Atlantoaxial disorders in rheumatoid arthritis associate with the destruction of peripheral and shoulder joints, and decreased bone mineral density

OBJECTIVE

To evaluate whether cervical spine changes are associated with the destruction of shoulder or peripheral joints and with bone mineral density (BMD) in patients with long-term RA.

METHODS

An inception cohort of 67 patients with seropositive and erosive RA were followed up for 20 years. Cervical spine, shoulder, hand and foot radiographs, and the BMD of the lumbar spine and femoral neck were evaluated.

RESULTS

A positive relationship was detected between the occurrence of atlantoaxial disorders and the destruction of both shoulder (p < 0.001) and peripheral (p = 0.001) joints. In addition, the severity of anterior atlantoaxial subluxation and atlantoaxial impaction positively correlated with the grade of destruction in the evaluated joints. Furthermore, patients with atlantoaxial disorders presented decreased BMD of the femoral neck (p = 0.019). The occurrences of subaxial subluxations (SAS) and subaxial disc space narrowings only associated with higher onset age of RA.

CONCLUSIONS

Patients with severe RA and osteoporosis have an increased risk for atlantoaxial disorders. The co-existence of shoulder destruction and cervical spine disorders makes the differential diagnosis of shoulder and neck pain challenging.

Dorntherapy: its effect on electroencephalographic activity in tinnitus patients with craniocervical dysfunction

Dorntherapy was developed in the 1980s by Dieter Dorn, a nonmedical person, to cure his and his family members' vertebral problems. This technique achieves correction of dysfunctions of the vertebrae and joints simply by using natural movements of arms and legs or by applying gentle pressure (thumb) to the spinous process. Various observations suggest that craniocervical dysfunction can lead to tinnitus, thus causing changes in the electroencephalographic patterns. This study demonstrates that the successful application of Dorntherapy induced prominent changes of the electroencephalographic activity. Data analysis revealed a significant increase in the power of the alpha (8-13 Hz) and the alpha2 (9-11 Hz). Besides electrophysiological effects, changes in the quality of tinnitus and in the intensity of the tinnitus were noted. These results suggest that Dorntherapy must be an integral part of any tinnitus therapy.

[Post-traumatic unilateral atlanto-axial rotatory subluxation in an adult]

This retrospective single-patient case report deals with a rare form of spinal trauma, i.e. atlantoaxial rotatory subluxation. The authors present a review of the literature including a classification of rotatory atlantoaxial subluxation types proposed by Fielding, and describe their own experience with treatment of this condition. A case is reported of a 29-year-old woman with a history of head contusion in a car accident. Immediately after the trauma she had the following symptoms: torticollis and neck pain with decreased cervical motion. Atlantoaxial rotatory subluxation of the right C1-C2 articulation was diagnosed by plain radiographs and CT. The patient was treated surgically by an open reduction, unilateral screw fixation of the right CI-C2 articulation (according to Magerl) and posterior C1-C2 wiring with graft. The normal atlantoaxial relation was restored with disappearance of torticollis. At follow-up certain limitation of neck movements due to C1-C2 stabilization persisted. No complications were noted. The patient remains neurologically intact and has radiographic documentation of fusion.

Acute torticollis in an adolescent: case report and MRI study

STUDY DESIGN

A case report is presented.

OBJECTIVES

To describe a typical case of acute adolescent torticollis in which a disc lesion was detected with magnetic resonance imaging.

SUMMARY OF BACKGROUND DATA

Acute torticollis is attributed to atlantoaxial rotary fixation of unknown etiology. The current view is that the lesion is caused by synovial fold entrapment in the C1-C2 interspace.

METHODS

In a 15-year-old male adolescent, magnetic resonance imaging was performed a few hours after the onset of torticollis, and 3 weeks after resolution of symptoms.RESULTS Increased signal intensity compatible with a fluid collection was seen in the right uncovertebral region at C2-C3. This lesion was probably linked to a sudden disruption of the disc collagen fibers, and had caused excessive lateral pressure, pushing C2 toward the left. Magnetic resonance imaging at 3 weeks was unremarkable.

CONCLUSIONS

The authors think that the observed disruption was a sudden and abnormal instance of a normal and, usually, very slow process of cleft formation with extension into the fibrocartilaginous core in the uncovertebral region. It is felt that this lesion may be a frequent cause of torticollis in adolescents.

Atlantoaxial rotatory fixation-subluxation revisited: a computed tomographic analysis of acute torticollis in pediatric patients

STUDY DESIGN

Cross-sectional clinical and radiologic study with a normal control group.

OBJECTIVES

To compare the range of motion of the atlantoaxial joint in patients with acute torticollis with those of normals as measured from computed tomography scans, to look for the existence of atlantoaxial rotatory fixation in any position (subluxation or normal range of motion) in this group of patients, and to clarify the definition of atlantoaxial rotatory subluxation by measuring the atlantodental interval and analyzing the location of the center of rotation in patients as well as normal controls.

SUMMARY OF BACKGROUND DATA

Although acute acquired torticollis is usually termed atlantoaxial rotatory subluxation or atlantoaxial rotatory fixation, the radiologic definition of these conditions is not clear.

PATIENTS AND METHODS

Thirty-three consecutive pediatric patients (average age 8.5 years, range 2-18 years) with acute acquired torticollis were analyzed. All were neurologically intact. Anteroposterior and lateral radiographs were obtained in all atlantoaxial computed tomography scans in 31 patients (dynamic in 23 and static in 8). Twelve age-matched patients with normal cervical spines were also analyzed with dynamic computed tomography as normal controls. Atlantoaxial rotatory subluxation, atlantoaxial angle, center of rotation, and presence of atlantoaxial rotatory fixation were analyzed in each computed tomography. All patients were treated conservatively. Eight had control dynamic computed tomography scans at the end of the treatment.

RESULTS

All patients had atlantoaxial rotatory subluxation <or=3 mm. On dynamic computed tomography, the range of atlantoaxial rotation was 30.4 degrees (range 11-54 degrees) toward deformity and 28.3 degrees (range 18-54 degrees) away from deformity (P = 0.333). Atlantoaxial rotatory fixation was not noted in any of the patients. The same measurement for the normal control group was 28 degrees (range 5-41 degrees) (P = 0.770). Of the eight patients with repeat control computed tomography, the atlantoaxial rotatory subluxation was 26 degrees before and 29 degrees after treatment (P = 0.691 to right and P= 0.199 to left). The center of rotation was within dens in 15 of 19 patients, outside dens in 2 of 19, and undetectable in 2 of 19. In the control group, it was within dens in 8 of 11, outside dens in 2 of 11, and undetectable in 1 of 11. All patients were symptom free at the end of the conservative treatment.

CONCLUSION

We could not demonstrate the presence of atlantoaxial rotatory subluxation or atlantoaxial rotatory fixation in our series of 33 consecutive pediatric patients with acute torticollis. Our findings suggest that the existence of these phenomena are doubtful, although not associated with acute acquired torticollis. Acute acquired torticollis is not necessarily the sign of a pathologic condition of the atlantoaxial joint. Finally, it is probably not necessary to obtain computed tomography scans (static or dynamic) in this group of patients at the time of presentation.

Brooks' posterior stabilisation surgery for atlantoaxial instability: review of 54 cases

PURPOSE

To assess the effectiveness of Brooks' posterior stabilisation and fusion for the unstable atlantoaxial joint due to congenital dysplastic dens and trauma.

METHODS

We retrospectively studied records of 54 patients (36 males and 18 females; age range, 3-58 years) who underwent Brooks' posterior stabilisation procedure between March 1975 and December 1999, at the Catholic University of Korea Medical Center and Dong-Shin General Hospital, Seoul. A single-stranded Kirschner wire was used to stabilise the first 19 cases (thin wires in 12 cases and thick wires in 7), and double-stranded wires were used in the next 35 cases (thin wires in 4 cases and thick wires in 31). After surgery, patients were immobilised in bed with light Halter traction of the head, followed by cervical bracing.

RESULTS

Fusion was observed by X-ray postoperatively at 15 weeks in 48 patients. Reduction was achieved in 3 luxation cases (including the single case of rotatory fixation). Brooks' fusion failed in 4 patients with dens fractures and 2 with dens anomaly. Four dens fractures in cases of successful Brooks' fusion in Brooks' fusion did not unite. Wire failure occurred in 4 cases of thin single-stranded wire fixation, namely, 2 cases of dens fractures and 2 of dens anomaly.

CONCLUSION

Brooks' procedure is safe and has a high fusion rate when double-stranded strong wire fixation of the atlantoaxial joint is combined with meticulous bone grafting and subsequent cervical bracing.

Atlanto-axial subluxation syndrome and management of intractable headache, neck pain and shoulder pain with auricular stimulation: a clinical case report

Atlanto-axial subluxation syndrome is a condition that is easily overlooked, misdiagnosed and mismanaged. Anatomy, neurovascular involvement and description of clinical manifestations are reviewed. Bi-Digital O-Ring Test is employed to establish an accurate diagnosis and its value and accuracy described briefly. Bi-Digital O-Ring Test has been an important diagnosis confirmation method (reconfirmed by CT or MRI in over 95% of more than 850 clinical cases) in this author's practice of spinal disorder and intractable pain management. A newly described device, the KIM-STIM, offers auricular stimulation of multiple points, using electrical microcurrent. Each unit is individually custom-molded to the patient's ear, and fitted with multiple electrodes. It was found to be very effective in managing the majority of intractable pain, especially pain requiring multiple daily treatments in order for the patient to live and function normally. The KIM-STIM device allows the patient to self-manage the pain, by day or night, thus allowing for a reduction or elimination of medication intake and diminishing the necessity for frequent doctor visits.

Biomechanical comparison of four anterior atlantoaxial plate systems

OBJECT

The optimum fixation method to achieve atlantoaxial fusion after resection of the odontoid process remains a matter of discussion. Anterior atlantoaxial plate fixation has been described by Harms as a fixation procedure to be performed after transoral odontoid resection. In recent biomechanical and clinical studies investigators have shown that this procedure is a good alternative to established posterior atlantoaxial fixation techniques, but they have also indicated the biomechanical disadvantages of the Harms plate design. Therefore, three new anterior atlantoaxial plate designs were developed. The purpose of this study was to compare these three newly designed plate systems biomechanically with that used in Harms anterior atlantoaxial plate fixation.

METHODS

Twenty-four human craniocervical cadaveric specimens were tested in flexion, extension, axial rotation, and lateral bending in a nonconstrained testing apparatus by using a nondestructive stiffness method. Three-dimensional displacement of C 1-2 was measured with an optical measurement system. Six different groups were examined: 1) control (24 specimens); 2) unstable (after odontoidectomy and dissection of the atlantoaxial ligaments; 24 specimens); 3) Harms (anterior atlantoaxial plate fixation according to Harms; six specimens); 4) subarticular atlantoaxial plate (SAAP; six specimens); 5) transpedicular atlantoaxial plate (TAAP; six specimens); and 6) subarticular atlantoaxial locking plate (SAALP; six specimens). Stiffness, range of motion, and neutral and elastic zones were determined. Compared with the Harms plate, stiffness was significantly higher when methods for placing the SAAP, TAAP, and SAALP devices were used (p < 0.05). Angular displacement of SAALPs was less than that demonstrated in any other group (p < 0.05). Stiffness values in any direction were significantly greater for the SAALP-fixed specimens than for the TAAP, SAAP, Harms, control, or unstable specimens (p < 0.05).

CONCLUSIONS

Experimentally, the SAAP, TAAP, and Harms plate achieved less stable fixation than the SAALP. Therefore, if transoral odontoid resection is performed, SAALP-fixed spines will provide significantly improved stability compared with previous fixation devices and methods. This may be a necessary prerequisite for a fast and uneventful osseous fusion even without additional posterior stabilization.

Degeneration of the atlanto-axial joints: a histological study of 9 cases

Degeneration of the lateral atlanto-axial joints (AAJ) has been described as a potential cause of severe neck pain. However, hardly any data are available on its incidence, especially in comparison to the lower cervical spine. In this histological study, we examined the AAJs in 9 specimens from elderly patients, graded the findings and compared them to those in the facet joints of the lower cervical spine. Most histological changes in the AAJs were mild, but the changes in the lower cervical spine were severer. Previous mechanical studies have described the AAJ as a very mobile joint with large neutral zones, which may explain the mild degree of osteoarthrosis found in these specimens.

A rare cause of cervical spinal stenosis: posterior arch hypoplasia in a bipartite atlas

We describe CT and MRI of a previously unreported combination of atlantoaxial anomalies consisting of posterior arch hypoplasia in a bipartite atlas with an os odontoideum, in a 30-year-old woman presenting with neck and left arm pain. MRI showed the os odontoideum, marked stenosis of the spinal canal at the level of the atlas, with cord compression and evidence of myelopathy. CT revealed a bipartite atlas with midline clefts in anterior and posterior arches, thickening in the anterior arch and hypoplasia of the posterior arch with incurving of both hemiarches. Flexion and extension radiographs demonstrated atlantoaxial instability.

[Atlanto-axial kyphosis]

Atlantoaxial kyphosis (AAK) is a rare sagittal deformity of the occiptoatlantoaxial junction. It is defined as a subgroup of anterior translatory atlantoaxial instability. AAK is a symptom of several ligamentours or bony disorders of the craniocervical junction; however, rheumatoid arthritis and trauma are the most common causes for AAK. AAK can be diagnosed on lateral radiographic views of the upper cervical spine if the angle between McGregor's line and the atlas plane is less than-15 degrees or the atlas-axis angle is greater 105 degrees. Treatment modalities for AAK depend on the ability to reduce the deformity. If closed reduction is achieved, posterior atlantoaxial fusion by sublaminar wiring according to Brooks or transarticular screw fixation according to Magerl are possible choices. Irreducible AAK can be treated with a combined transoral decompression, anterior plating according to Harms, and posterior wiring according to Brooks. This staged therapy for AAK was successful in our rheumatoid patient population with AAK.

The biomechanical study of atlantoaxial fixation

Recent studies of various C(1-2) constructs have confirmed superior stability with transarticular screw fixation. In the meantime, our study on the C2 morphology in Thai people found about 4 per cent of the pedicles were too small for the 3.5 mm. C(1-2) transarticular screw. In order to select a smaller screw to use in this operation, we performed a biomechanical testing of 2 sizes of screw (2.7 mm, 3.5 mm) for transarticular screw fixation and Gallie's wiring, comparison in terms of stiffness in flexion, extension, torsion, anterior and posterior shear loads. There were no statistical differences of the stiffness between 2.7 mm and 3.5 mm transarticular screw fixation in all directions, whereas there were significantly greater stiffness of transarticular screw over Gallie's wiring in various directions (P<0.05).

Spinal-cord compression due to extradural amyloidosis of the cervico-occipital hinge, in a hemodialysed patient. A case report

Long-term dialysed patients can develop an arthropathy, called dialysis arthropathy, due to the deposition and transformation of the beta2 microglobulin into amyloid. The involvement of the spine, called destructive spondyloarthropathy (DSA), occurs between 10 and 25 percent; of these patients, and sometimes causes neurological damage. The disc space narrowing, vertebral body erosion and pseudocystis, in presence of polyarthropathy, chronic renal failure, and carpal tunnel syndrome, allows to make a diagnosis of DSA, which is proved by histological finding of beta2 microglobulin-amyloid. We report a rare case of spinal cord compression due to beta2 microglobulin-amyloid deposit in extradural space of cervico-occipital hinge.

Upper cervical spine surgery in rheumatoid arthritis: retrospective study of 30 patients followed for two years or more after Cotrel-Dubousset instrumentation

PURPOSE

To evaluate the efficacy of upper cervical spine surgery in symptomatic atlantoaxial instability due to rheumatoid arthritis (RA).

MATERIAL AND METHODS

Thirty RA patients (29 women and one man) with a mean age of 56 years were studied retrospectively. Symptomatic forward slippage of the atlas on the axis with a synovial pannus surrounding the odontoid and magnetic resonance imaging evidence of spinal cord compression was present in all 30 patients; 18 patients had vertical translocation of the odontoid and 14 had basilar invagination. Surgery, performed between 1991 and 1997, consisted of occipitocervical fusion in 18 patients and atlantoaxial fusion in 12. Cotrel-Dubousset instrumentation was performed in all 30 patients.

RESULTS

Mean follow-up was four and a half years. All patients were satisfied with the procedure and exhibited marked functional gains and objective neurological improvement (by one class in the Ranawat scheme). Stable fusion was documented in all 30 patients.

CONCLUSION

Cervical instrumentation and bone grafting seems to provide functional and neurological gains in carefully selected RA patients with atlantoaxial instability and spinal cord compression. Long term follow-up suggests that the benefits are sustained and that morbidity is low.

Kinematic evaluation of atlantoaxial joint instability: an in vivo cineradiographic investigation

Although range of motion has been considered the best parameter to quantify atlantoaxial instability, no other kinematic parameters have been determined for dynamic quantification. The objectives of this study were to investigate the kinematics of the normal and pathologic atlantoaxial joints by cineradiography and to determine the in-vivo kinematic parameters, if any, for the quantification of atlantoaxial instability. Sagittal plane motion of the atlantoaxial joints was analyzed by cineradiography in 12 healthy volunteers and 15 patients with atlantoaxial subluxation. In both flexion and extension, C1-C2 sagittal rotation and C1 translation in the sagittal plane were measured continuously to determine the time-displacement curves for both parameters. All patients with atlantoaxial subluxation and seven of the volunteers had the sigmoid pattern in their time-displacement curves in sagittal rotation. In these cases, atlantoaxial motion showed different points of the onset of rapid increase in motion in their sigmoid curves between flexion and extension. The discrepancy between these points was more significant in the patients than in the volunteers. In most of the patients who had atlantoaxial instability, subluxation occurred when the atlantoaxial joints were still in a more extended position and they were reduced when they were still in more flexed position. The discrepancy showed characteristics similar to those of the neutral zone observed during in vitro investigations, suggesting that it becomes a good indicator of in vivo atlantoaxial instability.

[Direct fixation of odontoid process base fractures]

Fractures of the base of odontoid process are serious spinal injuries. Their treatment still remains controversial. External rigid immobilisation is the way of conservative healing. Operations by posterior approach: posterior atlantoaxial fixation, atlantoaxial transarticular screw fixation or even occipitocervical fixation limit range of head motion. Direct odontoid screw fixation preserves normal motion of C1-C2 junction. Success of this method depends on proper patients selection. The authors present description of surgical technique based on literature review and their own experience. The authors perform odontoid fixation by means of single cannulated cancellous screw guided by K-wire. This wire provides stability of broken odontoid process during procedure of screw insertion. Old fracture--1 case in author's experience--has been curetted before fixation. The authors reviewed clinical efficacity and results of direct odontoid screw fixation published in current literature.

[Atlanto-axial rotation and distance in small children. A postmortem study]

The aetiology of atlanto-axial rotatory subluxation is obscure. Therefore, a post mortem investigation was designed in order to evaluate the C 1-2 rotation and translation mobility and to clear the borderline between mobility and instability and to clear the role of the atlanto-axial joints in atlanto-axial rotatory subluxation. C 1-2 specimen of 2 months, 9 months and 53 months old children were used. In the intact specimen and after sequential decision of the atlanto-axial joint capsule, the atlanto-axial membrane, the transverse ligament of the atlas, and eventually the alar ligaments, the atlas was rotated and anteriorly translated over the axis. The end point of the movements was recorded radiographically. Decision of the anatomic structures increased the rotation of up to 25 degrees. The joint capsules are lax and wide thus allowing rotation with almost complete subluxation. The subluxation of atlanto-axial joints probably stays within the normal range of motion and is not a factor of atlanto-axial rotatory subluxation. Interlocking of the facets could not be observed. In atlanto-axial rotatory subluxation the atlanto-dental interval becomes asymmetric. Its radiographic projection is variable and therefore ist does not present a valuable radiographic parameter.

Biomechanical rationale for the pathology of rheumatoid arthritis in the craniovertebral junction

STUDY DESIGN

A finite-element model of the craniovertebral junction was developed and used to determine whether a biomechanical mechanism, in addition to inflammatory synovitis, is involved in the progression of rheumatoid arthritis in this region of the spine.

OBJECTIVES

To determine specific structure involvement during the progression of rheumatoid arthritis and to evaluate these structures in terms of their effect on clinically observed erosive changes associated with the disease by assessing changes in loading patterns and degree of anterior atlantoaxial subluxation.

SUMMARY OF BACKGROUND DATA

Rheumatoid arthritis involvement of the occipito-atlantoaxial (C0-C1-C2) complex is commonly seen. However, the biomechanical contribution to the development and progression of the disease is neither well understood nor quantified. Although previous cadaver studies have elucidated information on kinematic motion and fusion techniques, the modeling of progressive disease states is not easily accomplished using these methods. The finite-element method is well suited for studying progressive disease states caused by the gradual changes in material properties that can be modeled.

METHODS

A ligamentous, nonlinear, sliding-contact, three-dimensional finite-element model of the C0-C1-C2 complex was generated from 0.5 mm thick serial computed tomography scans. Validation of the model was accomplished by comparing baseline kinematic predictions with experimental data. Transverse, alar, and capsular ligament stiffness were reduced sequentially by 50%, 75%, and 100% (removal) of their intact values. All models were subjected to flexion moments replicating the clinical diagnosis of rheumatoid arthritis using full flexion lateral plane radiographs. Stress profiles at the transverse ligament-odontoid process junction were monitored. Changes in loading profiles through the C0-C1 and C1-C2 lateral articulations and their associated capsular ligaments were calculated. Anterior and posterior atlantodental interval values were calculated to correlate ligamentous destruction with advancement of atlantoaxial subluxation.

RESULTS

Model predictions (at 0.3 Nm) fell within one standard deviation of experimental means, and range of motion data agreed with published in vitro and in vivo values. The model predicted that stresses at the posterior base of the odontoid process were greatly reduced with transverse ligament compromise beyond 75%. Decreases through the lateral C0-C1 and C1-C2 articulations were compensated by their capsular ligaments. Anterior and posterior atlantodental interval values indicate that the transverse ligament stiffness decreases beyond 75% had the greatest effect on atlantoaxial subluxation during the early stages of the disease (no alar and capsular ligament damage). Subsequent involvement of the alar and capsular ligaments produced advanced atlantoaxial subluxation, for which surgical intervention may be warranted.

CONCLUSIONS

To the best of the authors' knowledge, this is the first report of a validated, three-dimensional model of the C0-C1-C2 complex with application to rheumatoid arthritis. The data indicate that there may be a mechanical component (in addition to enzymatic degradation) associated with the osseous resorption observed during rheumatoid arthritis. Specifically, erosion of the odontoid base may involve Wolff's law of unloading considerations. Changes through the lateral aspects of the atlas suggest that this same mechanism may be partially responsible for the erosive changes seen during progressive rheumatoid arthritis. Anterior and posterior atlantodental interval values indicate that complete destruction of the transverse ligament coupled with alar and/or capsular ligament compromise is requisite if advanced levels of atlantoaxial subluxation are present.

[A radiological study of the cervical alterations in Down syndrome. New findings on computerized tomography and three dimensional reconstructions]

OBJECTIVE

We studied a large proportion of the population in our health district who have Down's syndrome to determine the incidence and variety of changes in the spine and to define the guidelines for preventive diagnosis advisable in relation to atlanto-axial instability, a common disorder in these patients.

PATIENTS AND METHODS

First phase: a plain X-ray of the cervical spine in a neutral lateral projection and in flexion in 188 patients, measuring the atlanto-odontoid distance. Second phase: computerized tomography (CT) studies and three dimensional reconstructions in 25 patients (13.3%) chosen at random. The axial cuts from the upper portion of C3 to the occiput were 3 mm in thickness with 3 mm intervals and a standard reconstruction algorithm.

RESULTS

The incidences of atlanto-axial instability with an atlodontoid distance (3)5 mm were not comparable with the published series. There was a lower incidence (4.2%), with no difference between measurements in flexion and in the neutral lateral views. There was a greater incidence of malformations than in other reports, including a rare case of os odontoideum and also constant asymmetry of the occipital condyles (100%) in the patients of the CT series and consequently instability of the atlas (96%) and off-centered odontoides (84%).

CONCLUSIONS

The study showed that there was deficient asymmetrical development of the occipital bone, which caused different heights of the occipital condyles and led to cervico-cranial mal-position. For study of the degree of error of position and congenital anomalies. We recommend replacing plain X-ray studies by CT with three dimensional reconstructions.

Cervical flexion: a study of dynamic surface electromyography and range of motion

BACKGROUND

In the comprehensive assessment of painful conditions, dynamic surface electromyography (sEMG) and range of motion (ROM) recordings can provide information regarding muscle spasm, antalgic postures, fear of pain (protective guarding), muscle injury, and disordered movement caused by pain. This study examines ROM and sEMG patterns observed during cervical flexion.

OBJECTIVE

To demonstrate 2 distinctive sEMG recruitment and dynamic ROM patterns observed during cervical flexion and return to mid-line.

DESIGN

Single-subject design with independent measurement of dynamic ROM and sEMG.

SETTING

Applied clinical setting.

PARTICIPANTS

Two subjects with normal ROM and cervical muscles were studied.

MAIN OUTCOME MEASURE

One subject was studied with sEMG. looking at the cervical paraspinals and sternocleidomastoid muscles; the other subject was studied with an active ROM device. Three cervical movements were studied: lower cervical flexion, atlantoaxial (upper) cervical flexion, and a combination upper/lower cervical flexion.

RESULTS

The active ROM device indicates larger movements (higher degrees of flexion) for the lower cervical flexion compared with upper flexion. The combined movement indicates a differential movement from 2 spinal segments. The sEMG recordings indicated differential recruitment patterns. The sternocleidomastoid recruits briskly during the flexion phase of the upper cervical flexion movement, whereas the cervical paraspinals recruit briskly during return to mid-line when the lower cervical flexion is used. The combined upper then lower cervical flexion movement recruits both sets of muscles.

CONCLUSIONS

The results of the study indicate 2 distinct movement patterns associated with upper versus lower cervical flexion and 2 distinct sEMG recruitment patterns. The study suggests that these 2 distinct movements involve 2 distinct cervical segments and are associated with recruitment of different muscle groups. Applied clinical research on the cervical spine should use sEMG recordings to assess both the upper and lower flexion movements as the standard for the study of cervical flexion.

Differential biomechanical effects of injury and wiring at C1-C2

STUDY DESIGN

An in vitro study compared the biomechanics of the upper cervical spine among three groups of cadaveric specimens, each with a different source of instability: transverse-alar-apical ligament disruptions, odontoid fractures, or odontoidectomies. The responses of the three groups were again compared after a uniform posterior cable and graft fixation was applied to the specimens.

OBJECTIVES

To quantify and compare the effects of different injuries on atlantoaxial stability and to determine whether a single fixation technique effectively treats each injury.

SUMMARY OF BACKGROUND DATA

Previous biomechanical studies of atlantoaxial instability have been focused on mechanisms of injury or on comparison among fixation types.

METHODS

Cables and pulleys applied torques to human cadaveric C0-C6 specimens quasistatically while an optical system tracked three-dimensional angular and translational motion at C0-C1 and C1-C2. Specimens were tested immediately after injury, after posterior cable and graft fixation, and after 6000 cycles of fatigue.

RESULTS

Odontoidectomies increased C1-C2 angular and translational range of motion significantly more than odontoid fractures or ligament disruptions, especially during flexion-extension. Odontoid fractures produced a slightly larger increase in C1-C2 angular range of motion than ligament disruptions but a smaller increase in C0-C1 range of motion. The different injuries affected the lax zone and the position of C1-C2 axis of rotation differently. Restabilization by posterior cable and graft reduced motion only moderately for each injury type. All three fixated injuries were susceptible to loosening from fatigue.

CONCLUSION

The three different injuries produce different spinal biomechanical responses. To best promote fusion, posterior cable and graft fixation should be used with an adjunctive stabilizing technique to treat all three injuries.

Natural history of rheumatoid arthritis of the cervical spine

This article reviews the natural history of rheumatoid arthritis involving the cervical spine with special attention given to predictors of paralysis. Understanding the natural history of rheumatoid arthritis of the cervical spine is necessary to determine the benefit of various interventions. The primary treatment goal for cervical instability is prevention of irreversible neurologic injury. The natural history of rheumatoid arthritis for a period of 10 years or more is one of significant disease progression. The natural history of cervical instability in patients with rheumatoid arthritis is more variable, with only some patients having a neurologic deficit develop. Recent studies support prophylactic stabilization of the rheumatoid cervical spine to prevent paralysis in high risk patients. However, proponents for prophylactic arthrodesis must acknowledge that not all cervical instability in rheumatoid arthritis progresses to neurologic deficit, and surgical intervention in patients with rheumatoid arthritis incurs added morbidity and mortality. Identifying the risk factors for progression of cervical instability is the first step in eliminating morbidity and mortality from spinal cord and brain stem compression. Surgical stabilization is indicated not only for those patients with paralysis, but for the subgroups of patients with cervical rheumatoid disease who are at risk for spinal cord and brain stem compression. The posterior atlantodental interval is the most reliable screening tool and predictor of progressive neurologic deficit.

Biomechanical study of atlantoaxial arthrodesis: transarticular screw fixation versus modified Brooks posterior wiring

OBJECTIVE

The purpose of the present study was to compare the biomechanical stability of C1 and C2 vertebrae after treatment of ligamentous instability by either modified Brooks posterior wiring (MB) or transarticular screw (TAS) techniques. We hypothesized that the TAS technique would be more stable because of direct fixation through the facet joints.

STUDY DESIGN

We studied the in vitro stability (arthrodesis) of TAS fixation of C1 and C2 versus that of MB. TAS fixation involves placing screws across the facets from posteriorly at C2 to the anterior surface of C1, plus a bone graft and posterior wiring of C1 and C2.

METHODS

Cervical spines from nine individuals with an average age of sixty-two years (range 51 to 71 years) were harvested from cadavers (six male, three female). C1 and the segment from C2 to C5 were potted to allow motion only at the C1-C2 articulation. The specimens were destabilized by cutting the transverse ligament on both sides of the odontoid and the tectorial membrane between C1 and C2. The MB and TAS techniques were performed by methods similar to those described in the literature. The stiffness of the C1-C2 articulation of each specimen was tested under rotation, lateral bending, flexion, and anterior translation in random order. Intact and destabilized specimens fixed with either MB or TAS were tested in sequence.

RESULTS

Significantly higher stiffness values in the elastic zone were obtained with the TAS technique than with the MB technique for all modes of testing (p < 0.002, t test). Values for the neutral zone (the region where minimal loads produce displacement) were not significantly different between the MB and TAS techniques (p > 0.1, t test).

CONCLUSION

We conclude that stability is significantly enhanced by use of the TAS construct for treatment of ligamentous instability at the atlantoaxial joint for all motions tested in the present study.

[Trans-articular screw fixation of C1/C2 in atlanto-axial instability. Comparison between percutaneous and open procedures]

For posttraumatic atlantoaxial instabilities posterior transarticular screw fixation according to Magerl represents the treatment of choice. In order to be able to insert the screws steep enough the soft tissues of the neck have to be dissected down to C7. Several authors therefore described a percutaneous technique. We analysed 30 patients with a sagittal atlantoaxial instability treated with one of both methods between the years 1995 and 1998 to detect any differences of either technique. In 19 cases we used a modified percutaneous technique with special instruments as has been published by McGuire and Harkey. On lateral plain films the angle between the screws and the lower endplate of C2 was measured. 6 to 24 months after the accident 26 patients could be seen clinically and controlled radiologically, 4 patients had died in the meanwhile. The angle of the screws were significantly different with 10 degrees (percutaneous group 73.9 degrees, open group 63.9 degrees, p = 0.001). Time needed for the operative procedure averaged 35 minutes shorter with the cannulated technique (93 to 128 minutes, p = 0.05). All posterior fusions had healed radiologically. Active motion of the c-spine was restricted in both groups equally. We checked subjective criteria concerning pain and function with a visual analog scale and a special score. With these instruments advantages for the percutaneous procedure could be found (freedom of pain 43 points (percutaneous) versus 39 points (open), p = 0.05). We conclude that the soft tissue preserving percutaneous technique of screw application for C1/C2 posterior fusion allows for a better and easier placement of screws. It also leads to a shorter operating time and better subjective results. The method offers particularly advantages in cases where only a temporary stabilization of the C1/C2 complex without a regular fusion is needed.