Extreme lateral disc herniation: diagnosis by computed tomographic scanning

Clinical experience on intertransverse extraforaminal approach for far lateral disc herniations: 132 cases

Background

Far lateral disc herniations attract many spine surgeons for their type of onset, degree of pain, risk of neurological deficit, and increasing incidence. Today, a direct approach to the region by miminally invasive techniques is preferred.

Aims

We aimed to present the results of the cases that were operated via intertransverse extraforaminal approach through a midline incision.

Patients and Methods

One hundred thirty-two patients who were operated for far lateral disc herniation by extraforaminal approach between January 2010 and December 2017 were retrospectively evaluated. The demographical data, level of disc herniations, examination findings, preoperative and postoperative VAS scores, and postoperative long-term MacNab satisfaction rates were recorded.

Results

Sixty-nine of the patients were male. The mean age was 58.1 years. Acute onset pain was a dominant complaint in 75% of the cases. The mean preoperative VAS score of 8.24 decreased to 2.08 at one month postoperatively. Based on a mean follow-up of 34.4 months, the long-term satisfaction rates according to Macnab criteria were 74% excellent-good, 20% moderate, and 6% poor.

Conclusion

Intertransverse extraforaminal approach is an effective and safe technique for far lateral disc herniations. However, considering the anatomical restrictions and the unfamiliarity of the surgeons with the region, it is important that the surgeons perform the surgery with the technique they know best to increase the success of the surgery.

Navigation-assisted extraforaminal lumbar disc microdiscectomy: Technical note

Background:

Extraforaminal lumbar disc herniation (ELDH) amounts of 7%–12% of all lumbar disc herniations. Although they have already been widely described, an optimal treatment is still under discussion in the literature.

Objective:

We describe a novel application of navigation using 2D/3D imaging system to plan an adequate surgical trajectory and performing a neuronavigated microdiscectomy in ELDH that has not been previously described.

Methods:

This is a retrospective study in a single institution. Between February 2017 and July 2020, a total of 12 patients (7 males and 5 females), with a mean age of 56 years (range 49–71 years), have been treated because of ELDH through a far lateral microdiscectomy using 2D/3D imaging system-assisted neuronavigation (O-arm).

Results:

No intraoperative and/or postoperative complications were recorded. Patients presented a mean preoperative Visual Analog Scale (VAS) score of 7.83 ± 0.83 (range 7–9). At the day of discharge, leg pain VAS score effectively improved, decreasing to a mean value of 1.83 ± 0.83 (range 1–3). Further, low back and radicular pain improvement was recorded at 1-, 6-, and 12-month follow-up, respectively.

Conclusion:

We described a novel use of 2D/3D imaging system navigation in the microsurgical treatment of ELDH that has not previously reported. This technique is safe and effective and provides more intraoperative details compared to fluoroscopy, which can be crucial for the success of the procedure and to reduce complications and particularly indicated in complex cases with altered anatomy.

Extraforaminal Disk Herniation Treatment with Surgical Exploration by Unilateral Intertransversarii Microsurgical Approach

BACKGROUND

In this study we evaluated the role of a unilateral intertransversarii microsurgical approach for the treatment of extraforaminal lumbar disk herniations (ELDHs), with short-, medium-, and long-term follow-up.

METHODS

We retrospectively evaluated 96 patients who had undergone surgery for ELDH between 2001 and 2012 at our Institution. All the patients had been examined before the intervention, immediately after, and at 6 weeks, 6 months, and 18 months after the intervention. All the patients underwent surgical exploration with a unilateral intertransversarii microsurgical approach. After a midline incision was made, the paraspinal muscles were retracted laterally up to the transverse process, in order to visualize the intertransversarii ligament. Removal of this ligament allows microsurgical exposure of the extraforaminal pathology. If necessary, interlaminar microsurgical exploration is performed in the same session.

RESULTS

At 6-week postoperative follow-up we noted a significant decrease of pain both in patients who suffered from leg pain and in patients who reported back pain. Also, sensory and motor deficits had improved considerably. At 6-month postoperative follow-up we observed a further improvement in the clinical conditions of almost all patients. At the 18-month postoperative follow-up we observed a very low incidence of relapse of neurological symptoms.

CONCLUSION

Our technique can be reasonably proposed because of its low morbidity, fast recovery, and short hospital stay.

Three-Years Outcome of Microdiscectomy via Paramedian Approach for Lumbar Foraminal or Extraforaminal Disc Herniations in Elderly Patients over 65 Years Old

OBJECTIVE

Lumbar foraminal or extraforaminal disc herniations (FEFDH) have unusual clinical features and higher incidence in elderly patients compared to usual intraspinal canal disc herniations. We evaluated the efficacy of microdiscectomy via paramedian approach for lumbar FEFDH in elderly patients over the age of 65.

METHODS

Retrospective study was performed in 68 patients over the age of 65 (23 male and 45 female patients; 71.46±3.87 years) who underwent microdiscectomy via paramedian approach for unilateral lumbar FEFDH causing sciatica. The radiological factors including degree of slippage, presence of instability, disc height, and degree of disc degeneration; pain and functional status by the means of visual analogue scale score, Oswestry Disability Index score, and Macnab classification were analyzed preoperatively and during the postoperative follow-up period of 3 years to evaluate the efficacy of the surgical treatment.

RESULTS

Pain and functional status improved according to short- and long-term follow-up evaluations after surgery. Radiological changes following surgery, which can be understood as structural deteriorations and deformations, did not represent patient condition. Nine patients underwent additional surgery due to sustained or recurring leg pain of aggravation of back pain, and fusion surgery was required for 3 patients. Degree of preoperative slippage was the only statistically significant factor related to additional surgery (p<0.05).

CONCLUSION

Microdiscectomy via paramedian approach for FEFDH may be a good surgical alternative in elderly patients. Radiological changes after surgery did not show a concordance with patients' actual functional status. The excessive preoperative slippage tended to lead to unfavorable result after surgery and was associated with additional surgery.

Herniated nucleus pulposus in isthmic spondylolisthesis: higher incidence of foraminal and extraforaminal types

BACKGROUND

The purpose of this study was to evaluate the pattern of disc herniation and to investigate the associated symptoms in cases of isthmic spondylolisthesis. It is well known that the pathogenesis of degenerative spondylolisthesis associates with disc degeneration, followed by facet laxity and ligamentum flavum hypertrophy, which result in severe spinal canal stenosis. But isthmic spondylolisthesis is known to have a different pathogenesis. In isthmic spondylolisthesis, pseudodisc bulging is easily identified, and canal stenosis is comparatively rare. Therefore, we propose that isthmic spondylolisthesis has a different pattern of disc herniation from degenerative spondylolisthesis. We studied the type, incidence of disc herniation and clinical symptoms related to isthmic spondylolisthesis.

METHOD

This study included 132 patients with isthmic spondylolisthesis who had undergone an operation in the last 4 years. Among them, 120 patients were retrospectively reviewed. The mean age was 49.6 years, and the sex ratio was 1 to 1.93 (male to female). The disc herniation type was identified according to the classification of Bonneville.

FINDINGS

There were 78 patients (65%) with L4 to L5 spondylolisthesis and 42 patients (35%) with L5 to S1 spondylolisthesis. Eighty-two patients (68.3%) had only pseudodisc bulging without disc herniation, and 38 patients (31.7%) had pseudodisc bulging with disc herniation. Among the 38 patients with disc herniation, there were: medial type: 1 patient (2.6%), medial + posterolateral type: 1 patient (2.6%), posterolateral + foraminal type: 2 patients (5.3%), foraminal type: 7 patients (18.4%), foraminal + extraforaminal type: 25 patients (65.8%) and extraforaminal type: 2 patients (5.8%). Overall extreme lateral disc herniation (foraminal, extraforaminal) was seen in 36 patients, which was 30% of the total isthmic spondylolisthesis cases. In 26 out of 36 patients (72.2%), the dermatome was matched to the exact location of the extreme lateral disc herniation. In all cases, the extreme lateral disc herniation migrated upward slightly, about one slice (2 mm) according to thin-cut CT.

CONCLUSIONS

As expected, pseudodisc bulging without disc herniation was the most common type in isthmic spondylolisthesis. However, in cases of disc herniation, extreme lateral disc herniation occasionally occurs; therefore, every isthmic spondylolisthesis patient should be examined carefully for extreme lateral disc herniation with thin-cut axial CT or MRI, especially when the patients complain of lateralizing symptom.

Minimally invasive approach to extraforaminal disc herniations at the lumbosacral junction using an operating microscope: case series and review of the literature

Surgical access to extraforaminal lumbar disc herniations is complicated due to the unique anatomical constraints of the region. Minimizing complications during microdiscectomies at the level of L5–S1 in particular remains a challenge. The authors report on a small series of patients and provide a video presentation of a minimally invasive approach to L5–S1 extraforaminal lumbar disc herniations utilizing a tubular retractor with microscopic visualization.

Minimally invasive far lateral microendoscopic discectomy for extraforaminal disc herniation at the lumbosacral junction: cadaveric dissection and technical case report

BACKGROUND CONTEXT

Extraforaminal lumbar disc herniations (ELDHs) at the lumbosacral junction are an uncommon cause of L5 radiculopathy. The surgical anatomy of the extraforaminal space at L5-S1 is uniquely challenging for the various open surgical approaches that have been described for ELDHs in general. Reports specifically describing minimally invasive surgical approaches to lumbosacral ELDHs are lacking.

PURPOSE

To report the novel use of a far lateral microendoscopic (FLMED) approach to lumbosacral ELDH. To better define the unique anatomical features of extraforaminal approaches to the lumbosacral junction as they apply to minimal access techniques.

STUDY DESIGN/SETTING

A cadaveric investigation and clinical case were performed at a single institution. A thorough review of the literature was conducted.

PATIENT SAMPLE

A single patient with an extraforaminal disc herniation at the lumbosacral junction underwent evaluation and surgery.

OUTCOME MEASURES

The patient's self-reported pain levels were documented. Physiologic outcome was judged on pre- and postoperative motor and sensory examinations. Functional capacity was assessed by work status and ability to perform activities of daily living.

METHODS

FLMED was performed in two fresh human cadavers at the lumbosacral junction. Qualitative assessments of the surgical anatomy were made, and intraoperative fluoroscopy and endoscopic photographs were obtained to document the findings. A patient with refractory pain and sensorimotor deficits from compression of the L5 nerve root by an ELDH underwent FLMED. The literature was carefully reviewed for the epidemiology of ELDHs at the lumbosacral junction and the surgical techniques used to treat them.

RESULTS

The posterolateral surgical corridor to the lumbosacral disc was consistently constrained by the sacral ala and to a lesser extent the lateral facet and L5 transverse process. Resection of the superior ala exposed the exiting nerve root and provided ample access to the disc. In the clinical case, the patient enjoyed immediate pain relief, was discharged in 3 hours, and returned to full work and social activities. Follow-up neurological examination revealed no sensory or motor deficit.

CONCLUSIONS

FLMED offers a safe and efficacious approach to ELDHs at the lumbosacral junction by combining satisfactory visualization for adequate resection of the sacral ala with the benefits of reduced tissue injury and faster recovery times that accompany minimally invasive techniques.

Use of the ventrodorsal myelographic view to predict lateralization of extruded disk material in small-breed dogs with thoracolumbar intervertebral disk extrusion: 104 cases (2004–2005)

OBJECTIVE

To determine whether the ventrodorsal myelographic view can be used to accurately predict the circumferential location of extruded disk material in dogs with thoracolumbar intervertebral disk extrusion (IVDE) and to describe paradoxical contrast obstruction (PCO).

DESIGN

Retrospective case series.

ANIMALS

104 dogs with Hansen type I IVDE. Procedures-Ventrodorsal myelographic views were reviewed, and contrast patterns were categorized according to 8 predetermined patterns. Agreement among observers was compared, and the predicted location of extruded disk material was compared with surgical findings.

RESULTS

Agreement regarding myelographic pattern and location of extruded disk material was moderate (kappa = 0.74 and 0.80, respectively) among the 4 observers. Ninety-three (89%) dogs had myelographic evidence of lateralized extrusion, and in 83 of the 93 (89%), predicted location of extruded disk material matched the surgically confirmed location. In 33 of the 40 (83%) dogs with bilateral contrast column gaps of unequal length, disk material was found to be located on the side with the shorter, rather than the longer, contrast gap, a phenomenon described as PCO.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that the ventrodorsal myelographic view could be used to predict the circumferential location of extruded disk material in dogs with thoracolumbar IVDE more often than previously reported. The PCO phenomenon may be useful in determining the side of lateralization when contrast material does not outline the extruded disk material.

A minimally invasive transmuscular approach to far-lateral L5-S1 level disc herniations: a prospective study

BACKGROUND

Among all lumbar disc herniations, L5-S1 far-lateral disc herniations are rare entities. Besides, surgical approach may be difficult because of the very narrow passage at this level. For these 2 reasons, most spine surgeons are not experienced in herniations at this level. According to new microanatomic studies, previous lateral approaches at this level often do not allow access to the neuroforamen without partial or total destruction of the L5-S1 facet joint. To preserve the facet joint, an approach was developed.

PURPOSE

To assess the efficacy of a surgical technique that is a minimally invasive intermuscular approach (MIIMA) for decompression of L5-S1 far-lateral level disc herniation (FLLDH).

STUDY DESIGN

We present a prospective clinical study analysis of 14 patients with L5-S1 far-lateral disc herniations in a period between 2000 and 2004, treated with microsurgical technique.

METHODS

An imaging study revealed consistency with the patient's clinical presentation. In our department, a total of 580 patients underwent discectomy between 2000 and 2004 for lumbar disc herniation.

RESULT

Twenty-eight patients had foraminal or extraforaminal herniations (4.8%). Fourteen patients had FLLDH at the L4-L5 level (2.4%), whereas the other 14 were cases of FLLDH at the L5-S1 level (2.4%). One patient had FLLDH at both L5-S1 and L4-L5 levels (7.1%). The mean age of patients was 53.6 years, and the male:female ratio was approximately 5:9. All patients failed to recover after at least 6 weeks of conservative therapy. The mean duration of symptoms until the time of surgery was 7.2 months. Using this MIIMA technique, the authors removed the herniated discs compressing the (L5) nerve roots. Clinical outcome was measured using the visual analog scale. Every patient was discharged within 24 hours. Satisfactory (excellent or good) results were demonstrated in 13 patients (92.9%), because, except for 1 (7.1) permanent dysesthesia case, 4 cases (21.3%) were temporary dysesthesia. Postoperatively all patients reported excellent relief of their sciatic pains, and there were no technique-associated complications. No recurrence was observed during the follow-up period ranging from 10 to 60 months (mean, 29 mo). This is one of the major complications of any approach to a far-lateral disc.

CONCLUSIONS

The authors describe a MIIMA for excising herniated discs that is applicable to all types of far-lateral lumbar herniations. Postoperative dysesthesia is the most important complication and may persist as it did in our cases. Consequently, manipulation of the ganglion should be avoided at all costs, if possible. The MIIMA procedure provides a simple alternative for treating lumbar foraminal or lateral exit zone herniated discs in selected cases. This approach is effective, allowing the preservation of the L5-S1 facet joint, saving the facet joint, preventing postoperative instability, and offering a direct view of the L5-S1 neuroforamen.

Transforaminal Percutaneous Endoscopic Discectomy in the Treatment of Foraminal and Extraforaminal Lumbar Disc Herniations

The objective of this study is to evaluate the efficacy of the endoscopic technique, as applied to patients with foraminal and extraforaminal disc herniations, and to report the outcome and complications. A retrospective analysis was performed of 35 consecutive cases of foraminal and extraforaminal lumbar disc herniation managed by posterolateral endoscopic discectomy. Pain was measured by means of the Visual Analog Score. Patient satisfaction was evaluated by the Macnab outcome criteria. The median follow-up period was 18 months (range 10 to 35 months). The mean Visual Analog Score improved from 8.6 before the surgery to 3.2 after the surgery. Overall, excellent or good outcomes were obtained in 30 (85.7%) of the 35 patients at the last follow-up examination, with both these outcomes showing statistically significant improvement (P<0.01). There were no complications related to the surgery, nor was any spinal instability detected. Three patients (8.6%) experienced persistent radiculopathy and subsequently underwent open microdiscectomy at the same level. We concluded that transforaminal percutaneous endoscopic discectomy is safe and efficacious in the treatment of foraminal or extraforaminal disc herniations. However, proper patient selection is paramount to ensure a satisfactory outcome after decompression of foraminal and extraforaminal disc herniations.

Lateral transmuscular or combined interlaminar/paraisthmic approach to lateral lumbar disc herniation? A comparative clinical series of 48 patients

BACKGROUND

The optimum operative technique for lateral lumbar disc herniations (LLDH) remains unclear, and both interlaminar and extraspinal approaches are used.

OBJECTIVE

To compare outcome after LLDH removal either by a lateral transmuscular approach (LTM) or by a combined interlaminar and paraisthmic approach (CIP).

METHODS

28 patients underwent surgery using CIP and 20 using LTM. All patients were operated on by the same neurosurgeon. The clinical presentation of the two groups was comparable. Overall outcome was assessed after a mean follow up period of between 19 and 37 months using the Ebeling classification. In addition, the effect of surgery on radicular pain, low back pain, and sensory and motor deficits was defined.

RESULTS

Excellent to good results were achieved in 95% of the LTM group and 57% of the CIP group. The outcome was satisfactory to poor in 5% of the LTM and 43% of the CIP group (p<0.004). The percentage of sensorimotor deficit and of radicular pain improvement was higher in the LTM group. New low back pain was found exclusively in the CIP group (21%). The complication rate was 5% in the LTM group and 11% in the CIP group.

CONCLUSIONS

The LTM approach achieves a better overall outcome and improvement in radiculopathy. The complication rate is lower with the transmuscular route and the risk of new low back pain is minimised. These results are likely to be attributable at least in part to the lesser invasiveness of the LTM approach.

Paraspinal approach to the far lateral disc herniations: retrospective study on 42 cases

Forty-two patients underwent surgery for far-lateral disc herniations. Average patient age was 45.1 years, 28 patients were male and 14 female. The level concerned most was L4-5 disc (55%). A paramedian muscle-splitting intertransverse approach is described for this type of disc herniation. This method allows direct visualization of the disc and root involved and does not provide bone resection and important surgical manipulation. Ninety-one percent of the patients reported excellent or good results according to Macnab outcome criteria with an average follow-up of 32.5 months (range 1-5 years). Twelve patients (28.6%) developed postoperative transient radicular pain that disappeared in 15-21 days after analgesic therapy. There were no recurrences or spinal instability. The paramedian muscle-splitting intertransverse approach is a rational technique. Its advantages are that the spine is not opened and spinal stability is maintained. It requires minimal soft-tissue and bone resection and the herniated disc is directly visualized. Moreover, it contains minimal manipulation of the neuro-vascular structures and avoids significant muscle retraction. However, it requires an adequate learning curve and good familiarity with microsurgical techniques.

Micro-endoscopic-discectomy (MED) for far lateral disc herniation in the lumbar spine. Technical note

This study describes a new experience of the authors in the treatment of extraforaminal disc herniation via the micro-endoscopic far lateral approach to establish a less traumatic approach to extraforaminal disc herniation with less stay in hospital and less cost. Seventeen patients who underwent surgery for extraforaminal disc herniation were analysed and long-term follow up was done revisiting all of them in hospital. The results of surgical decompression via the micro-endoscopic far lateral approach were good in all patients with minimal discomfort. There was complete resolution of leg pain presented. Dysesthesia subsided after 2-3 weeks. Extraforaminal disc herniation can be diagnosed with the aid of CT scan and MRI. The minimally invasive surgical treatment via the micro-endoscopic far lateral approach, in our initial experience, has a high rate of succes.

Extraforaminal lumbar disc herniations: microsurgical anatomy and surgical approach

OBJECT

Familiarity with the microsurgical anatomy of the far-lateral compartment is essential for operating in patients with far-lateral discs. In this report the authors address the microsurgical anatomy studied in 24 extraforaminal lumbar disc spaces in three cadavers.

METHODS

Cadaveric dissections confirmed the authors' operative experience in which they found an arterial arcade to be associated with the nerve trunk. The main trunk of the lumbar artery was located lateral to the exiting nerve root in the region of intervertebral foramen. The trunk of the lumbar spinal nerve descending from the level above was 7 mm (+/- 3 mm [standard deviation]) lateral to the lumbar artery.

CONCLUSIONS

Clarification of the microsurgical anatomy of the far-lateral compartment confirmed the authors' clinical impression that the optimum approach to far-lateral discs is via the inferomedial quadrant of the extraforaminal compartment. In this quadrant, exposure of the main nerve root can be facilitated by dividing the posterior primary ramus and a newly described arterial arcade that envelops the nerve trunk. Once this arcade is divided, the nerve can be retracted with relative ease and safety, and the disc can be removed more easily.

Significance of a persistent positive straight leg raising test after lumbar disc surgery

OBJECT

Results of the straight leg raising (SLR) test provide the clinician with valuable information regarding possible causes of a patient's pain. In a previous study the results have also demonstrated a correlation between the outcome of the test and the severity of pain, as well as the prognostic value of the test; patients for whom the SLR test is persistently positive postoperatively appear to have a poorer short-term outcome. In a prospective study of 200 consecutive patients who underwent surgery for disc herniation, the authors evaluated the frequency of repeated surgery and outcome of surgery in patients with a persistent postoperative positive SLR test.

METHODS

The preoperative radiological evaluation included myelography, computerized tomography scanning, and/or magnetic resonance imaging. Preoperatively as well as 4, 12, and 24 months postoperatively, each patient was interviewed and examined using a standard protocol in which common symptoms and signs were described. The result of the SLR test was also classified into one of four categories: positive 0 to 30 degrees ; positive 30 to 60 degrees, positive greater than 60 degrees, or negative, and the surgical results were evaluated using a four-grade scale. Preoperatively, the SLR test was positive in 86% of patients. At 4 months postoperatively, 22% still had a positive SLR test. For the patients whose SLR test was positive 4 months postoperatively, the long-term outcome at all three follow-up examinations was inferior; this difference was statistically significant.

CONCLUSIONS

During the 2-year period, the reoperation rate was 18% (eight of 44) in patients with a positive postoperative SLR test compared with 4.5% (seven of 156) in patients whose postoperative SLR test was negative. A postoperative positive SLR test thus correlates to an unfavorable surgical outcome.

The surgical treatment of far lateral L3-L4 and L4-L5 disc herniations. A modified technique and outcomes analysis of 25 patients

STUDY DESIGN

A retrospective review of 25 patients who underwent a modified surgical procedure for the treatment of far lateral disc herniation.

OBJECTIVES

To describe a modification of previous surgical techniques for the treatment of far lateral disc herniation and to review the outcomes in resolution of pain and improvement of functional status.

SUMMARY OF BACKGROUND DATA

Lumbar disc herniations that occur far lateral to the intervertebral facet result in spinal nerve compression at L3-L4 and L4-L5. Previous surgical techniques have resulted in an increased risk of instability or continued postoperative back pain.

METHODS

Twenty-five patients with far lateral disc herniation underwent surgery using an extreme lateral approach. There was no medial facetectomy or disruption of the pars interarticularis. The intertransverse ligament was released from the superior portion of the inferior transverse process, and the nerve was located before removal of the disc. Preoperative and postoperative visual analog pain scale and Oswestry functional status evaluation were reviewed along with complications to evaluate the efficacy of the surgery.

RESULTS

No serious complications were noted, although transient neuropathic pain was common and was theorized to be caused by manipulation of the dorsal root ganglion during surgery. This pain was usually resolved within 4 to 6 weeks. The mean preoperative and postoperative visual analog scale scores were 7.7 and 4.2, respectively. The mean preoperative and postoperative Oswestry scores were 50.7% and 34.7%, respectively. Both of these improvements were statistically significant (P < 0.01).

CONCLUSIONS

This far lateral approach allowed the nerve and far lateral disc herniations to be easily identified. Also, there was less blood loss and no medial facetectomy or disruption of the pars interarticularis. This is a safe, effective technique with no disruption of spinal stability.

Long-term follow up of patients surgically treated by the far-lateral approach for foraminal and extraforaminal lumbar disc herniations

OBJECT

This study was undertaken to evaluate the long-term benefit in 202 patients who were surgically treated via a microsurgical far-lateral approach for foraminal or extraforaminal lumbar disc herniations.

METHODS

All patients underwent surgery at the authors' institute since 1987 and represented 6.5% of all lumbar spinal disc surgeries. There were 67 women and 135 men who ranged in age from 19 to 78 years (mean age 58 years). All patients had unilateral leg pain due to lumbar disc herniations into or lateral to the lateral interpedicular compartment. One patient underwent surgery at the L1-2 level, nine at L2-3, 48 at L3-4, 86 at L4-5, and 58 at the L5-S1 level. The mean follow-up period was 50 months (range 12-120 months). Outcome was defined as excellent (no pain), good (some back pain), fair (moderate radiculopathy), and poor (unchanged or worse) based on Macnab classification. Overall, excellent and good results were achieved in 62 (31%) and 85 (42%) patients, respectively, and fair and poor results in 40 (20%) and 15 (7%) patients, respectively. Of 11 recurrent disc herniations, four presented in an extreme-lateral position, five in a paramedian location, and two on the contralateral side. There were three minor complications related to surgery, seven general complications, and no case of spinal instability.

CONCLUSIONS

The far-lateral approach is a safe, effective procedure that avoids the risk of secondary spinal instability.

A paramedian tangential approach to lumbosacral extraforaminal disc herniations

OBJECTIVE

Extraforaminal disc herniations today are operated on via the so-called lateral approach. Clinical experience has shown that in contrast to levels L2/3-L4/5, this approach may become extremely difficult at the L5-S1 level. According to new microanatomic studies, the previous lateral approaches at this level often do not allow access to the neuroforamen without partial or total destruction of the L5-S1 facet joint. Postoperatively, this may lead to joint irritation with consecutive low back and pseudoradicular pain. To preserve the facet joint, a new approach was developed based on an anatomic study.

METHODS

The approach was first considered with the help of bone specimens including ilium, vertebra 5, and sacrum. Thereafter, lumbar maceration specimens were prepared leaving ligaments, intervertebral discs, and joints intact. From these specimens, bony and ligamentous landmarks were deduced. Finally, the approach was tested on seven cadavers. Subsequently, the approach was performed on 13 patients and the intraoperative findings, the clinical feasibility, and the postoperative results were analyzed.

APPROACH

After a transverse skin incision above the dorsal curvature of the ilium, the paravertebral muscles are dissected from the ilium medially toward the spinous process. Lateral from the apophyseal joint, a canal is drilled through the spongiosa of the sacrum. Primarily, a thin layer of inner cortex is spared to protect the content of the neuroforamen. Subsequently, it can easily be removed with the dissector to enter the extraforaminal space. In the depth of the drilled canal, the nerve root is found, because it is fixed at the sacrum near the disc space by the anterior lumbosacral ligaments. Riding on the nerve root, the intertransverse ligament and muscle can be removed with the punch. It is then possible to see the neuroforamen and extraforaminal space in front of the joint. Free fragments and contained discs can then easily be found and removed.

CONCLUSION

Using this new approach, the L5-S1 joint remains intact. Space for instrumental manipulations is created in areas not essential for joint function. For this procedure, newly defined anatomic landmarks, such as the ileolumbar ligament, upper edge of the sacrum, lateral rim of the apophyseal joint, and para-articular notch, guide the operative route. In accordance with the preliminary anatomic studies, this approach was successfully used in 13 patients, and we think that it is a promising alternative that helps to preserve joint function and dorsal root ganglion integrity.

Plain CT of the degenerative lumbar spine

Degenerative processes of the lumbar spine consist of several disorders of various etiologies with different radiological manifestations. Computed tomography (CT) is well suited for evaluation of these processes since contours of soft tissues, subtle bone structure changes and small calcifications are easily demonstrated with this technique. Spiral CT scanning provides fast data acquisitions, and volumes of high quality for multiplanar reformatting. This review article describes the CT scanning techniques and diagnostic findings of the most common degenerative processes of the lumbar spine.

Microsurgical anatomy of the lateral approach to extraforaminal lumbar disc herniations

OBJECTIVE

During the "lateral" approach to extraforaminal lumbar disc herniations, the surgeon may be confronted with considerable variations in anatomy, making this approach extremely difficult in some patients. An anatomic study, therefore, was undertaken to examine the bony boundaries of the operative target, the medial intertransverse space.

METHODS

In 31 lumbar spine specimens taken from cadavers of people who had been between 30 and 93 years old at death, the relevant distances and proportions of the operative window were measured at the levels L1-L2 to L5-S1.

RESULTS

Measurements revealed that the operative window in a systematic fashion becomes progressively smaller as the approach moves from L1-L2 toward L5-S1: 1) from L1 to L5, the medial boundary, the isthmus laminae, gradually extends farther laterally and eventually covers the waist of the respective vertebral body; 2) the lower boundary, the facet joint, gradually overlaps the disc space in an upward and lateral direction; 3) the upper boundary, the transverse process, gradually moves downward. Anatomic variations and abnormalities are found particularly often at the L5-S1 level.

CONCLUSION

The anatomic findings led to important conclusions regarding the microsurgical approach to extraforaminal lumbar disc herniations; at levels L1-L2 to L3-L4, the midline approach with lateral retraction of the paraspinal muscles allows for efficient exposure of the lateral neural foramen and avoidance of trauma to the facet joint. Often at level L4-L5, and nearly always at level L5-S1, a tangential route through a paramedian transmuscular approach offers many advantages.

Extreme lateral lumbar disc herniation: clinical presentation in 178 patients

A retrospective analysis of clinical characteristics of 178 consecutive patients with extreme lateral lumbar disk herniation, amongst 3047 patients operated on for herniated lumbar disc, is presented. The level specific incidence of extreme lateral disc herniation (ELLDH) ranged from a low of 4.5% at L4-5 to peak of 17.4% at L3-4 although the largest number of ELLDH occurred at L4-5 and L5-S1 for a total number of 139 cases (78.1%). 43.6% of all L3 radiculopathies were caused by an L3-4 ELLDH, whereas only 4.4% of all L5 radiculopathies were caused by an L5-S1 ELLDH. Leg pain, either of the sciatic or the femoral type, was the first and dominant clinical symptom of radiculopathy, but pain radiation occurred not always in the appropriate dermatomal segment. ELLDH at upper levels (L2-3 and L3-4) caused usually none or only minor low back signs (76.2%), whereas ELLDH at lower levels more often caused moderate or major lumbar symptoms and signs (59.6%). Positive femoral nerve traction test with upper ELLDH showed a high frequency (84.4%) and reliability and is therefore an important clinical parameter in this situation. Motor deficits occurred more often (78.8%) than sensory deficits (46.6%), were usually of the monoradicular type and were therefore a more reliable clinical sign than sensory disturbances.

Surgical observations in extremely lateral lumbar disc herniation

About 10% of lumbar disc herniations are localized in an extreme lateral position referred to as "extracanalicular". The clinical syndrome is a typical one with compression signs of the lateral, extra-foraminal nerve root and minimal lumbar pain. A reliable diagnosis can be made only since high resolution spinal computed tomography has become available. Surgical treatment will be rendered difficult by the "hidden" localisation of the disc fragments. A total number of 15 patients has been operated on in our department during the last year. In 10 patients, we used the lateral microsurgical approach proposed by REULEN, in five cases a combined procedure with lateral sequestrotomy and medial nucleotomy. In the first group, re-sequestration occurred in three cases and further surgery including medial nucleotomy was performed then. A good result with remission could be achieved in 13 cases, whereas in two cases with additional spondylolisthesis, lumbar back pain continued, but the radicular symptoms were reduced.

Are there typical localisations of lumbar disc herniations? A prospective study

A prospective intra-operative analysis of the location of lumbar disc herniation was performed in 131 patients with verified 54% contained (incomplete) and 46% non-contained (complete) lumbar disc herniations. Bulging discs or protrusions are not included in this study. Complete disc herniations occurred more frequently in the upper lumbar spine. The localization of the lumbar disc herniations within its segment showed no correlation to the affected level. 64% of the disc herniations were located medio-laterally, 20% laterally, 12% within or lateral of the intervertebral compartment and 5% in the midline. Nearly one third of all herniations were found at the level of the disc space. Medio-lateral disc herniations were displaced more often in a caudal direction, lateral herniations were found displaced upwards and downwards with similar frequency while extraforminal herniations migrated significantly more often in a cranial direction. The pathomechanism and anatomical pathways of disc fragment migration are discussed on the basis of a new concept of the anterior extradural space.

Unilateral facetectomy approach for lateral lumbar disc herniation

Forty-one patients with herniated lumbar discs in a lateral location underwent unilateral complete facetectomy for removal of their disc herniation. The diagnosis was made by computerized tomography in all patients. The follow-up period varied between 4 and 60 months, with an average of 22.4 months. All patients underwent dynamic lumbar spine x-ray films with flexion and extension exposures at various times during their follow-up period. The results were excellent in 35 patients, good in three, and poor in three. One patient suffered spinal instability postoperatively and required lumbar fusion because of back pain. Unilateral facetectomy gives an excellent view of the affected nerve root and the herniated disc, and the risk of spinal instability is very low.

Frequency and specific surgical management of far lateral lumbar disc herniations

A) 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. B) 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.

Diagnosis and microsurgical approach to far-lateral disc herniation in the lumbar spine

Lumbar-disc herniations that occur beneath or far lateral to the intervertebral facet joint are increasingly recognized as a cause of spinal nerve root compression syndromes at the upper lumbar levels. Failure to diagnose and precisely localize these herniations can lead to unsuccessful surgical exploration or exploration of the incorrect interspace. If these herniations are diagnosed, they often cannot be adequately exposed through the typical midline hemilaminectomy approach. Many authors have advocated a partial or complete unilateral facetectomy to expose these herniations, which can lead to vertebral instability or contribute to continued postoperative back pain. The authors present a series of 25 patients who were diagnosed as having far lateral lumbar disc herniations and underwent paramedian microsurgical lumbar-disc excision. Twelve of these were at the L4-5 level, six at the L5-S1 level, and seven at the L3-4 level. In these cases, myelography is uniformly normal and high-quality magnetic resonance images may not be helpful. High-resolution computerized tomography (CT) appears to be the best study, but even this may be negative unless enhanced by performing CT-discography. Discography with enhanced CT is ideally suited to precisely diagnose and localize these far-lateral herniations. The paramedian muscle splitting microsurgical approach was found to be the most direct and favorable anatomical route to herniations lateral to the neural foramen. With this approach, there is no facet destruction and postoperative pain is minimal. Patients were typically discharged on the 3rd or 4th postoperative day. The clinical and radiographic characteristics of far-lateral lumbar-disc herniations are reviewed and the paramedian microsurgical approach is discussed.

Pedicle origin and intervertebral compartment in the lumbar and upper sacral spine. A biometric study

The osseous boundaries of the intervertebral compartment are described. Measurements of the pedicles demonstrate that their configuration determines the shape of the intervertebral compartment. The pedicles originate in the upper lumbar spine (L 1 and L 2) in a vertical direction from the posterior aspects of the vertebral bodies. In the caudal lumbar spine (L 4 and L 5) the origin of the pedicles is more oblique and thereby moves much more laterally and ventrally. As a consequence the horizontal extension of the pedicles is increasing in the lower lumbar spine. In the upper lumbar region the intervertebral compartment corresponds more to a foramen, in the lower lumbar spine more to a canal. The resulting clinical relevance for the length of the intervertebral compartment and the nerve root course is discussed.

Extraforaminal lumbar disc herniations: CT demonstration of Sharpey's fibers avulsion

Forty-seven extraforaminal lumbar disc herniations (EFLDH) accounting for 7% of all lumbar disc herniations encountered during the same period of time were reviewed. L3-L4 or L4-L5 disc was involved in 89% of the cases giving rise to a L3 or L4 nerve root compression. An abnormal motion of lateral bending with rotation of the trunk was found retrospectively in 60% of the patients. In 53% of all EFLDH a bony avulsion of the vertebral end-plate facing the herniation was demonstrated at the site of attachment of Sharpey's fibers. This study suggests that this previously undescribed bony change witnesses a special injury of the spine responsible for most EFLDH.

Extreme lateral lumbar disc herniation

Extreme lateral lumbar disc herniation (ELLDH) occurring into and/or outside the intervertebral foramen was encountered in 95 cases amongst 1600 operations for herniated lumbar disc (6%): 43% occurred at L5-S1, 38% at L4-5, 18% at L3-4, and 1% at L2-3. The incidence amongst all herniations at one particular level was 6% at L5-S1, 4% at L4-5, and 18% at L3-4. The clinical presentation varied according to the level of extreme lateral disc herniation, but was not different from the presentation of a classical paramedian herniation occurring one level above. Forty-three patients were investigated with computed tomography (CT) only, 2 with myelography only, and 50 with both. CT always clearly demonstrated the pathology, but some cases are presented to illustrate the differential diagnosis. Myelography was normal in 13 cases; in 27 cases it showed a typical shortening and enlargement of the nerve root sheath which enters the affected intervertebral foramen. At operation, a total facetectomy was performed in 52 patients, a partial facetectomy in 34, and a lateral approach to the intervertebral foramen in 9. The lateral approaches, either paramuscular with retraction of the paraspinal muscles from the midline, or transmuscular by splitting of the paraspinal muscles, are described and illustrated in detail.