Open-door laminoplasty (ODLP) is considered an effective cervical medullary decompression procedure and has been widely used in the treatment of cervical spondylotic myelopathy (CSM). This procedure has many advantages. This procedure has many advantages: less reduction of spinal support and preservation of cervical spine stability; covering a large area of dura with bone tissue, reducing the compression of the cervical spinal cord by scar tissue; relatively little impact on the mobility of the cervical spine; and some prevention of posterior cervical sequence disorders and delayed neurological degeneration [1]. In this paper, we analyzed the clinical manifestations, imaging characteristics and long-term postoperative outcomes of 25 patients with spinal cord cervical spondylosis, aiming to explore the correlation between the efficacy of posterior cervical spine surgery and various imaging factors, and then provide reference indicators for the selection of treatment for spinal cord cervical spondylosis.
1.Data and methods
(1) Indications for surgery
(1) cervical spinal cord lesions caused by developmental spinal stenosis; (2) disc lesions of multiple vertebral segments (cervical spondylosis) or ossification of the posterior longitudinal ligament (OPLL) with lesions extending over three vertebral segments; (3) clinical symptoms caused by compression of the cervical spinal cord from the posterior side such as hypertrophy, calcification or ossification of the ligamentum flavum.
(2) Study subjects
Among the patients who underwent posterior “single-opening” vertebroplasty for spinal cord cervical spondylosis by the same surgical team in our department from August 1997 to February 2001, those who met the following conditions were included in the study: (1) the disease duration was more than one year; (2) the age was between 50 and 65 years; (3) there were clear preoperative cervical spine (3) clear preoperative cervical spine radiographs, CT films, MRI films, and postoperative and follow-up CT films, which can better show the pathological state of the cervical spine and spinal cord; (4) complete follow-up data; (5) exclusion of other comorbidities (such as post-traumatic degeneration, motor neuron disorders, etc.) that affect prognosis.
(3) Methods
①Recording the imaging characteristics of the patients: analysis factors including cervical curvature (mainly posterior convexity deformity), cervical stability, area of the spinal canal at the narrowest point before and after surgery and morphology and pathological changes of the cervical medulla of the corresponding segment (area measurement by CT, MRI workstation Archive Manager software).
(ii) Pre-operative, post-operative and follow-up conditions were scored according to the Japanese Orthopaedic Society’s functional assessment criteria for spinal cord damage (JOA score), respectively.
(iii) To perform linear or multiple regression and ANOVA on the imaging observation factors and clinical JOA scores, in addition to statistical processing such as randomization data and t-test for mean of paired data as needed and to make relevant statistical charts.
④ To avoid bias in judging, collecting and evaluating the results, this study used the “triple-blind” masking method, so that the evaluation of the study results could be conducted objectively.
2. Results
The number of cases in this group was 25, of which 16 were male and 9 were female. The age at the time of surgery ranged from 50 to 65 years, with a mean of 54.2 years; the duration of disease ranged from 12 months to 42 months, with a mean of 25.8 months; and the follow-up period ranged from 6 months to 48 months, with a mean of 26.3 months.
The imaging manifestations were: 10 cases with abnormal cervical curvature before surgery (mainly posterior convexity deformity, straightening of curvature was not included in the statistics), and the deformity was aggravated to varying degrees at postoperative follow-up; 6 cases with cervical instability in hyperflexion and hyperextension, 1 case with vertebral slippage and 5 cases with intervertebral angulation; 5 cases with signal changes in the spinal cord on MRI, all with T2 high signal and T1 low signal, 3 of which were long-segment extensive type and 2 Three of them were long-segment extensive type and two were limited type.
(1) Analysis of factors affecting prognosis
(1) Multiple regression analysis was performed with x1, x2, x3, x4, x5, and x6 representing the independent variables abnormal curvature, instability, intramedullary signal alteration, bony spinal canal area, spinal cord area, and preoperative JOA score, respectively, and y representing the response variable distant follow-up JOA score (JOA follow-up). The regression equation was established: y=4.886C0.633x1C1.217x2C0.735x3C0.016×4+0.044×5+0.761×6; while ANOVA was performed with P=7.9E-09, x2 and x5 partial regression coefficients were tested by t-test with P-values of 0.041 and 0.055 (close to 0.05), respectively, and x6 partial regression coefficient test with P value was 4.38E-05, and the complex correlation coefficient R=0.81. This regression equation was significant, and there was a linear correlation between cervical instability, spinal cord area and JOA preoperatively and long-term outcome, while there was no linear correlation between cervical curvature, intramedullary signal change, and bony spinal canal area and postoperative outcome of CSM.
②The independent variables x1, x2, x3, x4, and x5 were unchanged, and the response variable was the value of increase in JOA in the distant follow-up compared with the preoperative one. Statistical analysis was performed again, and the regression equation was obtained: y=5.406C0.827x1C1.234x2C1.153x3C0.016×4+0.014×5; P=0.0001, and the P values of x1 and x3 partial regression coefficient test were 0.072, 0.068 (close to 0.05), x2 partial regression coefficient test P value was 0.028, R=0.78. This regression equation was significant, and cervical curvature, instability, and intramedullary signal change were linearly correlated with the absolute score of postoperative symptom improvement, while spinal canal and spinal cord area were not related to it.
(2) Further investigation of the area of the spinal canal at the stenosis before and after surgery and its influence on postoperative outcome
The area of the bony spinal canal before and after surgery was 114.92±18.67 mm2 and 173.32±28.48 mm2, respectively, and the t-test showed a significant difference between the two (P<0.01), indicating that the ODLP surgery achieved the purpose of expanding the spinal canal and decompressing the lateral base. When the preoperative canal area was less than 100 mm2 or the postoperative canal area was less than 150 mm2, the follow-up JOA score decreased significantly, suggesting that the bony canal area is also a factor that cannot be ignored in determining the efficacy.
(3) Observation of the efficacy of ODLP after surgery
The JOA scores were 8.80±2.84 before surgery, 11.72±2.62 after surgery, and 12.56±3.07 at the long-term follow-up. t-tests were performed on paired data before and after surgery, postoperative and follow-up JOA scores, and the p-values were 1.61E-9 and 0.023, respectively, suggesting a significant difference between the means; the results indicate that the efficacy of posterior cervical spine surgery is certain, and the efficacy will be further improved at the long-term follow-up. The results indicate that the efficacy of posterior cervical spine surgery is certain, and the efficacy of long-term follow-up will be further improved.
3. Discussion
Imaging performance has an important reference value in the diagnosis and treatment of cervical spondylosis, and it is of clinical practical significance to predict the long-term efficacy of posterior cervical decompression surgery through imaging data. A variety of factors such as age, disease duration, disease, cervical spine stability, neurological comorbidities and imaging characteristics can affect the surgical efficacy of cervical spondylosis. The author restricted the selection of cases to eliminate the interference of too many factors and purify the correlation study between imaging factors and clinical efficacy as much as possible. The results of the study showed that the preoperative lesion degree was the most important factor affecting the prognosis among the factors predicting the outcome, while the role of each imaging factor was different.
(1) Degree of lesion
The preoperative JOA score directly influenced the postoperative and follow-up JOA scores, i.e., the preoperative functional status of the spinal cord largely determined the postoperative recovery, which further illustrates the importance of early diagnosis and early treatment of CSM. The significantly higher JOA scores after ODLP and the further improvement of clinical symptoms over time confirm that this procedure can provide long-term decompression of the spinal cord and has satisfactory efficacy. It has satisfactory curative effect.
(2) Cervical spine curvature
For patients with physiological curvature, the postoperative recovery is generally better, while for patients with loss of curvature, especially cervical retroflexion (lordosis), the deformity is more obvious and the spinal cord has less room to yield, so the decompression effect is often unsatisfactory because the stability of the cervical spine and the load balance in the spinal canal are affected after vertebroplasty. The results showed that postoperative spinal cord function was restored in those with cervical retroflexion without further aggravation, but appeared to reduce the expected surgical outcome. Therefore, for cases with significant retroflexion deformity, some consider it a relative contraindication to ODLP surgery and propose anterior decompression interbody fusion; however, fusion of three segments (or more) still brings a series of problems such as accelerated degeneration of the upper and lower segments and non-healing of the implants.
(3) Cervical instability
It is well documented that instability is often a major factor in cervical spine injury and determines prognosis. Cervical instability is measured on cervical hyperflexion and hyperextension radiographs, with vertebrae slipping forward or backward a distance greater than or equal to 3.5 mm or intervertebral angles greater than or equal to 11 degrees (the latter is also known as “physiological curve fracture”). Some authors consider intervertebral motion abnormalities to be more common in cervical degeneration and a more common sign of instability than spondylolisthesis. On the one hand, the hyper-limited activity of the unstable intervertebral space concentrates stress on the intervertebral junction, causing narrowing of the channel; on the other hand, it increases the mechanical irritation of the nerve tissue in the narrowed channel, which in turn induces a chronic inflammatory response to injury of the spinal cord. If preoperative instability is not taken seriously, the stability of the cervical spine will be reduced after ODLP. Although the local mechanical compression of the spinal cord is relieved for a short period of time, it will accelerate the cervical degeneration and chronic inflammation of the spinal cord, making the clinical symptoms aggravated after remission.
(4) Bony spinal canal or cervical spinal cord area at the stenosis
(1) The results showed no linear correlation between the area of the bony spinal canal and the improvement of neurological function before and after surgery.
There was no linear correlation between the area of the bony spinal canal and the improvement of neurological function before and after surgery; however, the cross-sectional area of the spinal cord before surgery and the prognosis correlated well, with higher scores and better prognosis for larger areas. On the one hand, it shows the importance of spinal cord decompression; on the other hand, it also indicates that the pathogenesis of CSM is not simply a reduction in spinal canal volume, but also the influence of physicochemical factors such as cervical degeneration instability, intervertebral disc degeneration, spastic occlusion of the anterior spinal cord vessels, and local inflammatory edema of the spinal cord [in the diagnosis and treatment of CSM, the comprehensive analysis of multiple imaging signs should be emphasized. This suggests that the clinical condition and prognosis should not be judged solely by the area of the spinal canal, and that intraoperative pursuit of increased spinal canal area should not reduce the stability of the cervical spine and allow epidural scar formation, otherwise the surgical efficacy will be affected.
(ii) Although the degree of spinal stenosis does not parallel its functional changes, a significantly reduced spinal canal area (<100 mm2) is often indicative of severe clinical symptoms and poor postoperative recovery; in patients with common developmental spinal stenosis combined with ossification of the posterior longitudinal ligament, the already narrowed spinal canal becomes even narrower based on extensive degeneration or multiple segmental lesions, resulting in rapid onset, severe disease, and poor prognosis.
③The results also showed that the prognosis was poor if the area of the spinal canal was still less than 150 mm2 after enlargement; many scholars suggested that the area of the spinal canal after decompression should be at least greater than 160 mm2, and it is appropriate for the vertebral plate to be lifted 5 mm from the dural sac. If the correlation between the area of the spinal cord after decompression and the improvement of neurological function can be explored, the pathogenesis of CSM will be better understood.
(5) Spinal cord signal changes
MRI is widely used in clinical practice, and changes in spinal cord signal provide important reference indicators for the assessment of spinal cord function, treatment and prognosis, but the impact on prognosis is uncertain due to the complexity of the imaging presentation, and often depends on the specific situation. The biochemical band diagrams of cellular activity can be directly observed on the active organism through the different changes of T1-weighted and T2-weighted image signals, and biochemical information of functional and metabolic processes in the whole organism can be obtained. The tissues in the damaged area of the spinal cord undergo a series of pathophysiological changes over time evolution from reversible changes in the acute phase (edema, hemorrhage) to irreversible changes in the chronic phase (degeneration, necrosis, cystic degeneration, etc.). Early on, it was thought that high signal was significantly correlated with clinical symptoms, degree of spinal cord compression and prognosis, and was often a sign of poorer prognosis; as research progressed, some scholars found no significant correlation between the two, and some even pointed out that patients with CSM with high T2-weighted signal had more significant postoperative symptom improvement, and some had The prognosis is better. The authors concluded that T2-weighted images with high signal have a certain reference value for determining the functional status and prognosis of the spinal cord, but they should be combined with T1-weighted images to provide more valuable information. When the spinal cord compression is further aggravated, necrotic cystic degeneration of the anterior horn cells of the spinal cord gray matter occurs, showing T1 low signal and T2 high signal. In addition, the extent of the lesion also affects the prognosis, with extensive areas of signal alteration predicting poor recovery; whereas limited lesions have relatively little impact on prognosis.
In conclusion, posterior cervical “single-opening” vertebroplasty is a relatively mature surgical technique with satisfactory postoperative follow-up. In addition to the condition that determines the prognosis, imaging has a greater impact on the prognosis in terms of cervical spine stability and spinal cord area; while cervical spine curvature, bony canal area and intramedullary signal changes before and after surgery often determine the degree of postoperative recovery on the basis of the condition.