Morphologic evaluation and surgical simulation of ossification of the posterior longitudinal ligament using helical computed tomography with three-dimensional and multiplanar reconstruction

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.

Morphometric measurement of the cervical spine for minimally invasive pedicle screw fixation using reverse engineering and three-dimensional reconstruction

BACKGROUND

Percutaneous cervical pedicle screw fixation has been proven to be an effective method of cervical screw instrumentation, which has the advantages of less invasiveness and low blood loss. Emerging evidence has indicated that the cervical spinous process plays an important role in percutaneous spine surgery. However, there is a limited amount of information on the fundamental research of pedicle and its associated imaging parameter measurement. The purpose of this study was to measure the anatomic data of the pedicle screw channel (PSC) using reverse engineering and three-dimensional reconstruction, and also to discuss the three-dimensional relationship between the cervical spinous process and the pedicle screw channel.

METHODS

Twenty adult subjects (10 males, 10 females, age range 19-46 years) were studied using the method of three-dimensional CT reconstruction and reverse engineering. The centrum was divided into 10 equal parts from front to back. The bisectors were defined as borderline depths of the centrum, from front to back, 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 0% of borderline depths were presented. Then, a 3D coordinate system was constructed to measure all the data, including the radius of the inscribed circle, the length of the PSC, the insertion angle, the distances from entry point to cervical spinous process and skin depth. All the indexes were measured from 70% to 90% borderline depth.

RESULTS

The radius of the inscribed circles from C₃ to C₇ at 90% borderline depth were 2.94 ± 0.55 mm, 3.04 ± 0.40 mm, 3.15 ± 0.36 mm, 3.28 ± 0.47 mm, 3.89 ± 0.54 mm, respectively. The lengths of the PSC were between 25 and 32 mm. The insertion angles for 70% to 90% borderline depth were 28.33°, 34.28°, 37.92°, respectively. The relationship between the PSC and spinous process was measured as the distance from the entry point to the end of the spinous process, which were, respectively, 26.91 mm, 28.18 mm, 30.03 mm, 35.67 mm, 41.99 mm from C₃ to C₇ .The distance from the skin to the entry point of C_3-7 increased gradually.

CONCLUSIONS

The measurements of this study could provide detailed information for percutaneous cervical screw fixation. The data of the relationship between the cervical spinous process and the pedicle screw channel present valuable technical information for the design, optimization and clinical application of the aiming device for percutaneous cervical pedicle screw fixation. Copyright © 2016 John Wiley & Sons, Ltd.

Increased bone mineral density and decreased prevalence of osteoporosis in cervical ossification of the posterior longitudinal ligament: a case-control study

Bone and mineral metabolism has been reported to affect the development of the ossification of the posterior longitudinal ligament (OPLL). The aim of this study was to compare bone mineral densities (BMD) and rate of osteoporosis between cervical OPLL and a matched control group. We also investigated the correlation of BMD with the number of cervical spine levels involved with OPLL. From 1999 to August 2011, 178 patients with cervical OPLL underwent dual-energy X-ray absorptiometry (DXA) at our institute. The control group was age-, sex-, and body mass index (BMI)-matched with the OPLL group on a 1:1 basis. BMD was measured at the lumbar spine (L1-L4), femoral neck, and total femur using DXA. Age, sex, and BMI were the same in the OPLL and control groups. BMDs of the OPLL and control groups were significantly different in the lumbar spine, femoral neck, and total femur (p = 0.0001, 0.0001, 0.009, respectively). Rates of osteopenia and osteoporosis were lower in the OPLL than in the control group according to lumbar spine and femoral neck DXA (p = 0.01, 0.03, respectively). A positive correlation was observed between lumbar spine BMD and the number of cervical spine levels involved with OPLL (p = 0.004).

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 posterior longitudinal ligaments: evaluation with MRI

Ossification of the posterior longitudinal ligament is a special subcategory of degenerative disease responsible for compression of the spinal cord. On MR images, T2-weighted sequences are the most effective to evaluate both spinal cord compression due to the ossification and abnormal signal intensity of the cord. Although ossification of the ligaments is well demonstrated on CT and plain radiographs, MRI noninvasively provides useful information about the degree and extent of spinal cord compression, as well as the character of the ossification.