Background: The purpose of this study was to clarify the clinical features of ossification of the posterior longitudinal ligament (OPLL) and extreme ossification at multiple sites. Methods: This prospective study involved patients with a diagnosis of cervical OPLL at 16 institutions in Japan. Patient-reported outcome measures, including responses on the Japanese Orthopaedic Association (JOA) Cervical Myelopathy Evaluation Questionnaire (JOA-CMEQ), JOA Back Pain Evaluation Questionnaire (JOA-BPEQ), and visual analog scale pain score, were collected to investigate clinical status. In each patient, the sum of the levels at which OPLL was located (OP index) was evaluated on whole-spine computed tomography, along with ossification of other spinal ligaments including the anterior longitudinal ligament (OALL), ligament flavum (OLF), supra- and intraspinous ligaments (SSL), and diffuse idiopathic skeletal hyperostosis (DISH). The distribution of OP index values in the study population was investigated, and the clinical and radiologic characteristics of patients in the top 10% were assessed. Results: In total, 236 patients (163 male, 73 female; mean age 63.5 years) were enrolled. Twenty-five patients with OP index ≥ 17 were categorized into a high OP index group and the remainder into a moderate/low OP index group. There were significantly more women in the high OP index group. Patients in the high OP index group also had significantly poorer scores for lower extremity function and quality of life on the JOA-CMEQ and in each domain but not for body pain on the JOA-BPEQ compared with those in the moderate/low OP index group. Patients in the high OP index group had more OALL in the cervical spine and more OLF and SSL in the thoracic spine. The prevalence of DISH was also significantly higher in the high OP index group. In the high OP index group, interestingly, OPLL was likely to be present adjacent to DISH in the cervicothoracic and thoracolumbar spine, especially in men, and often coexisted with DISH in the thoracic spine in women. Conclusion: This prospective cohort registry study is the first to demonstrate the clinical and radiologic features of patients with OPLL and a high OP index. In this study, patients with a high OP index had poorer physical function in the lumbar spine and lower extremities and were also predisposed to extreme ossification of spinal ligaments other than the OPLL.

Background/Objectives: Expansive open-door laminoplasty results in favorable clinical outcomes for cervical myelopathy. However, some postoperative complications associated with surgical invasiveness, such as axial neck pain and kyphosis, have not been resolved. The use of an exoscope, which is a recently introduced novel magnification tool, allows for traditional open-door laminoplasty with minimal invasiveness. Therefore, we propose the use of exoscopic minimally invasive open-door laminoplasty (exLAP) and present its clinical outcomes during the acute postoperative period. Methods: A total of 28 patients who underwent open-door laminoplasty at C3–C6 were reviewed. Of these patients, 17 underwent exLAP (group M) and 11 underwent conventional Hirabayashi open-door laminoplasty (group H). Outcomes were evaluated using numerical rating scale (NRS) scores for neck pain and the frequency of oral analgesic use from postoperative day 1 to 7. Results: The NRS score for neck pain was significantly lower for patients in group M than for those in group H. Conclusions: ExLAP is a novel, practical, and minimally invasive surgical technique that may alleviate the postoperative axial pain of patients with cervical myelopathy.

Background/Objectives: We investigated the impact of ossification of the posterior longitudinal ligament (OPLL) and cervical alignment on K-line assessment, proposed the K-line edge category for transitioning from K-line (+) to (−), and demonstrated a quantitative evaluation using the K-line edge. Methods: The 268 patients with OPLL who underwent computed-tomography-based K-line assessment were retrospectively stratified into three groups [K-line (+)/(±)/(−)]. We graphically plotted their distributions based on the OPLL-occupying ratio (OPLL-OR) and cervical angle (θ C_2–7). Results: The K-line (+), (±), and (−) groups comprised 159, 37, and 72 patients, respectively. The K-line (+) group demonstrated the lowest alignment value at −14.1°, suggesting a potential border for kyphosis at 14°. By examining the K-line (±) region, we successfully identified a clustered group and proposed the “K-line edge” for K-line (±), which was derived as y = 0.98x + 46.82 (R² = 0.67). The K-line edge calculation depended on the OPLL-OR and θ C_2–7 at each cervical level and determined the corresponding value for either OPLL-OR or θ C_2–7. The slope of the K-line edge was almost horizontal at both ends and was steeper in the middle, with the alignment playing a dominant role in the mid-cervical region. The calculated borders were approximately at 12° kyphosis at C4-4/5 and at 11° at C5-5/6. Conclusions: Focusing on K-line (±) identified three major factors during the K-line assessment: the OPLL-OR, cervical alignment (θ C_2–7), and cervical level. The K-line edge could be useful as a quantitative parameter for surgical decision-making.

Background: Posterior decompression with instrumented fusion (PDF) is a conventional surgical procedure performed in patients with massive ossification of the posterior longitudinal ligament (OPLL); however, it is invasive to the posterior cervical tissues. In this report, we introduce a novel PDF technique, exoscopic minimally invasive open-door laminoplasty with pedicle screw fixation (exLAPPS), to treat cervical OPLL, while minimizing posterior tissue damage. Methods: ExLAPPS was indicated for patients with K-line (−) OPLL or a canal occupying a ratio of ≥50%, allowing decompression from C3 to C7. A small midline incision was used for the navigation reference placement and exoscopic minimally invasive open-door laminoplasty, whereas bilateral lateral incisions were utilized for posterior fixation, including pedicle screw insertion, based on the minimally invasive cervical pedicle screw technique. Results: A total of 7 patients with K-line (-) or a canal occupancy ≥50% underwent exLAPPS for cervical OPLL. The mean operative time was 248 min (range, 165–342 min) and the mean blood loss was 320 mL (range, 50–740 mL). Postoperative imaging demonstrated adequate spinal cord decompression in all patients. A total of 52 pedicle screws were inserted, with a pedicle screw deviation rate of 1.9%. Conclusions: ExLAPPS is a minimally invasive surgical technique designed for posterior decompression and fixation in patients with cervical OPLL. In this preliminary case series, the procedure was successfully performed with acceptable operative time, blood loss, and screw placement accuracy. Although the present study did not include a direct comparison with conventional procedures, these preliminary observations suggest that ExLAPPS is a feasible surgical option for selected patients with cervical OPLL.

Background/Objectives: Extraforaminal lumbar interbody fusion provides indirect decompression without entering the spinal canal, but its uptake has been limited by poor visualization and risk of exiting nerve root injury. We describe a minimally invasive exoscopic extraforaminal lumbar interbody fusion (exELIF) technique and evaluate its clinical and radiological outcomes. This study aims to describe the exELIF technique and report its early clinical and radiological outcomes. Methods: Twenty-six patients with lumbar degenerative diseases underwent exELIF using a 3D exoscope (ORBEYE). The procedure was performed through bilateral 30–40 mm posterior incisions. Clinical outcomes were assessed using the Japanese Orthopedic Association score preoperatively and at 1-year follow-up. Postoperative computed tomography evaluated interbody fusion. Operative time, blood loss, and complications were recorded. Results: Mean operative time was 131 ± 51 min, and mean estimated blood loss was 82 ± 99 mL. The mean JOA score improved from 15.2 ± 2.2 to 24.3 ± 2.6, with a mean recovery rate of 66% at 1 year. Interbody fusion was achieved in 96%. In an exploratory CUSUM analysis of 18 single-level fluoroscopy-guided cases, a transition in operative time was observed at approximately the 10th case; operative time and estimated blood loss decreased from 141.5 ± 39.2 min and 89.0 ± 77.8 mL in cases 1–10 to 80.1 ± 6.7 min and 21.2 ± 18.1 mL in cases 11–18 (p < 0.001 and p = 0.035, respectively), indicating a reduction of operative time with accumulated experience rather than a formally established learning curve. Three patients developed transient exiting nerve root symptoms that resolved spontaneously during follow-up. One patient at the L5/S level required revision surgery due to left L5 nerve root palsy caused by posterior migration of the bone graft; this complication led to a modification of the technique, with posterior bone grafting no longer performed at L5/S. Partial screw loosening was observed in 5 patients (19%), all of which were asymptomatic and required no additional intervention. Conclusions: ExELIF provides excellent visualization in deep surgical fields, allowing the use of conventional surgical instruments through minimally invasive incisions. This is an early feasibility report of a single-institution retrospective case series with a heterogeneous cohort and no control group; the present data therefore do not establish superiority over conventional or endoscopic ELIF. Within these limits, exELIF was associated with acceptable early clinical improvement and a high interbody fusion rate, and progressive reduction in operative time with experience suggests that it may be a technically feasible minimally invasive option for selected patients with lumbar degenerative disease and for revision surgery after lumbar decompression.