Abstract: OBJECTIVE: To discuss the method of posterior craniocervical junction zone fixation technique and the clinical application experience of 27 cases. METHODS: To summarize 27 patients, 15 males and 12 females, aged 19-68 years, average 38 years, admitted between January 2004 and December 2007 with craniocervical junctional zone instability caused by various reasons; 21 cases of C1-C2 subluxation caused by various reasons, 1 case of dentate dislocation due to skull base depression via oral resection, 1 case of C1-C2 dislocation due to trauma, 1 case of slope chordoma via oral resection 3 cases before surgery, and 1 case of destruction of the circumoccipital joint due to intravertebral neurofibromatosis. All were treated with C2 pedicle-C1 lateral block/occipital screw internal fixation technique, and the surgical efficacy was evaluated by comparing preoperative and postoperative CT, MRI, and JOA scores. RESULTS: In two of the 27 patients, two C2 pedicle screws penetrated the bone cortex on postoperative CT review, but did not cause vascular or neurological compression; the remaining screws were well positioned; good bony fusion was formed in all cases. At 3-36 months of follow-up, one case showed no change in clinical symptoms compared with the preoperative period, and the remaining 26 cases improved. Conclusion: The C2 pedicle-C1 lateral block/occipital screw technique can be safely and effectively used for fixation within the craniocervical junction. Wu Hao, Department of Neurosurgery, Xuanwu Hospital, Capital Medical University
Keywords: craniocervical junctional zone; screw-titanium rod system.
The report of the application of the screw and rod fixation system for the cranial cervical junction region
Abstract Objective: To explore the value of the clinical application of screw and rod system in treatment of 27 cases of C1 and C2 destabilization patients . Methods: From 2004 May to 2007 Dec. 27 cases of C1-C2 destabilization patients were treated with posterior approach C1 lateral mass or occipital screws Male 15 cases, female 12 cases, from 19 to 68 years old, average 38 years old. 21 cases of C1-C2 subluxation, skull basilar impression 1 case, traumatic C1-C2 luxation 1 case, clivus chordoma 3 cases, intraspinal canal neurofibromatosis 1 case. All of the patients undertook CT JOA before and after operation were compared to evaluate the effect of the operation. Bony fusion was formed in all of the cases. Follow up the patients 3 to 36 months, all of the cases’ symptoms improve except 1 case’s Conclusion: C1 lateral mass or occipital screws and C2 pedical screws fusion is safe and effective method to treat C1-C2 The cranial cervical cavity is a very important part of the cervical cavity.
Key words: cranial cervical junction (CCJ), screw-rod sytem
The cranial cervical junction (CCJ) consists of an anatomical-functional complex of the occipital bone, the cricoid spine (C1) and the cardinal spine (C2), as well as the surrounding ligaments and other tissues. Various congenital and acquired factors can cause instability in this region, such as rheumatoid arthritis, trauma, tumors, congenital diseases, or infectious diseases [1]. The aim of surgical treatment of the craniocervical junction region is firstly to relieve the neural compression and secondly to fix the unstable spinal segments to make them fused and stable. In recent years, various screw-based nail plate and nail bar techniques have been increasingly used, and these internal fixation techniques can provide immediate postoperative stabilization with a high success rate of postoperative fusion, which is conducive to the later rehabilitation of patients. In this article, we present the application of the nail bar system for fixation within the craniocervical junction area in the context of the treatment experience of 27 patients.
1 Materials and methods
1.1 General information There were 27 patients in this group, 15 males and 12 females, aged 19-68 years old, average 38 years old; 21 cases of C1-C2 subluxation caused by various reasons, 1 case of dentate resection via oral cavity due to skull base depression, 1 case of C1-C2 subluxation caused by trauma, 3 cases of slope chordoma before surgery via oral cavity resection, and 1 case of destruction of the circumoccipital joint due to intravertebral neurofibromatosis. The patients all had symptoms of occipital neck pain and neck weakness before surgery, among which 24 cases were accompanied by symptoms of cervical medullary compression, presenting different degrees of vertebral bundle damage symptoms, limb numbness and weakness, and unstable walking. The mean preoperative JOA score was 7.4±1.6. All patients underwent preoperative CR in cervical forward and lateral and hyperextension and hyperflexion positions, and cervical spiral CT with 3D reconstruction of the upper cervical spine to analyze the reversibility of the cervical subluxation, as well as the C2 pedicle and transverse foramina. Patients sat up or moved out of bed wearing a regular neck brace for 3 days after surgery. At 3 months after surgery, the cervical spine CT was reviewed to evaluate the cervical fusion and JOA score was performed.
1.2 Surgical method
There were three types of internal fixation techniques used in this group of patients:
① C0-C2 nail bar fixation in 17 cases, which was applied to patients with circumferential occipital dislocation combined with circumferential occipital fusion.
(2) C1-C2 nail rod fixation in 6 cases, which was applied to patients with circumoccipital dislocation without combined circumoccipital fusion.
③ 4 cases of C0-C1 nail rod fixation were applied to patients with slope tumor involving one side of the circumoccipital joint, which led to the instability of the circumoccipital joint.
Preoperative cervical spiral CT scans were routinely performed, and the distance between the transverse foraminal curvature segment and the internal superior edge of the pedicle was measured by three-dimensional reconstruction images [2]. To determine the safety of C2 pedicle screw implantation. If it was judged preoperatively that the C2 pedicle was difficult to implant screws, the fixed segment was extended and C3 lateral block screw implantation was performed. In one of 21 patients with C1-C2 subluxation, C3 lateral block screws were used for fixation because of the narrow C2 pedicle on one side, which made it difficult to implant pedicle screws.
After fixation, the occipital scales, the posterior arch of C1 and the posterior edge of the C2 spinous process were decorticated, and cancellous bone particles of the posterior superior iliac spine were taken for bone grafting in the circumferential occipital joint and around the circumferential pivot joint.
Due to the anatomical peculiarities of the occipitocervical junction region, the methods of occipital, C1 lateral block and C2 pedicle screw implantation vary.
C0 nail placement method: The occipital nail is placed in the median crest of the occipital bone below the external occipital ridge, where the bone is thickest and the screw placement has the highest holding power and prevents the screw from penetrating the bone plate and causing damage to the brain tissue and venous sinuses. Usually only 2 screws are needed.
C1 lateral block screw placement method: The posterior part of the lateral block of the cricoid spine is continuous with the cricoid arch root. The posterior aspect of the lateral block of the cervical spine is explored along the subperiosteum and the puncture point can be identified at the lateral block. A depression is ground into the identified puncture site and a 1.0 mm diameter guide needle is drilled along the longitudinal axis of the pedicle and lateral block. A lateral cervical fluoroscopy is performed to observe the depth of the guide pin, and the pedicle screw is then screwed in (Figure 1).
Key points of C2 pedicle nail placement: Subperiosteal separation reveals the narrow part of the C2 pedicle and the internal superior edge of the pedicle, and the direction of nail entry is determined according to the direction of the internal superior edge of the pedicle, with the entry point chosen at the posterior edge of the narrow part. After the puncture point is determined, a hole is ground out of the bone cortex with a grinding drill, and a hand cone is drilled into the arch canal from there, which allows entry into the arch along the medullary cavity (Figure 2). However, in some cases (approximately 6.5%) there is a significant risk in implanting C2 pedicle screws with a diameter of 3.5-4 mm because of the narrow pivotal pedicle, which is less than 5 mm in diameter at its narrowest point [3]. Therefore, preoperative spiral CT with 3D reconstruction is routinely required to determine the condition of the C2 pedicle.
Method of repositioning using internal fixation instrumentation: In cases of fixation between the C1 lateral block and the C2 pedicle screw, after implantation of the screw, the titanium rod is trimmed to the appropriate length and fixed to the C2 pedicle screw first, and the horizontal dislocation between C1-C2 is reset by pushing forward on the C2 spinous process or the titanium rod, and the vertical dislocation between C1-C2 is reset by propping up the screw between C1-C2, and the reset is seen on fluoroscopy After satisfactory repositioning, the titanium rod was fixed by tightening the nut of the C1 lateral block screw. In the case of interscalene fixation between the occipital nail and the C2 pedicle screw, a similar interscalene bracing technique was used for repositioning and fixation.
1.3 Statistical methods of data
A paired t-test was used to compare the significance of the differences in preoperative and postoperative JOA scores in this group of patients, and the statistical software was SPSS 11.5.
2 Results
There were no spinal cord, nerve root or vertebral artery injuries during surgery. A total of 36 occipital nails, 18 C1 lateral block screws, 51 C2 pedicle screws, and 2 C3 lateral block screws were implanted. The cervical spine X-ray and CT were reviewed within 2 weeks after surgery, and all patients were followed up for 3-36 months, with a mean of 10.5 months, including frontal and lateral radiographs and lateral radiographs in hyperextension and flexion to determine the status of internal fixation and implant fusion, and the JOA score was performed at 3 months after surgery to assess the recovery of neurological function. Two C2 pedicle screws penetrated the bone cortex but did not cause compression of blood vessels and nerves, and the rest of the screws were well positioned; good bony fusion was formed in all cases. One case had no change in clinical symptoms after surgery compared with the preoperative period, and the remaining 26 cases improved. The average JOA score at 3 months after surgery was 13.2±1.0, and the JOA improvement rate was 60±12%. No displacement or fracture of the screws or titanium rods was observed during postoperative follow-up.
Discussion
Pathological changes of instability in the craniocervical junctional area include congenital, developmental and acquired abnormalities. Instability of the craniocervical junctional area can cause local bone and ligament destruction and lead to local pain, rotation restriction, C2 radiculopathy, and spinal cord compression. When instability of the craniocervical junctional area leads to neurological dysfunction, surgical treatment is required with the main goal of relieving neural compression, restoring the alignment of occipitocervical structures, and stabilizing the unstable spinal segments by fusing them [4].
The first internal fixation method frequently used in the craniocervical junction area was the cable fixation technique, the basic principle of which is to tighten the implant block, the posterior arch of the cervical spine, and the cardinal plate or spinous process by cable ligatures, relying on the fusion of the distal implant block to obtain long-term stability. The common disadvantage of all cable techniques is that they do not provide adequate immediate postoperative stability, require additional postoperative external fixation support, and are not suitable for patients with incomplete posterior cervical spine structures. The plate clamp is a posterior internal fixation technique for the cervical posterior spine that has been used after the cable technique and has better biomechanical results than the cable technique because of the more secure instrumentation, but the plate clamp is only suitable for cases with an intact posterior cervical arch and cervical lamina [5]. The later emergence of the nail plate technique and the nail bar technique overcomes the disadvantages of the first two posterior internal fixation techniques and has the advantage of providing immediate fixation and the posterior cervical arch and the pivot plate need not be intact at the time of use.
In this group of patients we used the nail and rod system internal fixation technique to treat instability in the craniocervical junction area caused by various diseases and achieved good results. In case of instability between C1 and C2 alone, we used C1 lateral block-C2 pedicle screws for fixation, which could obtain exact fixation while preserving 5° of intercraniocervical movement; while if the patient also had circumoccipital fusion, we used occipital-C2 pedicle screws for fixation, and three patients with craniocervical junction zone tumor in this group of cases were destroyed by tumor invasion of the circumoccipital joint, so we used The occipital-C2 pedicle screws were used for fixation. Before implantation of C2 pedicle screws, a spiral CT scan of the cervical spine with 3D reconstruction was routinely performed to evaluate the safety of C2 pedicle screw implantation. In one of the patients in this group, the C2 pedicle on the left side was small, with a diameter of only 2.3 mm, while the usual diameter of the implanted C2 pedicle screws was about 3.5 mm. Therefore, it was not possible to implant pedicle screws, so we extended a fixed segment and used C3 lateral block screws for fixation.
The nail bar system is easy to apply and exact fixation is achieved, and we also achieved a good repositioning effect by intraoperative correction of C1-C2 subluxation through intraoperative bracing between the occipital nail or C1 lateral block screw and C2 pedicle screw using the titanium bar as the axis.
Biomechanics has shown that screw fixation is stronger than wire or titanium cable binding techniques and can provide immediate postoperative stability, and patients can sit up or get out of bed with a cervical brace 2-3 days after surgery and can perform early rehabilitation exercises [6]. However, the effect of metal internal fixation is temporary due to the properties of metal internal fixation such as easy fatigue, loosening and fracture, and bony healing is required to achieve permanent strong fixation. In this group of cases, we removed the bone surface of the cortical bone and performed bone grafting between the small joints and around the internal fixation. A review of the CT at 3 months after surgery showed that a strong bony healing was achieved in all cases.
This technique has the advantages of precise fixation, intraoperative correction of C1-C2 dislocation by interscalene bracing technique, and early release from bed for rehabilitation exercises. However, the C2 pedicle needs to be evaluated prior to implantation of C2 pedicle screws to determine the risk of screw implantation.
Figure 1a Figure 1b
Figure 1 Patient Zhang, female, 55 years old, with dentate dysplasia, grade IV muscle strength in all four limbs, and labored breathing. A posterior C1 lateral block-C2 interpedicle screw fixation was performed. a The patient’s preoperative lateral CR showed a subluxation of the cricoaxial spine. b The patient’s postoperative lateral CR showed a satisfactory position of the C1 lateral block screw and C2 pedicle screw implantation and satisfactory repositioning of the cricoaxial spine.
Figure 2a Figure 2b
Figure 2c Figure 2d
Figure 2e
Figure 2 Patient Yang, female, 43 years old, with skull base depression combined with C0-C1 fusion. The patient was fixed with an occipital scale-screw-pivot screw interbody, and intraoperative correction of the cervical subluxation was achieved by the screw-sparing technique. a Preoperative cervical CT axial view of the patient showed the cervical subluxation and posterior displacement of the dentate process. b Preoperative cervical CT sagittal reconstruction of the patient showed the cervical subluxation and posterior displacement of the dentate process. c Postoperative cervical CT axial view of the patient showed complete repositioning of the cervical spine. d Postoperative cervical CT sagittal reconstruction of the patient showed complete repositioning of the cervical spine. The patient’s postoperative CT axial view shows complete repositioning of the cervical spine. e The patient’s postoperative CT axial view shows a well-positioned pedicle screw implantation.
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