Identification of ossification of the posterior longitudinal ligament extending through the dura on preoperative computed tomographic examinations of the cervical spine

A novel computed tomography scoring system for evaluating the risk of dural defects in anterior surgery for cervical ossification of the posterior longitudinal ligament

OBJECTIVE

To develop and validate a computed tomography (CT)-based scoring system for evaluating the risk of dural defects (DDs) in anterior surgery for cervical ossification of the posterior longitudinal ligament (OPLL).

METHODS

We retrospectively analyzed CT imaging features of 114 OPLL patients in our institute who received anterior decompression surgery. Intraoperative DDs were found in 16 patients. A multivariable logistic regression was used to evaluate the predictors. According to the odd ratio of the included risk factors, we developed a CT scoring system for evaluating the risk of DDs in anterior OPLL surgery. The system was further validated in an independent group of 39 OPLL patients.

RESULTS

We developed a CT scoring system as follows: hook sign (2 points), K-line (-) (1 point) and broad base (1 point). Thus, the system comprised 4 total points, and patients were at high risks of dural defects when the score ≥3 points. The operating characteristics of a score ≥3 for predicting DDs in the validation group were: sensitivity of 0.83, specificity of 0.94, LR positive of 13.75, LR negative of 0.18 and AUC of 0.886. The discriminatory ability of the proposed score could be demonstrated in the validation cohort.

CONCLUSIONS

The relatively simple and easy-to-use scoring system we propose integrates the 3 most reliable spinal CT findings observed in patients with OPLL and a DD. The likelihood to identify the underlying risks of spinal CSF leaks may be useful to triage patients who may benefit from indirect decompression techniques.

Giant calcified thoracic disk herniations: ossification of PLL or autonomous entity?

BACKGROUND

Giant calcified thoracic disk herniation (GCTD) is an uncommon event, which requires surgical treatment in less than 1% of patients. GCDTs are a specific subgroup of herniated thoracic disks occupying more than 40% of the spinal canal showing calcifications associated with a certain degree of ossification. In this paper, we are reporting our whole experience in the surgical management of GCTDs through anterior approaches. We believe that they present characteristics that associate them to the circumscribed type of ossified posterior longitudinal ligament (OPLL) with a possible common pathophysiology consisting in the dural violation.

METHODS

Twenty-three consecutive patients with GCDTs were managed through anterior approaches during the period 1996-2019 at the Niguarda Hospital, Milan, Italy. Clinical data, radiological features, surgical reports, histological findings, and outcomes were reviewed.

RESULTS

There was no mortality, whereas permanent morbidity consisted of 1 case of worsened paraparesis due to accidental spinal cord contusion. One patient required reoperation to repair a postoperative cerebrospinal fluid (CSF) leakage. All patients underwent postoperative MRI which showed excellent decompression of cord and dural sac in all cases. Histological study of en-bloc removed GCTD showed typical calcification patterns of the PLL.

CONCLUSIONS

GCDTs may be assimilated to the so-called "circumscribed type" of OPLL. The GCDTs may show the same radiological CT and MRI pattern of OPLL. The anterior accesses now represent the standard of care for GCTDs. The use of operative microscope and intraoperative monitoring is mandatory. The risk of CSF leakage can be markedly reduced by meticulous reconstruction of the dura and the placement of spinal drainage. Adequate exposition may sometimes require one or two levels of corpectomy with consequent vertebral body reconstruction and fixation of anterior column of the spine.

Surgical Management of Cervical Ossification of Posterior Longitudinal Ligament: The Treatment Algorithm and Outcome

Introduction Managing patients who present with symptoms of cervical myelopathy secondary to cervical ossification of the posterior longitudinal ligament (OPLL) is challenging. Various factors such as the number of levels involved with OPLL, types of OPLL, canal occupying ratio, K-line characteristics, and C2-C7 lordosis angle were found to guide decision-making and surgical approaches in managing this condition. However, no clear treatment algorithm has been published. This study aims to investigate the outcome of the management of cervical OPLL using a treatment algorithm used in a tertiary university hospital. Methods This is a retrospective cross-sectional study. Patients with cervical myelopathy secondary to cervical OPLL who were treated surgically in our center from 2014 to 2020 were included in this study. Demographic data and preoperative parameters that determined the treatment given according to our treatment algorithm were analyzed. Result A total of 24 patients fit the inclusion and exclusion criteria of the study. The mean recovery rate for all groups is 61.8[Formula: see text]21.9% and the mean postoperative neck disability index (NDI) is 17.83[Formula: see text]16.67%. There was a statistically significant difference between preoperative and postoperative Japanese Orthopaedic Association (JOA) scores for both anterior and posterior surgery subgroups. Conclusion We believe that the treatment algorithm used in our center could benefit other surgeons as a guide in managing patients who suffer from cervical myelopathy secondary to cervical OPLL. Further study including newer techniques would increase the surgeon's arsenal in providing the best outcome in managing this condition.

Medicolegal corner (spine): Contraindicated use of DuraSeal in anterior cervical spine led to quadriplegia

Background:

The package insert for DuraSeal (Integra LifeSciences, Princeton NJ) states it is Contraindicated for use in the anterior cervical spine (confined space): “Do not apply DuraSeal® hydrogel to confined bony structures where nerves are present since neural compression may result due to hydrogel swelling (…up to 12% of its size in any direction).” Further, it should not be used to treat massive unrepaired cerebrospinal fluid (CSF) leaks in any location; “…(it) is indicated as an adjunct to sutured dural repair during spine surgery to provide watertight closure,” but it is not to be used “...for a gap greater than 2 mm….”

Methods:

A spinal surgeon interpreted a geriatric patient’s MR as showing severe C3-C4 to C5-C6 anterior cord compression due to disc disease/spondylosis. However, he never reviewed the CT report/images that documented marked ossification of the posterior longitudinal ligament (OPLL) with multiple signs of dural penetrance.

Results:

The anterior C4, C5 corpectomy, and C3-C6 strut fusion/plating resulted in a massive, irreparable cerebrospinal fluid (CSF) leak. Despite the contraindications, the surgeon mistakenly applied DuraSeal which caused the patient’s postoperative quadriplegia (i.e., as documented on the delayed postoperative MR scan). Following a secondary surgery consisting of a laminectomy/posterior fusion, the patient was still quadriplegic. Further, as he requested no postoperative MR scan and performed no subsequent corrective surgery (i.e., anterior removal of DuraSeal), the patient remained permanently quadriplegic.

Conclusion:

DuraSeal is directly contraindicated for use in the anterior cervical spine, with/without a CSF leak. Here, utilizing DuraSeal for anterior cervical OPLL surgery resulted in permanent quadriplegia, and was below the standard of care.

The role of cerebrospinal fluid cross-section area ratio in the prediction of dural ossification and clinical outcomes in patients with thoracic ossification of ligamentum flavum

Background

It is imperative to preoperatively distinguish dural ossification (DO) and thus anticipate the risks and outcome of the surgery for patients with ossification of ligamentum flavum (OLF). However, studies have disagreed as to the efficacy of the radiographic signs or factors to predict DO and surgical outcome. In additon, the association between the cerebrospinal fluid cross-section area ratio (CCAR) and DO or clinical outcome had not been reported. The purpose of this study was to analyse CCAR and its role in prediction of DO and neurological function recovery rate in patients with OLF.

Methods

Fifty-two consecutive patients with OLF, who underwent posterior thoracic decompression and fusion between September 2012 and March 2019 at a single institution, were retrospectively reviewed. Demographic data, radiographic signs of DO, CCAR, pre- and postoperative modified Japanese Orthopedic Association (mJOA) score were recorded.

Results

There were 27 patients in the DO group and 25 patients in the non-DO group, with a mean age at surgery of 57.4 years and 53.9 years, respectively. No significant differences were found in sex, age, segment of maximum compression and preoperative mJOA score between the two groups. The receiver operating characteristic curve showed that the value of CCAR had a relatively high value for diagnosis of DO and prediction of neurological function recovery rate (P = .000). According to the value of CCAR, three zones were defined as DO zone (≤14.3%), non-DO zone (≥44.5%), and gray zone (14.3 to 44.5%). When the value of CCAR≤14.3%, the recovery rate was poor or fair, while it had good or excellent recovery when CCAR≥45.2%.

Conclusion

The value of CCAR had a high diagnostic value for prediction of DO and neurological function recovery rate in patients with OLF.

Review of Radiological Parameters, Imaging Characteristics, and Their Effect on Optimal Treatment Approaches and Surgical Outcomes for Cervical Ossification of the Posterior Longitudinal Ligament

Determining the optimal surgical method for cervical ossification of the posterior longitudinal ligament (OPLL) is challenging. The surgical indication should be made based on not only radiological findings, but also the patient’s age, preoperative neurological findings, social background, activities of daily life, and the presence or absence of comorbid diseases. Anterior resection for OPLL with or without wide corpectomy and fusion, posterior decompression with or without relatively long fusion, or anterior and posterior combined surgery may be considered. When evaluating the clinical condition of patients with cervical OPLL before surgery, various radiological parameters should be carefully considered, including the number of spinal segments involved, the cervical alignment or tilt angle, the relationship between OPLL and the C2–7 line (termed the “K-line”), the occupying ratio of OPLL, and the involvement of dural ossification. The objective of this article is to review the radiological parameters in current use for deciding upon the optimal surgical strategy and for predicting surgical outcomes, focusing on cervical OPLL.

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.

Clinical relation among dural adhesion, dural ossification, and dural laceration in the removal of ossification of the ligamentum flavum

BACKGROUND CONTEXT

Dural laceration frequently occurs during surgery in patients with ossification of the ligamentum flavum (OLF), mainly because of dural adhesion (DA) and dural ossification (DO) between the ligamentum flavum and the dura mater. However, the radiological predictive factors of DA in OLF have rarely been reported.

PURPOSE

The objective of this study was to determine the preoperative radiological signs for predicting intraoperative DA in OLF by using preoperative magnetic resonance imaging (MRI) and computed tomography (CT).

STUDY DESIGN

This is a retrospective study.

PATIENT SAMPLE

This study included 182 patients who underwent decompressive laminectomy and OLF removal from 2005 to 2014.

OUTCOME MEASURE

Demographic data, preoperative neurologic status, surgical procedure and results, and intraoperative and postoperative complications were analyzed. Clinical outcome was assessed with the Japanese Orthopaedic Association score.

MATERIALS AND METHODS

Depending on the morphologic appearance of OLF in preoperative radiographs, we aimed to investigate the prevalence of intraoperative DA and DO. We used the following factors of representative classifications: (1) surface appearance, (2) "double-layer" or "tram-track" sign, (3) cross-sectional area of the stenosed level, (4) Sato classification as axial classification, (5) Kuh classification as sagittal classification, and (6) high-signal-intensity change on T₂-weighted MRI.

RESULTS

Intraoperative evidence of DA was observed in 52 patients (29%), and DO was observed in 23 patients (13%). Twenty-seven patients (15%) had dural laceration during surgery. Statistically, DA was closely associated with the non-uniform type of surface appearance (odds ratio 5.396, p=.001) and with the presence of either a double-layer sign or a tram-track sign (odds ratio 11.525, p<.001). In the preoperative CT and MRI, 21 out of 23 patients with DO showed a "double-layer sign" or a "tram-track sign."

CONCLUSIONS

This study identified two predictive factors of DA in OLF, which were the non-uniform surface appearance and the presence of a double-layer sign or a tram-track sign. The presence of DO in OLF was closely associated with a double-layer sign or a tram-track sign in the preoperative radiological images.

Risk Factors and Management of Dural Defects in Anterior Surgery for Cervical Ossification of the Posterior Longitudinal Ligament

OBJECTIVE

To investigate risk factors and outcomes and to develop a cogent perioperative management algorithm for dural defects (DDs) in anterior surgery for cervical ossification of the posterior longitudinal ligament (OPLL).

METHODS

Ninety OPLL patients who had undergone anterior cervical decompression between January 2014 and December 2016 were reviewed. DDs occurred in 12 patients. Demographic, clinical, and radiologic data; intraoperative and postoperative management; and complications were analyzed. Risk factors for DDs were assessed with multivariate analysis. A treatment algorithm was identified based on these findings and our experience.

RESULTS

The prevalence of DDs was 13.3% (12/90). Univariate and multivariate analyses showed that the ratio of OPLL base to spinal canal (odds ratio [OR] 1.09, P = 0.012), kyphotic cervical alignment with thick OPLL masses (OR 9.44, P = 0.026), and lateral, curved, and irregular OPLL masses (OR 8.28, P = 0.037) could be risk factors for DDs. DDs were repaired intraoperatively with onlay grafts, and lumbar drains were placed in all DD patients. The treatment was successful in all DD patients, and outcome measures did not differ between the DD and no DD groups. No patient had experienced complications associated with DDs and CSF leaks at the final follow-up visit.

CONCLUSIONS

Patients with broad-based OPLL, kyphotic cervical alignment with thick OPLL masses, and lateral, curved, and irregular OPLL masses have a higher risk of DD in anterior surgery for OPLL. Intraoperative primary repair with onlay grafts combined with early lumbar drains is a simple, safe, and effective strategy for DDs. The outlook for the long-term sequelae of DDs is optimistic if they are managed adequately.

Radiologic Evaluation of Ossification of the Posterior Longitudinal Ligament with Dural Ossification

There are 3 basic radiological patterns of dural ossification (DO). Although double-layer DO is most common, when examining neuroimaging of ossification of the posterior longitudinal ligament (OPLL), isolated DO or masse DO should be kept in mind. Bone window computed tomography (CT) is most sufficient in identifying any type of DO associated with OPLL. Sagittal reformation of CT has replaced polytomography. MRI is not optimal for identification of DO and OPLL. Surgical approaches should be determined based on this important radiological information to avoid an unexpected complication. Expansive laminoplasty is the procedure of choice when DO is predominant.

Imaging grading system for the diagnosis of dural ossification based on 102 segments of TOLF CT bone-window data

Thoracic ossification of the ligamentum flavum (TOLF) complicated with dural ossification (DO) is a severe clinical disease. The diagnosis of DO preoperatively remains challenging. The current study retrospectively analyzed imaging features of 102 segments with TOLF from 39 patients and proposed a grading system for evaluating DO risk. Logistic regression results showed that unilateral spinal canal occupational rate (UCOR), tram track signs, and C-signs were all risk factors for DO (odds ratios of 5.393, 19.734 and 72.594, respectively). In validation analyses for the TOLF-DO grading system, sensitivity was 76.0% (19/25), specificity was 91.0% (70/77), and Youden’s index was 0.66. Thus, implementation of the TOLF-DO grading system has the potential to improve the diagnosis of DO.

Anterior longitudinal decompression in the management of severe ossification of the posterior longitudinal ligament in the cervical spine

The advantages of anterior surgery for severe ossification of the posterior longitudinal ligament in the cervical spine have been reported. However, it is more technically demanding and associated with a high risk of surgery-related complications. The purpose of this study was to evaluate the feasibility of longitudinal decompression techniques in anterior surgery for severe ossification of the posterior longitudinal ligament in the cervical spine. Between June 2008 and December 2011, twenty-two patients (16 men and 6 women; average age, 58 years [range, 45-72 years]) who underwent anterior corpectomy and fusion for severe ossification of the posterior longitudinal ligament were studied retrospectively. The clinical efficacy, canal narrowing ratio, fused segment height, and complications were investigated. After a mean 25.4-month follow-up, mean Japanese Orthopaedic Association score increased from 8.8±1.4 preoperatively to 14.0±1.2 at final follow-up (P<.05), an improvement rate of 63.5%±12.5%. Mean canal narrowing ratio decreased from 62.0%±6.0% preoperatively to 8.2%±4.9% postoperatively (P<.05). Mean fused segment height increased 2.3±0.5 mm from pre- to postoperatively and decreased 2.8±0.4 mm from postoperatively to final follow-up (P>.05). Five patients developed cerebrospinal fluid leakage, and 1 patient experienced hematoma. No instrument failure was observed, and all patients had successful fusion. Anterior longitudinal decompression is a relatively effective procedure in the management of severe ossification of the posterior longitudinal ligament in the cervical spine. It can be applied to treat closed-base ossification of the posterior longitudinal ligament (defined as no space between the lateral margin of the ossified base and the spinal canal lateral wall), but it is associated with a high risk of cerebrospinal fluid leakage.

What you need to know about ossification of the posterior longitudinal ligament to optimize cervical spine surgery: A review

What are the risks, benefits, alternatives, and pitfalls for operating on cervical ossification of the posterior longitudinal ligament (OPLL)? To successfully diagnose OPLL, it is important to obtain Magnetic Resonance Images (MR). These studies, particularly the T2 weighted images, provide the best soft-tissue documentation of cord/root compression and intrinsic cord abnormalities (e.g. edema vs. myelomalacia) on sagittal, axial, and coronal views. Obtaining Computed Tomographic (CT) scans is also critical as they best demonstrate early OPLL, or hypertrophied posterior longitudinal ligament (HPLL: hypo-isodense with punctate ossification) or classic (frankly ossified) OPLL (hyperdense). Furthermore, CT scans reveal the "single layer" and "double layer" signs indicative of OPLL penetrating the dura. Documenting the full extent of OPLL with both MR and CT dictates whether anterior, posterior, or circumferential surgery is warranted. An adequate cervical lordosis allows for posterior cervical approaches (e.g. lamionplasty, laminectomy/fusion), which may facilitate addressing multiple levels while avoiding the risks of anterior procedures. However, without lordosis and with significant kyphosis, anterior surgery may be indicated. Rarely, this requires single/multilevel anterior cervical diskectomy/fusion (ACDF), as this approach typically fails to address retrovertebral OPLL; single or multilevel corpectomies are usually warranted. In short, successful OPLL surgery relies on careful patient selection (e.g. assess comorbidities), accurate MR/CT documentation of OPLL, and limiting the pros, cons, and complications of these complex procedures by choosing the optimal surgical approach. Performing OPLL surgery requires stringent anesthetic (awake intubation/positioning) and also the following intraoperative monitoring protocols: Somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), and electromyography (EMG).

Cerebrospinal fluid leakage during anterior approach cervical spine surgery for severe ossification of the posterior longitudinal ligament: prevention and treatment

OBJECTIVE

The prevention and treatment of the common complication of cerebrospinal fluid leakage (CSFL) during anterior approach cervical spine surgery for severe ossification of the posterior longitudinal ligament (OPLL) is documented.

METHOD

A retrospective analysis of 47 patients with severe cervical OPLL aged 39 to 73 years (average, 56.4 years) who underwent anterior operations was conducted. All patients were classified as local or segmental types based on the thickness of the ossified mass (>5 mm) and canal stenosis rates exceeding 50%. Fifteen cases underwent discectomy and fusion and 32 cases corpectomy and fusion. Preoperative CT images were analyzed for operation breakthrough and decompression range. During surgery, the ossified mass was excised or floated and the arachnoid reserved in order to reduce dural damage. Sutures coupled with gelatin sponge or muscle pedicle were applied to repair dural defects. After surgery, patients were confined to bed to allow for drainage or puncture.

RESULTS

Fifteen cases of dural defects were recognized intraoperatively. Postoperatively, 5 patients developed CSFL. Partially cut dura with intact arachnoid occurred in one patient who developed a CSF pseudocyst. No cases required secondary operations or shunt placement and all exhibited good wound healing, with JOA scores increasing from 7.30 ± 1.08 to 13.70 ± 0.81 points and improvement rates of 65.98% ± 7.35%.

CONCLUSION

During anterior surgical treatment for severe OPLL, CSFL can be prevented and treated through careful analysis of CT images, meticulous operative technique, careful handling of the ossified mass, and intra-operative repair of dural damage.

Imaging of spinal stenosis: neurogenic intermittent claudication and cervical spondylotic myelopathy

Spinal stenosis in either the cervical or lumbar spinal segments is one of the most common indications for spine imaging and intervention, particularly among the elderly. This article examines the pathophysiology and imaging of the corresponding clinical syndromes, cervical spondylotic myelopathy or neurogenic intermittent claudication. The specificity fault of spine imaging is readily evident in evaluation of spinal stenosis, as many patients with anatomic cervical or lumbar central canal narrowing are asymptomatic. Imaging also may be insensitive to dynamic lesions. Those imaging features that identify symptomatic patients, or predict response to interventions, are emphasized.

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.

Conservative management of ossification of the posterior longitudinal ligament. A review

OBJECT

Ossification of the posterior longitudinal ligament (OPLL) can result in significant myelopathy. Surgical treatment for OPLL has been extensively documented in the literature, but less data exist on conservative management of this condition.

METHODS

The authors conducted a systematic review to identify all reported cases of OPLL that were conservatively managed without surgery.

RESULTS

The review yielded 11 published studies reporting on a total of 480 patients (range per study 1-359 patients) over a mean follow-up period of 14.6 years (range 0.4-26 years). Of these 480 patients, 348 (72.5%) were without myelopathy on initial presentation, whereas 76 patients (15.8%) had signs of myelopathy; in 56 cases (15.8%), the presence of myelopathy was not specified. The mean aggregate Japanese Orthopaedic Association score on presentation for 111 patients was 15.3. Data available for 330 patients who initially presented without myelopathy showed progression to myelopathy in 55 (16.7%), whereas the other 275 (83.3%) remained progression free. In the 76 patients presenting with myelopathy, 37 (48.7%) showed clinical progression, whereas 39 (51.5%) remained clinically unchanged or improved.

CONCLUSIONS

Patients who present without myelopathy have a high chance of remaining progression free. Those who already have signs of myelopathy at presentation may benefit from surgery due to a higher rate of progression over continued follow-up.

Ossification of the posterior longitudinal ligament: a review of literature

Ossification of the posterior longitudinal ligament (OPLL) is most commonly found in men, in the elderly, and in Asian patients. The disease can start with mild or no symptoms, but some patients progress slowly to develop symptoms of myelopathy. An accurate diagnosis through the use plain radiograph, computed tomography, and magnetic resonance imaging findings is very important to monitor the development of symptoms and to make decisions regarding a treatment plan. When symptoms are mild and non-progressive, conservative treatments and periodic observations are good enough, but once symptoms of myelopathy are present and neurologic symptoms are progressive, the treatment of choice is surgery to relieve spinal cord compression. Surgical management of OPLL continues to be controversial. Each surgical technique has some advantages and disadvantages, and the choice of operation should be decided carefully with various considerations. The patient's neurological condition, location and extent of pathology, cervical kyphosis, presence or absence of accompanied instability, and the individual surgeon's experience must be an important factors that should be considered before surgery.

Anterior surgery in selective patients with massive ossification of posterior longitudinal ligament of cervical spine: technical note

STUDY DESIGN

The study includes case series, technical note and review of literature.

OBJECTIVE

The objective of this study was to assess the validity of the radiographic indicator and the result of anterior operation for massive ossification of posterior longitudinal ligament (MOPLL, ossification of posterior longitudinal ligament with an occupying ratio exceeding 50%). Anterior decompression yielded a better outcome than posterior approach in patients with MOPLL of cervical spine. But anterior surgery has the problem of technically demanding and was associated with a high incidence of surgery-related complications. Many ways for reducing the risk of anterior surgery have been reported, including floating method, employing microscopes or burrs, and laser-assisted corpectomy.

MATERIALS AND METHODS

A case series of selective patients with MOPLL of cervical spine undergoing anterior surgery is reported. All patients were strictly selected based on CT images with the appearance of open-base. 29 cases with more than 12 months follow-up (average, 31.0 ± 10.0 m) were reviewed. Average age at operation was 59.3 ± 8.2 years (43-73 years). Anterior decompression was done only for one or two vertebrae.

RESULTS

One corpectomy was done in 13 cases, two corpectomies in 3 cases, and one corpectomy and one discectomy in 13 cases. Three levels were fused in 16 cases and two levels in 13 cases. No permanent neurological deterioration was observed. Neurological improvement was observed in every patients with an average improvement rate of 64 ± 23%. Mesh migration was observed in one case. A fusion rate of 100% was achieved.

CONCLUSION

Anterior surgery using our technique may be a relatively simple and safe procedure in selective patients with massive ossification of posterior longitudinal ligament of cervical spine.

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.

Incarcerated herniation of the cervical spinal cord after laminectomy for an ossification of the yellow ligament

A 74-year-old man showed a spastic gait and myelopathy in both the hands. Computed tomography revealed an OPLL on C3 and C4, bony spurs on the dorsal side of C4-C6, and an OYL on C3 and C4. We scheduled a two-stage decompression for both the OPLL and OYL. First, we performed laminectomy on the C3-C6 segments and resected the OYL. We did not observe any dural tear or CSF leakage in the dura. The patient's neurological symptoms improved. After the laminectomy, his myelopathy recurred. Postoperative MRI showed a spinal cord herniation. We had the C3/4 anterior cervical disectomy and fusion as we planned. In addition, we performed a surgery to repair the damaged dura mater at the site of spinal cord herniation at the same second surgery. The integrity of the arachnoid membrane was preserved. The patient's myelopathy gradually improved. There have been no reports on postoperative neurological deterioration caused by spinal cord herniation associated with a dural defect at the laminectomy site, without dural tear in the surgery after the resection of a posteriorly located cervical OYL. The possibility of a dural defect in OYL cases should be considered when planning a laminectomy for the resection of the OYL.

Wound-peritoneal shunts: part of the complex management of anterior dural lacerations in patients with ossification of the posterior longitudinal ligament

BACKGROUND

The complex management of dural lacerations occurring after the resection of multilevel ossification of the posterior longitudinal ligament (OPLL) requires further clarification.

METHODS

Both preoperative MR and CT studies documented multilevel ventral cord compression attributed to OPLL with kyphosis in 82 patients requiring multilevel anterior corpectomy/fusion (ACF) (average, 2.6 levels) followed by posterior fusion (PF) (average, 6.6 levels) under the same anesthetic. The 5 patients who developed intraoperative dural lacerations/penetration demonstrated the single-layer sign (2 patients: large central mass) or the double-layer sign (3 patients: hyperdense/hypodense/hyperdense layers) on preoperative 2-dimensional CT studies. All 5 patients were managed with complex dural repair (sheep pericardial grafts, fibrin sealant, microfibrillar collagen) and had shunts placed (wound-peritoneal and lumboperitoneal).

RESULTS

After complex dural repair/shunting, all 5 intraoperative dural lacerations (DLs) resolved. The application of low-pressure wound-peritoneal shunts was unique to this study (Uni-Shunts, Codman, Johnson and Johnson, Dorchester, Mass). The proximal end is placed lateral/parallel to the fibula strut graft/plate complex, whereas the distal catheter is tunneled into the peritoneum in the right upper quadrant (always prepared and draped in anticipation of the need for a shunt).

CONCLUSIONS

Of 82 patients undergoing multilevel anterior corpectomy for OPLL/kyphosis, 5 developed intraoperative DLs successfully managed with a complex dural repair, wound-peritoneal, and lumboperitoneal shunting procedures.

Diagnosis and surgery of ossification of posterior longitudinal ligament associated with dural ossification in the cervical spine

Direct removal of the ossified mass via anterior approach carries good decompression to ossification of the posterior longitudinal ligament (OPLL) in the cervical spine. Ossification occasionally involves not only the posterior longitudinal ligament but also the underlying dura mater, which increased the opportunity of the cerebrospinal fluid (CSF) leakage or neurological damage. The surgeon was required to recognize the dural ossification (DO) and need more cautious manipulation. Hida et al. first described the computed tomography (CT) findings that indicated the association with DO, and suggest the double-layer sign appeared more specific for DO. This study reviewed 138 patients who received anterior cervical corpectomy and fusion (ACCF) for OPLL, and 40 patients were found in the association with DO during anterior procedure. Radiological studies revealed that the patients with severe OPLL (higher occupying rate and larger extent) have increasing opportunity of association with DO. The double-layer sign, as a specific indicator for association with DO was sensitive in the patients with mild OPLL, but less frequent in those with severe OPLL with DO. Two surgical techniques were used for the patients with DO in anterior decompression procedure. When the double-layer sign was observed on CT scans, the OPLL could be separated from DO through a thin layer consisting a nonossified degenerated PLL to avoid CSF leakage. Otherwise, the entire ossified mass including OPLL and DO was removed completely. In this technique, the arachnoid membrane needed to be persevered with the aid of microscope to avoid a large area of membrane defect, resulting in uncontrolled CSF leakage. There was no significant difference in clinical results between the patients with DO and those without DO. Therefore, ACCF is meritorious for the patient with OPLL associated with DO, although more difficult manipulation and higher risk of CSF leakage.

Spinal cord herniation after multilevel anterior cervical corpectomy and fusion for ossification of the posterior longitudinal ligament of the cervical spine

The authors report the case of a 52-year-old man who had undergone resection of an ossified posterior longitudinal ligament via the anterior approach. The patient experienced postoperative neurological deterioration that may have been caused by a massive cord herniation associated with a dural defect at the corpectomy site.

Spinal cord herniation may develop as a complication of anterior cervical decompression. Surgeons should be alert to this condition when planning to treat cervical ossification of the ossified posterior longitudinal ligament via the anterior approach.

Anterior corpectomy and fusion for severe ossification of posterior longitudinal ligament in the cervical spine

Between May 2002 and October 2006, 19 patients (17 men and 2 women; average age 57.2; range 47-71 years) received anterior corpectomy and fusion for severe ossification of the posterior longitudinal ligament (OPLL) in our department. Preoperative radiological evaluation showed the narrowing by the OPLL exceeded 50% in all cases, and OPLL extended from one to three vertebrae. We followed-up all patients for 12-36 months (mean 18 months). The Japanese Orthopaedic Association (JOA) score before surgery was 9.3 +/- 1.8 (range 5-12) which significantly increased to 14.2 +/- 1.3 (range 11-16) points at the last follow-up (P < 0.01). The improvement rate (IR) of neurological function ranged from 22.2-87.5%, with a mean of 63.2% +/- 15.2%. The operation also provided a significant increase in the cervical lordosis and the cord flatting rate (P < 0.01). No severe neurological complication developed. We therefore concluded that anterior decompression and fusion was effective and safe in the treatment of the selected patients, although OPLL exceeded 50% diameter of the spinal canal.

Significance of the double- and single-layer signs in the ossification of the posterior longitudinal ligament of the thoracic spine

OBJECTIVE

The purpose of this study was to elucidate the significance of the signs of dural ossification applied to the thoracic ossification of the posterior longitudinal ligament (OPLL), as originally described for cervical OPLL by Hida et al.

METHODS

Twenty patients with thoracic OPLL who underwent anterior decompression were retrospectively studied through examination of preoperative computed tomographic scans and medical records. The types of OPLL, single- and double-layer signs, as well as actual dural penetration were evaluated.

RESULTS

Signs of dural ossification were found in 80.0% of the patients. There were 10 (71.4%) cases of a dural ossification sign among the 14 patients with segmental OPLL and six (100%) cases of a dural ossification sign among the six patients with non-segmental OPLL. Dural defects were present in six (60.0%) out of 10 patients with a double-layer sign and three (50.0%) out of six patients with a single-layer sign.

CONCLUSION

There are several differences between thoracic and cervical OPLL in regard to dural ossification signs. The incidence of these signs with thoracic OPLL was higher than that with cervical OPLL, and these signs can develop in a segmental OPLL as frequently as in a non-segmental OPLL. Dural defects were present in 60% of the patients with a double-layer sign and in 50% of the patients with a single-layer sign. Therefore, surgeons should be alert for the high possibility of a dural defect when these signs are present in thoracic OPLL, although, a dural defect can develop even in the absence of the signs.

Significance of the double-layer and single-layer signs in the ossification of the posterior longitudinal ligament of the cervical spine

Object

The purpose of this study was to elucidate the significance of the signs of dural penetration, which were previously described by Hida et al. This goal was accomplished by an analysis of preoperative computed tomography scans and a review of the medical records of patients who underwent removal of the ossification of the posterior longitudinal ligament (OPLL) via the anterior approach.

Methods

Outcomes in 197 patients with cervical OPLL who underwent anterior decompression and fusion were studied retrospectively. The types of OPLL, single- and double-layer signs of dural penetration, diameter of the central hypodense mass of the double-layer sign, and the presence of actual dural penetration were evaluated.

Signs of dural penetration were found in 30.5% of patients. These signs were much more prevalent in patients with nonsegmental OPLL. Dural defects were present in 20 (52.6%) of 38 patients with double-layer signs and in three (13.6%) of 22 patients with single-layer signs. Among patients in the double-layer sign group, the mean diameter of the central hypodense masses was thicker in the group with an actual dural defect. Although not to the degree reported by Hida et al., the double-layer sign had a significant association with dural defects. In particular, the thicker the central hypodense mass of the double-layer sign, the greater the possibility of a dural defect. However, a single-layer sign had less significance than a double-layer one.

Conclusions

Surgeons should be alert to the increased possibility of a dural defect when there is a double-layer sign with a thick central hypodense mass in nonsegmental OPLL.

Factors Affecting Prognosis of Patients Who Underwent Corpectomy and Fusion for Treatment of Cervical Ossification of the Posterior Longitudinal Ligament

OBJECTIVE

Even though cervical ossification of the posterior longitudinal ligament (OPLL) has several unique clinical features compared with spondylotic myelopathy or cervical disc disease, there have been few reports about factors affecting prognosis after decompression using corpectomy. To clarify the prognostic factors for cervical OPLL, the authors analyzed the clinical and radiologic parameters of 47 patients retrospectively.

METHODS

The patients were classified into a good-prognosis group and a poor-prognosis group according to the changes of Nurick grade after operation. Age at operation, gender, preoperative Nurick grade, duration of symptoms, snake-eye appearance, occupying ratio, type of OPLL, Pavlov ratio, and double-layer sign did not affect the prognosis significantly.

RESULTS

Multiple logistic regression analysis revealed that diabetes mellitus (DM) was the only statistically significant factor predicting poor prognosis for the patients with cervical OPLL who underwent corpectomy and fusion.

CONCLUSIONS

Surgeons do not have to be discouraged from performing anterior decompression for the patients with cervical OPLL on the basis of age, severity of disease (preoperative Nurick grade or occupying ratio), irreversible changes in gray matter of the spinal cord (snake-eye appearance), or duration of symptoms. We should direct our attention to DM as a potent risk factor for cervical OPLL and try to clarify the mechanism by which DM possibly affected the functional recovery of the patients.

Dural ossification associated with cervical ossification of the posterior longitudinal ligament: frequency of dural ossification and comparison of neuroimaging modalities in ability to identify the disease

OBJECT

The authors' goal in this study was to understand the frequency and pattern of dural ossification (DO, and to evaluate the effectiveness of neuroimaging modalities used to identify this disease in association with ossification of the posterior longitudinal ligament (OPLL).

METHODS

One hundred eleven patients with OPLL underwent anterior procedures. Of these patients, 17 (15.3%) had associated ossification of the dura mater. There were 10 cases of DO in the 94 patients with segmental OPLL and seven in the 17 patients with nonsegmental OPLL (seven continuous and 10 mixed-type OPLL). Retrospective evaluation of DO was performed by examining plain x-ray films, polytomography studies, computerized tomography (CT) scans, and magnetic resonance (MR) images. A positive correlation was found between the type of OPLL and the frequency of DO (p < 0.01). The DO was classified into the following three types according to shape: 1) isolated type, 2) double-layer type, and 3) en bloc type, based on its relationship with OPLL. There were 10 lesions of the double-layer type, four en bloc type, and three isolated type; the double-layer pattern of DO was the most common. All DOs as well as OPLLs (17 cases) were identified using bone-window CT scanning. Polytomography was used successfully to identify all 12 OPLLs, whereas DO was recognized in seven of the 12 cases. Magnetic resonance imaging could not identify DO (none of the 17 cases), although OPLL was identified on MR imaging in 12 of the 17 cases.

CONCLUSIONS

Three patterns of DO associated with OPLL, that is, isolated, double-layer, and en bloc types, were confirmed by retrospective analysis of neuroimaging findings. Nonsegmental OPLL was likely to be accompanied by DO. Bone-window CT scanning was most useful for identification of DO as well as OPLL, whereas MR imaging was ineffective in recognizing DO.

Ossification of the posterior longitudinal ligament. Results of anterior cervical decompression and arthrodesis in sixty-one North American patients

BACKGROUND

Ossification of the posterior longitudinal ligament is commonly associated with cervical myelopathy. Surgical treatment is a matter of controversy. We report on a series of patients who were managed with anterior cervical decompression and arthrodesis for the treatment of cervical myelopathy associated with ossification of the posterior longitudinal ligament.

METHODS

We retrospectively reviewed the records for all sixty-five patients who had been managed with anterior decompression and arthrodesis for the treatment of cervical ossification of the posterior longitudinal ligament and associated neurologic compression from 1982 to 2001. Sixty-one patients (thirty-nine men and twenty-two women) were followed for at least two years (or until the time of death). The average number of vertebrae resected was 2.2. The average duration of follow-up for the sixty surviving patients was four years (range, two years to fifteen years and four months). The preoperative, six-week postoperative, and final follow-up clinical status (including neurological function as assessed with the Nurick grading system) was recorded for each patient.

RESULTS

Fifty-six of the sixty-one patients had neurological improvement, with an average improvement of 1.5 Nurick grades at the time of the final follow-up. Eight patients had absent dura at the time of surgery and, of these, five had development of a cerebrospinal fluid fistula. Eight patients had development of new neurological signs and/or symptoms in the upper extremity postoperatively. Eight patients required reoperation because of a painful pseudarthrosis (one patient), strut-graft dislodgment (three), cerebrospinal fluid leakage (three), or compression of a nerve root caudad to the area of the original procedure (one). One patient died as the result of cardiac arrest on the third postoperative day. Fifty-eight patients had an osseous fusion, one had an asymptomatic nonunion, and one had a symptomatic pseudarthrosis that was treated with revision surgery.

CONCLUSIONS

Anterior decompression and arthrodesis is an effective way to achieve pain relief and neurological improvement in North American patients of non-Asian descent who have cervical myelopathy associated with ossification of the posterior longitudinal ligament. The risk of durocutaneous fistula, graft dislodgment, and postoperative neurological symptoms appears to be high in patients with cervical myelopathy associated with this condition.

Diagnosis and surgical management of cervical ossification of the posterior longitudinal ligament

BACKGROUND CONTEXT

The diagnosis and treatment of multilevel cervical ossification of the posterior longitudinal ligament (OPLL) is continuing to evolve as its effects become more readily recognized and surgical alternatives expand.

PURPOSE

To review the clinical, neurodiagnostic and surgical management of OPLL.

STUDY DESIGN/SETTING

Patients with early OPLL, often in their mid-forties, present with radiculopathy or mild/moderate myelopathy. Radiographically, hypertrophy of the posterior longitudinal ligament with punctate ossification appears opposite multiple disc spaces. Patients with classic OPLL frequently become symptomatic in their mid-fifties with radiographic characteristics showing ossification of the ligament behind the vertebrae alone (segmental), behind the vertebrae including the intervertebral disc spaces (continuous), and combinations of the segmental and continuous variants and OPLL opposite disc spaces alone. Both magnetic resonance imaging (MRI) and computed tomography (CT) examinations are critical. MRI better delineates the extent of soft tissue abnormalities in three dimensions, including the cervicothoracic junction, whereas CT more readily identifies the foci of frank ossification. Surgical alternatives include anterior, posterior or combined approaches. Anterior surgical options include plated multilevel anterior discectomy and fusion, anterior cervical corpectomy with fusion (ACF), or plated multilevel ACF with differing posterior fusion techniques. Posterior surgical options vary from laminectomy with or without simultaneous fusion and laminoplasty. Although outcomes with different approaches vary, many direct anterior resection techniques achieve more favorable results because of appropriate and adequate resection of the ligament.

CONCLUSIONS

The clinical and neuroradiographic documentation of OPLL and its appropriate surgical management anteriorly, posteriorly or circumferentially remain a therapeutic challenge.

Ossification of the cervical posterior longitudinal ligament: a review

Ossification of the cervical posterior longitudinal ligament (OPLL) represents a continuum beginning with hypertrophy of the posterior longitudinal ligament (PLL) followed by progressive coalescence of centers of chondrification and ossification. Early OPLL mimicking disc disease appears opposite multiple disc spaces associated with significant retrovertebral extension, helping to differentiate it from spondylosis. On computerized tomography examinations, the single- and double-layer signs indicate possible dural penetration with the increased potential for an intraoperative cerebrospinal fluid fistula during dissection. Direct ventral resection of OPLL in patients younger than 65 years of age is optimal and includes single- or multilevel anterior corpectomy with fusion, the latter accompanied by posterior fusion. For patients older than the age of 65 years, with a well-preserved cervical lordosis, laminectomy with or without fusion and/or laminoplasty may suffice in providing indirect dorsal decompression. Patients undergoing circumferential procedures with halo devices are managed with a specific anesthetic protocol, including awake intubation and positioning with intraoperative monitoring of somatosensory evoked potentials, electromyography, and the option of undergoing motor evoked potential monitoring. Intubation is maintained during the 1st postoperative night. When circumferential procedures are performed intubation is always maintained during the 1st postoperative night, and fiberoptic postoperative extubation is electively performed by specifically trained anesthesiologists when deemed appropriate. Patients exhibiting three or more major risk factors are considered candidates for delayed extubation and rarely, tracheostomy. Repeated anterior surgery, operations lasting more than 10 hours, involving four or more levels (including C-2), obesity, asthma, and blood transfusions of more than 4 U (1000-1200 ml) are all considered major risk factors.

Anterior approaches to cervical spondylosis and ossification of the posterior longitudinal ligament: review of operative technique and assessment of 65 multilevel circumferential procedures

BACKGROUND

Multilevel anterior cervical corpectomy with fusion (ACF) offers direct resection of spondylostenosis and ossification of the posterior longitudinal ligament (OPLL) with immediate stabilization. Ideal candidates for multilevel ACF include younger patients (<65 years of age), or older individuals (>65 years of age) with loss or reversal of the cervical lordosis (kyphosis).

METHODS

Sixty-five patients, averaging 56 years of age and including 40 males and 25 females, with multilevel MR- and CT-documented spondylostenosis and OPLL were studied. Preoperatively, patients exhibited moderate to severe myelopathy (average Nurick grade 3.8), and were managed with 2- to 4-level ACF with posterior wiring and fusion (PWF) procedures with halo application. The first 22 patients had no plate instrumentation, the next 22 had constrained (Orion) plates applied followed sequentially by the application of 13 semi-constrained (Atlantis) plates, and finally, 8 dynamic (ABC Aesculap) plates.

RESULTS

Patients improved an average of three postoperative Nurick grades. None exhibited new cord injuries, whereas three had transient C5 root paresis. Graft/plate or vertebral fracture with extrusion were observed in 3/22 nonplated patients, 2/22 constrained-plated patients, 3/13 semi-constrained-plated patients, and 0/8 dynamic-plated patients. Fusion was documented on dynamic radiographs and 2D-CT or 3D-CT studies obtained 3 and 6 months postoperatively, or later where indicated.

CONCLUSIONS

Multilevel ACF/PWF offers direct resection of spondylostenosis and OPLL with immediate maximal stabilization. Thus far, no graft/plate or vertebral body fracture or extrusions have been seen with dynamic plates, whereas the absence of plating and constrained and semi-constrained plating systems have failed.