Dynamic Cervical Spinal Canal Stenosis: Identifying Imaging Risk Factors in Extended Positions.

STUDY DESIGN: A retrospective study at a single academic institution. PURPOSE: This study aimed to identify imaging risk factors for stenosis in extended neck positions undetectable in preoperative neutral magnetic resonance imaging (MRI) and improving decompression strategies for cervical spine disorders. OVERVIEW OF LITERATURE: Cervical disorders are influenced by various dynamic factors, with spinal stenosis appearing during neck extension. Despite the diagnostic value of dynamic cervical MRI, standard practice often uses neutral-position MRI, potentially influencing surgical outcomes. METHODS: This study analyzed 143 patients who underwent decompression surgery between 2012 and 2014, who had symptomatic cervical disorders and MRI evidence of spinal cord or nerve compression but had no history of cervical spine surgery. Patient demographics, disease type, Japanese Orthopedic Association score, and follow-up periods were recorded. Spinal surgeons conducted radiological evaluations to determine stenosis levels using computed tomography myelography or MRI in neutral and extended positions. Measurements such as dural tube and spinal cord diameters, cervical alignment, range of motion, and various angles and distances were also analyzed. The residual space available for the spinal cord (SAC) was also calculated. RESULTS: During extension, new stenosis frequently appeared caudal to the stenosis site in a neutral position, particularly at C5/C6 and C6/C7. A low SAC was identified as a significant risk factor for the development of new stenosis in both the upper and lower adjacent disc levels. Each 1-mm decrease in SAC resulted in an 8.9- and 2.7-fold increased risk of new stenosis development in the upper and lower adjacent disc levels, respectively. A practical SAC cutoff of 1.0 mm was established as the threshold for new stenosis development. CONCLUSIONS: The study identified SAC narrowing as the primary risk factor for new stenosis, with a clinically relevant cutoff of 1 mm. This study highlights the importance of local factors in stenosis development, advocating for further research to improve outcomes in patient with cervical spine disorders.

Disc Height Narrowing Could Not Stabilize the Mobility at the Level of Cervical Spondylolisthesis: A Retrospective Study of 83 Patients with Cervical Single-Level Spondylolisthesis.

STUDY DESIGN: A retrospective study at a single academic institution. PURPOSE: We aimed to understand the pathogenesis of cervical spondylolisthesis by analyzing whether narrowing of the disc height stabilizes the slipped disc level according to the degenerative cascade. OVERVIEW OF LITERATURE: According to Kirkaldy-Willis' degenerative cascade, the narrowing of the disc height at slipped level contributes to intervertebral stability in lumbar spondylolisthesis. Conversely, the pathogenesis of cervical spondylolisthesis is unknown due to a scarcity of reports on the condition. METHODS: The images of 83 patients with cervical single-level spondylolisthesis were studied. We looked at 52 slipped levels for anterior slippage and 31 for posterior slippage. The imaging parameters included slippage in the neutral, flexed, and extended positions, axial facet joint orientation, sagittal facet slope, global cervical alignment, C2-C7 angle, C2-C7 sagittal vertical axis, range of motion (ROM), and slipped disc angle ROM. RESULTS: With the narrowing of the intervertebral disc height, slippage in the flexed position of both anterior and posterior spondylolisthesis increased. However, in both anterior and posterior spondylolisthesis, disc height narrowing did not show stability. The narrowing of the intervertebral disc height was found to be a risk factor for a translation of slippage of 1.8 mm or more in flexionextension motion in anterior spondylolisthesis in multivariate regression analysis. CONCLUSIONS: Narrowing the intervertebral disc height did not stabilize the translation of slippage in flexion-extension motion in cervical spondylolisthesis. Instead, narrowing of the disc height was associated with a translation of slippage of 1.8 mm or more in flexion-extension motion in cases of anterior slippage. Therefore, we discovered that degenerative cascade stabilization for cervical spondylolisthesis was difficult to achieve.

Surgical Outcomes of Selective Laminectomy for Patients With Cervical Kyphosis: A Retrospective Study of 379 Cases.

STUDY DESIGN: A retrospective study. OBJECTIVES: This study aimed to investigate the impact of cervical kyphosis on patients with cervical spondylotic myelopathy (CSM) following selective laminectomy (SL) regarding posterior spinal cord shift (PSS), and a number of SLs. METHODS: We evaluated 379 patients with CSM after SL. The patients with kyphosis (group K) were compared with those without kyphosis (group L). Moreover, groups K and L were divided into subgroups KS and KL (SLs ≤ 2) and LS and LL (SLs ≥ 3), respectively, and analyzed. Receiver operating characteristic (ROC) curve analysis was performed to determine the cut-off value of the C2-C7 angle for satisfactory surgical outcomes, which was defined as a Japanese Orthopaedic Association (JOA) recovery rate of ≥50% in group KS. RESULTS: The average PSS (mm) in group K was smaller than that in group L (.8 vs 1.4; P < .01), but the JOA recovery rate was comparable between the 2 groups. Meanwhile, the mean PSS and JOA recovery rate (%) in group KS was lower than those in group KL, respectively (.3 vs 1.0; P < .01, 35.1 vs 52.3; P = .047). Moreover, the average PSS of group KS (.6) was smaller than those of other subgroups ( < .01). In addition, the ROC curve analysis showed that the C2-C7 angle of -14.5° could predict satisfactory surgical outcomes in group KS. CONCLUSION: Selective laminectomy is not contraindicated for patients with kyphosis, but a larger number of SLs may be indicated for the patients with C2-C7 angles of ≤ -14.5°.

Assessment of the Necessity of Osteoporosis Treatment for Patients with Low Bone Density in Diffuse Idiopathic Skeletal Hyperostosis.

Introduction: Although patients with diffuse idiopathic skeletal hyperostosis (DISH) do not have low bone density, it is a risk factor for spine fractures associated with DISH. We investigated the characteristics and bone metabolism markers of patients with DISH having low bone density to assess whether osteoporosis medication is necessary to prevent fractures. Methods: A cross-sectional study was conducted between April 1, 2008, and March 31, 2019. The 86 patients included were divided into two groups according to their T-scores-one group had low bone density and DISH, and the other group did not. Group A (T-score≤-1) and B (T-score>-1) data were adjusted for confounding factors and compared for differences in age, body weight, maximum number of vertebral bodies with bony bridges between adjacent vertebrae (max VB), and previous history (hypertension, malignant tumors, diabetes mellitus, cardiac diseases, chronic renal failure, and spinal fractures). In Group A, multiple linear regression was used to investigate relationships among max VB, femur bone mineral density (BMD), total type I procollagen N-terminal propeptide (P1NP), and tartrate-resistant acid phosphatase 5b (TRACP-5b). Results: Group A had 36, and Group B had 50 male patients with DISH. Patients in Group B were heavier than those in Group A. The mean femur BMD in Group A was age-appropriate, and that in Group B was higher than the age-appropriate femur BMD. The mean values of P1NP and TRACP-5b were within the normal range. Max VB was positively correlated with total P1NP in Group A. Total P1NP was significantly and positively correlated with TRACP-5b. Conclusions: The DISH group with a T-score of ≤-1 was age-appropriate. The group with a T-score of >-1 had higher BMD because of their higher body weight. The group with a T-score of ≤-1 had good bone metabolism and did not require aggressive osteoporosis treatment.

Cervical Spinous Process and Its Attached Muscles Maintain Lower Disk Lordosis: A Retrospective Study of 155 Patients Who Underwent Muscle-Preserving Double Laminectomies.

STUDY DESIGN: A retrospective study conducted at a single academic institution. PURPOSE: This study compared the postoperative alignment of consecutive double laminectomies according to their decompression levels and investigated the influence of the extension unit of the spinous process and its attached muscles on postoperative alignment. OVERVIEW OF LITERATURE: Many reports have investigated bony and soft tissue factors as the causes of postoperative cervical alignment disorders. To-this-date, no other article has clarified the importance of the attached muscles between the spinous processes of C3 and C6 to maintain local cervical alignment. METHODS: In total, 155 consecutive patients who underwent muscle-preserving consecutive double laminectomies for cervical spondylotic myelopathy from 2005 to 2013 were included in this study. The imaging parameters included the C2-C7 angle, range of motion, C2-C7 sagittal vertical axis (SVA), C7 slope, C2-C5 angle, C5-C7 angle, local disk angle caudal to the decompression level, and the disk height between C2/C3 and C7/Th1. RESULTS: The caudal disk angle of the decompression level decreased after consecutive double laminectomies, thus suggesting that the extension unit maintained the local lordosis at the lower disk of the decompression level. Postoperatively, in the C3-4 decompression cases, the C2-C7 angle decreased by 7.3°, and the C2-C7 SVA increased by 8.6 mm, thus indicating the appearance of an alignment disorder. Multivariate logistic regression analysis showed that cephalad laminectomy was a risk factor for C2-C7 angle decreases >10°. However, the postoperative recovery rate of Japanese Orthopedic Association scores after consecutive double laminectomies was reasonable, and the overall cervical alignment was well maintained in all decompression levels except C3-C4. CONCLUSIONS: The cervical extension unit maintained lordosis at the disk caudal to it. The extension unit was found to contribute more to the maintenance of lordosis of the entire cervical spine at the cephalad side.

Atlantoaxial stenosis after muscle-preserving selective laminectomy.

There are few reports of degenerative atlantoaxial stenosis and new stenosis after cervical decompression. We experienced four cases of atlantoaxial stenosis after muscle-preserving selective laminectomy. We compared these four cases with no stenosis cases after long-term follow-up of selective laminectomy, as well as healthy subjects. A total of 1205 patients who underwent muscle-preserving selective laminectomy due to cervical disorders were included in this study. Postoperative atlantoaxial stenosis, which needed decompression, appeared in 4 cases, and 30 patients did not have radiological stenosis for more than 10 years after surgery. Twenty healthy volunteers were also used as controls. The radiographic parameters measured were C2-C7 angle, C2-C7 sagittal vertical axis (SVA), C2 slope, C7 slope, C2-C5 angle, C5-C7 angle, C1-C2 angle, and atlantodental interval (ADI). We measured the anterior-posterior (AP) diameters of the spinal cord (SC) and dural tube (Dura) at C1/C2 with sagittal MRI. In the cases of atlantoaxial stenosis, the AP of SC and Dura at C1/C2 were smaller preoperatively, and the residual space for SC (SAC) was also smaller. The preoperative ADI was significantly higher in patients with atlantoaxial stenosis, suggesting preoperative instability at C1/C2. Analysis of the ROC curve showed that patients with a preoperative SAC of less than 3.6 mm and an ADI of more than 1.35 mm were more likely to develop postoperative atlantoaxial stenosis. When we perform a muscle-preserving selective laminectomy, decompression of C1/C2 is suggested when the SAC at C1/C2 is less than 3.6 mm and the ADI is more than 1.35 mm.

Adjacent Segment Stenosis after Muscle-Preserving Selective Laminectomy: A Retrospective Study of Patients with a Minimum 10-Year Follow-Up.

Introduction: The present study aimed to understand the characteristics of adjacent segment stenosis post-surgery by examining the status of adjacent segment stenosis in patients with long-term follow-up after muscle-preserving selective laminectomy (SL). Methods: We examined 43 patients who underwent muscle-preserving SL at a single academic institution and were followed up for >10 years. The C2-C7 angle, C2-C7 sagittal vertical axis, range of motion, and C7 slope were measured using an X-ray lateral view. The anterior-posterior diameter of the spinal cord (AP of SC) and anterior-posterior diameter of the dural tube (AP of dura) at adjacent segment were measured using magnetic resonance imaging T2-weighted sagittal section. Residual space for the spinal cord at the adjacent segment (SAC) was calculated as the difference between AP of SC and AP of dura. Results: Four cases had cephalad adjacent segment stenosis at the last follow-up (upper stenosis (US) group), 9 cases had caudal adjacent segment stenosis ( lower stenosis (LS) group), and 30 cases had no stenosis (none (N) group). AP of SC, AP of dura, and SAC at the upper adjacent segment were significantly lower in the US group. AP of dura and SAC at the lower adjacent segment were significantly lower in the LS group. Multivariate logistic regression analysis revealed that the small AP of dura in the upper adjacent segment and small SAC in the lower adjacent segment were risk factors for developing a new stenosis. Conclusions: Decompression should be considered beforehand in adjacent segments with small AP of SC and small AP of dura when performing cervical decompression.

Association of Continuous Vertebral Bone Bridges and Bone Mineral Density with the Fracture Risk in Patients with Diffuse Idiopathic Skeletal Hyperostosis.

STUDY DESIGN: Cross-sectional study. PURPOSE: To examine whether the number of continuous vertebral bone bridges and bone mineral density (BMD) influence the fracture risk in diffuse idiopathic skeletal hyperostosis (DISH) patients. OVERVIEW OF LITERATURE: Bone bridges connecting through the intervertebral body in DISH create long lever arms that can increase the risk of fractures from minor trauma. DISH patients have a BMD that is higher than or comparable to those of age-matched healthy subjects. METHODS: We examined the computed tomography scans from the thoracic vertebra to the sacrum used to diagnose DISH in 140 patients (98 men and 42 women; average age, 78.6 years). We compared patients who did (n=52) and did not have (n=88) fractures at the continuous vertebral bodies fused by bone bridges. The relationship between the vertebral fractures and the maximum number of vertebrae that are bony cross-linked with contiguous adjacent vertebrae (max VB) from the thoracic vertebra to the sacrum or from the lumbar vertebra to the sacrum and proximal femur BMD were analyzed using a logistic regression model. RESULTS: We found that after adjusting for the confounding factors, higher max VB, both from the thoracic vertebrae to the sacrum and the lumbar vertebrae to the sacrum, was associated with a higher risk of vertebral fractures. This difference was statistically significant. The risk was higher when only the lumbar vertebrae to the sacrum was considered (thoracic vertebrae to the sacrum: odds ratio, 1.21; p<0.05; lumbar vertebrae to the sacrum: odds ratio, 2.78; p<0.01). Moreover, low proximal femur BMD in DISH patients raises the fracture risk (odds ratio, 0.47; p<0.01). CONCLUSIONS: Many continuous vertebral bone bridges, especially those that extend to the lumbar spine and low proximal femur BMD, are risk factors for fracture in DISH patients.

Clinical Effects of Anterior Cervical Spondylolisthesis on Cervical Spondylotic Myelopathy After Posterior Decompression Surgery: A Retrospective Multicenter Study of 732 Cases.

STUDY DESIGN: Multicenter retrospective study. OBJECTIVES: We aim to investigate features of cervical spondylotic myelopathy (CSM) associated with anterior cervical spondylolisthesis (ACS) during posterior decompression surgery. METHODS: A total of 732 patients with CSM were enrolled, who underwent posterior decompression surgery between July 2011 and November 2015 at 17 institutions. The patients with ACS (group A), defined as an anterior slippage of ≥2 mm on plain radiographs, were compared with those without ACS (group non-A). Also, the characteristics of patients with ACS progression (group P), defined as postoperative worsening of ACS ≥2 mm or newly developed ACS, were investigated. Moreover, kyphosis was defined as C2-C7 angle in neutral position ≤-5°. The Japanese Orthopedic Association (JOA) scoring system was used for clinical evaluation. RESULTS: Group A consisting of 62 patients (8.5%) had worse preoperative clinical status but comparable surgical outcomes to group non-A. Furthermore, ACS was associated with greater age, and the degree of slippage did not affect myelopathy grades. Seventeen patients (2.3%) were observed in group P, and preoperative ACS was a significant predisposing factor for the progression without clinical impact. Among the patients in group A, preoperative cervical kyphosis was a risk factor for lower JOA recovery rate. CONCLUSIONS: Although the presence of ACS increases the risk of postoperative progression, it is not a contraindication for posterior decompression. However, surgeons need to consider the indication of fusion surgery for the patients who have ACS accompanied by kyphosis because of the poor surgical outcomes.

Maximum number of bone cross-linked vertebrae: an index for BMD in diffuse idiopathic skeletal hyperostosis.

INTRODUCTION: The maximum number of vertebral bodies with bony bridges between adjacent vertebrae (max VB) helps assess the risk of fracture in diffuse idiopathic skeletal hyperostosis (DISH). In addition to max VB, the maximum thickness of bone cross-bridges (max TB) may be an index of bone mineral density (BMD). Therefore, this study investigated the relationship among max VB, max TB, and BMD. MATERIALS AND METHODS: The participants in this cross-sectional study were male patients (n = 123) with various max VB from the thoracic vertebrae to the sacrum without sacroiliac ankylosis. The participants were grouped by max VB. For example, a group with max VB from 4 to 8 would be listed as max VB (4-8). The relation between femur proximal BMD and mean max TB and max VB was assessed. Femur proximal BMD was then compared after adjusting for confounding factors. RESULTS: The results indicated that max VB was correlated with femur proximal BMD in max VB (0-8) and max VB (9-18) groups. The mean max TB was correlated only with femur proximal BMD in max VB (0-8). After adjusting, max VB (4-8) showed a significantly higher femur proximal BMD than max VB (0-3) and max VB (9-18). CONCLUSION: Femur proximal BMD and mean max TB showed different trends after max VB = 9, which suggests that max VB is an index of BMD, and that DISH has at least two possible populations in terms of BMD and bone cross-link thickness.

Baseline severity of myelopathy predicts neurological outcomes after posterior decompression surgery for cervical spondylotic myelopathy: a retrospective study.

STUDY DESIGN: Retrospective multicenter study. OBJECTIVES: To identify the usefulness of the baseline severity of myelopathy for predicting surgical outcomes for cervical spondylotic myelopathy (CSM). SETTING: Seventeen institutions in Japan. METHODS: This study included 675 persons with CSM who underwent posterior decompression. According to baseline severity, the individuals were divided into the mild (Japanese Orthopaedic Association [JOA] score ≥ 14.5), moderate (JOA score = 10.5-14), and severe (JOA score ≤ 10) groups. Surgical outcomes and clinical variables were compared between the groups. Logistic regression analysis was used to develop a prediction model for unsatisfactory symptom state (postoperative JOA score ≤ 14, residual moderate or severe myelopathy). RESULTS: The mean (±standard deviation) age was 67 ± 12 years. The participants in the severe group were older than those in the mild group. Postoperative JOA scores were higher in the mild group than in the severe group. According to multivariate logistic regression analysis, the prediction model included preoperative JOA scores (odds ratio [OR] 0.60; 95% confidence interval [CI] 0.55-0.67) and age (OR 1.06, 95% CI 1.04-1.08). On the basis of the model, a representative combination of the thresholds to maximize the value of "sensitivity - (1 - specificity)" demonstrated a preoperative JOA score of 11.5 as a predictor of postoperative unsatisfactory symptom state in people around the mean age of the study cohort (67 years). CONCLUSIONS: The combination of the baseline severity of myelopathy and age can predict postoperative symptom states after posterior decompression surgery for CSM.

Does K-line (-) in the Neck-flexed Position Predict Surgical Outcome of Cervical Spondylotic Myelopathy?: Results of a Multivariate Analysis After Muscle-preserving Selective Laminectomy.

STUDY DESIGN: A retrospective single-center study. OBJECTIVE: The aim of this study was to investigate the influence of the K-line in the neck-flexed position (flexion K-line) on the surgical outcome after muscle-preserving selective laminectomy (SL) for cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: Development of CSM is associated with dynamic factors and cervical alignment. The flexion K-line, which reflects both dynamic and alignment factors, provides an indicator of surgical outcome after posterior decompression surgery for patients with ossification of the posterior longitudinal ligament. However, the value of the flexion K-line for patients with CSM has not been evaluated. METHODS: Our study group included 159 patients treated with SL for CSM. Patients were divided into a flexion K-line (+) group and a flexion K-line (-) group. The influence of the flexion K-line on radiological and surgical outcomes was analyzed, with multivariate analysis conducted to identify factors affecting the surgical outcome. RESULTS: Patients in the flexion K-line (-) group were younger (P = 0.003), had a less lordotic cervical alignment (pre-and postoperatively, P < 0.001), a smaller C7 slope (pre-and postoperatively, P < 0.001), and a greater mismatch between the C7 slope and the C2-C7 angle (preoperatively, P = 0.047; postoperatively, P = 0.001). The postoperative increase in Japanese Orthopedic Association (JOA) score and the JOA score recovery rate (RR) were lower for the flexion K-line (-) than for the K-line (+) group (P < 0.001 and P < 0.001, respectively). On multivariate regression analysis, the flexion K-line (-) (ß = -0.282, P < 0.001), high signal intensity (SI) changes on T2-weighted image (WI) combined with low SI changes on T1-WI in the spinal cord (ß = -0.266, P < 0.001), and older age (ß= -0.248, P = 0.001) were predictive of a lower JOA score RR. CONCLUSION: The flexion K-line may be a useful predictor of surgical outcomes after SL in patients with CSM. LEVEL OF EVIDENCE: 4.

Analysis of the impact of spinopelvic radiographic parameters on the severity of cervical spondylotic myelopathy.

BACKGROUND: The correlation between spinal radiographic parameters and severity of cervical spondylotic myelopathy (CSM) is controversial. This study aimed to investigate the associations between spinal radiographic parameters and CSM severity, as well as between cervical and other spinopelvic radiographic parameters. METHODS: Patients diagnosed with CSM (N = 118; 77 men) at our hospital from March 2013 to February 2017 were included. The patients' demographic data and the following radiographic parameters were investigated: cervical lordosis (CL), C2-C7 sagittal vertical axis (C2-C7 SVA), T1 slope, thoracic kyphosis, lumbar lordosis, pelvic incidence, sacral slope, pelvic tilt, and sagittal vertical axis (SVA). Cervical cord compression ratio (CCCR) was evaluated on sagittal magnetic resonance imaging. The Japanese Orthopaedic Association (JOA) scoring system was used for clinical evaluation. Correlation analyses were performed among the clinical and radiographic parameters. RESULTS: The JOA score had the strongest correlation with SVA (r = -0.46, p < 0.01), followed by CCCR (r = -0.33, p < 0.01), CL (r = -0.29, p < 0.01), T1 slope (r = -0.29, p = 0.01), and C2-C7 SVA (r = -0.20, p = 0.03). Multivariate linear regression analysis revealed a model predicting the JOA score; JOA = 13.6 - 0.24 × SVA - 4.2 × CCCR (r = 0.51, p < 0.01). Although there was no significant correlation between the cervical and lumbopelvic radiographic parameters, the sequential correlation among the investigated spinopelvic parameters was identified. CONCLUSIONS: CSM severity worsened with spinal malalignment, such as a larger SVA. Though lumbopelvic radiographic parameters did not significantly impact cervical alignment and CSM severity, the sequential correlations among cervical-thoracic-lumbopelvic radiographic parameters were observed. Therefore, SVA is the most relevant radiographic parameter for CSM, but we cannot preclude the possibility that lumbopelvic alignment also affects cervical alignment and CSM severity.

K-line (-) in the neck-flexed position affects surgical outcomes in patients with ossification of the posterior longitudinal ligament after muscle-preserving selective laminectomy.

BACKGROUND: Posterior cervical decompression results in favorable outcomes for K-line (+) ossification of the posterior longitudinal ligament (OPLL) patients. However, even for patients with K-line (+) in the neck neutral position, K-line (-) in the neck-flexed position (flexion K-line (-)) may affect surgical outcomes. We investigated the influence of flexion K-line (-) on surgical outcomes after muscle-preserving selective laminectomy using multivariate analysis. METHODS: This study involved 113 OPLL patients with K-line (+) in the neck neutral position who underwent muscle-preserving selective laminectomy. Patients were divided into flexion K-line (+) (n = 90) and flexion K-line (-) (n = 23) groups. We analyzed the influence of a flexion K-line (-) on radiological and surgical outcomes. We conducted a multivariate analysis to analyze the factors affecting surgical outcomes. RESULTS: The patients with a flexion K-line (-) had a larger C2-C7 sagittal vertical axis (preoperatively, P = 0.042; postoperatively, P = 0.021), narrower postoperative clearance of the spinal cord (P = 0.003), a smaller proportion of segmental-type OPLL (P < 0.001), and a greater OPLL occupancy ratio (P < 0.001). The recovery rate measured by the Japanese Orthopedic Association (JOA) score was poorer in patients with a flexion K-line (-) (17.6 ± 32.2%) than in those with a flexion K-line (+) (35.3 ± 29.5%) (P = 0.013). Multiple linear regression analysis revealed that the flexion K-line (-) affected the recovery rate of the JOA score (ß = -0.233, P = 0.013). CONCLUSIONS: Even for patients with K-line (+) OPLL, the flexion K-line (-) affects surgical outcomes. The flexion K-line (-) is a useful predictor of poor surgical outcomes after posterior decompression surgery.

Ossified Posterior Longitudinal Ligament Existing at an Intervertebral Level Limits Compensatory Mechanism of Cervical Lordosis after Muscle-Preserving Selective Laminectomy.

INTRODUCTION: As C7 slope increases, lordotic change of C2-C7 angle compensates for adjustments in cervical sagittal balance. However, ossification of the posterior longitudinal ligament (OPLL) may affect the compensatory mechanism of the cervical spine. This study aims to evaluate the impact of OPLL on cervical lordotic compensation after muscle-preserving selective laminectomy (SL). METHODS: This study involved 235 patients with cervical spondylotic myelopathy (CSM) and OPLL who underwent ≥ 3 consecutive levels of SL. OPLL was classified into continuous, segmental, mixed, or localized type on the basis of the criteria previously reported. In this study, based on the motion preservation at the intervertebral level, patients were divided into CSM (n = 114), OPLL segmental type (OPLL-S; n = 44), and other types of OPLL (OPLL-O; i.e., continuous, mixed, and localized; n = 77). The cervical sagittal alignment, degree of spinal cord decompression, and surgical outcomes were compared among the three groups. RESULTS: The OPLL-O group had a larger postoperative C7 slope (p = 0.020), larger pre- (p = 0.021) and postoperative (p = 0.001) C2-C7 sagittal vertical axis, and greater pre- (p = 0.034) and postoperative (p = 0.002) C7 slope minus C2-C7 angle. Narrower postoperative spinal cord clearance (PSCC) from OPLL (p < 0.001) and more residual spinal cord compression (p < 0.001) were observed in the OPLL-O group. Correlation between postoperative C7 slope minus C2-C7 angle and PSCC was detected (r = -0.238, p < 0.001). The recovery rate of the Japanese Orthopedic Association score was slightly lower in the OPLL-O group (p < 0.001), and it was correlated with postoperative residual spinal cord compression (r = -0.305, p < 0.001). CONCLUSIONS: OPLL-O limits cervical lordotic compensation, resulting in cervical sagittal balance mismatch. It affects the degree of spinal cord decompression, which might be related to surgical outcome.

The Dural Tube Continues to Expand after Muscle-Preserving Cervical Laminectomy.

INTRODUCTION: The purpose of this study was to elucidate the duration for which the dural tube continues to expand after muscle-preserving cervical laminectomy and the extent to which the expansion affects surgical outcomes. METHODS: We analyzed 83 patients with cervical myelopathy who underwent muscle-preserving selective laminectomy of three consecutive laminae between C4 and C6. On the lateral radiographs, parameters considered were C2-7 Cobb angles, range of flexion-extension neck motions, and C2-7 sagittal vertical axis. Neck alignment was classified into four types with lateral radiographs. Anteroposterior (AP) diameter of the dural tube was measured at mid-level of the C5 vertebral body on T2 sagittal image. Expansion ratio (ER) was defined as the extent of expansion at a particular time divided by the final extent of expansion of the dural tube diameter. Operative outcomes were examined using the Japanese Orthopaedic Association scores. RESULTS: The mean age was 62.3 years, and the mean follow-up period was 2 years and 9 months. AP diameter of the dural tube had been expanding until 1-year after surgery. ER in cases with kyphosis was lower at 6 months than that in cases without kyphosis, indicating that the speed of dural expansion was slower in cases with kyphosis. There was no correlation between the extent of expansion of the dural tube and neurological recovery. CONCLUSIONS: The dural tube continued to expand for approximately 1-year after surgery. The dural tube of patients with kyphosis slowly expanded possibly because of the hardness of the dura mater. A small extent of dural expansion does not necessarily indicate bad surgical outcomes.

Upper cervical lordosis compensates lower cervical kyphosis to maintain whole cervical lordosis after selective laminectomy.

After lower-cervical-level spinal-cord tumor resection, compensatory upper cervical lordosis with lower cervical kyphosis was observed. However, no studies examined this compensation following posterior decompression surgery for cervical compressive myelopathy (CCM). The purpose of this study was to evaluate the compensatory mechanism after muscle-preserving selective laminectomy (SL) and to assess the clinical outcomes following such compensation. Enrolled in the study were 125 CCM patients who underwent C6 single-level SL, C5-C6 two-level SL, C4-C6 three-level SL, and C3-C6 four-level SL. Cervical spine lateral radiography was taken before surgery and during the final followup. The C2-C5, C5-C7, and C2-C7 angles were measured and presented respectively as the patients' "upper," "lower," and "whole" cervical alignments. Patients were divided into two groups according to their postoperative C5-C7 alignment changes. We then divided the C5-C7 kyphotic-change group according to the patients' postoperative C7 slope changes. Postoperative cervical sagittal balance and surgical outcomes were compared within the groups. Postoperative C5-C7 kyphotic change was compensated for by C2-C5 lordotic change, maintaining the preoperative C2-C7 angle. Although postoperative C5-C7 kyphotic change alone did not affect cervical sagittal balance or surgical outcomes, patients with C5-C7 kyphotic changes and C7 slope increases showed greater increases in the C2-C7 sagittal vertical axis and lower recovery rates in Japanese Orthopaedic Association scores. The patients' postoperative lower cervical kyphotic changes were compensated for by upper cervical lordotic changes. Despite this compensation, increases in patients' C7 slopes adversely affected sagittal balance and functional recovery.

Extremely high preoperative C7 slope limits compensatory cervical lordosis after muscle-preserving selective laminectomy.

PURPOSE: A high C7 slope induces C2-C7 lordosis to compensate for cervical sagittal balance adjustments. A muscle-preserving selective laminectomy (SL) can maintain this compensation postoperatively. This study evaluated the effect of an extremely high C7 slope on C2-C7 lordotic compensation following SL. METHODS: This study enrolled 151 cervical compressive myelopathy patients who underwent SL. Lateral cervical spine radiographs were taken before surgery and during final follow-up. Patients were divided into extremely high C7 slope (≥ 30°) (EH) and non-high C7 slope (< 30°) (NH) groups and the influence of a high C7 slope on radiological and surgical outcomes was examined. RESULTS: Mean age was higher in group EH (p < 0.001). Preoperatively, patients in group EH had a larger C2-C7 sagittal vertical axis (SVA) (p = 0.001) and greater cervical lordosis (p < 0.001). Although C2-C7 SVA increased after surgery, mean C2-C7 angle of group EH decreased. Mismatches between C7 slope and C2-C7 angle increased for group EH postoperatively (p = 0.015). Postoperative Japanese Orthopedic Association (JOA) score and recovery rate (RR) were slightly lower in group EH (p = 0.001 and p = 0.006, respectively). Multiple linear regression analyses revealed that extremely high C7 slope, not age, affected the RR of JOA score (p = 0.006). CONCLUSIONS: Patients in group EH were older and had highly compensated cervical sagittal alignment preoperatively. They demonstrated postoperative cervical sagittal balance mismatch increases and slightly worse functional recovery. An extremely high C7 slope limited compensatory cervical lordosis following SL. These slides can be retrieved under Electronic Supplementary Material.

Narrow width of muscle-preserving selective laminectomy demonstrated sufficient surgical outcomes and reduced surgical invasiveness.

Sufficient width of laminectomy or laminoplasty is considered a criterion for successful surgical outcomes following posterior cervical decompression. No previous study has focused on surgical outcomes achieved by wide versus narrow decompression. This study examined whether narrow laminectomy width (LW) affected surgical outcomes in cervical compressive myelopathy (CCM). Between 2005 and 2010, we performed muscle-preserving selective laminectomy (SL) with decompression between the bilateral medial margin of the facet joints (wide SL). After 2010, we began to perform narrow SL, in which the LW was no more than 2-3 mm wider than the spinal cord width (SW). Clinical features and radiological findings from 97 CCM patients in whom SL was performed at two consecutive levels, including the C4/5 level, were examined in this study. The relationship between LW and patients' functional outcomes was analyzed. Mean blood loss was lower in the narrow SL group than in the wide SL group. The length of hospital stay was also shorter in the narrow SL group. The wide SL group showed greater posterior spinal cord shift. The incidence of C5 palsy correlated with LW and LW minus SW (LW-SW). The recovery rate (RR) of Japanese Orthopaedic Association score was comparable between the two groups. The RR was not correlated with LW and LW-SW. Sufficient functional recovery can be achieved by narrow SL, and it offers advantages over wide posterior decompression, including reduced surgical invasiveness and complications. Wide decompression width is not always necessary for CCM patients.

Posterior spinal cord shift does not affect surgical outcomes after muscle-preserving selective laminectomy.

Postoperative posterior spinal cord shift (PSS) has been considered a required radiographic endpoint of posterior decompression procedures. To achieve PSS, laminoplasty for cervical compressive myelopathy (CCM) has been consecutively performed on four or more laminae (C2-C7, C3-C7, or C3-C6). However, the clinical significance of PSS remains controversial. By selecting the surgically treated laminae, selective laminectomy (SL) can achieve adequate decompression without disturbing the extensor musculature and facet joints. The clinical features and radiological findings from 162 patients with CCM whose decompression included C4/5 level were investigated. The postoperative C2-C7 angle, PSS at C4/5 level, and laminectomy width were measured. Radiologic factors affecting PSS and the relationship between PSS and functional outcome were analyzed. Smaller PSS was observed in cases involving two or fewer consecutive laminectomies than in cases involving three or more consecutive laminectomies. The number of consecutive laminae (CLs) surgically treated and the postoperative C2-C7 angle correlated with PSS. Multiple linear regression analyses showed that the number of surgically treated CLs was the greatest predictor of PSS. No correlation was observed between PSS and the recovery rate (RR) of the Japanese Orthopaedic Association (JOA) score; RR of the JOA score was not affected even in patients with no PSS. PSS was affected by the number of CLs surgically treated and the postoperative C2-C7 angle. The magnitude of PSS never affected the RR of JOA score after SL. Therefore, for patients with CCM, PSS is not mandatory to obtain satisfactory functional recovery.