Ossification of the posterior longitudinal ligament (OPLL) in the cervical spine and related neurological complications are not uncommon in East Asian countries. The estimated prevalence of cervical OPLL-related hospitalization is 7.7 per 100,000 person-years in Taiwan, and higher incidence rates have been observed in elderly and male patients 3).
Genetic factors are considered to play an important role in the etiology of OPLL based on nationwide pedigree surveys, twins surveys, and human leukocyte antigen (HLA) haplotype analysis 4).
The relationship between single-nucleotide polymorphisms (SNPs) in various genes and OPLL has been studied. A case-control association and sib-pair linkage studies have shown that several genes are related to the suscepti- bility to OPLL. These include genes for collagen, type VI, alpha 1 (COL6A1), collagen, type XI, alpha 2 (COL11A2), bone morphogenetic protein 2 (BMP2), ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), estrogen receptor 1 (ESR1), interleukin-1 beta (IL1B), leptin receptor, and transforming growth factor beta 1 (TGFB1) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14).
The progression of cervical ossification of the posterior longitudinal ligament (OPLL) can lead to increase in the size of the OPLL mass and aggravation of neurological symptoms.
The most characteristic symptom of OPLL is myelopathy resulting from the compression of the spinal cord; other signs and symptoms include sensory dysfunction of the upper and the lower extremities, motor weakness, an in- creased deep tendon reflex, and neurogenic bladder and bowel 15). 16) 17).
OPLL is not a two-dimensional (2D) disease, but rather a three-dimensional (3D) disease. Therefore, conventional measurement of parameters using radiography may not be suitable for evaluating OPLL.
3D method of measurement is superior to the conventional method in terms of evaluating the clinical state of symptomatic OPLL patients. Higher 3D OPLL ratio has an adverse effect on the spinal cord 18).
There are multiple options for managing cervical OPLL, ranging from observation to many kinds of surgical procedures, including posterior laminoplasty, laminectomy with or without fusion, anterior corpectomy with or without instrumentation, and circumferential decompression and fusion. None of these surgical approaches is free of complications. However, to date, there is still a lack of consensus regarding the choice of the surgical approach and the timing of surgical intervention. Cervical SCI and related neurological disabilities are more likely to occur in OPLL patients, who should therefore be cautioned regarding the possibility of a subsequent SCI if treated without surgery 19).
Anterior cervical spine decompression and reconstruction is a safe and appropriate treatment for cervical myelopathy in the setting of single or two level OPLL. Cervical laminectomy or laminoplasty is indicated in patients with preserved cervical lordosis having three or more levels of involvement. Younger patients with good pre operative functional status and less than 2 levels of involvement have better outcome following anterior surgery 20).
A retrospective study included patients (662 males and 251 females; mean age 55.8 years) with symptomatic OPLL. All patients had been diagnosed with OPLL based on cervical magnetic resonance imaging and computed tomography scans. Demographic, surgical outcome was measured using visual analog scale (VAS) and Japanese Orthopedic Association (JOA) scale scores. The results of our study indicated radicular pain was more common in segmental and circumscribe OPLL subtypes (P < 0.05). An anterior approach was favored in patients with less than 3 involved vertebral levels (P < 0.05). All surgical methods showed good outcomes (P < 0.05). Continuous and mixed OPLL subtypes showed worse surgical outcome with higher VAS and JOA scores (P < 0.05). Laminoplasty and anterior cervical discectomy and fusion were significantly associated with a higher recovery rate (P < 0.05). Among these patients, there were more complications with the anterior approach (P < 0.05). Male gender, open door laminoplasty ipsilateral, and ipsilateral-to-symptom-side opening were associated with postoperative C5 palsy (P < 0.05). Cervical OPLL may cause myelopathy, surgery is a safe and effective treatment for OPLL. There were no differences in clinical outcome according to surgical type, but complication rates varied depending on sex and surgical approach to symptom 21).
Moon et al., from the Departement of Neurosurgery, Chonnam National University Hospital and Medical School, Gwangju, Korea. examined the prevalence and incidence of cervical OPLL. Age/sex-matched controls were randomly extracted, with 10 times the number of OPLL cases. The differences in sex, co-morbidity, and relative survival rate, compared with controls, were assessed.
The cumulative prevalence was 20,960 per 1,025,340 people for 12 years. The annual incidence was approximately 199 to 371 per 1 million people. Overall, the crude mortality rate was 7.64%. The relative survival rate of OPLL cases was not significantly different from that of control cases. Diabetes, hypertension, cardiovascular disease, and cerebrovascular disease, except renal disease, correlated significantly with OPLL, compared with controls (p < 0.001). Additionally, between dead and surviving patients among the OPLL cases, all co-morbidities correlated more significantly with death (p < 0.001). Further, between the surgery and non-surgery cases of OPLL, diabetes, hypertension, and renal disease (p < 0.05) were significantly associated with surgery.
The annual incidences of OPLL were from 199 to 371 per 1,025,340 people for 10 years. Diabetes, hypertension, cardiovascular disease, and cerebrovascular disease, except renal disease, correlated significantly with OPLL, compared with controls. Especially, diabetes, hypertension, and renal disease were associated with OPLL patients who underwent surgery 22).
Sixty patients with cervical OPLL were included. All underwent an initial CT examination and had at least 24 months' follow-up with CT. The mean duration of follow-up was 29.6 months. Fourteen patients (Group A) had CT evidence of OPLL progression, and 46 (Group B) did not show evidence of progression on CT. The 2 groups were compared with respect to the following variables: sex, age, number of involved segments, type of OPLL, and treatment methods. The CT findings, such as the connection of an OPLL mass with the vertebral body and formation of trabeculation in the mass, were evaluated.
Sex and treatment modality were not associated with OPLL progression. The mean age of the patients in Group A was significantly lower than that in Group B (p = 0.03). The mean number of involved segments was 5.3 in Group A and 3.6 in Group B (p = 0.002). Group A had a higher proportion of cases with the mixed type of OPLL, whereas Group B had a higher proportion of cases with the segmental type (p = 0.02). A connection between the vertebral body and OPLL mass and trabeculation formation were more common in Group B (p < 0.01).
Progression of cervical OPLL is associated with younger age, involvement of multiple levels, and mixed-type morphology. OPLL masses that are contiguous with the vertebral body and have trabecular formation are useful findings for identifying masses that are less likely to progress 23).