is detected in patients with neck pain, radiculopathy, or myelopathy, to facilitate proper treatment.