The interspinous method of posterior atlantoaxial arthrodesis

Unilateral posterior atlantoaxial transarticular screw fixation

Bilateral posterior C 1-2 transfacet screw placement with associated posterior bone graft wiring is the accepted treatment for patients with atlantoaxial instability. This technique was modified to treat 19 patients with atlantoaxial instability and unilateral anomalies that prevented placement of a screw across the C1-2 facet. In these cases, a single contralateral transarticular screw was placed in conjunction with interspinous bone graft wiring to avoid neural or vertebral artery injury and to provide C1-2 stability. Postoperatively, all 19 patients were placed in Philadelphia collars (mean immobilization 8 weeks, range 6-12 weeks). Unilateral C1-2 facet screw fixation was needed for the following reasons: a high-riding transverse foramen of the C-2 vertebra present in 13 patients (left side in eight, right side in five), poor screw purchase in two (left side in both), screw malposition in one (left side), severe degenerative arthritis in one (right side), neurofibroma in one (right side), and fracture of the C-1 lateral mass in one (left side). Six weeks postsurgery, one patient presented with a broken screw and required occipitocervical fusion with a Steinmann pin and wire cable from the occiput to C-3 to achieve solid fusion. Solid fusions were achieved in the other 18 patients (mean follow-up period 31 months, range 14-54 months); there was no delayed screw breakage, wire breakage, or spinal instability. There were no operative or postoperative neurological or vascular complications. The authors' experience demonstrates that unilateral C1-2 facet screw fixation with interspinous bone graft wiring is an excellent alternative in the treatment of atlantoaxial instability when bilateral screw fixation is contraindicated.

Acute axis fractures. Analysis of management and outcome in 340 consecutive cases

STUDY DESIGN

Retrospective review of acute axis fractures treated at a tertiary referral center.

OBJECTIVE

To determine the optimal treatment of axis fractures based on 340 cases from a single institution.

SUMMARY OF BACKGROUND DATA

Axis fractures account for almost 20% of acute cervical spine fractures. However, their management and the clinical criteria predictive of nonoperative failure remain unclear.

METHODS

Admission imaging studies and clinical variables were obtained for 340 consecutive axis fracture patients. Fractures were classified as as odontoid Type I, II, or III with dena displacement on admission roentgenograms; hangman's fractures of Francis grade and Effendi type; and miscellaneous fractures. Treatment methods were documented, and outcomes were based on dynamic lateral roentgenograms, clinical examination, or telephone interviews at last follow-up.

RESULTS

Follow-up data were available in 92% of cases. Type II odontoid fractures comprised 35% of all axis fractures, were the most difficult to treat, and had the highest nonunion rate (28.4%). Odontoid displacement of 6 mm or more was associated with Type II nonunion (chi-square = 33.74, P < 0.0001). Patients underwent surgical fusion if fracture alignment could not be maintained by an external orthosis, or if they had odontoid fractures with transverse ligament disruption, Type II odontoid fractures with dens displacement of at least 6 mm, or hangman's fractures of severe Francis grade or Effendi type.

CONCLUSIONS

Type II odontoid fractures have the highest nonunion rate and were associated with dens displacement of 6 mm or greater. Early surgical fusion is recommended for acute fracture instability despite external immobilization, transverse ligament disruption, Type II odontoid fractures with dens displacement of at least 6 mm on admission, or severe Francis grade or Effendi-type hangman's fractures. Otherwise, nonoperative management is sufficient.

Triple anterior screw fixation of an acute combination atlas-axis fracture. Case report

The authors report the successful treatment of an acute combination atlas-axis fracture in an 85-year-old man using anterior odontoid and C1-2 transarticular facet screw fixation and a Philadelphia collar. Treatment with halo brace immobilization failed, and the patient experienced recurrent episodes of oxygen desaturation when placed partially prone for chest physiotherapy. If a posterior approach is not feasible, an anterior odontoid and C1-2 transarticular facet screw fixation can be considered as a salvage procedure for patients with acute combination atlas-axis fractures.

Frameless stereotactic guidance for surgery of the upper cervical spine

OBJECTIVE

The goal was to evaluate and describe the use of a frameless, computed tomography-guided, stereotactic technique in complex procedures involving the craniocervical junction.

METHODS

Eleven procedures, including transoral odontoid resection, posterior atlantoaxial fusion with transarticular C1-C2 screw fixation, and spinal tumor resection, were performed in the preceding 26 months. In each case, frameless stereotaxy was used to plan the incision, to define resection margins, and to determine the appropriate orientation of instrumentation.

RESULTS

There were no intraoperative complications noted. Each patient underwent adequate resection of the pathological lesion and satisfactory placement of instrumentation. The stereotactic system provided detailed anatomic visualization, which increased the confidence of the surgeon during the procedure. The system limited the need for extensive surgical exposure, reduced fluoroscopy time, and decreased the risk of neurovascular injury.

CONCLUSION

Frameless stereotaxy provided the surgeon with intraoperative information regarding the extent of bone and soft tissue resection. It provided a multidimensional view of anatomic relationships in the operative field, which significantly increased surgical accuracy and safety.

Cervical spine fractures in the elderly

BACKGROUND

Cervical spine fractures in the elderly are relatively common. The management of such injuries may be complicated by underlying medical debility and osteopenia as well as reduced tolerance to halo immobilization.

METHODS

Over a 1-year period, 43 cervical spine fractures were treated at our institution. Ten (23%) were in persons 70 years of age or older. This retrospective analysis describe the clinical features, treatment, and outcome of these 10 elderly patients. All fractures in this patient population involved the atlantoaxial complex, including five combination C1-C2 fractures. Six patients were treated with early halo immobilization and three were initially managed with a rigid cervical collar. Three patients required posterior cervical fusion.

RESULTS

Of the six patients undergoing halo immobilization, five progressed to osseous union. Three patients were immobilized in a Philadelphia collar resulting in one osseous union, one nonunion, and one death. Three patients underwent posterior cervical fusion with subsequent osseous union in all three.

CONCLUSIONS

Although external immobilization with a halo device is our treatment of choice for most C1 and C2 fractures in elderly patients, a Philadelphia collar is useful in select cases when halo immobilization or early surgical fusion is contraindicated. Posterior cervical fusion can be safely and effectively performed in elderly patients and should be strongly considered for initial therapy in the elderly with fracture types unlikely to progress to osseous union with external immobilization alone.

Use of an adjustable, transportable, radiolucent spinal immobilization device in the comprehensive management of cervical spine instability. Technical note

In this report the authors describe a device that consists of a transportable, radiolucent board that couples to a standard halo head ring. The board provides continuous cervical spine immobilization during all phases of acute medical treatment of cervical spine instability, including closed reduction, transport, radiographic imaging, and operative procedures. By combining the advantages of several existing systems, this immobilization device facilitates and improves the safety of comprehensive acute management of cervical spinal instability by eliminating the need for patient transfer from stretcher to radiography machine to operating table. Its radiolucent construction and its compatibility with standard operating tables allow unencumbered surgical access and ample room for biplanar fluoroscopy, thereby also facilitating operative procedures, particularly the placement of internal spinal fixation.

Predictors of outcome in the quadriparetic nonambulatory myelopathic patient with rheumatoid arthritis: a prospective study of 55 surgically treated Ranawat class IIIb patients

The functional results of surgery in patients with myelopathic nonambulatory rheumatoid arthritis (Ranawat Class IIIb) are often disappointing, with high rates of postoperative morbidity and mortality. The authors therefore undertook a detailed investigation of a cohort of 55 Ranawat Class IIIb patients (11 men and 44 women) with a mean age of 64.7 years who were recruited prospectively over a 10-year period (1983-1993), to determine what factors may accurately predict a good surgical outcome. Only 14 patients (25.5%) were judged to have had a favorable outcome as determined by an improvement to Ranawat Class I or II or an improvement of at least 0.5 points in the Stanford Health Assessment Questionnaire disability index. The early postoperative mortality rate was high (12.7%) in this group and almost one-quarter of the patients were dead within 6 months. These poor results mirror those already published in the existing literature. Univariate analysis revealed that age (p = 0.02), degree of vertical translocation (p = 0.05), and, more importantly, spinal cord area (p = 0.006) were significant predictors of outcome. Multiple logistic regression analysis showed that spinal cord area (p = 0.026) was, in fact, the major determinant of outcome and, indeed, of long-term survival (p = 0.001). The mean spinal cord area of those patients not achieving a good outcome was 44 mm2. The atlantodens interval (ADI) was not shown to be a significant outcome determinant, which may be explained by the correlation between an increasing vertical translocation and a decreasing ADI (r = 0.4, p = 0.01). Furthermore, as the degree of vertical translocation increased, the space available for the cord was observed to decrease (p = 0.003) commensurate with a reduction in spinal cord area (p = 0.02). Together, these findings strongly argue for earlier surgical intervention, before the development of vertical translocation, permanent neurological damage, and spinal cord atrophy can occur.

Arteriovenous fistula as a complication of C1-2 transarticular screw fixation. Case report and review of the literature

A case is reported of a vertebral artery-to-epidural venous plexus fistula as a complication of posterior atlantoaxial facet screw fixation. The use of transarticular screws to stabilize the C1-2 joint has become an increasingly popular fixation technique, most notably for atlantoaxial instability due to trauma or rheumatoid disease. Despite the fact that this approach is technically challenging, there have been few reports of complications associated with C1-2 transarticular fixation. Although damage to the vertebral artery is a documented hazard of transarticular fixation at this level, a symptomatic arteriovenous fistula resulting from the procedure has not been described previously. The etiology, presentation, and treatment of this unusual complication are discussed.

Biomechanical characteristics of C1-2 cable fixations

The biomechanical characteristics of four different methods of C1-2 cable fixation were studied to assess the effectiveness of each technique in restoring atlantoaxial stability. Biomechanical testing was performed on the upper cervical spines of four human cadaveric specimens. Physiological range loading was applied to the atlantoaxial specimens and three-dimensional motion was analyzed with stereophotogrammetry. The load-deformation relationships and kinematics were measured, including the stiffness, the angular ranges of motion, the linear ranges of motion, and the axes of rotation. Specimens were nondestructively tested in the intact state, after surgical destabilization, and after each of four different methods of cable fixation. Cable fixation techniques included the interspinous technique, the Brooks technique, and two variants of the Gallie technique. All specimens were tested immediately after fixation and again after the specimen was fatigued with 6000 cycles of physiological range torsional loading. All four cable fixation methods were moderately flexible immediately; the different cable fixations allowed between 5 degrees and 40 degrees of rotational motion and between 0.6 and 7 mm of translational motion to occur at C1-2. The Brooks and interspinous methods controlled C1-2 motion significantly better than both of the Gallie techniques. The motion allowed by one of the Gallie techniques did not differ significantly from the motion of the unfixed destabilized specimens. All cable fixation techniques loosened after cyclic loading and demonstrated significant increases in C1-2 rotational and translational motions. The bone grafts shifted during cyclic loading, which reduced the effectiveness of the fixation. The locations of the axes of rotation, which were unconstrained and mobile in the destabilized specimens, became altered with cable fixation. The C1-2 cables constrained motion by shifting the axes of rotation so that C-1 rotated around the fixed cable and graft site. After the specimen was fatigued, the axes of rotation became more widely dispersed but were usually still localized near the cable and graft site. Adequate healing requires satisfactory control of C1-2 motion. Therefore, some adjunctive fixation is advocated to supplement the control of motion after C1-2 cable fixation (that is, a cervical collar, a halo brace, or rigid internal fixation with transarticular screws).

C1-C2 transarticular screw fixation for treatment of C1-C2 instability

C1-C2 instability has traditionally been treated by C1-C2 posterior wiring and bone grafting. However, this technique has an incidence of non-union which may exceed 10%. Transarticular screw fixation has developed as a technique of providing increased strength of fixation of C1-C2 arthrodesis, while at the same time avoiding the need for postoperative halo bracing and avoiding the risk of neurological injury associated with the passage of sublaminar wires. We present a retrospective review of 12 patients with C1-C2 instability treated by C1-C2 transarticular screw fixation. Eight patients underwent this procedure as primary treatment, and 4 after a failed Gallie fusion. Five patients had a cruciate ligament rupture, 5 had an odontoid process fracture, 1 had os odontoideum, and 1 had rheumatoid instability. There was no surgical morbidity or mortality and, at a mean follow up of 12.1 +/- 3 months (range 8-14 months), all patients had achieved solid fusion, and all neurological symptoms referable to the instability had resolved. C1-C2 transarticular screw fixation has been shown to be safe and effective and has a number of advantages when compared to traditional posterior wiring techniques. We recommend that this technique be considered as a primary treatment of C1-C2 instability.

Atlantoaxial arthrodesis using Halifax interlaminar clamps reinforced by halo vest immobilization: a long-term follow-up experience

Thirty-two patients who underwent atlantoaxial arthrodesis using Halifax interlaminar clamps and halo vests between January 1989 and December 1992 were reviewed. The atlantoaxial instabilities were related to trauma in 16 patients, including 14 patients with unstable odontoid fractures, 1 patient with a complex C2 fracture, and 1 patient with a disrupted transverse ligament. Of the other 16 patients, whose atlantoaxial instabilities were nontraumatic in origin, 9 had instabilities that were secondary to rheumatoid arthritis, 1 had instability that was secondary to tuberculous infection, and 6 had instabilities that were caused by os odontoideum. The patients were followed postoperatively with lateral cervical radiographs for an average of 37 months (range, 16-59 mo). Solid atlantoaxial arthrodeses were achieved in all (100%) of these 32 patients after 32 to 111 days (average, 84.5 d) of halo immobilization, indicating atlantoaxial arthrodeses can be reasonably anticipated when Halifax interlaminar clamps with autogenous iliac bone grafting are reinforced by halo vest immobilization for 3 months.

C1-C2 posterior cervical fusion: long-term evaluation of results and efficacy

Posterior wiring techniques are the most commonly used methods of achieving C1-C2 arthrodesis. Recently, transarticular screw fixation and interlaminar clamping have been advocated to achieve more secure fixation. A retrospective review of patients undergoing C1-C2 fusion for nonneoplastic disease was undertaken at the University of Toronto Hospital, with the aim of determining the long-term outcome of the selected procedures. Thirty-two patients underwent 36 procedures from 1986 to 1992, with a mean follow-up of 4.7 +/- 2.2 years (range, 2.0-8.0 yr). The most common disease processes were odontoid fracture (18 patients), transverse atlantal ligament injury (5 patients), os odontoideum (5 patients), and rheumatoid C1-C2 instability (3 patients). Thirty-one Gallie fusions, one Brooks-Jenkins fusion, two transarticular screw fusions, and two Halifax clamp applications were performed. Six (19%) of Gallie/Brooks-Jenkins fusions failed. These occurred with os odontoideum (three patients), Type II odontoid fracture (two patients), and transverse atlantal ligament injury (one patient). All transarticular screw and Halifax clamp procedures resulted in successful fusions. Two procedures (6%) resulted in new neurological deficit; both of these patients underwent posterior wiring for os odontoideum. This study suggests that Type II odontoid fractures may be successfully managed by a posterior wiring technique alone. Rheumatoid C1-C2 instability may be managed by posterior wiring supplemented with halo immobilization. Transarticular screw fixation has several potential advantages as a technique for C1-C2 arthrodesis and, in particular, may be appropriate for os odontoideum that had a high failure rate (75%) with conventional posterior wiring, even when this was supplemented with halo bracing.

Injuries involving the transverse atlantal ligament: classification and treatment guidelines based upon experience with 39 injuries

Comprehensive anatomic and clinical analyses of 39 patients with injuries involving the transverse atlantal ligament or its osseous insertions were performed to assess the morphology of the injured ligaments and the patients' capacity to heal. Injuries of the upper cervical spine were screened with plain radiographs, thin-section computed tomography, and magnetic resonance imaging studies. The injuries were classified as disruptions of the substance of the ligament (Type I injuries, n = 16) or as fractures and avulsions involving the tubercle for insertion of the transverse ligament on the C1 lateral mass (Type II injuries, n = 23). These two types of injuries had distinctly different clinical characteristics that were useful for determining treatment. Type I injuries were incapable of healing satisfactorily without internal fixation; they should be treated with early surgery. Type II injuries, which rendered the transverse ligament physiologically incompetent even though the ligament substance was not torn, should be treated initially with a rigid cervical orthosis, because they had a 74% success rate nonoperatively. Surgery should be reserved for patients with Type II injuries that have nonunion with persistent instability after 3 to 4 months of immobilization. Type II injuries had a 26% rate of failure of immobilization; therefore, close monitoring is needed to detect patients who will require delayed operative intervention.

C1-C2 posterior cervical fusion: long-term evaluation of results and efficacy

Posterior wiring techniques are the most commonly used methods of achieving C1-C2 arthrodesis. Recently, transarticular screw fixation and interlaminar clamping have been advocated to achieve more secure fixation. A retrospective review of patients undergoing C1-C2 fusion for nonneoplastic disease was undertaken at the University of Toronto Hospital, with the aim of determining the long-term outcome of the selected procedures. Thirty-two patients underwent 36 procedures from 1986 to 1992, with a mean follow-up of 4.7 +/- 2.2 years (range, 2.0-8.0 yr). The most common disease processes were odontoid fracture (18 patients), transverse atlantal ligament injury (5 patients), os odontoideum (5 patients), and rheumatoid C1-C2 instability (3 patients). Thirty-one Gallie fusions, one Brooks-Jenkins fusion, two transarticular screw fusions, and two Halifax clamp applications were performed. Six (19%) of Gallie/Brooks-Jenkins fusions failed. These occurred with os odontoideum (three patients), Type II odontoid fracture (two patients), and transverse atlantal ligament injury (one patient). All transarticular screw and Halifax clamp procedures resulted in successful fusions. Two procedures (6%) resulted in new neurological deficit; both of these patients underwent posterior wiring for os odontoideum. This study suggests that Type II odontoid fractures may be successfully managed by a posterior wiring technique alone. Rheumatoid C1-C2 instability may be managed by posterior wiring supplemented with halo immobilization. Transarticular screw fixation has several potential advantages as a technique for C1-C2 arthrodesis and, in particular, may be appropriate for os odontoideum that had a high failure rate (75%) with conventional posterior wiring, even when this was supplemented with halo bracing.

Surgical management of atlantoaxial nonunions

Sixteen patients referred for atlantoaxial fixation failures were treated surgically with revision procedures during the past decade. Of these 16 patients, atlantoaxial instability occurred because of rheumatoid arthritis in five, as odontoideum in seven, transverse ligament disruption in two, and odontoid fracture nonunion in two. The 16 individuals (10 men, six women; mean age 43.7 years; age range 20-77 years) had undergone a total of 20 C1-2 internal fixation procedures that failed. Surgical strategies for definitive revision of the nonunions in these 16 subjects included 10 rigid internal fixations with transarticular screws, three revised C1-2 fixations with autogenous bone struts and wire or cables, and three extended fixations with occipitocervical instrumentation. Autogenous grafts were used in all revisions. A postoperative halo brace was used in five individuals with osteoporotic bone; all patients wore a restrictive postoperative cervical orthosis. Postoperatively, 15 patients (94%) had a stable construct (mean follow up 35 months; range 12-79 months), which included 13 osseous unions and two stable fibrous unions. One patient had nonunion; he fractured his anterior C1-2 transarticular screws 2 years postoperatively. He had occipital radicular pain without myelopathy but refused further surgery. Atlantoaxial pseudarthroses were effectively treated by addressing the pathological, biomechanical, and technical reasons for failed fusion. Successful fusion after reoperation was improved by using autologous bone grafts, adequately controlling atlantoaxial motion (with rigid transarticular screws internally or externally with a halo vest), compressing the bone grafts between the arches of C-1 and C-2 with wire cables, meticulously preparing the fusion bed, and by optimizing the pharmacological and clinical parameters to promote bone healing.

Occipito-cervical fixation in rheumatoid arthritis--an analysis of surgical risk factors in 163 patients

163 patients with rheumatoid arthritis (RA) and atlanto-axial subluxation treated by posterior occipito-cervical fixation (OCF) over a period of twenty-one years (November 1970-January 1991) were followed. Common complaints prior to surgery were occipital headache, neck pain, radicular pain and myelopathy. The mean age at time of surgery was 61 years. The mean follow-up time was 54 months. Clinical improvement was obtained in 88% of the patients, whereas 7% were unchanged and 5% had progressive symptoms in spite of surgery. There was no pre-operative or immediate postoperative mortality. In 79 patients, one or more potential surgical risk factors were identified. Twenty-four reoperations were performed in the neck. The most common cause for reoperation was mechanical failure due to wire-break or spinous process fracture. Wound infection in the neck was recorded in 16 patients. Five were deep and required removal of the fixation material. Following OCF, new or progressive subaxial subluxation (SAS) led to further surgery in 4%. The study offers support for the beneficial effect of OCF in rheumatoid AAS. We conclude that, in spite of a number of identified risk factors, OCF with the Brattström-Granholm technique remains a safe and effective method for stabilization of upper cervical subluxations in RA.

Reconstruction of the hypoplastic posterior arch of the atlas with calvarial bone grafts for posterior atlantoaxial fusion: technical report

Posterior atlantoaxial fusion is a common procedure performed for instability at C1-C2. This operation requires intact posterior elements of both the atlas and the axis. When this is not the case, the incorporation of the occiput and the lower spinal segments is usually required for adequate posterior fusion, but such a procedure limits the mobility of the upper cervical spine. A technique for the reconstruction of the posterior arch of the atlas with calvarial bone is described in this report. This technique allowed the successful fusion of the C1 and C2 vertebrae in a patient with traumatic atlantoaxial subluxation who also had a congenital absence of the posterior arch of the atlas.

Odontoid fractures. Review of 150 cases and practical application for treatment

A total of 150 odontoid fractures was treated over a 12-year period, 43 by anterior screw fixation. The rate of pseudarthrosis dropped from 20% to 5% in type II unstable fractures. Thus, anterior screw fixation seems to be safe and efficient, and may be more widely used to treat all type II and some type III fractures. Odontoid pseudarthrosis is usually tolerated quite well and therefore requires no correction. If necessary, anterior grafting with fixation can be proposed as an alternative for posterior fusion.

Bovine bone grafting in occipito-cervical fusion for atlanto-axial instability in rheumatoid arthritis

Bovine bone chips (Surgibone) were used in occipito-cervical fusion in nine patients with atlanto-axial instability due to rheumatoid arthritis. The patients were examined with CT 12-15 months after surgery. Graft resorbtion was observed in one patient. The other 8 patients showed preserved grafts, in most cases the grafts appeared to be in contact with the underlying bone. One patient was revised, and at the grafted site a bony bridge was found. In conclusion, the use of bovine chips in posterior occipito-cervical fusion will not lead to predictable bone union. However, there seem to be exceptions to that rule.

Plate and screw fixation for atlanto-axial subluxation

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

Posterior atlantoaxial facet screw fixation

Eighteen patients with atlantoaxial instability were treated with posterior atlantoaxial facet screws to obtain immediate rigid fixation of C1-2. Of these 18 patients, instability occurred due to trauma in nine, rheumatoid arthritis in six, neoplasms in two, and os odontoideum in one. Four patients presented with nonunion after failed C1-2 wire and graft procedures. In all cases in this series the screw fixations were augmented with an interspinous C1-2 strut graft which was wired in place to provide three-point stabilization and to facilitate bone fusion. In every case fixation was satisfactory, and C1-2 alignment and stability were restored without complications due to instrumentation. One patient died 3 months postoperatively from metastatic tumor; the spinal fixation was intact. All 17 surviving patients have developed osseous unions (mean follow-up period 12 months, range 6 to 16 months). Posterior atlantoaxial facet screw fixation provides immediate multidirectional rigid fixation of C1-2 that is mechanically superior to wiring or clamp fixation. This technique maximizes success without the need for a supplemental rigid external orthosis, and is particularly useful for pseudoarthrosis.

Occipital-axis posterior wiring and fusion for atlantoaxial dislocation associated with occipitalization of the atlas. Technical note

The authors present their technique of occipital-axis posterior wiring and fusion for atlantoaxial dislocation associated with an occipitalized atlas. The technique consists of drilling a 3 x 1-cm horizontal groove in the occipital bone 1 cm posterior to the foramen magnum and building up a bony bridge along the posterior margin of the foramen magnum. This bony bridge is referred to as an "artificial atlas." Conventional wiring and fusion is performed between the artificial atlas and the C-2 lamina, interposing a strut bone graft. Since the compression force on tightening the wire is vertical, a very high degree of stability for the occipital-C-2 complex is achieved, facilitating early mobilization without postoperative redislocation.

Halifax interlaminar clamp for posterior cervical fusion: a long-term follow-up review

Fifty consecutive patients requiring posterior cervical fusion for various pathologies were treated with Halifax interlaminar clamps for internal spinal fixation. Fusion involved the C1-2 level in 17 cases, the C1-3 level in one, and the lower cervical area (C2-7) in 32. No patient was lost to follow-up review, which varied from 6 to 40 months (average 21 months). Fusion failed in five patients, three at the C1-2 level, one at the C1-3 level, and one at the C2-3 level. Screw loosening was the cause of failure in four patients, and in one the arch of C-1 fractured. No other complications occurred. Because of the lack of complications, avoidance of the hazards of sublaminar instrumentation, and an excellent fusion rate, this technique is highly recommended for posterior cervical fusion in the lower cervical spine. Atlantoaxial arthrodesis was achieved in only 14 (82%) of 17 patients, however, which might be due to the higher mobility at this multiaxial level. Improved results in this region may be possible by using a new modified interlaminar clamp, by performing adequate bone fusions, and by postoperative external halo immobilization in high-risk patients.

Odontoid fractures in elderly patients

This retrospective analysis describes the clinical characteristics, treatment, and outcome of 19 patients aged 80 years or older with odontoid fractures. The fractures were due to falls in 15 patients (78.9%) and were associated with motor-vehicle accidents in four. Type III fractures were seen in three patients and type II fractures in 16. No patient suffered a neurological injury associated with the fracture. Five patients (26.3%) died during hospitalization; factors contributing to their death included prolonged bed rest, associated injuries, and concomitant medical illnesses. The mean follow-up period in the remaining 14 patients was 28.8 months (range 5 to 72 months). Eight patients with a posterior displacement of 5 mm or less were treated with cervical immobilization, three of whom showed a stable non-union of the fracture site at follow-up review. One patient with 10-mm displacement refused operative treatment. Three of the patients without surgical treatment subsequently died from unrelated causes; all remaining patients resumed their routine activity. Five patients with displacement of 5 mm or greater and instability at the fracture site were treated with posterior cervical fusion of C1-2 using wire and autologous iliac bone grafts. In this group, no operative morbidity or mortality occurred and stable constructs developed in all patients; one patient died from an unrelated cause during the follow-up period and the other patients resumed their normal activity. Prolonged bed rest caused respiratory complications in two of six patients who survived initial hospitalization; two of three patients treated with rigid immobilization developed complications that required alternative treatments.

The influence of transoral odontoid resection on stability of the craniovertebral junction

Twenty-seven cases of craniovertebral junction compression treated with transoral surgery were reviewed to assess the influences of pathological processes and surgical interventions on spinal stability. All patients presented with signs and symptoms of spinal-cord or brain-stem dysfunction. Pathology included rheumatoid arthritis in 11 patients, congenital osseous malformations in 11, spinal fractures in two, plasmacytoma in one, osteomyelitis in one, and a gunshot injury in one. Instability was defined as clear radiographic evidence of mobile subluxation in conjunction with clinical assessment. Of 19 patients (70%) requiring internal fixation, nine underwent upper cervical fusion and 10 had occipitocervical fusion. When instability occurred, all subluxations were at the C1-2 level. There were no occipito-atlantal subluxations. Eight patients (30%) had preoperative instability of the craniovertebral junction due solely to their pathology, 11 patients (40%) suffered instability after transoral surgery, and eight (30%) were without clinical or radiographic evidence of instability (mean follow-up period 14 months). Craniovertebral junction instability predominated among patients with rheumatoid arthritis: 91% required fusion and 45% presented with pre-existing instability. Among individuals with congenital osseous malformations, 45% required fusion and only one patient (9%) had pre-existing instability. Patients who required subsequent posterior decompression of a Chiari malformation were at risk for developing instability; three of four became unstable after posterior decompression. Transoral resection of the dens, the anterior arch of C-1, and the lower clivus does not fully destabilize the spine; however, this operation may potentiate incipient pathological instability. The primary determinants of instability are the extent of pathological bone destruction, ligamentous weakening, and operative bone removal. Long-term follow-up monitoring is needed after transoral surgery to detect cases of late instability.

Magnetic resonance imaging of the transverse atlantal ligament for the evaluation of atlantoaxial instability

Twenty normal human subjects and 14 patients with upper cervical spine pathology were studied with axial high-field magnetic resonance (MR) imaging to examine the transverse atlantal ligament. Gradient-echo MR imaging pulse sequences provided reliable visualization of the transverse ligament, which exhibited low signal intensity and extended behind the dens between the medial portions of the lateral masses of C-1. The MR imaging characteristics of the transverse ligament were verified in clinical studies and in postmortem specimens. The clinical MR examinations defined 27 normal ligaments, three ligament disruptions, and four stretched rheumatoid ligaments. Atlantoaxial instability associated with transverse ligament rupture or ligamentous laxity required internal fixation. In contrast, fractures of C-1 or C-2 or atlantoaxial rotatory dislocations associated with an intact transverse ligament healed without instability or nonunion. The transverse ligament is the primary stabilizing component of C-1. The treatment of atlantoaxial instability has previously been based on criteria drawn from computerized tomography or plain radiographic studies, which only indirectly assess the probability of rupture of the transverse ligament. It is concluded that MR imaging accurately depicts the anatomical integrity of the transverse ligament. After transverse ligament failure, the remaining ligaments of the craniovertebral junction are inadequate to maintain stability. The presence of ligament disruption should be considered as a criterion for early fusion.

Atlantoaxial stabilization in rheumatoid arthritis

Atlantoaxial subluxation in patients with rheumatoid arthritis is common. Operative stabilization is clearly indicated when signs and symptoms of spinal cord compression occur. However, many recommend early operative fusion before evidence of appreciable neural compression occurs because 1) the myelopathy in these patients may be irreversible; 2) the overall prognosis is poor once symptoms of cord compression are present; and 3) the risk of sudden death associated with atlantoaxial subluxation is increased even in asymptomatic patients. The authors believe that rheumatoid arthritis patients in relatively good health without advanced multisystem disease and less than 65 years of age should be considered for operative stabilization if mobile atlantoaxial subluxation is greater than 6 mm. Seventeen patients with severe rheumatoid arthritis and atlantoaxial subluxation treated with a posterior arthrodesis are presented. A new method of fusion, devised by the senior author (V.K.H.S.), was utilized in all cases. Indications for operative therapy in these patients included evidence of spinal cord compression in 11 patients (65%) and mobile atlantoaxial subluxation greater than 6 mm but no signs or symptoms of cord compression in six patients (35%). Thirteen patients developed a stable osseous fusion, two patients a well-aligned fibrous union, one patient a malaligned fibrous union, and one patient died prior to evaluation of fusion stability. The details of the operative technique and management strategies are presented. Several technical advantages of this method of fusion make this approach particularly useful in patients with rheumatoid arthritis. Because of multisystem involvement of this disease, a high rate of osseous fusion is often difficult to achieve.