Mechanism of disc rupture. A preliminary report

Lumbar intervertebral disc herniation is thought to be related to senescent changes in the nucleus pulposus except in rare instances of trauma. This investigation provides the first in vitro model of disc prolapse that reliably ruptures discs under physiologically reasonable stress. Fourteen vertebral motion segments with intact posterior elements were loaded repetitively at 1.5 Hz in a combination of flexion (7 degrees), rotation (less than 3 degrees), and compression (1,334 N) for an average of 6.9 hours (range, 3.0-13.0 hours) in a materials testing machine. Loading was terminated when reaction force leveled off for more than 1 hour. Ten discs failed through annular protrusions, and four failed by nuclear extrusion through annular tears, supporting the hypothesis that intervertebral disc prolapse is peripheral in origin. The annulus fibrosus is the site of primary pathologic change.     

微创手术治疗青少年腰椎间盘突出症的临床分析

目的探讨微创手术治疗青少年腰椎间盘突出症的临床疗效。方法回顾分析应用小切口微创手术治疗青少年腰椎间盘突出症21例。结果术后评分按照Nakai分级标准,优17例,良2例,可2例,差0例,手术优良率近90．5％。结论小切口微创手术治疗青少年腰椎间盘突出症具有组织创伤小、手术出血少、对脊椎稳定性破坏轻微、疗效确实等特点,是一种理想的临床手术方法。     

Patterns of lumbar disc degeneration are different in degenerative disc disease and disc prolapse magnetic resonance imaging analysis of 224 patients

Background contextExisting research on lumbar disc degeneration has remained inconclusive regarding its etiology, pathogenesis, symptomatology, prevention, and management. Degenerative disc disease (DDD) and disc prolapse (DP) are common diseases affecting the lumbar discs. Although they manifest clinically differently, existing studies on disc degeneration have included patients with both these features, leading to wide variations in observations. The possible relationship or disaffect between DDD and DP is not fully evaluated.PurposeTo analyze the patterns of lumbar disc degeneration in patients with chronic back pain and DDD and those with acute DP.Study designProspective, magnetic resonance imaging–based radiological study.MethodsTwo groups of patients (aged 20–50 years) were prospectively studied. Group 1 included patients requiring a single level microdiscectomy for acute DP. Group 2 included patients with chronic low back pain and DDD. Discs were assessed by magnetic resonance imaging through Pfirmann grading, Schmorl nodes, Modic changes, and the total end-plate damage score for all the five lumbar discs.ResultsGroup 1 (DP) had 91 patients and group 2 (DDD) had 133 patients. DP and DDD patients differed significantly in the number, extent, and severity of degeneration. DDD patients had a significantly higher number of degenerated discs than DP patients (p<.000). The incidence of multilevel and pan-lumbar degeneration was also significantly higher in DDD group. The pattern of degeneration also differed in both the groups. DDD patients had predominant upper lumbar involvement, whereas DP patients had mainly lower lumbar degeneration. Modic changes were more common in DP patients, especially at the prolapsed level. Modic changes were present in 37% of prolapsed levels compared with 9.9% of normal discs (p<.00). The total end-plate damage score had a positive correlation with disc degeneration in both the groups. Further the mean total end-plate damage score at prolapsed level was also significantly higher.ConclusionThe results suggest that patients with disc prolapse, and those with back pain with DDD are clinically and radiologically different groups of patients with varying patterns, severity, and extent of disc degeneration. This is the first study in literature to compare and identify significant differences in these two commonly encountered patient groups. In patients with single-level DP, the majority of the other discs are nondegenerate, the lower lumbar spine is predominantly involved and the end-plate damage is higher. Patients with back pain and DDD have larger number of degenerate discs, early multilevel degeneration, and predominant upper lumbar degeneration. The knowledge that these two groups of patients are different clinically and radiologically is critical for our improved understanding of the disease and for future studies on disc degeneration and disc prolapse.     

Effect of anular repair on the healing strength of the intervertebral disc: a sheep model

STUDY DESIGN: The intervertebral disc, in a sheep model, was used to assess the effect of directly repairing three different anular incisions on the subsequent healing strength of the intervertebral disc. OBJECTIVES: To assess whether directly repairing an anular defect, made at the time of lumbar discectomy, could influence the healing rate and strength of the anulus fibrosus. METHODS: Twenty-four sheep underwent a retroperitoneal approach to five lumbar disc levels. An anular incision, followed by partial discectomy was done at each exposed level. Anular incisions used in this study consisted of 1) a straight transverse slit, 2) a cruciate incision, and 3) a window or box excision. Healing strength was measured at three time intervals: 2 weeks, 4 weeks, and 6 weeks. Each anular incision type was performed on 30 lumbar discs, 10 discs in each time interval. Five discs in each time interval underwent direct repair, and five discs were left unrepaired to heal as controls. The sheep were killed at 2, 4, and 6 weeks after surgery. The lumbar spines were removed en bloc, and the intervertebral discs were subjected to pressure-volume testing to assess the anular strength of repaired versus unrepaired disc injuries at each time interval. RESULTS: Statistical analysis was performed to evaluate the effects of healing time, incision technique, and repair on the pressure-volume characteristics of the involved discs. Pressure-volume testing showed trends of stronger healing for repaired discs, but at no time interval was any significant difference found between repaired and nonrepaired anular strength. Of the nonrepaired discs, the box incision was only 40 to 50% as strong as the slit or cruciate incised discs during early healing. CONCLUSION: Direct repair of anular incisions in the lumbar spine does not significantly alter the healing strength of the intervertebral disc after lumbar discectomy.     

Histological changes in aging lumbar intervertebral discs. Their role in protrusions and prolapses

To study the relationships between the changes due to aging in lumbar intervertebral discs and the development of protrusion or prolapse, we carried out histological studies on operative specimens of thirty-one discs, of which twenty-two had been protruded and nine, prolapsed. The specimens were obtained during twenty-nine operations for herniation of a lumbar intervertebral disc in patients who were sixty years old or older. Changes in the anulus fibrosus were more extensive in the nine prolapsed discs than in the twenty-two protruded discs. Of the nine prolapsed discs, myxomatous degeneration, fibrosis, and swollen anular fibers were found in all nine, and cysts were seen in five. Of the twenty-two protruded discs, only five showed myxomatous degeneration; ten, fibrosis; one, a cyst; and sixteen, swollen fibers. For comparison, we also studied specimens that had been obtained at operation from twenty-one other patients, twenty to fifty-nine years old, who had a prolapsed disc. The anulus showed myxomatous degeneration in all twenty-one specimens, cysts in eight, and fibrosis in ten. In addition, we examined 368 autopsy specimens from people who had been between twenty-five and eighty-five years old at the time of death. In many of the subjects who had died in the sixth decade of life or later, we found that the orientation of the inner fiber bundles of the anulus fibrosus was reversed, so that they bulged inward. The reversal appeared to be the result of myxomatous degeneration of the middle fibers of the anulus, atrophy of the nucleus, and narrowing of the disc space. These histological findings suggest explanations for the predominance of protrusions of the nucleus pulposus in patients who are less than sixty years old and of prolapse of the anulus fibrosus in the few patients who are more than sixty years old who have herniation of an intervertebral disc.     

Chemonucleolysis revisited: a prospective outcome study in symptomatic lumbar disc prolapse

OBJECTIVE: This prospective study was carried out to assess the functional outcome in patients with symptomatic lumbar disc prolapse treated by chemonucleolysis (CNL). METHODS: The Oswestry Low Back Pain Disability Index (ODI) was used to assess the pre- and postprocedure functional status of 112 patients with magnetic resonance (MR) scan-proven lumbar disc prolapse treated by CNL. Follow-up was for at least 5 years. RESULTS: Ninety-three of 112 patients (83%) had excellent/good results, whereas 11 of 112 (10%) were unchanged and 8 of 112 (7%) were worse after the CNL. The younger patients with single-level discs at L5-S1 had the most successful outcome. Seventy percent of our patients (25-45 years of age) were gainfully employed with a mean return to work at 12 weeks. CONCLUSIONS: CNL is a good procedure to bridge the gap between conservative treatment and surgery for lumbar disc prolapse. CNL is beneficial in 80% of patients with significant leg symptoms. After careful selection of candidates using MR scans, it is an effective procedure that does not compromise future open surgery, should it be necessary.     

End-plate lesions of the lumbar spine

It has been suggested that the pattern of development and attrition of blood vessels and notochord remnants leaves congenitally weak points in the cartilage disc plates. There is strong presumptive evidence that nuclear prolapse can take place through these weak spots in the cartilage plates to form Schmorl's nodes. It has been postulated that the development of Schmorl's nodes may also lead to anomalies of the vasculature in the end-plates, which may lead to further end-plate lesions. In the present study, we have examined lumbar intervertebral discs and vertebrae from eight specimens with Schmorl's nodes and 12 specimens without nodes. The specimens examined were from individuals ranging in age from 17 to 90 years. The specimens were sectioned at 150 microns, stained, and the percentage of the bone cartilage interface occupied by marrow spaces was measured using a microscope with an ocular micrometer. The specimens with Schmorl's nodes had a significantly greater proportion of disc marrow contacts than did the normal vertebrae.     

False-negative lumbar discograms. Correlation of discographic and histological findings in postmortem and surgical specimens

To investigate the causes of false-negative discograms, 181 lower thoracic and lumbar intervertebral discs that had been removed as part of en bloc specimens during thirty autopsies were studied first by discography and then histologically. Comparison of the results of the two methods showed that if fissures and cysts were present in a degenerated anulus fibrosus, but did not establish continuity between the nuclear cavity and the site of a herniation, the discogram was false-negative. Under these circumstances, the inner fiber bundles of the anulus fibrosus were intact and their orientation was often reversed, so that they bulged inward. This finding suggested that a protrusion or a prolapse of tissue from just the anulus fibrosus might have been developing. Ten of the fifty-seven discs that had such changes in the orientation of the fibers had a histologically proved protrusion or prolapse of the anulus fibrosus. However, the discograms showed protrusion in only six of the ten discs and demonstrated a false-negative result in the other four. The cases of seventy-seven patients in whom discography had been performed and a herniation had been subsequently confirmed at operation were also studied. Fifty-nine of the patients had a protrusion and eighteen had a prolapse of the disc. The discograms were falsely interpreted as negative in 32 per cent (nineteen) of the fifty-nine patients who had a protrusion and in 56 per cent (ten) of the eighteen who had a prolapse. Histologically, the prolapses were interpreted as protrusions of a portion of the anulus fibrosus. It was concluded that false-negative discograms are more frequent when a protrusion or a prolapse involves the anulus fibrosus rather than the nucleus pulposus, and that a negative discogram does not exclude the possibility of extensive degeneration of the anulus fibrosus.     

Origin of lumbar spinal roots and their relationship to intervertebral discs: a cadaver and radiological study

Previous studies on the anatomy of the lumbar spine have not clarified the precise relationship of the origin of the lumbar roots to their corresponding discs or their angulation to the dural sac. We studied 33 cadavers (25 formalin-preserved and eight fresh-frozen) and their radiographs to determine these details. All cadavers showed a gradual decrease in the angle of the nerve root from L1 to S1. The origin of the root was found to be below the corresponding disc for the L1 to L4 roots. In the formalin-preserved cadavers 8% of the L5 roots originated above, 64% below and 28% at the L4/L5 disc. In the fresh cadavers the values were 12.5%, 62.5% and 25%, respectively. For the S1 root 76% originated above and 24% at the L5-S1 disc in the formalin-preserved cadavers and 75% and 25%, respectively, in the fresh cadavers.A herniated disc usually compresses the root before division of the root sleeve. Thus, compression of the thecal sac before the origin of the root sleeve is common for L1 to L5 whereas compression at the root sleeve is common for S1. Our findings are of value in understanding the pathophysiology of prolapse of the disc and in preventing complications during surgery.     

Transpedicular surgery for dorsolumbar junction disc prolapse: anatomic and biomechanical considerations of a minimally invasive approach.

The dorsal spine is the least affected region of the spine for intervertebral disc prolapse. The majority of cases of thoracic disc prolapse affect the lower dorsal spine, probably due to the increased mobility of that region. The dorsolumbar junction (DLJ) comprises D10 to L1 together with the intervening discs. Over a period of nine years, we have operated on thirty-two DLJ disc prolapses using a transpedicular approach in thirty patients. There were eight cases of D10/D11 disc prolapse, ten of D11/D12, and twelve of D12/L1 prolapse. Two patients had more than 1 level involvement. Back ache was the predominant symptom in patients with DLJ disc prolapse, seen in 92 % of cases. Presentation was in the form of conus/cauda equina syndrome with D11, D12 and L1 radiculopathy. All the patients were evaluated by MRI. Disc prolapse was eccentric in 10 and diffuse central in 22 levels. There was a distinct neurological improvement in all patients after surgery, pain relief being the most prominent feature. The dorsolumbar region differs from the dorsal spine in terms of mobility, anatomic and biomechanical features. It is a transition zone between the relatively fixed dorsal spine and the mobile lumbar region. These differences account for the higher incidence of disc prolapse in the region as compared to the dorsal spine cranial to D10. The transpedicular approach appears to be most suitable for discectomy for DLJ disc prolapse. The approach is minimally invasive considering the size of the incision, minimal bone removal and avoidance of vital structures. Postoperative pain is minimal and ambulation can be begun within 24 hours of surgery.     

The distribution of surface strain in the cadaveric lumbar spine

The fourth lumbar vertebrae and L4-5 discs from six cadaveric lumbar spines were subjected to detailed strain gauge analysis under conditions of controlled loading. With central compression loads, maximal compressive strain was found to occur near the bases of the pedicles and on both superficial and deep surfaces of the pars interarticularis, which emphasises the importance of the posterior elements of lumbar vertebrae in transmitting load. Radial bulge and tangential strain of the disc wall were maximal at the posterolateral surface, in agreement with the fact that disc degeneration and prolapse commonly occur there. Under posterior offset loads simulating extension, both compressive and tensile strains were found to be increased on both surfaces of the pars interarticularis, which suggests that hyperextension may lead to stress fractures and spondylolisthesis. Posterior offset loads also increased the radial bulge of the posterior disc wall and tangential strain at the anterior surface of the disc. Anterior offset loads simulating flexion increased the radial bulge of the anterior disc wall and tangential strain at the posterior surface of the disc. These findings are compatible with movement of the nucleus pulposus within the disc during flexion and extension. This hypothesis was supported by post-mortem discography.     

一氧化氮在突出腰椎间盘中的表达及其意义

目的 :研究一氧化氮 (NO)在突出腰椎间盘组织中的含量及组织学定位 ,并对其意义进行探讨。方法 :对 32例腰椎间盘突出患者的突出间盘组织采取两种方法进行研究 :(1) 12例做体外培养 ,用分光光度法测定培养液上清中NO含量 ;(2 ) 2 0例用免疫组化方法对产生NO的细胞类型及组织学定位进行研究。同时对取自 4具新鲜尸体的 12个正常椎间盘采用相同方法做为对照。结果 :突出腰椎间盘组织产生NO的量为 2 0 0 70± 6 5 5 5nmol/g ,正常对照组的NO量为 76 31± 19 49nmol/ g ,两者统计学有显著性差异 (P <0 0 0 1)。免疫组化结果发现 ,2 0例患者椎间盘组织中一氧化氮合成酶表达阳性 16例 ,12个正常椎间盘组织中无表达阳性细胞。结论 :诱导型一氧化氮合成酶主要由突出椎间盘周围的肉芽组织产生 ,阳性细胞主要以成纤维细胞、软骨细胞及淋巴细胞为主。腰椎间盘可自身合成NO ,NO可能在椎间盘退变中起重要作用 ,突出腰椎间盘中的NO主要由突出腰椎间盘周围的肉芽组织产生。     

Histology of intervertebral disc protrusion: an experimental study using an aged rat model

STUDY DESIGN: In vitro experimental intervertebral disc ruptures of aged rats were examined histologically. OBJECTIVES: To clarify the mechanism of intervertebral disc herniations by microscopic investigation of ruptured discs. SUMMARY OF BACKGROUND DATA: Clinically, disc herniations have been classified into two types: extrusion and protrusion. However, the pathogenesis of protrusion type herniations has not yet been demonstrated by any studies. To clarify this issue, it is essential to establish an appropriate model producing disc herniations, and to examine the sequential changes in the structure of herniated discs. METHODS: Lumbar discs of 2-year-old rats were examined histologically and compared with human lumbar discs. To examine structural changes in discs subjected to repetitive motion stress, 400 repetitions of a sequence of flexion (30 degrees ) and axial rotation (6 degrees ) were applied in vitro to the lumbar discs of the animals. RESULTS: The microstructure of normal lumbar discs in aged rats was similar in many ways to the human lumbar discs in a 20- to 40-year-old adult. Of 10 discs subjected to repetitive stress, 4 were ruptured at the junction between the posterior anulus fibrosus and the sacral cartilage endplate. One had an extruded nucleus pulposus, and three had a protruded anulus fibrosus, which displayed disorganized structure containing widened and flaccid lamellae. CONCLUSIONS: The results from this study indicate that disc protrusion can be caused by disorganization of the ruptured annular lamellae, not by focal compression of the nucleus pulposus.     

Acute increase in lateral bending of the canine lumbar disc following chymopapain injection

Twenty-four lumbar discs in six adult beagle dogs were injected with either 0.1 ml CP (ChymodiactinR) (200 U) (12 discs) or 0.1 ml saline (12 discs) under direct vision at laparotomy. All animals were killed 1 hour later; the lumbar spine was immediately excised en bloc and frozen until biomechanical testing. After overnight thawing, test specimens were prepared and consisted of a disc and half a vertebral body on each side. The posterior elements were discarded. Each motion segment was mounted on a testing plate, with bone cement used for fixation. Lateral bending of the motion segment was tested as an analog to the motion of a disc during correction of a scoliotic spine with a distraction force. Lateral bending forces of 2 kg and 4 kg were applied for 30 minutes each. Lateral bending, creep, and residual deformity (in degrees) were recorded. CP injected disc showed an acute increase in lateral bending of 28% and 26%, respectively (2-kg and 4-kg loads) (P less than 0.001). In addition, CP injected discs showed a 25% increase in their residual angular deformity compared with the control discs (P less than 0.001). No significant changes were noted in creep values between CP and saline injected discs. This study demonstrates a significant acute increase of 28% and 26% in lateral bending of the canine disc following enzyme injection.     

Frequency and specific surgical management of far lateral lumbar disc herniations

Summary Frequency of Far Lateral Lumbar Disc Herniation The analysis of pre-operative computer-assisted tomograms and myelograms in a series of 694 operated lumbar disc herniations showed that a far lateral disc prolapse occured in 7% of the cases. Within the group of those far laterally herniated discs 3% of the herniations were predominantly located in the intervertebral foramen, whereas 4% of the protruded discs were mainly situated extraforaminally compressing the spinal nerve in its paravertebral course.Surgical Management of Extraforaminal Far Lateral Lumbar Disc Herniation By March 1988 40 patients had been operated on for an extraforaminal disc protrusion making use of an external microsurgical exposure (in two cases by a transmuscular approach and in 38 cases via an enlarged midline approach). A medium-term follow-up of these 40 patients revealed a substantial clinical relief of pain in 34 cases (85%). Based on these gratifying results we regard the external exposure of the extraforaminally protruded disc as the treatment of choice.     

老年性腰椎间盘突出症的手术治疗分析

目的探讨老年腰椎间盘突出症的临床特点及手术治疗原则。方法分析54例老年腰椎间盘突出症的临床特点及不同手术方式的远期效果。结果术后随访6个月至3年6个月，优良率占93．8％。结论在老年腰椎间盘突出症的手术中，既要做到充分减压，又要尽可能最大限度地保持脊柱生物力学的稳定性。     

腰椎间盘突出与有无临床症状的影像对照研究

目的：探讨应用区域定位评分法研究腰椎间盘突出（膨出、突出、脱出）有临床症状与无临床症状的相关性及原因分析。方法：将符合要求的CT病理分型为膨出、突出、脱出的体检或住院或门诊患者120例,按有临床症状与无临床症状分为2组,每组按CT病理分型分3组,年龄20-59岁,平均38．5岁,有临床症状与无临床症状两组间在性别、年龄、病程及椎间盘分布节段差异均无统计学意义;应用区域定位评分法对各组评分;用游标卡尺分别测量矢状径指数（SI）、盘黄韧带前间隙、侧隐窝上口宽度、硬膜囊前后径。CT值由X线断层扫描测定,分别测量3次,取平均值。结果：④腰椎间盘突出有临床症状与无临床症状两组在SI、CT值、CT评分、硬膜囊前后径之间差异无统计学意义（P〉0．05）;在侧隐窝上口宽度、盘黄韧带前间隙之间差异有统计学意义（P〈0．05）。②腰椎间盘突出有临床症状与无临床症状两组突出类型比较,差异有统计学意义（P〈0．05）;腰椎间盘脱出有临床症状与无临床症状两组突出节段比较,差异有统计学意义（P〈0．05）。结论：①腰椎间盘突出大小、部位、类型不一定与临床症状存在必然关系,腰椎间盘突出症与压迫程度无正比关系;②椎管内突出髓核是否导致相应的临床症状存在着诸多或必然因素,可能与椎间盘突出物可代偿的椎管储备容量、受累神经根对机械压迫的逃逸避让与弹性延长功能,以及受累神经根低氧消耗与抗缺血性损伤代偿作用等因素有关。     

腰椎转移癌与腰椎间盘突出症的鉴别18例报告

目的：明确腰椎间盘突出症与腰椎转移癌的不同点,以防误诊。方法：对比腰椎间盘突出症与腰椎转移癌的临床表现、辅助检查,找出其不同点。结果;腰椎间突出症与腰椎转移癌临床表现相似,鉴别诊断以ＭＲＩ最有价值。结论：应重视详细的体格检查,对疑有腰椎转移癌可能者,应行ＭＲＩ检查以资鉴别。     

P物质阳性神经纤维在退变腰椎间盘的分布及意义

目的研究P物质（substance P,SP）阳性神经纤维在腰椎间盘中的出现及分布,以探讨其在椎间盘退变中的潜在作用。方法收集16例患者的21个病变腰椎间盘和来自于新鲜尸体的12个正常对照椎间盘,行组织学检查和SP免疫组织化学染色检查。结果SP阳性神经纤维偶见于正常椎间盘,在病变椎间盘内可见较多的SP免疫反应阳性神经纤维分布,阳性神经纤维数量与腰椎间盘退变程度呈正相关。结论腰椎间盘退变程度和SP阳性神经纤维数量有明显的相关性,SP可能作为神经炎性介质加速了腰椎间盘的退变。     

The short-term effects of chymopapain on intervertebral discs

Cadaveric lumbar discs were injected with chymopapain and subjected to a series of mechanical tests over a period of up to 19 hours. Discs from the same spine injected with saline were used as controls. The results showed that chymopapain had no measurable effect on the mechanical properties of the disc apart from the increased height and stiffening caused by fluid injection. Another series of tests on isolated pieces of disc material showed that chymopapain could reduce the size of prolapsed nuclear material by 24% in one hour and by 80% in 48 hours. It is concluded that, in the short-term, chymopapain has a negligible effect on the mechanics of a disc but it can reduce the size of any prolapsed nuclear material with which it comes in contact.