A biomechanical comparison of different wrist external fixators with and without K-wire augmentation.

To compare stability of wrist external fixation, simulated unstable extra-articular distal radius fractures were created in 7 fresh-frozen cadaveric upper extremities and stabilized using 4 different external fixators. Physiologic muscle tension across the wrist was simulated by application of 40-N load distributed among the wrist tendons. Alternating loads of up to 100 N in flexion and extension of the wrist were applied during stability testing and 3-dimensional kinematics of the proximal and distal fracture fragments were determined using attached infrared light-emitting diodes and a 3-dimensional motion tracking system. Fracture stability was reassessed for each of the constructs after augmentation of the fracture fragments with a single dorsal transfixion K-wire. K-wire augmentation demonstrated a significant reduction in motion of the distal radial fragment of at least 40% in all 3 rotational planes. For flexion/extension, the reduction in motion was from 4.5 degrees to 2.6 degrees. For radial/ulnar deviation, the range of motion decreased from 3.0 degrees to 1.5 degrees. Rotational motion declined from an average of 3.2 degrees to 1.2 degrees. The addition of the single dorsal transfixion K-wire significantly improved stability of each of the 4 fixators in at least 1 of the 3 planes in which motion was measured. While we compared the most rigid with some of the least rigid external fixators, the data do not support an important difference in fracture fragment stability among the 4 fixators. The data much more strongly support the concept of K-wire augmentation for increasing stability of an unstable extra-articular distal radius fracture regardless of the type of external fixator that is used.

Load-displacement behavior in a distal radial fracture model. The effect of simulated healing on motion.

External fixation of fractures of the distal end of the radius neutralizes external forces and maintains axial alignment during healing. As far as we know, there have been no biomechanical studies of the effects of early removal of the fixator in a partially healed fracture model. The purpose of the present study was to observe the load-displacement behavior of a distal radial fracture model in which we had simulated partial healing by injection of butyl-rubber caulk and augmented this simulated healing with Kirschner-wire fixation. Sixteen fresh-frozen hand-wrist-forearm specimens from cadavera were mounted in mid-rotation in resin pots, and a load was applied. An osteotomy was used to simulate the fracture. Relative motion at the site of the osteotomy was compared, with use of a three-dimensional Optotrak kinematic device, during physiological loading of six constructs with Kirschner-wire transfixion or outrigger fixation. In the experimental group, partial healing was simulated by injection of butyl-rubber caulk into the site of the osteotomy and testing with simulated muscle-loading was performed through a full range of motion of the wrist. No difference could be detected between the relative motion at the osteotomy sites that had been treated with standard fully augmented external fixation and that in the experimental group (p > 0.05). T test analysis revealed that motion was equivalent regardless of whether Kirschner-wire transfixion or outrigger fixation had been used (p = 0.62) and that all of the augmented constructs had significantly less relative motion than all of the nonaugmented constructs (p < 0.001).

A comparison of the cost effectiveness of one-stage versus two-stage bilateral total hip replacement.

Forty patients underwent 80 bilateral primary total hip replacements (THRs) under the same anesthesia (one-stage). Forty other patients who underwent unilateral primary THRs during the same time interval were selected to match the first 40 patients with regard to age, sex, diagnosis, weight, medical comorbidity, type of prosthesis used, and perioperative management protocol. An assumption was made in that each unilateral case represented the first side of bilateral THRs performed during two separate hospitalizations (two-stage). Analysis of the total hospital charges submitted to the insurance companies was made between the groups. On average, there was a 24% reduction (P<.05) for each case if bilateral THRs were done in one stage. This was primarily due to a significant decrease (P<.05) in the length of hospital stay in the one-stage group. There was no difference between the two groups in the operative time, estimated blood loss, or perioperative complications.