Naoki Notani

Analysis of the Relationship between Ligamentum Flavum Thickening and Lumbar Segmental Instability, Disc Degeneration, and Facet Joint Osteoarthritis in Lumbar Spinal Stenosis

Study Design Cross-sectional study. Purpose To investigate the relationship between ligamentum flavum (LF) thickening and lumbar segmental instability and disc degeneration and facet joint osteoarthritis. Overview of Literature Posterior spinal structures, including LF thickness, play a major role in lumbar spinal canal stenosis pathogenesis. The cause of LF thickening is multifactorial and includes activity level, age, and mechanical stress. LF thickening pathogenesis is unknown. Methods We examined 419 patients who underwent computed tomography (CT) myelography and magnetic resonance imaging after complaints of clinical symptoms. To investigate LF hypertrophy, 57 patients whose lumbar vertebra had normal disc heights at L4–5 were selected to exclude LF buckling as a hypertrophy component. LF thickness, disc space widening angulation in flexion, segmental angulation, presence of a vacuum phenomenon, and lumbar lordosis at T12–S1 were investigated. Disc and facet degeneration were also evaluated. Facet joint orientation was measured via an axial CT scan. Results The mean LF thickness in all patients was 4.4±1.0 mm at L4–5. There was a significant correlation between LF thickness and disc degeneration; LF thickness significantly increased with severe disc degeneration and facet joint osteoarthritis. There was a tendency toward increased LF thickness in more sagittalized facet joints than in coronalized facet joints. Logistic regression analysis showed that LF thickening was influenced by segmental angulation and facet joint osteoarthritis. Patient age was associated with LF thickening. Conclusions LF hypertrophy development was associated with segmental instability and severe disc degeneration, severe facet joint osteoarthritis, and a sagittalized facet joint orientation.

Locally applied simvastatin promotes bone formation in a rat model of spinal fusion.

Simvastatin, an inexpensive lipid‐lowering drug widely used to prevent cardiovascular disorders, is known to increase osteoblastic activity, inhibit osteoclastic activity, and stimulate osteoblastic production of bone morphogenetic protein 2. Furthermore, local simvastatin application increased bone formation in animal models of fracture or bone defects. We investigated the effect of locally applied simvastatin in a rat model of spinal fusion. We performed posterolateral lumbar fusion surgery with iliac crest autograft in 36 rats divided into group I (n = 17; implanted with a gelatin scaffold) and group II (n = 19; implanted with a gelatin scaffold infused with 0.5 mg simvastatin). The rats were euthanized at 6 or 12 weeks postoperatively, and the spines were explanted and assessed. The fusion rates in group II (16.7%: 6 weeks, 30%: 12 weeks) were considerably higher than those in groups I (0%: 6 weeks, 0%: 12 weeks). The 6‐ and 12‐week radiographic scores were significantly higher in group II than in group I. High‐resolution micro‐computerized tomography revealed that the tissue and bone volumes of the callus tended to be higher in group II than in group I. Histologic analysis of the spines explanted after 12 weeks demonstrated new bone formation between the transverse processes in group II, but thicker and wider individual trabeculae with fibrotic tissue and muscle fiber between the transverse processes in group I. Locally applied simvastatin was efficacious in accelerating bone formation in our rat model of spinal fusion, supporting its potential clinical application as a promoter of bone morphogenesis in spinal fusion.

Surgical outcomes of laminoplasty for cervical spondylotic myelopathy in very elderly patients (older than 80 years): Time from symptom onset to surgery and changes in spinal cord signal intensity on MRI

OBJECTIVE We aimed to assess the surgical outcomes of laminoplasty for cervical spondylotic myelopathy (CSM) in very elderly patients (older than 80 years), focusing specifically on the time from symptom onset to surgery and on the loss in spinal cord signal intensity on magnetic resonance imaging (MRI). PATIENTS AND METHODS We retrospectively reviewed 100 consecutive patients (61 males and 39 females) with CSM who underwent laminoplasty between 2006 and 2014. The patients were stratified based on the age at the time of surgery, with Group A consisting of 26 patients aged 80 years or older and Group B consisting of 74 patients younger than 80 years. The severity of myelopathy was assessed in terms of the Japanese Orthopaedic Association (JOA) score. Signal intensity loss on MRI was graded from I to III based on the size of the area with intensity changes (Grade I, one disk; Grade II, larger than one disk) and presence of intramedullary hypointensity on T1-weighted sagittal scans (Grade III). Surgical outcome, morbidities, and changes in spinal cord signal intensity on MRI were analyzed. RESULTS The time from symptom onset to surgery was 6.2±5.2 and 16.5±18.8months in Groups A and B, respectively, with significantly shorter duration of symptoms in Group A (p<0.001). Compared to Group B, Group A had lower mean JOA score preoperatively (8.8±1.9 vs. 10.1±1.7) and postoperatively (12.1±1.7 vs. 13.5±1.6), as well as lower mean JOA score recovery rate (40.7±12.5% vs. 51.0±15.4%) (p<0.05 for all). However, there was no difference between the groups regarding achieved JOA score (Group A, 3.3±1.0; Group B, 3.4±1.0). Preoperatively, intramedullary signal intensity change was observed in 84.6% of patients in Group A (22/26; 3, 13, and 6 patients with Grade I, II, and III, respectively), and in (82.4%) of patients in Group B (61/74; 18, 38, and 5 patients with Grade I, II, and , respectively), with significantly higher incidence of Grade III pattern in Group A than in Group B. CONCLUSION Compared to younger patients, very elderly patients had a shorter time from symptom onset to surgery but lower preoperative JOA score, indicating that the condition of very elderly patients is likely to deteriorate and become severe rapidly after the onset of myelopathy. However, it is very important to know these pathologies and optimize the timing of surgery, as laminoplasty for CSM can be beneficial even in very elderly patients.

Relationship of T1 slope with loss of lordosis and surgical outcomes after laminoplasty for cervical ossification of the posterior longitudinal ligament

OBJECTIVE T1 slope (T1S) has emerged as a predictor of kyphotic alignment change after laminoplasty. Although it was reported that patients with cervical ossification of the posterior longitudinal ligament (OPLL) and higher T1S had more pronounced lordotic curvature before surgery and higher loss of cervical lordosis after surgery, few studies have attempted to correlate these findings with clinical outcomes. We aimed to investigate the relationship of T1S with loss of cervical lordosis and surgical outcomes after laminoplasty for cervical OPLL. PATIENTS AND METHODS 35 consecutive patients (26 men and 9 women) with cervical OPLL who underwent double-door laminoplasty were followed for more than 12 months. Radiological and clinical measurements were performed to analyze the following parameters: pre and postoperative C2-C7 Cobb lordotic angle (LA), preoperative C2-C7 range of motion (ROM), loss of cervical lordosis, percentage of change in postoperative kyphosis, pre and postoperative C2-C7 sagittal vertical axis (SVA), change in C2-C7 SVA and occupying ratio of the OPLL, Japanese Orthopedic Association (JOA) score recovery rate, preoperative MRI grade. RESULTS Patients were divided into 2 groups according to preoperative T1 slope, with the cutoff value being the average preoperative T1 slope. Preoperative C2-C7 Cobb LA (P=0.007) and loss of cervical lordosis (P=0.034) differed between the two groups. Preoperative C2-C7 Cobb LA (R=0.50, P=0.002) and loss of cervical lordosis (R=0.36, P=0.036) were significantly correlated to preoperative T1S. Multivariate linear regression analysis showed that the preoperative T1S was not related to JOA score recovery rate and the preoperative MRI grade (OR=-9.985, P=0.015) was only related to JOA score recovery rate. CONCLUSION Although the degree of alignment compromise is correlated with the preoperative T1S, clinical outcomes demonstrate overall improvement after cervical laminoplasty with cervical OPLL, regardless of preoperative T1S.

Enhancing the effects of exfoliated carbon nanofibers using bone morphogenetic protein in a rat spinal fusion model: Effects of Exfoliated Carbon Nanofibers in a Rat Spinal Fusion Model

Exfoliated carbon nanofibers (ExCNFs) are expected to serve as excellent scaffolds for promoting and guiding bone‐tissue regeneration. We aimed to enhance the effects of ExCNFs using bone morphogenetic proteins (BMPs) and examined their feasibility and safety in clinical applications using a rat spinal fusion model. Group I (n = 15) animals were implanted with the control carrier; Group II (n = 16) animals were implanted with carrier containing 1 μg ExCNFs; Group III (n = 16) animals were implanted with carrier containing 1 μg recombinant human (rh) BMP‐2; and Group IV (n = 17) animals were implanted with carrier containing 1 μg rhBMP‐2 and 1 μg ExCNFs. The rats were euthanized after 4 or 8 weeks and their spines were explanted and assessed by manual palpation, radiographs, and high‐resolution microcomputerized tomography (micro‐CT); the spines were also subjected to histological analysis. The fusion rates in Group IV (25.0%: 4‐week, 45.5%: 8‐week) were considerably higher than in Groups I (0%: 4‐week, 0%: 8‐week), II (0%: 4‐week, 15.0%: 8‐week), and III (16.7%: 4‐week, 30.0%: 8‐week). These results demonstrated the enhancement of ExCNF bone fusion effects by BMP in a rat spinal fusion model. Our results suggest that the enhancement of ExCNFs effects by BMP makes this combination a possible attractive therapy for spinal fusion surgeries.

Relationship between vertebral morphology and the potential risk of spinal cord injury by pedicle screw in adolescent idiopathic scoliosis

OBJECTIVE We aimed to investigate the relative preoperative position of the spinal cord in AIS and explore the potential risk of spinal cord injury from placement of pedicle screws. PATIENTS AND METHODS Twenty-seven patients with a mean age of 15 ± 1.8 years (range, 12-19 years) classified as having Lenke type 1 AIS (1A: 15 cases, 1B: 8 cases, 1C: 4 cases) were analyzed. The mean Cobb angle of the main curve was 55.9 ± 14.4°. Axial CT myelography images were selected from the T4 to T12 vertebrae, and 243 images were analyzed. Outer cortical pedicle width, inner cortical pedicle width, pedicle length, chord length, transverse pedicle angle, the angle of rotation (RAsag) of the vertebra, and the distance between the spinal cord and concave (Dc) and convex pedicles (Dv) were calculated from landmark locations. RESULTS The mean concave outer cortical pedicle width was larger than the mean convex outer cortical pedicle width at T4, T5, T11, and T12 (p < 0.05) and smaller than the mean convex outer cortical pedicle width around the apex of the curve from T7 to T9 (p < 0.05). The mean concave inner cortical pedicle width was larger than the mean convex inner cortical pedicle width at T4, T5, and T11 (p < 0.05) and smaller than the mean convex inner cortical pedicle width around the apex of the curve at T7 and T8 (p < 0.001). The mean Dc was smaller than the mean Dv around the apex of the curve from T6 to T11 (p < 0.05). Dv was significantly correlated with the convex outer cortical pedicle width (R = 0.286, p < 0.001), convex inner cortical pedicle width (R = 0.202, p = 0.002), convex transverse pedicle angle (R=-0.286, p < 0.001), and RAsag (R = 0.277, p < 0.001). Dc was significantly correlated with the concave outer (R = 0.269, p < 0.001) and inner cortical pedicle width (R = 0.230, p < 0.001). CONCLUSION The distance from the spinal cord to the medial wall of the pedicle was significantly correlated with outer and inner cortical pedicle width, and the potential risk of spinal cord injury by pedicle screw is increased with insertion into a narrower pedicle, especially on the concave side around the apex.

Relationship of preoperative intramedullary MRI signal intensity and dynamic factors with surgical outcomes of laminoplasty for cervical ossification of the posterior longitudinal ligament

OBJECTIVE We aimed to analyze the relationship of preoperative signal intensity on magnetic resonance imaging (MRI) and dynamic factor with surgical outcomes of laminoplasty for cervical ossification of the posterior longitudinal ligament (OPLL). PATIENTS AND METHODS We retrospectively reviewed the records of 29 patients (20 males and 9 females) who underwent double-door laminoplasty for cervical OPLL. T2-weighted MRI was performed preoperatively. To assess the high-signal changes of the spinal cord, signal intensity was classified as grade 0 (low signal, no changes), grade 1 (medium signal, mild changes), and grade 2 (bright signal, pronounced changes). The following factors were analyzed for their relationship with surgical outcome, expressed as the Japanese Orthopedic Association (JOA) score recovery rate: pre- and postoperative C2-C7 range of motion (ROM), segmental ROM, C2-C7 lordotic angle, and spinal cord occupying ratio, as well as disease duration. RESULTS Disease duration was significantly longer in patients with pronounced high-signal changes on preoperative MRI (P < 0.05 for grade 2 vs. grade 1 or 0). The mean preoperative JOA score and JOA score recovery rate were significantly lower in patients with pronounced high-signal changes on preoperative MRI (P < 0.05 for grade 2 vs. grade 1 or 0). Preoperatively, segmental ROM was significantly smaller in patients with no MRI signal intensity changes (P < 0.05 for grade 0 vs. grade 1 or 2). Additionally, preoperative segmental ROM was negatively correlated with JOA score recovery rate (R=-0.470, P = 0.01) and positively correlated with high-signal changes on preoperative MRI (R = 0.460, P = 0.012). On multivariate analysis, preoperative segmental ROM was negatively associated with JOA score recovery rate (odds ratio, - 0.407; P = 0.046). CONCLUSION Given its negative correlation with JOA score recovery rate and positive correlation with high-signal changes on preoperative MRI, higher preoperative segmental ROM may be associated with spinal cord damage due to repeated minor trauma, predicting poor surgical outcome of laminoplasty in cervical OPLL.

Spondylectomy and lateral lumbar interbody fusion for thoracolumbar kyphosis in an adult with achondroplasia: A case report

Rationale: Fixed thoracolumbar kyphosis with spinal stenosis in adult patients with achondroplasia presents a challenging issue. We describe the first case in which spondylectomy and minimally invasive lateral access interbody arthrodesis were used for the treatment of fixed severe thoracolumbar kyphosis and lumbar spinal canal stenosis in an adult with achondroplasia. Patient concerns: A 61-year-old man with a history of achondroplastic dwarfism presented with low back pain and radiculopathy and neurogenic claudication. Diagnoses: Plain radiographs revealed a high-grade thoracolumbar kyphotic deformity with diffuse degenerative changes in the lumbar spine. The apex was located at L2, the local kyphotic angle from L1 to L3 was 105°, and the anterior area was fused from the L1 to L3 vertebrae. MRI revealed significant canal and lateral recess stenosis secondary to facet hypertrophy. Interventions: We planned a front-back correction of the anterior and posterior spinal elements. We first performed anterior release at the fused part from L1 to L3 and XLIF at L3/4 and L4/5. Next, the patient was placed in the prone position. Spondylectomy at the L2 vertebra and posterior fusion from T10 to L5 were performed. Postoperative radiographs revealed L1 to L3 kyphosis of 32°. Outcomes: No complications occurred during or after surgery. Postoperatively, the patients low back pain and neurological claudication were resolved. No worsening of kyphosis was observed 24 months postoperatively. Lessons: Circumferential decompression of the spinal cord at the apical vertebral level and decompression of lumbar canal stenosis were necessary. Front-back correction of the anterior and posterior spinal elements via spondylectomy and lateral lumbar interbody fusion is a reasonable surgical option for thoracolumbar kyphosis and developmental canal stenosis in patients with achondroplasia.

Dynamic paraspinal muscle impingement causing acute hemiplegia after C1 posterior arch laminectomy: A case report

Rationale: Acute neurological deficits following spinal surgery commonly result from epidural hematoma, surgical trauma, vascular compromise, and graft or hardware impingement, with the cause identified by magnetic resonance imaging (MRI). We present a rare case of dynamic paraspinal muscle impingement after C1 posterior arch laminectomy, which was diagnosed by myelography, with no significant findings on MRI. Patient concerns: An 81-year-old, severely obese male, was referred to our department for the treatment of vertebral disease of the lumbar spine. The patient presented with bilateral weakness and numbness of the upper extremities and gait disturbances. Based on MRI, a diagnosis of retro-odontoid pseudotumor was made, and C1 posterior arch laminectomy, in combination with C4 partial laminectomy and C5 to C6 laminoplasty, was performed. On postoperative day 3, the patients neurological status deteriorated, with right upper extremity and right lower extremity weakness increasing with neck extension. Although there was no evidence of epidural hematoma formation on MRI, obstruction of the flow of contrast medium by an external posterior compression in neck extension at the level of C1 was identified by myelography. Revision surgery was performed and local muscle swelling at the surgical site identified with no hematoma formation. Occiput to C3 fixation, with instrumentation, was performed. Outcomes: Muscle strength of the right upper extremity and lower extremities recovered postsurgery, and the patient has continued to improve function 3 years after surgery, with no further neurological episodes. Lessons: Dynamic paraspinal muscle impingement following C1 laminectomy in a muscular man was diagnosed by myelography, with no significant findings on standard MRI. Conclusion: The possibility of dynamic paraspinal muscle impingement should be considered in patients developing acute, progressive, neurological deficits after posterior cervical decompression, with myelography being the imaging method of choice for diagnosis.

Surgical outcomes after laminoplasty for cervical spondylotic myelopathy: A focus on the dynamic factors and signal intensity changes in the intramedullary spinal cord on MRI

OBJECTIVE We aimed to analyze the relationship between the dynamic factors and signal intensity changes in the intramedullary spinal cord on MRI, and surgical outcomes, following double-door laminoplasty for cervical spondylotic myelopathy (CSM). PATIENTS AND METHODS This retrospective study included 100 consecutive patients who underwent double-door laminoplasty for CSM. The following factors were analyzed: JOA score recovery rate, age, duration from onset to surgery, intraoperative bleeding, signal intensity changes in the intramedullary spinal cord on MRI, pre and postoperative C2-7 lordotic angle (LA), changes in C2-7 LA, pre and postoperative C2-7 range of motion (ROM), and pre and postoperative segmental ROM. The Charlson Comorbidity Index (CCI) was also used for the assessment of complications. RESULTS Age, CCI, preoperative segmental ROM, and pre and postoperative MRI grade significantly correlated with JOA score recovery rate (P<0.01), whereas number of expanded laminae, duration from onset to surgery, surgery time, intraoperative bleeding, preoperative and postoperative C2-7 LA, change in C2-7 LA, and preoperative C2-7 ROM did not. Multivariate analysis showed that the preoperative segmental ROM (OR=-0.988, P=0.017) and preoperative MRI grade (OR=-7.170, P=0.042) were significantly associated with JOA score recovery rate. CONCLUSION Considering the dynamic factors, there was no correlation with C2-7 ROM and surgical outcome, but preoperative segmental ROM and a change in signal intensity of the intramedullary spinal cord on MRI were negatively correlated with surgical outcome. From these results, we suggest that preoperative segmental ROM is possibly associated with spinal cord damage due to repeated minor trauma and affects surgical outcome of laminoplasty.