Transforaminal (TF) percutaneous endoscopic surgery for the lumbar spine under the local anesthesia was initiated in 2003 in Japan. Since it requires only an 8-mm skin incision and damage of the paravertebral muscles would be minimum, it would be the least invasive spinal surgery at present. At the beginning, the technique was used for discectomy; thus, the procedure was called PELD (percutaneous endoscopic lumbar discectomy). TF approach can be done under the local anesthesia, there are great benefits. During the surgery patients would be in awake and aware condition; thus, severe nerve root damage can be avoided. Furthermore, the procedure is possible for the elderly patients with poor general condition, which does not allow the general anesthesia. Historically, the technique was first applied for the herniated nucleus pulposus. Then, foraminoplasty, which is the enlargement surgery of the narrow foramen, became possible thanks to the development of the high speed drill. It was called the percutaneous endoscopic lumbar foraminoplasty (PELF). More recently, this technique was applied to decompress the lateral recess stenosis, and the technique was named percutaneous endoscopic ventral facetectomy (PEVF). In this review article, we explain in detail the development of the surgical technique of with time with showing our typical cases.

Clinical review of pediatric patients with lumbar spondylolysis and biomechanical analysis using finite-element lumbar spine model. To evaluate the usefulness of the signal changes observed on MR images of the pedicle for the early diagnosis of spondylolysis, and to investigate the pathomechanism of the signal changes based on the stresses in pedicles, as predicted using finite-element analyses. Furthermore, to evaluate the usefulness of the signal change to predict the bony healing following conservative treatment. Since early-stage spondylolysis can achieve osseous healing conservatively, it is important to diagnose this disorder as early as possible. Presently, there is no well-established, noninvasive, and reliable diagnostic tool for the early diagnosis. Thirty-seven pediatric patients with spondylolysis were included. Sixty-eight defects were examined and their stages as revealed on CT scans were recorded. High signal changes (HSC) of the pedicles on axial T2-weighted MRI were compared with the CT-based stages of the defect. Among them, 16 patients, including 15 boys and 1 girl, were treated conservatively for at least a 3-month period. Bony healing of the fracture site was evaluated on CT, and the results were compared between two groups with or without HSC at the initial consultation. Using a three-dimensional nonlinear finite-element model of the L3–L5 segment, stress distributions in the pars and pedicle regions were analyzed in response to 400 N compression and 10.6 Nm moment. Based on CTs, 68 pars defects were classified as follows: 8 very early, 24 late-early, 16 progressive, and 20 terminal stages. All defects in very early and late-early stages (100%) showed HSC on T2-weighted MRI at the ipsilateral pedicle. Among 16 progressive stages, eight (50%) showed HSC, while no defects of the terminal stage (0%) were found to have HSC. In total, 29 pars defects were treated conservatively out of 16 patients. In 19 of the HSC positive defects, 15 (79%) showed bony healing after the conservative treatment, whereas none of the 10 HSC negative defects (0%) showed any healing. The results were statistically significant at P < 0.05 (χ2). Stress results from the finite-element model indicated that pars interarticularis showed the highest value in all loading modes, and the pedicle showed the second highest. The correlation between the high stresses in the pedicle and the corresponding HSC suggest that signal changes in MRI could be used as an indicator for early diagnosis of spondylolysis. The HSC of the pedicle provided useful information to diagnose early stage spondylolysis. Furthermore, the HSC may be a good indicator as to whether a bony union will result from conservative treatment.

Background: Unilateral spondylolysis is common in youths; its clinical and biomechanical features, especially effects on the contralateral side, are not fully understood. Hypothesis: Unilateral spondylolysis predisposes the contralateral side to stress fracture, especially in athletes actively engaged in sporting activities involving torsion of the trunk. Study Design: Case series and descriptive laboratory study. Methods: Thirteen athletes younger than age 20 with unilateral spondylolysis were included. The contralateral pedicle and pars of spondylolytic vertebrae were examined using computed tomography and magnetic resonance imaging. Using a finite element model of the intact ligamentous L3-S1 segment, stress distributions were analyzed in response to 400-N axial compression and 10.6-N.m moment in flexion, extension, lateral bending, and axial rotation. Unilateral spondylolysis was created in the model at L5. The stress results from the unilateral defect model were compared to the intact model predictions and correlated to the contralateral defects seen in patients. Results: Among 13 patients, there were 6 early-, 2 progressive-, and 5 terminal-stage defects. Three (23.1%) showed contralateral stress fracture. Among them, 2 belonged to the progressive-stage and 1 to the terminal-stage spondylolysis group. The remaining 4 patients in the terminal defect group showed stress reactions, such as sclerosis at the contralateral pedicle. In the finite element analysis model with an L5 left spondylolysis, the stresses at the contralateral and pars interarticularis were found to increase in all loading modes, with increases as high as 12.6-fold compared to the intact spine. Conclusions: Unilateral spondylolysis could lead to stress fracture or sclerosis at the contralateral side due to an increase in stresses in the region. Clinical Relevance: Surgeons should be aware of possibility of contralateral stress fractures in cases in which patients, especially athletes engaged in active sports, show unilateral spondylolysis and persistent low back pain complaints.

It has been noted that bony union of a pars defect can be achieved in children if they wear a trunk brace. Our aim was to evaluate how the stage of the defect on CT and the presence or absence of high signal change in the adjacent pedicle on T2-weighted MRI were related to bony healing. We treated 23 children conservatively for at least three months. There were 19 boys and four girls with a mean age of 13.5 years (7 to 17). They were asked to refrain from sporting activity and to wear a Damen soft thoracolumbosacral type brace. There were 41 pars defects in 23 patients. These were classified as an early, progressive or terminal stage on CT. The early-stage lesions had a hairline crack in the pars interarticularis, which became a gap in the progressive stage. A terminal-stage defect was equivalent to a pseudarthrosis. On the T2-weighted MR scan the presence or absence of high signal change in the adjacent pedicle was assessed and on this basis the defects were divided into high signal change-positive or -negative. Healing of the defect was assessed by CT. In all, 13 (87%) of the 15 early defects healed. Of 19 progressive defects, only six (32%) healed. None of the seven terminal defects healed. Of the 26 high signal change-positive defects 20 (77%) healed after conservative treatment whereas none of the high signal change-negative defects did so. We concluded that an early-stage defect on CT and high signal change in the adjacent pedicle on a T2-weighted MR scan are useful predictors of bony healing of a pars defect in children after conservative treatment.

Object: Various kinds of trunk braces have been used to achieve bone healing in cases of pediatric lumbar spondylolysis. However, the optimal brace for achieving bone healing is unclear. The purpose of the present study was to determine in what types of spondylolysis bone healing can be achieved and how long it takes. Methods: In this prospective study, 63 pars interarticularis defects (spondylolysis) among 37 patients who were younger than 18 years (mean 13.5 ± 2.7 years) were treated using a hard brace. The youngest patient was 8 years old. Based on the results of CT scanning, the lyses were classified into 3 categories: early, progressive, and terminal defects. Progressive defects were further divided into 2 types according to STIR MRI findings: those with high signal intensity at the adjacent pedicle and those with low signal intensity (that is, a normal appearance). A hard brace, such as a molded plastic thoracolumbosacral orthosis, was used to immobilize the trunk. Approximately every 3 months, CT scanning was performed to evaluate bone healing until approximately 6 months. Results: The union rates were 94%, 64%, 27%, and 0% for the early, progressive with high signal intensity, progressive with low signal intensity, and terminal defects, respectively. It was noted that no terminal defect was healed using conservative treatment. The mean time to healing among the defects that showed bone healing was 3.2, 5.4, and 5.7 months for the early, progressive with high signal intensity, and progressive with low signal intensity groups, respectively. Conclusions: Patients with early-stage defects are the best candidates for conservative treatment with a hard brace because more than 90% of such cases can be healed in 3 months.

Background: Endoscopic lumbar decompression is useful for the treatment of various spinal conditions and is being performed in an increasing number of patients worldwide. We reviewed the surgery-related complications in patients who underwent endoscopic surgery and discuss the learning curve for this procedure. Methods: Since the first case in August 2000, a total of 138 patients have undergone endoscopic posterior decompression surgery. Of these, there were 74 patients with Herniated Nucleus Pulposus (HNP), 57 with Lumbar Canal Stenosis (LCS), and 7 with other conditions. From 2003 to 2005, the senior surgeon took a sabbatical, and no endoscopic surgery was conducted. We divided the cases based on the date of surgery: there were 62 patients in the early (E) group (before September 2003), and 76 in the late (L) group (from January 2006 to April 2008). We compared the incidence of surgery-related complications between 2 disease types as well as between the E and L groups. Results: We encountered 11 complications, which included 6 dural tears, 2 post-surgical hematomas, 2 neural complications and 1 fracture of the inferior articular process. The incidence of surgery-related complications was 8.6%. The incidences of complications were 8.1% and 9.3% for HNP and LCS, respectively, and 11.3%, and 5.3% in the E and L groups, respectively. The incidence was particularly high (16.7%) in the E group with LCS. Conclusion: There is a steep learning curve for endoscopic surgery. Based on the data, surgeons should start performing endoscopic techniques for LCS after gaining enough experience of endoscopic surgery for HNP.