Translaminar screws of the axis—an alternative technique for rigid screw fixation in upper cervical spine instability

C2 pedicle screws or transarticular atlantoaxial screws are technically demanding and carry an increased risk of vertebral artery injury. In up to 20% of cases, pedicle and transarticular screw placement is not possible due to a high-riding vertebral artery or very small C2 pedicles in addition to other anatomical variations. Translaminar screws have been reported to rigidly capture posterior elements of C2 and therefore appear to be a suitable alternative. We present our first experiences and clinical results with this new method in two neurosurgical spine centers. Twenty-seven adult patients were treated between 2007 and 2010 in two neurosurgical spine departments with C2 translaminar screw fixation for upper cervical spine instability of various origins (e.g., trauma, tumor, dens pseudarthrosis). Eight patients were men and 19 were women. Mean age was 68.9 years. In most cases, translaminar screws were used because of contraindications for pedicle or transarticular screws as a salvage technique. All patients were clinically assessed and had CT scans postoperatively to verify correct screw placement. Follow-up was performed with reexamination on an ambulatory basis. Mean follow-up was 7.6 months for all patients. In 27 patients, 52 translaminar screws were placed. There were no intraoperative complications. Postoperatively, we identified four screw malpositions using a new accuracy grading scale. One screw had to be revised because of violation of the spinal canal >4 mm. None of the patients had additional neurological deficits postoperatively, and all showed stable cervical conditions at follow-up. Two patients died due to causes not associated with the stabilization technique. The fusion rate for patients with C1/C2 fixation is 92.9%. Translaminar screws can be used at least as an additional technique for cases of upper cervical spine instability when pedicle screw placement is contraindicated or not possible. The current data suggest comparable biomechanical stability and fusion rates of translaminar screws to other well-known posterior fixation procedures. In addition, translaminar screw placement is technically less demanding and reduces the risk of vertebral artery injury.     

Posterior C2 fixation using bilateral, crossing C2 laminar screws: case series and technical note

Rigid screw fixation of the axis, for either atlantoaxial fixation or for incorporation of C2 into subaxial cervical constructs, provides significant stability and excellent long-term fusion results but remains technically demanding due to the danger of injury to the vertebral artery. Anatomic variability of the foramen transversarium in the body of the axis can preclude safe transarticular C1-C2 screw placement in up to 20% of patients. Although more recent methods of C2 screw fixation with pedicle screws allow safer fixation in a higher number of patients, there remains a significant risk to the vertebral artery with C2 pedicle screw placement. The author describes a novel technique of C2 rigid screw fixation using bilateral, crossing C2 laminar screws, not previously reported in the literature, which does not place the vertebral artery at risk during C2 fixation. This technique has been successfully used by the author in cases of craniocervical and atlantoaxial fixation as well as for incorporation of C2 into subaxial fixations. The technique is illustrated, and the author's initial experience in treating 10 patients with crossing, bilateral C2 aminar screws for indications of trauma, neoplasm, pseudarthrosis, and degenerative disease is reviewed. The possible advantages of C2 fixation with C2 laminar screws are discussed.     

C2 laminar screw and C1-2 transarticular screw combined with C1 laminar hooks for atlantoaxial instability with unilateral vertebral artery injury

Transarticular screw fixation (TASF) is technically demanding, with high risk of vertebral artery (VA) injury. How to manage intraoperative VA injury and choose optimal alternative fixation becomes a concern of spinal surgeons. In this study, the management strategy for a patient with suspected intraoperative VA injury was analyzed. A 53-year-old woman developed type II odontoid fracture and brain stem injury due to a motor vehicle accident 3 months earlier. After conservative treatments, the brain stem injury improved, but with residual ocular motility defect in the right eye. The odontoid fracture did not achieve fusion with displacement and absorption of fracture fragments. After admission, atlantoaxial fixation using bilateral C1-2 transarticular screws (TASs) combined with C1 laminar hooks was planed. The first TAS was inserted successfully. Unfortunately, suspected VA injury developed during tapping the tract for the second TAS. Considering the previous brain stem injury and that directly inserting the screw to tamponade the hemorrhage might cause VA stenosis or occlusion, we blocked the screw trajectory with bone wax. C2 laminar screw was implanted instead of intended TAS on the injured side. The management strategy for suspected VA injury should depend on intraoperative circumstances and be tailored to patients. Blocking screw trajectory with bone wax is a useful method to stop bleeding. Atlantoaxial fixation using C2 laminar screw and C1-2 TAS combined with C1 laminar hooks is an ideal alternative procedure.     

Modification of Wright's technique for placement of bilateral crossing C2 translaminar screws: technical note

BACKGROUND CONTEXT: Several relatively new screw techniques have been described that rigidly capture the posterior elements of C2. The previously described procedures of axis fixation are technically demanding and place the vertebral artery at some risk. A novel and less technically demanding technique of obtaining C-2 translaminar screws has been recently described. Although the risk of vertebral artery injury has been essentially eliminated, the authors recognize that neurologic injury from breakthrough of the inner cortex of the lamina by the drill or screw is still a possibility. PURPOSE: Describe and illustrate a modified C2 translaminar technique and review the results of patients who have undergone the surgery. The current modification of the C2 translaminar screw technique was designed to reduce the risk of inadvertent screw placement within the spinal canal. STUDY DESIGN/SETTING: A techniques paper combined with a retrospective clinical review of patients undergoing the surgery. PATIENT SAMPLE: Patients undergoing posterior instrumented fusion surgery of the cervical spine, which incorporates C2 posterior elements using the translaminar technique. OUTCOME MEASURES: Radiographic analysis of the fusion construct incorporating the C2 translaminar screws. METHODS: We have modified the previously described technique of C-2 translaminar screw placement with the addition of "exit" cortical windows to assure bicortical, intralaminar screw placement. RESULTS: The results of the first six patients with an average follow-up of 12 months demonstrated this method to be safe and effective in fixating the axis. CONCLUSIONS: We have made a simple modification of Wright's elegant technique with the addition of "exit" windows at the facet-laminar junctions. This gives us the assurance that the C2 screw has not entered the spinal canal by directly visualizing the tip of the screw exiting the outer cortices of the lamina before leaving the operating room.     

Translaminar screw fixation in the lumbar spine: technique, indications, results

Translaminar screw fixation of the lumbar spine represents a simple and effective technique for short segment fusion in the degenerative spine. Clinical experience with 173 patients who underwent translaminar screw fixation revealed a fusion rate of 94%. The indications for translaminar screw fixation as a primary fixation procedure are: segmental dysfunction, lumbar spinal stenosis with painful degenerative changes, segmental revision surgery after discectomies, and painful disc-related syndromes such as internal disc disruption and lumbar disc herniation with concomitant degenerative changes. As an additional stabilization procedure, translaminar screws can be used to augment anterior fusion or reinforce pedicle systems. Translaminar screw fixation achieves as high fusion rate provided the biomechanical principles of the lumbar spine with an intact anterior column are respected and a meticulous operative technique is employed to enhance bony ingrowth of the graft. Received: 12 January 1998 Revised: 18 March 1998 Accepted: 6 April 1998     

Laminar screw fixation of the axis

OBJECT: Laminar fixation of the axis with crossing bilateral screws has been shown to provide rigid fixation with a theoretically decreased risk of vertebral artery damage compared with C1-2 transarticular screw fixation and C-2 pedicle screw fixation. Some studies, however, have shown restricted rigidity of such screws compared with C-2 pedicle screws, and others note that anatomical variability exists within the posterior elements of the axis that may have an impact on successful placement. To elucidate the clinical impact of such screws, the authors report their experience in placing C-2 laminar screws in adult patients over a 2-year period, with emphasis on clinical outcome and technical placement. METHODS: Sixteen adult patients with cervical instability underwent posterior cervical and cervicothoracic fusion procedures at our institution with constructs involving C-2 laminar screws. Eleven patients were men and 5 were women, and they ranged in age from 28 to 84 years (mean 57 years). The reasons for fusion were degenerative disease (9 patients) and treatment of trauma (7 patients). In 14 patients (87.5%) standard translaminar screws were placed, and in 2 (12.5%) an ipsilateral trajectory was used. All patients underwent preoperative radiological evaluation of the cervical spine, including computed tomography scanning with multiplanar reconstruction to assess the posterior anatomy of C-2. Anatomical restrictions for placement of standard translaminar screws included a deeply furrowed spinous process and/or an underdeveloped midline posterior ring of the axis. In these cases, screws were placed into the corresponding lamina from the ipsilateral side, allowing bilateral screws to be oriented in a more parallel, as opposed to perpendicular, plane. All patients were followed for >2 years to record rates of fusion, instrumentation failure, and other complications. RESULTS: Thirty-two screws were placed without neurological or vascular complications. The mean follow-up duration was 27.3 months. Complications included 2 revisions, one for pseudarthrosis and the other for screw pullout, and 3 postoperative infections. CONCLUSIONS: Placement of laminar screws into the axis from the standard crossing approach or via an ipsilateral trajectory may allow a safe, effective, and durable means of including the axis in posterior cervical and cervicothoracic fusion procedures.     

Posterior C1-C2 fusion with polyaxial screw and rod fixation.

STUDY DESIGN: A novel technique of atlantoaxial stabilization using individual fixation of the C1 lateral mass and the C2 pedicle with minipolyaxial screws and rods is described. In addition, the initial results of this technique on 37 patients are described. OBJECTIVES: To describe the technique and the initial clinical and radiographic results for posterior C1-C2 fixation with a new implant system. SUMMARY OF BACKGROUND DATA: Stabilization of the atlantoaxial complex is a challenging procedure because of the unique anatomy of this region. Fixation by transarticular screws combined with posterior wiring and structural bone grafting leads to excellent fusion rates. The technique is technically demanding and has a potential risk of injury to the vertebral artery. In addition, this procedure cannot be used in the presence of fixed subluxation of C1 on C2 and in the case of an aberrant path of the vertebral artery. To address these limitations, a new technique of C1-C2 fixation has been developed: bilateral insertion of polyaxial-head screws in the lateral mass of C1 and through the pars interarticularis into the pedicle of C2, followed by a fluoroscopically controlled reduction maneuver and rod fixation. METHODS: After posterior exposure of the C1-C2 complex, the 3.5-mm polyaxial screws are inserted in the lateral masses of C1. Two polyaxial screws are then inserted into the pars interarticularis of C2. Drilling is guided by anatomic landmarks and fluoroscopy. If necessary, reduction of C1 onto C2 can be accomplished by manipulation of the implants, followed by fixation to the 3-mm rod. For definitive fusion, cancellous bone can be added. No structural bone graft or wiring is required. In selected cases, e.g., C1-C2 subluxation or fractures in young patients in whom only temporary fixation is necessary, the instrumentation can be removed after an appropriate time. Because the joint surfaces stay intact, the patient can regain motion in the C1-C2 joints. RESULTS: Thirty-seven patients underwent this procedure. No neural or vascular damage related to this technique has been observed. The early clinical and radiologic follow-up data indicate solid fusion in all patients. CONCLUSION: Fixation of the atlantoaxial complex using polyaxial-head screws and rods seems to be a reliable technique and should be considered an efficient alternative to the previously reported techniques.     

Complications of pedicle screws in lumbar and lumbosacral fusions in 105 consecutive primary operations

Pedicle screw fixation is technically demanding and associated with high complication rates. The aim of this study was to identify and quantify the pedicle screw-related complications in 105 consecutive operations. We retrospectively analysed 105 consecutive primary operations. We found complications of varying severity in 54% of the patients. Deep infections were found in 4.7%, all successfully cured by debridement and antibiotics. There were no permanent neurological complications related to the screws. One serious neurological sequela, a T10 paraplegia, was unrelated to screw placement between L3 and S1. Screw misplacement was found in 6.5% of the screws. Screw breakage occurred in 12.4% of the patients, inevitably leading to loss of correction. Reduced spondylolisthesis L5-S1 without anterior support was found to be especially prone to screw breakage. The study confirmed that pedicle screw placement is a technically demanding procedure with a high complication rate. Fortunately, most complications are not severe. Infections can be dealt with by thorough debridement and parenteral antibiotics. Neurological sequelae can be minimised by careful tactile technique. To avoid screw breakage and subsequent loss of correction, anterior support should be provided, through either posterior or anterior lumbar interbody fusion (PLIF or ALIF) techniques, in reduced spondylolisthesis L5-S1.     

Atlantoaxial stabilization with the use of C1-3 lateral mass screw fixation. Technical note

Atlantoaxial stabilization has evolved from simple posterior wiring to transarticular screw fixation. In some patients, however, the course of the vertebral artery (VA) through the axis varies, and therefore transarticular screw placement is not always feasible. For these patients, the authors have developed a novel method of atlantoaxial stabilization that does not require axial screws. In this paper, they describe the use of this technique in the first 10 cases. Ten consecutive patients underwent the combined C1-3 lateral mass-sublaminar axis cable fixation technique. The mean age of the patients was 62.6 years (range 23-84 years). There were six men and four women. Eight patients were treated after traumatic atlantoaxial instability developed (four had remote trauma and previous nonunion), whereas in the other two atlantoaxial instability was caused by arthritic degeneration. All had VA anatomy unsuitable to traditional transarticular screw fixation. There were no intraoperative complications in any of the patients. Postoperative computed tomography studies demonstrated excellent screw positioning in each patient. Nine patients were treated postoperatively with the aid of a rigid cervical orthosis. The remaining patient was treated using a halo fixation device. One patient died of respiratory failure 2 months after surgery. Follow-up data (mean follow-up duration 13.1 months) were available for seven of the remaining nine patients and demonstrated a stable construct with fusion in each patient. The authors present an effective alternative method in which C1-3 lateral mass screw fixation is used to treat patients with unfavorable anatomy for atlantoaxial transarticular screw fixation. In this series of 10 patients, the method was a safe and effective way to provide stabilization in these anatomically difficult patients.     

Pseudarthrosis and techniques for fixation to the pelvis

For adult patients undergoing spinal deformity correction surgery, it is unclear if fusion should routinely end at L5 or S1. Adding to this controversy is the concern for the development of a pseudarthrosis at L5–S1 with attempted fusions caudal to long constructs, which remains a challenging problem. There are a number of different constructs that have been used to stabilize the lumbosacral junction. Pelvic fixation into the ilium, whether by iliac screws or alar–iliac screws, provides rigid lumbosacral fixation that generally results in the lowest pseudarthrosis rates with adult deformity constructs. The addition of L5–S1 interbody fusion, either TLIF or ALIF, should be considered requisite if the most distal fixation points are S1 or S2 screws. Newer techniques, such as transsacral axial interbody fusion, may offer an alternative to open L5–S1 interbody fusion, though data are limited to case series. Perhaps most important is for deformity surgeons to consider, in concert, spinal alignment parameters, host biology, and adequate surgical fixation in order to minimize the likelihood of lumbosacral pseudarthrosis.     

Die direkte Verschraubung von Frakturen des Dens axis

The results of anterior screw fixation of odontoid fractures in 28 patients are presented. There were 27 type II- and 1 type III-injuries. Non-union with persistent instability had to be notified in one patient (3.6 %), secondary posterior C1/2 fusion had to be performed. Incorrect positioning of the screws in the odontoid with penetration of the postero-lateral cortex occurred in 3 patients (10.7 %). Malpositioning of the odontoid after screw fixation was documented in 5 cases (17.9 %). Cardiopulmonary complications had to be treated in 5 patients (17.9 %), 4 patients (14.3 %) died in the postoperative period. 17 patients could be followed up. Only 3 patients (17.8 %) were free of symptoms. A significant limitation in ROM of axial rotation was seen in 44 % of the patients. With anterior screw fixation of the odontoid high fusion rates can be achieved, however the procedure is technically demanding. Regarding the functional outcome, there is no significant difference to other established treatment methods.     

Placement of C2 laminar screws using three-dimensional fluoroscopy-based image guidance

The use of C2 laminar screws in posterior cervical fusion is a relatively new technique that provides rigid fixation of the axis with minimal risk to the vertebral artery. The techniques of C2 laminar screw placement described in the literature rely solely on anatomical landmarks to guide screw insertion. The authors report on their experience with placement of C2 laminar screws using three-dimensional (3D) fluoroscopy-based image-guidance in eight patients undergoing posterior cervical fusion. Overall, fifteen C2 laminar screws were placed. There were no complications in any of the patients. Average follow-up was 10 months (range 3–14 months). Postoperative computed tomographic (CT) scanning was available for seven patients allowing evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. The intraoperative planning function of the image-guided system allowed for 4-mm diameter screws to be placed in all cases. Using modified Odom’s criteria, excellent or good relief of preoperative symptoms was noted in all patients at final follow-up. Eric W. Nottmeier, MD is a paid consultant for BrainLAB.     

The radiological outcome of lumbar spinal fusion using a South African-developed dynamic spinal fixation system.

OBJECTIVES: To investigate the radiological outcome of the use of a new Cape Town-developed spinal fixation system. DESIGN: One hundred and fifty-five patients underwent posterior lumbar spinal fusions with this fixation system and autogenous bone graft more than a year ago. Of these 121 were available for radiological follow-up. SETTING: Spinal pedicle fixation systems are in common use in spinal fusion surgery. Most systems use rigid screws with a high rate of implant failure. In South Africa most spinal implants are imported and expensive, and this prompted the development of a locally manufactured dynamic spinal fixation system with the aim of producing a cheaper and more effective system with a lower risk of implant failure. OUTCOME MEASURES: A visual assessment of 1-year post-surgery radiographs by a qualified independent observer looking particularly at the rate of fusion and the incidence of implant failure. RESULTS: Bone fusion rates were comparable to all other pedicle fixation systems but implant failure rates were considerably less than in systems using rigid screws and more comparable to a similar dynamic spinal fixation system. CONCLUSIONS: This spinal fixation system is safe and effective in aiding bone fusion. It has a low rate of implant failure and is currently cheaper than all imported spinal fixation systems. It has therefore achieved the objectives that prompted its inception.     

Comparison of the anatomic risk for vertebral artery injury associated with percutaneous atlantoaxial anterior and posterior transarticular screws

Background contextAs a minimally invasive spine surgery, percutaneous atlantoaxial fixation techniques using anterior transarticular screw (ATS) and posterior transarticular screw (PTS) have promising clinical results. However, transarticular screw fixation is technically demanding and carries a potential risk of iatrogenic vertebral artery (VA) injury. There were no available data comparing the anatomic risk of VA injury associated with these screws.PurposeTo evaluate the trajectories of percutaneous atlantoaxial ATS and PTS through three-dimensional (3D) computerized tomography.Study designTo compare the anatomic risk of VA injury between percutaneous ATS and PTS.Patient sampleSixty patients ranged in age from 19 to 75 years (mean, 45.08 years) and included 35 men and 25 women.Outcome measuresImage measurement of C2 isthmus height and C2 isthmus width and the distance between the medial-most superior articular facet to the medial-most edge of the VA groove of the C2 (D).MethodsSixty consecutive patients (in total) with lower cervical lesions were evaluated through 3D images reconstructed by a rapid 3D system. The maximum possible diameters of the percutaneous atlantoaxial ATS and PTS trajectories were compared and examined. Mean, range, and standard deviations for each type of screw, for left and right trajectories, and for men and women were calculated from 120 percutaneous atlantoaxial ATS and PTS measurements through SPSS.ResultsThe maximum mean diameter differed significantly between the trajectories of 120 percutaneous atlantoaxial ATS and PTS. For screw trajectories ≤3.5 mm in diameter, 19.2% of the PTS trajectories were judged as risky, whereas all the anterior ones were judged as safe.ConclusionsFrom an anatomic perspective, percutaneous ATS fixation poses less anatomic risk of VA injury than percutaneous PTS fixation. As an alternative surgical therapy for atlantoaxial subluxation, percutaneous ATS fixation may play a more important role in the future.     

The effect of bone quality on the stability of ankle arthrodesis. A finite element study

BACKGROUND: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. METHODS: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. RESULTS: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. CONCLUSIONS: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. CLINICAL RELEVANCE. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.     

Cervical pedicle screw guiding jig,an innovative solution

Pedicle screws are one the commonest used modality in spinal instrumentation. However, the method of pedicle screw fixation in cervical spine as compared to thoracic and lumbar spine is still technically demanding because it carries the risk of catastrophic damage to the surrounding neurovascular structures We have utilized virtual planning and 3D (3-dimension) printing to develop a patient specific jig to guide the accurate placement of pedicle screws. A patient with bifacetal dislocation C7 over D1 classified as flexion-distraction injury type 3 who was planned for decompression and fusion by posterior instrumentation at C6, C7, D1 and D2 was selected. A CT scan with 1?mm cuts was used to produce DICOM images of the same. Using these DICOM images virtual planning was done on MIMICS and 3 MATICS software to create patient specific jigs. These jigs were then 3D printed using a 3D printer and used for accurate placement of pedicle screws intra-operatively after adequate sterilization. Our procedure is low cost but high technology based. It is simple, accurate, and very cost effective. The technology transfer is very easy and can be adopted easily.     

Chiari I malformation associated with ventral compression and instability: one-stage posterior decompression and fusion with a new instrumentation technique

OBJECTIVE AND IMPORTANCE: We describe an alternative surgical technique for treatment of Chiari I malformation associated with ventral compression and instability of the region. An expansive suboccipital cranioplasty and a rigid occipitocervical fixation are performed in one stage. METHODS: The occipitocervical fixation is performed by use of metal rods fixed on the cranial side by screws inserted into the diploic layer of occipital bone and on the caudal side by screws inserted into the pedicle of the axis or in a transarticular fashion into the lateral masses of axis and atlas vertebra. A large piece of autologous bone is placed in the region between the rostral edge of cranial decompression and the axis, with the aim of achieving both expansive suboccipital cranioplasty and occipitocervical fusion. RESULTS: We performed this procedure in two patients with Chiari I malformation associated with basilar invagination and occipitalization of the atlas. Postoperatively, decompression of the brainstem and restoration of normal cerebrospinal fluid flow at the craniovertebral junction were confirmed radiologically, and the patients were relieved of their symptoms. At 1 and 3 years of follow-up, respectively, solid bone fusion was observed between the occipital bone and axis in both patients. CONCLUSION: Simultaneous posterior decompression and occipitocervical fixation with an alternative instrumentation technique is discussed. The procedure can be performed regardless of the size of suboccipital craniectomy. Screw insertion into the diploic layer of the occipital bone has not been described previously.     

Plate and screw fixation for atlanto-axial subluxation

Summary Our experience with 30 cases of atlanto-axial dislocation, over the period of 3 years and 9 months, is described. A modified plate and screw method of fixation of the lateral masses of the atlas and axis was successfully used in these cases. The technical aspects and merits of the method, wherein a 100% union rate was achieved, with no morbidity, mortality, or instrument fatigue or failure, are presented. The average follow-up period is of 19 months. The technique provided immediate rigid segmental internal fixation, permitting early mobilization with minimal external support. Onlay and interfacetal bone grafts subsequently produced bony fusion. Direct application of screws to the atlas and axis, thus utilizing the firm purchase in their thick and large cortico-cancellous lateral mass, provides a biomechanically strong fixation of the region.Occipito-cervical fusion can be achieved in selected cases by a modification of the method. It appears that such a method of fixation could be useful at least in some complex congenital or traumatic craniovertebral region instability where the conventional methods have failed or are not suitable.     

Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation.

BACKGROUND CONTEXT: A relatively high pseudarthrosis rate is associated with multilevel anterior cervical discectomy and fusion (ACDF). Anterior plate fixation increases fusion rate in multilevel ACDF. A debate still exists between the effectiveness of allograft versus autograft in plated multilevel ACDF. PURPOSE: To determine the efficacy of allograft versus autograft in fusion rate and clinical outcome in patients undergoing two- and three-level ACDFs with rigid anterior plate fixation. STUDY DESIGN: A retrospective radiographic and clinical review to assess fusion, risk factors and clinical outcome of 80 consecutive patients who underwent ACDF with rigid anterior plate fixation involving two and three levels with either allograft or autograft. PATIENT SAMPLE: There were 45 patients (56%) who had autogenous iliac crest tricortical grafts and 35 patients (44%) who received tricortical allograft with an average age of 49 years who were treated by multilevel ACDF with rigid anterior plate fixation at a single institution. Thirty-three Peak polyaxial (Depuy-Acromed, Rayham, MA), 26 Orion (Sofamor-Danek, Memphis, TN), 16 Atlantis (Sofamor-Danek, Memphis, TN) and 5 Synthes (Paoli, PA) anterior cervical plating systems were used. All patients underwent ACDF (61 two-level, 19 three-level) by a Smith Robinson technique. All patients had burring of the end plates, 2-mm distraction of the motion segment and graft countersunk 2 mm from the anterior vertebral border. Anterior cervical plate with unicortical screw purchase was used in all cases. Segmental screw fixation was performed in 46 patients. Soft collars were worn postoperatively for 3 to 4 weeks. OUTCOME MEASURES: Follow-up lateral neutral, flexion and extension radiographs were used to assess fusion. The radiographs were reviewed by an independent blinded observer in assessing fusion grades between autograft versus allograft. Clinical outcomes were rated excellent, good, fair and poor based on Odom's criteria. METHODS: Fusion rate and postoperative clinical outcome were assessed in 80 patients who underwent two- or three-level ACDF with rigid anterior plate fixation. Additional risk factors were also analyzed. RESULTS: Radiographic fusion was assessed in all patients (mean, 16 months). Seventy-eight patients (97.5%) achieved solid arthrodesis. Pseudarthrosis occurred in two patients who had allograft for two-level and three-level fusions. Nonsegmental screws were used in the two-level nonunion case. Postoperative dysphagia developed in one two-level nonunion patient, and revision surgery was performed in the other nonunion three-level patient. Twenty-three patients were smokers, and 26 patients had work-related injuries. Clinical outcome (mean, 20 months) was excellent in 23, good in 48 and fair in 9 patients. No statistical significance was noted between demographics, history of tobacco use, graft-type, end plate preparation technique, intermediate segmental screws, plate-type, clinical outcome of fused and nonfused patients and presence of work-related injuries (p>.05). CONCLUSIONS: A high fusion rate of 97.5% was obtained for multilevel ACDF with rigid plating with either autograft or allograft. In this study, nonunion occurred in patients with allograft but this difference was not statistically significant. Fusion was obtained in 97.8% of patients with segmental screw fixation and 97.1% with nonsegmental screw fixation. Nonsegmental screw fixation may contribute to less than adequate stability and contribute to a higher rate of nonunion, but such effects could not be discerned from this study. Excellent and good clinical outcome was noted in 88.8% of the patients. Proper patient selection and meticulous operative technique is essential to obtain high fusion rates and optimal clinical outcome, which is more important than graft type.     

Safety of atlantoaxial fusion using laminar and transarticular screws combined with an atlas hook in a patient with unilateral vertebral artery occlusion (case report)

Objective and importance  A disadvantage of transarticular and C2 pedicle screws is vertebral artery (VA) injury as a result of screw misplacement. If unilateral occlusion of the VA is present, VA injury of the dominant side will cause fatal complications as a result of collateral flow insufficiency. Several authors have recently reported the usefulness of C2 laminar screws because of their safety on VA injury. We used transarticular and C2 laminar screws combined with the atlas hook in a patient with C1-2 instability and unilateral VA occlusion, in order to reduce the risk of further VA injury. Clinical presentation  A 64-year-old woman with rheumatoid atlantoaxial subluxation complained of cervical myelopathy and neck pain. Preoperative MR angiography showed a left side VA occlusion. Technique  The patient underwent atlantoaxial, posterior fusion using a transarticular screw on the side of the occlusion and a C2 laminar screw on the dominant side combined with a bilateral atlas hook. The transarticular screw was inserted using a navigation system and image intensifier, and the laminar screw was inserted free hand. Bone grafting from the iliac crest was performed. Conclusion  Transarticular and C2 laminar screws fixation combined with the atlas hook in a patient with unilateral VA occlusion is a useful technique, in order to reduce the risk of further VA injury.