Foundmental And Clincal Study Of Axial Symptoms After Laminoplasty

1 An experimental study of TNF-αcontent of intervertebral discs after open-door laminoplastyObjectives:Axial symptoms have an high occurrence rate,but the exactly mechanism of axial symptoms still remains unknown,so there are no methods at present to prevent or treat axial symptoms effectively after laminoplasty.Extensor musculature injury,ventral rami of cervical never irration and zygapophysial joint disorders are considered to be the main causes to postoperative axial symptoms,but all these hypotheses lack sound testimony. Clinical research results showed that the distribution area of postoperative axial symptoms had some segmental character,and this imply the occurrence of axial symptoms maybe due to intervertral disc degeneration,adjacent disc disease may be an unknown cause to postoperative axial symptoms.But conventional theory regard the adjancent disc disease as an inheretigate problem of anterior intervertebral fusion ,and as laminoplasty do not perform intervertebral fusion,so it will not interfere intervertebral degenerative process.we designed this study in order to make clear whether or not laminoplasy can promote the intervertebral degenerative process and the relationship between axial symptoms and adjacent disease.Methods:60 adult goats were divided into two groups,the experimental group underwent C3-C6 laminoplasty and the control group had a posterior incision made and the skin immediately closed.Lateral cervical spine radiographs were obtained preoperatively and 4 weeks,8 weeks and 12 weeks after operation and cervical curvature index(CCI)were measured.After the goats were killed,histological changes of interveterbral disc were observed using Masson and HE stain 12 weeks after operation. TNF-αlevel of C2-3,C3-4,C4-5,C5-6,C6-7 was also measured using ELISA kit at 4 weeks, 8 weeks and 12 weeks after operation.Results:(1)In control group,preoperative CCI was42.90%±5.88%,and postoperative CCI was 42.44%±5.70%,41.61%±5.48%and39.49%±5.67% in 4weeks,8weeks and 12 weeks after operation respectively,and no significient difference was found. But in experimental group,preoperative CCI was 45.04%±5.14%,and postoperative CCI was respectively 39.03%±8.66%,38.92%±8.03% and 36.51%±9.11% in 4weeks,8weeks and 12 weeks after operation,significient difference was found between preoperative CCI and 8 and 12 weeks postoperative CCI. P<0.01. (2)Histological observation showed that construction of intervertebral discs were normal both in control group 4 weeks,8 weeks and 12 weeks after operation and experimental group 4 weeks after operation,which collagen bundles were parallel,at right angles to the bundles of the adjacent lamellae and chondrocytes embedded in amorphous extracellular matrix with central clumped notochordal cells .In experimental group,mild disorganisation such as loss of the organized parallel arrangement of the lamellar fibres,tiny tears,and cellular proliferation in some areas were present in C2-3 and C6-7 interverbral discs 8 weeks after operation, and apparent loss of the distinct lamellar borders,extensive clefs and proliferation of chondrocyte were found in C2-3 and C6-7 interverbral discs 12 weeks after operation.Slight disorganization was also observed in C3-4,C4-5,C5-6 interverbral discs 12 weeks after operation in experimental group.(3)In experimental group,the TNF-αcontent of C2-3,C3-4,C4-5,C5-6,C6-7 intervertebral disc was 6.66±1.43ng/ml,5.50±0.78 ng/ml,6.02±1.27 ng/ml,5.97±1.47 ng/ml,6.60±1.70 ng/ml in 4 weeks after operation,and 9.93±1.63 ng/ml,5.79±1.21 ng/ml,6.31±1.54 ng/ml,7.10±1.54 ng/ml,8.97±1.75 ng/ml in 8 weeks after operation,and 12.17±2.48 ng/ml,6.72±1.26 ng/ml,7.64±1.52 ng/ml,7.23±2.28 ng/ml,11.36±2.25 ng/ml in 12 weeks after operation.The tendency of TNF-αcontent in intervertebral discs was increasing.This tendency was apparent in C2-3 and C6-7 intervertebral discs. the TNF-αcontent of C2-3 and C6-7 disc in experimental group was higher than that in control group 8 and 12 weeks after operation,P<0.01.Conclusions: ( 1 ) Laminoplasty can lead to TNF-αcontent of intervertebral discs increase postoperatively,which imply that degenerative process of intervertebral discs are promoted postoperatively. (2)The adjacent segment disease can occur similarly after laimnoplasty. (3)Pain originated form disc degeneration may be an important mechanism of axial symptom after laminoplasty.2 Anatomic Study of the Insertion and innervation of Semispinalis CervicisObjective:Some patients who had cervical laminoplasty with subsequent substantial loss of extention stability have shown failed healing of repaired semispinalis cervicis,and the unhealing of semispinalis cervicis will result in postoperative axial symptom .At present,the exactly reason for this pheno- mon still remains unknown.Most investigaton focous on how to preserve the integrity of semispinalis during operation,but little attention has been paid to the C2 insertion and innervating patterns of SSC. Precise anatomic study- results about the nerves and muscles in the posterior cervical spine was lack both domestic and abroad,and anatomic data of Chinese C2 insertion of SSC was also not available.So,we did this anatomic reseach,in order to find some clues for the unhealing of SSC after laminoplasty and imports for modified- operation methods.Methods:26 Chinese embalmed spines (14males and 12 females)were harvested for this study.Each of these 26 spines was sectioned form the base of occipital bone to the frist six thoracic vertebrae.Ramification course and distribution of cervical dorsal rami nerve and its anatomic relationship with the semispinalis cervicis,semispinalis capitis and multifidus was observed,and the risks for the cervical dorsal rami injury were also investigated.The length of the dorsal rami trunks and medial branches were also easured.After the soft connective tissues was thoroughly removed from the bony opening between the bilateral SSC insertions, the following parameters were -measured:(1)The C2 triangle ratio:the bilateral SSC insertions in C2 appeared to be triangular in the caudal view.The isosceles triangle created by the bilateral SSC insertions was referred to as C2 triangle,and width and height of that triangle were measured.The ratio of width to height was calculated referred to as C2 triangle ratio.(2)C2 length:a line was drawn across the surfaces of the inferior margins of the bilateral C2 inferior facets,and the distance between that line and the top of the C2 spinous process was measured as C2 length in the caudal view.(3)C2 angle:two lines were drawn by joining the cephalous apex with the bilateral caudal ends of the C2 spinous process,and the angle between the two lines was measured as the C2 angle in the back view.Results:(1) C3-8 dorsal rami arises from the spinal nerves,passing through osseofibrous aperture,osseofibrous cannl and tendinous decusssation fibers of semispinalis cervicis and multifidus muscle,and then supplied nuchal muscles,cervical zygapophysial joints and nuchal skin.2)The semispinalis cervicis is a composite muscle originate from the thoracic transverse processes of the frist six thoracic vertebrae and insert into the cervical spinous processes from C2 to C5.Despite its long running distances,the motor branches of SSC innervations originated from only two levels of the cervical dorsal rami.(3)At C3-8,the mean lengths of the DR trunks were 4.92±1.22mm,3.01±0.96mm,3.21±0.87mm,5.12±1.21mm,7.05±1.02mm,9.98±2.01mm respectively,and the mean length of the MB portion from point B to point P were 13.24±2.14mm,16.88±3.21mm,17.02±1.92mm,15.83±3.02mm,13.05±2.93mm,12.71±1.09mm respectively.(4)There were considerable individual variations in the morphologic features of the C2 spinous process and the C2 insertion of the semispinalis cervicis. The mean C2 angle was 44.6°±18.0°in males , and63.0°±14.7°in females,significant difficience was seen between two groups, P=0.005. (5)The C2 triangle ratio and C2 angle correlated with one another,P=0.003.Conclusions: (1)The innervating patterns of SSC and C4,C5MB injury during operation due to various reasons are the main cause of postoperative unhealing and deficiency of SSC,and a precise knowledge of the cervical dorsal rami anatomy and the innervating patterns of the paravertebral muscles is necessary for avoidance of inadvertent injuries to the nerves and occurance of axial symptom.(2)There were considerable individual variations in the morphologic features of the C2 spinous process and the C2 insertion of the semispinalis cervicis,this will bring in great difficulties for reattachment of SSC during laminoplasty.(3) Preoperative prediction of the morphologic features insertion at the original site is possible by measuring the opening angle of the C2 spinous process using three dimensional computed tomography because the muscle insertion correlated with the angle of the C2 spinousprocess.This information may be useful in reattaching the semispinalis cervicis during cervical laminoplasty.3 The impact on cervical axial symptom of modified open-door laminoplasy preserving the semispinalis cervicis insertionObjectives: cervical lamnoplasty has been reported to produce stable long-term neurologic improvement for cervical myelopathy, with benefits lasting over 10 years.However, the persistent axial symptoms after cervical laminoplasty often spoil patients'quality of life.Many authors have reported the risk factors of the axial symptoms, and some authors emphasized the importance of preserving the posterior muscles, especially the semispinalis cervicis (SSC) for preventing the symptoms. In conventional C3–C7 laminoplasty, however, it is very difficult to preserve the SSC insertion into C2 while opening the C3 lamina. Therefore, the SSC insertion in C2 has been transiently detached from the C2 spinous process and then repaired to the C2 spinous process at the time of wound closure. In laminoplasty,however, postoperative nonrepair of the SSC was reported to be found in some patients in whom the SSC insertion in C2 had been repaired to the C2 spinous process. For complete preservation of the SSC inserted in C2, therefore, the authors changed the laminoplastic procedure from C3–C7 laminoplasty to C4–C7 laminoplasty with C3 laminectomy in 2002. The purpose of this study was to clarify prospectively whether this modified laminoplasty preserving the SSC insertion into C2 could reduce the axial symptoms compared with C3–C7 laminoplasty reattaching the SSC to C2.Methods: Since March 2001 to March 2005,Forty-four patients who underwent modified open-door laminoplasy with semispinalis cervicis insert intact were included in this study(Group A). Fifty patients who underwent convitional open-door laminoplasty in the authors'department during the same period served as control(Group B). Preoperative and postoperative Japanese Orthopedic Association(JOA) scores ,the degree of axial symptom, ranges of neck motion, cervical curvature indices were recorded and compared.Results: The average recovery rate was 59.2%±11.3%for group A and 60.1%±19.5% for group B.There was no significant difference in JOA recovery rate between two groups.The rate of patients with evident axial symptoms was 25.0% in group A and 54.0% in group B,and the difference was statistically significant(P <0.05). Loss of cervical curvature index was 2.1%±1.6% in group A and 6.4%±3.2% in group B, and the different was of statistically significant(P< 0.01)。At the same time,loss of ranges of neck motion was 4.6°±4.0°in group A and 11.6°±7.8°in group B,significant difference was also seen (P< 0.01).Conclusions :Modified open-door laminoplasy with C3 Laminectomy is less invasive to the posterior extensor mechanism and can perserve semispinalis cervicis insert intact.This new procedure has the same surgical indications as C3-7 laminoplasty and is effective in preventing postoperative axial symptoms with adequate decompression of the spinal cord.