: The RUST score exhibits substantial improvements in reliability from previously published scores and produces equally reproducible results among a variety of orthopedic specialties and experience levels. Because no "gold standards" currently exist against which RUST can be compared, this study provides only the initial step in the score's full validation for use in a clinical context.

A combination of a nonlocking plate with an allograft strut (construct D) resulted in the highest stiffness of the constructs examined for treating a periprosthetic fracture around a stable femoral component of a total hip replacement.

The inferior lag screw position produced the highest axial and torsional stiffness. Anterior and posterior lag screw positions produced the lowest stiffnesses and load-to-failure. Inferior placement of the lag screw on the anteroposterior radiograph and central placement on the lateral radiographs is recommended.

No abstract

Anatomic reduction with the medial cortical contact was the stiffest construct after a simulated two-part fracture. This study affirms the concept of medial cortical support by fixing proximal humeral fractures in varus, if absolutely necessary. This may be preferable to fixing the fracture in anatomic alignment when there is a medial fracture gap.

No abstract

Femoral shaft fractures after total hip arthroplasty (THA) remain a serious problem, since there is no optimal surgical repair method. Virtually all studies that examined surgical repair methods have done so clinically or experimentally. The present study assessed injury patterns computationally by developing three-dimensional (3D) finite element (FE) models that were validated experimentally. The investigation evaluated three different constructs for the fixation of Vancouver B1 periprosthetic femoral shaft fractures following THA. Experimentally, three bone plate repair methods were applied to a synthetic femur with a 5 mm fracture gap near the tip of a total hip implant. Repair methods were identical distal to the fracture gap, but used cables only (construct A), screws only (construct B), or cables plus screws (construct C) proximal to the fracture gap. Specimens were oriented in 15 degrees adduction to simulate the single-legged stance phase of walking, subjected to 1000 N of axial force, and instrumented with strain gauges. Computationally, a linearly elastic and isotropic 3D FE model was developed to mimic experiments. Results showed excellent agreement between experimental and FE strains, yielding a Pearson linearity coefficient, R2, of 0.92 and a slope for the line of best data fit of 1.06. FE-computed axial stiffnesses were 768 N/mm (construct A), 1023 N/mm (construct B), and 1102 N/mm (construct C). FE surfaces stress maps for cortical bone showed Von Mises stresses, excluding peaks, of 0-8 MPa (construct A), 0-15 MPa (construct B), and 0-20 MPa (construct C). Cables absorbed the majority of load, followed by the plates and then the screws. Construct A yielded peak stress at one of the empty holes in the plate. Constructs B and C had similar bone stress patterns, and can achieve optimal fixation.

Biomechanical investigations of orthopedic fracture fixation constructs increasingly use analogs like the third and fourth generation composite femurs. However, no study has directly compared cortical screw purchase between these surrogates and human femurs, which was the present aim. Synthetic and human femurs had bicortical orthopedic screws (diameter=3.5 mm and length=50 mm) inserted in three locations along the anterior length. The screws were extracted to obtain pullout force, shear stress, and energy-to-pullout. The four study groups (n=6 femurs each) assessed were the fourth generation composite femur with both 16 mm and 20 mm diameter canals, the third generation composite femur with a 16 mm canal, and the human femur. For a given femur type, there was no statistical difference between the proximal, center, or distal screw sites for virtually all comparisons. The fourth generation composite femur with a 20 mm canal was closest to the human femur for the outcome measures considered. Synthetic femurs showed a range of average measures (2948.54-5286.30 N, 27.30-35.60 MPa, and 3.63-9.95 J) above that for human femurs (1645.92-3084.95 N, 17.86-24.64 MPa, and 1.82-3.27 J). Shear stress and energy-to-pullout were useful supplemental evaluators of screw purchase, since they account for material properties and screw motion. Although synthetic femurs approximated human femurs with respect to screw extraction behavior, ongoing research is required to definitively determine which type of synthetic femur most closely resembles normal, osteopenic, or osteoporotic human bone at the screw-bone interface.