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

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

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

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

Purpose of the study: Cases of serious trauma to the cervical spine requiring surgical management in older subjects goes in hand with the general trend towards a more active elderly population. We analyzed retrospectively our experience with 28 patients cared for in our unit from 1990 to 1999. Patients and methods: Mean age of these 11 women and 17 men was 73 years (range 65–93). High-energy trauma was the cause of the cervical injury in 12 patients (42%). The others were victims of falls in their homes. This later cause explains the long delay to care (21 days on the average with a range from zero days to six months). The six patients who had injuries to the upper cervical spine had fractures of the odontoid process secondary to a fall. The mobile segment of the spine was involved in most of the injuries involving the lower cervical spine (eleven severe sprains and six dislocations) resulting from high-energy trauma in half of the cases. These injuries occurred above an osteoarthritic block. Half of the patients had neurological complications: eleven immediate, three late. The Franckel classification was: A=2, C=4, D=7. The same repair technique was used for the upper an lower cervical spine. Five of the six fractures of the odontoid process were fixed with a Bölher screw, and one with posterior fusion. An anterior graft with plate fixation was used 18 times for the lower spine. Roy Camille posterior fixation was used four times because of the irreducible nature of the fracture or because of the need for posterior fusion. Results: Morbidity was high. Seven patients (25%) had serious cardiorespiratory complications leading to death in five patients. All these patients had neurological sequelae (Franckel A and C). For the other patients, the postoperative period was uneventful and similar to that observed in younger patients (immobilization, neurological recovery, consolidation). Discussion: The high frequency of upper cervical spine trauma observed in our series is also reported in the literature. It increases with age. The frequency of neurological involvement was identical to that observed by Roth and Spivak. Prognosis was poor in case of neurological involvement. The appropriateness of surgery in Franckel A patients may be questionable. Surgery cannot avoid the risk of mortality in these patients but it can enable mobilisation and nursing care, avoiding the need for a halo jacket. Conclusion: Spinal trauma in the elderly can be managed similarly to that in young adults, at least in cases without major neurological involvement

Introduction and Aims: Odontoid fractures are quite common in the elderly following minor falls. As there are a few articulations in the upper cervical spine, degeneration in any one particular joint may affect the biomechanics of loading of the upper cervical spine. We aimed to analyse the pattern and relationship of odontoid fractures to the upper cervical spine osteoarthritis in the elderly. Method: Between July 1999 and March 2003, 185 patients had CT scan of the cervical spine for cervical spine injuries. Twenty-three out of 47 patients over the age of 70 years had odontoid fractures. The CT scan pictures of these patients were studied to analyse the type of fracture and its displacement, the severity of osteoarthritis in each articulation in the upper cervical spine, namely lateral atlantoaxial, atlantooccipital, atlantoodontoid and subaxial facetal joints, evaluation of osteopenia in the dens-body junction and in the body and odontoid process of the axis, and calcification of the ligaments. Results: Twenty-one of the 23 patients had Type II odontoid fracture with posterior displacement in seven (33.3%) and posterior angulation in nine (42.8%) patients. In these patients with Type II dens fracture, the atlantodens interval was obliterated in 19 (90.48%) patients, with only two of them (9.52%) having lateral atlantoaxial osteoarthritis. Conclusion: Type II fracture is the commonest odontoid fracture in the elderly. Posterior displacement of the fracture is common in elderly, unlike the younger population. There is a significant relationship between the upper cervical spine osteoarthritis, apart from osteopenia, to the incidence of Type II odontoid fractures. Significant atlantoodontoid osteoarthritis in the presence of normal lateral atlantoaxial joints increases the risk of sustaining Type II odontoid fracture

Introduction: The intricate biomechanical function of the alar ligaments in the craniocervical articular complex has received considerable scientific attention. While allowing the greatest range of axial rotation of the entire spine with 40° to each side, definitive restraint at the extremes of motion by the alar ligaments is of vital importance. Detailed knowledge of the function of these ligaments is essential for comprehending the factors leading to potentially devastating instability. Methods: Bilateral alar ligaments including the bony entheses were removed from six adult cadavers aged 65–89 years within 48 hours of death. All specimens were judged to be free of abnormalities with the exception of non-specific degenerative changes. Dimensions of the alar ligaments were measured. Schematic multipla-nar reconstruction of axial atlanto-axial rotation was done in the transverse and frontal planes for the neutral position and for rotation to 30° and 40° in the neutral plane to assess schematic fibre elongation during axial rotation and to determine the change in the angle of insertion at the odontoid and condylar entheses. This was repeated with a 1mm descending translation of the occipital condyles at 30° and 3mm descending translation of the occipital condyles at 40° rotation. Results: The average diameter of the odontoid process measured in the sagittal plane was 10.6 mm (SD 1.1). The longest fibre length was measured from the posterior border of the odontoid enthesis to the posterior border of the condylar enthesis with an average of 13.2 mm (SD 2.5) and the shortest between the lateral (anterior) border odontoid enthesis and the anterior condylar enthesis with an average of 8.2 mm (SD 2.2). Attachment areas of the enthesis revealed an average of 60 mm2 (SD 12.4) for the odontoid and 50,6 mm2 (SD12.6) for the condylar enthesis. Schematic fibre elongation reaches 27,1% for the longest fibres at 40° axial rotation. This is reducible to 7,8% elongation by 3mm caudal translation of the atlas. Conclusions: This theoretical model confirms that the bi-convex shape of atlanto-axial joint allows for rotation when modelled with oblique alar ligaments. This provides baseline for further research with functional MRI which will be useful for rheumatoid and post traumatic spine