| BackgroundCervical spondylosis has become one of the common and frequently occurring illness in clinic and brought great hazardous to suffers, their families and society along with the development of society, population aging, and alteration of people's work and life styles especially. Technique of treatment is also in constant improvement following the development of medical science in a profound understanding of cervical disease. Although conflicting evidence exists, the majority of available evidence suggests that CSM is largely a surgical disease in the presence of symptoms and signs, appropriate radiographic evidence.Surgical techniques can be broadly divided into anterior surgery, posterior surgery, or combined anterior and posterior surgical techniques. Anterior decompression and fusion (ADF) allows direct removal of the compressive abnormality that compresses the spinal cord and nerve root from the front, with stabilization obtained by anterior arthrodesis. However, The disadvantages include the need for graft healing, related to bone grafting, such as dislodgement, fracture, and nonunion of the grafted bone and recurrence of myelopathy due to adjacent segment degeneration. Particularly, when three or more segments are involved, accelerated complication rates associated with anterior surgery, adjacent segment degeneration seen more obvious.The purpose of posterior surgical approaches is to expand spinal canal and to gain the decompression of the spine cord. Cervical laminoplasty has recently received increased attention for the treatment of cervical spondylotic myelopathy. Posterior based operations-such as laminectomy, laminectomy and fusion, and laminoplasty. Prior to the advent of anterior cervical spine surgery, laminectomy was the most common approach to decompression for multilevel myelopathy. However, there were significant problems associated with postlaminectomy kyphosis secondary to iatrogenic destabilization of the cervical spine, and lead to delayed neurological deterioration. Restenosis of spinal canal due to scar tissue formation, and will lead to spinal cord injury due to mild trauma.To address problems related to laminectomy, another alternative technique is laminectomy and fusion, which allows posterior canal expansion and maintains stability. This modification theoretically avoids problems associated with laminectomy alone, and it may allow reduction of kyphosis to lordosis. However, complications related to fixation include hardware failure with loss of alignment, radiculopathy, screw malposition, and the need for a repeated operation, and related to cervical instability due to accelerated adjacent segment degeneration. Laminectomy and fusion was limited further application in the clinical as these complications. Pal and Cooper found that 36% of the total load applied on the top of the specimen is transmitted through the anterior column formed by bodies and intervertebral discs, and 64% in posterior cervical columns formed by the facet joints and articular processes. The posterior columns plays a more important role in load transmission than anterior column. These prompted the development of a variety of methods to decompress the spine posteriorly, yet maintain postoperative stability by retaining the bulk of the posterior elements, redesigning configuration lamina and canalis vertebralis.Cervical laminoplasty has recently received increased attention for the treatment of cervical spondylotic myelopathy. Cervical laminoplasty has been used for the posterior decompression of the cervical spinal cord caused by cervical spondylosis, ossification of the posterior longitudinal ligament (OPLL), congenital spinal stenosis, or a combination of the above. Laminoplasty offers several advantages over traditional laminectomy and laminectomy with instrumented fusion. By preserving the posterior elements (lamina, spinous processes), it has been suggested that laminoplasty may decrease the incidence of postlaminectomy kyphotic deformity compared with laminectomy alone. Compared with laminectomy with instrumented fusion, laminoplasty may have a decreased incidence of adjacent level spondylosis by preserving cervical range of motion. Posterior-based procedures for spinal cord indirect decompression and its associated microcirculation rely on the ability of the cord to drift away from the anterior lesions as a result of releasing the posterior tethers (laminae, ligamentum flavum). Expansive laminoplasty was developed to achieve posterior spinal cord decompression while preserving cervical spine stability. There is small epidural scar and no aggravating spinal cord injury due to mild trauma. Among various methods of laminoplasty, unilateral open-door laminoplasty has been considered easier and safer than other methods. A desired outcome after open door cervical laminoplasty is the reconstruction of a stable laminar arch with sufficient room for the decompressed spinal cord.Once the laminae have been opened and the spinal cord has been decompressed, preventing restenosis is a primary concern. It is the most traditional way of maintaining door patency by sutures, and the lamina door is tethered open by sutures between the spinous process and facet capsule or paravertebral muscle fascia on the hinge side. However, there has the possibility of iatrogenic injury to the medial branches ramified from the dorsal ramus of the cervical nerves along the dorsolateral part of the facet joints during the cervical posterior approach, and it will cause neck pain, and hinge closure is easy to exist.To address problems related to sutures, another modified technique is unilateral open-door laminoplasty with suture anchor fixation, and tying and fixation of the sutures onto the holed lateral mass screws was used instead of the conventional method. However, cervical instability and hinge closure is still existence.To address problems related to way of maintaining door patency, various methods have been employed to maintain hinge patency and provide secure fixation, including autogenous or allogenic bone grafting, hydroxyapatite spacer and the miniplate osteosynthesis. Autografts are certainly the ideal spacer, offering considerable osteogenic and osteoconductive potential. However, donor site morbidity such as bleeding, ache, and sensation obstacle, and a second operation to harvest the graft are major disadvantages of autografts, and these were prohibited extensive application in the clinical. Allografts can provide structural support. However, the source is narrow and potential risk of viral transmission cannot be eliminated. Hydroxyapatite can provide structural support. However, it is poor reliability and difficult to use due to brittle, and it is not easy to acquire bone healing. Either autografts, allografts or Hydroxyapatite are needed to fashion into a self-locking configuration, relying on precise carpentry, the recoil of the hinges, and the force of the overlying musculature to secure the interlocking bone edges. Otherwise, additional instruments should be employed to avoid the risks of graft dislodgement. The expensive cost of commercial bone substitutes prohibits their use in developing countries.To address problems related to way of maintaining door patency, use of the titanium miniplate can help to minimize the problems with loss of canal expansion previously seen while facilitating the procedure. Use of the plate may also allow the patient to engage in rehabilitation protocol and possibly decrease the incidence of postoperative axial neck symptoms and loss of motion previously associated with laminoplasty. Rhee demonstrate that plate-only laminoplasty was effective in maintaining canal expansion without the need for supplemental bone graft struts, and it was not associated with the restenosis owing to hinge closure or dislodgements reported using alternative forms of fixation such as sutures. However, the cost of plate curently used is expensive. Ideally, a method of achieving laminar fixation should be technically straightforward, provide secure laminar fixation, and be rapid to minimize the risk of iatrogenic injuries, blood loss, and operative time, and be safe to minimize the risk of restenosis of the canal, and decrease axial neck pain following laminoplasty, and nervous paralysis, moreover cost is moderate.OsteoMed M3 plate and screws has been widely used in neurosurgery, maxillofacial, hand, and foot fractures, joint fixed and reconstruction surgery. The titanium plate is mesh shape, and the area is 4cmX5cm, and the thickness is 0.5 mm size. Self drilling screw, with diameter 2.0 mm and length 5.0 mm, can be easily twisted into bone. The length of screw is moderate, which decrease the risk of damaging spinal cord, nerve and vertebral artery due to too long screws, and avoid the risk of influence of fixed effect due to too short screws. OsteoMed M3 plates of sufficient size can be clipped into multiple small steel use, and can obviously reduce consumable expenses. In cervical posterior line plates were placed at all levels from C3 to C7 to allow adequate enlargement of the spinal canal, and the price is only 3,000 yuan which is equal to the cost of a piece of hand titanium plate, and which is more suitable for developing national condition, and has wide application prospects.To study the method for that OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty. The biomechanical clinical evaluation index:to measure the shortest distance between the entry point of 5mm screws and spinal canal, transverse foramen, and nerve root port, and to compare three-dimensional motional stability of 6 groups including OsteoMed M3 titanium plate and screws group, and to compare the fatigue experiment on expansive unilateral open-door laminoplasty of the cervical spine with OsteoMed M3 plate and screws, and to evaluate the pullout strength of different screw orientation, and to retrospectively review the surgical results of OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty. The object is to provide the theoretic basis for the widely clinical application and optimal selection of cervical posterior surgery.Objective1,To measure the shortest distance between the entry point of screws and spinal canal, transverse foramen, and nerve root port when OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty, and to evaluate the risk of damaging spinal cord, nerve and vertebral artery due to screws of 5mm length.2,To compare three-dimensional motional stability of different groups including OsteoMed M3 titanium plate and screws group, and to evaluate the method for that OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty and its immediate effects and initial stability of cervical vertebrae.3,To evaluate the method for that OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty and its immediate effects and initial stability of cervical vertebrae.4,To evaluate the method for that OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty and to evaluate the pullout strength of different screw orientation.5,We retrospectively described the technique and reviewed the surgical results of OsteoMed M3 titanium plate and screws were used to secure the posterior elements in the open position after expansive unilateral open-door laminoplasty.Method1,The CT scans of 100 patients without traumatic and cervical spine disease were random extracted and measured according to the imaging data by CT examination from The department of diagnostic radiology of Yuebei People's Hospital. There were 50 males with mean age 51.32 years (aged 20～86 years), and 50 females with mean age 43.54 years (aged 17～74 years). The anatomic data of cervical vertebrae in each group were measured and recorded using computerized image analysis software of HIS and PACS system.Measure indexes on CT were as follows:①The vertical shortest distance between junction of the lamina lateral margins of C3-C7 with the lateral mass medial margins of C3-C7 and spinal canal.②The shortest distance between junction of the lamina lateral margins of C3-C6 with the lateral mass medial margins of C3-C6 and transverse foramen.③The shortest distance between junction of the lamina lateral margins of C3-C7 with the lateral mass medial margins of C3-C7 and nerve root port.2,To select fresh cervical spine specimens(C1～T1)from 6 adult cadavers, and the specimens were dividede into intact cervical specimens group, sutures group, suture anchor fixation group, plate group, laminectomy group, and laminectomy and fusion group. The range of motion of different groups were measured by a three dimensional spinal stability test. The movement was applied with±2.0N.m loads in flexion/extension, left/right lateral bending, and left/right axial rotation on the three-dimension motion stability test. Multi-level motion was measured by using Motion Analysis motion capture system. The motion measure system included six infrared camera placed around cervical specimen and used specialized acceptable infrared, sphericity markers. Four markers were rigidly attached to each vertebral level(C3-C6) in noncolinear position and oriented to permit detection by infrared camera. Each marker motion coordinate was calculated by computer and angular displacement parameters were calculated, including the range of motion(ROM), neutral zone(NZ), and elastic zone(EZ), in flexion and extension, right/left lateral bending, and left/right rotation. ROM of treated cervical vertebrae were recorded and analyzed to evaluat effects of intact cervical specimens group, sutures group, suture anchor fixation group, plate group, laminectomy group, and laminectomy and fusion group.3,OsteoMed M3 plate and screws and silk ligation were used for an expansive unilateral open-door laminoplasty in six fresh human cervical spine specimens respectively, and fatigue experiment were executed in positions of flexion and extension on three-dimension motional stability test. The cessation of testing would be when the incidence of thread rupture and of loosening of thread, plate and screws were recorded.4,To select cervical spine fresh specimens(C1～T1)from 6 adult cadavers, and six fresh human cervical spine specimens were random numbered, and select C3,C4 and C5 total 18 segments sequence number. OsteoMed M3 plate and screws were used for an expansive unilateral open-door laminoplasty in these specimens respectively. The screws were inserted in lateral mass on the sequence and grouping at different extraversion angles:extraversion angle 0°group, extraversion angle 30°group and extraversion angle 45°group. The maxinum pullout strength was tested on the ElectroForce material testing machine. Axis pullout speed was 2mm/min, and whole pullout process of the screw was recorded, and the number of curve peaks was the maxinum pullout strength.5,25 patients with multilevel cervical disc herniation and canal stenosis were treated with an expansive unilateral open-door laminoplasty with OsteoMed M3 plate and screws. The follow-up period was over 6 months, and average follow-up period was 9 months (7 months～3 year). There were 18 male cases and 7 female cases. The age varied from 46 years old to 75 years old, and the average age was 61.4years old. The description for expansive unilateral open-door laminoplasty of the cervical spine with OsteoMed M3 plate and screws is as follows. The patient is placed in the prone position, and cervical spine is maintained in appropriate lordosis. A standard posterior midline incision is made down to the spinous processes. The paraspinal muscles are dissected laterally out to the lamina and the medial aspect of the lateral masses in the standard fashion. Care is taken during lateral exposure, not to disrupt the facet capsules. C6 and C7 spinous processes are shortened using a rongeur to the same height as C5. This prevents C6 and C7 spinous processes from impinging on the adjacent muscles when the laminae are hinged open. After identification of the interval between the lamina and the lateral mass, a bony trough is created with the high-speed 4- to 5mm burr, decorticating the posterior aspect of the lamina. The depth of the trough stops just superficial to the anterior cortex of the lamina. This is extended cephalad to caudad direction from one level above to one level below the involved stenotic levels. One trough corresponds to the hinge side of the door and the opposite side the aperture side of the door. The side with the most apparent clinical radiculopathy is often chosen as the open side, allowing foraminal decompression if required. On the aperture side, a 2- to 3-mm Kerrison rongeur is then used to remove the thinned anterior aspect of the lamina and interconnecting ligamentum. By completely removing the dorsal cortex and thinning the ventral cortex until a greenstick deformation of the hinge could be produced. The anterior aspect of the lamina on the hinge side is not removed and must remain intact. Additionally, the width of the trough should be slightly larger on the hinge side to prevent the walls of the trough from abutting. If the hinge fracture occurs at multiple levels, the laminoplasty should become a laminectomy by default. In each case, OsteoMed M3 plates of sufficient size to allow for adequate enlargement of the spinal canal were chosen, and plates were placed at all levels.5 mm mini-screws were placed into the lateral mass and the cut edge of the lamina through the plate in all cases. We encouraged the patients to do early active cervical exercises after 4 weeks surgery. The evaluate the improvement of spinal function after surgeries under JOA of Japaneses Orthopaedoc Association to analyse the effects and releated facters.Result1,The 95% normal lower limit of the shortest distance between junction of the lamina lateral margins of C3-C6 with the lateral mass medial margins of C3-C6 and transverse foramen were all greater than the length of 5mm screw, and the 95% normal lower limit of shortest distance between junction of the lamina lateral margins of C3-C7 with the lateral mass medial margins of C3-C7 and nerve root port were all greater than the length of 5mm screw. The 95% normal lower limit of vertical shortest distance between junction of the lamina lateral margins of C3-C7 with the lateral mass medial margins of C3-C7 and spinal canal were part less than the length of 5mm screw, especially in female patients.2,After expansive unilateral open-door laminoplasty, laminectomy and fusion group exhibited an decrease in angular motion in all directions and a significant increase in stability in all directions(P<0.05). Intact cervical specimens group was significantly different from sutures group, suture anchor fixation group, laminectomy group and laminectomy and fusion group in ROM of flexion/extension and left lateral bending(P<0.05), but intact cervical specimens group was not significantly different from the plate group. Intact cervical specimens group was significantly different from laminectomy group and laminectomy and fusion group in ROM of right lateral bending and right axial rotation(P<0.05), but intact cervical specimens group was not significantly different from sutures group, suture anchor fixation group and the plate group. Intact cervical specimens group exhibited a more significant different than other groups in ROM of left axial rotation (P<0.05).After expansive unilateral open-door laminoplasty, the plate group exhibited a more significantly different in angular motion than laminectomy and laminectomy and fusion group in ROM of extension and right lateral bending (P<0.05), and it was not significantly different from other groups. The plate group exhibited a more significantly different in angular motion than sutures group, laminectomy group and laminectomy and fusion group in ROM of flexion (P<0.05), and it was not significantly different from other groups. The plate group exhibited a more significantly different in angular motion than sutures group, suture anchor fixation group, laminectomy group and laminectomy and fusion group in ROM of left lateral bending (P<0.05). The plate group exhibited a more significant different than other groups in ROM of left axial rotation (P<0.05). The plate group exhibited a more significantly different in angular motion than suture anchor fixation group, laminectomy group and laminectomy and fusion group in ROM of right axial rotation.3,Partial rupture of joint capsule and easy move of the hinge side were seen in all of the specimens in the silk ligation. It was observed that rupture of joint capsule and cast of silk thread and reclose of the opened laminate as clinical widely used device for suture of joint capsule when the experiment was executed to the 73rd time and the 1806th time. There was no trauma on joint capsule in the OsteoMed M3 plate and screws, and no plate and screw loosening and rupturing and no reclose of the opened laminate.4,The maxinum pullout strength was (81.60±7.33)N for extraversion angle 0°group, (150.05±15.57)N for extraversion angle 30±group, (160.08±17.77)N for extraversion angle 45±group. The maxinum pullout strength of extraversion angle 0±group were less than extraversion angle 30±and 45±group(P<0.05). The pullout strength of extraversion angle 30±and 45±group were equal (P>0.05)5,All of 25 cases'follow-up period were over 6 months. Most of the patients had marked neurologic improvement after surgery. The mean JOA score increased significantly from 9.40±1.658 (range,5 to 13) before surgery to 13.80±1.958 (range,7 to 16) at final follow-up(t=-21.137, P=0.000). Mean recovery rate was 57.9%. Postoperative radiography, magnetic resonance imaging and computed tomography scan demonstrated significantly increased sagittal diameter and canal expansion. Two cases without relief of nurological symptoms underwent an additional anterior multilevel corpectomy. One case with ossification of the posterior longitudinal ligament had not good enough neurologic improvement after surgery. One patient had marked neurologic improvement after surgery, however died of another disease. No neurologic deterioration owing to hinge reclosure or major surgery-related complications were observed. Conclusion1,The results demonstrated that it was safer that the entry point of screws lied in the site among the lateral mass lateral margins and the lateral mass medial margins, and the risk of neural injury, spinal cord injury and vertebral artery injury could not occur.2,Expansive unilateral open-door laminoplasty with OsteoMed M3 plate and screws meets clinical and biomechanical requirements, and can remain the immediate effects and initial stability of cervical vertebrae.3,Unilateral open-door laminoplasty using OsteoMed M3 titanium plate and screws fixation is good for posterior cervical surgery because of its biomechanical advantage of maintaining significant stabilization of the spine.4,The pullout strength of the screws inserted extraversion angle over 30°provides stronger fixation than extraversion angle 0°in the unilateral open-door laminoplasty using OsteoMed M3 titanium plate and screws fixation.5,Unilateral open-door laminoplasty with OsteoMed M3 titanium plate and screws fixation effectively maintains expansion of the spinal canal and resists closure while preserving alignment and stability. This modified technique is easy to perform with a low complication rate and is good for clinical application. |
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