Variations in the lumbosacral ligament and associated changes in the lumbosacral region resulting in compression of the fifth dorsal root ganglion and spinal nerve

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.

Alternative Splicing of Nrcam Gene in Dorsal Root Ganglion Contributes to Neuropathic Pain

NrCAM, a neuronal cell adhesion molecule in the L1 family of the immunoglobulin superfamily, is subjected to extensively alternative splicing and involved in neural development and some disorders. The aim of this study was to explore the role of Nrcam mRNA alternative splicing in neuropathic pain. A next generation RNA sequencing analysis of dorsal root ganglions (DRGs) showed the differential expression of two splicing variants of Nrcam, Nrcam⁺¹⁰ and Nrcam^-10, in the injured DRG after the fourth lumbar spinal nerve ligation (SNL) in mice. SNL increased the exon 10 insertion, resulting in an increase in the amount of Nrcam⁺¹⁰ and a corresponding decrease in the level of Nrcam^-10 in the injured DRG. An antisense oligonucleotide (ASO) that specifically targeted exon 10 of Nrcam gene (Nrcam ASO) repressed RNA expression of Nrcam⁺¹⁰ and increased RNA expression of Nrcam^-10 in in vitro DRG cell culture. Either DRG microinjection or intrathecal injection of Nrcam ASO attenuated SNL-induced the development of mechanical allodynia, thermal hyperalgesia, or cold allodynia. Nrcam ASO also relieved SNL- or chronic compression of DRG (CCD)-induced the maintenance of pain hypersensitivities in male and female mice. PERSPECTIVE: We conclude that the relative levels of alternatively spliced Nrcam variants are critical for neuropathic pain genesis. Targeting Nrcam alternative splicing via the antisense oligonucleotides may be a new potential avenue in neuropathic pain management.

Quantification of fat in the posterior sacroiliac joint region: fat volume is sex and age dependant

Fat is appreciated as a structural component of synovial joints. It may serve a shock-absorbing function for the incongruent surfaces, vessels and ligaments, but has not been investigated in the posterior sacroiliac joint (PSIJ). Sixty-six cadaveric hemipelves were serially-sectioned and photographed. The amount of visible fat in the PSIJ was quantified using a modified version of Cavalieri’s method. Total volume, fat volume and fat percentage of the PSIJ were calculated in predefined sub-regions. Fat is consistently present in the PSIJ (1.9 ± 1.3 cm³). Fat volume correlates with the PSIJ total volume (p < 0.0001; r = 0.73) and age (p = 0.024; r = 0.24), and is smaller in males (1.4 ± 0.8 cm³) than females (2.4 ± 1.5 cm³). Fat volumes in the middle and inferior sub-regions of the PSIJ show side- (p < 0.0001) and sex-differences (p = 0.013 females, middle sub-region). Age and PSIJ total volume correlate between sexes in various sub-regions (p = 0.05 females superior sub-region; males inferior sub-region). Fat percentage differs between sexes and sub-regions (p = 0.018 females, superior sub-region) but is independent of age and sides. The presence of fat within the PSIJ is a normal finding and shows sex-dependant and age-related differences. It is unclear whether fat is linked to age-related degeneration or has a shock-absorbing role in stress- and load-dissipation in the PSIJ.

Bilateral Neuropathy of Primary Sensory Neurons by the Chronic Compression of Multiple Unilateral DRGs

To mimic multilevel nerve root compression and intervertebral foramina stenosis in human, we established a new animal model of the chronic compression of unilateral multiple lumbar DRGs (mCCD) in the rat. A higher occurrence of signs of spontaneous pain behaviors, such as wet-dog shaking and spontaneous hind paw shrinking behaviors, was firstly observed from day 1 onward. In the meantime, the unilateral mCCD rat exhibited significant bilateral hind paw mechanical and cold allodynia and hyperalgesia, as well as a thermal preference to 30°C plate between 30 and 35°C. The expression of activating transcription factor 3 (ATF3) was significantly increased in the ipsilateral and contralateral all-sized DRG neurons after the mCCD. And the expression of CGRP was significantly increased in the ipsilateral and contralateral large- and medium-sized DRG neurons. ATF3 and CGRP expressions correlated to evoked pain hypersensitivities such as mechanical and cold allodynia on postoperative day 1. The results suggested that bilateral neuropathy of primary sensory neurons might contribute to bilateral hypersensitivity in the mCCD rat.

Chronic Compression of the Dorsal Root Ganglion Enhances Mechanically Evoked Pain Behavior and the Activity of Cutaneous Nociceptors in Mice

Radicular pain in humans is usually caused by intraforaminal stenosis and other diseases affecting the spinal nerve, root, or dorsal root ganglion (DRG). Previous studies discovered that a chronic compression of the DRG (CCD) induced mechanical allodynia in rats and mice, with enhanced excitability of DRG neurons. We investigated whether CCD altered the pain-like behavior and also the responses of cutaneous nociceptors with unmyelinated axons (C-fibers) to a normally aversive punctate mechanical stimulus delivered to the hairy skin of the hind limb of the mouse. The incidence of a foot shaking evoked by indentation of the dorsum of foot with an aversive von Frey filament (tip diameter 200 μm, bending force 20 mN) was significantly higher in the foot ipsilateral to the CCD surgery as compared to the contralateral side on post-operative days 2 to 8. Mechanically-evoked action potentials were electrophysiologically recorded from the L3 DRG, in vivo, from cell bodies visually identified as expressing a transgenically labeled fluorescent marker (neurons expressing either the receptor MrgprA3 or MrgprD). After CCD, 26.7% of MrgprA3⁺ and 32.1% MrgprD⁺ neurons exhibited spontaneous activity (SA), while none of the unoperated control neurons had SA. MrgprA3⁺ and MrgprD⁺ neurons in the compressed DRG exhibited, in comparison with neurons from unoperated control mice, an increased response to the punctate mechanical stimuli for each force applied (6, 20, 40, and 80 mN). We conclude that CCD produced both a behavioral hyperalgesia and an enhanced response of cutaneous C-nociceptors to aversive punctate mechanical stimuli.

Inhibition of Hyperpolarization-Activated Cation Current in Medium-Sized DRG Neurons Contributed to the Antiallodynic Effect of Methylcobalamin in the Rat of a Chronic Compression of the DRG

Recently several lines of evidence demonstrated that methylcobalamin (MeCbl) might have potential analgesic effect in experimental and clinical studies. However, it was reported that MeCbl had no effect on treating lumbar spinal stenosis induced pain. Thus, the effects of short-term and long-term administration of MeCbl were examined in the chronic compression of dorsal root ganglion (CCD) model. We found that mechanical allodynia was significantly inhibited by a continuous application of high dose and a single treatment of a super high dose of MeCbl. Little is known about mechanisms underlying the analgesia of MeCbl. We examined the effect of MeCbl on the spontaneous activity (SA), the excitability, and hyperpolarization-activated nonselective cation ion current in compressed medium-sized dorsal root ganglion (DRG) neurons using extracellular single fiber recording in vivo and whole-cell patch clamp in vitro. We found that MeCbl significantly inhibited the SA of A-type sensory neurons in a dose-dependent manner and inhibited the excitability of medium-sized DRG neurons. In addition, MeCbl also decreased I_h current density in injured medium-sized DRG neurons. Our results proved that MeCbl might exert an analgesic effect through the inhibition I_h current and then might inhibit the hyperexcitability of primary sensory neurons under neuropathic pain state.

The sacroiliac joint: an overview of its anatomy, function and potential clinical implications

This article focuses on the (functional) anatomy and biomechanics of the pelvic girdle and specifically the sacroiliac joints (SIJs). The SIJs are essential for effective load transfer between the spine and legs. The sacrum, pelvis and spine, and the connections to the arms, legs and head, are functionally interrelated through muscular, fascial and ligamentous interconnections. A historical overview is presented on pelvic and especially SIJ research, followed by a general functional anatomical overview of the pelvis. In specific sections, the development and maturation of the SIJ is discussed, and a description of the bony anatomy and sexual morphism of the pelvis and SIJ is debated. The literature on the SIJ ligaments and innervation is discussed, followed by a section on the pathology of the SIJ. Pelvic movement studies are investigated and biomechanical models for SIJ stability analyzed, including examples of insufficient versus excessive sacroiliac force closure.

Electrophysiological diagnosis using sensory nerve action potential for the intraforaminal and extraforaminal L5 nerve root entrapment

BACKGROUND

The diagnosis of lumbar intraforaminal and extraforaminal stenosis (lumbar foraminal stenosis) is sometimes difficult. However, sensory nerve action potential (SNAP) decreases in amplitude when the lesion is at or distal to the dorsal root ganglion. Therefore, the amplitude of SNAP with lumbar foraminal stenosis should be decreased. In this cohort study, the usefulness of SNAP for the preoperative diagnosis of L5/S foraminal stenosis was assessed.

METHODS

In 63 patients undergoing unilateral L5 radiculopathy, bilateral SNAPs were recorded for the superficial peroneal nerve (L5 origin). The patients were divided into two groups according to the results of imaging examinations. Group A (37 patients) included patients whose lesion was located only at the intraspinal canal. In group B (26 patients), the lesion was located only at the intra- or extraforaminal area. All patients received surgery and the symptoms were diminished. The ratios of the amplitudes of SNAPs on the affected side to that on the unaffected side were compared between groups A and B.

RESULTS

SNAPs could not be elicited bilaterally in four patients. The amplitude ratio for group B (median 0.42, max 1.17, min 0) was significantly lower than that in group A (median 0.85, max 1.43, min 0) (p < 0.001 by Mann-Whitney U test). Using a cut-off value of 0.5 for the amplitude ratio, the sensitivity for the diagnosis of lumbar foraminal stenosis was 91.3 % with a specificity of 85.7 %.

CONCLUSIONS

Measurement of SNAP could be useful to diagnose a unilateral L5/S foraminal stenosis.

Posterior decompression surgery for extraforaminal entrapment of the fifth lumbar spinal nerve at the lumbosacral junction

Object

In this paper, the authors' goal was to elucidate the clinical features and results of decompression surgery for extraforaminal stenosis at the lumbosacral junction.

Methods

Twenty-eight patients with severe leg pain caused by extraforaminal stenosis at the lumbosacral junction (18 men and 10 women; mean age 68.2 ± 8.9 years) were treated by posterior decompression without fusion using a microendoscope in 19 patients and a surgical microscope or loupe in 9 patients. The decompression procedures consisted of partial resection of the sacral ala, the L-5 transverse process, and the L5–S1 facet joint along the L-5 spinal nerve. The following items were investigated: 1) preoperative neurological findings; 2) preoperative radiological findings, including plain radiographs, CT scans, selective radiculography of L-5; 3) surgical outcome as evaluated using the Japanese Orthopaedic Association scale for low-back pain (JOA score); and 4) need for revision surgery.

Results

All patients presented with neurological deficits compatible with a diagnosis of L-5 radiculopathy such as weakness of the extensor hallucis longus muscle and sensory disturbance in the L-5 area together with neurogenic claudication. On plain radiographs, 21 patients (75%) and 17 patients (60.7%) exhibited lumbar scoliosis (≥ 5°) and wedging of the L5–S1 intervertebral space (≥ 3°), respectively. The CT scans demonstrated marked osteophyte formation at the posterolateral margin of the L5–S1 vertebral bodies, and a selective L-5 nerve root block was effective in all patients. All patients reported pain relief immediately after surgery. The mean JOA scores were 11.3 ± 3.8 before surgery and 24.3 ± 3.4 at the time of the final follow-up examination; the recovery rate was 68.6 ± 16.5%. The mean estimated blood loss was 66.6 ± 98.6 ml, and the mean surgical time was 135.3 ± 46.5 minutes. No significant difference in the recovery rate of the JOA scores or in the surgical time and blood loss was observed between the 2 surgical approaches. Four patients underwent revision posterior interbody fusion for the recurrence of radicular pain as a result of intraforaminal stenosis in 3 patients and insufficient decompression of the extraforaminal area in the remaining patient at an average of 19.5 months after surgery.

Conclusions

Extraforaminal stenosis at the lumbosacral junction is a rare but distinct pathological condition causing L-5 radiculopathy. Decompression surgery without fusion using a microendoscope or a surgical microscope/ loupe is a feasible and less invasive surgical option for elderly patients with extraforaminal stenosis at the lumbosacral junction.

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.

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.

The assessment and management of chronic hamstring/posterior thigh pain

Hamstring injuries have a high incidence and recurrence rate. Much is understood with regards to the mechanism of hamstring injury, with eccentric loading at fast rates being important. Little is known about the aetiology of hamstring injury, with age and previous injury being the only causative factors with robust scientific support. Clinically, it can be difficult to differentiate between a lesion occurring in hamstring tissue and pain that is experienced in the hamstrings that is referred from elsewhere. The use of specific examination procedures such as the slump test and the straight leg raise, supplemented with other sensitive and specific tests can help in the differential diagnosis. This chapter will explore the aetiology of chronic hamstring injury/posterior thigh pain, will discuss the differential diagnosis of chronic hamstring/posterior thigh pain, and present a model for the management of these injuries.

Robust increase of cutaneous sensitivity, cytokine production and sympathetic sprouting in rats with localized inflammatory irritation of the spinal ganglia

We investigated the role and mechanisms of inflammatory responses within the dorsal root ganglion (DRG) in the development of chemogenic pathological pain. DRG inflammation was induced by a single deposit of the immune activator zymosan in incomplete Freund's adjuvant in the epidural space near the L5 DRG via a small hole drilled through the transverse process. After a single zymosan injection, rats developed bilateral mechanical hyperalgesia and allodynia which began by day 1 after surgery, peaked at days 3-7, and lasted up to 28 days. The number of macrophages in ipsilateral and contralateral DRGs increased significantly, lasting over 14 days. Robust glial activation was observed in inflamed ganglia. Cytokine profile analysis using a multiplexing protein array system showed that, in normal DRG, all but interleukin (IL)-5, IL-10 and granulocyte-macrophage colony stimulating factor (GM-CSF) were detectable with concentrations of up to 180 pg/mg protein. Local inflammatory irritation selectively increased IL-1beta, IL-6, IL-18, monocyte chemoattractant protein-1 (MCP-1), and growth-related oncogene (GRO/KC) up to 17-fold, and decreased IL-2 and IL-12 (p70) up to threefold. Inflaming the DRG also remarkably increased the incidence of spontaneous activity of A- and C-fibers recorded in the dorsal root. Many of the spontaneously active A-fibers exhibited a short-bursting discharge pattern. Changes in cytokines and spontaneous activity correlated with the time course of pain behaviors, especially light stroke-evoked tactile allodynia. Finally, local inflammation induced extensive sprouting of sympathetic fibers, extending from vascular processes within the inflamed DRG. These results demonstrate the feasibility of inducing chronic localized inflammatory responses in the DRG in the absence of traumatic nerve damage, and highlight the possible contribution of several inflammatory cytokines/chemokines to the generation of spontaneous activity and development and persistence of chemogenic pathologic pain.

Microendoscopic partial resection of the sacral ala to relieve extraforaminal entrapment of the L-5 spinal nerve at the lumbosacral tunnel

✓ The authors report the cases of three patients with L-5 radiculopathy caused by extraforaminal entrapment of the L-5 spinal nerve at the lumbosacral tunnel; this structure comprises the lumbosacral ligament, the sacral ala, and the L-5 and S-1 vertebral bodies. All three patients suffered severe leg pain and neurological deficits compatible with L-5 radiculopathy. Decompressive surgery involved the microendoscopic partial resection of the sacral ala along the L-5 spinal nerve. All patients experienced immediate pain relief postoperatively. Microendoscopic partial resection of the sacral ala is an effective and minimally invasive surgical option for patients with extraforaminal entrapment of the L-5 spinal nerve.

Lumbar spine region pathology and hamstring and calf injuries in athletes: is there a connection?

This paper discusses the theory that subtle lumbosacral canal impingement of the L5 nerve root may be a relatively common occurrence in older footballers and may in fact be a common underlying basis for the age related predisposition towards hamstring and calf strains.

Segmental degeneration in the cervical spine and associated changes in dorsal root ganglia

Degenerative change in cervical segments C5-C7 was documented to determine whether osteo-ligamentous adaptations were age-related. In addition, companion morphological studies were carried out to determine whether parallel changes occurred in related soft tissues, including DRG. Independent of the provoking stimulus, aberrant soft tissue change may be expected with segmental degeneration. Two associations were identified: between the incidence of segmental degeneration and severity of DRG distortion, and between segmental degeneration and DRG inflammatory mast cell density. Peripheral type C cells seemed more susceptible to compression in circumstances of DRG distortion. In light of neuropeptide expression in these cell types, predominant type C cell compression may be clinically relevant in the noxious cascade contributing to the sensation of pain.

Extraforaminal entrapment of the fifth lumbar spinal nerve by osteophytes of the lumbosacral spine: anatomic study and a report of four cases

STUDY DESIGN

An anatomic study of the associations between the fifth lumbar spinal nerve (L5 spinal nerve) and a lumbosacral tunnel, consisting of the fifth lumbar vertebral body (L5 vertebral body), the lumbosacral ligament, and sacral ala, and clinical case reports of four patients with lumbar radiculopathy secondary to entrapment of the L5 spinal nerve in the lumbosacral tunnel.

OBJECTIVES

To delineate the anatomic, clinical, and radiologic features and surgical outcome of patients with entrapment of the L5 spinal nerve in the lumbosacral tunnel.

SUMMARY OF BACKGROUND DATA

Although several cadaveric studies on a lumbosacral tunnel as a possible cause of L5 radiculopathy have been reported, few studies had focused on osteophytes of the L5-S1 vertebral bodies as the major component of this compressive lesion, and clinical reports on patients with this disease have been rare.

METHODS

Lumbosacral spines from 29 geriatric cadavers were examined with special attention to the associations between osteophytes of the L5-S1 vertebral bodies and the L5 spinal nerve. Four patients with a diagnosis of the entrapment of the L5 spinal nerve by osteophytes at the lumbosacral tunnel were treated surgically, and their clinical manifestations and surgical results were reviewed retrospectively.

RESULTS

The anatomic study demonstrated osteophytes of the L5-S1 vertebral bodies in seven of the 29 cadavers. Entrapment of the L5 spinal nerve in the lumbosacral tunnel was observed in six of the seven cadavers with L5-S1 osteophytes but in only one of the 22 cadavers without such osteophytes (P < 0.05, chi2 test). All four patients had neurologic deficits in the L5 nerve root distribution. MRI and myelography showed no abnormal findings in the spinal canal, but CAT scans demonstrated prominent osteophytes on the lateral margins of L5-S1 vertebral bodies in all four. Selective L5 nerve block completely relieved all patients of pain but only temporarily. Three patients were treated via a posterior approach by resecting the sacral ala along the L5 spinal nerve, and the other patient was treated by laparoscopic anterior resection of the osteophytes. Pain relief was obtained in the four patients immediately after surgery, but one patient experienced recurrence of pain 1 year after the first surgery and was successfully treated by additional posterior decompression and fusion.

CONCLUSIONS

Extraforaminal entrapment of L5 spinal nerve in the lumbosacral tunnel can cause L5 radiculopathy, and osteophytes of L5-S1 vertebral bodies are a major cause of the entrapment.

Enhanced excitability of sensory neurons in rats with cutaneous hyperalgesia produced by chronic compression of the dorsal root ganglion

Pain and hyperalgesia can occur when the dorsal root ganglion (DRG) and its roots are deformed mechanically in association with injuries or diseases of the spine. To evaluate the electrophysiological changes that contribute to this sensory pathology, intracellular recordings were obtained in vitro from DRGs that had received a chronic mechanical compression [chronic compression of DRG (CCD)]. The compression was produced by inserting L-shaped rods ipsilaterally into the intervertebral foramina, one at L(4) and the other at L(5) in rats 1-14 days before the recording. Control rats received a sham operation. Postoperatively, the threshold force applied by punctate stimulation of the plantar surface of the hind paw decreased significantly on the foot ipsilateral to the CCD (mechanical hyperalgesia) but changed little on the contralateral foot or on either foot for control rats. DRG somata were viewed through a microscope during recording and classified as small, medium, and large according to their diameters. CCD cells in each size category were more excitable than those of comparable size from control rats as judged by the significantly lowered threshold currents and action potential voltage thresholds. Spontaneous activity was recorded in 11% of all the CCD cells tested. The spontaneous activity and/or changes in both the threshold currents and action potential thresholds were observed as early as one day after injury. The association of cutaneous hyperalgesia with changes in the electrophysiological properties of DRG cells suggests a possible role for intrinsic alterations in the membrane properties of compressed DRG cells in the production and persistence of chronic pain after certain spinal injuries or pathologies of the spine.

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.