The interspinous ligament of the lumbar spine. Magnetic resonance images and their clinical significance

STUDY DESIGN: A preliminary study of magnetic resonance features of the interspinous ligament in degenerative lumbar spine. OBJECTIVES: To classify the magnetic resonance imaging features of the interspinous ligaments in relation to the patient's age, disc degeneration, and radiographic instability. Magnetic resonance imaging also was correlated with the histologic findings of the interspinous ligaments. SUMMARY OF BACKGROUND DATA: As reported, rupture of the interspinous ligament frequently is found in the degenerative lumbar spine. However, little information is available in the literature on imaging assessment of the interspinous ligament in degenerative lumbar disorders. METHODS: In this study, 24 interspinous ligaments at L1-L2 or L2-L3 from 15 patients with nondegenerated discs were selected to represent normal magnetic resonance features of the interspinous ligament, and 38 patients with the mean age of 49 years underwent functional radiography and magnetic resonance imaging. The magnetic resonance features of the interspinous ligament were classified into five categories according to their signal intensities: Type 1A (low intensity on T1- and T2-weighted images without hypertrophy of the spinal process); Type 1B (same signal pattern as in Type 1A with hypertrophy of spinal process); Type 2 (low intensity on T1- and high intensity on T2-weighted images); Type 3 (high intensity on T1-weighted images); and Type 4 (others). Seven patients with variable patterns of the interspinous ligament were selected to undergo histologic examinations. RESULTS: Of the interspinous ligaments considered normal, 80% were classified as Type 1A. There were 14 Type 1A, 30 Type 1B, 19 Type 2, 16 Type 3, and 20 Type 4 ligaments. The mean age and disc degeneration grade of the patients with the Type 1B ligaments was significantly higher. Instability was found to be associated with Type 2 interspinous ligaments (7 of 19), whereas instability rarely was noted in Types 1A (1 of 14) and 1B (1 of 30) ligaments. The histologic examination revealed that chondrometaplasia and necrotization of fiber bundle predominated in Type 1B, proliferation of cells and vascular invasion in Type 2, fatty degeneration in Type 3 ligaments. CONCLUSIONS: The magnetic resonance imaging characteristics may be helpful in assessing normal or pathologic changes in the interspinous ligaments.     

Effects of aging and spinal degeneration on mechanical properties of lumbar supraspinous and interspinous ligaments.

BACKGROUND CONTEXT: The effects of aging and spinal degeneration on the mechanical properties of spinal ligaments are still unknown, although there have been several studies demonstrating those of normal spinal ligaments. PURPOSE: To investigate the mechanical properties of the human posterior spinal ligaments in human lumbar spine, and their relation to age and spinal degeneration parameters. STUDY DESIGN/SETTING: Destructive uniaxial tensile tests were performed on the human supraspinous and interspinous ligaments at L4-5 level. Their mechanical properties were compared with age and spinal degeneration using several imaging modalities. PATIENT SAMPLE: Twenty-four patients with lumbar degenerative diseases on whom posterior surgeries were performed, with the age ranging from 18 to 85 years. OUTCOME MEASURES: The ultimate load and elastic stiffness as structural properties, the degree of disc degeneration, range of segmental motion, the disc height, disc space narrowing ratio and degree of facet degeneration as the parameters of spinal degeneration. METHODS: Twenty-four supraspinous and interspinous ligaments at the L4-5 level were obtained from posterior surgeries of patients with lumbar degenerative disease. The mechanical tests of bone-ligament-bone complexes were performed in a uniaxial tensile fashion with a specially designed clamp device. The ultimate load and elastic stiffness were calculated as structural properties. The degree of disc degeneration, range of segmental motion, the disc height, disc space narrowing ratio and degree of facet degeneration were examined by using radiographs, computed tomography and magnetic resonance imaging. RESULTS: The average and SD value of ultimate load, elastic stiffness, tensile strength and elastic modulus were 203+/-102.9 N, 60.6+/-36.7 N/mm, 1.2+/-0.6 Mpa and 3.3+/-2.1 Mpa, respectively. A significant negative correlation was found between age and tensile strength (p= 0.02). The specimens with facet degeneration showed lower values in tensile strength and elastic modulus than those without facet degeneration (p<0.04). However, no correlation was found between disc-related parameters and tensile strength. CONCLUSIONS: The mechanical strength of human lumbar posterior spinal ligaments decreases with age and facet degeneration, particularly in the ligament substance.     

Some new observations on the functional anatomy of the lower cervical spine.

The ligaments are a major stabilizing component of the cervical spine and are critical for spinal stability as well as stabilization therapy. Relatively little information is available on the anatomic details and function of the cervical ligaments. Fifteen fresh cervical spines were dissected and the ligaments examined grossly and functionally. Eight different intrinsic ligaments of the lower cervical spine were identified. The largest and most rigid of these are the annulus fibrosus, posterior longitudinal ligament, and capsular ligament. By virtue of their size and certain biomechanical observations, these ligaments stabilize the cervical spine. The other ligaments play a more specialized and secondary role. The intertransverse ligaments, although thin and frail, are consistently found and appear to limit rotation and lateral bending, the anterior longitudinal ligament limits extension and the interspinous and supraspinous ligaments limit spinal flexion. Under physiologic conditions, the elastic ligamentum flavum permits extension of the spine without impinging upon the spinal cord or nerve roots. As a group, the ligaments of the cervical spine control motion within finite limits without jeopardizing spinal cord or nerve root function.     

Biomechanical analysis of the disc adjacent to posterolateral fusion with laminectomy in lumbar spine

OBJECTIVES: After posterolateral fusion with laminectomy for the degenerative lumbar spine, accelerated degeneration of the disc adjacent to the fusion mass has been clinically observed. Previous studies used a finite element model (FEM) to calculate the stress of the adjacent disc in the fused lumbar spine with spinal fixator and bone graft. However, little emphasis was placed on the simultaneous spinal fusion and decompression procedure. To investigate if the spinal decompression procedure in posterolateral fusion would increase stress significantly, the FEM was employed to estimate the stress concentration of the disc above the fusion mass in posterolateral fusion with laminectomy and hemilaminectomy. METHODS: Three FEMs of the lumbar spine were established: intact spine, posterolateral fusion with total laminectomy, and posterolateral fusion with hemilaminectomy (preserved partial lamina, spinous process, and supraspinous and interspinous ligaments). The posterolateral fusion added spinal fixator and bone graft between the transverse process. The L1 vertebral body was subjected to 10-Nm flexion, extension, torsion, and lateral bending. The bottom of the L5 vertebral body was fixed. RESULTS: In flexion, the stress on the adjacent disc in posterolateral fusion with laminectomy and hemilaminectomy respectively increased 90% and 21% over that of the intact spine. In posterolateral fusion with hemilaminectomy, the supraspinous and interspinous ligaments shared some external forces to alleviate the stress concentration of the adjacent disc. However, in extension, torsion, and lateral bending, these two fusion models had almost no change in range of motion and stress of adjacent disc. CONCLUSION: Posterolateral fusion with hemilaminectomy (preserved partial lamina, spinous process, and supraspinous and interspinous ligaments) was able to alleviate the stress concentration of the disc above the fusion mass in flexion.     

腰椎退行性滑脱与棘间韧带MRI的T2WI高信号相关性分析

目的:探讨腰椎退行性滑脱与MRI棘间韧带T2WI高信号之间的关系,以提高对棘间韧带信号改变的认识。方法:收集2018年3月至2020年3月临床诊断为腰椎退行性滑脱43例患者的MRI资料,男19例,女24例,年龄50~92岁,平均69岁。利用影像归档和通信系统(picture archiving and communication systems,PACS)调阅影像,记录滑脱节段与非滑脱节段棘间韧带出现T2WI高信号的分布情况和发生率,利用Spearman分析棘间韧带的T2WI高信号与腰椎滑脱程度的关系。结果:除8条韧带因图像显示不佳未计入统计结果外,43例患者共207个腰椎椎体和相应的棘间韧带入组研究。根据Meyerding分型法,43例患者共有48个节段出现滑脱,Ⅰ度滑脱41个节段,Ⅱ度滑脱7个节段。滑脱节段对应的棘间韧带出现T2WI高信号30例,其中L_2,3节段3例,L_3,4节段3例,L_4,5节段20例,L5S1节段4例;159个非滑脱节段对应的棘间韧带出现T2WI高信号53例,其中L1,2节段6例,L_2,3节段6例,L_3,4节段13例,L_4,5节段7例,L₅S₁节段21例。滑脱节段与非滑脱节段相比,棘间韧带T2WI高信号的发生率分别为62.5%和33.3%,差异有统计学意义(χ²=13.06,P<0.05)。Spearman相关分析显示棘间韧带T2WI高信号的出现与腰椎滑脱程度呈正相关(r=0.264,P<0.05)。结论:退行性腰椎滑脱患者中滑脱椎体的棘间韧带出现T2WI高信号更多见,T2WI高信号的出现与椎体滑脱的程度呈正相关,在影像诊断中应引起足够重视。     

Ultrastructure of the human interspinous ligament and ligamentum flavum. A preliminary study

The ultrastructure of ligamenta flava (LF) and interspinous ligaments (ISL) obtained from four patients who underwent surgery for vertebral fracture (control group) and five patients operated for disc herniation was studied. The fine structure of LF was composed of elastic and elaunin fibers. Small diameter collagen fibrils were found between the elastic system fibers. The ISL was constituted predominantly of collagen fibrils. Elastic fibers were seen in the most ventral part of the ligament. In ISL and LF of the control group, the cells were fibroblastic-like cells. Chondrocytes were present only near their attachment sites. The proteoglycans were demonstrated between the collagen fibrils, and they appeared to form a regular interfibrillar linking. In ligaments obtained from patients with disc herniation, several modifications were found. The fibroblasts transformed into chondrocytic cells, which were surrounded by a pericellular matrix rich in proteoglycan filaments. A few cells that had suffered necrosis were found. Alterations in the collagen-proteoglycans arrangement also were evidenced. The proteoglycan filaments were randomly oriented to the collagen fibrils.     

Role of the capsulo-ligamentous structures in rotation and combined flexion-rotation of the lumbar spine.

We carried out experiments on whole cadaveric lumbar spines in order to determine the role that each of the capsulo-ligamentous structures play in axial rotation in the neutral position and in the flexed position. Eight specimens were first tested intact, then after division of all the apophyseal joint capsules between L1 and the sacrum. Another five specimens were also first tested intact, then after division of the supra- and interspinous ligaments and yellow ligament, and finally after cutting the posterior longitudinal ligament and posterior annulus at each level as well. The results show that there is considerable variation in the axial rotation of the lumbar vertebrae within the same spine and across different spines. The apophyseal joint capsules limit rotation both in neutral and flexed positions. In flexion, the amplitude of rotation in the lumbar spine is reduced. Of the capsulo-ligamentous structures, it is the posterior annulus and the posterior longitudinal ligament that seem to play the more important role in limiting axial rotation while the spine is flexed.     

Anatomical study of the yellow ligament of the spine with special reference to its ossification

In thoracolumbar spine, the interlaminar and the capsular portion of the yellow ligament differed in their location and direction of elastic fibers. However, the capsular portion in most cervical spines were not considered to represent elastic tissues. At the ligament-osseous junction (enthesis) in the thoracolumbar spine, decreased elastic fibers, hyalinized collagen fibers, emergence of fibrocartilaginoid cells and intra-ligamentous calcification were noted. In the cervical spine and in part of the thoracolumbar spin, however, elastic fibers were close to the bony tissue partially penetrating it without the above-mentioned histological findings. Small ossification in the yellow ligament of a cadaver was considered to be "degenerative enthesopathy (enthesophyte)" originating from "enthesis". But in operative cases, the ossification had the same direction and location as those of the small ossification seen in a cadaver, but endogenous factors were strongly suggested because of the extensive change in matrix prior to ossification.     

The pisotriquetral joint: anatomic, biomechanical, and radiographic analysis

PURPOSE: To examine anatomically and radiographically the ligaments stabilizing the pisotriquetral (PT) joint and to determine the contribution of each ligament to the stability of this joint. METHODS: Twelve cadaver arms were used. The study had 3 components: (1) anatomic dissection of the PT joint ligaments and patterns of degenerative changes, (2) biomechanical sequential sectioning of the supporting ligaments, and (3) radiographic assessment of PT joint motion in several planes both before and after ligament sectioning. RESULTS: The ligaments that attached to the pisiform were the pisometacarpal (PM), pisohamate (PH), radial PT, ulnar PT, and transverse carpal ligament. The PH ligament was shorter, wider, and thicker than the PM ligament. The transverse carpal ligament attachment in the pisiform was insubstantial. In 10 limbs degenerative changes were present, most of them peripheral. Biomechanical testing showed that the primary stabilizers of the PT joint were the PM, PH, and ulnar PT ligaments and that these were responsible for resisting proximal, ulnar, and radial forces, respectively. The PH distance increased along with the pisiform sagittal motion during wrist flexion on oblique x-rays after transection of the PM and ulnar PT ligaments. Concomitantly this distance decreased on the anteroposterior x-rays during radial deviation. The PH distance increased along with the pisiform frontal motion after transection of the PH and radial PT ligaments. CONCLUSIONS: The pisiform ligament complex has primary and secondary stabilizers to the PT joint. The primary stabilizers are the PH, PM, and ulnar PT ligaments. The transverse carpal and radial PT ligaments are secondary stabilizers. Injuries of the primary stabilizers of the PT joint may lead to instability that predisposes to degenerative joint disease.     

Elastic fiber depletion in the supporting ligaments of the gastroesophageal junction: a structural basis for the development of hiatal hernia

BACKGROUND: The position of the gastroesophageal junction is maintained by a complex of fibroelastic ligaments. The purpose of this study was to characterize and compare the histology of these ligaments in patients with gastroesophageal reflux disease (GERD) and hiatal hernia (HH) versus GERD alone, with emphasis on the elastin morphology. STUDY DESIGN: Thirteen patients were examined at the time of laparoscopic fundoplication for symptomatic GERD; nine had no significant HH and four had large diaphragmatic hernias (GERD/HH). Tissue biopsies were obtained from the gastrohepatic ligament (GHL, n=5 and n=3, GERD and GERD/HH, respectively), the phrenoesophageal ligament (n=7 and n=4, respectively), and the gastrophrenic ligament (n=6 and n=4, respectively). Sections of fixed tissue were stained with hematoxylin and eosin, Masson's trichrome, and resorcin-fuchsin for analysis of elastic fibers by light microscopy, and elastin area was quantified and expressed as a percentage of the imaged tissue. RESULTS: Elastin and collagen fibers were prominent in all ligaments in patients with GERD alone. In patients with GERD/HH, there was fragmentation and distortion of elastin in the phrenoesophageal ligament and gastrohepatic ligament, and to a lesser degree, in the gastrophrenic ligament. Compared with patients with GERD alone, the presence of hiatal hernia was associated with a reduction in elastin area by more than 50% in the phrenoesophageal ligament ([mean +/- SEM] 31.0%+/-3.3% versus 15.1%+/-1.3%, p < 0.01) and gastrohepatic ligament (26.9% +/- 0.5% versus 12.5%+/-0.1%, p < 0.008). There was no decrease with respect to elastin in the gastrophrenic ligament. CONCLUSIONS: The periesophageal ligaments in patients with GERD are characterized by prominent elastic fibers. In contrast, GERD/HH is associated with depletion of elastic fibers in two of three ligaments supporting the gastroesophageal junction. Elastic fiber depletion in the periesophageal ligaments thereby provides a structural basis for the development of HH. It remains unclear if this represents a primary (etiologic) alteration or if it is a secondary phenomenon.     

MRI classification of interspinous ligament degeneration of the lumbar spine: intraobserver and interobserver reliability and the frequency of disagreement

Posterior spinal ligament pathology is becoming increasingly recognized as a significant cause of low back pain. Despite the growing clinical importance of interspinous ligament degeneration in low back pain patients, formal reliability studies for the magnetic resonance imaging (MRI) evaluation of interspinous ligaments have not been performed. We proposed an MRI classification system for interspinous ligament degeneration and conducted a comprehensive reliability and reproducibility assessment. Fifty patients who had low back pain with or without leg discomfort (26 males and 24 females) with a mean age of 48.8 years (range 23–85 years) were studied. The classification for lumbar interspinous ligament degeneration was developed on the basis of the literature using mid-sagittal T1- and T2-weighted images. Three spine surgeons independently graded a total of 200 interspinous ligament levels. Intraobserver and interobserver reliability were assessed by kappa statistics. The frequency of disagreement was also identified. The intraobserver agreement was excellent in all readers (kappa range 0.840–0.901). The interobserver agreement was lower as expected, and was substantial to excellent (kappa range 0.726–0.818). Overall complete agreement was obtained in 87.8% of all interspinous ligament levels. A difference of 1, 2, and 3 grades occurred in 8.1, 3.0, and 1.1% of readings, respectively. This proposed MRI classification of interspinous ligament degeneration was simple, reliable, and reproducible. Its use as a standardized nomenclature in clinical and radiographic research may be recommended.     

Histology of the alar and transverse ligaments.

Seven sets of human transverse and alar ligaments, after tensile testing, and eight corresponding ligaments without testing, were examined histologically with respect to their fiber composition and fiber orientation. Various staining techniques were supplemented by polarized light microscopy. Both the transverse and the alar ligaments consist of collagen fibers, with very few elastic fibers in the peripheral layer. In the central portion of the transverse ligament, the collagen fibers cross each other at an angle of approximately 30 degrees. Close to the dens, the transverse ligaments show on their ventral side a transition into fibrocartilage. Except for the immediate site of failure, no differences became evident between tested specimens and controls. The collagen, as the almost exclusive constituent, together with the fiber orientation determine the mechanical properties of these ligaments. This supports the hypothesis that the ligaments could be irreversibly overstretched or even ruptured when the head is rotated and, in addition, flexed by impact trauma, especially in unexpected rear-end collisions.     

Load-displacement properties of the normal and injured lower cervical spine in vitro

The objective of this study was to determine which discoligamentous structures of the lower cervical spine provide significant stability with regard to different loading conditions. Accordingly, the load-displacement properties of the normal and injured lower cervical spine were tested in vitro. Four artificially created stages of increasing discoligamentous instability of the segment C5/6 were compared to the normal C5/6 segment. Six fresh human cadaver spine segments C4-C7 were tested in flexion/extension, axial rotation, and lateral bending using pure moments of ± 2.5 Nm without axial preload. Five conditions were investigated consecutively: (1) the intact functional spinal unit (FSU) C5/6; (2) the FSU C5/6 with the anterior longitudinal ligament and the intertransverse ligaments sectioned; (3) the FSU C5/6 with an additional 10-mm-deep incision of the anterior half of the anulus fibrosus and the disc; (4) the FSU C5/6 with additionally sectioned ligamenta flava as well as interspinous and supraspinous ligaments; (5) the FSU C5/6 with additional capsulotomy of the facet joints. In flexion/extension, significant differences were observed concerning range of motion (ROM) and neutral zone (NZ) for all four stages of instability compared to the intact FSU. In axial rotation, only the stage 4 instability showed a significantly increased ROM and NZ compared to the intact FSU. For lateral bending, no significant differences were observed. Based on these data, we conclude that flexion/extension is the most sensitive load-direction for the tested discoligamentous instabilities. Received: 12 August 1999/Revised: 15 October 1999/Accepted: 28 October 1999     

颈椎后纵韧带总胶原、Ⅰ型和Ⅱ型胶原含量变化的研究

目的通过测量脊髓型颈椎病患者和正常对照组颈椎后纵韧带总胶原、Ⅰ型和Ⅱ型胶原含量，探讨颈椎后纵韧带在颈椎病发病机制中的意义。方法收集脊髓型颈椎病下位颈椎后纵韧带15例做实验组，同年龄段正常下位颈椎后纵韧带10例做对照组，Weossner法测定2组总胶原含量；酶联免疫吸附法测定Ⅰ型和Ⅱ型胶原含量：HE染色和Masson染色，对比观察后纵韧带的显微结构变化。结果实验组总胶原、Ⅰ型胶原含量低于对照组；实验组Ⅱ型胶原含量较对照组高；实验组Ⅰ型／Ⅱ型胶原比值明显低于对照组，差异有统计学意义（P〈0．05）；病理显示实验组弹力纤维、胶原纤维肿胀，排列紊乱。结论颈椎后纵韧带总胶原、Ⅰ型和Ⅱ型胶原代谢发生紊乱，与颈椎病发生发展有密切关系。     

Quantitative anatomy of cervical spine ligaments. Part II. Middle and lower cervical spine.

The quantitative anatomy of the ligaments of the middle and lower cervical spine was determined from six human cadaveric specimens using stereophotogrammetry. For each of the ligaments--anterior longitudinal, posterior longitudinal, capsular, ligamentum flavum, interspinous, and supraspinous--the origins, lengths, and orientations were defined three-dimensionally. The anterior and posterior longitudinal ligaments were approximately 7.5 mm wide and 12 mm long at levels C3 through T1, whereas only 3.8 mm wide but 23 mm long and 31 mm long at C1-C2, respectively. The capsular ligaments were fairly constant at all levels, oriented posteriorly at approximately 45 degrees to the transverse plane. The ligamentum flavum were relatively constant in width (5 mm), whereas their lengths increased from 5.2 mm at C2-C3 to 8.7 mm at C7-T1. The interspinous ligament was tilted anteriorly 30-40 degrees and was shortest at levels C2-C3 and C3-C4. The supraspinous ligament was more vertically oriented than the interspinous ligament by 15-20 degrees.     

Comparison of structure, mechanical properties, and functions of lumbar spinal ligaments

The organization of collagen in the supraspinous, interspinous, and longitudinal ligaments, as well as the ligamenta flava, in lumbar spines from human cadavers has been investigated by polarized light microscopy, scanning electron microscopy, and x-ray diffraction. These experiments were performed on ligaments in situ, with their bony attachments undisturbed, and on excised ligaments at a range of applied strains. Results were related to the composition (investigated by standard histologic techniques) and gross structures (investigated by light microscopy) of the ligaments. More importantly, the results were related to the mechanical properties of the ligaments, which include stiffness, failure conditions, stress relaxation, and hysteresis. Where necessary, results were supplemented by or compared with those obtained from pig ligaments. Mechanical properties were related to postural changes by ligament strains induced in cadaveric specimens, using results from the literature. Thus, ligament structures could be related to their physiologic functions.     

Lumbar intervertebral disc and ligament deformations measured in vivo

The physiologic deformations of the anterior and posterior margins of the annulus fibrosus and the interspinous ligaments were defined in flexion and extension by accurate measurements taken from lateral roentgenograms of the lumbar spines of 11 normal males. The anterior and posterior disc heights were shown to compress and extend up to 35% and 60%, respectively, while the interspinous distance extended up to 369%. In relation to the known mechanical characteristics in vitro, these deformations implied that the soft-tissue elements were lax or in compression during part of the range of motion. Significantly, the interspinous ligament could be active only in the extremes of flexion. These data provide basic information for further studies of the function of the soft parts of the intervertebral joints.     

Study of the innervation of the spinal ligaments at the lumbar level

The authors studied the innervation of the human lumbar spinal ligaments on cadaver or surgical specimens. In the ligaments annexed to the neural arch and in the posterior longitudinal ligament were found free-ending fibers and amyelinic perivascular fibers. In the anterior longitudinal ligament, coexisting with perivascular fibers were found encapsulated corpuscular formations on the ventrolateral aspect of the junction between the intervertebral disc and vertebral body. These findings comfort the role of the anterior longitudinal ligament in proprioception essential both in static and dynamic function of the spine.     

An anatomic basis for spinal instability: a porcine trauma model

To determine the anatomic basis for spinal instabilities, 16 porcine cervical spine specimens were subjected to a well-defined sagittal plane trauma. The multidirectional instability of each specimen was measured before and after trauma. Detailed anatomic dissections were performed on each traumatized specimen to quantitate the extent of injury to several distinct anatomic structures and columns. Multiple regression models were constructed to determine which anatomic structures and columns correlated best with each multidirectional instability. Flexion instability correlated best with injury to the interspinous/supraspinous ligaments and the ligamentum flavum. Extension instability correlated best with anterior longitudinal ligament and pedicle injury. Axial rotation instability correlated best with anterior disc-end-plate and capsular ligament injuries, while lateral bending instability correlated best with posterior disc-end-plate injuries. Anterior column injuries correlated best with extension, axial rotation, and lateral bending instabilities, while posterior column injuries correlated best with flexion instability. Finally, individual anatomic structural injuries had higher correlations with multidirectional instabilities than did the injuries defined by the anatomic columns.