C1-C2 Complex Research Articles

STRANGULATION-INDUCED ATLANTOAXIAL ROTATORY SUBLUXATION TREATED WITH CLOSED REDUCTION

BackgroundCervical subluxation is a broad class of injuries in which there are degrees of misalignment of vertebral bodies in relationship to adjacent vertebra. Atlantoaxial rotatory subluxation (AARS) is a subtype of cervical subluxation resulting from exaggerated rotation of the C1–C2 complex. Inflammatory, infectious, post-surgical, and traumatic etiologies are recognized and well-described. AARS is predominantly seen in children and occurs rarely in adults. Case ReportWe submit the case of an otherwise healthy adult male patient presenting to the emergency department with strangulation-induced C1–C2 subluxation with a rotational component that was treated at the bedside by neurosurgery with closed reduction. Why Should an Emergency Physician Be Aware of This? Clinicians must consider a broad range of serious pathologies in a patient presenting with torticollis, especially in the setting of strangulation. Although extremely rare in adults, AARS must be considered in the differential diagnosis, as early identification increases the likelihood of successful nonoperative treatment.

Use of Intraoperative Imaging to Preserve C1-C2 Mobility in Complex Atlas-Hangman Fractures.

Combination fractures of the C1-C2 complex especially atlas and hangman are relatively uncommon and management usually compromises C1-C2 mobility. To evaluate the treatment of combined C1- hangman's fracture with and without intraoperative O- arm based navigation system, and its outcome in terms of preserving C1-C2 mobility. This was a case series of patients with combined C1 and hangman's fracture, managed at a tertiary care hospital during February 2009 to December 2016. Neurological function assessed with American Spine Injury Association (ASIA) impairment scale. Radiological fusion of the operated segment assessed with computed tomographic scan, criteria used for successful fusion included formation of callus across the fracture. Preservation of rotational motion between C1 and C2 was assessed by cervical flexion rotation (CFR) test. We included 10 patients (male/female: 9/1; mean 47.7 ± 17.5 years) in our study. Operative intervention was performed in 9 patients. We used intraoperative computed tomogram (CT) scan with navigation in 5 patients. The mean follow-up period was 28.7 months (range 6 to 70 months). Neurological recovery occurred in all 4 patients with preoperative neurological deficits. Radiological fusion occurred in all cases. Rotation at C1-2 was preserved in all 5 cases operated under O-arm guidance and in one patient with type 1 fracture who was managed conservatively. The goals in treating these complex fractures are to achieve early maximum stability and preserving maximum range of motion. These are often competing phenomena, which can be achieved by using intra operative CT scan and navigation system.

Posterior Temporary C1-2 Pedicle Screws Fixation for the Treatment of Unstable C1-2 Complex Fractures: Minimum of 2-Year Follow-Up.

Retrospective. To present rarely reported complex fractures of the upper cervical spine (C1-C2) and discuss the clinical results of the posterior temporary C1-2 pedicle screws fixation for C1-C2 stabilization. A total of 19 patients were included in the study (18 males and 1 female). Their age ranged from 23 to 66 years (mean age of 39.6 years). The patients were diagnosed with complex fractures of the atlas and the axis of the upper cervical spine and underwent posterior temporary C1-2 pedicle screws fixation. The patients underwent a serial postoperative clinical examination at approximately 3, 6, 9 months, and annually thereafter. The neck disability index (NDI) and the range of neck rotary motion were used to evaluate the postoperative clinical efficacy of the patients. The average operation time and blood loss were 110 ± 25 min and 50 ± 12 ml, respectively. The mean follow-up was 38 ± 11 months (range 22 to 60 months). The neck rotary motion before removal, immediately after removal, and the last follow-up were 68.7 ± 7.1°, 115.1 ± 11.7°, and 149.3 ± 8.9° (P < 0.01). The NDI scores before and after the operation were 42.7 ± 4.3, 11.1 ± 4.0 (P < 0.01), and the NDI score 2 days after the internal fixation was removed was 7.3 ± 2.9, which was better than immediately after the operation (P < 0.01), and 2 years after the internal fixation was removed. The NDI score was 2.0 ± 0.8, which was significantly better than 2 days after the internal fixation was taken out (P < 0.001). Posterior temporary screw fixation is a good alternative surgical treatment for unstable C1-C2 complex fractures.

Endonasal Odontoidectomy in Basilar Invagination.

Objective The endoscopic endonasal odontoidectomy (EEO) is emerging as a feasible surgical alternative to conventional microscopic transoral approach. In this article, we show EEO in the basilar invagination (BI) and describe in detail the technical aspects, advantages, and disadvantages of this approach ( Fig. 1 ). Methods We describe EEO using audiovisual material from the neurosurgical department of Hospital Universitari i Politècnic La Fe Valencia database. Results We present the case of a 61-year-old male patient with BI. Initially, we performed suboccipital decompression and occipitocervical fusion. Subsequently, after a no significant neurological improvement and persistent anterior compression, EEO was performed. The postoperative evolution was uneventful and the preoperative neurological deficits were recovered rapidly after surgery Discussion EEO technique enables complete odontoid resection, preventing invasion of aggressive oral bacterial flora, and it is not limited by the mouth opening. As well, it avoids manipulation of the soft palate, therefore evades the risk of velopalatal insufficiency, facilitates immediate oral tolerance, and early extubation. The rostral position of C1–C2 complex in BI could suppose a great advantage in favor the endonasal approaches. Mucoperichondrial vascularized flaps could be obtained to avoid a postoperative cerebrospinal fluid (CSF) leak and facilitate the reepithelization process of the surgical bed. Conclusion EEO may provide a significant anatomic and technical advantage over the trans-oral approach. The link to the video can be found at: https://youtu.be/Td6MDcjCNKk .

Traumatic Atlantoaxial Dislocation with Type II Odontoid Fractures: A Case Report

Odontoid fracture frequently ensues after a cervical trauma, and most commonly at the junction between the dens and the body (type II odontoid fracture). This report is focused on a 24-years-old male patient with right-sided hemiparesis, resulting from traumatic atlantoaxial dislocation with type II odontoid fracture. Cervical CT-scanning showed a spondylolisthesis of the C1-C2 complex with type II odontoid fracture, and the injury was treated using posterior reduction and internal stabilization. Therefore, hemiparesis was reduced, and during the follow-up period, our patients were disease-free. Early diagnosis and the appropriate management of atlantoaxial trauma is a possible approach towards preventing severe neurological deficits.

Radiological and surgical anatomy of ventral c1-c2 complex

To evaluate anatomical data of the bony structures during exploration of the C1-C2 complex. This study included six formalin-fixed cadaveric head and neck specimens. Radiological images and anatomical measurements included: C1-C2 distance, bony distance between C1 anterior tubercle-nares and superior incisors, height of C1 anterior arch, and height and width of odontoid articular surface. The mean distance between C1 anterior tubercle-nares and superior incisors on maxilla were 96.16 ± 8.07 mm and 84.14 ± 9.16 mm, respectively. The mean height of C1 anterior arch was 13.89 mm. The meandistance between medial borders of right-left C1 lateral masses was 19.10 ± 1.80 mm. The mean distance between medial border of lateral midline on mass right and left sides were 9.43 ± 0.88 mm and 9.68 ± 0.97 mm, respectively. The mean height of C1 anterior arch at midline was 13.89 ± 2.48 mm, and the mean distance between ventral surface of anterior arch and ventral joint of odontoid at midline was 6.43 ± 1.29 mm. The anteroposterior, horizontal diameters of odontoid on its base were 12.12 ± 0.38 mm, and 11.12 ± 0.94 mm, respectively. The angles of transoral and transnasal approaches to C1 were 32.67 ± 4.59° and 32.00 ± 2.10°, respectively. A safe transoral or transnasal odontoidectomy requires accurate measurements and imaging regarding ventral C1-C2 relationships, distances of odontoid, lateral mass and midline.

Article Commentary: “Spontaneous Ankylosis of Occiput to C2 following Closed Traction and Halo Treatment of Atlantoaxial Rotary Fixation”

The authors present a unique case of an 11-year-old child with spontaneous fusion of his occiput to C1–C2 following traction, manipulative reduction, and halo immobilization for refractory atlantoaxial rotatory fixation. The child initially presented with torticollis, neck pain, and headaches and underwent numerous chiropractor manipulations over 9 months with alleviation of his neck pain and headaches. However, his torticollis persisted; thus, he was referred to an orthopedic surgeon where initial workup included magnetic resonance imaging, magnetic resonance angiography, and computed tomography (CT) imaging. This revealed a Fielding and Hawkins type II rotatory fixation, with remodeling changes involving the left C2 articular facet. The treatment options of surgical versus nonsurgical reduction were discussed with the family, and they decided for nonsurgical reduction and immobilization. Thus, the child was placed in traction and had improvement but not complete resolution of his rotational deformity. Subsequently, an attempt was made to preserve the traction reduction with halo vest immobilization for 3 months. At his 6-month follow-up, the patient demonstrated mild residual torticollis. CT imaging was obtained to provide further clarity on bony anatomy and showed spontaneous fusion from the occiput to C2. Because most of the head and neck rotation occurs at the occiput–C1–C2 integrated functional complex, it is desirable to try to preserve the motion levels around the craniocervical junction as much as possible. Therefore, nonsurgical management is the clearly recommended first line of treatment using halter-type traction and reduction followed by Minerva or halo bracing for 3 months. However, if reduction is not achieved and/or there is persistent atlantoaxial rotatory fixation after 3 months of bracing, surgical reduction and internal fixation fusion for management is the recommended treatment with the hope of limiting the surgical reduction and fusion efforts to the C1–C2 segments. In a retrospective case review, we found instability patterns following nonoperative care of very young children with ligamentous injuries involving the craniocervical junction to be unpredictable with spontaneous ossification not a regular occurrence.1 I agree with the authors' management of this child and would have recommended a similar approach even with the child's very delayed presentation.2 I suspect that the child had extension of his fusion from occiput to the atlantoaxial motion segments secondary to the recurrent trauma of the craniocervical articular surfaces and surrounding soft tissues over the course of numerous chiropractor neck manipulations and/or prolonged traction periods, which eventually led to focal joint inflammation and subsequent spontaneous fusion. Based on our previous surgical experience in operating on the craniocervical junction of the very young patient, surgical reduction and fusion targeting the atlantoaxial segment would not have predictably prevented extension of the fusion to the occipitocranial junction. However, with the advent of innovative magnetic resonance imaging, one may be able to predict who will have extension of the fusion by highlighting increased signal of the occiput–C1–C2 complex ligaments. For example, Landi et al found increased signal in the alar, capsular, and transverse ligaments in two patients with Fielding and Hawkins type II rotatory fixation using short T1 inversion recovery (STIR) sequences.3 Overall, the management of refractory atlantoaxial rotatory fixation in children remains challenging and frustrating. The one remedy in absence of a decisive evidence-based treatment is to clearly present all treatment options to the patient and their family to invite a shared decision-making approach for outcomes like the occurrence of a spontaneous fusion.

Transoral Decompression and Posterior Stabilization in Fixed Anterior Pathology of the Craniocervical Junction

Introduction Management of the anterior compressive pathology of the craniovertebral junction (CVJ) is complex and demanding. We review our experience with the transoral surgical decompression of fixed anterior CVJ lesions, with particular attention to the decision making and to the indication for a consecutive stabilization. Patients and Methods Retrospective study (2000–2013) of 47 consecutive patients (14 males and 13 females). Mean age was 59.2 years (range, 32–82 years). Encountered lesions were rheumatoid arthritis with pannus (29, 9 of which with associated cranial settling), ankylosing spondylitis (four), tumors (seven: six extradural chordomas/chondrosarcomas and one metastasis), odontoid fractures with hypoporosis, and rotational instability (seven). Patients presented with a variety of following symptoms: high cervical pain (82%), varying degrees of quadriparesis (64%), lower cranial nerve deficits (23%), and central cord syndrome with neurogenic bladder (14%). All patients underwent one-stage transoral decompression and consecutive posterior atlantoaxial or occipitocervical stabilization. Clinical evaluation was made pre- and postoperatively using the Ranawat score. Follow-up period ranged between 6 and 48 months (average, 22 months). Results According to the Ranawat score, we had 21 grade I patients, in 20 of which pain was eradicated, 10 grade II patients, 8 of which passed to grade I, 11 grade IIIA patients, of which 6 passed to grade I and 5 to grade II, and 5 grade IIIB patients of which 4 passed to grade IIIA. In seven patients, the transarticular screws crossed the anterior cortex of the atlas, without clinical manifestations. In five patients, complete reduction of the C1–C2 rotation was not possible, because of the chronic nature of the defect. Surgical morbidity occurred in five cases (three dural tears and two occipital wound infections). There were two perioperative deaths ([a] dural rupture, pneumoencephaly, meningitis, and massive pulmonary embolism, [b] pulmonary infection, and cardiorespiratory arrest). Conclusion Successful and stable decompression of the CVJ requires extensive preoperative evaluation, appropriate tailoring, and adequate expertise. The transarticular C1–C2 fixation is a safe and effective stabilization method when the atlanto-occipital joints remain competent. Complications appear mostly in patients with rotational deformity of the C1–C2 complex. Patients with clinical and radiological findings of myelopathy improve less even if surgery is successful.

Odontoid process fractures: the role of the ligaments in maintaining stability. A biomechanical, cadaveric study.

Aims: We wished to investigate the role of the cervical ligaments in maintaining atlantoaxial stability after fracture of the odontoid process. Methods: We dissected eight fresh-frozen cadaveric cervical spines to prepare the C1 and C2 vertebrae for biomechanical analysis. The C1 and C2 blocks were mounted and biomechanical analysis was performed to test the stability of the C1-C2 complex after cutting the odontoid process to create an Anderson and D’Alonzo type II fracture then successive division of the atlantoaxial ligaments. Biomechanical analysis of stiffness, expressed as Young’s modulus, was performed under right rotation, left rotation and anterior displacement. Results: The mean Young’s modulus in anterior displacement decreased by 37% when the odontoid process was fractured (p = 0.038, 95% confidence interval 0.04–1.07). The mean Young’s modulus in anterior displacement decreased proportionally (compared to the previous dissection) by the following percentages when the structures were divided: facet joint capsules (bilateral) 16%, ligamentum flavum 27%, anterior longitudinal ligament 10%. These differences did not reach statistical significance (p > 0.05). Discussion: We have found that the odontoid process itself may account for up to 37% of the stiffness of the C1-C2 complex and that soft tissue structures account for further resistance to movement. We suggest magnetic resonance imaging (MRI) of the soft tissues in the acute setting of a minimally displaced odontoid process fracture to plan management of the injury. If the MRI determines that there is associated ligament injury it is likely that the fracture is unstable and we would suggest operative management.

Applied anatomy of a minimally invasive muscle-splitting approach to posterior C1–C2 fusion: an anatomical feasibility study

To describe the applied anatomy of a minimally invasive muscle-splitting approach used to reach the posterior aspect of the C1-C2 complex. Atlantoaxial fusion using a midline posterior approach and polyaxial screw and rod system is widely used. Although minimally invasive variations of this technique have been recently reported, the complex applied anatomy of these approaches has not been described. The C1-C2 complex represents an unique challenge because of its bony and vascular anatomy. In this study, the applied anatomy and feasibility of this technique are examined on cadavers. The microsurgical anatomy of the upper cervical spine is examined on a formalin-fixed and on a fresh cadaver. The muscle-splitting approach is performed on 12 fresh cadavers using this technique. The minimally invasive muscle-splitting approach is described in detail. Relevant anatomy and bony landmarks that aid screw placement in C1 and C2 could be well visualized. Using this approach, we were able to reach the lateral mass of the atlas and the inferior articular process and pars interarticularis of the axis in all of the nine cadavers. We placed mini polyaxial screws in C1 lateral mass and C2 pars interarticularis in four cadavers according to the technique described by Harms and Melcher. Using this approach, it was possible to reach the posterior aspect of C1 and C2; the relevant anatomy needed to perform a C1-C2 fusion could be well visualized.

Novel Motion Preservation Device for Atlantoaxial Instability

An in vitro cadaveric biomechanical study. To evaluate the anteroposterior (A-P) stability and the flexibility of our novel motion preservation device (MPD) using cadaveric cervical spines. The MPD intended to restrict the A-P instability of the C1-C2 complex and to preserve the axial rotation, flexion, extension, and lateral bending was designed and produced. The stability and the flexibility of the MPD was evaluated. Ten embalmed cadaveric specimens were loaded with pure A-P translation force and the A-P translational distances were measured. Each specimen was tested for the following 4 models, respectively: Intact (control), the Dens-removed, the MPD instrumented, and a Rod fixation system instrumented. Fifteen specimens were loaded with pure moments (up to 1.5 Nm), and the C1-C2 range of motion (ROM) was measured for flexion, extension, lateral bending, and axial rotation using a stereophotogrammetry motion analysis system. Mean A-P translational distances were 4.26 mm in Intact, 13.1 in the Dens-removed, 5.42 in the MPD, and 2.58 in the Rod fixation. The distance values with the MPD had no significant difference compared with Intact. Mean C1-C2 ROM of Intact, the MPD, and the Rod fixation at 1.5 Nm were: 14.7, 6.96, and 2.11 degrees in flexion, 6.46, 4.72, and 2.84 degrees in extension, 3.29, 4.02, and 1.01 degrees in right lateral bending, 4.92, 4.58, and 1.84 degrees in left lateral bending, 26.4, 15.4, and 1.16 degrees in right axial rotation, and 25.6, 14.3, and 1.21 degrees in left axial rotation, respectively. The MPD restricted the A-P instability of the C1-C2 complex. In flexion, extension, and axial rotation, the C1-C2 ROM of the MPD was about 50% of the ROM in Intact, whereas equivalent to Intact in lateral bending.

Direct Posterior C1 Lateral Mass Screws Compression Reduction and Osteosynthesis in the Treatment of Unstable Jefferson Fractures

Technical case report. To investigate a new concept and surgical technique in the treatment of unstable Jefferson fractures, which preserves the motion of upper cervical spine, avoiding fusion. The management of unstable Jefferson fractures remains controversial. Conservative treatment usually involves a long time of immobilization in halo vest, whereas surgical intervention generally performs fusion, eliminating the range of motion of upper cervical spine. Two patients with unstable Jefferson fractures were surgically treated via direct posterior C1 lateral mass screws compression reduction and osteosynthesis technique, aiming at restoring the C0-C2 height and maintaining the vertical ligamentous tension for C0-C1-C2 complex stability despite the incompetent transverse ligament, achieving physiologic repair instead of traditional fusion. The clinical and radiographic results were documented. The postoperative CT showed that C1 lateral mass screws were well positioned. At 1-year follow-up, plain radiographs, and CT scan revealed no implant failure, good cervical alignment, and bony healing of the fractures; no C1-C2 instability was observed on the flexion-extension radiographs. The patients were completely pain-free, with full range of motion of the cervical spine. The ideal treatment of unstable Jefferson fractures is expected to preserve the function of C0-C1-C2. Unstable Jefferson fractures involve the concomitant failure of the vertical ligamentous tension because of the loss of C0-C2 height. Reduction of the displaced lateral masses to restore the C0-C2 height and maintain the ligamentous tension is the key to the surgery. Direct posterior C1 lateral mass screws compression reduction and osteosynthesis is a valid technique, avoiding fusion of upper cervical spine.

Is Rheumatoid Arthritis a Risk Factor for a High-Riding Vertebral Artery?

A retrospective comparative study on the morphologic characteristics of the axis in patients with or without rheumatoid arthritis (RA). To compare the morphologic risk of vertebral artery (VA) injury during atlantoaxial transarticular screw fixation between patients with or without RA. VA injury is a potentially serious complication during atlantoaxial transarticular screw fixation. Although this operation is frequently performed on RA patients, there have been few comparative studies on the morphologic risk of VA injury between RA and non-RA patients. A total of 107 three-dimensional computed tomography images of the cervical spine including the C1-C2 complex were evaluated. Forty-seven RA patients and 60 non-RA patients were included in the study. The maximum atlantoaxial transarticular screw diameter (MSD) that could be inserted without breaching the cortex was measured 3-dimensionally using a computer- assisted navigation system. A high-riding-VA carrier was defined as a patient with either MSD of 4 mm or less. In RA patients, the space available for the spinal cord in flexion (SAC in flexion), duration of disease, RA stage, and type of disease were examined. In the RA group, 45 of 94 MSDs (47.9%) were 4 mm or less, and 33 of 47 patients (70.2%) were high-riding-VA carriers. In the non-RA group, 11 of 120 MSDs (9.2%) were 4 mm or less, and 9 of 60 (15.0%) patients were high-riding-VA carriers. MSD, C3 A-P diameter, and the ratio of MSD to C3 A-P diameter were significantly smaller in the RA group than in the non-RA group. Multiple logistic regression analysis showed that SAC in flexion was a significant risk factor for a high-riding-VA carrier in the RA group. RA was a significant risk factor for the presence of a high-riding VA. When performing atlantoaxial transarticular screw fixation, particularly on RA patients, thorough preoperative evaluation of the bony architecture is of great importance to avoid inadvertent VA injury.

Osseous and vascular anatomical variations within the C1–C2 complex: a radiographical study using computed tomography angiography

One of the limiting factors of C1-C2 fixation is the location of the vertebral artery (VA). The authors sought to assess the potential variations in atlanto-axial VA anatomy using computed tomography angiography (CTA). Detailed measurements were made on digital images of 106 patients undergoing CTA at our institution (54 males, 52 females; mean age 56, range 20-86). Distances, diameters and angles of osseous and vascular elements of the atlanto-axial complex were measured. Optimal C1 and C2 screw trajectories demonstrated wide variations among patients. The size of the VA groove or foramen was not predictive of exact arterial location or size. The size, location and path of the VA cannot be precisely predicted by the appearance of osseous structures such as the transverse foramina and/or the VA groove. CTA provides additional information regarding the atlanto-axial complex, and should be considered as a useful adjunct in the preoperative evaluation of select patients.

Posterior atlantoaxial dislocation without odontoid fracture

We report a case of posterior atlantoaxial dislocation without a fracture of the odontoid in a 35-year-old woman. There have been nine reported cases of similar injury in the English literature. The integrity of the transverse ligament following posterior atlantoaxial dislocations has not been well documented in these reports. In the present case, MRI revealed an intact transverse ligament, which probably contributed to the stability of the C1-C2 complex following closed reduction.

Placement of C2 laminar screws using three-dimensional fluoroscopy-based image guidance by Eric W. Nottmeier and Andrew B. Foy

In their work colleagues Nottmeier and Foy present a retrospective series of eight patients treated with posterior C1–C2 fusion by laminar screws using three-dimensional fluoroscopy-based image guidance. They conclude from the results of their work that: “In this study, it has been shown that C2 laminar screws can be safely and accurately placed using 3D fluoroscopy-based image guidance. Advantages of this technology over traditional techniques include real-time 3D computerized feedback to the surgeon during placement, as well as the ability to size the screw to the patient’s anatomy using intraoperative computerized planning.” In the last decade, technology has advanced to the point where regular computer workstations are able to calculate in real-time the transformation matrices needed to determine the position of a camera-tracked object (in a surgical setting, typically a frame with fiducials) in relation to a camera-tracked reference base. By attaching the reference base to a patient and (surgical) instruments to camera-tracked objects, the workstation can calculate the respective positions/orientations and display their virtual interactions. When three-dimensional data sets representing the patient’s anatomy from modalities including CT/MRI/3D rotational X-ray imaging, are manipulated so that virtual and real reference bases are exactly aligned, surgical instruments and/or implants can be displayed on anatomical structures not visible for the surgeon intraoperatively. This is, in a nutshell, current “computer-assisted surgery” or “image-guided surgery”. Assuming that transformation matrix calculations are mathematical processes carried out with high fidelity and great reproducibility, imperfections in navigational accuracy must have other sources. Calibration errors in 3D fluoroscopy-based systems have, for example, been shown to account for approximately 1 mm accuracy in a phantom model [1]. In a more realistic cadaveric model, the accuracy of navigation deteriorated to approximately 2.5 mm, mainly due to bending of instruments and/or references during manipulation [2]. In clinical practice more inaccuracies can be introduced by occasional blocking of the camera field of view; inadvertently touching/hitting references and, especially, a nonrigid connection between the patient reference base and the actual surgical site. In the present study, the patient reference base was attached to a head clamp, which was, in turn, connected via pins to the patient’s skull while surgery was performed at the levels C1 and C2. This experimental setup represents quite a long chain of connections from the reference base to the surgical site with considerable opportunity for movement between the two extremes. This is without taking into account additional movements due to, for example, patient ventilation and direct manipulation of C1 and C2 by surgical instruments. Considering that the C0–C1–C2 complex is highly mobile, it came as a small surprise for this reviewer to find such accurate screw placement in the current study. As can be found in the article, the investigators did verify the image-guided technique (“After accuracy of navigation was confirmed by the surgeon ... ”). The interesting question that follows automatically is: “How?” Checking accuracy by probing the patient reference base with a navigated instrument and finding a perfectly matched position/orientation on the computer display does nothing for the flexibility/movement errors that may be present at the more distant surgical site. Most often, surgeons verify accuracy by a direct intraoperative view of the surgical site to see whether, for example, the proposed drill trajectory or planned screw length is in accordance to their own experience from conventional surgeries before moving on with navigation. This leads to the strange paradox that is really bugging contemporary image-guided procedures: the employment of a technique to enhance surgical accuracy requiring the surgeon’s intraoperative verification of its accuracy. The reluctance of surgeons to show complete faith in image guidance seems justified considering the errors demonstrated in accuracy studies. Using computer navigation without proper anatomical and surgical knowledge would be irresponsible. Armed with proper knowledge, however, navigation becomes largely superfluous since surgeons trust their surgical experience/skills and the direct intraoperative view over computer-generated images anytime, and adjust their actions accordingly. Which surgeon would happily volunteer when asked to perform a percutaneous procedure having to trust solely on information provided by any image-guided technique commercially available today? Until now, no large-scale long-term and properly controlled study has been published in the field of computer-assisted surgery that has convincingly showed any actual patient benefit when using image guidance. Lacking a control group and using a navigation technique susceptible to the aforementioned accuracy problems, the present study may, unfortunately, not be able to change this status.

Atlantoaxial Dislocation in a Child Secondary to a Displaced Chondrum Terminale

A mong children, cervical spinal injuries are rare. When they do occur, younger children sustain more upper cervical injuries than older children do1,2. The spinal anatomy of children (i.e., a disproportionately large head, wedge-shaped vertebrae, and horizontally oriented facets) is different than that of adults and offers little resistance to the high shear forces that predominate in falls and/or motor-vehicle accidents1-5. Fig. 1 Lateral radiograph of the cervical spine, made on the day of injury, demonstrating atlantoaxial dislocation. The tip of the odontoid process is not ossified at birth. The chondrum terminale is a cartilaginous epiphysis at its apex. Fusion of the terminale to the rest of the dens, if it happens at all, does not take place until a child is between ten and thirteen years of age. This physis is a potential weak spot at the C1-C2 junction. The transverse ligament is the horizontal portion of the cruciate ligament and is the most important ligamentous structure of the C1-C2 complex of the occiput. It is the primary and most crucial stabilizing component of all of the ligaments of the atlantoaxial complex, confining the odontoid process within the articular notch on the anterior arch of C1 and preventing anterior subluxation of C1 on C2. The transverse ligament lies just below the physis of the chondrum terminale. The nonelastic nature of the transverse ligament and its proximity to the physis of the chondrum terminale makes this area a potential site for pediatric cervical spinal injury. The following case outlines our hypothesis for a mechanism of injury that, to our knowledge, has not been reported previously. The family of our patient was informed that data concerning the case would be submitted for publication. Fig. 2-A T2-weighted sagittal magnetic resonance imaging scan of the upper portion of the …

C1 lateral mass screws for posterior segmental stabilization of the upper cervical spine and a new method of three-point rigid fixation of the C1-C2 complex

To describe our experience with C1 lateral mass screws as part of a construct for C1-2 stabilization and report an alternate method of C1-C2 complex three-point fixation. All patients that had at least one screw placed in the lateral mass of C1 as part of a construct for stabilization of the C1-C2 complex entered this study. In selected patients who had a higher chance of nonunion an alternate construct was used: transarticular C1-C2 screws combined with C1 lateral mass screws. Twenty-one C1 lateral mass screws were placed in 11 patients. In three patients the alternate construct was used. All patients had a demonstrable solid and stable fusion on follow-up. C1 lateral mass screws are safe and provide immediate stability. The use of C1-C2 transarticular screws combined with C1 lateral mass screws is a feasible and also an excellent alternative for a three-point fixation of the C1-C2 complex.

Long-term incidence of subaxial cervical spine instability following cervical arthrodesis surgery in patients with rheumatoid arthritis

Cervical spine deformities are well-known complications of RA. A 5- to 20-year follow-up of 51 consecutive rheumatoid patients who underwent posterior cervical arthrodesis is presented to evaluate the recurrence of instability and need for further surgery. We conducted a retrospective review of the clinical features of 11 men and 40 women with an established diagnosis of RA and associated cervical deformities who underwent cervical spine surgery at the Mayo Clinic (Rochester, MN) between 1979 and 1990. Their mean age was 61 +/- 10 years (SD), and their duration of RA averaged 21 +/- 8.9 years (SD). There were 22 patients who presented with myelopathy, 7 with radiculopathy, and 22 with instability/neck pain. There were 33 patients with AAS, 2 with SMO process into the foramen magnum, 8 with SAS, and 8 with combinations of these. Preoperative reduction was followed by decompression and fusion using wiring techniques and autologous bone graft. Postoperative halo orthosis was provided for at least 3 months. The mean follow-up was 8.3 +/- 6 years (SD). There were 31 patients (61%) who underwent atlantoaxial arthrodesis, 17 patients (33%) who underwent subaxial, and 3 patients (6%) who underwent occipitocervical arthrodesis. During follow-up, 39% (13/33) of patients with AAS developed nonsymptomatic (6) or symptomatic/unstable (7) SASs subsequent to C1-C2 fusion. The latter 7 patients (21%) subsequently required extension of their arthrodesis. Adjacent segment disease was most common at the C3-C4 interspace after atlantoaxial fusion in 62% (8/13). Among the 8 patients who underwent isolated cervical fusion for SAS, 1 patient (1/8, 12%) developed adjacent instability after a fall and required extension of the previous fusion. No secondary procedure was required for the 6 patients initially stabilized by C1-(C6-T1) fusions for combinations of AAS + SAS. None of the patients initially treated by C1-C2 arthrodesis for AAS progressed to SMO. The incidence of subaxial instability in patients with rheumatoid disease who underwent cervical arthrodesis may be higher than previously reported, indicating the need for continued follow-up in these patients. Adjacent segment disease may be most common at the C3-C4 level following atlantoaxial fusion. Early stabilization of the C1-C2 complex in the patients with AAS may potentially prevent progression of SMO.

Acute combination fracture of atlas and axis: “triple” anterior screw fixation in a 92-year-old man: Technical note

Background The combination of odontoid and bilateral transarticular C1-C2 anterior screw fixation is a recent addition in treating C1-type II odontoid fractures. When feasible, it ensures early maximal stability, even if it slightly reduces the mobility of C1-C2 complex. We report a case of combination atlas-type II odontoid fracture that occurred in a 92-year-old man. The instability was treated with odontoid screw fixation and anterior bilateral C1-C2 transarticular screw fixation in a single stage. The aim of the article is to describe the feasibility of “triple” anterior screw fixation in the presence of C1-type II odontoid fracture. Methods The diagnosis, treatment, and outcome of a 92-year-old patient with mild tetraparesis caused by C1-type II odontoid fracture were assessed. Results Cervical x-rays, computed tomographic scan, and magnetic resonance imaging demonstrated a fracture of posterior arch of C1, associated with type II odontoid fracture and with presumable damage of C1 transverse ligament. Magnetic resonance imaging also showed a high cervical centromedullary area slightly hyperintense in T1-weighted images. Treatment consisted of odontoid and bilateral C1-C2 transarticular screw fixation with single anterior approach. The admission neurologic conditions improved and the patient was early mobilized. Conclusions The authors suggest that in presence of C1-type II odontoid fracture, the triple anterior screw fixation has to be taken into account as salvage procedure, especially if other methods of stabilization failed or cannot be safely performed. This technique seems to be safety feasible also in old patients, as our report and the experience of others confirm.