Quantitative evaluation for cervical foraminal bony stenosis based on angled sagittal slices along a nerve root on computed tomography

Cervical foraminal canal stenosis is a common disease, but any relationships between the measurement values of cervical foraminal canals and clinical symptoms have yet to be explored. We aim to determine a numerical cutoff point of cervical foraminal bony canal size that does not lead to radiculopathy so as to establish criteria for the surgical indication. We reconstructed angled sagittal slices along a nerve root on computed tomography (CT) on a workstation from pre-operative CT data and measured 1152 cervical foraminal canals (144 patients) from Cervical (C) 4/5 to C7/Thoracic (Th) 1. We evaluated the relationship between the size of foraminal canals and clinical manifestations. Receiver operating characteristic (ROC) analysis was used to calculate cutoff points of each foraminal canal size with positive neurologic manifestations. Of the 144 patients’ 1152 nerve roots, 286 nerve roots (24.8%) were diagnosed as radiculopathy by neurological examinations. The mean measured value of all foraminal canals on angled sagittal CT imagery was 3.39 ± 1.37 mm. The cutoff point of foraminal canal sizes without radiculopathy was 2.7 mm (sensitivity 0.680, specificity 0.591) overall. A cutoff point ascertained by quantitative evaluation of cervical foraminal canal size is useful for making diagnosis of cervical foraminal canal bony stenosis.     

Lumbar synovial cyst in an adolescent: case report

Background  Spinal extradural cysts are a rare cause of spinal cord or nerve root compression which tends to occur in the elderly but rarely reported in the under 20s. History  A 14-year-old girl with a 9-month history of left radicular pain was found to have an intraspinal cystic lesion causing radicular compression. MRI showed a 1.1-cm extradural cystic lesion with a low signal on T1 and high signal on T2-weighted images lying in the spinal canal at the L4 vertebral body level. The patient underwent an L4 hemi-laminectomy and excision of a synovial cyst, and the radicular pain completely regressed. Discussion  We discuss the pathogenesis, radiological techniques, and management of synovial cyst in a pediatric patient. Conclusion  Intraspinal ganglion cysts are extremely rare in children and only two other cases have been reported previously. They are benign lesions, frequently presenting radiculopathy, and should be considered in the differential diagnosis, in patients with low back pain and radiculopathy.     

Central Decompressive Laminoplasty for Treatment of Lumbar Spinal Stenosis : Technique and Early Surgical Results

Objective

Lumbar spinal stenosis is a common degenerative spine disease that requires surgical intervention. Currently, there is interest in minimally invasive surgery and various technical modifications of decompressive lumbar laminectomy without fusion. The purpose of this study was to present the author''s surgical technique and results for decompression of spinal stenosis.

Methods

The author performed surgery in 57 patients with lumbar spinal stenosis between 2006 and 2010. Data were gathered retrospectively via outpatient interviews and telephone questionnaires. The operation used in this study was named central decompressive laminoplasty (CDL), which allows thorough decompression of the lumbar spinal canal and proximal two foraminal nerve roots by undercutting the lamina and facet joint. Kyphotic prone positioning on elevated curvature of the frame or occasional use of an interlaminar spreader enables sufficient interlaminar working space. Pain was measured with a visual analogue scale (VAS). Surgical outcome was analyzed with the Oswestry Disability Index (ODI). Data were analyzed preoperatively and six months postoperatively.

Results

The interlaminar window provided by this technique allowed for unhindered access to the central canal, lateral recess, and upper/lower foraminal zone, with near-total sparing of the facet joint. The VAS scores and ODI were significantly improved at six-month follow-up compared to preoperative levels (p<0.001, respectively). Excellent pain relief (>75% of initial VAS score) of back/buttock and leg was observed in 75.0% and 76.2% of patients, respectively.

Conclusion

CDL is easily applied, allows good field visualization and decompression, maintains stability by sparing ligament and bony structures, and shows excellent early surgical results.     

Acute Contralateral Radiculopathy after Unilateral Transforaminal Lumbar Interbody Fusion

ObjectiveCases of contralateral radiculopathy after a transforaminal lumbar interbody fusion with a single cage (unilateral TLIF) had been reported, but the phenomenon has not been explained satisfactorily. The purpose of this study was to determine its incidence, causes, and risk factors.MethodsWe did retrospective study with 546 patients who underwent a unilateral TLIF, and used CT and MRI to study the causes of contralateral radicular symptoms that appeared within a week postoperatively. Clinical and radiological results were compared by dividing the patients into the symptomatic group and asymptomatic group.ResultsContralateral symptoms occurred in 32 (5.9%) of the patients underwent unilateral TLIF. The most common cause of contralateral symptoms was a contralateral foraminal stenosis in 22 (68.8%), screw malposition in 4 (12.5%), newly developed herniated nucleus pulposus in 3 (9.3%), hematoma in 1 (3.1%), and unknown origin in 2 patients (6.3%). 16 (50.0%) of the 32 patients received revision surgery. There was no difference in visual analogue scale and Oswestry disability index between the two groups at discharge. Both preoperative and postoperative contralateral foraminal areas were significantly smaller, and postoperative segmental angle was significantly greater in the symptomatic group comparing to those of the asymptomatic group (p<0.05).ConclusionThe incidence rate is not likely to be small (5.9%). If unilateral TLIF is performed for cases when preoperative contralateral foraminal stenosis already exists or when a large restoration of segmental lordosis is required, the probability of developing contralateral radiculopathy is increased and caution from the surgeon is needed.     

The redundant nerve root syndrome of the Cauda equina

The redundant nerve root syndrome is defined as the association of high-grade extradural lumbar spinal stenosis with large, elongated and tortuous nerve roots. Acquired elongation of nerve roots due to the mechanical trapping at the level of lumbar spinal stenosis is assumed to be the possible mechanism. It is believed that the cause is a squeezing force due to the chronic compression. The most common clinical symptoms are low back pain and leg pain. Although lumbar spinal canal stenosis is common, the entity has rarely been discussed in the literature. Here we present the MR imaging and intraoperative appearance of the condition with a brief discussion in a 71-year-old woman.     

Immediate postoperative MRI findings after lumbar decompression surgery: Correlation of imaging features with clinical outcome

An understanding of the common MRI findings observed after decompression surgery is important. However, to date, no study addressing this has been published. The aim of this study was to analyze and describe the immediate postoperative MRI findings after lumbar decompression surgery. We retrospectively analyzed the immediate postoperative MRIs of 121 consecutive patients who underwent lumbar decompression surgery between July 2017 and June 2018. Changes in stenosis at the decompressed and adjacent levels, epidural fat edema, epidural and subdural fluid collections, nerve root swelling, facet joint effusions, intervertebral disc signal, and paravertebral muscle edema were correlated with clinical characteristics. Both groups had reduced central canal stenosis postoperatively (p < 0.001) but worsened stenosis at adjacent segments. Fluid collection, hemorrhagic or non-hemorrhagic, at the laminectomy site was the commonest finding (one-level: 73.8%, two-level: 88.5%), with a higher percentage of severe central canal compromise in the two-level decompression group (p = 0.003). Other postoperative MRI findings, such as epidural fat edema, nerve root swelling, subdural fluid collection, and facet joint effusion, were noted without statistical significance. In conclusion, even with successful decompression for lumbar canal stenosis, increased central canal stenosis at adjacent segments is common on immediate postoperative MRI scans, showing no statistically significant correlation with the immediate postoperative outcome. Postoperative fluid collection at the laminectomy site is the commonest imaging finding, and higher rates of hemorrhagic fluid and more severe central canal compromise occur in two-level decompression, but rarely cause clinical problems.     

Limited Unilateral Decompression and Pedicle Screw Fixation with Fusion for Lumbar Spinal Stenosis with Unilateral Radiculopathy: A Retrospective Analysis of 25 Cases

ObjectiveLumbar spinal stenosis is conventionally treated with surgical decompression. However, bilateral decompression and laminectomy is more invasive and may not be necessary for lumbar stenosis patients with unilateral radiculopathy. We aimed to report the outcomes of unilateral laminectomy and bilateral pedicle screw fixation with fusion for patients with lumbar spinal stenosis and unilateral radiculopathy.MethodsPatients with lumbar spinal stenosis with unilateral lower extremity radiculopathy who received limited unilateral decompression and bilateral pedicle screw fixation were included and evaluated using visual analog scale (VAS) pain and the Oswestry Disability Index (ODI) scores preoperatively and at follow-up visits. Ligamentum flavum thickness of the involved segments was measured on axial magnetic resonance images.ResultsTwenty-five patients were included. The mean preoperative VAS score was 6.6±1.6 and 4.6±3.1 for leg and back pain, respectively. Ligamentum flavum thickness was comparable between the symptomatic and asymptomatic side (p=0.554). The mean follow-up duration was 29.2 months. The pain in the symptomatic side lower extremity (VAS score, 1.32±1.2) and the back (VAS score, 1.75±1.73) significantly improved (p=0.000 vs. baseline for both). The ODI improved significantly postoperatively (6.60±6.5; p=0.000 vs. baseline). Significant improvement in VAS pain and ODI scores were observed in patients receiving single or multi-segment decompression fusion with fixation (p<0.01).ConclusionLimited laminectomy and unilateral spinal decompression followed by bilateral pedicle screw fixation with fusion achieves satisfactory outcomes in patients with spinal stenosis and unilateral radiculopathy. This procedure is less damaging to structures that are important for maintaining posterior stability of the spine.     

Diagnosis of lumbar radiculopathy using simultaneous MR neurography and apparent T2 mapping

We sought to assess the utility of simultaneous apparent T2 mapping and neurography with the nerve-sheath signal increased by inked rest-tissue rapid acquisition of relaxation-enhancement imaging (SHINKEI-Quant) for the quantitative evaluation of compressed nerves in patients with lumbar radiculopathy.Thirty-two patients with lumbar radiculopathy and 5 healthy subjects underwent simultaneous apparent T2 mapping and neurography with SHINKEI-Quant. Regions of interest (ROIs) were placed in the lumbar dorsal root ganglia (DRG) and the spinal nerves distal to the lumbar nerves bilaterally at L4-S1. The T2 relaxation times were measured on the affected and unaffected sides. The T2 ratio was calculated as the affected side/unaffected side. Pearson correlation coefficients were calculated to determine the correlation between the T2 relaxation times or T2 ratio and clinical symptoms. An ROC curve was used to examine the diagnostic accuracy and threshold of the T2 relaxation times and T2 ratio.We observed no significant differences in the T2 relaxation times between the nerve roots on the left and right at each spinal level in healthy subjects. In patients, lumbar neurography revealed swelling of the involved nerve, and prolonged T2 relaxation times compared with that of the contralateral nerve. The T2 ratio correlated with leg pain. The ROC analysis revealed that the T2 relaxation time threshold was 127 ms and the T2 ratio threshold was 1.07.To our knowledge, this is the first study to show the utility of SHINKEI-Quant for the quantitative evaluation of lumbar radiculopathy.     

Lumbar synovial cyst in a adolescence: case report

Background  Spinal extradural cysts are a rare cause of spinal cord or nerve root compression which tends to occur in the elderly but rarely reported in the under 20s. History  A 14-year-old girl with a 9-month history of left radicular pain was found to have an intraspinal cystic lesion causing radicular compression. Magnetic resonance imaging showed a 1.1-cm extradural cystic lesion with a low signal on T1-weighted images and high signal on T2-weighted images lying in the spinal canal at the L4 vertebral body level. The patient underwent an L4 hemilaminectomy and excision of a synovial cyst, and the radicular pain completely regressed. Discussion  We discuss the pathogenesis, radiological techniques and management of synovial cyst in a paediatric patient Conclusion  Intraspinal ganglion cysts are extremely rare in children and only two other cases have been reported previously. They are benign lesions, frequently presenting radiculopathy, and should be considered in the differential diagnosis in patients with low back pain and radiculopathy.     

Increased thickness of lumbar spine ligamentum flavum in wild-type transthyretin amyloidosis

BackgroundWild-type transthyretin (ATTRwt) amyloid deposits have been found in the ligamentum flavum of patients undergoing surgery for spinal stenosis. The relationship between ATTRwt and ligamentum flavum thickness is unclear. We used pre-operative magnetic resonance imaging (MRI) to analyze ligamentum flavum thickness in lumbar spinal stenosis patients with and without ATTRwt amyloid.MethodsWe retrospectively identified 178 patients who underwent lumbar spine surgery. Ligamentum flavum thickness of 253 specimens was measured on T2-weighted axial MRI. Amyloid presence was confirmed through Congo red staining of specimens, and ATTRwt was confirmed using mass-spectrometry and gene sequencing.ResultsTwenty four of the 178 patients (13.5%) were found to have ATTRwt in the ligamentum flavum. Forty ATTRwt specimens and 213 non-ATTRwt specimens were measured. Mean ligamentum flavum thickness was 4.92 (±1.27) mm in the ATTRwt group and 4.00 (±1.21) mm in the non-ATTRwt group (p < 0.01). The ligamentum flavum was thickest at L4-L5, with a thickness of 5.15 (±1.27) mm and 4.23 (±1.29) mm in the ATTRwt and non-ATTRwt group, respectively (p = 0.007). There was a significant difference in ligamentum flavum thickness between ATTRwt and non-ATTRwt case for both patients younger than 70 years (p = 0.016) and those older than 70 years (p = 0.004). ATTRwt patients had greater ligamentum flavum thickness by 0.83 mm (95% confidence interval (CI): 0.41–1.25 mm, p < 0.001) when controlled for age and lumbar level.ConclusionPatients with ATTRwt had thicker ligamentum flavum compared to patients without ATTRwt. Further studies are needed to investigate the pathophysiology of ATTRwt in ligamentum flavum thickening.     

Value of repeat CT scans in low back pain and radiculopathy

We assessed the clinical value of repeat spine CT scan in 108 patients aged 18–60 years who underwent repeat lumbar spine CT scan for low back pain or radiculopathy from January 2008 to December 2010. Patients with a neoplasm or symptoms suggesting underlying disease were excluded from the study. Clinical data was retrospectively reviewed. Index examinations and repeat CT scan performed at a mean of 24.3 ± 11.3 months later were compared by a senior musculoskeletal radiologist. Disc abnormalities (herniation, sequestration, bulge), spinal stenosis, disc space narrowing, and bony changes (osteophytes, fractures, other changes) were documented. Indications for CT scan were low back pain (60 patients, 55%), radiculopathy (46 patients, 43%), or nonspecific back pain (two patients, 2%). A total of 292 spine pathologies were identified in 98 patients (90.7%); in 10 patients (9.3%) no spine pathology was seen on index or repeat CT scan. At repeat CT scan, 269/292 pathologies were unchanged (92.1%); 10/292 improved (3.4%), 8/292 worsened (2.8%, disc herniation or spinal stenosis), and five new pathologies were identified. No substantial therapeutic change was required in patients with worsened or new pathology. Added diagnostic value from repeat CT scan performed within 2–3 years was rare in patients suffering chronic or recurrent low back pain or radiculopathy, suggesting that repeat CT scan should be considered only in patients with progressive neurologic deficits, new neurologic complaints, or signs implying serious underlying conditions.     

Occurrence of discal and non-discal changes after sequestrectomy alone versus sequestrectomy and implantation of an anulus closure device

Sequestrectomy alone represents a procedure for the treatment of lumbar disc herniation. For selected cases, an anulus closure device (ACD) can be implanted which may result in lower reoperation rates. However, comparative magnetic resonance imaging (MRI) changes and their clinical relevance of both procedures are unclear and have not been reported so far.Clinical and MRI data of patients after limited discectomy with ACD implantation (group ACD; N = 45) and patients after sequestrectomy alone (group S; N = 40) with primary lumbar disc herniation were compared retrospectively. Pain intensity on the visual analogue pain scale (VAS), oswestry disability index (ODI) or the patient satisfaction index (PSI) were collected. Disc signal intensity, Modic type changes, endplate reactions, anular tears and reherniations were investigated using MRI before and <18 months postoperative. Morphologic changes were correlated with clinical outcome.There was no difference in VAS back, VAS leg or ODI/PSI after the operation although group S showed significantly more reherniations in MRI. The overall rate of repeated surgery at the same level was similar with a trend in favour of the ACD group (P = 0.729). Significantly more patients of the ACD group experienced endplate erosions after surgery (P < 0.001). Both groups experienced progression of disc signal intensity, Modic type changes, and anular tears with most MRI signs being without clinical relevance.ACD implantation is associated with a significantly lower reherniation rate in MRI but showed a significantly higher rate of endplate erosions. The structural changes do not appear to be clinically relevant.     

Lumbar Epidural Varix Mimicking Disc Herniation

Lumbar radiculopathy is generally caused by such well-recognized entity as lumbar disc herniation in neurosurgical practice; however rare pathologies such as thrombosed epidural varix may mimic them by causing radicular symptoms. In this case report, we present a 26-year-old man with the complaint of back and right leg pain who was operated for right L4–5 disc herniation. The lesion interpreted as an extruded disc herniation preoperatively was found to be a thrombosed epidural varix compressing the nerve root preoperatively. The nerve root was decompressed by shrinking the lesion with bipolar thermocoagulation and excision. The patient''s complaints disappeared in the postoperative period. Thrombosed lumbar epidural varices may mimic lumbar disc herniations both radiologically and clinically. Therefore, must be kept in mind in the differential diagnosis of lumbar disc herniations. Microsurgical techniques are mandatory for the treatment of these pathologies and decompression with thermocoagulation and excision is an efficient method.     

Bilateral decompression of multilevel lumbar spinal stenosis through a unilateral approach.

Lumbar canal stenosis due to hypertrophy and calcification of the facet joints and/or ligamentum flavum is a common condition in the elderly. Although a large number of individuals are symptom-free, the degenerative process, usually encroaching on both central and lateral pathways, may lead to symptoms of itself or decompensate a preexisting narrow canal. Even at an advanced age, decompression surgery is effective for symptomatic stenosis. Less invasive procedures preserving maximal bony and ligamentous structures have recently been recommended to reduce associated morbidity. This paper introduces a unilateral surgical approach for bilateral decompression by ligamentectomy, partial facetectomy and foraminal unroofing. Using a specially designed, one-side retractor, after the ipsilateral nerve root decompression the contralateral dural sac and nerve roots were approached through an 8 x 15 mm window in the interspinous ligament. The contralateral ligamentum flavum, facet joints and foraminal roof were resected, preserving the supraspinous ligament complex and much of the contralateral musculature. This technique, preserving anatomy and biomechanical function of the lumbar spine, is useful for surgery on multilevel lumbar canal stenoses.     

The minimally invasive paramedian approach for foraminal disc herniation

Foraminal disc herniation presents with an operative challenge, as it often requires facetectomy, which can result in segmental instability. The intraforaminal approach includes partial pars resection and medial facetectomy and allows for direct visualization of the nerve roots and herniated disc in the foramen without violating the joint, with good clinical outcomes. Herein, we describe a retrospective series of patients that underwent minimally invasive paramedian approach with hemilaminectomy, partial medial pars resection, medial facetectomy for foraminal disc herniation. Demographics and clinical outcomes were obtained from medical records. Improvement in functional outcomes was evaluated using the pre and post-operative Visual Analog Scale (VAS) and Oswestry Disability Index (ODI). A total of 23 patients were included in this study. The average age was 56.47 ± 9.4 yrs and body mass index was 31.92 ± 7.7 kg/m². 47.8% of cases were L4-5 FDH. The estimated blood loss was 31.32 ± 19.8 ml. The average length of hospital stay was 1.11 ± 0.3 days. All patients were discharged home. Overall, there was a significant improvement in the VAS (pre-op: 8.21 ± 2.1; post-op: 2.59 ± 2.7; p-value: <0.0001) and ODI (pre-op: 57.16 ± 13.2; post-op: 21.47 ± 9.9; p-value: <0.0001). The minimally invasive paramedian approach provides satisfactory outcomes as a safe strategy in the treatment of foraminal disc herniation. Herein, there was a significant improvement in pain and functional outcomes, minimal blood loss and decreased hospital stay.     

Minimally Invasive Muscle Sparing Transmuscular Microdiscectomy : Technique and Comparison with Conventional Subperiosteal Microdiscectomy during the Early Postoperative Period

Objective

The authors introduce a minimally invasive muscle sparing transmuscular microdiscectomy (MSTM) to treat herniated lumbar disc disease. Its results are compared with conventional subperiosteal microdiscectomy (CSM) to validate the effectiveness.

Methods

Muscle sparing transmuscular microdiscectomy, which involves muscle dissection approach using the natural fat cleavage plane between the multifidus to expose the interlaminar space, was performed in 23 patients to treat a single level unilateral lumbar radiculopathy. The creatine phosphokinase (CPK)-MM serum levels were measured on admission and at 1, 3, and 5 days postoperatively. Postoperative pain was evaluated using a 10-point visual analogue scale (VAS) and recorded on admission and at 1, 3, and 5 days postoperatively. The results were compared to those from the conventional subperiosteal microdiscectomy (43 patients).

Results

The CPK-MM levels were significantly lower in the serum of the MSTM group compared to the CSM group on postoperative days three and five (p = 0.03 and p = 0.02, respectively). The clinical scales for back pain using VAS were significantly lower in the MSTM group than in the CSM group on postoperative days three (p = 0.04). The mean VAS scores for leg pain in both groups showed no significant differences during the early postoperative period.

Conclusion

Muscle sparing transmuscular microdiscectomy is a minimally invasive surgical option to treat lumbar radiculopathy due to herniated disc. The approach affected minimal injury to posterior lumbar supporting structures with alleviated postoperative back pain.     

Sciatica due to unusual causes: Tarlov cysts and nerve roots anomalies

Tarlov cysts and nerve roots anomalies usually involve lumbosacral roots and are often asymptomatic. MRI has enabled recognition of many conditions that used to be missed by CT or myelography investigations performed for back and leg pain. However, even without additional compressive impingement (disc hernia, spondylolisthesis or lumbar canal stenosis) these anomalies can be responsible for sciatica, motor deficit and bladder sphincter dysfunction. Tarlov cysts are perinervous dilatations of the dorsal root ganglion. CT and especially MRI can reveal these cysts and their precise relations with the neighboring structures. Delayed filling of the cysts can be visualized on the myelogram. MRI is more sensitive than CT myelography for a positive diagnosis of nerve root anomalies, a differential diagnosis with disc hernia and classification of these anomalies. Surgical treatment is indicated for symptomatic Tarlov cysts and nerve root anomalies resistant to conservative treatment. Better outcome is observed in patients with an additional compressive impingement component. We report two cases of sciatica: one caused by Tarlov cysts diagnosed by MRI and the other by nerve root anomalies diagnosed by CT myelography. In both cases, conservative treatment was undertaken. The clinical, radiological and therapeutic aspects of these disorders are discussed.     

经皮内镜椎间孔成形术治疗椎间孔狭窄性腰腿痛短期疗效观察

目的探讨侧后路经皮椎间孔镜下椎间孔成形术治疗椎间孔狭窄性腰腿痛的短期疗效。方法回顾性分析25例经MRI证实的椎间孔狭窄病例资料,采用侧后路经皮椎间孔镜下椎间孔成形术,其中腰L4～L5为9例,L5～S1 16例。分析治疗前及治疗后1周,术后1、3、6个月视觉模拟评分（visual analogue scale,vAs）变化及术后6个月MacNab评分。结果25例随访6。10个月,术后VAS较术前明显降低（P=0．000）。术后6个月MacNab评分：优11例,良12例,可2例,优良率92．0％。结论侧后路经皮椎间孔镜下椎间孔成形术治疗椎间孔狭窄性腰腿痛短期疗效满意。     

C7神经移位经背侧入路椎管外吻合腰神经前根重建截瘫下肢迈步功能的应用解剖

背景：利用周围神经移位重建截瘫平面以下的肢体运动及尿便功能方面已经做了很多有意义的工作,在选择移位神经及如何重建截瘫患者迈步方面没有定论。 目的：为C7神经移位经背侧入路椎管外吻合腰神经前根重建提供解剖学基础。 方法：在12例成人尸体标本上,经背侧入路观测椎管外L2,L3 ,L4神经前根的显露、排列及可切取长度、C7神经转移路径距离及胫神经可切取长度。 结果与结论：经背侧入路椎管外L2,L3,L4神经前支可辨认,L2,L3,L4神经前支的可切取长度为(1.81±0.35),(2.20±0.37),(1.45±0.31) cm;胫神经可切取长度(63.87±4.23);C7至梨状肌下孔的距离为(65.65±2.98) cm;C7至L2 ,3,4神经前支距离分别为(50.83±5.58),(53.15±5.82),(55.93±6.51) cm。胫神经可切取长度能够满足C7至梨状肌下孔的距离及C7至L2,L3,L4神经前支距离。结果提示,C7神经作为动力神经源,胫神经可选择为桥接神经,经背侧入路椎管外吻合L2,L3,L4神经前根重建截瘫迈步功能的具有可行性。