Myofibroblasts are increased in the dorsal layer of the hypertrophic ligamentum flavum in lumbar spinal canal stenosis.

BACKGROUND CONTEXT: Hypertrophy of the ligamentum flavum (LF) is a major contributor to the development of lumbar spinal canal stenosis (LSS). Although previous studies have identified some factors related to hypertrophy of the LF, the etiology remains unclear. It is well known that myofibroblasts have a key role in the pathology of fibrosis in other tissues, including the skin, liver, kidney, and lung. We hypothesized that myofibroblasts were also important players in the pathology of fibrosis in the LF. PURPOSE: To elucidate the distribution and role of myofibroblasts in the hypertrophic LF. STUDY DESIGN: A histological, immunohistochemical, and gene expression analysis of the LF in the human lumbar spine. PATIENT SAMPLE: Hypertrophic LF tissue samples were collected from patients with LSS. OUTCOME MEASURES: Histology, immunohistochemistry, microarray, reverse transcription-quantitative polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay. METHODS: The degree of fibrosis in the dural and dorsal layers of the LF was evaluated by Masson's trichrome tissue staining. Collagen gene expression was evaluated by quantitative reverse transcription polymerase chain reaction. Immunostaining of αSMA was performed to evaluate localization of myofibroblasts in LF tissue. The association between gene expression of alpha-smooth muscle actin (αSMA) and that of several types of collagen was investigated. The signal activated on the dorsal side of LF was examined by gene set enrichment analysis using microarray data. Expression levels of αSMA and several types of collagen in LF fibroblasts were investigated under hypoxic conditions. RESULTS: In the histological study using Masson's trichrome staining, the fibrosis score was significantly higher in the dorsal layer than in the dural layer. Gene expression levels for several types of collagen (COL1A1, COL1A2, COL3A1, COL5A1, COL6A1, and COL11A1) and heat shock protein 47 (a collagen-specific chaperone) were significantly higher in the dorsal layer. Furthermore, immunohistochemistry revealed a significantly greater number of αSMA-stained cells in the dorsal layer. There was a strong correlation of αSMA mRNA expression with COL1A-1 in LF fibroblasts. Gene set enrichment analysis showed that the set of fibrosis-related gene signals, including those for epithelial-mesenchymal transition, hypoxia, and inflammation, were significantly upregulated in the dorsal layer compared with the dural layer. Under hypoxic stimulation, expression of αSMA and several types of collagen was increased in LF fibroblasts. CONCLUSIONS: This study is the first to reveal that myofibroblast expression levels are higher in the dorsal layer of the LF than in the dural layer. We confirmed that hypertrophy of the LF in LSS is associated with increased expression of myofibroblasts in the dorsal layer. Hypoxia could be a cause of expression of myofibroblasts leading to fibrosis and finally to hypertrophy of the LF. CLINICAL SIGNIFICANCE: The results of this study partially elucidate the molecular mechanisms of LF hypertrophy and suggest that myofibroblasts may be involved in age-related degeneration of the LF.

Mycobacterium abscessus ssp. abscessus infection progressing to empyema from vertebral osteomyelitis in an immunocompetent patient without pulmonary disease: a case report.

BACKGROUND: Pleural involvement by non-tuberculous mycobacteria (NTM) in patients without distinct pulmonary disease is extremely rare. Vertebral osteomyelitis (VO) with or without pulmonary disease is also a rare clinical presentation of NTM infection, and pleural spread of NTM from VO has not been reported. CASE PRESENTATION: A 63-year-old woman was admitted to our hospital with back pain persisting for 4 months and a 2-day history of fever and right chest pain. The patient was initially treated as right-sided empyema due to general bacteria. However, after removal of the chest tube, a previously overlooked paravertebral lesion was observed on CT. MRI confirmed VO at T7/8. Mycobacterium abscessus ssp. abscessus was detected in both the thoracic cavity and the paravertebral lesion. Both VO and the paravertebral abscess were improved by antimycobacterial treatment. CONCLUSION: VO of the thoracic spine due to non-tuberculous mycobacterial infection should be considered as a cause of pleuritis or empyema without pulmonary disease, especially in patients with back pain.

Pullout Strength of Pedicle Screws Following Redirection After Lateral or Medial Wall Breach.

STUDY DESIGN: A cadaveric biomechanical study designed to test the pullout strength of pedicle screws. OBJECTIVE: To evaluate the pullout strength of redirected pedicle screws with a larger diameter following lateral wall breach, redirected pedicle screws of the same diameter following medial wall breach, and redirected pedicle screws with a larger diameter following medial wall breach. SUMMARY OF BACKGROUND DATA: Screw malposition is one of the main pitfalls of inserting pedicle screws. Intraoperatively a malpositioned screw is redirected and inserted along the correct axis. METHODS: Forty-seven vertebrae (T9-L5) were harvested from eight fresh cadaveric spines. The 18 pedicle screws that breached the lateral wall were then removed and redirected using a pedicle screw of 1 mm larger in diameter. The 16 pedicle screws that had breached the medial wall were then removed and redirected using a pedicle screw of the same diameter. The other 13 pedicle screws that had breached the medial wall were then removed and redirected using a pedicle screw of 1 mm larger in diameter. The pullout strength was measured. RESULTS: Following lateral wall breach, mean pullout strength for the larger redirected screws was 46.9% greater than that of the correctly aligned screws. Following medial wall breach, mean pullout strength for the redirected screws of the same diameter was 20.6% less than that of the correctly aligned screws. Mean pullout strength for the larger pedicle screws following medial wall breach was 27.3% more than that of the correctly aligned screws. CONCLUSION: Redirected pedicle screws of larger diameter after a lateral or medial pedicle breach show recovery of pullout strength. However, the pullout strength of redirected pedicle screws of the same diameter after a medial pedicle breach is significantly less than that of correctly aligned screws. LEVEL OF EVIDENCE: 1.

Degenerative Changes of the Facet Joints in Adults With Lumbar Spondylolysis.

STUDY DESIGN: Radiologic analysis using computed tomography. OBJECTIVES: To analyze the degenerative changes of the facet joints in patients with spondylolysis in comparison with control subjects. SUMMARY OF BACKGROUND DATA: Defects of the pars interarticularis are thought to result in a reduction of biomechanical stress on adjacent facet joints. Therefore, degenerative changes of the facet joints in patients with spondylolysis are expected to be less than those in patients without spondylolysis. METHODS: Abdominal and pelvic multidetector computed tomography scans of 2000 subjects, performed for conditions unrelated to low back pain, were reviewed. A total of 107 patients (37 women and 70 men) with L5 spondylolysis were identified [spondylolysis (+) group]. Sex-matched and age-matched controls without spondylolysis were chosen randomly [spondylolysis (-) group]. Subjects in the spondylolysis group were subdivided into either bilateral spondylolysis or unilateral spondylolysis groups for comparison with the control group. Four radiologic findings (narrowing, sclerosis, osteophyte, and bone cyst) indicative of degenerative change of the facet joints adjacent to the L5 pars defects were evaluated and the degree of degenerative change was graded by summing the number of degenerative changes (score range, 0-4). The χ test and Mann-Whitney U test were used for statistical analysis. RESULTS: Significantly more degenerative changes in both L4/L5 and L5/S facet joints were found in the spondylolysis (+) group than in the spondylolysis (-) group (χ test, P <0.05). Degenerative changes of the facet joints at both L4/L5 and L5/S were more severe in the bilateral spondylolysis (+) group than in the spondylolysis (-) group. Degenerative changes of the facet joints at both L4/L5 and L5/S were more severe in the unilateral spondylolysis (+) group than in the spondylolysis (-) group. CONCLUSIONS: Degenerative changes of the facet joints in patients with lumbar spondylolysis were more severe than those without spondylolysis.

Pediatric isthmic spondylolisthesis showing radiologic evidence of slippage after physis injury.

The pathogenesis of slippage in pediatric spondylolisthesis is still unclear, although epiphyseal injury may account for many cases based on preclinical studies. However, no reports have described a pediatric case of isthmic spondylolisthesis showing radiologic evidence of epiphyseal injury. We report such evidence in a 13-year-old boy with low-back pain. Radiography revealed rounding of the S1 surface, a fracture line below the S1 endplate surface, and a bone marrow lesion in addition to slippage. Slippage and the rounding deformity were partially reversed (from 20 to 14% and from 42 to 27%, respectively) with conservative treatment and natural bone remodeling.

Proteomic Analysis of Human Tendon and Ligament: Solubilization and Analysis of Insoluble Extracellular Matrix in Connective Tissues.

Connective tissues such as tendon, ligament and cartilage are mostly composed of extracellular matrix (ECM). These tissues are insoluble, mainly due to the highly cross-linked ECM proteins such as collagens. Difficulties obtaining suitable samples for mass spectrometric analysis render the application of modern proteomic technologies difficult. Complete solubilization of them would not only elucidate protein composition of normal tissues but also reveal pathophysiology of pathological tissues. Here we report complete solubilization of human Achilles tendon and yellow ligament, which is achieved by chemical digestion combined with successive protease treatment including elastase. The digestion mixture was subjected to liquid chromatography-mass spectrometry. The low specificity of elastase was overcome by accurate mass analysis achieved using FT-ICR-MS. In addition to the detailed proteome of both tissues, we also quantitatively determine the major protein composition of samples, by measuring peak area of some characteristic peptides detected in tissue samples and in purified proteins. As a result, differences between human Achilles tendon and yellow ligament were elucidated at molecular level.

The Pullout Strength of Pedicle Screws Following Redirection After Lateral Wall Breach or End-plate Breach.

STUDY DESIGN: Using fresh cadavers, the biomechanical testing were used to examine the pullout strength of each pedicle screw. OBJECTIVE: The aim of this study was to evaluate pullout strength of (1) a redirected pedicle screw following lateral wall breach; (2) a redirected pedicle screw following end-plate breach; and (3) a pedicle without redirection after end-plate breach without redirection. SUMMARY OF BACKGROUND DATA: Screw malposition, such as lateral wall breach or end-plate breach, is one of the main pitfalls of inserting pedicle screws. METHODS: From 17 fresh spines, 54 vertebrae were harvested. In each vertebra on one pedicle, the screw was inserted correctly down the axis of the pedicle, while on the other pedicle, the screw was inserted to breach the lateral wall or the end-plate. The 18 pedicle screws that breached the lateral wall were then removed and redirected along the correct axis of the pedicle. The 18 pedicle screws that breached the end-plate were removed and redirected along the correct axis of the pedicle. The 18 other pedicle screws that had breached the end-plate were not removed. The pullout force of pedicle screws was measured. RESULTS: First, the mean pullout strength for the redirected screws following lateral wall breach was 24.0% less as compared with the correctly aligned screws. Second, the mean pullout strength for the redirected screws following end-plate breach was 23.3% less as compared with the correctly aligned screws. Third, the mean pullout strength for the pedicle screws end-plate breach was 7.6% less as compared with the correctly aligned screws. CONCLUSION: The pullout strength of redirected pedicle screws after either a lateral pedicle breach or end-plate breach is significantly less than the pullout strength of correctly aligned screw. A pedicle screw that is not redirected after end-plate breach is weaker than a pedicle screw correctly aligned; however, the difference is not significant. LEVEL OF EVIDENCE: N/A.

Prevalence of Symptomatic Lumbar Spondylolysis in Pediatric Patients.

Lumbar spondylolysis, a stress fracture of the pars interarticularis, is prevalent in adolescent athletes. Recent advances in diagnostic tools and techniques enable early diagnosis before these fractures progress to complete fractures through the pars. However, because patients often consult family physicians for primary care of low back pain and these physicians may not have access to diagnostic modalities such as magnetic resonance imaging (MRI) and computed tomography, stress fractures can be missed. This study surveyed the prevalence of symptomatic spondylolysis in pediatric patients who consulted an orthopedic clinic for primary care and investigated whether such acute stress fractures may be overlooked without MRI. The prospective study investigated 264 patients who were younger than 19 years and had low back pain. Of the 153 patients (58.0%) with low back pain persisting for longer than 2 weeks, 136 who agreed to undergo MRI were included in the study. This group included 11 elementary school students, 71 junior high school students, and 54 high school students. The overall prevalence of lumbar spondylolysis was 39.7% (54 of 136) and was 9.3% in elementary school students (5 of 11, 45.5%), 59.3% in junior high school students (32 of 71, 45.1%), and 31.5% in high school students (17 of 54, 31.5%). All 54 patients with spondylolysis had a history of athletic activity. Primary care physicians should recognize that approximately 40% of pediatric patients presenting with low back pain persisting for longer than 2 weeks may have spondylolysis and should consider MRI in those with a history of athletic activity. Because the spine is immature in this age group, almost half of affected elementary school and junior high school students may have lumbar spondylolysis. [Orthopedics. 2016; 39(3):e434-e437.].

Postoperative discal cyst: An unusual complication after microendoscopic discectomy in teenagers.

Various complications after microendoscopic discectomy (MED) are well known, but postoperative discal cyst is a unique and relatively unknown complication. Here, we report on two teenage patients who presented with postoperative discal cyst after MED for herniated nucleus pulposus (HNP), which resolved after conservative treatment. The patients were diagnosed with HNP at L4-5 and L5-S1 based on MRI and then treated by MED. Postoperative discal cyst was diagnosed on MRI after recurrence of symptoms. Both patients were managed conservatively. T2-weighted MRI demonstrated hyperintense collections adjacent to the operated intervertebral disc level, which were communicating with the corresponding disc annulus. Because the clinical symptoms were relatively mild, the patients were managed conservatively; both made a complete clinical recovery with radiological evidence of improvement. Postoperative discal cyst is a relatively unknown complication after MED for HNP. Surgeons should be aware of this postoperative complication when operating on young individuals with HNP.

Characteristics of lumbar spondylolysis in elementary school age children.

PURPOSE: Lumbar spondylolysis, a stress fracture of the pars interarticularis in the lumbar spine, is often precipitated by trauma, but there may be a congenital predisposition to this condition. There have been few studies on spondylolysis in young children, despite their suitability for studies on congenital defects. The aim of this study was to identify the clinical features of lumbar spondylolysis in elementary school age children in order to elucidate its pathogenesis. METHODS: Thirty lumbar spondylolysis patients (23 boys, 7 girls, including a pair of twins; mean age 9.5 years, age range 5-12 years) were studied. Patient data on history of athletic activity, symptoms at first consultation, and radiological findings such as spinal level, stage of the stress fracture, and skeletal age were collected. RESULTS: Among the 30 patients, 27 (21 boys, 6 girls) had L5 spondylolysis (90.0 %). Only 2 patients had no history of athletic activity at the first consultation. All patients, except for 2 whose diagnosis was incidental, complained of low back pain. In the 27 patients with L5 spondylolysis, 17 (63.0 %) had terminal-stage fracture and 25 (92.6 %) had spina bifida occulta (SBO) involving the S1 lamina. Sixteen of the 27 (59.3 %) had SBO involving the affected lamina (L5) and S1 lamina. In contrast, the 3 patients with L3 or L4 spondylolysis had no evidence of SBO. With respect to skeletal age, 23 of the 27 L5 spondylolysis patients (85.2 %) were in the cartilaginous stage while the remaining 4 patients were in the apophyseal stage. CONCLUSION: Lumbar spondylolysis in elementary school age children was commonly a terminal-stage bone defect at L5, which was not necessarily related to history of athletic activity and was sometimes asymptomatic. It was often associated with SBO, indicating a possible congenital predisposition. These findings may provide further insight into the pathogenesis of lumbar spondylolysis.

Percutaneous endoscopic lumbar discectomy utilizing ventral epiduroscopic observation technique and foraminoplasty for transligamentous extruded nucleus pulposus: technical note.

Percutaneous endoscopic discectomy (PED) is a minimally invasive disc surgery that can be performed under local anesthesia and requires only an 8-mm skin incision. For transligamentous extruded nucleus pulposus with foraminal stenosis, it is very hard to remove the migrated mass with a simple transforaminal approach. For such difficult cases, foraminoplasty and an epiduroscopic technique is useful. A 29-year-old man visited the authors' hospital, complaining of low-back and right leg pain. MRI revealed a massive herniated nucleus pulposus with foraminal stenosis. A transforaminal PED was planned to remove the herniated mass. Through the inside-out technique, the base of the herniated mass was removed. Following the foraminoplasty, the cannula was moved into the epidural space. With epidural observation just beneath the nerve root, the extruded transligamentous fragment was confirmed and removed en bloc. Immediately after the surgery, the patient's symptoms resolved. The combination of foraminoplasty and epiduroscopic observation during the transforaminal approach for PED is a useful and reliable technique to remove extruded transligamentous disc fragments.

Hysterical conversion paralysis in an adolescent boy with lumbar spondylolysis.

We describe a case of recurrent hysterical paralysis triggered by low back pain because of lumbar spondylolysis. A 16-year-old male soccer player was referred to our institution with five previous episodes of acute paralysis triggered by severe low back pain. We performed direct surgical repair of the terminal-stage bilateral spondylolysis at L4 using a hook-rod system. His chronic low back pain was completely resolved, and no further episodes of hysterical paralysis have occurred after surgery. Spine surgeons should be aware of possible hysterical conversion paralysis when there is discrepancy between radiological and neurological findings.

Clinical features of patients with pars defects identified in adulthood.

PURPOSE: Lumbar spondylolysis is considered a stress fracture of the pars interarticularis that occurs during growth. However, it is sometimes insidious and identified in adults as pseudoarthrosis, the terminal-stage of spondylolysis. The purpose of this study was to identify the clinical features of patients with terminal-stage spondylolysis that first manifested during adulthood. PATIENTS AND METHODS: Thirty-six patients (21 men, 15 women; mean age 55.8 years; age range 25-77 years) with low back pain (LBP) were studied. In all patients, lumbar spondylolysis had not been diagnosed until the first visit to our hospital. Patient data collected were history of athletic activity and LBP during their growth period and radiological findings, such as spinal level, displacement, and spina bifida occulta (SBO). RESULTS: Among the 36 patients, including a patient with multi-level spondylolysis (L4 and L5), a total of 37 vertebrae with terminal-stage spondylolysis were identified. Twenty-three (89.2 %) of the 37 vertebrae had L5 spondylolysis. Sixteen patients (44.4 %) had no history of athletic activity, 26 (72.2 %) had no experience of LBP during their growth period, and 14 (38.9 %) had neither. Twenty of the 37 vertebrae (70.4 %) involved displacement (grade 1 = 14; grade 2 = 6). In nine patients (25.0 %; eight men, one woman), SBO of the sacrum was accompanied by L5 spondylolysis. CONCLUSIONS: Approximately 90 % of patients with terminal-stage spondylolysis that was first diagnosed in adulthood involved the L5. Also, about 40 % had no history of athletic activity or experience of LBP during their growth period. In addition, only some patients with L5 spondylolysis had SBO, and all but one of these patients was male. This suggests that male patients with L5 spondylolysis may have some congenital predisposition.

State of the art: Intraoperative neuromonitoring in spinal deformity surgery.

Application of deformity correction spinal surgery has increased substantially over the past three decades in parallel with improvements in surgical techniques. Intraoperative neuromonitoring (IOM) techniques,including somatosensory evoked potentials (SEPs), muscle evoked potentials (MEPs), and spontaneous electromyography (free-run EMG), have also improved surgical outcome by reducing the risk of iatrogenic neural injury. In this article, we review IOM techniques and their applications in spinal deformity surgery. We also summarize results of selected studies including hundreds of spinal correction surgeries. These studies indicate that multimodal IOM of both motor and sensory responses is superior to either modality alone for reducing the incidence of neural injury during surgery. J. Med. Invest. 62: 103-108, August, 2015.

State-of-the-art ultrasonographic findings in lower extremity sports injuries.

Athletes sometimes experience overuse injuries. To diagnose these injuries, ultrasonography is often more useful than plain radiography, computed tomography (CT), or magnetic resonance imaging (MRI). Ultrasonography can show both bone and soft tissue from various angles as needed, providing great detail in many cases. In conditions such as osteochondrosis or enthesopathies such as Osgood-Schlatter disease, Sinding-Larsen-Johansson disease, bipartite patella, osteochondritis dissecans of the knee, painful accessory navicular,and jumper's knee, ultrasonography can reveal certain types of bony irregularities or neovascularization of the surrounding tissue. In patients of enthesopathy, ultrasonography can show the degenerative changes at the insertion of the tendon. Given its usefulness in treatment, ultrasonography is expected to become essential in the management of overuse injuries affecting the lower limb in athletes. J. Med. Invest. 62: 109-113, August, 2015.

Foraminoplastic transforaminal percutaneous endoscopic discectomy at the lumbosacral junction under local anesthesia in an elite rugby player.

Percutaneous endoscopic discectomy (PED) is the least invasive disc surgery available at present. The procedure can be performed under local anesthesia and requires only an 8 mm skin incision. Furthermore, damage to the back muscle is considered minimal, which is particularly important for disc surgery in athletes. However, employing the transforaminal (TF) PED approach at the lumbosacral junction can be challenging due to anatomical constraints imposed by the iliac crest. In such cases, foraminoplasty is required in addition to the standard TF procedure. A 28-year-old man who was a very active rugby player visited us complaining of lower back and left leg pain. His visual analog scale (VAS) score for pain was 8/10 and 3/10, respectively. MRI revealed a herniated nucleus pulposus at L5-S level. TF-PED was planned; however, the anatomy of the iliac crest was later found to prevent access to the herniated mass. Foraminoplasty was therefore performed to enlarge the foramen, thereby allowing a cannula to be passed through the foramen into the canal without causing exiting nerve injury. The herniated mass was then successfully removed via the TF-PED procedure. Pain resolved after surgery, and his VAS score decreased to 0/10 for both back and leg pain. The patient returned to full rugby activity 8 weeks after surgery. In conclusion, even with an intracanalicular herniated mass at the lumbosacral junction, a TF-PED procedure is possible if additional foraminoplasty is adequately performed to enlarge the foramen.

Tenosynovial Giant Cell Tumor, Diffuse Type/Pigmented Villonodular Synovitis in a Pars Defect: A Case Report.

STUDY DESIGN: Case report. OBJECTIVE: To describe a rare case of tenosynovial giant cell tumor, diffuse type/pigmented villonodular synovitis (PVNS) in a pars defect in a patient with lumbar spondylolysis. SUMMARY OF BACKGROUND DATE: PVNS rarely occurred in lumbar spine, and no studies in the English literature have reported PVNS in a pars defect in lumbar spondylolysis. METHODS: The patient was a 14-year-old female presented with a 5-month history of low back pain. Plain radiography showed spondylolysis at L5 and computed tomography revealed a 1 × 2-cm slightly eroding tumorous mass at the left L5 pars. On magnetic resonance imaging, the mass showed intermediate intensity and gadolinium enhancement on T1-weighted images (WI) and high intensity on T2-WI and T2 STAR-WI. After undergoing computed tomography-guided needle biopsy, a pathological diagnosis of PVNS was made and total gross resection was performed. RESULTS: The gross appearance and the postoperative pathological diagnosis were consistent with PVNS. The postoperative clinical course was uneventful and postoperative computed tomography and magnetic resonance imaging revealed no residual lesion. CONCLUSION: This is the first report of PVNS occurring in spondylolysis. LEVEL OF EVIDENCE: N/A.

A review of the pathomechanism of forward slippage in pediatric spondylolysis: the Tokushima theory of growth plate slippage.

Spondylolysis is a stress fracture of the pars interarticularis, which in some cases progresses to spondylolisthesis (forward slippage of the vertebral body). This slip progression is prevalent in children and occurs very rarely after spinal maturation. The pathomechanism and predilection for children remains controversial despite considerable clinical and basic research into the disorder over the last three decades. Here we review the pathomechanism of spondylolytic spondylolisthesis in children and adolescents, and specifically the Tokushima theory of growth plate slippage developed from our extensive research findings. Clinically, we have observed the slippage site near the growth plate on MRI; then, using fresh cadaveric spines, we found the weakest link against forward shear loading was the growth plate. We subsequently developed an immature rat model showing forward slippage after growth plate injury. Moreover, finite element analysis of the pediatric spine clearly showed increased mechanical stress at the growth plate in the spondylolytic pediatric spine model compared with the intact pediatric spine. Thus, spondylolysis progresses to spondylolisthesis (forward slippage) in children and adolescents with the growth plate as the site of the slippage. Repetitive mechanical loading on to the growth plate may serve to separate the growth plate and subsequently progress to spondylolisthesis.

Percutaneous endoscopic lumbar discectomy for a huge herniated disc causing acute cauda equina syndrome: a case report.

Microsurgery for lumbar disc herniation that requires surgical intervention has been well described. The methods vary from traditional open discectomy to minimally invasive techniques. All need adequate preanesthetic preparation of patients as general anesthesia is required for the procedure, and nerve monitoring is necessary to prevent iatrogenic nerve injury. Conventional surgical techniques sometimes require the removal of the corresponding lamina to assess the nerve root and herniated disc, and this may increase the risk for posterior instability of the vertebral body. Should this occur, fusion surgery may be needed, further increasing morbidity and cost. We present here a case of lumbar herniated disc fragments causing acute cauda equina syndrome that were endoscopically resected through a transforaminal approach in an awake patient under local anesthesia. Percutaneous endoscopic discectomy under local anesthesia proved to be a better alternative to open back surgery as it made immediate intervention possible, was associated with fewer perioperative complications and morbidity, minimized soft tissue damage, and allowed early rehabilitation with a better outcome and greater patient satisfaction. In addition to these advantages, percutaneous endoscopic discectomy protects other approaches that may be needed in subsequent surgeries, whether open or minimally invasive.

State of the art: Transforaminal approach for percutaneous endoscopic lumbar discectomy under local anesthesia.

Minimally invasive percutaneous endoscopic discectomy (PED) with a transforaminal approach under local anesthesia was started in the late 20th century. As the procedure requires a skin incision of only 8 mm, it is the least invasive disc surgery procedure at present, and owing to advances in instruments and optics, the use of this technique has gradually spread. In Japan, Dr. Dezawa from Teikyo University Mizonokuchi Hospital introduced this technique in 2003. Thanks to his efforts, the number of surgeons who can perform PED has increased, although the number of active PED surgeons is still only around 20. The first author (K.S.) started PED in 2010. In this review article, we explain the state-of-the-art PED transforaminal technique for minimally invasive disc surgery and present three successful cases.