Aims. Fracture of the odontoid process (OP) in the elderly is associated with mortality rates similar to those of hip fracture. The aim of this study was to identify variables that predict mortality in patients with a fracture of the OP, and to assess whether established hip fracture scoring systems such as the Nottingham Hip Fracture Score (NHFS) or Sernbo Score might also be used as predictors of mortality in these patients. Patients and Methods. We conducted a retrospective review of patients aged 65 and over with an acute fracture of the OP from two hospitals. Data collected included demographics, medical history, residence, mobility status, admission blood tests, abbreviated mental test score, presence of other injuries, and head injury. All patients were treated in a semi-rigid cervical orthosis. Univariate and multivariate analysis were undertaken to identify predictors of mortality at 30 days and one year. A total of 82 patients were identified. There were 32 men and 50 women with a mean age of 83.7 years (67 to 100). Results. Overall mortality was 14.6% at 30 days and 34.1% at one year. Univariate analysis revealed head injury and the NHFS to be significant predictors of mortality at 30 days and one year. Multivariate analysis showed that head injury is an independent predictor of mortality at 30 days and at one year. The NHFS was an independent predictor of mortality at one year. The presence of other spinal injuries was an independent predictor at 30 days. Following survival analysis, an NHFS score greater than 5 stratified patients into a significantly higher risk group at both 30 days and one year. Conclusion. The NHFS may be used to identify high-risk patients with a fracture of the OP. Head injury increases the risk of mortality in patients with a fracture of the OP. This may help to guide multidisciplinary management and to inform patients. This paper provides evidence to suggest that frailty rather than age alone may be important as a predictor of mortality in elderly patients with a fracture of the odontoid process. Cite this article: Bone Joint J 2019;101-B:253–259

Aims: The optimal treatment of Type II odontoid fractures remains controversial. Our retrospective multicentric study of 114 odontoid process fractures documents experience with management of these fractures and discuss a new classification subtype II T and its surgical treatment. Methods: Fractures were defined using plain radiographs and CT reconstructions as per the Anderson- D’Alonzo classification. We have surgically treated 114 consecutive patients suffering from C2 odontoid fracture. 104 fractures were classified as Type II and 10 as Type III. Two cases of atypical, horizontal, mid-shaft odontoid process fractures were reported. In 55% an anterior two-screw fixation technique was chosen, remaining 45% underwent single-screw fixation. Results: One year follow-up data were available in 86.8% of cases and no major complications were found. Fusion rate calculated 6 months following surgery was 93%. We encountered cases, where the fracture line passes transversally through the middle of the shaft of odontoid process, below the level of transverse atlantal ligament, and we suggest to classify these cases as Type II T fractures. Also we analysed series of 75 surgically treated C1-2 instabilities and out of 11 pseudoarthrosis of the odontoid process 7 unrecognised Type II T fractures were found. Conclusions: Reported atypical fractures, newly classified as Type II T, are highly unstable (especially in rotations). In the authors’ opinion, two- screw technique should be the treatment of choice when internal fixation indicated

Ventral screw osteosynthesis is a common surgical method for treating fractures of the odontoid peg, but there is still no consensus about the number and diameter of the screws to be used. The purpose of this study was to develop a more accurate measurement technique for the morphometry of the odontoid peg (dens axis) and to provide a recommendation for ventral screw osteosynthesis. Images of the cervical spine of 44 Caucasian patients, taken with a 64-line CT scanner, were evaluated using the measuring software MIMICS. All measurements were performed by two independent observers. Intraclass correlation coefficients were used to measure inter-rater variability. The mean length of the odontoid peg was 39.76 mm (. sd. 2.68). The mean screw entry angle α was 59.45° (. sd. 3.45). The mean angle between the screw and the ventral border of C2 was 13.18° (. sd. 2.70), the maximum possible mean converging angle of two screws was 20.35° (. sd. 3.24). The measurements were obtained at the level of 66% of the total odontoid peg length and showed mean values of 8.36 mm (. sd. 0.84) for the inner diameter in the sagittal plane and 7.35 mm (. sd. 0.97) in the coronal plane. The mean outer diameter of the odontoid peg was 12.88 mm (. sd. 0.91) in the sagittal plane and 11.77 mm (. sd. 1.09) in the coronal plane. The results measured at the level of 90% of the total odontoid peg length were a mean of 6.12 mm (. sd. 1.14) for the sagittal inner diameter and 5.50 mm (. sd. 1.05) for the coronal inner diameter. The mean outer diameter of the odontoid peg was 11.10 mm (. sd.  1.0) in the sagittal plane and 10.00 mm (. sd. 1.07) in the coronal plane. In order to calculate the necessary screw length using 3.5 mm cannulated screws, 1.5 mm should be added to the measured odontoid peg length when anatomical reduction seems possible. The cross-section of the odontoid peg is not circular but slightly elliptical, with a 10% greater diameter in the sagittal plane. In the majority of cases (70.5%) the odontoid peg offers enough room for two 3.5 mm cannulated cortical screws. Cite this article: Bone Joint J 2013;95-B:536–42

Fractures of the odontoid peg are common spinal injuries in the elderly. This study compares the survivorship of a cohort of elderly patients with an isolated fracture of the odontoid peg versus that of patients who have sustained a fracture of the hip or wrist. A six-year retrospective analysis was performed on all patients aged > 65 years who were admitted to our spinal unit with an isolated fracture of the odontoid peg. A Kaplan–Meier table was used to analyse survivorship from the date of fracture, which was compared with the survivorship of similar age-matched cohorts of 702 consecutive patients with a fracture of the hip and 221 consecutive patients with a fracture of the wrist. A total of 32 patients with an isolated odontoid fracture were identified. The rate of mortality was 37.5% (n = 12) at one year. The period of greatest mortality was within the first 12 weeks. Time made a lesser contribution from then to one year, and there was no impact of time on the rate of mortality thereafter. The rate of mortality at one year was 41.2% for male patients (7 of 17) compared with 33.3% for females (5 of 15). . The rate of mortality at one year was 32% (225 of 702) for patients with a fracture of the hip and 4% (9 of 221) for those with a fracture of the wrist. There was no statistically significant difference in the rate of mortality following a hip fracture and an odontoid peg fracture (p = 0.95). However, the survivorship of the wrist fracture group was much better than that of the odontoid peg fracture group (p < 0.001). Thus, a fracture of the odontoid peg in the elderly is not a benign injury and is associated with a high rate of mortality, especially in the first three months after the injury. Cite this article: Bone Joint J 2014;96-B:88–93

Odontoid fracture of the second cervical vertebra (C2) is the most common spinal fracture type in elderly patients. However, very little is known about the biomechanical fracture mechanisms, but could play a role in fracture prevention and treatment. This study aimed to investigate the biomechanical competence and fracture characteristics of the odontoid process. A total of 42 human C2 specimens (14 female and 28 male, 71.5 ± 6.5 years) were scanned via quantitative computed tomography, divided in 6 groups (n = 7) and subjected to combined quasi-static loading at a rate of 0.1 mm/s until fracturing at inclinations of −15°, 0° and 15° in sagittal plane, and −50° and 0° in transverse plane. Bone mineral density (BMD), specimen height, fusion state of the ossification centers, stiffness, yield load, ultimate load, and fracture type according to Anderson and d'Alonzo were assessed. While the lowest values for stiffness, yield, and ultimate load were observed at load inclination of 15° in sagittal plane, no statistically significant differences could be observed among the six groups (p = 0.235, p = 0.646, and p = 0.505, respectively). Evaluating specimens with only clearly distinguishable fusion of the ossification centers (n = 26) reveled even less differences among the groups for all mechanical parameters. BMD was positively correlated with yield load (R² = 0.350, p < 0.001), and ultimate load (R² = 0.955, p < 0.001), but not with stiffness (p = 0.070). Type III was the most common fracture type (23.5%). These biomechanical outcomes indicate that load direction plays a subordinate role in traumatic fractures of the odontoid process in contrast to BMD which is a strong determinant of stiffness and strength. Thus, odontoid fractures appear to result from an interaction between load magnitude and bone quality

Aims. Rates of mortality as high as 25% to 30% have been described following fractures of the odontoid in the elderly population. The aim of this study was to examine whether easily identifiable variables present on admission are associated with mortality. . Patients and Methods. A consecutive series of 83 elderly patients with a fracture of the odontoid following a low-impact injury was identified retrospectively. Data that were collected included demographics, past medical history and the results of blood tests on admission. Radiological investigations were used to assess the Anderson and D’Alonzo classification and displacement of the fracture. The mean age was 82.9 years (65 to 101). Most patients (66; 79.5%) had a type 2 fracture. An associated neurological deficit was present in 11 (13.3%). All were treated conservatively; 80 (96.4%) with a hard collar and three (3.6%) with halo vest immobilisation. Results. The rate of mortality was 16% (13 patients) at 30 days and 24% (20 patients) at one year after injury. A low serum level of haemoglobin and the presence of a neurological deficit on admission were independent predicators of mortality at 30 days on binary logistic regression analysis. A, low level of haemoglobin, admission from an institution, a neurological deficit and type 3 fractures were independent predictors of mortality at one year. . Conclusion. We suggest that these easily identifiable predictors present on admission can be used to identify patients at high risk and guide management by a multidisciplinary team. Cite this article: Bone Joint J 2017;99-B:116–21

Fractures of the odontoid peg are relatively common in elderly people. Often they are minimally displaced and can be treated with a collar. However, a fracture which is displaced significantly may be difficult to manage. We describe the case of an 80-year-old man with a fracture of the odontoid peg which was completely displaced and caused respiratory distress. After initial closed reduction and application of a halo jacket, open and internal fixation was undertaken and relieved his symptoms. It is a safe and effective way to manage this injury

The purpose of this study was to propose a new classification based on the structural, anatomical and biomechanical properties of the odontoid process, to evaluate the outcome and to suggest the adequate treatment in relation to the specific fracture type. The files of 97 patients with odontoid process fractures admitted to our institution were reviewed. The external and internal anatomy of the axis has been studied. The fractures were classified according to the proposed new classification. The method was tested for reliability and validity. Mean follow-up was 14 years. Intraobserver and interobserver agreement was excellent with intraclass correlation coefficients at levels of 0.98 and 0.85 respectively. Four types of odontoid process fractures are distinguished; type A fractures are avulsion fractures involving the tip of the odontoid; type B fractures are fractures of the neck between the lower edge of the transverse ligament and the line connecting the medial corners of the upper articular facets of the axis; type C fractures involve the area between the previously mentioned line and the base of the odontoid process (type C1) or extend to the body of the axis (type C2); type D fractures are complex fractures involving more than one level of the odontoid process. Classification of odontoid process fractures has to be reconsidered as novel imaging technology has shown new patterns of fractures. Computed tomography scan with image reconstruction is mandatory. The analysis of the imaging data in the present study justifies the new classification

Between 1982 and 2000, 37 cases of fractures of the odontoid process were treated at Hirosaki University Hospital. There were 16 females and 21 males, with an average age of 43.9 and 37.7 respectively. Twenty-three of 37 were type II and 14 were type III by the classification of Anderson and D’Alonzo. Eight of type II were old fractures. Nineteen of them were injured in traffic accidents, 9 in accidental falls from a height, 4 by falling down, 2 in lumbering accidents and 3 by unknown causes. Severe neurological disorders were recognized in 7, mild in 12 and 22 had no neurological disorders. Neurological disorders were correlated with SAC (space available for spinal cord) at C1-2. Twenty-two of type II (95.7%) and 10 of type III (71%) were treated surgically. Surgical methods were anterior screw fixation of the odontoid process in 7, anterior atlanto-axial joint fixation in 3, posterior atlanto-axial joint fixation in 5, posterior occipito-cervical fusion in 3, anterior and posterior combined fixation of the atlanto-axial joint in 2 and others in 2. Bone union was obtained in 18 (81.8%) of type II and 10 (100%) of type III by the primary operations. There was no nonunion in anterior screw fixation cases. Nonunion occured in one of type II (100%) and 2 of type III (50%) treated nonoperatively. Two of them were operated for nonunion. One of them remained nonunion by two additional operations. No case of nonunion showed neurological deterioration for 91.8 months after treatment on average. Anterior direct screw fixation of the odontoid process is superior to the other methods in the point of immobilization of the odontoid fragment without limiting the motion of the atlanto-axial joint. We recommend anterior direct screw fixation of the odontoid process as a first choice of the surgical method for fresh fractures of the odontoid process in cases with reduced fragments

Background. Fractures of the odontoid peg are one of the commonest spinal injuries in the elderly population. In this population there is a higher risk of morbidity and mortality as a result of the injury. The magnitude of this risk has not been quantified in the literature. Aim. To show a survivorship analysis in a cohort of elderly patients with odontoid peg fractures. Method and Materials. A 6-year retrospective analysis was performed on all patients >65 years old admitted to a spinal unit with an isolated odontoid peg fracture. Actuarial (Life-Table) analysis was used to estimate survivorship from the date of fracture. Results. A total of 32 patients > 65 years of age with isolated odontoid peg fractures were identified. There were 17 male and 15 female. A low velocity mechanical fall was the commonest cause for the injury. The average age for the females was 86.7 years and for the males 78 years. The age distribution was unimodal in both sex, the greatest number occurring for the females in the 85-94 year age group and 75-84 years for the males. Overall, it was estimated that only 62.5 % would be alive by one year. The period of greatest mortality was within the first 12 weeks, a lesser contribution from then to one year, and had no impact on mortality thereafter. Males appeared to suffer a heavier mortality than females within the first year. At one year the male survival rate had fallen to 58.8% compared with a female rate of 66.6%. Conclusion. We observed that odontoid peg fractures in the elderly are not benign injuries and are a cause of high mortality rates within the first three months of the injury. Patients who survived to one year following the injury were observed to have their risk return to age and sex matched rates for this population

Background. Fractures of the odontoid peg are one of the commonest cervical spinal injuries in the elderly population. In this population there is a higher risk of morbidity and mortality as a result of the injury. The magnitude of the mortality risk has not been quantified in the literature. Aim. To show a survivorship analysis in a cohort of elderly patients with odontoid peg fractures. Method & Materials. A 6-year retrospective analysis was performed on all patients >65 years old with isolated odontoid peg fracture. Kaplan-Meir curve was used to estimate survivorship from the date of fracture. Results. A total of 32 patients witha mean age of 82.1 years were analysed. There were 17 male and 15 female with an average follow-up of 20.4 months. A low velocity mechanical fall was the commonest cause for the injury in 93.7% of cases. 81% of cases were treated with rigid collar immobilsation. Overall, it was estimated that only 62.5 % would be alive by one year. The period of greatest mortality was within the first 12 weeks, a lesser contribution from then to one year, and had no impact on mortality thereafter. Multivariate logistic regression demonstrated that age (P= 0.02) was significant factor with an odds ratio of 1.2. There was no significant relationship among gender or treatment with the occurrence of an adverse event. Conclusion. We observed a 3 month and one year mortality rates of 255 and 37.5% respectively. Odontoid peg fractures in the elderly are not benign injuries and are a cause of high mortality rates within the first three months of the injury. Patients who survived to one year following the injury were observed to have their risk return to age and sex matched rates for this population

Odontoid synchondral fractures are considered the most common type of fracture, amounting TO 10% of all subaxial injuries in the under 7 demographic. This injury occurs as typically the result of hyperflexion. Most odontoid fractures in children below 7 years of age involves the odontoid synchondrosis. The following is a report of the management of paediatric synchondral fractures in 2 patients who presented to the Children's Hospital Westmead in 2010. Both patients had displaced synchondral odontoid fractures which were managed by indirect reduction and halo traction. In both patients an anatomical alignment was achieved and maintained. Follow-up was 6 and 9 months respectively and the patients were assessed both clinically and radiologically. We feel the use of the “double mattress” technique is a valuable tool, as a means of achieving and maintaining occipitocervical extension, necessary, in the treatment of odontoid synchondral fractures

We treated 183 patients with fractures of the odontoid process (109 type II, 74 type III) non-operatively. Union was achieved in 59 (54%) with type-II fractures. All type-III fractures united, but in 16 patients union was delayed. There was no correlation between union and the clinical or radiological outcome of the fractures. Selective vertebral angiography, carried out in 18 patients ten with acute fractures and eight with nonunion, showed that the blood supply to the odontoid process was not disrupted. Studies on ten adult axis vertebrae at post-mortem showed that the difference in the surface area between type-II and type-III fractures was statistically significant. Our findings show that an age of more than 40 years, anterior displacement of more than 4 mm, posterior displacement and late presentation contribute towards nonunion of type-II fractures

Fractures of the odontoid in children with an open basilar synchondrosis differ from those which occur in older children and adults. We have reviewed the morphology of these fractures and present a classification system for them. There were four distinct patterns of fracture (types IA to IC and type II) which were distinguished by the site of the fracture, the degree of displacement and the presence or absence of atlantoaxial dislocation. Children with a closed synchondrosis were classified using the system devised by Anderson and D’Alonzo. Those with an open synchondrosis had a comparatively lower incidence of traumatic brain injury, a higher rate of missed diagnosis and a shorter mean stay in hospital. Certain subtypes (type IA and type II) are likely to be missed on plain radiographs and therefore more advanced imaging is recommended. We suggest staged treatment with initial stabilisation in a Halo body jacket and early fusion for those with unstable injuries, severe displacement or neurological involvement

Purposes of the study. The most common fracture of the cervical spine in the elderly population is a fracture of the odontoid peg. Such fractures are usually not displaced and these are commonly treated non-operatively. Rarely though, peg fractures are displaced and then their management is less straightforward. This is in part because the group of patients who sustain them frequently have complex and pre-existing medical co-morbidities and in part because a new neurological injury may have been sustained as a result of the peg fracture itself. Many options for the management of displaced peg fractures, both operative and non-operative have been described in the literature and discussion continues as to which technique is superior and in which patient population. The purpose of this study was to follow-up those patients who were managed operatively in our unit between 2007 and 2009. Methods and Results. We present our case series of 4 patients who sustained significantly displaced fractures of the odontoid peg with accompanying neurological injury, who were treated with posterior stabilisation using the Harms technique. Conclusions. We have found this method to be safe and reliable. It not only yields a good surgical outcome, but allows patients' rehabilitation to be optimised, maximising functional improvement. We believe the technique is superior to anterior stabilisation in this patient population because it utilises superior posterior bone quality and mechanical fixation. The approach in our unit is to treat elderly patients with displaced odontoid peg fractures according to the same principles as would be followed in managing those that have disabling injuries such as fractures of the femoral neck; early stabilisation and early mobilisation in those patients whose co-morbidities allow it

1. Fifty-one cases of fracture of the odontoid have been analysed. Forty were reported by other surgeons; eleven were new cases first reported by us. 2. Fracture of the odontoid in young children is an epiphysial separation. It occurs up to the age of seven years. As in epiphysial separations elsewhere, it unites readily, and remodelling occurs when reduction has been incomplete, so that normal anatomy is restored. 3. In adults forward displacement is twice as common as backward displacement. 4. Immediate paralysis is commoner if backward displacement occurs, but late neurological disorders are seen only after fractures with forward displacement. 5. Failure of bony healing is not dangerous if treatment has resulted in firm fibrous union, for there is neither excessive abnormal mobility nor progressive subluxation, either of which could injure the spinal cord or medulla. Neurological disorders developing after the fracture are the result of mobility from inadequate early treatment. It is the results of inadequate early treatment which have given this fracture a sinister reputation. 6. The fracture should be reduced by skeletal traction through a skull caliper. The reduction should be maintained for six weeks by continuous traction, and this should be followed by a period of six weeks in a plaster. 7. The increasing definition of the fracture-line seen in the radiographs of some patients indicates non-union

Aim: To evaluate the necessity for further radiological investigation in patients with suspicion of rotatory subluxation of the atlanto-axial complex on plain radiography following acute cervical trauma. To outline guidelines for assessment of patients with atlanto-axial asymmetry on plain radiography. Methods: A retrospective review of all patients who had undergone atlanto-axial CT scanning as a result of radiographic C1–C2 asymmetry following cervical spine trauma in the 3 year period from January 1999 to December 2001. The plain X-ray and CT images were reviewed retrospectively and correlated with their clinical presentation and outcome by the senior author. Results: Twenty-eight patients were included in the study. Acute cervical spine trauma had occurred most commonly following a road traffic accident. No patient was found to have acute cervical spine torticollis or severe cervical pain. Patients age ranged from 21–44 years (M:F – 15:13). All patients were found to have atlanto-odontoid asymmetry on initial plain X-ray. No patients were found to have rotatory subluxation on CT images. 3 patients were found to have minor degrees (< 10°) of rotation on the CT scan which is within normal limits. 9 patients (32%) were found to have congenital odontoid lateral mass asymmetry. All patients were treated conservatively and had no further intervention. All plain radiographs were then assessed to determine the underlying reason for asymmetry. In 19 cases the orientation of the radiographic beam in combination with head rotation was found to be at fault. Conclusion: Rotatory subluxation of the cervical spine is a rare but serious condition in the adult. The condition is suspected radiologically in the presence of odontoid lateral mass asymmetry on open mouth view. The application of ATLS principles in the initial assessment of trauma patients has resulted in a significant increase in the number of radiological examinations performed. This has led inevitably to an increase in the number of anomalies identified. An average of 400 c-spine X-rays per year are performed for trauma in our casualty department. In this study, we have identified 9 patients out of a total of 29 with congenital odontoid lateral mass asymmetry over a 3 year period. This represents approximately 0.75% of the cervical spine X-rays and should be considered in the differential diagnosis following acute cervical trauma. We outline guidelines for recognising benign atlanto-axial asymmetry

Background: Type II odontoid fractures are the commonest upper cervical spine injury in the elderly, following minor falls. Structural heterogeneity within the axis with deficiency of bone mass in the base of the odontoid process has been attributed for these fractures. Aims: To analyse whether osteoporosis at the dens-body junction is directly related to the occurrence of odontoid fractures in the elderly. Material and Methods: We studied the reformatted CT scan images of 36 patients over the age of 70 years who had cervical spine injuries following minor trauma. In all these patients the severity of osteoporosis at the dens-body junction, and in the peg and body of axis were evaluated. The osteoporosis was graded into none, mild, moderate and severe. Statistical analysis was performed using Pearson’s Chi-square test to find the significance of osteoporosis at the dens-body junction in producing Type II odontoid fractures in the elderly. Results: Type II odontoid fractures was seen in 21 patients. Eleven of the 21 patients with Type II fractures and eight of the 15 patients with no Type II odontoid fractures had significant osteoporosis at the dens-body junction. Five patients with Type II fracture and eight patients with no Type II fractures had significant osteoporosis at the dens and body of axis. Statistical analysis showed that the osteoporosis at the dens-body junction was not significant in patients with Type II odontoid fracture compared to those with no Type II odontoid fracture (χ. 2. = 1.1; df = 3, p = 0.78). Conclusions: Eventhough osteoporosis is one of the factors that increase the incidence of Type II fractures of the odontoid process in the elderly, it is not a direct aetiological factor

Background: Type II odontoid fractures are the commonest upper cervical spine injury in the elderly, following minor falls. Structural heterogeneity within the axis with deficiency of bone mass in the base of the odontoid process has been attributed for these fractures. Aims: To analyse whether osteoporosis at the dens-body junction is directly related to the occurrence of odontoid fractures in the elderly. Material and Methods: We studied the reformatted CT scan images of 36 patients over the age of 70 years who had cervical spine injuries following minor trauma. In all these patients the severity of osteoporosis at the dens-body junction, and in the peg and body of axis were evaluated. The severity was graded into none, mild, moderate and severe, depending on the cortical thickness, trabecular pattern, and the size of holes (absence of trabeculae) using sagittal, coronal and transverse sections of CT scan pictures. The osteoporosis was graded into none, mild, moderate and severe. Statistical analysis was performed using Pearsons Chi-square test to find the significance of osteoporosis at the dens-body junction in producing Type II odontoid fractures in the elderly. Results: Type II odontoid fractures was seen in 21 patients. Eleven of the 21 patients with Type II fractures and eight of the 15 patients with no Type II odontoid fractures had significant osteoporosis at the dens-body junction. Five patients with Type II fracture and eight patients with no Type II fractures had significant osteoporosis at the dens and body of axis. Statistical analysis showed that the osteoporosis at the dens-body junction was not significant in patients with Type II odontoid fracture compared to those with no Type II odontoid fracture (Chi-square value = 1.1; df = 3, p = 0.78). Conclusions: Eventhough osteoporosis is one of the factors that increase the incidence of Type II fractures of the odontoid process in the elderly, it is not a direct aetiological factor

High definition computed cervical myelograms have been made in flexion and extension in 13 patients with Morquio-Brailsford's disease. We observed that: 1) odontoid dysplasia was present in every case, with a hypoplastic dens and a detached distal portion which was not always ossified; 2) atlanto-axial instability was mild, and anterior atlanto-axial subluxation was absent in most cases; 3) severe spinal cord compression, when present, was due to anterior extradural soft-tissue thickening; 4) this compression was not relieved by flexing or extending the neck and was manifested early in life; 5) posterior occipitocervical fusion resulted in disappearance of the soft-tissue thickening and normalisation of subsequent development of the dens. We conclude that the severity of neurological involvement at the craniovertebral junction was determined by soft-tissue changes, not by the type of odontoid dysplasia nor by subluxation. Posterior occipitocervical fusion proved to be an effective treatment