Mechanical evaluation of external skeletal fixator-intramedullary pin tie-in configurations applied to cadaveral humeri from red-tailed hawks (Buteo jamaicensis).

Use of external skeletal fixator-intramedullary pin (ESF-IM) tie-in fixators is an adjustable and effective method of fracture fixation in birds. The objective of this study was to determine the contribution of each of the following parameters to the compressive and torsional rigidity of an ESF-IM pin tie-in applied to avian bones with an osteotomy gap: (1) varying the fixation pin position in the proximal bone segment and (2) increasing the number of fixation pins in one or both bone segments. ESF-IM pin tie-in constructs were applied to humeri harvested from red-tailed hawks (Buteo jamaicensis) (n=24) that had been euthanatized for clinical reasons.

Mechanical evaluation of various external skeletal fixator-intramedullary pin tie-in configurations using a tubular plastic bone model.

Use of external skeletal fixator-intramedullary pin tie-in (ESF-IM pin tie-in) fixators is an adjustable and effective method of fracture fixation in birds. The objective of this study was to evaluate the elements of the ESF-IM tie-in configuration used in birds. Ten variations of constructs were applied to a plastic bone model with a standard gap.

OP-1 augments glucocorticoid-inhibited fracture healing in a rat fracture model.

Glucocorticoids inhibit bone remodeling and fracture healing. We sought to determine whether osteogenic protein 1 (OP-1) can overcome this inhibition in a closed fracture model in the rat. Time-released prednisolone or placebo pellets were implanted subcutaneously; closed femoral fractures were created 2 weeks later in rats.

Biomechanical comparison of extended trochanteric osteotomy and slot osteotomy for femoral component revision in total hip arthroplasty.

Background: Depending upon the clinical presentation and need for exposure in revision hip arthroplasty, an extended trochanteric osteotomy or slot osteotomy could be used for removal of an inaccessible distal cement mantle, infected material, or distal fragment of a broken stem. This study is a biomechanical comparison of these two osteotomy techniques.

Methods: A press-fit femoral component with a 20-cm straight stem was implanted in each of ten synthetic femurs.

Fatigue analysis of plates used for fracture stabilization in small dogs and cats.

Objective: To evaluate the fatigue life of stacked and single, veterinary cuttable plates (VCP) and small, limited contact, dynamic compression plates (LC-DCP).

Study Design: In vitro biomechanical study.

Methods: Fracture models (constructs; n = 8) were assembled for each of 6 groups all with 8-hole plates: 2.

Recombinant human osteogenic protein-1 induces bone formation in a chronically infected, internally stabilized segmental defect in the rat femur.

Background: Recombinant human osteogenic protein-1 (rhOP-1), combined with a collagen carrier, has been shown to induce new-bone formation in a variety of animal models. The purpose of the present investigation was to test the hypotheses that rhOP-1 would accelerate bone formation in an internally stabilized, chronically infected, critical-size defect in the rat femur and that this effect would be enhanced by the administration of systemic antibiotic.

Methods: A 6-mm segmental defect was created surgically, stabilized with a polyacetyl plate and six Kirschner wires, and contaminated with 10(4) colony-forming units of Staphylococcus aureus in one femur in each of 168 Sprague-Dawley rats.

Precooling an acetabular liner makes its insertion into a metal shell easier.

Temporary shrinkage of an acetabular polyethylene liner due to precooling could reduce the force required to snap the liner into its metal shell. This study documented cooling and heating rates of liners with a particular locking mechanism design, determined forces required to seat liners in their shells as a function of temperature, and quantified the force surgeons can exert with their thumbs when seating a liner. It took up to 8 minutes to cool 58- and 70-mm liners in an ice-water bath from room temperature to near 0 degrees C, and up to 24 minutes to subsequently warm these liners to near body temperature.

Characterization of a chronic infection in an internally-stabilized segmental defect in the rat femur.

The aim of this study was to characterize a new model of chronic osteomyelitis with clinically relevant features. A segmental defect of critical size was surgically created in the rat femur, stabilized with a polyacetyl plate and Kirschner wires, and contaminated with bacteria. The animals were allowed to recover while the contamination progressed to a chronic infection.

Morse-type tapers: factors that may influence taper strength during total hip arthroplasty.

We studied the effect of varying impaction force, repeated impactions, and fluid contamination on the disassembly strength of Morse-type tapers in 4 commercially available, modular femoral total hip components. The effect of varying techniques of taper assembly on the distraction force was studied. Our results show a reproducible and linear relationship between the taper impaction force and the disassembly force.

In vitro stability of cemented and cementless femoral stems with compaction.

Rigidity of initial fixation is a key factor contributing to the longevity of cemented and cementless femoral components in total hip arthroplasty. The objective of this study was to measure the initial stability of primary cemented and cementless femoral components under load when 15 pairs of cadaveric femurs were prepared by outward compaction of femoral cancellous bone in situ or by conventional extraction broaching. Three-dimensional micromotion was measured at proximal and distal locations on the femoral components using a device with spherical targets and linear variable differential transformers.