In this paper, a modular designed automatic screw tightening shaft system, which is based on enhanced variable gain PID control, is proposed. Designed for the autonomous screw tightening operation, the screw tightening shaft enjoys huge potential for industry application. The screw tightening shaft and the screw tightening process are both mathematically modeled as an uncertain feedback system ...

The purpose of this study was to determine the influence of gender, screw design, and the approach on maximal screw length in scaphoid fracture fixation. Measurements were performed on 3D reconstructions of 20 CT scans of normal scaphoids. A comparison was made between 15 different available screw designs and between volar and dorsal screw placement. The length of the scaphoid along its central...

STUDY DESIGN A prospective self-controlled study. OBJECTIVE The aim of the present study was to compare the application and clinical outcomes of transposterior arch lateral mass screw and lateral mass screw fixation of the atlas in the treatment of atlantoaxial instability. SUMMARY OF BACKGROUND DATA Atlas posterior screw fixation techniques comprise transposterior arch lateral mass screw f...

STUDY DESIGN A biomechanical spine model was used to evaluate the impact of screw design on screw-vertebra interface loading during simulated surgical corrections of adult scoliosis. OBJECTIVES To evaluate differences in screw-vertebra interface forces during adult scoliosis correction between favored angle (FA) screws with extension tabs and standard polyaxial screws while varying deformity ...

BACKGROUND It has been observed clinically that the Z-effect is a potential cause of failure of an intramedullary nail with two cephalic screws. It describes the migration behavior of the cephalic screws in the femoral head. The primary objective was to examine different cephalic screw configurations and test the load distribution between them as a function of their relative placement and their...

BACKGROUND It was reported that expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) could be used to increase screw stability in osteoporosis. However, there are no studies comparing the two kinds of screws in vivo. Thus, we aimed to compare biomechanical and interfacial performances of EPS and PMMA-PS in osteoporotic sheep spine. METHODOLOGY/PRINCIPAL F...

BACKGROUND Pedicle screw pullout due to poor bone quality, mainly caused by osteoporosis, is a common problem in spine surgery. Special implants and techniques, especially PMMA augmentation, were developed to improve the fixation of pedicle screws. PMMA injection into a pilot hole or through a screw involves the same risks as vertebroplasty or kyphoplasty, regardless of the technique used. Espe...

background: at present, there is no consensus on an appropriate treatment modality for intertrochanteric fractures in the elderly with background diseases. the aim of the present study was to compare treatment outcomes of intertrochanteric fractures reduced with dynamic hip screws (dhs) and bipolar hemiarthroplasty in elderly patients with background medical conditions. methods: in this randomi...

conclusions we recommend the additional 2d-fluoroscopic tangential view for detection of screw misplacements caused by overlength, with penetration on the dorsal cortical surface of the distal radius, predominantly observed for the most lateral screw position. the use of intraoperative 3d fluoroscopy did not become accepted in our clinical routine, due to the technical demanding and time consum...

The paper begins with a review of screw algebra including dual numbers, unit line vectors, dual vectors, screws, line coordinates, and screw coordinates and summarizes the essential rules of operation for screw algebra. A significant advantage of the algebra is that geometric, kinematic, and dynamic equations of a rigid body can be expressed in a concise and compact form. Several physical quant...