Introduction: The loss of cervical lordosis or kyphotic change after posterior decompression surgery is one of the potential complications when treating patients with cervical spondylotic myelopathy (CSM). It is necessary to clarify the safety margin of cervical lordosis, including anterior dynamic compression factors for the spinal cord. The minimum distance between K-line and vertebral body or osteophytes (K-line brace height [KLBH]) is an index that allows the quantitative evaluation of anterior dynamic compression factors. In this study, the authors aim to compare clinical outcomes and radiographic parameters, including sagittal alignment, or balance among Group A (flexion KLBH ≥ 4 mm and neutral KLBH ≥ 4 mm), Group B (flexion KLBH < 4 mm and neutral KLBH ≥ 4 mm), and Group C (flexion KLBH < 4 mm and 0 < neutral KLBH < 4 mm).

Methods: A total of 33 consecutive patients were enrolled; the inclusion criteria were cases with CSM, posterior decompression surgery, ages 40 or over at the time of surgery, preoperative neutral K-line (+), and minimum follow-up period of 1 year. The following radiographic parameters were measured: KLBH, local kyphosis angle, segmental range of motion, C2-C7 angle, C7 slope, and C2-C7 sagittal vertical axis. Clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) score for cervical myelopathy, JOA Cervical Myelopathy Evaluation Questionnaire, and Visual Analog Scale. The patients were divided into Group A (n = 13), Group B (n = 14), and Group C (n = 6).

Results: Postoperative JOA score was significantly lower in Group C. The recovery rate of the JOA score was significantly different between Groups A and C. Postoperative neutral KLBH was large in order of Groups A-C. In two cases (6.1%), neutral K-line changed from (+) to (−) after surgery; both cases were in Group C. The number of cases with a preoperative focal kyphosis angle ≥10˚ was significantly smaller in Group A than in Groups B and C.

Conclusions: When performing posterior decompression surgery for patients with CSM, the safety margin of the preoperative neutral KLBH was shown to be ≥4 mm. The preoperative neutral KLBH < 4 mm and focal kyphosis angle ≥10˚ are potential risk factors for the loss of cervical lordosis or kyphotic change. With the above factors, additional measures including partial fusion or correction may be required to prevent the loss of cervical lordosis or kyphotic change.

Introduction: A rapidly growing elderly population with medical comorbidities can benefit from traditional treatment algorithms for pyogenic spondylodiscitis in the lumbar and thoracic spines that are updated to incorporate recent advances in minimally invasive surgery (MIS). We assessed the usefulness of our treatment algorithm that includes percutaneous pedicle screw (PPS) -rod fixation and transpsoas lateral lumbar interbody fusion (LLIF) in 54 patients with pyogenic spondylitis.

Methods: The algorithm first categoried the patients into neurologically intact or neurologically compromised groups. The former group first underwent image-guided needle biopsy followed by conservative treatment with antibiotics and a spinal brace. The latter group underwent an immediate single-stage MIS with non-fused PPS fixation at the infection-free vertebrae at two levels above and below the affected vertebrae followed by posterior exposure for decompression and debridement through a separate midline incision. Twenty patients who did not show a favorable response to conservative treatment underwent additional above-mentioned PPS-rod fixation. The successful eradication of infection followed by spontaneous fusion between the affected vertebrae allowed the removal of the implants where possible. In cases where the infection persisted and/or vertebral bodies were extensively damaged, MIS-LLIF was performed for direct access to the infected focus with further debridement and iliac bone grafting.

Results: Percutaneous imaged-guided needle biopsy, blood culture, or surgical sampling identified the causative bacteria in 33 of the 54 cases (61.1%), including gram-positive organisms in 30 (90.9%) and gram-negative organisms in 3 (9.1%) cases. Conservative management alone improved infection to the healed stage in 12 patients. Of the 39 patients who needed surgical intervention, 35 fully recovered with only minimally invasive posterior surgery, including 20 patients who initially underwent conservative management followed by additional non-fused PPS0-rod fixation. Posterior surgery failed to adequately eradicate infection in 3 patients and they had to undergo additional MIS-LLIF for further debridement and iliac bone grafting. In the remaining 1 patient, the infection improved to the healed stage, but the extensive bone defect required a revision surgery with single-level MIS-LLIF and PPS-rod fixation after the removal of the previously placed implants.

Conclusions: Placement of non-fused PPS-rod in infection-free vertebrae alone or in combination with posterior debridement through a separate midline incision was effective in local stabilization without contamination of the metal implant from the infected tissue. MIS-LLIF allowed direct access to the infected focus for further debridement and bone grafting in cases of extensive vertebral body damage.

Introduction: The rate of postoperative neurological deterioration is reportedly high in patients with thoracic ossification of posterior longitudinal ligament (T-OPLL). However, the neurological deterioration details after anterior decompression through a posterior approach are unknown.

Methods: In total, 24 patients with T-OPLL (14 males and 10 females; mean age 49 years), who underwent anterior decompression through a posterior approach, were included. The rate of neurological deterioration, timing of occurrence, reoperation, and time required for recovery were investigated. Patients were divided into two groups according to the occurrence of postoperative neurological deterioration, and the following factors were compared: corresponding spinal level, body mass index, duration of disease, preoperative JOA score, morphological type of OPLL, coexisting ossification ligamentum flavum, ossification-kyphosis angle, canal occupancy ratio, thoracic kyphosis, kyphosis correction angle, MEP derivation, number of laminectomy, number of pediculecutomy, dural tear, operative duration, and blood loss.

Results: Postoperative neurological deterioration occurred immediately after the surgery in 4 patients (16.7%). No patient underwent reoperation, and muscle strength recovered within 12 weeks. Those with neurological deterioration had low preoperative JOA scores (p = 0.02), a large number of laminectomy (p = 0.002), and long operative duration (p = 0.005).

Conclusions: The rate of postoperative neurological deterioration was lower than that previously reported. Prolonged compression to the spinal cord, which increased in the prone position, presumably caused neurological deterioration.

Introduction: Middle column injury is a poor prognostic factor for the conservative treatment of osteoporotic vertebral fractures (OVF). The effects of the degree of middle column injury and external fixation methods (body cast, hard, or soft brace) on bone union and deformity of the vertebral body were examined.

Methods: Of the patients with fresh thoracolumbar OVF without paralysis who were hospitalized and treated within 1 month of onset, 224 were followed up after 1 year. The degree of middle column injury was evaluated by flexion CT, reflecting the loading position, and the patients were divided into four groups according to the occupancy rate of the bone fragments that had entered the spinal canal (occupancy rate).

Results: In Group A (occupancy rate >50%: 7 cases), the union rate was significantly higher in a body cast than in a hard brace (p < 0.05); in Groups B and C (occupancy rates 30%-50% and <30%: 26 and 164 cases), the union rate was significantly higher in a body cast than in a soft brace (p < 0.01 and 0.05). There was a trend toward improvement in the anterior vertebral margin height and fragment occupancy in the spinal canal in Groups A, B, and C, respectively.

Conclusions: A body cast is useful for conservative treatment of OVF with middle column injury.

Introduction: The purpose of this study was to elucidate the clinical characteristics of delayed-onset surgical site infections (SSI) compared with those of early-onset SSIs.

Methods: Of the 1555 patients who underwent spinal instrumentation surgery, 31 (2.0%) required additional surgery because of surgical site infection. Background factors, such as age, gender, medical history, surgical factors, clinical findings at the time of onset (including wound appearance, imaging, and blood tests), causative microorganisms, presence of implants, and duration until normalization of C-reactive protein (CRP) were investigated. Delayed-onset SSIs were defined as those occurring after 30 days postoperatively and were compared with early-onset SSIs.

Results: A total of 35% of the cases were classified as delayed-onset SSIs, with a median onset period of 79 days. Compared with early-onset SSIs, delayed-onset SSIs exhibited a lower incidence of visible wound abnormalities and lower CRP levels. In delayed-onset SSIs, imaging studies revealed significant differences in lytic changes on CT scans and bone marrow edema on MRI. P. acnes was the predominant causative microorganism in delayed-onset SSIs (early-onset vs. delayed-onset: 2 cases/20, 5 cases/11), and the rate of implant preservation was significantly lower in delayed-onset cases (early-onset vs. delayed-onset: 100%, 45%). However, no significant difference was observed in the time to CRP normalization or treatment duration between the two groups.

Conclusions: Delayed-onset SSIs often manifest with subtle clinical signs, progress insidiously to cause bone destruction, and exhibit marked instability when detected, often requiring implant removal. In patients with persistent postoperative back pain and delayed bone union, consideration of this clinical condition is essential.

Introduction: We assessed the outcomes of balloon kyphoplasty (BKP) as a monotherapy technique, focusing on the walking ability of patients with osteoporotic vertebral fractures (OVF) and lower-limb neurological symptoms.

Methods: BKP was performed as the initial surgery in 34 cases of patients with lower-limb neurological symptoms suspected to be caused by OVF. The patients' walking ability, neurological symptoms, lumbar back pain, and need for additional surgery were investigated pre- and post-operatively. Patients were categorized into two groups, those whose neurological symptoms improved to a level that did not affect activities of daily living (ADL) after BKP monotherapy (BKP Monotherapy Successful Group) and those who required additional surgery due to persistent symptoms affecting ADL (Additional Surgery Group). The preoperative neurological symptoms and imaging findings of the two groups were compared.

Results: In all cases, walking ability score significantly increased from preoperative 2.2±1.1 to postoperative 4.3±0.8 during one month. In 25 cases (73.3%), neurological symptoms improved to no longer affecting ADL (BKP Monotherapy Successful Group), whereas nine cases (26.5%) showed no or insufficient improvement, necessitating additional surgery (Additional Surgery Group). There were no significant differences in preoperative neurological symptoms and imaging findings between the two groups.

Conclusions: BKP monotherapy was performed in 34 cases of patients with OVF with lower-limb neurological symptoms, resulting in successful alleviation of neurological symptoms in 25 cases (73.5%) and significant improvement in walking ability scores. No factors predicting an improvement in neurological symptoms with BKP monotherapy could be identified preoperatively.

Introduction: Biportal endoscopic spine surgery (BESS) or unilateral biportal endoscopy (UBE) is an endoscopic procedure that creates two portals (camera and working portals) and performed under perfusion. We utilized this technique in cases of minimally recurrent lumbar disc herniation (rLDH) to elucidate its usefulness for surgical treatment of rLDH.

Methods: Fifteen patients who underwent UBE/BESS herniectomy for postoperative rLDH were included in our study. Details of the initial surgery, approach to reoperation, duration from initial surgery to reoperation, operative time, and modified MacNab criteria were investigated as postoperative result.

Results: Time from initial surgery to reoperation ranged from 4 days to 5 years. The mean operative time was 64 min (22-66 min). The modified MacNab criteria at the final follow-up were excellent in 27%, good in 60%, and fair in 13% cases.

Conclusions: UBE/BESS is considered safe for recurrent hernias because it is an endoscopic procedure providing high degree of freedom in handling instruments used in microscopic surgery and a bright, magnified field of view. In our report, the modified MacNab criteria were excellent or good in 87% of cases. Furthermore, no intraoperative complications were observed, which is comparable to the results in existing reports. This study reports cases of rLDH treated via UBE/BESS without intraoperative complications and provided good results.

Introduction: We hypothesized that the postoperative outcome can be changed by the K-line in the neck-extended position (EK-line).

Methods: The study retrospectively reviewed the patients who underwent laminoplasty and were observed for >1 year after surgery. We defined EK-line (+) as cases where the peak of OPLL exceeds the K-line but does not exceed the EK-line, and EK-line (−) as cases where the peak of OPLL exceeds the EK-line. The Kruskal-Wallis test was used to compare the postoperative change in the range of motion (ROM) on cervical X-ray and the Japanese Orthopedic Association score (JOA score) between patients with K- (+), EK- (+), and EK-lines (−); the Wilcoxon test was used to compare the two groups.

Results: There were 62 cases: 44 were K-line (+), 12 were EK-line (+), and 6 were EK-line (−). There were significant differences in the extension ROM and JOA score recovery rate between the K- (+), EK (+), and EK-lines (−) (58% vs 50% vs 27%, p = 0.03). The JOA score recovery rate was significantly lower in the EK-line (−) than in the K-line (+).

Conclusions: Concerning the K-line (−) patients, EK-line (+) patients had comparable results to K-line (+) patients. EK-line is possibly a useful indicator of surgical selection for cervical OPLL.

Introduction: I underwent transthoracic L1/2 interbody fusion and experienced extensive spinal canal stenosis of T11/12/L1, L1/2, and L3/4 as an adjacent segment disease 30 years later. The spinal cord and cauda equina coexist in the thoracolumbar area, making level diagnosis complicated. We report the application of new percutaneous full endoscopic laminoplasty (PFEL) adapted to the different figures of the facet joints.

Case Report: In 1992, at age 46 years, resection of nucleus pulposus was performed for L1/2 intervertebral disc herniation using a percutaneous nucleotomy. However, severe pain due to interbody instability occurred, and transthoracic interbody fusion for L1/2 was performed 1 month later. Thirty years later, at age 76 years, ossification of ligamentum flavum at T11/12/L1 (epiconus syndrome), spinal canal stenosis at L1/2 of the fusion segment with kyphosis and right rotation deformity (conus medullary syndrome), and spinal canal stenosis at L3/4 (cauda equina syndrome) appeared. I experienced weakness in the lower leg muscles, frequent calf cramps, and moderate left lumbar buttock pain released in spine flexion. On December 24, 2022, PFEL at L3/4 was conducted. The left-side pain and calf cramps subsided. However, 2 weeks later, severe pain in the right buttocks increased with right flexion and rotation and incontinence appeared. Since the facet joint of T12/L1 had a sagittal plane configuration, and the lamina and inferior articular processes were narrow, if a unilateral approach for bilateral compression (UBD) was selected, the ipsilateral inferior articular process would almost disappear. On January 16, 2023, PFEL with a bilateral approach for contralateral decompression (BCD) was conducted. At the same time, on T11/12, PFEL with UBD was performed. Although leg muscle weakness and incontinence improved, momentary mild right lumbar buttock radiating pain and mild urinary urgency persisted. On April 24, 2023, PFEL of UBD for L1/2 was performed. The results were satisfactory.

Conclusions: Thoracolumbar junction presents with complicated symptoms, such as upper central (spinal cord) and lower peripheral (cauda equina) nerves appearing mixed. Because the T12/L1 facet joint has a sagittal plane configuration, it is prone to instability after laminectomy, and interbody fusion is recommended. However, we devised a minimally invasive method such as BCD that could sufficiently decompress and avoid interbody fusion.

Introduction: Intradural extramedullary spinal metastases (IESMs) of malignant tumor are rare with no established treatment guidelines. Lung cancer and breast cancer are the most frequent primary lesions; however, few reports exist of spinal intradural extramedullary metastases from colorectal cancer.

Case Report: We present a case of a 69-year-old male, who had a history of treatment for rectal cancer 5 years ago. He subsequently presented with lower back pain, bilateral leg pain, paraplegia, as well as bladder and rectal dysfunction due to IESMs. The tumor was totally resected with a surrounding inner layer of dura mater and arachnoid membrane. The recovery of walking function occurred quickly, where the patient was able to walk independently in 4 weeks after operation. Postoperatively, he remained highly active until his death due to the primary disease 2 years and 2 months.

Conclusions: IESMs are generally associated with a poor prognosis. However, surgical treatment may contribute to improving quality of life despite difficulty in improving the prognosis. Surgical treatment should be considered only in some cases of this disease.