Ossification of the Posterior Longitudinal Ligament in Not Only the Cervical Spine, but Also Other Spinal Regions

Abstract

This study demonstrated that more than half of the patients with cervical OPLL had coexisting OPLL in the thoracic and/or lumbar spine. We strongly recommend computed tomographic analysis of the whole spine for patients with radiographical evidence of OPLL in the cervical spine for the early detection of additional sites of ossification.

Prevalence and Distribution of Ossified Lesions in the Whole Spine of Patients with Cervical Ossification of the Posterior Longitudinal Ligament A Multicenter Study (JOSL CT study)

“…Kappa values 0.00–0.20 were considered to indicate slight agreement; 0.21–0.40, fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, substantial agreement; and 0.811.00, almost perfect agreement [17]. Therefore, this finding indicates substantial agreement and consistency with the results of the previous study [9]. We also evaluated the degree of OPLL occupying the cervical spinal canal, with classification of the canal narrowing ratio (CNR) [18] at the most compressed segment defined as follows: Grade 1, 0% < CNR ≤ 25%; Grade 2, 25% < CNR ≤ 50%; Grade 3, 50% < CNR ≤ 75%; and Grade 4, CNR > 75%.…”

“…This finding is consistent with evidence that female patients tend to have OPLL in the thoracic spine—the area of the spine in which the number of vertebral and intervertebral levels is greatest—and indicates that hormonal factors could affect the development of OPLL in the whole spine. Although the details of why patients with multiple ossified lesions are predominantly female remain unclear, several studies have suggested possible mechanisms linking sex and hyperostosis [9,21–23]. Serum estrogen level has been shown to correlate with the onset and extension of ossified lesions, and estrogen is thought to stimulate osteoblast-like cells with the aid of trophic factors [9,21,22].…”

“…Image analysis was independently performed by five senior spine surgeons (T.H., K.T., K.M., A.I., and T.Y.). To quantify hyperostosis of the posterior longitudinal ligament, the distribution of OPLL at each vertebral body and intervertebral disc level was recorded, and the number of levels at which OPLL was present was defined as the ossification index (OP-index), as described previously [9]. The number of ossified lesions in the cervical spine was defined as the cervical OP-index.…”

“…Recently, increased use of multi-detector computed tomography (CT) has contributed to recognition of a higher prevalence of ossified lesions than has been found by the previous method using plain X-rays [14]. A previous single-institution CT study demonstrated that patients with cervical OPLL had a high incidence of OPLL in the thoracolumbar spine [9]. It has been well documented that prognosis and surgical outcomes are worse in patients with multiple-regional OPLL than in patients with cervical lesions alone [15].…”

“…Although a single-institution CT study has reported the prevalence of ossified lesions in patients with cervical OPLL [9], we conducted the present multicenter CT study with the aim of not only evaluating the prevalence of OPLL in the whole spine among patients with cervical OPLL in order to strengthen the evidence, but also using a multiple regression model to investigate the factors that correlate with the presence and distribution of ossified lesions in the whole spine.…”