Anterior cervical subtotal vertebrectomy and bone graft fusion internal fixation is a common surgery for treatment of irtervertebral disc protrusion and cervical spondylotic myelopathy. Anterior cervical decompression is generally performed by to remove the ventral pressure to spinal cord. It is characterized by direct thorough decompression and little interference to spinal cord, which prevents secondary injury and is conducive to the neurological function recovery under relatively normal physiological environment. Conventional decompression range includes intervertebral disc tissue and bone spurs. In addition, peripheral erosion during slot opening in the cervical vertebra can enlarge decompression range. In addition to direct removal of ventral pressure to spinal cord, anterior cervical subtotal vertebrectomy and bone graft fusion internal fixation can make titanium mesh or iliac bone grafts fused and fixed, allowing for re-stabilization of diseased segments[4]. Simple anterior decompression and bone grafting easily result in many adverse events due to poor stabilization in particular for many segment surgery, including bone graft loosening and displacement, low bone graft fusion rate, loss of intervertebral space height and trachelokyphosis. In contrast, immediate stability provided by steel plate internal fixation can retrieve the drawbacks above mentioned. Jin et al[5] reported that any patients who are involved in subtotal or total vertebrectomy and bone graft fusion can choose anterior cervical internal fixation.
Evidence exists that application of anterior cervical steel plate leads to a 92%-100% bone graft fusion rate for one segment of lesions and a 70%-100% fusion rate for two or more segments of lesions[6-7]. Anterior cervical steel plate shows the following several biological characteristics: first, strong supporting function increases the stability of diseased segments, reduces the movement between bone grafts and end plate, and enhances fusion rate. Second, reducing complications of intervertebral grafts, such as preventing from graft prolapsed. Third, preventing from trachelokyphosis and keeping the balance of cervical vertebra in the sagittal level. Steel plate pre-curved with certain radian can attach to the cervical vertebra, which improves the physiological curvature of cervical vertebra, reduces the arm of force, optimizes stress transduction, and enhances stability and fixation force[8], providing good local mechanics for improvement in neurological function after surgery.
Anterior cervical steel plate obviously reduces complications, but a series of other complications appear, including screw loosening and prolapse, internal fixation fragmentation, and injury to esophagus and peripheral tissue caused by the screws prolapsed from the steel plate. For multi-segment anterior cervical discectomy and fusion, anterior locking plate can greatly enhance the stability of bone grafts, effectively maintain the physical curvature of cervical vertebra, and prevent intervertebral height loss and the mechanical transduction abnormality among adjacent segments[9-11]. The anterior locking titanium plate used in the present study exhibits the following characteristics: first, integrated structure can effectively prevent screw withdrawal. Second, in the flexion and extension positions of cervical vertebra, there are tension band and supporting effects, the stability of cervical vertebra in fixed segments is strengthened and the fusion rate of bone grafts is increased. Third, the fixation screws do not penetrate the posterior border of the vertebral body. Fourth, internal fixation system equipped with locking screws are made of titanium or titanium alloy, with good histocompatibility and tolerance to corrosion and produce small influence on postoperative magnetic resonance imaging. Fifth, the tapered worm in the nail-tail and the inner ring in the steel plate form pressurized caging; screw direction can be adjusted, with the characteristics of one-screw multi-direction fixation, which allows increased fixation range.
Caution should be taken during and after anterior cervical decompression combined with bone grafting and titanium plate internal fixation. First, thorough decompression is the key to surgery. During slot opening to decompress, attention should be paid to the bone spurs in the posterior border of the vertebral body, in particular full examination of the corner of the slot opened. In addition, caution should be taken to resect the posterior longitudinal ligament. In the present study, 23 patients showed suspected intervertebral disc-caused pressure under the complete posterior longitudinal ligament; 79 patients demonstrated thickened posterior longitudinal ligament to different degrees, and 35 patients presented local calcification or ossification in the posterior longitudinal ligament, resulting in pressure to the dura mater. Therefore, the key to ensure the curative efficacy of the surgery is to resect the posterior longitudinal ligament in the corresponding segments to be decompressed as possible[12]. Second, this surgery reserves bony end plate above and below the bone slot, prevents titanium mesh collapse into the vertebral body, and effectively maintains the height of fused segments. At the same time, the intervertebral disc tissue and cartilage end plate not thoroughly removed would influence the environment of bone grafting. Therefore, caution should be taken to manage the superior and inferior ends of the intervertebral body. Our experience is that with the assistance of C-arm X-ray machine, the superior and inferior end plates are treated under the condition of slot opening based on precise contrast with the superior and inferior borders of the intervertebral body prior to decompression. Third, superior laryngeal nerve injury is commonly induced by intraoperative electric coagulation burning and long-time bracing. Great vessel and esophagus injury is commonly induced by improper intraoperative pulling and hooking or excessive bracing force. Spinal cord injury and Horner's syndrome should be also avoided, which are induced by unclear anatomical relationship and careless manipulation. After surgery, cervical vertebra should be protected by avoiding long-term bending over desk working and sleep with high pillow. Neck support should be used within postoperative 6-8 weeks.
This study is a retrospective, controlled case analysis. Anterior cervical subtotal decompression combined with bone grafting and locking plate internal fixation for treatment of cervical spondylotic myelopathy can thoroughly decompress and achieve stable bone fusion and reconstruction, with satisfactory clinical efficacy. This surgery is safe and reliable. But precise long-term curative efficacy needs further investigation for limited case numbers and various follow-up periods.
