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The stability of a burst fracture of the atlas (Jefferson's fracture) should be determined in order to decide upon the appropriate treatment. Unstable fractures include those with a rupture of the transverse ligament, or those in which union has been incomplete despite treatment. An occiput-to-C2 or in atlantoaxial arthrodesis may be indicated.

Cervical traction of one-third the person's weight was applied for 3 minutes to normal subjects. The mean and standard deviation of displacement and rotation between adjacent cervical vertebra was calculated in the sagittal plane. The average separation between adjacent vertebra was 0.7 mm with a standard deviation of 0.5 mm. The average angular motion between adjacent vertebra was 0.9 degrees with a standard deviation of 2.4 degrees.

Cast wedging using vector and geometrical analysis demonstrated that the open wedge produces distraction of the fracture, the closing wedge shortening, and that the opening--closing wedge can perfectly correct skeletal deformity. The level of wedging should lie at the axis intersection, i.e., at the intersection of the long axes of the 2 major fracture fragments. An open wedge at the axis intersection is recommended for tibial shaft fractures immobilized with long leg casts; an opening--closing wedge at the axis intersection, for fractures immobilized with "pins and plaster".

Torisonal, compression, and bending forces were applied to long oblique fractures of rabbit tibiae that were fixed with 2 screws in different positions. Torison, bending and compression tests were applied to the tibiae. Results for torsional load show that screws should be perpendicular to the fracture plane. For compressive load, screws should be fixed perpendicular to the long axis of the bone. When bending moments are applied in the same plane as the plane of the screws, there is no preferred position of the screws across the fracture. When bending moments are applied perpendicular to the plane of the screws, screws should be positioned perpendicular to the fracture plane.

Torisonal, compression, and bending forces were applied to long oblique fractures of rabbit tibiae that were fixed with 2 screws in different positions. Torison, bending and compression tests were applied to the tibiae. Results for torsional load show that screws should be perpendicular to the fracture plane. For compressive load, screws should be fixed perpendicular to the long axis of the bone. When bending moments are applied in the same plane as the plane of the screws, there is no preferred position of the screws across the fracture. When bending moments are applied perpendicular to the plane of the screws, screws should be positioned perpendicular to the fracture plane.

Cervical traction of one-third the person's weight was applied for 3 minutes to normal subjects. The mean and standard deviation of displacement and rotation between adjacent cervical vertebra was calculated in the sagittal plane. The average separation between adjacent vertebra was 0.7 mm with a standard deviation of 0.5 mm. The average angular motion between adjacent vertebra was 0.9 degrees with a standard deviation of 2.4 degrees.