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Background: Hirayama disease (HD) is characterized by slow progression of muscle atrophy without sensory disturbance in a single upper extremity in adolescent boys. HD can be treated using both conservative measures and surgery. However, the optimal treatment remains controversial., Case Presentation: We have encountered an 18-year-old man with HD who presented to us with a 2-year history of progressive muscle atrophy and weakness of the left upper extremity. He underwent posterior cervical fusion surgery in the extended position without decompression. As of 5 years postoperatively, there has been no deterioration of his muscular atrophy and weakness and his condition has mildly improved. He was able to return to daily life and work with no difficulty., Conclusions: Although cervical fusion surgery has several risks, including adjacent segment disease, posterior spinal fusion surgery without decompression in the short segment can be considered as a surgical option for HD. J. Med. Invest. 71 : 298-302, August, 2024.

Foraminal stenosis is one of the types of lumbar spinal stenosis. The pathology can be treated minimally invasively by full-endoscopic spine surgery (FESS). The final challenge in transforaminal FESS is foraminal stenosis in patients with stable isthmic spondylolisthesis at L5. This article provides a step-by-step explanation of how to achieve complete decompression. A cannula of 8 mm in diameter is docked at the base of the superior articular process of the sacrum. The pars crisscross that consists of the superior articular process at S1, the floating lamina, the inferior articular process at L4, and the pars ragged edge is then clearly seen endoscopically. Visualization of the pars crisscross is key to successful decompression. Starting with the superior articular process at S1, followed by partial removal of the floating lamina. Next, the tip of the inferior articular process at L4 is removed. The pars ragged edge is then carefully shaved. Finally, decompression of the exiting nerve root at L5 is confirmed. This report provides the first step-by step description of full-endoscopic decompression of foraminal stenosis under local anesthesia in patients with stable L5 isthmic spondylolisthesis, which we have named "full-endoscopic pars crisscross decompression". J. Med. Invest. 71 : 191-196, August, 2024.

Purpose : To compare the effectiveness of O-arm navigation with that of conventional fluoroscopic guidance in corrective posterior fixation for cervical spinal injury. Methods : This retrospective comparative study involved 11 consecutive patients who underwent corrective posterior fixation using O-arm navigation or conventional fluoroscopy for cervical spinal injury between February 2016 and May 2021. Patient-specific characteristics (age and sex), number of screws, number of pedicle screws, accuracy of pedicle screw insertion, number of vertebral bodies fixed, operating time, and length of hospital stay were analyzed using the t-test. A P-value  < 0.05 was considered statistically significant. Results : Corrective posterior fixation was performed under O-arm navigation in 5 patients and under conventional fluoroscopic guidance in 6. A significantly greater number of pedicle screws was used in the O-arm group (6.4 vs 2.7, P = 0.046). According to the Neo classification for pedicle screw placement, there were no grade 2 or 3 breaches. No other items showed a significant difference between the groups (P > 0.05). Conclusion : O-arm navigation can improve the accuracy of cervical pedicle screw insertion. Its introduction could expand the indications for use of pedicle screws in posterior fixation of cervical spinal injury beyond those that are possible using conventional fluoroscopy. J. Med. Invest. 69 : 273-277, August, 2022.

Purpose : To analyze extraosseous signal changes (ESCs) on magnetic resonance imaging (MRI) in pediatric patients with stress fractures occurring in the lamina. Methods : This study was a retrospective review of 69 consecutive pediatric patients with stress fractures occurring in the lamina. We analyzed MRI scans obtained at the first presentation. Results : We used mainly axial short tau inversion recovery images acquired through the pedicle of these 84 fracture sites to identify the ESCs. These were then divided into three groups: "invisible" when no ESC was detected, "periosteal" for ESC seen on only the dorsal side of the lamina, and "perimuscular" for ESC distinctly spread around / in the paravertebral muscles. In total, 78 (92.9%) fracture sites showed ESCs on the dorsal side of the lamina among which 72 ESCs were located on only the "dorsal" side, while 6 ESCs were on the ventral side against the transverse process. Conclusion : ESCs on MRI were detected in more than 90% of patients before stress fracture became apparent in the lamina, which was considered similar to findings of periosteal thickening / edema detected at the onset of stress fracture in long bone. J. Med. Invest. 68 : 136-139, February, 2021.

In this report, we presented a 65 year-old male case having right leg pain due to L5 radiculopathy. Based on the radiological examination including CT, MRI and radiculography, double crash impingement of L5 nerve root due to L4-5 lateral recess and L5-S foraminal stenosis was diagnosed. Because of the strong pain, he could not work anymore. His job was a general manager of big hospital, he needed to return to job as soon as possible. We decided to conduct the full-endoscopic decompression surgery of ventral facetectomy (FEVF) for L4-5 lateral recess stenosis and foraminoplasty (FELF) for L5-S foraminal stenosis. The technique can be done under the local anesthesia with only 8 mm skin incision; thus, it must be the least invasive spine surgery. Soon after the surgery, he could return to the original job as a general manager. In conclusion, the full-endoscopic decompression surgery for the spinal canal stenosis such as FELF and FEVF would be minimally invasive procedure and it enable patients the quick return to the original activity. J. Med. Invest. 67 : 192-196, February, 2020.

Objective : Infectious spondylodiscitis (IS) is rarely seen in healthy elementary school age children. Conservative treatment with antibiotics is usually preferable but sometimes fails because of the low identification rate of the pathogen by percutaneous needle biopsy. When surgical treatment is indicated, selecting the appropriate procedure is crucial in terms of invasiveness for such young children. Case report : We present the case of a 9-year-old otherwise healthy girl with IS who successfully underwent debridement and identification of the causative pathogen using full endoscopic discectomy (FED) system. Methicillin-susceptible Staphylococcus aureus was identified on several cultures of samples. Immediately after the surgery, the LBP was significantly decreased and the remittent fever resolved dramatically. At the 1-year follow-up, she had no symptoms and plain radiographs showed bony fusion. Conclusion : This is the first report on IS in elementary school-age children treated with the FED system. Debridement using this system could provide minimally invasive and effective curettage of the infected disc space and can be helpful in identifying the pathogen even for small children. J. Med. Invest. 67 : 351-354, August, 2020.

INTRODUCTION : The pathology of lumbar spondylolysis is generally thought to begin with a stress fracture in adolescence. Stress fractures of the lower extremities occur in watershed areas with a poor vascular supply because of an inability to respond to stress and heal. This pathology has not been well researched in the lumbar spine. The aim of this study was to evaluate the distribution of the spinal arteries in patients with lumbar spondylolysis. METHODS : The extraosseous distribution of the arteries around the pars interarticularis was retrospectively investigated in 14 patients with colon cancer who underwent abdominal contrast-enhanced computed tomography (CE-CT) as part of a preoperative assessment at our hospital and were found to have spondylolysis at L5. RESULTS : All patients were found to have terminal-stage spondylolysis at L5 (1 unilateral, 13 bilateral). L5 segmental artery was absent in all cases. However, separate spinal arteries supplying the pars interarticularis at L5 were found above and below the transverse process at this level. CONCLUSION : All the patients had two separate arteries originating from the cranial and caudal sides that distributed to the superior and inferior articular processes, suggesting that the pars interarticularis is a posterior element containing a vascular watershed area. J. Med. Invest. 67 : 62-66, February, 2020.

In this paper, we present 2 cases of herniated nucleus pulposus (HNP) combined with the residual bony fragment of apophyseal ring fracture. HNP typically exists at the narrow lateral recess formed by the bony fragment, and so it has been reported that symptoms may persist. Case 1 was a 22-year-old man, a high-level javelin thrower and Paralympic athlete. He had a history of persistent pain for 4 years due to HNP, and so we performed surgical removal. Case 2 was a 23-year-old male professional baseball player. He was referred to us only 17 days after the onset of pain and presented with muscle weakness, a feature which may prolong the clinical course in addition other features such as pain. Thus, we performed a comparatively quick intervention of surgical removal. In both cases, we had excellent clinical outcomes and better function and performance. In conclusion, in cases with HNP and apophyseal ring separation, surgical intervention in the comparatively early phase can be recommended, particularly if the patients desire quick return to their original level of activity. J. Med. Invest. 66 : 358-361, August, 2019.

A 73-year-old woman complained of right medial side of scapular pain associated with winged scapula to miss without observing the back in minute detail. Additional treatment was required due to overlooking caused by insufficient examination. We performed micro-endoscopic foraminotomy that provided the disappearance of scapular pain and improvement of winged scapula in relatively early. It was commonly said that winged scapula is an extremely rare condition that causes dysfunction of the upper extremities. We suggest that there are the meaning of winged scapula in diagnosis and the importance of physical examination. Further studies should be required to research the morbidity of winged scapula associated with cervical disease. By sharing our experience of this attention arousing case, we provide information not to repeat the same mistakes. J. Med. Invest. 66 : 340-343, August, 2019.

Purpose : To evaluate the stabilizing effects of a Fit Cure-Spine® semi-rigid thoracolumbar orthosis and wearer satisfaction after lumbar surgery. Methods : In study 1, the spinal angle, spinal motion angle, and distribution of load were measured in 8 adult male volunteers when the orthosis was worn (1) with no custom-made stay (CMS), (2) with a CMS in the prone position (P-CMS), and (3) with a CMS in the prone position and decreased lordosis (DP-CMS). In study 2, pain scale scores and responses to a questionnaire were recorded in 40 consecutive patients who underwent lumbar spinal surgery in our hospital. Results : In study 1, the mean lumbar lordosis when standing was similar to that in the prone position. When the trunk was bent forward, loads on the back support in P-CMS and DP-CMS were concentrated at the center of the CMS, unlike those for No-CMS. In study 2, there was a significant decrease in postoperative wound pain after wearing the Fit Cure-Spine orthosis for 2 weeks. Most patients who wore the orthosis were satisfied with their pain outcome. Conclusion : Adjustment to lumbar lordosis and the prone position was restricted in volunteers wearing the Fit Cure-Spine with a CMS. J. Med. Invest. 66 : 275-279, August, 2019.

INTRODUCTION Titanium (Ti) coated polyether ether ketone (PEEK) interbody cages (IBCs) have been introduced to overcome any disadvantages. The purpose of this study was to investigate the radiological outcomes of lumbar interbody fusion (LIF) surgery using the Ti-coated PEEK IBC with a minimum of 1-year of follow-up. METHODS A total of 26 intervertebral spaces in consecutive 21 patients who underwent posterior/transforaminal LIF using the Ti-coated PEEK IBC were evaluated. Rates of bone union, screw loosening, cage subsidence and bone cyst formation around the endplate were evaluated on computed tomography scans acquired at least 1 year postoperatively. RESULTS AND DISCUSSION At the 1-year follow-up, bone fusion was achieved in 23 (88.4%) of 26 intervertebral spaces. Cagesubsidence was found in 5 intervertebral spaces ; however,bone fusion was achieved in all these spaces. Bone cysts formed in 4 intervertebral spaces and 4 of 94 screws were found to be loosened. Three of the loosened screws were found in vertebral bodies adjacent to intervertebral spaces with nonunion. However, there was no association between these events. Although more scientific evidence is required to determine the advantages of Ti-coated PEEK IBCs, we believe the clinical outcomes achieved were favorable at the 1 year minimum follow-up. J. Med. Invest. 66 : 119-122, February, 2019.

Background : There is few reports evaluated accurately the pain generator of low back pain in elite athletes. The purpose of this report was to show case series and to investigate the cause of unidentified low back pain of elite athletes. Methods : Twenty-three adult elite athletes consulted our sports spine clinic to seek a second opinion for low back pain between April 2013 and March 2016. Their cause of low back pain had not been identified by nearby doctor. Spine surgeons had diagnosed using diagnostic injection and STIR-MRI and the final diagnosis made by the spine surgeon were collected. Results : The mean age of 23 patients (16 male, 7 female) was 30.4 years. The most common sport played was baseball. The final diagnosis made by a spine surgeon was as follows : disc related low back pain (n = 12), facet joint arthritis (n = 5), vertebral endplate injury (n = 4), early-stage lumbar spondylolysis (n = 1), supraspinous ligament injury (n = 1). Conclusions : A thorough medical interview, careful physical examination, appropriate diagnostic imaging, and injection block examination can effectively identify the cause of low back pain. J. Med. Invest. 66 : 252-257, August, 2019.

Full-endoscopic spinal surgery was first developed for the lumbar herniated nucleus pulposus. Mainly, there are two types in the full-endoscopic lumbar surgery : i.e., transforaminal (TF) and interlaminar approach. The surgery can be done under the local anesthesia for the TF approach ; therefore, we need to further develop the TF approach to variety of the spinal disorders. Recently, the TF full-endoscopic surgery has been applied for the spinal canal stenosis. First, transforaminal full-endoscopic lumbar foraminoplasty for the foraminal stenosis ; then, transforaminal lumbar lateral recess decompression for the lateral recess stenosis has been developed. Finally, we have developed the surgical technique to decompress the central stenosis via TF approach under the local anesthesia. Prior to initiate the clinical case, we have attempted the lumbar undercutting laminectomy using a fresh cadaveric spine. After we technically confirmed that the transforaminal full-endoscopic lumbar undercutting laminectomy (TE-LUL) is possible, we applied the technique to the patient whose lung capacity did not allow general anesthesia. The 72 years old female patient with central canal stenosis could be improved her left leg pain and muscle weakness after TE-LUL under the local anesthesia. In this paper, we introduce the surgical technique of the TE-LUL and discuss of the efficacy of the TE-LUL. J. Med. Invest. 66 : 224-229, August, 2019.

Ligamentum flavum (LF) hypertrophy is one of the main factors of lumbar spinal canal stenosis (LSCS). The primary object of this study is to clarify the existence of epiligament in the LF and its role in hypertrophy, and to develop an LF hypertrophy animal model. A cadaveric spine from a 30-year-old man was used to investigate the existence of epiligament in LF. Five LF samples from LSCS patients were obtained to evaluate hypertrophied LF. To create a rat model, we destabilized the lumbar spine. Each LF was sagittally cut for histological evaluation. The epiligament was clearly evident in normal LF specimens, which stained pink on Elastica van Gieson and green on Masson Trichrome. One layer was observed on the dural side and another on the dorsal side of the LF. LSCS patients had an enlarged dorsal epiligament, at around 30 times that of the regular thin epiligament on the dural side. The destabilized rat model showed an enlarged dorsal epiligament, with a mean thickness 8-fold that of the control. LF hypertrophy may be due to enlargement of the dorsal epiligament. Mechanical loading of the LF is an important factor for inducing hypertrophy in the rat model. J. Med. Invest. 65:85-89, February, 2018.