L4-L5 Intervertebral Disc Research Articles

BACK INJURY- VOLLEYBALL

HISTORY A 15 year-old female high school volleyball player incurred a back injury while playing volleyball 11 weeks prior to presentation. She reports tripping and falling while running, striking her head and back. Since her injury, she has experienced persistent lumbar pain with referred pain to her right lower limb, and numbness over the dorsal aspect of her right lower extremity. Coughing, sneezing, and bending at the waist aggravate her lumbar pain, which she describes as deep, sharp, and achy. Various traditional and COX-2 specific ant-inflammatory agents have not relieved her symptoms. She had not undergone formal physical therapy at the time of our evaluation. PHYSICAL EXAMINATION Normal gait pattern without listing. Full lumbar range of motion with painful flexion and extension. The right lumbosacral paraspinal region was tender to palpation. No tenderness was elicited with sacroiliac joint (SIJ) palpation and SIJ provocative maneuvers did not elicit pain. Straight leg raising reproduced lumbar pain on the right side without radicular symptoms. Full pain-free range of motion was noted in the hips, knees, and ankles bilaterally. Manual muscle testing revealed intact strength in both lower limbs, except 4+/5 right great toe extension. Muscle stretch reflexes were +2 bilaterally at the patella, medial hamstrings, and achilles tendons. Sensation was decreased to light touch and pin prick on the dorsal surface of the right foot. Upper motor neuron signs were absent. DIFFERENTIAL DIAGNOSIS Lumbosacral intervertebral disc herniation w/L/S radiculopathy vs. sclerotomal pain referral pattern Lumbosacral strain/sprain Discitis Vertebral osteomyelitis Spondylolysis/spondylisthesis Tumor TESTS AND RESULTS Lumbosacral MRI: – small 1–2mm disc bulge at L1 – L2 w/o central or lateral canal stenosis or neural element compromise – small paracentral disc bulge at L4-L5 toward the right neural foramen abutting but not compressing the right L5 nerve root Electrodiagnostic evaluation: – No electrical evidence of L/S radiculopathy/plexopathy, focal entrapment, or peripheral neuropathy. FINAL/WORKING DIAGNOSIS Right paracentral L4-L5 intervertebral disc protrusion causing a right L5 radiculopathy affecting primarily sensory fibers. TREATMENT AND OUTCOME Prednisone 70mg taper over 7 days; ultracet 1–2 tabs q6 hr prn. Physical therapy with passive modalities including hot packs, ice message, electrical stimulation. Lumbar stabilization program with instructions on proper body posture and mechanics, as well as a home exercise program. Due to lack of benefit from oral steroids and poor tolerance for therapy due to persistent symptoms, a total of three, L5 transforaminal epidural steroid injections were performed under fluroscopy. Resolution of symptoms enabling patient to complete 12 sessions of physical therapy. Continue home exercise program, gradually increasing activity level while wearing a lumbosacral corset. Avoid heavy lifting and high impact activities.

In Vivo Intradiscal Pressure Measurement in Healthy Individuals and in Patients With Ongoing Back Problems

In vivo intradiscal pressure measurement in different postures in healthy individuals and in those with ongoing back problems. With the most recent technique, 1) to analyze the influence of degeneration on the intradiscal pressure, 2) to calculate the spinal load on the L4-L5 intervertebral discs, and 3) to assess the relation between the spinal load and movement of the intervertebral motion segment. Almost all the data on intradiscal pressure are from the studies by Nachemson. The results from these pioneering studies have formed the basis for current knowledge about the in vivo loading conditions of the human spine. Although performed already during the 1960s and 1970s with the technique available at that time, virtually no other similar studies have been performed to corroborate the findings. The intradiscal pressure (vertical and horizontal) was measured using an advanced pressure sensor in 8 healthy volunteers and 28 patients with ongoing low back pain, sciatica, or both at L4-L5. Among other calculations, the actual loading conditions in various body positions were calculated in relation to the angle between the two vertebrae of the studied motion segments. The effect of respiration on intradiscal pressure was shown as a continuously periodic fluctuation in the healthy prone individual. The intradiscal pressure was significantly reduced according to the degree of disc degeneration as estimated by magnetic resonance imaging. There possibly was a difference between the vertical and horizontal pressures in the degenerated and nondegenerated discs because the nucleus pulposus was pressure-tropic property. The spinal load increased in the following order of body positions: prone, 144 N; lateral, 240 N; upright standing, 800 N; and upright sitting, 996N (P < 0.0001). In the standing and sitting body positions, the spinal load increased not only with forward bending, but also with backward bending. The spinal load was highly dependent on the angulation in the motion segment. The movements of the spine from a flexed to an extended position made the load of the spine change in a curvilinear fashion, fitting a squared equation in the standing body position. There was a correlation between the spinal load and the angle of the motion segment in the standing but not in the sitting body position. The spinal load was highly dependent on the angle of the motion segment in normal discs in vivo. The intradiscal pressure in degenerated discs was significantly reduced compared with that of normal discs. However, further studies on the effect of respiratory movement on intradiscal pressure, the difference between vertical and the horizontal pressures, and the difference in the spinal load between standing and the sitting body positions are necessary. The data obtained from the current study are fundamental to understanding the pathomechanisms and biomechanical problems of disc disease.

Sensory innervation of the dorsal portion of the lumbar intervertebral disc in rats.

The vertebral levels of dorsal root ganglia innervating the dorsal portion of the L5-L6 intervertebral disc were investigated in rats using a retrograde transport method. The pathways and functions of nerve fibers supplying the dorsal portion of the disc were determined by denervation and immunohistochemistry. The dorsal portion of the lumbar intervertebral disc has been reported to be innervated segmentally, but anesthetic block of the paravertebral sympathetic trunks and the L2 spinal nerve can relieve discogenic low back pain. In the current study, the sensory innervation of the dorsal portion of the L5-L6 intervertebral disc was investigated, because the disc anatomically corresponds to the L4-L5 disc in humans, and the dorsal portion of the human L4-L5 disc is frequently subject to injury that causes low back pain. A retrograde transport of Fluoro-Gold (F-G; Fluorochrome, Denver, CO) was used. Subjects included nontreated control (n = 32) and sympathectomized rats in which paravertebral sympathetic trunks were removed from L2 to L3 (n = 9). In a ventral approach, Fluoro-Gold crystals were placed on the dorsal portion of the L5-L6 disc, and labeled neurons in the bilateral dorsal root ganglia from T10 to L6 were counted. Fluoro-Gold crystals did not leak from the dorsal portion of the L5-L6 disc in 14 of the 32 nontreated rats and in 5 of the 9 sympathectomized rats. These rats were used for analysis. Fluro-Gold-labeled neurons were found in dorsal root ganglia from T13 to L6 in the 14 control rats but only from L2 to L6 in the 5 sympathectomized rats. The dorsal portion of the L5-L6 disc of rats was shown to be multisegmentally innervated by the T13 to L6 dorsal root ganglia. The sensory fibers from T13, L1, and L2 dorsal root ganglia were shown to innervate the dorsal portion of the L5-L6 disc through the paravertebral sympathetic trunks. In contrast, those from the L3-L6 dorsal root ganglia may innervate the dorsal portion of the L5-L6 disc through the sinuvertebral nerves.

Peridiscal vascular anatomy of the lower lumbar spine. An endoscopic perspective.

An analysis of the vascular anatomy relative to the underlying discs in the lower lumbar spine performed by using radiologic studies. To define better the vascular anatomy of this region from the perspective of the endoscopic spine surgeon, and to draw conclusions regarding surgical accessibility of the lower lumbar intervertebral discs. Cadaveric studies have highlighted the high degree of anatomic variability among the vascular structures overlying the anterior elements of the lower lumbar spine. An endoscopic approach to the intervertebral disc at these levels often is limited by arterial or venous structures. The growth of laparoscopic techniques to approach the intervertebral disc has renewed interest in the vascular anatomy of this region. A computer-generated series of abdominal vascular studies performed for unrelated indications were scrutinized to ensure clear demarcation of the overlying vascular structures and underlying bony anatomy of the lumbar spine in a true anteroposterior plane. For analysis, 21 arterial (abdominal angiograms) and 22 venous (venograms) studies were selected. For the arterial data, level of aortic bifurcation and course of common iliac vessels were determined. The venous data were analyzed in a similar manner using the confluence of the common iliac veins as the major landmark. To draw conclusions about anterior surgical accessibility of the disc, the location of vessels was measured with respect to intervertebral disc spaces. The bifurcation level of the abdominal aorta was quite variable, occurring anteriorly to the L3 vertebral body in 3 of 21 studies (14%), and anteriorly to L4 and L5 in 10 (48%) and 7 (38%) of the studies, respectively. The cranial half of L5 was the most common single area of bifurcation (in one third of the studies). Venous anatomy was more consistent, with 86% of the patients displaying an iliac vein confluence at L5, and 14% having a confluence overlying L4. From an arterial perspective the L3-L4, L4-L5, and L5-S1 discs were readily accessible in 10%, 38%, and 95% of the studies, respectively. From a venous perspective, these levels were accessible in 100%, 73%, and 60% of the studies, respectively. The results of this study suggest that a laparoscopic approach to the L3-L4 intervertebral disc will seldom be accomplished without significant retraction of the aorta. Access to the L4-L5 space will be accomplished readily in approximately one third of the patients. In the others, it will require significant vascular dissection. The L5-S1 space, conversely, will be readily accessible by the authors' definitions without significant vessel dissection in the majority of patients.

Sensory nerve fibres from lumbar intervertebral discs pass through rami communicantes. A possible pathway for discogenic low back pain.

It has been thought that lumbar intervertebral discs were innervated segmentally. We have previously shown that the L5-L6 intervertebral disc in the rat is innervated bilaterally from the L1 and L2 dorsal root ganglia through the paravertebral sympathetic trunks, but the pathways between the disc and the paravertebral sympathetic trunks were unknown. We have now studied the spines of 17 rats to elucidate the exact pathways. We examined serial sections of the lumbar spine using immunohistochemistry for calcitonin gene-related peptide, a sensory nerve marker. We showed that these nerve fibres from the intervertebral disc ran through the sinuvertebral nerve into the rami communicantes, not into the corresponding segmental spinal nerve. In the rat, sensory information from the lumbar intervertebral discs is conducted through rami communicantes. If this innervation pattern applies to man, simple decompression of the corresponding nerve root will not relieve discogenic pain. Anterior interbody fusion, with the denervation of rami communicantes, may be effective for such low back pain.

Sensory nerve fibres from lumbar intervertebral discs pass through rami communicantes

It has been thought that lumbar intervertebral discs were innervated segmentally. We have previously shown that the L5-L6 intervertebral disc in the rat is innervated bilaterally from the L1 and L2 dorsal root ganglia through the paravertebral sympathetic trunks, but the pathways between the disc and the paravertebral sympathetic trunks were unknown. We have now studied the spines of 17 rats to elucidate the exact pathways. We examined serial sections of the lumbar spine using immunohistochemistry for calcitonin gene-related peptide, a sensory nerve marker. We showed that these nerve fibres from the intervertebral disc ran through the sinuvertebral nerve into the rami communicantes, not into the corresponding segmental spinal nerve. In the rat, sensory information from the lumbar intervertebral discs is conducted through rami communicantes. If this innervation pattern applies to man, simple decompression of the corresponding nerve root will not relieve discogenic pain. Anterior interbody fusion, with the denervation of rami communicantes, may be effective for such low back pain.

Intervertebral disc decompression following endplate damage: Middle-aged discs are affected most

Objective. To analyze the effect of asymmetrical loading on intradiscal pressure.Design. Human cadaveric lumbar spines were instrumented with multiple pressure sensors and subjected to external mechanical loads.Background. Tears and radial fissures in the posterolateral annulus with no evidence of annular protrusion or nuclear extrusion are frequently observed in non-degenerated intervertebral discs. Cadaveric studies have shown that asymmetrical loads lead to posterolateral herniation. Regional overload may be responsible for a progressive structural weakness of the posterolateral annular fibres.Methods. Three needles each equipped with three independent pressure sensors were inserted in the midplane of the L3L4 intervertebral disc (n = 16) in the anterior, right posterolateral and left posterolateral regions. Axial rotation was applied in the upright, flexed and extended positions and the pressures recorded.Results. The largest intradiscal pressure increase was observed in the posterolateral inner annular regions, more so in flexion than extension, when combined with axial rotation. Significant centripetal pressure gradients were found only in the posterolateral needles during the upright and flexed positions.Conclusions. When applying compression and axial rotation, the posterolateral inner annular zones of the intervertebral disc show high stress peaks and centripetal pressure gradients. Asymmetrical loads (rotation) combined with postural changes in the sagittal plane increase these effects, and may be responsible for a chronic mechanical overload of these regions.

Inflammatory cells in full-thickness anulus injury in pigs. An experimental disc herniation animal model.

Inflammatory cells were studied by indirect immunocytochemistry in experimental full-thickness anulus fibrosus lesions in pigs. First, to determine the occurrence, by immunocytochemistry, of T lymphocytes and macrophages in experimentally produced, anterolateral full-thickness disc lesions in pigs, and second, to compare the presence of inflammatory cells in 1) the injury area, 2) the adjacent noninjured part of the disc, and 3) control discs. Previous studies on disc herniation material obtained from human disc surgeries have demonstrated inflammatory cells in a subgroup of herniations. Macrophages were most prevalent, being more numerous than lymphocytes. Macrophages have furthermore been suggested to be important in the resorption process of extruded disc tissue. No similar studies on an animal model of disc herniation, however, have so far been presented. A full thickness anular incision, 10 mm long, was made with a scalpel in the L3-L4 or L4-L5 intervertebral discs of 12 adult pigs. The incision was made in the anterolateral part of the disc. Nucleus material was observed outside the injury site when tissue samples were taken, suggesting a disc herniation. Tissue then was analyzed from the area of injury, from the area adjacent to the injury, and from separate control discs from three additional pigs of the same age. Thin frozen sections were studied by indirect immunocytochemistry (alkaline phosphatase anti-alkaline phosphatase method) using monoclonal anti-human antibodies applicable to porcine tissues, T lymphocytes (CD3), and macrophages (CD68). Cells were graded as: -, absent; (+), only a few scattered cells; and +, abundant cells. Disc tissue samples were taken 1 month (three discs), 2 months (four discs), and 3 months (five discs) after the operation. Macrophages were present more commonly than T cells, and were abundant in seven of 12 discs (58%), with T cells abundant in four of 12 discs (33%). Only a few macrophages were present in the injured tissue from one additional disc, and scattered T cells were seen in four additional discs. Abundant macrophages were also observed in one of two discs in the adjacent noninjured area, whereas only a few T lymphocytes at the most were present in such noninjured disc tissue. In four (33%) and three (25%) injured discs, respectively, no macrophages or T lymphocytes could be found. No inflammatory cells were observed in three of 12 discs (25%). The three control discs showed no inflammatory cells. Inflammatory cells, predominantly macrophages, were present in a subsample of experimental discs with full-thickness anulus defects, as has previously been observed for human disc herniations. In this animal model, macrophages may have spread to adjacent noninjured parts of the disc. The induced herniation in this animal model is, however, anterolateral and may not fully correspond to clinical disc herniations, most of which are posterolateral. However, the results from this model support a role for inflammation in disc herniation.

Foraminal Herniation of a Lumbar Disc Mimicking Neurinoma on CT and MR Imaging

A case of a large L3-L4 intervertebral disc herniation causing a widening of the intervertebral foramen is reported. There was a soft-tissue mas within the spinal canal and intervertebral foramen. The soft-tissue mass within the spinal canal and intervertebral foramen showed marked enhancement on magnetic resonance scans after injection of a paramagnetic contrast agent (Gd-DTPA). The combination of lesion configuration and paramagnetic contrast enhancement mimicked a spinal neurinoma. There exists a degree of overlap between the imaging of herniated discs and spinal neurinomas. When this overlap involves several aspects, such as anatomic configuration, mass enhancement, and secondary foraminal dilatation, the differential diagnosis between a herniated disc and a neurinoma may be problematic.

T9-T10 Intervertebral Disc Herniation in Three Dogs

SummaryThree middle-aged (6-8 years), intact male Dachshunds were admitted to the University of Tennessee Veterinary Teaching Hospital (UTVTH) with acute onset of back pain and pelvic limb paralysis.Physical examination of dog #1 revealed hyperaesthesia of the thoracolumbar spine. Superficial pain sensation was absent in the pelvic limbs, while deep pain sensation was intact. The cutaneous trunci (panniculus) reflex was absent caudal to the thoraco-lumbar region. Reflexes to the pelvic limbs were exaggerated.A myelogram showed dorsal deviation of the ventral contrast column and attenuation of the ventral and dorsal contrast columns at the T9-T10 disc space. A hemilaminectomy was performed from T9 to T10, and mineralized disc material was retrieved from the vertebral canal at T9-T10. The T9- T10 to L3-L4 disc spaces were fenestrated. Two weeks after surgery, superficial and deep pain sensation of the rearlimbs were present, but paralysis persisted. The animal was euthanatised at the owners’ request. A postmortem examination was not performed.Dog #2 displayed absent superficial pain sensation, and intact deep pain sensation of the pelvic limbs. Hyperaesthesia of the thoracolumbar region and hyperreflexia of the rear limbs were noted. Examination of the cutaneous trunci reflex was not performed. A myelogram revealed ventral extradural compression of the spinal cord at T9- T10. A T9-T10 hemilaminectomy revealed a large amount of extruded disc material, which was removed. The Tll- T12 to L4-L5 intervertebral discs were fenestrated. Forty-eight hours postoperatively, the patient regained voluntary motor function, and recovery was uneventful.Neurologic examination of dog #3 revealed absence of deep pain sensation in the pelvic limbs; duration of which was not known. Spinal radiographs and myelography revealed ventral extradural spinal cord compression at T9-T10 (Fig.). A right-sided hemilaminectomy at T9-T10 revealed a large amount of calcified disc material, ventral to the spinal cord. The T11-T12 through Ll- L2 intervertebral discs were fenestrated. Sixty days postoperatively, paralysis persisted and the dog was euthanatised. No postmortem examination was performed.Herniation of the T9-T10 intervertebral disc was diagnosed in three Dachshunds with acute paraplegia. The clinical diagnosis and surgical management of T9-T10 disc herniation are similar to that in the more common sites of disc herniation.

Intradiscal Pressure Measurements Above an Instrumented Fusion

An in vitro study to determine the intradiscal pressure changes during flexion in levels above a simulated fusion was performed. To determine if intradiscal pressure increases more during flexion in discs above an instrumented spinal segment compared to an uninstrumented segment. The progressive degeneration of intervertebral discs adjacent to a fused or fixed segment is a phenomenon that is noted but poorly understood. Intuitively, the degeneration appears to be a function of altered biomechanics of the motion segments in the spine. Two intervertebral disc levels were evaluated, L3-L4 and L4-L5 from each of six fresh frozen cadaver spines. Pressure measurements were taken with the spine uninstrumented, with bilateral pedicle screw-rod instrumentation from L5 to S1, and with bilateral pedicle screw-rod instrumentation from L4 to S1. Pressure measurements were accomplished with Millar Mikro-Tip pressure transducers. The transducers were placed within the nucleus pulposus of L3-L4 and L4-L5 intervertebral discs. Pressure data were recorded by computer data acquisition. The pressure data were compared by intervertebral level and by the effects of added instrumentation. In general, the addition of instrumentation significantly affected the intradiscal pressure in the levels above a simulated fusion. The intradiscal pressure increased as the amount of levels involved in the simulated fusion increased. The intradiscal pressure increased as flexion motion increased. A greater increase was seen at the L4-L5 level than the L3-L4 level. When L5-S1 fixation was added, the intradiscal pressure increased. When L4-S1 fixation was added, the intradiscal pressure further increased. This study demonstrated increasing intradiscal pressures during flexion.

Increasing neuroforaminal volume by anterior interbody distraction in degenerative lumbar spine.

This study quantified changes in the size of the stenotic neuroforamen in degenerative lumbar spines. The volume and area of the neuroforamen were measured before and after the application of anterior distraction using the BAK interbody fusion system. To quantitatively assess the neuroforaminal area and volume when the BAK interbody fusion system is applied to lumbar spines with neuroforaminal stenosis. The spatial relationship between the nerve root and the osseous and nonosseous elements of the neuroforamen is clinically important. Few studies have focused on changes in neuroforaminal size in the lumbar spine after anterior interbody distraction. No previous study has assessed the neuroforaminal volume. The BAK instrumentation system was applied anteriorly at L4-L5 and L5-S1 intervertebral discs in nine degenerative cadaver lumbar spines. The neuroforaminal volumes of L4-L5 and L5-S1 were measured from silicon molds taken of the neuroforamen. In addition, computed tomography and circular blunt probes were used to determine the neuroforaminal areas. The disc height was recorded from lateral radiographs. After the BAK instrumentation, the volume of the neuroforamen increased significantly--by 22.9% for L4-L5 and 21.5% for L5-S1. The posterior disc height increased by 37.1% at L4-L5 and 45.1% at L5-S1. The neuroforaminal areas significantly increased--by 29.0% at L4-L5 and 33.8% at L5-S1. There was good correlation between the volume and the posterior disc height (R2 = 0.50) and the volume and the area of the narrowest portion of neuroforamen (R2 = 0.56). The results indicated that anterior systems such as the BAK system, which increase disc heights, can significantly increase neuroforaminal volume and area, providing adequate space for the nerve root and improving neuroforaminal stenosis.

Study of the lumbar curvature with various factors of pelvic inclination. Change of radiographic lumbar curvature according to hip joint flexion.

The objective of this study was to investigate the influence of the hip flexion upon parameters that are indicators of spinal mobility. These parameters include intervertebral disc angle and lumbar curvature by measurement of the radiography in twenty eight healthy men. The state of knowledge of how these parameters relate to lumbar mobility have resolved. The results of the parameters showed negligible changes in relation to the mobility of lumbar spine according to angle of hip flexion except at L4-L5 intervertebral disc angle and lumbar curvature (p < 0.05). This results of study confirms that hip joint movement therapy can be applied to these norms in patient management in supine position of for the stable spinal injuries in the upper lumbar region during early phase.

Lumbar intervertebral disc transfer. A canine study.

Degenerative lumbar disc disease has been implicated as a cause of low back pain. Current treatment options for low back pain involve nonphysiologic fusion of the involved segments and have variable success rates. This is an experimental study of lumbar intervertebral disc transplantation using a canine surgical model. This study evaluated the feasibility of lumbar disc transplantation and its effects on disc metabolism and morphology. Eight mature mongrel dogs underwent disc transfer surgeries, in which the L2-L3 and L4-L5 intervertebral discs, with a small segment of adjacent superior and inferior vertebral body, were removed and transposed. The transplanted disc were stabilized by plates or by a flexible cable wire construct using Songer cables (DANEK, Inc., Memphis, TN). Unrestricted activity was allowed postoperatively. At 4 months, the spines were harvested, and the transplanted discs were evaluated biochemically and histologically. Intervening nontransplanted discs served as viable controls and thrice-frozen discs served as nonviable controls. Cell viability was assessed by measuring proteoglycan synthesis and DNA content. Proteoglycan synthesis (35S uptake normalized to DNA content) was maintained in transplanted anulus fibrosus tissue, but was decreased in nucleus pulposus samples (P < 0.05). DNA content was not altered significantly in the transplanted discs. Histologic analysis of the transplanted discs showed revascularization and remodeling of the bone adjacent to the disc and preservation of the lamellar architecture of the anulus fibrosus. The transplanted nucleus pulposus samples had chondrocyte-like cells present, but the staining characteristics of the nucleus material was variable. The contour of the transplanted disc endplates was irregular in all specimens. The structure and function of autograft intervertebral discs were maintained after disc transfer surgery; the transplant discs, however, were not completely normal in either their morphology or their metabolic functioning.

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During a two-year period from January 1986 to December 1987, 54 patients underwent lumbar discectomy for herniated nucleus pulposus. Five patients (9.8%) were diagnosed as having an extraforaminal disc herniation.‹Materials› There were 3 male patients and 2 female patients. The age was 20-53 years old, the average being 36 years old. The site of nucleus pulposus were 4 cases at the L5-S1 intervertebral disc and one case at the L4-L5 intervertebral disc.‹Diagnosis› Clinically, the involved nerve root level could be easily identified but the point of compression was relatively difficult to decide. All patients were evaluated with myelography, computerized tomography, discography enhanced computerized tomography (Disco-CT) and nerve root infiltration. In all cases, myelography did not show any abnormalities. Disco-CT was very useful for accurate diagnosis of the extraforaminal disc herniation.‹Treatment› All patients had osteoplastic hemilateral laminectomy. This method was different from conventional laminectomy. To briefly reviewing this technique, the lamina is cut diagonally at the interarticular part and the spinous process is cut longitudinally with an osteotome from back to front. The lamina is removed in one piece and superior facet is cut in the medial one fourth and upper one fourth. The result of this procedure is that the extraf oraminal disc herniation can be easily identified and removed. After that, lamina is replaced and fixed with 5 silk threads.The advantages of this method are; 1) the operating area is wide and extraforaminal disc herniation can be removed safely and completely; 2) the intervertebral joints need not be sacrificed and spinal instrumentation is not necessary; 3) the posterior elements are kept intact and there will be no dead space. Follow-up study, the average being 13 months, showed good results. Osteoplastic hemilateral laminectomy is an effective method of management.

Lateral lumbar spine roentgenograms: Potential role in complications of lumbar disc surgery

Penetration into the abdominal cavity with injury to visceral, vascular, or neural structures is a potentially lifethreatening complication of lumbar disc exploration. In this report, we used reconstructed computed tomographic measurements of the L3-L4, L4-L5, and L5-S1 intervertebral discs to show that lateral spine roentgenograms contain an unavoidable magnification error that makes accurate measurement of minimal depth to penetration impossible. This magnification error may mislead the unwary surgeon into an overestimation of actual disc size. Moreover, the “safe distances” that have been published for the avoidance of penetration at the L3-L4, L4-L5, and L5-S1 intervertebral levels would have been excessive for 22.2%, 19.4%, and 8.3%, respectively, of the 26 patients in our study.