Background. Screw-retained restorations are favored in some clinical situations such as limited inter-occlusal spaces. This study was designed to compare stresses developed in the peri-implant bone in two different types of screw-retained restorations (segmented vs. non-segmented abutment) using a finite element model. Methods. An implant, 4.1 mm in diameter and 10 mm in length, was placed in t...

P edicle screw fixation for spinal stabilization is now commonplace in spine surgery. Traditionally, pedicle screws are placed through a trajectory in which screw insertion utilizes a transpedicular path through the axis of the pedicle, either paralleling the end plate, as in the straightforward trajectory, or following the anatomic axis of the pedicle with an approximately 22° cephalocaudal tr...

Current surgical treatment of idiopathic scoliosis involves the use of various segmental instrumentation. Various pedicle screws have allowed for improved correction. Although monoaxial screws have improved rotational control compared with polyaxial screws, their use may increase screw-bone interface or vertebral endplate forces if not inserted in an exactly straight trajectory. Uniaxial screws...

Aims Bone fracture fixation in orthopaedic surgery occurs with the use of implants, such as bone screws. Screws are tightened, typically manually, with the level of tightening depending on surgeons’ manual feel. However, this subjective insertion torque control can lead to overtighening and screw stripping 1 . Previously our group has shown that stripping torque can be predicted based on the to...

An experimental study of the fatigue life of cortical bone screws under conditions which stimulated in vivo usage was performed. The two most important factors influencing fatigue life were axial screw tension (the force normal of the plate to bone) and the cyclic shearing load. All screws failed at the root of the thread in the interface between the plate and the bone. A modified screw design ...

BACKGROUND AND PURPOSE Sclerostin is produced by osteocytes and is an inhibitor of bone formation. Thus, inhibition of sclerostin by a monoclonal antibody increases bone formation and improves fracture repair. Sclerostin expression is upregulated in unloaded bone and is downregulated by loading. We wanted to determine whether an anti-sclerostin antibody would stimulate metaphyseal healing in un...

orthodontic miniscrews are widely used as temporary anchorage devices to facilitate orthodontic movements. miniscrew loosening is a common problem, which usually occurs during the first two weeks of treatment. macrodesign can affect the stability of a miniscrew by changing its diameter, length, thread pitch, thread shape, tapering angle and so on. in this study, a 3-d finite element analysis wa...

BACKGROUND This study sought to determine whether several metatarsophalangeal (MTP) fusion techniques require complete immobilization or if some level of weight-bearing could be recommended after surgery. A comparison of synthetic composite to actual bone was included in order to examine the validity of the testing conditions. METHODS Four MTP fusion modalities were tested in synthetic compos...

The strength of pedicle screws attachment to the vertebrae is an important factor affecting their motion resistance and long term performance. Low bone quality, e.g. in osteopenic patients, keeps the screw bone interface at risk for subsidence and dislocation. In such cases, bone cement could be used to augment pedicle screw fixation. But its use is not free of risk. Therefore, clinicians, espe...

BACKGROUND In tibial tubercle transfer (TTT) procedures, the osteotomized and transferred tibial tubercle is usually fixed into the host bone using metal screws. PURPOSE To compare the strength of fixation provided by a single bioabsorbable screw versus a metal screw for TTT. STUDY DESIGN Controlled laboratory study. METHODS Twenty-two pairs of human cadaveric tibiae were used to compare ...