A new classification of thoracolumbar injuries: the importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status

STUDY DESIGN

A new proposed classification system for thoracolumbar (TL) spine injuries, including injury severity assessment, designed to assist in clinical management.

OBJECTIVE

To devise a practical, yet comprehensive, classification system for TL injuries that assists in clinical decision-making in terms of the need for operative versus nonoperative care and surgical treatment approach in unstable injury patterns.

SUMMARY OF BACKGROUND DATA

The most appropriate classification of traumatic TL spine injuries remains controversial. Systems currently in use can be cumbersome and difficult to apply. None of the published classification schemata is constructed to aid with decisions in clinical management.

METHODS

Clinical spine trauma specialists from a variety of institutions around the world were canvassed with respect to information they deemed pivotal in the communication of TL spine trauma and the clinical decision-making process. Traditional injury patterns were reviewed and reconsidered in light of these essential characteristics. An initial validation process to determine the reliability and validity of an earlier version of this system was also undertaken.

RESULTS

A new classification system called the Thoracolumbar Injury Classification and Severity Score (TLICS) was devised based on three injury characteristics: 1) morphology of injury determined by radiographic appearance, 2) integrity of the posterior ligamentous complex, and 3) neurologic status of the patient. A composite injury severity score was calculated from these characteristics stratifying patients into surgical and nonsurgical treatment groups. Finally, a methodology was developed to determine the optimum operative approach for surgical injury patterns.

CONCLUSIONS

Although there will always be limitations to any cataloging system, the TLICS reflects accepted features cited in the literature important in predicting spinal stability, future deformity, and progressive neurologic compromise. This classification system is intended to be easy to apply and to facilitate clinical decision-making as a practical alternative to cumbersome classification systems already in use. The TLICS may improve communication between spine trauma physicians and the education of residents and fellows. Further studies are underway to determine the reliability and validity of this tool.

Progression of ossification of the posterior longitudinal ligament following en bloc cervical laminoplasty

BACKGROUND

Ossification of the posterior longitudinal ligament often causes compressive myelopathy. Ossification is a progressive disease, and it has been reported that the area of ossification increases after decompressive surgery. However, it is uncertain how the progression of ossification affects the long-term outcome after cervical laminoplasty. This study was performed to clarify the relationship between the progression of ossification of the posterior longitudinal ligament and the clinical results following en bloc cervical laminoplasty.

METHODS

Forty-five patients who were followed for more than ten years after laminoplasty participated in this study. Radiographs and tomograms of the cervical spine of each patient were made before and after the operation and at the time of the latest follow-up. The extent of ossification in the longitudinal and sagittal axes was evaluated. Neurological function was graded with use of the Japanese Orthopaedic Association scoring system. The relationship between the progression of ossification and the score-based rate of recovery was analyzed.

RESULTS

Thirty-three (73%) of the patients had progression of ossification of the posterior longitudinal ligament after laminoplasty. Progression was frequent in patients with the mixed type of ossification and in those with the continuous type, whereas it was rare in patients with the segmental type. The patients with progression of the ossification were significantly younger than those without progression (p = 0.018). The Japanese Orthopaedic Association score improved rapidly within one year and continued to improve up to five years after surgery. The score tended to decrease thereafter. For thirteen patients, the score had worsened at the time of the latest follow-up. Three patients had neurological deterioration following an increase in the thickness of the ossification.

CONCLUSIONS

Progression of ossification of the posterior longitudinal ligament was often observed during the long-term follow-up period after laminoplasty. Young patients with mixed and continuous types of ossification had the greatest risk for progression. Preventive measures, such as the use of a wider laminar opening during the laminoplasty, should be considered for patients who are at risk for progression of ossification.

Magnetic resonance evaluation of the intervertebral disc, spinal ligaments, and spinal cord before and after closed traction reduction of cervical spine dislocations

STUDY DESIGN

A prospective clinical study using magnetic resonance imaging of the cervical spine in a consecutive series of patients with cervical spine dislocations.

OBJECTIVES

To determine the incidence of intervertebral disc herniations and injury to the spinal ligaments before and after awake closed traction reduction of cervical spine dislocations.

SUMMARY OF BACKGROUND DATA

Prior series in which the prereduction imaging of disc herniations in the dislocated cervical spine are described have been anecdotal and have involved small numbers of patients. In addition, no uniform clinical criteria to define the presence of an intervertebral disc herniation in the dislocated cervical spine has been described. The incidence of disc herniations in the unreduced dislocated cervical spine is unknown.

METHODS

Eleven consecutive patients with cervical spine dislocations who met the clinical criteria for an awake closed traction reduction had prereduction and postreduction magnetic resonance imaging. Using strict clinical criteria for the definition of an intervertebral disc herniation, the presence or absence of disc herniation, spinal ligament injury, and cord injury was determined. Neurologic status before, during, and after the closed reduction maneuver was documented.

RESULTS

Disc herniations were identified in 2 of 11 patients before reduction. Awake closed traction reduction was successful in 9 of the 11 patients. Of the nine patients with a successful closed reduction, two had disc herniations before reduction, and five had disc herniations after reduction. No patient had neurologic worsening after attempted awake closed traction reduction.

CONCLUSIONS

The process of closed traction reduction appears to increase the incidence of intervertebral disc herniations. The relation of these findings, however, to the neurologic safety of awake closed traction reduction remain unclear.

Long-term results of the anterior floating method for cervical myelopathy caused by ossification of the posterior longitudinal ligament

STUDY DESIGN

Results of the anterior floating method used to decompress ossification of the posterior longitudinal ligament were studied for an average postoperative interval of 13 years.

OBJECTIVE

To investigate the long-term results of the anterior floating method used to manage ossification of the posterior longitudinal ligament.

SUMMARY OF BACKGROUND DATA

The anterior floating method is a technique that differs from the extirpation method used to manage ossification of the posterior longitudinal ligament. Reports of the long-term results from anterior decompression used to manage cervical ossification of the posterior longitudinal ligament are rare.

METHODS

The anterior floating method was used to decompress cervical ossification of the posterior longitudinal ligament in 63 patients. These patients were followed for more than 10 years with neurologic evaluations using a scoring system proposed by the Japanese Orthopedic Association (JOA score).

RESULTS

The recovery rate was 66.5% at 10 years and 59.3% at 13 years, the time of the final survey. Operative outcomes most closely reflected the preoperative duration and severity of myelopathy (JOA score) and the preoperative cross-sectional area of the spinal cord. There was no correlation with the canal narrowing ratio or the thickness of ossification of the posterior longitudinal ligament. Delayed deterioration was attributed to an original inadequate decompression and progression of ossification of the posterior longitudinal ligament outside the original operative field. There was no evidence of significant recurrent ossification of the posterior longitudinal ligament within the margins of prior decompression.

CONCLUSIONS

The anterior floating method appears to yield adequate long-term outcomes when used to manage ossification of the posterior longitudinal ligament.

Pathology of ossification of the posterior longitudinal ligament and ligamentum flavum

Ossification takes place in the posterior longitudinal ligament and ligamentum flavum of the spine under certain conditions of unknown nature. Ossification of these ligaments has the following characteristics: (1) ectopic bone formation occurring within the spinal ligaments; (2) ossification accompanies ligamentous tissue hyperplasia and cell proliferation; (3) before ossification, fibrocartilaginous cell proliferation, calcification and tissue resorption with vascular ingrowth take place sequentially; (4) ossification of the ligament has a specific site of predilection and often occurs in combination with senile ankylosing vertebral hyperostosis (Forestier's disease) or diffuse idiopathic skeletal hyperostosis; and (5) ossification and symptom development are remarkably more frequent in the Japanese population. Recent studies revealed that bone morphogenetic proteins and transforming growth factor-beta played an important role in the matrix hyperplasia and ossification of the spinal ligament, and metabolic and genetic aberration often characterized patients suffering from this disorder.

Ligamentous ossification of the cervical spine in the late middle-aged Japanese men. Its relation to body mass index and glucose metabolism

STUDY DESIGN

The present study investigated the relationship of obesity and glucose metabolism in persons with ossification of the anterior longitudinal ligament, ossification of the nucal ligament, and ossification of the posterior longitudinal ligament of the cervical spine.

OBJECTIVE

To provide a insight into the etiology of ligamentous ossification of the cervical spine.

SUMMARY OF BACKGROUND DATA

The high incidence of ligamentous ossification of the cervical spine with obese patients has been reported, but no definite association was reported between the incidence of ossification of the anterior longitudinal ligament, ossification of the nucal ligament, and ossification of the posterior longitudinal ligament and their bone mass index values.

METHODS

Lateral cervical radiographs and 75 g oral glucose tolerance tests of more than 4802 Japanese men aged 48-57 years at the Self Defense Force Hansin Hospital were evaluated.

RESULTS

The incidences of ossification of the anterior longitudinal ligament, ossification of the nucal ligament, and ossification of the posterior longitudinal ligament were 23.1% (1110 of 4802), 23.3% (1117 of 4802) and 4.1% (198 of 4802), respectively. In the groups whose body mass index was 25 or more, the incidences of ossification of the anterior longitudinal ligament, ossification of the nucal ligament, and ossification of the posterior longitudinal ligament were significantly high (P < 0.01). The higher incidence of diabetes or impaired glucose tolerance was statistically significant in ossification of the anterior longitudinal ligament and ossification of the posterior longitudinal ligament but not in ossification of the nucal ligament. The rates, which showed significantly high glucose response by 1-hour or 2-hour plasma glucose level after oral glucose tolerance tests with body mass index-matched control subjects, were ossification of the anterior longitudinal ligament, 93.5%; ossification of the posterior longitudinal ligament, 52.0%; and ossification of the nucal ligament, 14.0%, respectively.

CONCLUSIONS

From this study, obesity was shown to be the major risk factor of ossification of the nucal ligament, and obesity and glucose intolerance were risk factors in ossification of the anterior longitudinal ligament and ossification of the posterior longitudinal ligament. The authors concluded the morbidity rates of ossification of the anterior longitudinal ligament. ossification of the nucal ligament, and ossification of the posterior longitudinal ligament were high in obesity, however, concerning the glucose intolerance, ossification of the nucal ligament is etiologically different from ossification of the anterior longitudinal ligament and ossification of the posteior longitudinal ligament.

Ossified posterior longitudinal ligament: management strategies and outcomes

PURPOSE

This study was designed to determine the management strategies and outcomes of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

METHODS

One hundred twenty-one patients with radiologically proven OPLL including early form of OPLL (EOPLL) and hypertrophy of the posterior longitudinal ligament (HPLL) underwent surgical intervention either by the anterior procedure or posterior procedure from 1993 to 2002. The anterior approach with direct removal of OPLL was performed on 111 patients with one- or two-level OPLL, whereas expansive laminoplasty was performed as the choice posterior procedure on 10 cases with extensive OPLL. The surgery-related outcome was excellent or good for 88% and fair for 12%. This clinical improvement correlated well with the severity of the preoperative myelopathy. Two patients underwent the second anterior procedure after expansive laminoplasty. OPLL associated with dural ossification may show cerebrospinal fluid leakage after resection of the OPLL and dural ossification.

CONCLUSIONS

One- or two-level OPLL can be resected by an anterior approach with partial corpectomy, whereas expansive laminoplasty is indicated for multilevel compressive myelopathy due to OPLL. EOPLL and HPLL should be carefully examined with radiological workups because they are a prestage form of OPLL.

MRI findings of thoracolumbar spine fractures: a categorisation based on MRI examinations of 100 fractures

OBJECTIVE

To define the state of different structures of the fractured thoracolumbar spine which may play a role in the immediate and long-term mechanical stability on MR images and to investigate the relationship of these findings with the AO classification of spinal injuries.

DESIGN

The state of the anterior longitudinal ligament, posterior longitudinal ligament, posterior ligamentous complex, cranial and caudal endplates, cranial and caudal discs and the vertebral body were defined using clinical, experimental and radiological data. The state of these structures was reported for each fracture on the MRI examinations and the different MRI features appropriate for different fracture classes were defined.

PATIENTS

MRI examinations of 70 patients with 100 fractures of the thoracolumbar spine were used for this study.

RESULTS

Wide variations were seen in the state of the structures studied. We could not find a definite pattern to relate these findings with the AO classification scheme.

CONCLUSIONS

MR findings should be integrated into future classification schemes of thoracolumbar spine fractures. This would enable specific data about the structures involved in the stability of the spine to be acquired. Prospective studies using the criteria developed in this study may help resolve some of the controversies concerning the diagnosis and prognosis of these injuries as well as the development of new classification systems.

Repetitive tensile stress to rat caudal vertebrae inducing cartilage formation in the spinal ligaments: a possible role of mechanical stress in the development of ossification of the spinal ligaments

Object

Mechanical stress has been considered one of the important factors in ossification of the spinal ligaments. According to previous clinical and in vitro studies, the accumulation of tensile stress to these ligaments may be responsible for ligament ossification. To elucidate the relationship between such mechanical stress and the development of ossification of the spinal ligaments, the authors established an animal experimental model in which the in vivo response of the spinal ligaments to direct repetitive tensile loading could be observed.

Methods

The caudal vertebrae of adult Wistar rats were studied. After creating a novel stimulating apparatus, cyclic tensile force was loaded to rat caudal spinal ligaments at 10 N in 600 to 1800 cycles per day for up to 2 weeks. The morphological responses were then evaluated histologically and immunohistochemically.

After the loadings, ectopic cartilaginous formations surrounded by proliferating round cells were observed near the insertion of the spinal ligaments. Several areas of the cartilaginous tissue were accompanied by woven bone. Bone morphogenetic protein–2 expression was clearly observed in the cytoplasm of the proliferating round cells. The histological features of the rat spinal ligaments induced by the tensile loadings resembled those of spinal ligament ossification observed in humans.

Conclusions

The findings obtained in the present study strongly suggest that repetitive tensile stress to the spinal ligaments is one of the important causes of ligament ossification in the spine.

Acute spinal ligament disruption: MR imaging with anatomic correlation

Disruption of spinal ligaments can lead to instability that jeopardizes the spinal cord and nerve roots. Magnetic resonance (MR) imaging can directly image spinal ligaments; however, the sensitivity with which this modality demonstrates ligament injury has, to the authors' knowledge, not been reported. On a biomechanical testing machine, 28 cadaveric spines were subjected to controlled injury that resulted in ligament tears. The spines were then imaged with plain radiography, computed tomography, and MR imaging (1.5 T). The images were analyzed for evidence of ligament injury before dissection of the specimen. Forty-one of 52 (79%) ligament tears of various types were correctly identified at MR imaging. Disruptions of the anterior and posterior longitudinal ligaments were most conspicuous and were detected in all seven cases in which they were present (no false-positive or false-negative results); disruptions of the ligamentum flavum, capsular ligaments, and interspinous ligaments could also be identified but less reliably (three false-positive and 11 false-negative results). That MR imaging can reliably and directly allow assessment of spinal ligament disruption in this in vitro model suggests its potential utility for this assessment in patients.

Thoracolumbar burst fractures: evaluation with MR imaging

PURPOSE

To determine the frequency of posterior ligamentous injury that occurs in patients with thoracolumbar burst fractures and to correlate ligamentous disruption with radiographic appearance.

MATERIALS AND METHODS

Magnetic resonance (MR) imaging examinations of 21 patients with 25 thoracolumbar burst fractures were retrospectively evaluated to determine spinal ligament integrity. Radiographic and computed tomographic (CT) examinations were evaluated for interpediculate widening, midsagittal canal narrowing, posterior element fractures, and kyphosis; a radiographic assessment of posterior ligamentous integrity was made. These findings were then correlated with the status of the spinal ligaments.

RESULTS

The patients were divided into two groups on the basis of the status of their supraspinous ligament (SSL). Six patients had disrupted SSLs, and 15 had intact SSLs. Radiographic and CT findings did not correlate with supraspinous ligament disruption. Radiographic indicators of posterior ligamentous disruption were present in only 33% of patients with SSL disruption.

CONCLUSION

SSL disruption is a frequent occurrence in patients with burst fractures. No radiographic features of burst fractures correlate with SSL disruption, and radiographic signs of posterior ligamentous disruption are insensitive.

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

Ossification of the posterior longitudinal ligament (OPLL) can cause severe and irreversible paralysis in not only the cervical spine but also the thoracolumbar spine. To date, however, the prevalence and distribution of OPLL in the whole spine has not been precisely evaluated in patients with cervical OPLL. Therefore, we conducted a multi-center study to comprehensively evaluate the prevalence and distribution of OPLL using multi-detector computed tomography (CT) images in the whole spine and to analyze what factors predict the presence of ossified lesions in the thoracolumbar spine in patients who were diagnosed with cervical OPLL by plain X-ray. Three hundred and twenty-two patients with a diagnosis of cervical OPLL underwent CT imaging of the whole spine. The sum of the levels in which OPLL was present in the whole spine was defined as the OP-index and used to evaluate the extent of ossification. The distribution of OPLL in the whole spine was compared between male and female subjects. In addition, a multiple regression model was used to ascertain related factors that affected the OP-index. Among patients with cervical OPLL, women tended to have more ossified lesions in the thoracolumbar spine than did men. A multiple regression model revealed that the OP-index was significantly correlated with the cervical OP-index, sex (female), and body mass index. Furthermore, the prevalence of thoracolumbar OPLL in patients with a cervical OP-index ≥ 10 was 7.8 times greater than that in patients with a cervical OP-index ≤ 5. The results of this study reveal that the extent of OPLL in the whole spine is significantly associated with the extent of cervical OPLL, female sex, and obesity.

Clinicopathological study of "snake-eye appearance" in compressive myelopathy of the cervical spinal cord

OBJECT

The goal of this study was to elucidate the pathophysiological features and clinical significance of the magnetic resonance imaging-documented small intramedullary high signal intensity known as "snake-eye appearance" (SEA) in cases of compressive myelopathy such as cervical spondylosis or ossification of the posterior longitudinal ligament.

METHODS

One hundred forty-four patients with compression myelopathy who underwent surgery between 1998 and 2000 were selected. Intramedullary high signal intensity was found in 79 cases and was divided into two types, SEA and non-SEA (NSEA). The Japan Orthopaedic Association (JOA) scoring system was used for evaluation of pre- and postoperative neurological status. In nine cases of SEA autopsy was performed and specimens were histologically analyzed. The improvement ratio determined by JOA score was 32.2 +/- 15.1% in SEA, 47.1 +/- 12.1% in NSEA, and 50 +/- 18.3% (p < 0.01) in control cases in which high signal intesity was absent. There were significant differences among SEA, NSEA, and control groups. In a separate group of nine patients who died of unrelated causes, histological examination showed small cystic necrosis in the center of the central gray matter of the ventrolateral posterior column and significant neuronal loss in the flattened anterior horn.

CONCLUSIONS

Snake-eye appearance was found to be a product of cystic necrosis resulting from mechanical compression and venous infarction. Destruction of the gray matter accompanying significant neuronal loss in the anterior horn suggested that SEA is an unfavorable prognostic factor for the recovery of upper-extremity motor weakness.

The influence of fracture mechanism and morphology on the reliability and validity of two novel thoracolumbar injury classification systems

STUDY DESIGN

The Thoracolumbar Injury Severity Score (TLISS) and the Thoracolumbar Injury Classification and Severity Score (TLICS) were prospectively evaluated.

OBJECTIVES

To compare the reliability and validity of the TLISS and TLICS schemes to determine the importance of injury mechanism and morphology to the identification and treatment of thoracolumbar fractures.

SUMMARY OF BACKGROUND DATA

Two novel algorithms have been developed for the categorization and management of thoracolumbar injuries: the TLISS system emphasizing injury mechanism and the TLICS scheme involving injury morphology.

METHODS

The clinical and radiographic findings of 25 patients with thoracolumbar fractures were prospectively presented to 5 groups of surgeons with disparate levels of training and experience with spinal trauma. These injuries were consecutively scored, first using the TLISS and then 3 months later with the TLICS. The recommended treatments proposed by the 2 schemes were compared with the actual management of each patient.

RESULTS

For both algorithms, the interrater kappa statistics of all subgroups (mechanism/morphology, status of the posterior ligaments, total score, predicted management) were within the range of moderate to substantial reproducibility (0.45-0.74), and there were no statistically significant differences noted between the respective kappa values. Interrater correlation was higher for the TLISS paradigm on mechanism/morphology, integrity of the posterior ligaments, and proposed management (P < or = 0.01). The TLISS and TLICS schemes both exhibited excellent overall validity.

CONCLUSIONS

Although both schemes were noted to have substantial reproducibility and validity, our results indicate the TLISS is more reliable than the TLICS, suggesting that the mechanism of trauma may be a more valuable parameter than fracture morphology for the classification and treatment thoracolumbar injuries. Since these injury characteristics are interrelated and are critical to the maintenance of spinal stability, we think that both concepts should be considered during the assessment and management of these patients.

Uniaxial cyclic stretch induces osteogenic differentiation and synthesis of bone morphogenetic proteins of spinal ligament cells derived from patients with ossification of the posterior longitudinal ligaments

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments. Mechanical stress, which acts on the posterior ligaments, is thought to be an important factor in the progression of OPLL. To elucidate this mechanism, we investigated the effects of in vitro sinusoidal cyclic stretch (120% peak to peak, at 1 Hz) on cultured spinal ligament cells derived from OPLL and non-OPLL patients. The mRNA expressions of alkaline phosphatase (ALP), osteopontin, bone morphogenetic protein (BMP)-2, BMP-4, and BMP receptors as well as ALP activity in cell layers and production of BMPs into the conditioned medium were significantly increased by cyclic stretch in OPLL cells, whereas no change was observed in non-OPLL cells. A stretch-activated Ca(2+) channel blocker, Gd(3+), the voltage-dependent L-type Ca(2+) channel blockers diltiazem and nifedipine, and Ca(2+)-free medium suppressed stretch-induced ALP activity, which suggests a role of Ca(2+) influx in the signal transduction of mechanical stress to the osteogenic response of OPLL cells. Our study provides first evidences that mechanical stress plays a key role in the progression of OPLL through the induction of osteogenic differentiation in spinal ligament cells and the promotion of the autocrine/paracrine mechanism of BMPs in this lesion.

Effect of the transligamentous extension of lumbar disc herniations on their regression and the clinical outcome of sciatica

STUDY DESIGN

Magnetic resonance imaging of symptomatic herniated lumbar discs was investigated longitudinally and prospectively for the presence of tear in the posterior longitudinal ligament (PLL).

OBJECTIVES

To clarify the effect of transligamentous extension through the PLL of herniated disc on its regression and to determine the factors contributing to a successful clinical outcome.

SUMMARY OF BACKGROUND DATA

Greater regression of the herniated fragment has been noted with larger initial disc herniations. The exposure of herniated disc materials to the epidural vascular supply through the ruptured PLL has been suspected to play a part in the mechanism of disappearance of the herniated nucleus pulposus. However, it had not been shown clinically.

METHODS

Clinical outcomes and magnetic resonance images of 36 patients with symptomatic lumbar disc herniations, treated conservatively, were analyzed. Patients were divided into three groups: subligamentous, transligamentous, and sequestered herniations. The size of the herniated disc was measured by herniation ratio, which is defined as the ratio of the area of herniated disc to that of the thecal sac on the axial view. Factors associated with the natural regression of herniated disc and the successful clinical outcome were explored.

RESULTS

Of the 36 herniated discs, 25 decreased in size. Ten (56%) of 18 subligamentous herniations, 11 (79%) of 14 transligamentous herniations, and all 4 (100%) sequestered herniations were reduced in size. The average decreases in herniation ratio of the subligamentous, transligamentous, and sequestered disc groups were 17%, 48%, and 82% respectively. The decrease in herniation ratio was related to the presence of transligamentous extension but was not related to the initial size of herniation. Successful outcome correlated with a decrease in herniation of more than 20%.

CONCLUSION

Transligamentous extension of herniated disc materials through the ruptured PLL is more important to its reduction in size than is the initial size of the herniated disc. Decrease in herniation ratio of more than 20% seems to correspond to successful clinical outcome.

Involvement of bone morphogenic protein-2 (BMP-2) in the pathological ossification process of the spinal ligament

OBJECTIVE

To investigate the function of bone morphogenic protein-2 (BMP-2) in the ossification of the spinal ligament (OSL).

METHODS

Total RNA was prepared from the cultured spinal ligament cells from patients with OSL and analysed by reverse transcription-polymerase chain reaction using specific primers for BMP-2. BMP-2 mRNA expression in ligament tissues was examined by in situ hybridization. Spinal ligament cells from patients without OSL were treated with BMP-2 and examined for alkaline phosphatase activity.

RESULTS

Expression of the BMP-2 gene was detected in cultured spinal ligament cells. In ligament tissues, BMP-2 mRNA was present in the chondrocyte-like cells in the fibrocartilage zone. Exogenous BMP-2 increased alkaline phosphatase activity in spinal ligament cells from patients without OSL.

CONCLUSION

The BMP-2 gene is expressed in the spinal ligaments of OSL patients, and exogenous BMP-2 stimulates osteogenic differentiation of spinal ligament cells. The expression of BMP-2 in the spinal ligaments could be a clue in elucidating how heterotrophic osteogenesis develops in ligament tissue.

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

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To investigate the progression pattern of ossification of the posterior longitudinal ligament (OPLL) after cervical laminoplasty.

SUMMARY OF BACKGROUND DATA

OPLL is a progressive disease, and an increased area of ossification affects the surgical results after laminoplasty. However, it is uncertain how the ossification area progresses with time after surgery.

METHODS

Fifty-five patients who were available for serial radiographs of more than 5 years were included. The extent of ossification in the longitudinal axis was assessed using computer software. The associations between the progression of OPLL and the clinical and radiologic data were analyzed.

RESULTS

Forty-one patients had OPLL progression. The patients were divided into three groups according to the pattern of progression. Group 1 consisted of patients 40 to 49 years of age with continuous or mixed type, showing slow progression at the beginning, then fast. Group 2 consisted of patients older than 50 years with continuous or mixed type, showing rapid progression at the beginning and then slow. The patients in Group 3 had segmental type with no or slight progression.

CONCLUSIONS

We speculated that the progression of OPLL decreases as the patient ages. These findings will be important for the management of patients with OPLL after surgery.

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.

Magnetic resonance imaging findings in ossification of the posterior longitudinal ligament of the cervical spine

OBJECT

Because of the lack of magnetic resonance (MR) signal from cortical bones, MR imaging is inadequate for diagnosing ossified lesions in the spinal canal. However, MR imaging provides important information on spinal cord morphology and associated soft-tissue abnormality. The purpose of this study is to determine the role of MR imaging in the diagnosis and treatment of patients with ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

METHODS

The authors reviewed MR imaging findings in 42 patients with cervical OPLL who were examined with a superconducting MR imaging system. The types of OPLL reviewed included eight cases of continuous, 21 cases of segmental, and 13 cases of the mixed type. All patients were treated surgically either by anterior (26 cases) or posterior decompression (16 cases).

CONCLUSIONS

The T1-weighted images clearly demonstrated the spinal cord deformity caused by OPLL. Associated disc protrusion was found to be present at the maximum compression level in 60% of the patients in this series. The highest incidence of disc protrusion (81%) was found in patients with segmental OPLL. Intramedullary hyperintensity on T2*-weighted imaging was noted in 18 patients (43%). The neurological deficits observed in these 18 patients were significantly more severe than those observed in the other 24 patients. Postoperative MR imaging revealed improvement in the spinal cord deformity, although the intramedullary hyperintensity was still observed in most cases. The present study demonstrates the importance of associated disc protrusion in the development of myelopathy in patients with cervical OPLL. Magnetic resonance imaging findings may be used to help determine the actual levels of spinal cord compression and to suggest the method of surgical treatment.

Spinal fractures and pseudoarthrosis complicating ankylosing spondylitis: MRI manifestation and clinical significance

PURPOSE

To analyze magnetic resonance (MR) patterns of fractures and pseudoarthrosis of the ankylosing spondylitic spine, and related changes in the dura and adjacent soft tissue.

MATERIALS AND METHODS

Sixteen patients with radiographically evident fractures or pseudoarthrosis of the spine were included. Each underwent MR studies. Ten patients among them underwent surgical operations.

RESULTS

Both transdiscal (n = 12) and transvertebral (n = 4) fractures were identified. The levels were located from T9 to L3. Five of 16 patients had pseudoarthrosis. The fractures or pseudoarthrosis had two patterns: low signal on T1-and high signal on T2-weighted images, and low signal on both T1-and T2-weighted images. Disruption of anterior longitudinal ligament (ALL) was identified in 14 patients. Seven patients had vertebral translation, all had disruption of the ALL. Dural adhesions were noted in five patients and manifested as linear epidural enhancements with triangular blunt edges.

CONCLUSION

MR patterns of ankylosing spondylitis are important in evaluating complications of fractures or pseudoarthrosis, as well as changes in dura, soft tissue, and ligaments.

Course of nonsurgical management of burst fractures with intact posterior ligamentous complex: an MRI study

STUDY DESIGN

Prospective study.

OBJECTIVES

To evaluate the results of nonsurgical management of burst fractures with intact posterior ligamentous complex and to investigate the effect of trauma and/or residual kyphotic deformity on adjacent and next adjacent (neighboring) discs.

SUMMARY OF BACKGROUND DATA

Conservative treatment based on integrity of posterior ligamentous complex is controversial, probably because of poor evaluation by clinical and indirect radiographic findings. Degenerative changes in the adjacent discs due to trauma and/or residual kyphotic deformity is a common expectation.

MATERIAL AND METHODS

Fifteen consecutive patients who were intact neurologically with burst fractures (T11-L2) were treated nonsurgically with the indication based solely on the integrity of posterior ligamentous complex determined by MRI. Correction of deformity and stabilization with a total body cast under sedation were the mainstays of treatment. Patients were mobilized the next day, and casts were removed at the end of the third month follow-up period with no further external stabilization. Local kyphosis angle, sagittal index, and percent of compression of anterior body height were measured on pretreatment, post-treatment, third month, and latest follow-up radiographs. All of the preoperative and latest follow-up MRI studies of the patients were obtained to examine the discs adjacent and next adjacent to the fractured levels. The self-reported perceptions of the patients of function, pain and appearance were analyzed using the Likert Questionnaire.

RESULTS

There were eight female and seven male patients with an average age of 28 (range, 15-49) years. Average follow-up period was 31 (range, 24-51) months. Average local kyphosis angle was found to be 16.5 degrees (0-34 degrees ) after trauma. It was corrected to 5 degrees (range, 19-25 degrees ) and deteriorated to 14.6 degrees (range, 2-25 degrees ) at the third month and to 17 degrees (range, 2-29 degrees ) at the final follow-up review. There was a similar tendency for both sagittal index and percent anterior body height. The pretreatment MRI analysis revealed changes in the shape of the discs (narrowing or herniation into the body) with no change in the signal intensity of nucleus pulposus in eight of the cranial and four of the caudal adjacent discs. On follow-up MRI, there was only one intact disc with a normal shape cranially. All others had height loss, but only one had complete loss of signal intensity. Caudally, two additional discs had changes in shape without any gross changes in signal intensity of nucleus pulposus, whereas two had changes in signal intensity without change in shape. Only two of the next adjacent discs had changes in shape or signal intensity at the time of injury or at latest follow-up review. Average score of function, pain, and appearance were 3.9 (range, 3-5), 3.7 (range, 2-5), and 3.7 (range, 2-5), respectively, at the latest follow-up review. All patients were back at work in 3.6 (range, 1-9) months on average and all were satisfied with their treatment.

CONCLUSIONS

The present study revealed that an intact posterior ligamentous complex might not prevent loss of correction gained by nonsurgical management of burst fractures. Significant loss occurs in the first 3 months despite external stabilization. However, the magnitude of residual deformity usually remains close to the initial deformity. Although changes in the shape of adjacent discs occur due to trauma and/or natural course, significant loss in signal intensity of nucleus pulposus is unlikely. Patient outcome seems to be highly satisfactory despite residual deformity.

Ganglion cyst of the posterior longitudinal ligament causing lumbar radiculopathy: case report

We describe a man aged 26 years who presented with a neurological syndrome, which was found on lumbar radioculopathy to be due to a ganglion cyst originating from the posterior longitudinal ligament. Based on MRI findings, cystic lesion was suspected, a round lesion at L4 level with no connection to the adjacent facet or to the dura matter. During surgery, a liquid-containing cystic lesion was found to originate from the posterior longitudinal ligament at L4 level. The resected cyst was diagnosed histologically as a ganglion cyst. A complete cure was established after surgery and no recurrence was noted at a follow-up 1.7 years postoperatively. A ganglion cyst of the posterior longitudinal ligament should be considered in the differential diagnosis of a cyst in the lumbar region causing neurological complications.

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

STUDY DESIGN

To establish the diagnosis of dural penetration on preoperative computed tomographic studies of the cervical spine in patients with ossification of the posterior longitudinal ligament (OPLL).

OBJECTIVES

To define before surgery the pathognomonic computed tomographic findings of OPLL extending to and through the dura.

SUMMARY OF BACKGROUND DATA

On preoperative computed tomographic studies, Hida et al have described the single-layer sign characterized by a solid mass of hyperdense OPLL and the double-layer sign defined by two (anterior and posterior) ossified rims surrounding a central nonossified but hypertrophied posterior longitudinal ligament. Only 1 of the 9 patients exhibiting the single-layer sign but 10 of 12 patients showing the double-layer sign had no separate dural plane identified at surgery.

METHODS

Only 2 of 54 patients undergoing multilevel cervical circumferential OPLL procedures had absent dura at surgery. Computed tomographic examinations for all patients were retrospectively reviewed to determine unique signs of dural penetration.

RESULTS

Dura was absent in 1 of 12 patients who had the single-layer CT sign that was additionally characterized by an irregular C angular configuration. Only 1 of 4 patients exhibiting the double-layer computed tomographic sign had absent dura at surgery. The remaining 38 patients had the smooth-layer sign, characterized by more regular margins of classic (22 patients) or early OPLL (16 patients).

CONCLUSIONS

The double-layer computed tomographic sign is more pathognomonic for dural penetration than the single-layer sign. The smooth-layer sign, indicating a clean dural plane, is more typical in North American patients.

MicroRNA-181 regulates the development of Ossification of Posterior longitudinal ligament via Epigenetic Modulation by targeting PBX1

Objectives: Ossification of the posterior longitudinal ligament (OPLL) presents as the development of heterotopic ossification in the posterior longitudinal ligament of the spine. The etiology of OPLL is genetically linked, as shown by its high prevalence in Asian populations. However, the molecular mechanism of the disease remains obscure. In this study, we explored the function and mechanism of OPLL-specific microRNAs. Methods: The expression levels of the ossification-related OPLL-specific miR-181 family were measured in normal or OPLL ligament tissues. The effect of miR-181a on the ossification of normal or pathogenic ligament cells was tested using real-time polymerase chain reaction (PCR), Western blot, alizarin red staining and alkaline phosphatase (ALP) staining. The candidate targets of miR-181 were screened using a dual luciferase reporter assay and functional analysis. The link between miR-181a and its target PBX1 was investigated using chromatin immunoprecipitation, followed by real-time PCR detection. Histological and immunohistochemical analysis as well as micro-CT scanning were used to evaluate the effects of miR-181 and its antagonist using both tip-toe-walking OPLL mice and in vivo bone formation assays. Results: Using bioinformatic analysis, we found that miR-181a-5p is predicted to play important roles in the development of OPLL. Overexpression of miR-181a-5p significantly increased the expression of ossification-related genes, staining level of alizarin red and ALP activity, while the inhibition of miR-181a-5p by treatment with an antagomir had the opposite effects. Functional analysis identified PBX1 as a direct target of miR-181a-5p, and we determined that PBX1 was responsible for miR-181a-5p's osteogenic phenotype. By chromatin immunoprecipitation assay, we found that miR-181a-5p controls ligament cell ossification by regulating PBX1-mediated modulation of histone methylation and acetylation levels in the promoter region of osteogenesis-related genes. Additionally, using an in vivo model, we confirmed that miR-181a-5p can substantially increase the bone formation ability of posterior ligament cells and cause increased osteophyte formation in the cervical spine of tip-toe-walking mice. Conclusions: Our data unveiled the mechanism by which the miR-181a-5p/PBX1 axis functions in the development of OPLL, and it revealed the therapeutic effects of the miR-181a-5p antagomir in preventing OPLL development both in vivo and in vitro. Our work is the first to demonstrate that microRNA perturbation could modulate the development of OPLL through epigenetic regulation.