How does the ossification area of the posterior longitudinal ligament progress after cervical laminoplasty?

Reduced Vertebral Hounsfield Unit Values in the Bridging Group of Ossification-Related Segments in Patients with Ossification of the Posterior Longitudinal Ligament of the Cervical Spine

BACKGROUND

Increased systemic bone mineral density has been reported in patients with ossification of the posterior longitudinal ligament (OPLL). This study investigated the differences in vertebral Hounsfield unit (HU) values between the bridged and nonbridged groups of patients with OPLL of the cervical spine at the ossification-related segments.

METHODS

A total of 436 ossification-related segments from 157 patients were involved in the study. X-ray and computed tomography scans were used to assess the segmental cervical range of motion (ROM), C2-7 Cobb angle, K-line, ossification thickness, maximum canal occupancy, HU values, and presence and type of OPLL.

RESULTS

In terms of imaging parameters, HU values were significantly higher in the OPLL group (P < 0.001), whereas the ROM was greater in the control group (P < 0.05). In the OPLL group, the K-line positive group had a better C2-7 Cobb angle and greater T1 slope. The ossification-related segments were divided into bridging and nonbridging groups, with smaller vertebral HU values, thicker ossification lesions, greater canal occupation, and reduced interbody mobility in the bridging group. However, we found no significant correlation among segmental ROM, ossified material thickness, maximum canal occupancy of the ossified material, and segmental HU values.

CONCLUSIONS

We found that the mean HU value of the cervical spine in patients with OPLL was higher than that of the control group, and the ROM was smaller than that of the control group, with the smallest ROM in the continuous type. In the ossification-related segments, the bridging group exhibited lower vertebral HU values, reduced segmental mobility, and thicker ossification thickness.

Ossification of the Posterior Longitudinal Ligament in the Cervical Spine: Etiology, Clinical Presentation, and Management

» Ossification of the posterior longitudinal ligament (OPLL) is a hyperostotic condition that results in ectopic bone formation and calcification of the posterior longitudinal ligament.» OPLL can present in any race/ethnicity but historically has been reported in the East Asian population.» OPLL predisposes patients to spinal cord injury in the setting of minor trauma.» Asymptomatic patients typically can be managed nonoperatively. Surgical treatment is reserved for patients presenting with myelopathy and worsening radiculopathy that has not responded to conservative treatment.» The decision to use anterior, posterior, or combined anterior-posterior approaches should be an individualized decision that considers the degree of OPLL pathology, K-line imaging findings, and other patient-specific risk factors.

Ossification of Posterior Longitudinal Ligament Growth in the C1/2 Segment and its Clinical Significance: Is C2 Total Decompression Necessary?

STUDY DESIGN

A retrospective analysis at a single institution.

OBJECTIVE

This study aimed to determine whether ossification of posterior longitudinal ligament (OPLL) growth in the C1/2 area remains clinically uneventful despite visible radiologic enlargement.

BACKGROUND

In cervical decompressive surgery for OPLL, preserving the C2 lamina is preferred for stability, and the larger spinal canal space above C2 tends to mitigate clinical issues caused by OPLL growth. However, the effects of OPLL progression in the C1/2 segment, which often remains untreated, on patients' clinical outcomes are unclear.

PATIENTS AND METHODS

We enrolled 144 patients with cervical OPLL who underwent decompression surgery between January 2011 and December 2018. The patients were categorized based on whether they underwent a C2 sparing procedure or C2 laminectomy. The primary outcome was radiologic progression of OPLL, defined as a 2 mm increase in sagittal thickness or longitudinal elongation, and its correlation with clinical symptoms.

RESULTS

Of the 144 patients, 35 were in the C2 sparing group, and 109 were in the C2 laminectomy group, with an average follow-up period of 5.2 to 5.6 years. The rate of radiologic progression of OPLL in the C1/2 segment was comparable between the two groups (54.3% vs. 51.4%, P = 0.916). However, diagnosis of C1/2 stenosis at the final follow-up was still lower in the C2 sparing group than in the C2 laminectomy group (2.9% vs. 10.1%, P = 0.294), and there were no new cases of symptoms caused by cord compression in the C1/2 segment in either group.

CONCLUSION

OPLL in the C1/2 segment was clinically silent despite radiologic growth. For patients who do not present with significant canal stenosis or cord compression due to OPLL above the C2 upper lamina, C2 lamina-sparing decompressive surgery is preferred.

LEVEL OF EVIDENCE

Level III.

Radiographic characterization of OPLL progression in patients receiving laminoplasty with a minimum of two-years follow-up

Ossification of the posterior longitudinal ligament (OPLL) is a common cause of degenerative cervical myelopathy (DCM) in Asian populations. Characterization of OPLL progression following laminoplasty remains limited in the literature. 29 patients with OPLL received cervical laminoplasty and a minimum of 2-years follow-up. Clinical and radiological surveillance occurred at 3-months, 6-months, 12-months post-op and then at yearly intervals. Transverse (anteroposterior) diameter and sagittal length of OPLL in relation to their cervical vertebral level of localisation was assessed upon immediate post-op radiographs compared to those obtained at subsequent follow-up. OPLL progression was defined as an increase in transverse dimensions and/or length by ≥ 2 mm. The average period of clinical follow-up was 6.7 ± 3.3 years. Upon latest follow-up, 79% of patients demonstrated at least 2 mm of transverse or longitudinal progression of OPLL. This corresponded to 2-years and 5-year progression rates of 54% and 71% respectively. OPLL located over C5 demonstrated the greatest transverse progression rate at (0.24 ± 0.34 mm / year). The mean overall longitudinal progression rate was 1.61 ± 2.06 mm / year. No patients experienced neurological decline resulting from OPLL progression requiring revision decompression during the period of post-operative observation. Characterizing transverse and longitudinal progression by cervical level via radiographs has implications in surgical planning for OPLL and should be consolidated upon post-operative CT/MRI scans as well as larger sample sizes.

Comparison of Anterior Controllable Antedisplacement and Fusion Versus Laminoplasty in the Treatment of Multisegment Ossification of Cervical Posterior Longitudinal Ligament: A Meta-Analysis of Clinical

OBJECTIVE

This study aims to provide a comprehensive summary of the existing literature and conduct a systematic evaluation of the clinical outcomes associated with anterior controllable antedisplacement and fusion (ACAF) and posterior laminoplasty (LP) for the treatment of multisegment ossification of the cervical posterior longitudinal ligament (OPLL).

METHODS

We conducted an electronic search of databases, including PubMed, Embase, Cochrane Library, and CNKI, from the inception of the initial database to March 2023. We analyzed various parameters, including demographic data, operation time, intraoperative blood loss, cervical curvature, Japanese Orthopaedic Association (JOA) scores, Visual Analog Scale (VAS) scores, and postoperative complications. Two independent reviewers screened the literature, extracted data, and assessed the risk of bias in the included studies. Meta-analysis was performed using RevMan 5.4 software.

RESULTS

Our evaluation encompassed 7 studies involving a total of 467 patients. The patient cohort was divided into 2 groups: Group A (ACAF) comprised 226 patients, while Group B (LP) comprised 241 patients. Overall, our statistical analysis revealed significant differences between the 2 groups (P < 0.05) in terms of intraoperative blood loss, operative time, JOA score, JOA score improvement rate, postoperative VAS score, postoperative cervical curvature, and the incidence of certain postoperative complications (C5 nerve root paralysis, dysphagia, and axial symptoms). However, there was no statistically significant difference in the incidence of postoperative cerebrospinal fluid leakage and postoperative total complications between the 2 groups (P > 0.05).

CONCLUSIONS

The findings of this study suggest that, in the treatment of multilevel cervical OPLL, ACAF yields superior outcomes compared to LP. Specifically, ACAF improves postoperative neurologic function, reduces postoperative pain, lowers intraoperative blood loss, improves postoperative cervical curvature, and decreases the incidence of C5 nerve root paralysis and postoperative axial symptoms. Nonetheless, ACAF is associated with longer operative times and a higher incidence of postoperative dysphagia, though the overall incidence of postoperative complications is similar. It is important to note that these conclusions should be interpreted cautiously due to the limited sample size and the variable quality of the included studies. Further research involving larger, high-quality studies is warranted to validate these findings.

True Continuous Segment of Ossification of Posterior Longitudinal Ligament is Protective Against Postoperative Early Kyphosis Progression After Laminoplasty

BACKGROUND AND OBJECTIVES

Ossification of the posterior longitudinal ligament (OPLL) is a potentially catastrophic disease. Laminoplasty (LP) is a common surgical intervention, but postoperative kyphosis progression is a major complication, for which various risk factors have been identified and used in surgical decision-making. Our focus is on the ability of OPLL with specific morphological traits, designated as the true continuous segment (TCS), to stabilize alignment and prevent postoperative kyphosis after LP.

METHODS

This retrospective case-control study included patients who underwent cervical LP for OPLL treatment with a minimum 1-year follow-up. Demographic, operative, and radiographic parameters were analyzed. TCS is defined as a continuous segment of OPLL that spans the disk space more than half of the adjacent vertebral body height without crack, or OPLL segment attached to both upper and lower adjacent vertebral bodies by bridging, or obvious interbody autofusion, and is identified from preoperative computed tomography. A subgroup analysis for preoperatively lordotic patients, divided into 2 groups based on cervical alignment at the final follow-up, was conducted to identify risk factors for kyphosis progression. Difference analysis, linear regression analysis for loss of lordosis (LoL), and logistic regression analysis for kyphosis progression were used.

RESULTS

A total of 84 patients were identified. Among them, 78 patients with preoperatively lordotic alignment were divided into 2 groups: those who maintained lordotic alignment (n = 60) and those who progressed to kyphosis (n = 18). Regression analyses revealed a significant protective effect of TCS count against LoL and postoperative kyphosis, with a TCS count of 3 or more conclusively preventing kyphosis (sensitivity 1.000, specificity 0.283, area under the curve 0.629).

CONCLUSION

For patients with OPLL, TCS was shown to protect against the LoL after LP. Therefore, TCS should be identified and considered when planning surgical treatment for OPLL.

Prevalence and characteristics of thoracic ossification of the posterior longitudinal ligament in 3299 Black patients: a cross-sectional study of a prospectively registered database

OBJECTIVES

To the best of our knowledge, the prevalence of thoracic ossification of the posterior longitudinal ligament (T-OPLL) in the Black population has never been studied and is still unknown. The purpose of this study was to examine the prevalence and characteristics of T-OPLL in the Black patients.

METHODS

This is a cross-sectional study. All patients who underwent chest CT for the trauma screening and whose race was classified as 'Black' on the questionnaire were recruited in the study from March 2019 to March 2020. Demographic data, including age, sex, body mass index (BMI) and presence of diabetes mellitus (DM), were recorded. T-OPLL was defined as ectopic OPLL of more than 2 mm thickness in the axial plane image of the CT scan. The prevalence and characteristics of T-OPLL, and the association of T-OPLL with BMI and DM were evaluated.

RESULTS

A total of 3299 Black patients (1507 women and 1792 men) were included for the analysis. The prevalence of T-OPLL was 1.5% (50 patients), with 2.4% for females and 0.8% for males. The highest prevalence was observed in patients at the age of 70 years (3.8%). Thickness of T-OPLL was between 2 and 3 mm in 46% (23/50) of the patients, and the largest thickness was 6.1 mm. T-OPLL was significantly associated with female sex and the presence of DM.

CONCLUSIONS

The prevalence of T-OPLL was 1.5% in the 3299 Black patients who underwent chest CT for the trauma screening, with 2.4% for females and 0.8% for males.

Distinct progression pattern of ossification of the posterior longitudinal ligament of the thoracic spine versus the cervical spine: a longitudinal whole-spine CT study

OBJECTIVE

Data regarding risk factors for the progression of ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine are scarce. Therefore, in this study, the authors aimed to elucidate the difference in the radiographic progression pattern of OPLL and its risk factors between cervical and thoracic OPLL using longitudinally acquired whole-spine CT scans.

METHODS

Overall, 123 patients with symptomatic OPLL who underwent repeated whole-spine CT examinations, with an average interval of 49 months (at least 3 years) between scans, were retrospectively reviewed. Progression of OPLL was assessed to compare the distribution of OPLL over the entire spine on the initial and final CT scans. Patients were divided into a cervical OPLL (C-OPLL) group and a thoracic OPLL (T-OPLL) group according to the location of the main lesion. The progression pattern of OPLL and its risk factors were compared between the two groups using the Student t-test or Mann-Whitney U-test.

RESULTS

In the C-OPLL group, 15 (22.1%) of 68 patients had OPLL progression, of whom 12 patients (80.0%) had progression only in the cervical spine and 3 patients (20.0%) had progression in multiple regions (cervical and thoracic/lumbar). In the T-OPLL group, 16 (29.1%) of 55 patients had OPLL progression, of which 3 patients (18.8%) had progression only in the thoracic spine and 8 patients (50.0%) had progression in multiple regions. Young age was a common risk factor for OPLL progression regardless of the location of OPLL, and this trend was more pronounced in the T-OPLL group than in the C-OPLL group. High BMI, male sex, and multilevel, severe T-OPLL were identified as independent risk factors for progression of T-OPLL (OR 1.19, 95% CI 1.03-1.37; OR 10.5, 95% CI 1.39-81.94; and OR 1.24, 95% CI 1.16-1.45, respectively).

CONCLUSIONS

Patients with T-OPLL are predisposed to diffuse progression of OPLL over the entire spine, whereas patients with C-OPLL are likely to have progression in only the cervical spine. Young age and high BMI are significant risk factors for OPLL progression, especially in patients with T-OPLL. Our study highlights the need for continued follow-up in patients with T-OPLL, especially in young patients and those with obesity, for early detection of spinal cord and cauda equina symptoms due to the progression of OPLL throughout the spine.

Progression of Ossification of Posterior Longitudinal Ligament After Anterior Cervical Discectomy and Fusion in Military Patients Exposed to Minor Trauma

Objective

Ossification of the posterior longitudinal ligament (OPLL) can progress even after cervical spine surgery and may cause neurological injury as a result of minor trauma. The purpose of this study was to investigate the preventive factors associated with OPLL progression after anterior cervical discectomy and fusion (ACDF), a procedure commonly performed in clinical practice.

Methods

We retrospectively investigated 295 male soldiers who underwent ACDF surgery between 2012 and 2017. Patients who were followed up for >12 months using dynamic radiography and computed tomography (CT) were included in the study. Radiological parameters investigated included OPLL progression, C2-C7 angles on dynamic radiography, segmental angles, C2-C7 cervical sagittal vertical axis (C2-C7 SVA), and the T1 slope. These parameters were measured preoperatively and 1 year postoperatively.

Results

A total of 49 patients were enrolled, and 10 patients were confirmed to have OPLL progression. Comparison between the OPLL progression and non-progression groups showed no statistically significant differences in pre- and postoperative cervical range of motion. However, statistically significant differences were observed in the postoperative neutral C2-C7 angle (progression -3.9°±6.4° vs. non-progression -13.4°±7.9°, p=0.001) and the SVA change (progression 5.8±7.9 mm vs. non-progression -3.7±6.3 mm, p=0.00). The cutoff values were -8.01° for the postoperative neutral C2-C7 angle and 1.4 mm for SVA changes.

Conclusion

Increased SVA (>1.4 mm) and a small postoperative neutral C2-C7 angle (>-8.01°) 1 year after ACDF were associated with OPLL progression. It is important to be mindful of these factors during follow-up after ACDF, because additional surgical treatment may be necessary for OPLL progression due to neurological injury caused by minor trauma.

Unveiling the genetic variation of severe continuous/mixed-type ossification of the posterior longitudinal ligament by whole-exome sequencing and bioinformatic analysis

BACKGROUND CONTEXT

Ossification of the posterior longitudinal ligament (OPLL) in the cervical spine is known as a rare, complex genetic disease, its complexity being partly because OPLL is diagnosed by radiological findings regardless of clinical or genetic evaluations. Although many genes associated with susceptibility have been reported, the exact causative genes are still unknown.

PURPOSE

We performed an analysis using next-generation sequencing and including only patients with a clear involved phenotype.

STUDY DESIGN/SETTING

This was a case control study.

PATIENT SAMPLE

A total of 74 patients with severe OPLL and 26 healthy controls were included.

OUTCOME MEASURES

Causal single-nucleotide variant (SNV), gene-wise variant burden (GVB), and related pathway METHOD: We consecutively included the severe OPLL patients with continuous-/mixed-type and an occupying ratio of ≥ 40%, and performed whole-exome sequencing (WES) and bioinformatic analysis. Then, a validation test was performed for candidate variations. Participants were divided into 4 groups (rapidly-growing OPLL, growing rate ≥ 2.5%/y; slow-growing, < 2.5%/y; uncertain; and control).

RESULTS

WES was performed on samples from 74 patients with OPLL (rapidly-growing, 33 patients; slow-growing, 37; and uncertain, 4) with 26 healthy controls. Analysis of 100 participants identified a newly implicated SNV and 4candidate genes based on GVB. The GVB of CYP4B1 showed a more deleterious score in the OPLL than the control group. Comparison between the rapidly growing OPLL and control groups revealed seven newly identified SNVs. We found significant association for 2 rare missense variants; rs121502220 (odds ratio [OR] = infinite; minor allele frequency [MAF] = 0.034) in NLRP1 and rs13980628 (OR= infinite; MAF = 0.032) in SSH2. The 3 genes are associated with inflammation control and arthritis, and SSH2 and NLRP1 are also related to vitamin D modulation.

CONCLUSIONS

Identification of unique variants in novel genes such as CYP4B1 gene may induce the development of OPLL. In subgroup analysis, NLRP1 and SSH2 genes coding inflammation molecules may related with rapidly-growing OPLL.

"Only Spinal Fixation" as Surgical Treatment of Cervical Myelopathy Related to Ossified Posterior Longitudinal Ligament: Review of 52 Cases

BACKGROUND

Ossification of the posterior longitudinal ligament (OPLL) is a hyperostotic condition resulting in a progressive narrowing of the spinal canal and subsequent neurologic deficits. Although systemic and local factors in combination with genetic abnormality have been considered in its etiopathogenesis, OPLL remains a poorly understood pathology. Surgical management of OPLL and the choice of the most appropriate treatment are still controversial issues. Here the authors report a series of OPLL-affected patients treated by "only-fixation" technique.

METHODS

Between June 2012 and June 2019, 52 patients having OPLL were treated by a surgical strategy involving only spinal fixation without any form of bone or soft tissue decompression. Facetal fixation for both the atlantoaxial and subaxial spine formed the basis of the surgical treatment. Clinical parameters, analysis of video recordings before and after surgery, and patient self-assessment were included in the analysis of outcome.

RESULTS

During the mean follow-up period there was an immediate postoperative and progressive recovery in symptoms in 51 patients. Of 14 patients who were wheelchair bound before surgery, 12 walked independently on follow-up assessment of 6 months. All patients had successful arthrodesis in the surgically treated segments. There were no infective- or implant-related complications.

CONCLUSIONS

Decision making in the surgical management of cervical OPLL is still controversial. The concept of spinal instability has been shown to be a nodal point in the pathogenesis of OPLL, and "only-spinal fixation" can be considered a rationale for an appropriate surgical treatment.

Comparison of Anterior Controllable Antedisplacement and Fusion With Posterior Laminoplasty in the Treatment of Multilevel Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective, Randomized, and Control Study With at Least 1-Year Follow Up

STUDY DESIGN

A prospective, randomized, controlled study.

OBJECTIVE

To compare anterior controllable antidisplacement and fusion (ACAF) with laminoplasty in the treatment of multilevel ossification of the posterior longitudinal ligament (OPLL), and evaluate the efficacy and safety of this procedure.

SUMMARY OF BACKGROUND DATA

The optimal approach for the treatment of OPLL still remains controversial. Both anterior and posterior approaches have their advantages and disadvantages.

METHODS

Between September 2016 and April 2018, a total of 80 patients with multilevel OPLL were randomized in a 1:1 ratio to ACAF group and laminoplasty group. All patients were followed up at least 1 year. Clinical and radiological results were compared between ACAF group and laminoplasty group.

RESULTS

ACAF took a longer operation time. C5 palsy and axial pain occurred more commonly in laminoplasty group, whereas dysphagia and hoarseness appeared easily in ACAF group. At 1-year follow-up, the final Japanese Orthopedic Association (JOA) score and recovery rate were significant higher in ACAF group than those in laminoplasty group, when occupying rate (OR) was not less than 60%, or K-line was negative. ACAF was also good at preservation of cervical lordosis and sagittal balance, but range of movement of cervical spine in both groups decreased significantly.

CONCLUSION

Generally speaking, ACAF is a safe and effective alternative for multilevel OPLL. Compared with laminoplasty, ACAF is more effective in the cases when OR is not less than 60%, or K-line is negative.

LEVEL OF EVIDENCE

2.

Posterior decompression and fusion versus laminoplasty for cervical ossification of posterior longitudinal ligament: a systematic review and meta-analysis

Both posterior decompression and fusion (PDF) and laminoplasty (LAMP) have been used to treat cervical myelopathy due to multilevel ossification of posterior longitudinal ligament (OPLL). However, considerable controversy exists over the choice of the two surgical strategies. Thus, the aim of this study is to compare clinical outcomes of PDF and LAMP for treatment of cervical myelopathy due to multilevel OPLL. We searched PubMed, EMBASE and Cochrane Central Register of Controlled Trials database to identify relevant clinical studies compared with clinical outcomes of PDF and LAMP for cervical OPLL. The primary outcomes including Japanese Orthopaedic Association (JOA) score and recovery rate of JOA were evaluated, and the secondary outcomes involving visual analogue scale (VAS), cervical curvature, OPLL progression rate, complication rate, reoperation rate and surgical trauma were also evaluated using Stata software. A total of nine studies were included in the current study, involving 324 patients. The current study suggests that compared with LAMP, PDF achieves a lower OPLL progression rate, better postoperative cervical curvature and similar neurological improvement in the treatment of multilevel cervical OPLL. However, PDF has a higher complication rate, more surgical trauma and higher postoperative VAS than LAMP.

INFLUENCE OF THE MISDEF ALGORITHM ON THE THERAPEUTIC DECISION FOR VERTEBRAL DEFORMITY IN THE ADULT

ABSTRACT Objective The therapeutic decision in cases of adult spinal deformity takes numerous factors into account with a consequent variability in treatment options. The objective is to compare the impact of the MISDEF (minimally invasive spine deformity) algorithm on therapeutic decisions in cases of adult spinal deformity. Methods Prospective radiographic analysis of 40 cases of adult deformity. The cases were sent, in two steps, to 20 Latin American surgeons who had to choose among six treatment options with and without the use of the MISDEF. Results For the conducts of decompression, decompression and short fusion, decompression and fusion with interbody device, and osteotomy with extension of fusion to the thoracic spine, no significant differences were found when comparing decisions made with and without MISDEF. For osteotomy, we observed a tendency for the number of surgeons choosing this conduct to increase when the decision is made with MISDEF. We observed that the number of surgeons who decided on conservative treatment decreased with the use of MISDEF (p <0.001). In cases with sagittal vertical axis <6 cm or pelvic tilt <25 ° or PI-LL (pelvic incidence minus lumbar lordosis) <10 ° or coronal curve <20 °, there was a decrease in the conservative treatment option and an increase in osteotomy with proximal extension of the fusion with the use of MISDEF. Conclusions There is a tendency to increase indications of osteotomy and decrease the conservative treatment option when making a decision with MISDEF. The use of the algorithm showed no significant impact on the therapeutic decision in severe cases of adult deformity. Level of Evidence II; Prospective comparative radiographic analysis.

How Does Ossification of Posterior Longitudinal Ligament Progress in Conservatively Managed Patients?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to elucidate the progression of ossification of the posterior longitudinal ligament (OPLL) in conservatively managed patients and determine its risk factors SUMMARY OF BACKGROUND DATA.: Although several studies have demonstrated how OPLL progresses after laminoplasty or fusion, its progression in conservatively managed patients remains unclear.

METHODS

The vertical length of the ossified mass and its thickness at each segment were evaluated on sagittal computed tomography images. Patients with vertical growth >2 mm were included in the vertical progression group. Segments with a thickness progression >1 mm were classified as thickness progressed segments, and patients who had at least one progressed segment were included in the thickness progression group. Based on the characteristics at each disc level, the ossified mass at each segment was classified into four types: type 1, no disc space involvement; type 2, involving the disc space, but not crossing; type 3, crossing the disc space, but not fused; and type 4, completely fused.

RESULTS

The progression of ossified mass was observed in younger patients (P < 0.01) and in C2-C3 involvement (P < 0.01) cases. Moreover, progression in both directions was observed more frequently in the mixed-type OPLL (P < 0.01). Progression occurred most often in type 3 segments (72.0%, P < 0.01). In type 3 segments, thickness progression was found more frequently in segments with segmental range of motion (ROM) ≥5° (55.6% vs. 27.8%, P = 0.04). The proportion of segments whose initial thickness was >5 mm was significantly higher among progressed segments (60.0% vs. 35.2%, P = 0.03).

CONCLUSION

Young age, C2-C3 involvement, and mixed-type OPLL are risk factors for OPLL progression. Segments with morphology of crossing the segment, but without fusion (type 3), segmental ROM ≥5°, and initial thickness >5 mm need special attention.

LEVEL OF EVIDENCE

3.

Progression of Ossification of the Posterior Longitudinal Ligament after Cervical Total Disc Replacement

Objective

Total disc replacement (TDR) is frequently performed anterior approaching method for the patients diagnosed with cervical disc herniation. This study aimed to assess the degree of ossification of the posterior longitudinal ligament (OPLL) progression after cervical TDR.

Methods

Twenty-two male soldiers who underwent cervical TDR surgery from 2009 to 2016 and were followed-up for more than 12 months were enrolled. The enrolled patients were classified as; 1) patients with pre-existing OPLL and without; and 2) patient showing progression of OPLL or not.

Results

Twenty-two men were included in the analysis. The mean follow-up period from the surgery was 41.4 months (range, 12–114 months). The mean age of all patients was 40.7 years (range, 31–52 years). TDR-only was used in 7 cases, and the hybrid surgery (TDR+ACDF) was used in 15 cases. The incidence of progression or newly development of OPLL was significantly higher in pre-existing OPLL group (p=0.01). In 11 cases showing the progression of the OPLL, the mean size of OPLL progression was 4.16 mm (range, 0.34–18.87 mm) in the longitudinal height and 1.57 mm (range, 0.54–3.91 mm) in thickness.

Conclusion

The progression of OPLL after cervical TDR was more frequent in patients with pre-existing OPLL than in patients without OPLL. Even though TDR is a major alternative to the treatment of cervical lesions to preserve vertebral segmental motion, careful attention should be paid to whether TDR should be used in patients with OPLL and this should be fully explained to the patient.

Progression of Cervical Ossification of Posterior Longitudinal Ligament After Laminoplasty or Laminectomy With Posterior Fixation

STUDY DESIGN

Retrospective case analysis.

OBJECTIVE

This study was conducted to investigate the course of ossification of the posterior longitudinal ligament (OPLL) progression after laminoplasty (LP) or laminectomy with posterior fixation (PF).

SUMMARY OF BACKGROUND DATA

LP is now recognized as a standard technique for the treatment of cervical multisegment OPLL; however, PF is beneficial for patients with severe stenosis. In recent years, there has been increasing interest in mechanical stress in OPLL, which is assumed to significantly impact progression.

METHODS

The progression of OPLL was assessed using midline sagittal computed tomography images of the cervical spine at various follow-up points. Radiographic parameters including the C2-C7 Cobb angle, C2-C7 range of motion (ROM), and adjacent cranial and caudal segmental ROMs were measured. Postoperative changes and differences between the LP and PF groups in the radiographic parameters were calculated to assess biomechanical stress. Logistic regression analysis was used to analyze the risk factors affecting the progression rate.

RESULTS

The authors included 14 PF and 36 LP patients, with a mean follow-up period of 28.9±20.8 and 37.6±16.8 months, respectively (P=0.069). After surgical treatment, both groups showed loss of cervical lordosis (9.2±6.9 vs. 5.3±8.2 degrees, P=0.220) and C2-C7 ROM (14.6± 13.5 vs. 13.1±12.2 degrees, P=0.861). The decrease of ROM in the cranial adjacent segment was larger in the LP group than in the PF group (0.7±4.1 vs. 1.4±5.5 degrees, P=0.453). The ROM in the caudal adjacent segment decreased in the LP group but increased in the PF group (-1.4±6.2 vs. 2.6±5.1 degrees, P=0.041). The progression rate was 2.15±1.31 mm/mo in the PF group and 1.53±1.04 mm/mo in the LP group (P=0.041). PF showed an odds ratio of 12.917 for a higher progression rate (95% confidence interval, 1.397-119.443; P=0.024).

CONCLUSION

The rate of progression of cervical OPLL was significantly higher after PF than after LP.Level III-a retrospective analysis.

Ossification of the Posterior Longitudinal Ligament: Surgical Approaches and Associated Complications

Ossification of the posterior longitudinal ligament (OPLL) is a rare but potentially devastating cause of degenerative cervical myelopathy (DCM). Decompressive surgery is the standard of care for OPLL and can be achieved through anterior, posterior, or combined approaches to the cervical spine. Surgical correction of OPLL via any approach is associated with higher rates of complications and the presence of OPLL is considered a significant risk factor for perioperative complications in DCM surgeries. Potential complications include dural tear (DT) and subsequent cerebrospinal fluid leak, C5 palsy, hematoma, hardware failure, surgical site infections, and other neurological deficits. Anterior approaches are technically more demanding and associated with higher rates of DT but offer greater access to ventral OPLL pathology. Posterior approaches are associated with lower rates of complications but may allow for continued disease progression. Therefore, the decision to pursue either an anterior or posterior approach to surgical decompression may be critically influenced by complications associated with each procedure. The authors critically review anterior and posterior approaches to surgical decompression of OPLL with particular focus on the complications associated with each approach. We also review the recent work in developing new surgical treatments for OPLL that aim to reduce complication incidence.

Does Ossification of the Posterior Longitudinal Ligament Progress After Fusion?

Starting in the 1960s, ossification of the posterior longitudinal ligament (OPLL) became more commonly diagnosed in Japan. The disease is characterized by a gradual increase in calcification of the posterior longitudinal ligament with the eventual sequelae of cervical canal stenosis and myelopathy. Surgical interventions to relieve stenosis and neurologic symptoms are performed to decompress the cervical canal. Studies demonstrate continued ossification of the OPLL in both nonsurgical and surgically treated patients. In this review, the authors evaluate the epidemiology, pathophysiology, and literature regarding disease progression in OPLL after cervical fusion.

Postoperative Progression of Cervical Ossification of Posterior Longitudinal Ligament: A Systematic Review

OBJECTIVE

The purpose of this study was to provide a systematic and comprehensive review of the existing literature regrading postoperative ossification of posterior longitudinal ligament (OPLL) progression.

METHODS

Using the PRISMA guidelines, we conducted an exhaustive review of electronic databases. Potential articles were screened and related information was extracted and analyzed. Twenty-four articles with low-quality evidence were included in the review. The findings of the literature review were divided into several groups: the relationship of surgery to OPLL progression; incidence and risk factors; timing and process of OPLL progression; the effect of additional instrumentation on progression; and neurologic deterioration related with progression.

RESULTS

There was no definitive conclusion for whether surgery could accelerate OPLL progression compared with the natural course. The incidence of postoperative OPLL progression was reported from 3.3% to 74.5%. Younger age, involvement of multiple levels and mixed or continuous types are recognized as risk factors. OPLL could progress transversely and longitudinally and progression in length appeared more significant than progression in thickness. Although radiologic OPLL progression was observed significantly more frequently after laminoplasty than after fusion surgery, whether additional instrumented fusion could suppress progression needs further research. Radiographic progression of OPLL did not positively correspond with neurologic deterioration.

CONCLUSIONS

The lack of high-level evidence makes it difficult to draw definite conclusions and further research and long-term follow-up clinical studies are needed to better understand postoperative OPLL progression.

Clinical Impact of Ossification of the Posterior Longitudinal Ligament Progression After Cervical Laminoplasty

STUDY DESIGN

This is a retrospective study.

OBJECTIVES

(1) To analyze the incidence of second surgery after initial laminoplasty for ossification of the posterior longitudinal ligament (OPLL) due to disease progression, (2) to examine factors associated with poor surgical outcome.

SUMMARY OF BACKGROUND DATA

Neurological deterioration after laminoplasty is frequently encountered due to OPLL progression.

PATIENTS AND METHODS

Of 201 OPLL patients treated by laminoplasty at a single-institution, the 153 monitored for >3 years postsurgery were included in this analysis. Neurological findings were graded by the Japanese Orthopaedic Association (JOA) score. We retrospectively examined the incidence of second surgery due to OPLL progression. We also evaluated the clinical characteristics and the surgical outcomes after second operation to identify potential risk factors for poor outcome.

RESULTS

Eight patients required a second surgery due to OPLL progression. Neurological recovery was achieved in 5 of these patients, whereas 3 exhibited continued dysfunction. Patients with poor recovery showed kyphotic changes of spinal alignment and high-intensity regions in the spinal cord on T2-weighted magnetic resonance images (T2-MRI).

CONCLUSIONS

Only a small fraction of OPLL patients required a second surgery due to OPLL progression. Recovery was poor in those with clear high-intensity T2-MRI signals in the spinal cord.

A Systematic Review of Classification Systems for Cervical Ossification of the Posterior Longitudinal Ligament

DESIGN

Systematic review.

OBJECTIVE

To conduct a systematic review to (1) summarize various classification systems used to describe cervical ossification of the posterior longitudinal ligament (OPLL) and (2) evaluate the diagnostic accuracy of various imaging modalities and the reliability of these classification systems.

METHODS

A search was performed to identify studies that used a classification system to categorize patients with OPLL. Furthermore, studies were included if they reported the diagnostic accuracy of various imaging modalities or the reliability of a classification system.

RESULTS

A total of 167 studies were deemed relevant. Five classification systems were developed based on X-ray: the 9-classification system (0.60%); continuous, segmental, mixed, localized or focal, circumscribed and others (92.81%); hook, staple, bridge, and total types (2.40%); distribution of OPLL (2.40%); and K-line classification (4.19%). Six methods were based on computed tomography scans: free-type, contiguous-type, and broken sign (0.60%); hill-, plateau-, square-, mushroom-, irregular-, or round-shaped (5.99%); rectangular, oval, triangular, or pedunculate (1.20%); centralized or laterally deviated (1.80%); plank-, spindle-, or rod-shaped (0.60%); and rule of nine (0.60%). Classification systems based on 3-dimensional computed tomography were bridging and nonbridging (1.20%) and flat, irregular, and localized (0.60%). A single classification system was based on magnetic resonance imaging: triangular, teardrop, or boomerang. Finally, a variation of methods was used to classify OPLL associated with the dura mater (4.19%).

CONCLUSIONS

The most common method of classification was that proposed by the Japanese Ministry of Health, Labour and Welfare. Other important methods include K-line (+/-), signs of dural ossification, and patterns of distribution.

Effect of posterior instrumented fusion on three-dimensional volumetric growth of cervical ossification of the posterior longitudinal ligament: a multiple regression analysis

BACKGROUND CONTEXT

Despite the fact that ossification of posterior longitudinal ligament (OPLL) is a three-dimensional disease, conventional studies have focused mainly on a two-dimensional measurement, and it is difficult to accurately determine the volume of OPLL growth and analyze the factors affecting OPLL growth after posterior decompression (laminoplasty or laminectomy and fusion).

PURPOSE

The present study aimed to investigate the factors affecting OPLL volume growth using a three-dimensional measurement.

STUDY DESIGN/SETTING

This was a retrospective case study.

PATIENT SAMPLE

Eighty-three patients with cervical OPLL who were diagnosed as having multilevel cervical OPLL of more than three levels on cervical computed tomography (CT) scans were retrospectively reviewed from June 1, 1998, to December 31, 2015.

OUTCOME MEASURES

The OPLL volume from the C1 vertebrae to the C7 vertebrae was measured on preoperative and the most recent follow-up CT scans.

METHODS

Eighty-three patients were retrospectively examined for age, gender, body mass index, hypertension, diabetes, type of OPLL, surgical method, preoperative cervical curvature, and preoperative and postoperative cervical range of motion. Preoperative cervical CT and the most recent follow-up cervical CT scans were converted to Digital Imaging and Communications in Medicine data, and the OPLL volume was three-dimensionally measured using the Mimics program (Materialise, Leuven, Belgium). The OPLL volume growth was analyzed using univariate and multivariate analyses.

RESULTS

The average follow-up period was 32.36 (±23.39) months. Patients' mean age was 54.92 (±8.21) years. In univariate analysis, younger age (p=.037) and laminoplasty (p=.012) were significantly associated with a higher mean annual growth rate of OPLL (%/y). In multivariate analysis, only laminoplasty (p=.027) was significantly associated with a higher mean annual growth rate of OPLL (%/y). The mean annual growth rate of OPLL was about seven times faster with laminoplasty (8.00±13.06%/y) than with laminectomy and fusion (1.16±9.23%/y).

CONCLUSIONS

Posterior instrumented fusion has the effect of reducing OPLL growth rate compared with motion-preserving laminoplasty. Patients' age and the surgical method need to be considered in surgically managing the multilevel OPLL.

Ossification of the posterior longitudinal ligament in the cervical spine: a review

Ossification of the posterior longitudinal ligament (OPLL) is a rare pathologic process of lamellar bone deposition that can result in spinal cord compression. While multiple genetic and environmental factors have been related to the development of OPLL, the pathophysiology remains poorly understood. Asymptomatic patients may be managed conservatively and patients with radiculopathy or myelopathy should be considered for surgical decompression. Multiple studies have demonstrated the morphology and size of the OPLL as well as the cervical alignment have significant implications for the appropriate surgical approach and technique. In this review, we aim to address all the available literature on the etiology, history, presentation, and management of OPLL in an effort to better understand OPLL and give our recommendations for the treatment of patients presenting with OPLL.

Rapid Progression of Ossification of the Posterior Longitudinal Ligament After Anterior Cervical Discectomy and Fusion

BACKGROUND

Ossification of the posterior longitudinal ligament (OPLL) has a reported incidence of 1.9%-4.3%. Disease progression is associated with surgery, with most studies focusing on OPLL progression after laminoplasty. The continued range of motion following surgery is believed to place strain on adjacent levels, driving calcification of the ligament. We present a case of marked progression of OPLL at levels adjacent to a previous anterior cervical discectomy and fusion.

CASE REPORT

A 59-year-old man initially presented for progressive loss of balance and dexterity and underwent a C4-6 anterior cervical discectomy and fusion procedure. Computed tomography performed 1 year postoperatively showed fusion across C4-6 with no evidence of OPLL at any level. Two years following index surgery, the patient reported right-side arm pain. Computed tomography revealed new minimal OPLL opposite the C3-4 level that was not causing cord compression. A sparing midline bilateral C3-7 laminotomy was performed to correct stenosis seen on magnetic resonance imaging. At 7 years after the index procedure, the patient presented with myelopathic symptoms exceeding symptoms at his index presentation. Computed tomography revealed marked progression of OPLL. The patient underwent C2-T2 posterior fusion with laminectomy from C2-C7 and responded well with gradual improvements in balance and arm pain after surgery.

CONCLUSIONS

Our report demonstrates that OPLL progression, which is largely reported following laminoplasty, may similarly occur following anterior cervical discectomy and fusion and supports the concept of motion-related OPLL progression.

Inter- and Intra-Observer Variability of the Volume of Cervical Ossification of the Posterior Longitudinal Ligament Using Medical Image Processing Software

Objective

Computed tomography (CT)-based method of three dimensional (3D) analysis (MIMICS^®, Materialise, Leuven, Belgium) is reported as very useful software for evaluation of OPLL, but its reliability and reproducibility are obscure. This study was conducted to evaluate the accuracy of MIMICS^® system, and inter- and intra-observer reliability in the measurement of OPLL.

Methods

Three neurosurgeons independently analyzed the randomly selected 10 OPLL cases with medical image processing software (MIMICS^®) which create 3D model with Digital Imaging and Communication in Medicine (DICOM) data from CT images after brief explanation was given to examiners before the image construction steps. To assess the reliability of inter- and intra-examiner intraclass correlation coefficient (ICC), 3 examiners measured 4 parameters (volume, length, width, and length) in 10 cases 2 times with 1-week interval.

Results

The inter-examiner ICCs among 3 examiners were 0.996 (95% confidence interval [CI], 0.987–0.999) for volume measurement, 0.973 (95% CI, 0.907–0.978) for thickness, 0.969 (95% CI, 0.895–0.993) for width, and 0.995 (95% CI, 0.983–0.999) for length. The intra-examiner ICCs were 0.994 (range, 0.991–0.996) for volume, 0.996 (range, 0.944–0.998) for length, 0.930 (range, 0.873–0.947) for width, and 0.987 (range, 0.985–0.995) for length.

Conclusion

The medical image processing software (MIMICS^®) provided detailed quantification OPLL volume with minimal error of inter- and intra-observer reliability in the measurement of OPLL.

Are There Differences in the Progression of Ossification of the Posterior Longitudinal Ligament Following Laminoplasty Versus Fusion?: A Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis of studies for the treatment of cervical myelopathy with ossification of the posterior longitudinal ligament (OPLL) treated with laminoplasty or fusion.

OBJECTIVE

To delineate whether OPLL continues to progress after laminoplasty compared with fusion and to clarify the relationship between radiological progression of OPLL and neurological decline.

SUMMARY OF BACKGROUND DATA

Laminoplasty is usually performed in patients with multilevel OPLL due to the surgical morbidity of anterior surgery. However, the disadvantage of laminoplasty is that the remaining OPLL can progress after the surgery.

METHODS

A literature search of PubMed, Embase, Web of Science, and the Cochrane library was performed to identify investigations concerning the progression of OPLL after laminoplasty or fusion. The pooled results were analyzed by calculating the effect size based on the event rate and the logit event rate.

RESULTS

We included data from 11 studies involving 530 patients, of whom 429 underwent laminoplasty and 101 underwent fusion surgery. The prevalence of radiological OPLL progression was 62.5% (95% confidence interval [CI] 55.3%-69.3%) for the laminoplasty group and 7.6% (95% CI 3.4%-15.9%) for the fusion group. The laminoplasty displayed substantially high prevalence of the progression of OPLL compared with the fusion group. In the laminoplasty group, the prevalence of OPLL progression increased with time and reached 60% at about 10-year follow-up. The prevalence for neurological decline was similar for about 2 years, 8.3% (95% CI 3.7%-17.9%) for the laminoplasty group and 3.8% (95% CI 1.3%-10.2%) for the fusion group.

CONCLUSION

Laminoplasty frequently induces progression of OPLL compared with fusion surgery, but does not make significant clinical deterioration. However, laminoplasty may not be recommended for OPLL patient because it can be getting worse with time.

LEVEL OF EVIDENCE

1.

Serum biomarkers in patients with ossification of the posterior longitudinal ligament (OPLL): Inflammation in OPLL

BACKGROUD

Ossification of the posterior longitudinal ligament (OPLL) is characterized by replacement of ligamentous tissue by ectopic new bone formation. OPLL causes narrowing of the spinal canal, resulting in neurological impairment. However, the pathogenesis of OPLL has not been fully elucidated. We investigated whether inflammation occurs in OPLL or not using high-sensitivity CRP (hs-CRP) in a case-control study.

METHODS AND FINDINGS

This study included 103 patients with OPLL in the patient group and 95 age- and sex-matched volunteers with degenerative spinal disease in the control group. Of the 103 OPLL patients, 88 patients who were available for more than 2 years follow-up were checked for OPLL progression. A blood sample was obtained and Hs-CRP, and other routine data, including total protein (TP), albumin (ALB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), glucose (Glu), calcium (Ca), inorganic phosphate (Pi), white blood cell count (WBC), hemoglobin (Hb) and platelet (PLT), were analyzed. The data were compared between the patients with OPLL and the controls. The severity of the ossified lesions in the whole spine were evaluated by the ossification index (OS index) in patients with OPLL. The data were also compared between the patients with OPLL progression (the progression group) and the patients without OPLL progression (the non-progression group). In the results, the mean hs-CRP in the OPLL group was higher than that in the controls. The Pi in the OPLL group was lower than that in the control group. A negative correlation was found between the Pi and the OS index. The mean hs-CRP in the progression group was higher than that in the non-progression group. There was a positive correlation between the average length of the OPLL progression per year and the hs-CRP.

CONCLUSIONS

The results may suggest the occurrence of local inflammation in OPLL and the inflammation might cause OPLL progression. These facts are important for understanding the pathology of OPLL.

Expansive open-door laminoplasty versus laminectomy and instrumented fusion for cases with cervical ossification of the posterior longitudinal ligament and straight lordosis

PURPOSE

To identify whether expansive open-door laminoplasty (Lam) is more appropriate than laminectomy and instrumented fusion (LIF) for cases with ossification of the posterior longitudinal ligament (OPLL) and straight cervical lordosis.

METHODS

A total of 67 cases were included and divided into Group Lam (n = 32) and Group LIF (n = 35), and the mean follow-up periods were 38 and 42 months, respectively. The cervical lordosis was elevated by C2-7 Cobb angle and cervical sagittal balance by C2-C7 sagittal vertical axis (SVA). Japanese Orthopedic Association (JOA), neurological recovery rate (RR) being calculated by the JOA, visual analog scale (VAS) and neck disability index (NDI) were used to assess clinical outcomes.

RESULTS

Differences in general data between two groups were not significant. Total blood loss and operation duration in Group Lam were both significantly less than that in the Group LIF. By the final follow-up, the cervical lordosis significantly decreased in Group Lam and increased in Group LIF, the SVA significantly increased in Group Lam and kept unchanged in Group LIF, and the JOA, VAS, NDI significantly improved in both groups. Although there was no significant difference in RR between the two groups, cases in Group Lam had significantly larger incidence of postoperative kyphosis and kyphotic change rate, and less VAS, NDI and incidence of axial pain than cases in Group LIF.

CONCLUSIONS

When compared with the LIF, the Lam is recommended for cases with OPLL and straight cervical lordosis when taking comparable neurological recovery, less axial pain and better neck function improvement into consideration.

Prevalence, Concomitance, and Distribution of Ossification of the Spinal Ligaments: Results of Whole Spine CT Scans in 1500 Japanese Patients

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To investigate the prevalence, concomitance, and distribution of various types of ossification of the spinal ligaments in healthy subjects using computed tomography (CT).

SUMMARY OF BACKGROUND DATA

CT has better diagnostic accuracy for ossification of the spinal ligaments compared to plain radiography. Currently there is no study that examines the prevalence of ossification of the spinal ligaments using whole spine CT scans.

METHODS

One thousand five hundred Japanese patients (888 men and 612 women) who underwent positron emission tomography and CT (PETCT) in a private health check center between 2006 and 2013 were included. This PETCT was performed on self-paying participants as a preventive cancer screen. Existence of ossification of the posterior longitudinal ligament (OPLL), ligamentum flavum (OLF), anterior longitudinal ligament (OALL), diffuse idiopathic skeletal hyperostosis (DISH), and nuchal ligament (ONL) was examined.

RESULTS

The prevalence of spinal ligament ossifications was found to be 6.3% in cervical OPLL (8.3% in men and 3.4% in women), 23% in ONL (33% in men and 8.8% in women), 1.6% in thoracic OPLL (1.4% in men and 2.0% in women), 12% in thoracic OLF (15% in men and 7.7% in women), 37% in thoracolumbar OALL (45% in men and 26% in women), and 12% in DISH (16% in men and 6.2% in women). Thirteen percent of patients with cervical OPLL had thoracic OPLL, 34% of cervical OPLL had thoracic OLF, 45% of cervical OPLL had ONL, and 36% of cervical OPLL had DISH. The most common level was C5 for cervical OPLL, T1/2 for thoracic OPLL, T11 for thoracic OLF, and T8/9 for OALL.

CONCLUSION

Accurate prevalence of various types of ossification of the spinal ligaments evaluated by CT was revealed. High concomitance was observed in each classification of spinal ligament ossification.

LEVEL OF EVIDENCE

3.

More Than 20 Years Follow-up After En Bloc Cervical Laminoplasty

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of the study was to evaluate clinical outcomes and to clarify the potential risks of cervical laminoplasty by a long-term follow-up of more than 20 years.

SUMMARY OF BACKGROUND DATA

There is no follow-up report exceeding 20 years after cervical laminoplasty.

METHODS

Two hundred sixteen patients underwent en bloc cervical laminoplasty for the treatment of cervical compressive myelopathy due to cervical spondylosis or ossification of the posterior longitudinal ligament between 1981 and 1994. Of these, 148 patients with a follow-up of more than 20 years were retrospectively studied (68 survived patients and 80 dead patients). The neurological evaluation was graded using Japanese Orthopaedic Association (JOA) score and the recovery rate. Neurological recovery was defined by the increase in JOA score. Radiological examinations were carried out using pre- and postoperative radiographs. As for the dead patients, the cause and age of death were reviewed.

RESULTS

The JOA score and recovery rate increased to 14.2 ± 2.7% and 64.9 ± 28.6%, respectively, at 5 years. The JOA score and recovery rate were maintained at 13.9 ± 3.2% and 61.6 ± 34.6% at 10 years. The JOA score decreased to 11.4 ± 5.1 at the last follow-up. In 32 out of 65 patients (49.2%), the JOA scores worsened mainly due to other spinal lesions. Cervical alignment became kyphotic when comparing preoperatively and at the last follow-up (ossification of the posterior longitudinal ligament: 15.7 ± 12.2° and 6.9 ± 17.8°, cervical spondylosis: 11.0 ± 8.9° and 3.3 ± 9.4°). Range of motion (ROM) decreased and one of the causes of ROM reduction was interlaminar fusion. The mean age at death was 78.2 years. The most frequent cause of death was malignant tumor.

CONCLUSION

Spine surgeons must be aware that patients have a long postoperative lifetime when cervical laminoplasty is performed. A long postoperative follow-up should be carried out after laminoplasty.

LEVEL OF EVIDENCE

4.

Association of miR-146a, miR-149, miR-196a2, and miR-499 Polymorphisms with Ossification of the Posterior Longitudinal Ligament of the Cervical Spine

Background

Ossification of the posterior longitudinal ligament (OPLL) of the spine is considered a multifactorial and polygenic disease. We aimed to investigate the association between four single nucleotide polymorphisms (SNPs) of pre-miRNAs [miR-146aC>G (rs2910164), miR-149T>C (rs2292832), miR-196a2T>C (rs11614913), and miR-499A>G (rs3746444)] and the risk of cervical OPLL in the Korean population.

Methods

The genotypic frequencies of these four SNPs were analyzed in 207 OPLL patients and 200 controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay.

Findings

For four SNPs in pre-miRNAs, no significant differences were found between OPLL patients and controls. However, subgroup analysis based on OPLL subgroup (continuous: continuous type plus mixed type, segmental: segmental and localized type) showed that miR-499GG genotype was associated with an increased risk of segmental type OPLL (adjusted odds ratio = 4.314 with 95% confidence interval: 1.109–16.78). In addition, some allele combinations (C-T-T-G, G-T-T-A, and G-T-C-G of miR-146a/-149/-196a2/-499) and combined genotypes (miR-149TC/miR-196a2TT) were associated with increased OPLL risk, whereas the G-T-T-G and G-C-C-G allele combinations were associated with decreased OPLL risk.

Conclusion

The results indicate that GG genotype of miR-499 is associated with significantly higher risks of OPLL in the segmental OPLL group. The miR-146a/-149/-196a2/-499 allele combinations may be a genetic risk factor for cervical OPLL in the Korean population.

Hybrid Decompression and Fixation Technique Versus Plated 3-Vertebra Corpectomy for 4-Segment Cervical Myelopathy: Analysis of 81 Cases With a Minimum 2-Year Follow-Up

STUDY DESIGN

A retrospective comparative study.

OBJECTIVE

The purpose of this study was to compare the stability and outcomes of a hybrid technique with those of a 3-vertebra corpectomy in the management of 4-segment cervical myelopathy.

SUMMARY OF BACKGROUND DATA

Patients with primarily ventral disease and loss of cervical lordosis are considered good candidates for anterior surgery. Cervical corpectomy is commonly performed in patients with multilevel cervical myelopathy. Corpectomies including >3 vertebraes entail an extremely high risk of reconstruction failure. To avoid the need to perform a 3-vertebra corpectomy, we use a hybrid decompression and fixation technique. This hybrid technique is a technique to obtain optimum decompression and fixation in patients with multilevel cervical myelopathy.

METHODS

A total of 81 patients with multilevel cervical myelopathy who underwent 4-segment cervical fixation with a minimum 2-year follow-up were included.

RESULTS

The hybrid technique involved combining a plated 2-vertebra corpectomy and single-level discectomy with stand-alone cage fixation. This technique was performed in 39 patients, and the plated 3-vertebra corpectomy was performed in 42 patients. Nine patients (21%) who underwent the plated 3-vertebra corpectomy were treated with halo immobilization, but no patient in the hybrid group required this treatment (P=0.002). There were fewer instances of reconstruction failure in the hybrid group than in the 3-vertebra corpectomy group (0% vs. 10%, respectively; P=0.048) and fewer instances of C5 palsy (3% vs. 17%, respectively; P <0.0001). The incidence of postoperative C5 palsy was 25% for C3-C5 corpectomy, 19% for C4-C6 corpectomy, and 11% for C4-C5 corpectomy+C6-C7 discectomy.

CONCLUSIONS

The hybrid technique has the following advantages over 3-vertebra corpectomy for 4-segment cervical fixation: a shorter graft bone and plate are required; the fixed segment has greater initial stability; postoperative external immobilization is simplified; and the risk of reconstruction failure and postoperative C5 palsy is reduced markedly.

Comparison of clinical outcomes in decompression and fusion versus decompression only in patients with ossification of the posterior longitudinal ligament: a meta-analysis

OBJECTIVE

Ossification of the posterior longitudinal ligament (OPLL) is a pathological calcification or ossification of the PLL, predominantly occurring in the cervical spine. Although surgery is often necessary for patients with symptomatic neurological deterioration, there remains controversy with regard to the optimal surgical treatment. In this systematic review and meta-analysis, the authors identified differences in complications and outcomes after anterior or posterior decompression and fusion versus after decompression alone for the treatment of cervical myelopathy due to OPLL.

METHODS

A MEDLINE, SCOPUS, and Web of Science search was performed for studies reporting complications and outcomes after decompression and fusion or after decompression alone for patients with OPLL. A meta-analysis was performed to calculate effect summary mean values, 95% CIs, Q statistics, and I2 values. Forest plots were constructed for each analysis group.

RESULTS

Of the 2630 retrieved articles, 32 met the inclusion criteria. There was no statistically significant difference in the incidence of excellent and good outcomes and of fair and poor outcomes between the decompression and fusion and the decompression-only cohorts. However, the decompression and fusion cohort had a statistically significantly higher recovery rate (63.2% vs 53.9%; p < 0.0001), a higher final Japanese Orthopaedic Association score (14.0 vs 13.5; p < 0.0001), and a lower incidence of OPLL progression (< 1% vs 6.3%; p < 0.0001) compared with the decompression-only cohort. There was no statistically significant difference in the incidence of complications between the 2 cohorts.

CONCLUSIONS

This study represents the only comprehensive review of outcomes and complications after decompression and fusion or after decompression alone for OPLL across a heterogeneous group of surgeons and patients. Based on these results, decompression and fusion is a superior surgical technique compared with posterior decompression alone in patients with OPLL. These results indicate that surgical decompression and fusion lead to a faster recovery, improved postoperative neurological functioning, and a lower incidence of OPLL progression compared with posterior decompression only. Furthermore, decompression and fusion did not lead to a greater incidence of complications compared with posterior decompression only.

Ossification of the Posterior Longitudinal Ligament: Etiology, Diagnosis, and Outcomes of Nonoperative and Operative Management

Study Design Narrative review. Objective To provide an overview on the diagnosis, natural history, and nonoperative and operative management of ossification of the posterior longitudinal ligament (OPLL). OPLL is a multifactorial condition caused by ectopic hyperostosis and calcification of the posterior longitudinal ligament. Familial inheritance and genetic factors have been implicated in the etiology of OPLL. The cervical spine is most commonly affected followed by the thoracic spine. The clinical manifestations range from asymptomatic to myelopathy or myeloradiculopathy. Methods Using PubMed, studies published prior to October 2014 with the keywords "OPLL, etiology"; "OPLL, genetics"; "OPLL, spinal cord injury"; "OPLL, natural history"; "OPLL, non-surgical management"; OPLL, surgical management"; "OPLL, surgical complications" were evaluated. Results The review addresses the etiology, epidemiology, classification, clinical presentation, imaging findings, and nonoperative and operative management of OPLL. Complications associated with surgical management of OPLL are also discussed. Conclusions OPLL commonly presents with myelopathy and radiculopathy. Spine providers should consider OPLL in their differential diagnosis and when reviewing images. If surgical intervention is pursued, imaging-based measurements and findings can help in choosing an anterior versus posterior surgical approach.

Single-door cervical laminoplasty using titanium miniplates alone

PURPOSE

To review outcome of 29 patients who underwent single-door cervical laminoplasty for myelopathy using titanium miniplates alone.

METHODS

Records of 20 men and 9 women aged 35 to 79 (mean, 64.3) years who underwent single-door cervical laminoplasty for myelopathy using titanium miniplates alone were reviewed. A total of 125 laminae were opened; 97 of them were fixed with a titanium miniplate. In 19 patients, a 20-hole titanium miniplate bent to the contour of a lamina was used and fixed into 3 laminae at alternate levels. In the remaining 10 patients, the pre-contoured ARCH Laminoplasty System was used and fixed into all laminae. In most patients, screw fixation was unicortical, and no spacer or bone graft was used.

RESULTS

The mean follow-up duration was 4 (range, 2-9) years. At one-year follow-up, the mean Japanese Orthopaedic Association (JOA) score improved from 9.2 to 13.2 (p<0.001). The mean JOA recovery rate was 64%. No patient had neurological deterioration. The mean anteroposterior diameter increased from 14.3 mm to 19.7 mm; the mean increase was 6.1 mm in the plated laminae and 5.3 mm in the unplated laminae (p=0.11). Out of the 125 laminae, there were 2 hinge non-unions in the unplated laminae, and 2 screw pullouts (not associated with plate loosening). No patient had penetration into the vertebral foramen or neuroforamen. Spring-back closure occurred in 5 (18%) of the 28 unplated laminae, with a mean of <3 mm loss of the initial expansion. Two patients developed transient C5 palsy presenting as shoulder abduction weakness. One patient had a delayed dural tear due to a sharp spike at the edge of the opened C6 lamina.

CONCLUSION

Single-door cervical laminoplasty using miniplates alone is a safe technique and achieves a high hinge union rate, good canal expansion, and neurological recovery.

Progressive relapse of ligamentum flavum ossification following decompressive surgery

Thoracic ossification of the ligamentum flavum (T-OLF) is a relatively rare spinal disorder that generally requires surgical intervention, due to its progressive nature and the poor response to conservative therapy. The prevalence of OLF has been reported at 3.8%-26%, which is similar to that of cervical ossification of the posterior longitudinal ligament (OPLL). The progression of OPLL after cervical laminoplasty for the treatment of OPLL is often shown in long-term follow-up. However, there have been no reports on the progression of OLF following surgery. We report a case of thoracic myelopathy secondary to the progressive relapse of OLF following laminectomy.

Anterior decompressive surgery after cervical laminoplasty in patients with ossification of the posterior longitudinal ligament

BACKGROUND CONTEXT

Two surgical procedures, posterior decompressive surgery (PDS) and anterior decompressive surgery (ADS), are the treatment options for cervical ossification of the posterior longitudinal ligament (OPLL). Each procedure has advantages and disadvantages. Cervical laminoplasty, a type of PDS, is relatively easy to perform and can be used for patients with multilevel cord compression. ADS can often be more technically demanding.

OBJECTIVE

The purpose of this study was to clarify the clinical characteristics and surgical results of the patients for whom ADS was necessary after PDS.

STUDY DESIGN

Retrospective study.

METHODS

A total of 144 patients, followed for more than 3 years after cervical laminoplasty, were included. The neurologic status was graded using the Japanese Orthopedic Association (JOA score). Eleven patients underwent ADS after PDS. The clinical background and surgical outcomes were evaluated. Radiological findings of the 11 patients requiring ADS after PDS (PA group) and the 133 PDS patients not requiring ADS (P group) were compared.

RESULTS

In the PA group, the JOA score was slightly deteriorated during follow-up after cervical laminoplasty. Severe pain in the unilateral upper extremity and deterioration of cervical myelopathy were the most typical symptoms necessitating ADS. The incidence of the mixed type of OPLL was significantly higher in this group. The JOA score improved in all patients after ADS as a second surgery.

CONCLUSIONS

In our strategy for the surgical treatment of cervical OPLL, PDS with laminoplasty remains as the initial treatment, and in patients with neurological deterioration and newly developed clinical symptoms during follow-up, ADS is considered as a salvage procedure.

Three-dimensional evaluation of volume change in ossification of the posterior longitudinal ligament of the cervical spine using computed tomography

BACKGROUND

Two-dimensional imaging is not adequate for evaluating ossification of the posterior longitudinal ligament (OPLL). This study was designed to evaluate the accuracy of a novel computed tomography (CT)-based three-dimensional (3D) analysis method that we had devised to measure volume changes in OPLL.

SUBJECTS AND METHODS

Twenty OPLL patients (12 male and 8 female; mean age 63.6 years) who were being followed conservatively were examined twice with an interval of at least 1 year between the two scans. The mean interval was 22 (range 12-45) months. A 3D model was created with DICOM data from CT images, using the MIMICS(®) software to calculate the volume. The mean ossification volume was determined from two measurements. Since ossification size varies widely, evaluation of change in volume is generally affected by the original size. Therefore, the change in ossification volume between the first and second CT examinations was calculated as the annual rate of progression.

RESULTS

The type of OPLL was classified as continuous in 3 patients, segmented in 3, and mixed in 14. The mean ossification volume was 1,831.68 mm(3) at the first examination and 1,928.31 mm(3) at the second, showing a significant mean increase in ossification volume. The mean annual rate of lesion increase was 3.33% (range 0.08-7.79%).

CONCLUSION

The 3D method used allowed detailed OPLL classification and quantification of change in the ossified volume. Thus, this method appears to be very useful for quantitative evaluation of OPLL with only minimal measurement error.

Interobserver and intraobserver reliability of the classification and diagnosis for ossification of the posterior longitudinal ligament of the cervical spine

PURPOSE

Ossification of the posterior longitudinal ligament (OPLL) of the cervical spine has been classified into four types by lateral plain radiographs, but the reliability of the classification and of the diagnosis of either cervical OPLL or cervical spondylotic myelopathy (CSM) was unknown. We investigated the interobserver and intraobserver reliability of the classification and diagnosis for OPLL by radiographs and computed tomography (CT) images.

METHODS

A total of 16 observers classified each patient's images into five groups; OPLL continuous, segmental, mixed, circumscribed type, or CSM. To evaluate interobserver reliability, the observers first classified only radiograph images, and next both radiographs and CT images. On another day they followed the same procedure to evaluate intraobserver reliability. We also evaluated interobserver and intraobserver reliability of the diagnosis of either cervical OPLL or CSM.

RESULTS

Interobserver reliability of the classification with radiographs only showed moderate agreement, but interobserver reliability with both radiographs and CT images showed substantial agreement. Intraobserver of reliability the classification was also improved by additional CT images. Interobserver reliability of the diagnosis with both radiographs and CT images was almost similar to with radiographs only. Intraobserver reliability of the diagnosis was improved by additional CT images.

CONCLUSIONS

This study suggested that the reliability of the classification and diagnosis for cervical OPLL was improved by additional CT images. We propose that diagnostic criteria for OPLL include both radiographs and CT images.

Does ossification of the posterior longitudinal ligament progress after laminoplasty? Radiographic and clinical evidence of ossification of the posterior longitudinal ligament lesion growth and the risk factors for late neurologic deterioration

Ossification of the posterior longitudinal ligament (OPLL) is a disease process characterized by progressive growth and calcification resulting in spinal canal compromise and serious neurological sequelae in advanced cases. Historically, OPLL has most commonly been treated with posterior surgical decompression. Although this procedure indirectly decompresses the spinal cord, it does not address the offending pathological entity, and further growth of the lesion may result in delayed neurological deterioration. This fact is particularly relevant because a number of long-term studies have revealed both longitudinal and transverse disease progression in individuals treated both surgically and conservatively. Despite these high rates of radiographically documented progression, however, the rate of neurological decline in patients undergoing posterior surgery with laminoplasty is low. In this article, the authors review the pathophysiology of OPLL, evidence of disease progression, and outcome data addressing conservative and surgical treatments.

Impact of spinopelvic alignment on decision making in deformity surgery in adults

Sagittal spinal misalignment (SSM) is an established cause of pain and disability. Treating physicians must be familiar with the radiographic findings consistent with SSM. Additionally, the restoration or maintenance of physiological sagittal spinal alignment after reconstructive spinal procedures is imperative to achieve good clinical outcomes. The C-7 plumb line (sagittal vertical axis) has traditionally been used to evaluate sagittal spinal alignment; however, recent data indicate that the measurement of spinopelvic parameters provides a more comprehensive assessment of sagittal spinal alignment. In this review the authors describe the proper analysis of spinopelvic alignment for surgical planning. Online videos supplement the text to better illustrate the key concepts.

Three-dimensional measurement of growth of ossification of the posterior longitudinal ligament

Object

Ossification of the posterior longitudinal ligament (OPLL) is a progressive disease that causes cervical myelopathy. Because 2D evaluation of ossification growth with plain lateral radiographs has limitations, the authors developed a unique technique to measure ossification progression and volume increase by using multidetector CT scanning.

Methods

The authors used serial thin-slice volume data obtained by multidetector CT scanning in 5 patients. The mean patient age was 63 years, and the mean follow-up duration was 3.1 years. First, a 3D model of OPLL was semiautomatically segmented at a specific threshold. Then, a preoperative model of OPLL was superimposed on a postoperative model using voxel-based registration of the vertebral bodies. Progression and volume increase were measured using a digital viewer that was developed by the authors. Progression was visualized using a color-coded contour on the surface of the OPLL model.

Results

All patients had progression of 0.5 mm or greater. The mean values concerning OPLL growth were as follows: maximum progression length, 4.7 mm; progression rate, 1.5 mm/year; volume increase, 1622 mm3; volume expansion rate, 37%; and volume increase rate, 484 mm3/year. The accuracy of superimposition by voxel-based registration, defined as closeness to the true value, was less than 0.31 mm. For intraobserver reproducibility of the volume measurement, the mean intraclass correlation coefficient, root mean square error, and coefficient of variation were 0.987, 16.0 mm3, and 1.7%, respectively.

Conclusions

Ossification of the posterior longitudinal ligament progresses even after surgery. Three-dimensional evaluation with the aid of CT scans is a useful and reliable method for assessing that growth.

Ossification of the posterior longitudinal ligament: pathogenesis, management, and current surgical approaches. A review

Ossification of the posterior longitudinal ligament (OPLL) is an important cause of cervical myelopathy that results from bony ossification of the cervical or thoracic posterior longitudinal ligament (PLL). It has been estimated that nearly 25% of patients with cervical myelopathy will have features of OPLL. Patients commonly present in their mid-40s or 50s with clinical evidence of myelopathy. On MR and CT imaging, this can be seen as areas of ossification that commonly coalesce behind the cervical vertebral bodies, leading to direct ventral compression of the cord. While MR imaging will commonly demonstrate associated changes in the soft tissue, CT scanning will better define areas of ossification. This can also provide the clinician with evidence of possible dural ossification. The surgical management of OPLL remains a challenge to spine surgeons. Surgical alternatives include anterior, posterior, or circumferential decompression and/or stabilization. Anterior cervical stabilization options include cervical corpectomy or multilevel anterior cervical corpectomy and fusion, while posterior stabilization approaches include instrumented or noninstrumented fusion or laminoplasty. Each of these approaches has distinct advantages and disadvantages. While anterior approaches may provide more direct decompression and best improve myelopathy scores, there is soft-tissue morbidity associated with the anterior approach. Posterior approaches, including laminectomy and fusion and laminoplasty, may be well tolerated in older patients. However, there often is associated axial neck pain and less improvement in myelopathy scores. In this review, the authors discuss the epidemiology, imaging findings, and clinical presentation of OPLL. The authors additionally discuss the merits of the different surgical techniques in the management of this challenging disease.

Evaluation of ossification of the posterior longitudinal ligament by three-dimensional computed tomography and magnetic resonance imaging

BACKGROUND CONTEXT

Detection of ossification of the posterior longitudinal ligament (OPLL) of lesions by lateral radiography is sometimes difficult because the lesions are small. Three-dimensional computed tomography (3D CT) imaging has made it possible to detect lesions not been seen by lateral radiography.

PURPOSE

To evaluate the use of 3D CT in visualizing and classifying OPLL, and the added value of magnetic resonance imaging (MRI) in determining spinal cord compression.

STUDY DESIGN

Prospective case study in an academic department of orthopedic surgery.

PATIENT SAMPLE

Patients with OPLL diagnosed by lateral radiography of the cervical spine from April 2006 to March 2007 were identified.

METHODS

Ossification of the posterior longitudinal ligament visualized lateral radiography was classified according to the existing scheme as continuous, segmental, mixed, or other type. Ossification of the posterior longitudinal ligament visualized by 3D CT was organized into a classification system comprising flat, irregular, or localized types and were compared with the lateral radiographic images. Magnetic resonance imaging was done to determine the extent of spinal cord compression.

RESULTS

All 55 patients (35 men and 20 women; median age, 66 years) with OPLL were enrolled. Of these, 41 (75%) had a type of OPLL as visualized by 3D CT that corresponded with only one type of OPLL as visualized by lateral radiography. In 39 (71%) of 55, the areas of the ossified lesions visualized by 3D CT were the same as those visualized by lateral radiography. In the other 16, the lesions were either too small or too unclear to be visualized by lateral radiography. In all cases, 3D CT imaging showed that the transverse width of OPLL was within the bilateral Luschka joints, which was not noted by lateral radiography. In 13 of the 14 subjects who underwent MRI, spinal cord compression was noted at the superior or inferior edges of the ossified lesions that had been seen by 3D CT.

CONCLUSIONS

Three-dimensional computed tomography visualization of OPLL provided the basis of a classification system, superior to lateral radiography, and provided new information about OPLL. Combining 3D CT with MRI might be useful to provide details about spinal cord compression in OPLL.

Ossification of the posterior longitudinal ligament: a review

Ossification of the posterior longitudinal ligament (OPLL) is most commonly found in men, the elderly, and Asian patients. There are many diseases associated with OPLL, such as diffuse idiopathic skeletal hyperostosis, ankylosing spondylitis, and other spondyloarthropathies. Several factors have been reported to be associated with OPLL formation and progression, including genetic, hormonal, environmental, and lifestyle factors. However, the pathogenesis of OPLL is still unclear. Most symptomatic patients with OPLL present with neurological deficits such as myelopathy, radiculopathy, and/or bowel and bladder symptoms. There are some reports of asymptomatic OPLL. Both static and dynamic factors are related to the development of myelopathy. Plain radiography, CT, and MR imaging are used to evaluate OPLL extension and the area of spinal cord compression. Management of OPLL continues to be controversial. Each surgical technique has some advantages and disadvantages, and the choice of operation should be made case by case, depending on the patient's condition, level of pathology, type of OPLL, and the surgeon's experience. In this paper, the authors attempt to review the incidence, pathology, pathogenesis, natural history, clinical presentation, classification, radiological evaluation, and management of OPLL.

Long-term results of double-door laminoplasty using hydroxyapatite spacers in patients with compressive cervical myelopathy

No previous studies have reported 10-year follow-up results for double-door laminoplasty using hydroxyapatite (HA) spacers. The purpose of this study was therefore to explore the long-term results of double-door laminoplasty using HA spacers and to determine if non-union or breakage of HA spacers is related to restenosis of the enlarged cervical canal. The study group consisted of 68 patients with a minimum of 10 years of follow-up after double-door laminoplasty using HA spacers. The average postoperative Japanese Orthopaedic Association score improved significantly after surgery and was maintained until the final follow-up. The average range of motion decreased by 42.6% in patients with cervical spondylotic myelopathy (CSM) and 65.8% in patients with ossification of the posterior longitudinal ligament (OPLL). The enlarged cervical canal area was preserved almost until the final follow-up. The average non-union rates of HA spacers were 21% in CSM and 17% in OPLL, and the average breakage rates were 24 in CSM and 21% in OPLL at the final follow-up. Although non-union and breakage of HA spacers were common, neither of these factors were correlated with restenosis of the enlarged cervical canal.