Remote Fractures Research Articles

Direct anterior screw fixation for recent and remote odontoid fractures

Object The management of odontoid fractures remains controversial. Only direct anterior screw fixation provides immediate stabilization of the spine and may preserve normal C1–2 motion. To determine the indications, optimum timing, and results for direct anterior screw fixation of odontoid fractures, the authors reviewed the surgery-related outcome of patients who underwent this procedure at two institutions. Methods One hundred forty-seven consecutive patients (98 males and 49 females) who underwent direct anterior screw fixation for a recent fracture (< 6 months postinjury [129 patients]) or remote (≥ 18 months postinjury [18 patients]) Type II (138 cases) or III (nine cases) odontoid fractures at the University of Utah (94 patients) and National Institute of Traumatology in Budapest, Hungary (53 patients) between 1986 and 1998 are included in this study (mean follow-up period 18.2 months). Data obtained from clinical examination, review of hospital charts, operative findings, and imaging studies were used to analyze the surgery-related results in these patients. In patients with recent fractures there was an overall bone fusion rate of 88%. The rate of anatomical bone fusion of recent fractures was significantly (p ≤ 0.05) higher in fractures oriented in the horizontal and posterior oblique direction (as compared with anterior oblique), but this finding was independent (p ≥ 0.05) of age, sex, number of screws placed (one or two), and the degree or the direction of odontoid displacement. In patients with remote fractures there was a significantly lower rate of bone fusion (25%). Overall, complications related to hardware failure occurred in 14 patients (10%) and unrelated to hardware in three patients (2%). There was one death (1%) related to surgery. Conclusions Direct anterior screw fixation is an effective and safe method for treating recent odontoid fractures (< 6 months postinjury). It confers immediate stability, preserves C1–2 rotatory motion, and achieves a fusion rate that compares favorably with alternative treatment methods. In contradistinction, in patients with remote fractures (≥ 18 months postinjury) a significantly lower rate of fusion is found when using this technique, and these patients are believed to be poor candidates for this procedure.

Primary and remote fractures around underground cavities : Carter, B J, Lajtai, E Z, Petukhov, A Int J Num Anal Meth GeomechV15, N1, Jan 1991. P21–40

Primary and remote fractures around underground cavities : Carter, B J, Lajtai, E Z, Petukhov, A Int J Num Anal Meth GeomechV15, N1, Jan 1991. P21–40

Primary and remote fracture around underground cavities

AbstractThe development of fractures around cavities in rock is examined using physical and numerical models. In uniaxial compression, fracture proceeds from primary through remote to compressional (slabbing) fracture. There is a wide stress interval where the only event is the stable propagation of the primary fracture. When the crack length becomes equal to about the size of the diameter of the cavity, the critical stress condition shifts to either side of the primary fracture, leading to the nucleation of remote fractures. Almost simultaneously, failure at the compressive stress concentration follows. With increasing stress, fracture in the remote region is seen to extend away from and towards the compressive region, eventually merging with the slabbing fractures. Increasing the confining pressure shortens the stress interval during which primary fracture is the only process and shifts failure to the remote and the compressional fracture zone.

Investigation of fracture flow paths using alterant geophysical tomography

The mapping of fractures is a problem of major importance to many geotechnical projects. It is a three dimensional problem requiring the use of measurement methods with sufficient resolution and probing range to map fractures at a distance from exposed surfaces. The National Research C6uncil's report on Rock Mechanics Research Requirements [1] identified a need for major improvements in the methods used for mapping remote fractures. This article discusses a new geophysical method (Alterant Geophysical Tomography, AGT) in which tracers are forced into the in situ rock fractures to change the transmission properties of electromagnetic waves propagated between boreholes or tunnels. The theoretical advantages of the method and the results of the first experiment where it was used are also presented. This technique is analogous to the medical diagnostics technique known as X-ray fluoroscopy wherein a tracer is used to attenuate X-rays. The movement of the tracer within the digestive tract or circulatory system of the human body is monitored by measuring the attenuation of X-rays. AGT involves the transmission of an electromagnetic energy field through fractured rock before, during, and/or after a tracer is forced into the fractures. By using alterant geophysical tomography, changes induced by these tracers are mapped in the plane defined by the two boreholes. This approach is intended for geologic environments where fracture flow dominates such that the tracer penetrates the fractures but not the rock matrix.