Occipitocervical Joint Research Articles

Evaluation of the Bone Union Occurring Subsequent to C1-2 Fusion Combined With C1 Laminectomy for the Surgical Treatment of Retro-Odontoid Pseudotumor.

Introduction Surgical treatments for retro-odontoid pseudotumors (ROPs) include C1 laminectomies and C1-2 and occipitocervical (OC) fusions. When a C1 laminectomy is combined with a C1-2 fusion, concerns arise regarding an increased risk of pseudarthrosis due to decreased bone grafting space. Extension of the fusion area to the OC region may be considered to ensure an adequate bone graft bed. However, this procedure is associated with a risk of complications. Thus, in this study, we investigated the bone fusion and clinical outcomes of C1-2 fusion combined with a C1 laminectomy. Methods Between January 2017 and December 2022, seven patients with ROPs who had undergone C1-2 fusion combined with a C1 laminectomy were included in the study. All patients were followed up for >1 year. Bone fusion was evaluated by computed tomography (CT) at one year postoperatively, while implant failure was assessed by radiography at the final follow-up. Clinical evaluations included preoperative and one-year postoperative Japanese Orthopaedic Association (JOA) scores and recovery rates. Results This study included five male and two female patients, with an average age of 71.9 years. The average follow-up duration was 3.3 years. The primary anchor choices included the C1 lateral mass screw and the C2 pedicle screw. In one case, the transarticular screw was utilized unilaterally, and in another case, a lamina screw was utilized unilaterally. One year postoperatively, CT revealed bone fusion in three of the seven patients. Fusion occurred at the lateral and median atlantoaxial joints in two cases and one case, respectively. Screw loosening was observed in one case. None of the patients required reoperations. The average JOA recovery rate was 34.6%. Conclusion This surgical technique is useful for stabilizing and decompressing the C1-2 region while preserving mobility at the OC joint. However, further long-term follow-up studies are required.

The impact of suboccipital muscle inhibition on postural stability in young individuals

Introduction. Postural stability is the result of cooperation between the musculoskeletal and nervous systems. The stability of standing posture ensures the spatial arrangement of the body, where the center of gravity falls within the center of the support base. FHT (Forward Head Posture) increases the extension in the occipito-cervical joint and upper cervical spine, deepening the flexion of the lower cervical segment, causing improper contraction of the suboccipital muscles. Disorders in the tone of the suboccipital muscles may affect the balance. Objective. The research hypothesis was made that a single 4-minute suboccipital muscle inhibition procedure influences the change in postural stability values with open and closed eyes in individuals with cranio vertebral angle (CVA) within the normal range and below. Materials and Methods. Healthy participants (10 women and 8 men) with an age of 22.7 ± 0.58. The participants took part in the study. They were classified into research groups based on the CVA angle assessment. Postural stability analysis used the Koordynacja stabilometric platform. Measurements were taken with open and closed eyes, before and immediately after suboccipital muscle inhibition. Results. The suboccipital muscle inhibition was observed to affect anterior-posterior (A-P) displacements in group A (CVA < 50) p-value = 0.0168, with no significant impact in group B (CVA ≥ 50), p-value = 0.3695. Conclusion. A single 4-minute suboccipital muscle inhibition procedure does not significantly influence postural stability parameters in the examined groups, except for A-P displacements with open eyes in the CVA < 50 group.

Social Media Devices' Influence on User Neck Pain during the COVID-19 Pandemic: Collaborating Vertebral-GLCM Extracted Features with a Decision Tree.

The prevalence of neck pain, a chronic musculoskeletal disease, has significantly increased due to the uncontrollable use of social media (SM) devices. The use of SM devices by younger generations increased enormously during the COVID-19 pandemic, being-in some cases-the only possibility for maintaining interpersonal, social, and friendship relationships. This study aimed to predict the occurrence of neck pain and its correlation with the intensive use of SM devices. It is based on nine quantitative parameters extracted from the retrospective X-ray images. The three parameters related to angle_1 (i.e., the angle between the global horizontal and the vector pointing from C7 vertebra to the occipito-cervical joint), angle_2 (i.e., the angle between the global horizontal and the vector pointing from C1 vertebra to the occipito-cervical joint), and the area between them were measured from the shape of the neck vertebrae, while the rest of the parameters were extracted from the images using the gray-level co-occurrence matrix (GLCM). In addition, the users' ages and the duration of the SM usage (H.mean) were also considered. The decision tree (DT) machine-learning algorithm was employed to predict the abnormal cases (painful subjects) against the normal ones (no pain). The results showed that angle_1, area, and the image contrast significantly increased statistically with the time of SM-device usage, precisely in the range of 2 to 9 h. The DT showed a promising result demonstrated by classification accuracy and F1-scores of 94% and 0.95, respectively. Our findings confirmed that the objectively detected parameters, which elucidate the negative impacts of SM-device usage on neck pain, can be predicted by DT machine learning.

Assessing Complications of Occipitocervical Joint Fusion at Rural vs Urban Hospitals in the US

Assessing Complications of Occipitocervical Joint Fusion at Rural vs Urban Hospitals in the US

Unilateral atlanto-occipital injury: A case series and detailed radiographic description.

ContextAtlanto-occipital dissociation is a highly lethal ligamentous injury at the craniocervical junction (CCJ). Previous studies have described rare cases of milder forms of atlanto-occipital injury (AOI) which might be managed nonoperatively, but there is a paucity of literature on this subject.Aims:We retrospectively reviewed our institutional experience to characterize the injury patterns, treatments, and clinical courses of patients with unilateral AOI.Methods:We included patients with radiographic evidence of unilateral occipitocervical joint capsular disruption, distraction, or edema ± injury of the apical ligament, tectorial membrane, anterior atlanto-occipital membrane, posterior atlanto-occipital membrane, alar ligaments, or cruciate ligament. The long-term outcomes were gathered from medical records, and six patients were available for Neck Disability Index via phone call at the time of the study.Results:Eight patients were included in the study. The mean age was 45.1 years ± 26.5. Causes of trauma included motor vehicle collision for five patients (5/8, 62.5%), falls for two (2/8, 25), and assault for one (1/8, 12.5%). All patients had a widened condyle-C1 interval >2 mm. Three patients underwent occipitocervical fusion, one patient underwent atlantoaxial fusion, and another received subaxial fusions for other injuries. Three patients underwent no surgical intervention. All patients were seen at least once as an outpatient following hospital discharge. There were no delayed neurologic injuries or deaths.Conclusions:We propose that ligamentous injury at the CCJ functions more as a spectrum rather than dichotomous diagnosis, of which a subset can likely be safely managed nonoperatively.

Simplifying the Surgical Classification and Approach to the Posterolateral Skull Base and Jugular Foramen Using Anatomical Triangles.

IntroductionLesions of the jugular foramen (JF) and postero-lateral skull base are difficult to expose and exhibit complex neurovascular relationships. Given their rarity and the increasing use of radiosurgery, neurosurgeons are becoming less experienced with their surgical management. Anatomical factors are crucial in designing the approach to achieve a maximal safe resection.Methods and methodsSix cadaveric heads (12 sides) were dissected via combined post-auricular infralabyrinthine and distal transcervical approach with additional anterior transstyloid and posterior far lateral exposures. Contiguous surgical triangles were measured, and contents were analyzed. Thirty-one patients (32 lesions) were treated surgically between 2000 and 2016 through different variations of the retro-auricular distal cervical transtemporal approaches.ResultsWe anatomically reviewed the carotid, stylodigastric, jugular, condylar, suboccipital, deep condylar, mastoid, suprajugular, suprahypoglossal (infrajugular), and infrahypoglossal triangles. Tumors included glomus jugulare, lower cranial nerve schwannomas or neurofibromas, meningiomas, chondrosarcoma, adenocystic carcinoma, plasmacytoma of the occipitocervical joint, and a sarcoid lesion. We classified tumors into extracranial, intradural, intraosseous, and dumbbell-shaped, and analyzed the approach selection for each.ConclusionJugular foramen and posterolateral skull base lesions can be safely resected through a retro-auricular distal cervical lateral skull base approach, which is customizable to anatomical location and tumor extension by tailoring the involved osteo-muscular triangles.

The timing of fusion surgery for clival chordoma with occipito-cervical joint instability: before or after tumor resection?

Clival chordoma with occipito-cervical (OC) joint invasion can result in preoperative and postoperative instability. The authors investigate the appropriate timing of OC fusion to prevent instability-, fusion-, and surgery time-related morbidity. Twenty-two consecutive patients underwent surgery for clival chordoma from December 2008 to September 2014. OC fusion was performed for patients with OC joint invasion and instability due to preoperative destruction of the occipital condyle or extensive postoperative condylectomy. The data in relation to OC joint instability, fusion, and surgery time were analyzed retrospectively and compared between OC fusion before and after tumor resection. Of the 22 patients, 8 with tumor invasion of the OC joint underwent OC fusion. OC fusion was performed after tumor resection in one-stage for four patients and before tumor resection in two-stage for four patients. There was OC joint instability from tumor destruction of the occipital condyle in seven patients (87.5%). Patients with OC fusion after tumor resection encountered complications such as surgery site wound dehiscence, encephalitis, and cardiac arrest with consequent mortality in one patient. These complications were avoided in subsequent patients where OC fusion was performed before tumor resection. There were no differences in the extent of tumor resection between OC fusion before and after tumor resection. Two-stage OC fusion before tumor resection can reduce instability-, fusion-, and surgery time-related morbidity and achieve feasible tumor resection when OC joint instability is expected. The extent of tumor invasion and brain stem compression should be considered when fusion precedes tumor resection.

Atlas instrumentation guided by the medial edge of the posterior arch: An anatomic and radiologic study.

Study Design:This was an interventional human cadaver study and radiological study.Objectives:Atlas instrumentation is frequently involved in fusion procedures involving the craniocervical junction area. Identification of the entry point at the center of atlas lateral mass (ALM) is challenging because of its rounded posterior surface and the surrounding venous plexus. This report examines using the medial edge of atlas posterior arch (MEC1) as a fixed and reliable anatomic reference to guide the entry point of ALM screws.Methods:Fifty, normal, cervical spine computed tomography studies were reviewed. ALM screw trajectories were planned at one point along MEC1 and another point 2 mm lateral to MEC1. Free-hand ALM instrumentation was performed in ten fresh human cadavers using the 2 mm entry point, with a sagittal trajectory parallel to atlas inferior arch (IAC1); three-dimensional imaging was then performed to confirm instrumentation accuracy.Results:The average ALM diameter was 12.35 mm. Inserting a screw using the entry point 2 mm lateral to MEC1 was closer to ALM midpoint than using the entry point along MEC1 (P < 0.0001). Twenty ALM screws were successfully inserted in the ten cadavers. No encroachments into the spinal canal or foramen transversarium occurred. However, two screws were superiorly directed and violated the occipitocervical joint; they were not parallel to IAC1.Conclusion:MEC1 provides a fixed and reliable landmark for ALM instrumentation. An entry point 2 mm point lateral to MEC1 is close to ALM midpoint. IAC1 also provides a guide for the sagittal trajectory. Attention to anatomic landmarks may help reduce complications associated with atlas instrumentation but should be verified in future clinical studies.

A Method to Prevent Occipitocervical Joint Violation Using Plain Radiography During Percutaneous Anterior Transarticular Screw Fixation.

A prospective study of anterior transarticular screw (ATS) fixation patients. To develop a method to determine screw tip position through plain radiography after percutaneous ATS fixation to prevent occipitocervical joint (OCJ) violation. No studies using plain radiography to prevent OCJ violation during percutaneous ATS fixation have been performed. In total, 34 subjects (with 68 screws) who had undergone percutaneous ATS fixation were enrolled. To evaluate the screw tip location in relation to the C1 lateral mass (LM), the screw tip positions were graded 1, 2, or 3 on anteroposterior (AP) radiographs, and I, II, or III on lateral radiographs. OCJ violation was analyzed by postoperative computed tomography (CT). Screws with tips located lower (tip I) in the LM did not result in OCJ violation. Only one tip in the tip 3 position showed OCJ perforation, and this screw was also located in tip III. Screw perforation rates of tip 1-tip II, tip 1-tip III, and tip 2-tip III were the highest (100%), followed by tip 2-tip II (10.5%) and tip3-tip III (10%). This study provides insights into OCJ violation during percutaneous ATS fixation. According to AP radiography, a percutaneous ATS with the screw tip located in the lateral part of the LM resulted in a lower rate of OCJ perforation, whereas screws located in the medial LM resulted in the highest rate of perforation. Percutaneous ATS with the screw tip located in the neutral part of the LM should ensure that the screw tip is below the upper part of the LM, preventing OCJ violation. These findings may help surgeons assess screw positioning both during and after the operation. 3.

Craniovertebral junction 360°: A combined microscopic and endoscopic anatomical study.

Objectives:Craniovertebral junction (CVJ) can be approached from various corridors depending on the location and extent of disease. A three-dimensional understanding of anatomy of CVJ is paramount for safe surgery in this region. Aim of this cadaveric study is to elucidate combined microscopic and endoscopic anatomy of critical neurovascular structures in this area in relation to bony and muscular landmarks.Materials and Methods:Eight fresh-frozen cadaveric heads injected with color silicon were used for this study. A stepwise dissection was done from anterior, posterior, and lateral sides with reference to bony and muscular landmarks. Anterior approach was done endonasal endoscopically. Posterior and lateral approaches were done with a microscope. In two specimens, both anterior and posterior approaches were done to delineate the course of vertebral artery and lower cranial nerves from ventral and dorsal aspects.Results:CVJ can be accessed through three corridors, namely, anterior, posterior, and lateral. Access to clivus, foreman magnum, occipital cervical joint, odontoid, and atlantoaxial joint was studied anteriorly with an endoscope. Superior and inferior clival lines, supracondylar groove, hypoglossal canal, arch of atlas and body of axis, and occipitocervical joint act as useful bony landmarks whereas longus capitis and rectus capitis anterior are related muscles to this approach. In posterior approach, spinous process of axis, arch of atlas, C2 ganglion, and transverse process of atlas and axis are bony landmarks. Rectus capitis posterior major, superior oblique, inferior oblique, and rectus capitis lateralis (RCLa) are muscles related to this approach. Occipital condyles, transverse process of atlas, and jugular tubercle are main bony landmarks in lateral corridor whereas RCLa and posterior belly of digastric muscle are the main muscular landmarks.Conclusion:With advances in endoscopic and microscopic techniques, access to lesions and bony anomalies around CVJ is becoming easier and straightforward. A combination of microscopic and endoscopic techniques is more useful to understand this anatomy and may aid in the development of future combined approaches.

Stabilization of the craniocervical junction after an internal dislocation injury: an in vitro study

Background contextReconstructive surgeries at the occipitocervical (OC) junction have been studied in treating degenerative conditions. There is a paucity of data for optimal fixation for a traumatically unstable OC joint. In clinical OC dislocations, segmental fixation may be impossible because of vertebral artery injury or fracture. Segmental fixation of the occiput, C1, and C2 demonstrated maximum biomechanical stability in fixation of an unstable craniocervical dislocation. A biomechanical study comparing various points of cervical posterior screw fixation after recreating traumatic injury would illuminate relative advantages between the various techniques. PurposeTo determine the rigidity lost, if any, of segmental C0–C2 posterior screw fixation versus fixation skipping C1 at the OC junction, with or without a cross-connector. Study designThis study is a cadaveric biomechanical investigation. MethodsIntervertebral motions and translations were recorded in seven specimens under conditions in the following order: intact, OC dislocation model with complete disruption of the cruciate ligaments, alar ligaments, and occipitoatlantal/atlantoaxial capsules (injury), segmental posterior fixation (SPF) with posterior instrumentation (ELLIPSE; Globus Medical, Inc., Audubon, PA, USA) at occiput, C1, and C2 levels, endpoint fixation (EPF) with posterior instrumentation at occiput and C1 level skipping C1, and endpoint fixation with a cross-connector (EPFC). Motion was applied through a custom spine simulator with a pure moment load of 2.5 Nm and measured with motion capture markers attached to occiput (C0), anterior C1 ring, and C2. Flexion-extension (FE), lateral bending (LB), axial rotation (AR), and cranial-caudal (CC) motions were recorded in terms of C0–C2. Results were reported as a percentage of injured motion (injury=100%), unless otherwise stated. ResultsThe injury significantly increased the motion to 165%, 263%, and 130%, during FE, LB, and AR, respectively, of intact. The CC translations increased to 164%, 254%, and 121% during FE, LB, AR, respectively, of intact. Segmental posterior fixation significantly reduced motion to 7%, 8%, and 1%, during FE, LB, and AR, respectively, of injury. Endpoint fixation significantly increased motion in FE, resulting in 12%, 6%, and 4% during FE, LB, and AR, respectively, of injury when compared with SPF. The EPFC construct decreased the motion compared with its counterpart to 8.6%, 5.7%, and 3.2% during FE, LB, and AR, respectively. ConclusionsAll fixation constructs significantly reduced motion in all loading modes and CC translations, compared with intact and injury. The construct with the greatest stability against craniocervical dislocation included SPF with instrumentation at the occiput, C1, and C2. By skipping C1 using the EPF, FE and cephalad-caudal translations significantly increased compared with posterior fixation at every level. The addition of a cross-connector increased the stability but was not statistically significant.

Traumatic atlanto-occipital dislocation in children.

Although once considered an invariably fatal injury, improvements in diagnosis and management have made atlanto-occipital dislocation (AOD) a survivable injury. MRI is the preferred imaging modality; occasionally, flexion/extension/distraction fluoroscopy may be required to determine craniovertebral stability. Early surgical stabilization is recommended for all children with AOD. Early occipitocervical fusion using screws in combination with a rod or plate, or sublaminar wires with a contoured rod, coupled with autograft bone, provide immediate stabilization and a high fusion rate. Halo immobilization and traction are contraindicated in the management of AOD in children because of the risk of displacement of the injured occipitocervical joint. Postoperative hydrocephalus is frequent and should be suspected when neurologic decline occurs after fixation. Nearly half of children who survive AOD will have residual neurologic deficits.

Delayed diagnosis of post-traumatic C7 vertebra anterior subluxation with an unusual neurological pattern: a case report

IntroductionPost-traumatic subluxations are potentially devastating injuries to the axial skeleton. Of utmost priority are an expedient and timely diagnosis and realignment because of its association with spinal cord and nerve root trauma, which lead to progressive deleterious neurological deficits. A good radiological study of the occipitocervical joint and first thoracic vertebra is key to a successful early diagnosis. However, cases might still fail to be diagnosed, leading to trouble. A case of post-traumatic subluxation at the C7 vertebral level with an unusual neurological pattern is presented here.Case presentationA 35-year-old farmer from the Sindh province of Pakistan presented to our neurology department after a fall 2 months earlier and complained of lower limb pain and difficulty in walking. He had numbness in both of his lower limbs up to his umbilical region, with sparing of bladder function along with intact strength in the upper extremities bilaterally.ConclusionsOur case highlights the unusual sparing of upper limbs and intact urinary continence with severe lower limb deficits in a 70% subluxation. Our case is unusual because highly detrimental effects such as quadriplegia are expected with such extreme subluxation, but our patient presented with only lower limb deficits. This case serves as a reminder to emergency medicine doctors, spine surgeons, and even radiologists (a) to evaluate spine injuries by using computed tomography in trauma patients to identify artifact around a suspected injury and (b) to be mindful of negative conventional radiographs.

Occipitocervical Reconstruction Through Direct Lateral and Posterior Approach for the Treatment of Primary Osteosarcoma in the Atlas

Case report. To report a new surgical technique of the primary cervical osteosarcoma in the atlas. Primary osteosarcoma of the atlas is extremely rare. This is the first report that describes a surgical treatment of the primary osteosarcoma in the atlas. Resection of an osteosarcoma in the atlas is very difficult because of the complex and important anatomic structures that surround it, and secure reconstruction of the atlas is difficult as well. A 48-year-old man was referred to our institute with a 10-month history of a palpable painful mass on the right posterior neck. His neck mass was diagnosed as chondroblastic osteosarcoma by open bone biopsy. The plain radiograph of the lateral cervical spine revealed the osteoblastic lesion of the vertebra and an extraosseous mass formation from the C1 to C3 vertebrae. Computed tomography of the cervical spine revealed approximately a 7 × 3 × 7 cm-sized extraosseous calcified mass that originated from the right lateral mass of the atlas. The magnetic resonance imaging of the cervical spine did not show any spinal cord compression. The patient underwent excision of this tumor using the direct lateral approach and reconstruction of the lateral mass of the atlas. On gross examination of the mass, there was a reactive thin membrane ("pseudomembrane") between soft tissue and tumor. At 3 months after surgery, the computed tomographic scan showed the solid fusion state of the occipitocervical joint. He rarely complained of any problems except for mild limitation of neck motion. We report a rare case of complete excision of an osteosarcoma of the C1 lateral mass in our patient via a direct lateral and posterior approach to secure additional fixation of occipitocervical joint. We describe our technique for reconstructing the lateral mass of the atlas. This reconstruction technique will also be applicable to other resection surgeries involving the occipitocervical junction.

Comprehensive computed tomography assessment of the upper cervical anatomy: what is normal?

Background context High-speed computed tomography (CT) exams have replaced traditional radiographs for assessment of cervical spine injuries in many emergency departments. Recent evidence demonstrates that even subtle displacements can indicate significant upper cervical spine injuries. Many different anatomical measurements have been described in the upper cervical spine to date, most of them based on X-ray. The range of anatomical relationships that exist in an uninjured population must be known to reliably detect abnormal relations. The measurements with the lowest normal variation are likely to be most useful in detecting injuries. Purpose The purpose of this study was to describe the normal quantitative anatomical relationships as well as the threshold measurements most likely to detect injury in the upper cervical spine. Study design/Setting Retrospective anatomical case review. Patient sample Seventy-six thin-sliced cervical CT scans randomly selected from a trauma population, all negative for injury in the cervical spine. Methods Forty-two different anatomical measurements were made of the upper cervical spine. These included traditional historical measurements and other detailed dimensions to characterize occipitocervical (OC) and atlantoaxial (AA) joint relationships. Results After review of all the anatomical measurements performed in the upper cervical spine, direct measurements of the joint space had the least variation. The mean OC joint space was 0.6 mm, with an upper 95% confidence interval (CI) of 1 mm at the most anterior or posterior aspects of the joints. This was true for both sagittal and coronal measurements. The mean AA joint space was 0.6 mm, with an upper 95% CI of 1.2 mm at the lateral aspect of the joint on the coronal image only. The midsagittal structures demonstrated significantly higher standard deviation and variability. Conclusions These results revealed consistently narrow joint spaces and left-right symmetry in the upper cervical spine joints that do not vary according to demographics. There was distinctly greater consistency in the coronal plane, which enabled more precise diagnostic measurement and side-to-side comparison of measurements. This precision will enable more accurate identification of abnormal scans, which should prompt consideration for additional workup. Thus, better understanding of these relationships may enable earlier detection of subtle craniocervical dissociative injuries based on CT scan data. This is important, because the only evidence of a severe injury on CT can be subtle misalignment.

Evaluation of Occipitocervical Subluxation in Rheumatoid Arthritis Patients, Using Coronal-View Reconstructive Computed Tomography

Reconstructive computed tomography (CT) study of occipito-atlanto and atlantoaxial joints in RA patients. The occipitocervical region is one of the most common sites of rheumatoid arthritis (RA). Although lateral radiography has been used for the diagnosis of atlantoaxial subluxation and vertical subluxation, reconstructive CT imaging of the occipito-atlanto and atlantoaxial joints is more sensitive in detecting morphologic changes in this region. We investigated this region in RA patients, using coronal-view reconstructive CT images, and examined the relationship between the morphology and other radiographic parameters. The occipitocervical region was examined in 58 female RA patients by reconstructive CT, plain radiography, and MRI. The degree of destructive change on reconstructive CT was compared to that on other radiographic evaluations. Coronal-view reconstructive CT revealed primary destructive changes before detection by lateral radiography, using Redlund-Johnell or Ranawat values. A Redlund-Johnell value less than 34 mm was diagnostic for occipitocervical subluxation in female RA patients. Coronal-view reconstructive CT is useful for the diagnosis of occipitocervical joint subluxation in RA.

The Feasibility of Microscope-Assisted “Free-Hand” C1 Lateral Mass Screw Insertion Without Fluoroscopy

Retrospective study. To determine if C1 lateral mass screws could be safely inserted without the use of fluoroscopy. Standard surgical technique for C1 lateral mass screw placement uses intraoperative fluoroscopy. However, intraoperative fluoroscopy is time consuming, cumbersome, and exposes both the patient and surgical team to radiation. Radiographic analysis and chart review. Surgical technique was analyzed in 3 components: feasibility to complete the screw insertion without intraoperative fluoroscopic guidance; occurrence of any intraoperative, perioperative complications; and radiologic assessment of screw positions on roentgenogram. Forty-six C1 lateral mass screws were inserted in 24 consecutive patients who underwent posterior cervical fusion. There were 19 female and 5 male. The mean age was 63 +/- 18 years at the time of surgery. All C1 lateral mass screws were inserted unicortically using a microscope-assisted "free-hand" technique. The average intraoperative blood loss in C1-C2 fusion was 123 +/- 50 mL. The mean operative time for each C1-C2 fusion was 133 +/- 30 minutes. Satisfactory positions of C1 screws were noted in intraoperative and postoperative radiograph examinations. There was no mortality or wound infection. There was no cortical breach along the screw path palpated intraoperatively. No vertebral artery injury or cerebral spinal fluid leakage during the screw insertion was observed. However, one patient with a prior posterior cervical operation had a dural tear during the exposure, another had new occipital neuralgia, and a third patient had a symptomatic occipitocervical joint violation by a C1 screw, which was diagnosed only on computed tomography scans. The symptoms resolved after the C1 screws were removed. Microscope-assisted "free-hand" C1 lateral mass screws insertion is a feasible and reproducible technique. which offers an alternative method of screw insertion without cumbersome and potentially harmful fluoroscopy.

Morphometric and qualitative analysis of congenital occipitocervical instability in children: implications for patients with Down syndrome

Congenital occipitocervical (OC) instability is uncommon in healthy children but can occur in many children with Down syndrome. A simple morphometric method of evaluating the OC joint in children with OC instability is presented, supported by a qualitative image analysis based on computed tomography (CT). Thin-cut CT scans of the OC joint were obtained in eight patients with Down syndrome and one patient with congenital OC instability. These patients' CT scans were compared with those of 15 healthy age-matched control individuals. Morphometric analysis was performed by measuring the depth and length of the superior articular surface (SAS) of C-1, and these values were normalized for a comparison between groups. Qualitative data were acquired using a surface-rendering technique for a visual comparison of the C-1 SAS. Morphometric analysis demonstrated an absence of the concave C-1 SAS anatomy in patients with congenital OC instability compared with age-matched control individuals (0.083 compared with 0.202, p < 0.001). Three-dimensional (3D) image analysis of the C-l SAS supported this finding. Congenital differences in the shape of the OC joint are highly associated with atraumatic OC instability in children with Down syndrome. High-resolution CT imaging combined with 3D rendering techniques and surface mapping provides support for this assessment. It appears that abnormal OC joint shape is a contributing factor to congenital OC instability, especially in patients with Down syndrome.

Subluxación C6-C7 y la importancia de la radiología simple en el Servicio de Urgencias. A propósito de un caso y revisión de la literatura

Post-traumatic fractures and luxations of the cervical spine are commonest in young patients. A good basic radiological study of the region between the occipitocervical joint and the first thoracic vertebra is essential. The antialgic spasm which causes the shoulders to be raised means that their image is superimposed on that of the cervico-dorsal vertebrae hiding the latter. Suitable technical measures should be taken for X-ray images of this area. If these are not satisfactory, computerized tomography (CT) or magnetic resonance (MR) are indicated. We present the case of a twenty year old woman who presented after cervical hyperextension due to a road traffic accident. She had been attended in the Emergency Department of another hospital, where she went complaining of bilateral cervicobrachial pain. Plain antero-posterior and lateral X-rays were done showing as far as C6. The patient was discharged on analgesics and muscle relaxants. Her symptoms did not improve so she was sent for rehabilitation. Even so, she became paraplegic three months later. On MR subluxation of C6-C7, an extradural intraspinal space-occupying lesion and osteolysis of C7 were seen. An emergency operation was done. The C7 vertebra was removed together with a very vascular mass. Histological study showed that it was a giant cell tumour. Subsequently, the patient recovered movement of her legs and radiotherapy was started.