Three-dimensional primary stability of cementless femoral stems

OBJECTIVE: This study investigates by means of a new bone-prosthesis interface motion detector whether conceptual design differences of femoral stems are reflected in their primary stability pattern. DESIGN: An in vitro experiment using a biaxial materials testing machine in combination with three-dimensional motion measurement devices was performed. BACKGROUND: Primary stability of uncemented total hip replacements is considered to be a prerequisite for the quality of bony ongrowth to the femoral stem. Dynamic motion as a response to loading as well as total motion of the prosthesis have to be considered under quasi-physiological cyclic loading conditions. METHODS: Seven paired fresh cadaveric femora were used for the testing of two types of uncemented femoral stems with different anchoring concepts: CLS stem (Spotorno) and Cone Prosthesis (Wagner). Under sinusoidal cyclic loading mimicking in vivo hip joint forces a new measurement technique was applied allowing for the analysis of the three-dimensional interface motion. RESULTS: Considerable differences between the two prostheses could be detected both in their dynamic motion and total motion behaviour. Whereas the CLS stem, due to the wedge-shaped concept, provides smaller total motions, the longitudinal ribs of the Cone prostheses result in a substantially smaller dynamic motion. CONCLUSIONS: The measuring technique provided reliable and accurate data illustrating the three-dimensional interface motion of uncemented femoral stems.

Use of straight and curved 3-dimensional titanium miniplates for fracture fixation at the mandibular angle

PURPOSE: The aim of this follow-up study was to evaluate the clinical usefulness of a new type of 3-dimensional (3D) miniplate for open reduction and monocortical fixation of mandibular angle fractures. PATIENTS AND METHODS: In 20 consecutive patients, noncomminuted mandibular angle fractures were treated with open reduction and fixation using a 2 mm 3D miniplate system in a transoral approach. All patients were systematically monitored until 6 months postoperatively. Among the outcome parameters recorded were infection, hardware failure, wound dehiscence, and sensory disturbance of the inferior alveolar nerve. RESULTS: The mean operation time from incision to wound closure was 65 minutes. Two patients had a mucosal wound dehiscence with no consequences. None developed an infection requiring a plate removal. All but 2 patients had normal sensory function 3 months after surgery. Plate fracture occurred in one patient in whom a preceding surgical removal of the third molar had been the reason for the mandibular fracture. In the absence of clinical symptoms, the patient declined plate removal. On final follow-up, fracture healing was considered clinically complete in all patients. CONCLUSIONS: The 3D plating system described here is suitable for fixation of simple mandibular angle fractures and is an easy-to-use alternative to conventional miniplates. The system may be contraindicated in patients in whom insufficient interfragmentary bone contact causes minor stability of the fracture.

Stability of soft tissue profile after mandibular setback in sagittal split osteotomies: a longitudinal and long-term follow-up study

PURPOSE: The aim of the study was to conduct a long-term prospective follow-up on the stability of soft tissues after bilateral sagittal split osteotomy (BSSO) with rigid internal fixation to set back the mandible. PATIENTS AND METHODS: Seventeen consecutive patients (6 females, 11 males) were re-examined 12.7 years (T5) after surgery. The precedent follow-ups included: before surgery (T1), 5 days (T2) after surgery, 6.6 months (T3) after surgery, and 14.4 months after (T4) surgery. Lateral cephalograms were traced by hand, digitized, and evaluated with the Dentofacial Planner program (Dentofacial Software, Toronto, Canada). The x-axis for the system of coordinates ran through Sella (point 0) and the line NSL -7 degrees. RESULTS: The net effect of the soft tissue chin (soft tissue pogonion) was 79% of the setback at pogonion. At the lower lip (labrale inferior) it was 100% of the setback at lower incisor position. Point B' followed point B to 99%. Labrale inferior and menton' also showed a significant backward, as well as a downward, movement (T5 to T2). Gender correlated significantly (P = .004) with the anterior displacement of point B' and pogonion' (P = .012). The soft tissue relapse 12.7 years after BSSO setback surgery at point B' was 3% and 13% at pogonion'. CONCLUSION: Among the reasons for 3-dimensional long-term soft tissue changes of shape, the surgical technique, the normal process of human aging, the initial growth direction, and remodeling processes must be considered. Growth direction positively influenced the long-term outcome of setback surgery in female compared with male patients because further posterior movement of the mandibular soft tissue occurred.

hp-dGFEM for Second-Order Elliptic Problems in Plyhedra I: Stability and Quasioptimality on Geometric Meshes

We introduce and analyze hp-version discontinuous Galerkin (dG) finite element methods for the numerical approximation of linear second-order elliptic boundary-value problems in three-dimensional polyhedral domains. To resolve possible corner-, edge- and corner-edge singularities, we consider hexahedral meshes that are geometrically and anisotropically refined toward the corresponding neighborhoods. Similarly, the local polynomial degrees are increased linearly and possibly anisotropically away from singularities. We design interior penalty hp-dG methods and prove that they are well-defined for problems with singular solutions and stable under the proposed hp-refinements. We establish (abstract) error bounds that will allow us to prove exponential rates of convergence in the second part of this work.

High-precision confocal reflection measurement for two dimensional refractive index mapping of optical fibers

We introduce a new fiber-optical approach for reflection based refractive index mapping. Our approach leads to improved stability and reliability over existing free-space confocal instruments and significantly cuts alignment efforts and reduces the number of components needed. Other than properly cleaved fiber end-faces, this setup requires no additional sample preparation. The instrument is calibrated by means of a set of samples with known refractive indices. The index steps of commercially available fibers are measured accurately down to < 10⁻³. The precision limit of the instrument is currently of the order of 10⁻⁴.

Two-Dimensional Crystallisation of Membrane Proteins and Structural Assessment

Two-dimensional (2D) crystallisation of Membrane proteins reconstitutes them into their native environment, the lipid bilayer. Electron crystallography allows the structural analysis of these regular protein–lipid arrays up to atomic resolution. The crystal quality depends on the protein purity, ist stability and on the crystallisation conditions. The basics of 2D crystallisation and different recent advances are reviewed and electron crystallography approaches summarised. Progress in 2D crystallisation, sample preparation, image detectors and automation of the data acquisition and processing pipeline makes 2D electron crystallography particularly attractive for the structural analysis of membrane proteins that are too small for single-particle analyses and too unstable to form three-dimensional (3D) crystals.