Escherichia coli infections in knee joints. The pharmacological and antibacterial effects of intramuscular antibiotics.

UNLABELLED: Using a standardized strain of Escherichia coli 06 and a rabbit knee-joint model, we determined the following values: (1) the effective concentrations of amikacin and carbenicillin in vitro against Escherichia coli 06 when used singly or in combination; (2) the levels of each of these antibiotics in serum and synovial fluid after an intramuscular injection; (3) the effectiveness of amikacin in preventing intra-articular infection when it is administered thirty minutes before and six hours after an intra-articular inoculation of the same strain of Escherichia coli; and (4) the synergistic effects of amikacin and carbenicillin in combination both in vitro and in vivo when used together as a single dose six hours after intra-articular bacterial inoculation. Amikacin was much more effective when administered before joint inoculation and the minimum effective (inhibitory) concentrations of amikacin in vitro and in vivo were approximately the same. A synergistic effect of amikacin and carbenicillin in combination was more clearly evident in vitro than in vivo. CLINICAL RELEVANCE: In vitro tests such as determinations of the minimum inhibitory concentration and the minimum bactericidal concentration, and the serum bactericidal test, can provide valuable guides for the determination of minimum goals for antibiotic therapy. These in vitro tests were related to concentrations of antibiotics in tissue assessed by in vivo bacterial challenge tests and were found to be predictive of efficacy in vivo.

Urinary infections in total hip arthroplasty. Influences of prophylactic cephalosporins and catheterization.

We studied 359 patients retrospectively and 100 patients prospectively, all on cephalosporin prophylaxis. Urinary infections were eight times more frequent in catheterized patients; most were caused by Pseudomonas and Enterobacter. One patients had acute seeding in the arthroplasty site from a Pseudomonas urinary infection.

Stability of the upper lumbar spine following progressive disruptions and the application of individual internal and external fixation devices.

UNLABELLED: Five fresh human cadavera were tested to determine range-of-motion measurements at the interspace of the first and second lumbar vertebrae after progressive disruption of the joint followed by internal and external stabilization. The disruption progressed from posterior to anterior, leaving the anterior longitudinal ligament and anterior part of the annulus fibrosus intact. Flexion-extension range of motion was most sensitive to progressive disruptions and was significant following disruption of the facets. The Taylor-Knight brace was effective for limiting lateral motion, fair for limiting flexion-extension, and not effective for rotation. The three-point hyperextension brace was fairly effective for flexion-extension only. The body cast was effective in limiting all motions. Wire loops partially cut through the spinous processes in all cases with extreme flexion. Harrington distraction rods were effective in limiting motion if under proper tension, but they dislodged in three of the five specimens. CLINICAL RELEVANCE: Data from this study show that flexion of the second lumbar vertebra on the first of 20 degrees or a lateral bend of 10 degrees seen on a routine roentgenogram without vertebral fracture indicates that all posterior ligaments and at least part of the annulus fibrosus must be disrupted. Because internal fixation failed on occasion, we strongly urge the use of external fixation and careful mobilization of the patient to prevent flexion and rotation if internal stabilization is used for disruptions of the upper lumbar spine. The body cast was the most effective in limiting motion of the external fixation devices tested.

Humeral hypertrophy in response to exercise.

We compared roentgenograms of the jumeri of a group of professional tennis players and showed that there was pronounced hypertrophy of bone on the playing side. The cortical thickness on that side was greater by 34.9 per cent in men and 28.4 per cent in women compared with the control side. This represents a highly significant hypertrophy of bone in response to exercise.

Biomechanics of spinal fixation and fusion.

Recent experiments have shown that in the sheep spine a displacement of 5.2 mm and a strain of 36% was present at the lumbosacral joint, where fusion almost never occurred when multiple, small (5 mm x 14 mm) cancellous and corticocancellous bone grafts were placed in an interlocking fashion across the decorticated lamina of the lumbar spine and sacrum. A displacement of 1.2 mm and a strain of 10% was found at the L5-L6 joint, where fusion always occurred when the same type of bone grafts were applied in the same manner (described above) over the decorticated lamina of L5 and L6. Firm fixation of the lumbosacral spine and bone graft has brought about an arthrodesis in this model, presumably because the displacement and strain had been limited to acceptable levels. Data are presented to support the concept that, because the spine is composed of bony elements separated by a disc with viscoelastic properties, the biomechanics of spinal fixation and fusion are different than the biomechanics of long bone fixation and fracture healing. These differences should be considered in the design and use of spinal fixation devices.

A paradigm of delayed union and nonunion in the lumbosacral joint. A study of motion and bone grafting of the lumbosacral spine in sheep.

In a group of nine sheep (Group A), it was noted that when small, interlocking cancellous and cortical cancellous bone grafts are placed posteriorly on the lumbosacral spine, union always occurred in the interlumbar motion segments and almost never occurred at the lumbosacral joint. One of the main differences in these two areas is the amount of motion that occurs at each level with flexion and extension. Because nonunion following bone grafting for arthrodesis of the spine is a serious clinical problem, we have studied the amount of motion seen at the interlumbar and lumbosacral joints in sheep to ascertain how much motion is compatible with union and how much is associated with nonunion. In vivo studies were carried out in eight sheep (Group B), and five normal spine segments were studied in vitro to determine normal motion in this species. To simplify the complex in vivo motion that occurs at the lumbar motion segments, the simple linear displacement and strain of the fusion mass (consisting of fibrous tissue and bone grafts placed on and between the laminas posteriorly) was measured with the spine in flexion and extension. When the displacement and strain at the interlaminar level of the L6-S1 joint was measured, the linear displacement was found to be 5.2 mm and the associated linear strain 36%. The displacement at the L5-L6 interspace was 1.2 mm, and the strain 10%. The stiffness of the L5-L6 joint (which always fused) and the L6-S1 joint (which did not fuse, with one exception) were also studied. In a third group of four animals (Group C), internal fixation of the lumbosacral joint was attempted in addition to bone grafting.(ABSTRACT TRUNCATED AT 250 WORDS)

Tennis shoulder.

A depression of the exercised shoulder was found in skilled tennis players, and in other athletes employing the overhand motion. The deformity is attributed to stretching of the shoulder elevating muscles and hypertrophy of the extremity. Most symptoms were over the anterior rotator cuff, and occurred on abduction of the arm. Shoulder depression results in a relative abduction and abduction causes impingement of the cuff. Shoulder droop may induce thoracic outlet syndrome and may simulate scoliosis in the athlete.

Modeling of the human leg in ski injuries.

This study establishes that the human lower extremity-ski system has a fundamental frequency of approximately 1 Hz. The fundamental mode dominates the system response when loading times are short compared to the first natural frequency. Consequently, the use of a single degree of freedom approximation and the use of impulse criteria can provide important insights into the problem of skiing injuries. Specifically, the sport of snow skiing develops forces with frequency content in the static, transition, and impulse regions of the leg-ski response spectrum. Therefore, ski release bindings must be designed to safely and effectively couple the leg to the ski throughout this loading environment. An important means of evaluating possible binding designs is by simulating their characteristics in a computer model. The model will apply realistic loading histories to the ski or binding, will evaluate the strain in the bones and ligaments of the lower extremity, and will determine the release point of the binding. The program presented in this discussion is one stage in the development of this total system capability.

Cellular uptake of ribonuclease A-functionalised core-shell silica microspheres.

Analysis of protein function in a cellular context ideally requires physiologically representative levels of that protein. Thus conventional nucleic acid-based transfection methods are far from ideal owing to the over expression that generally results. Likewise, fusions with protein transduction domains can be problematic whilst delivery via liposomes/nanoparticles typically results in endosomal localisation. Recently, polymer microspheres have been reported to be highly effective at delivering proteins into cells and thus provide a viable new alternative for protein delivery (protein transduction). Herein we describe the successful delivery of active ribonuclease A into HeLa cells via novel polymer core-silica shell microspheres. Specifically, poly(styrene-co-vinylbenzylisothiouronium chloride) core particles, generated by dispersion polymerisation, were coated with a poly(styrene-co-trimethoxysilylpropyl methacrylate) shell. The resultant core-shell morphology was characterised by transmission electron, scanning electron and confocal fluorescence microscopies, whilst size and surface charge was assessed by dynamic light scattering and zeta-potential measurements, respectively. Subsequently, ribonuclease A was coupled to the microspheres using simple carbodiimide chemistry. Gel electrophoresis confirmed and quantified the activity of the immobilised enzyme against purified HeLa RNA. Finally, the polymer-protein particles were evaluated as protein-transduction vectors in vitro to deliver active ribonuclease A to HeLa cells. Cellular uptake of the microspheres was successful and resulted in reduced levels of both intracellular RNA and cell viability.