Correlation of radiographic measurements with biomechanical test results.

The refracture of bone after the removal of an internal fixation device is not common, but it can be a serious complication. The development of a simple radiographic tool to determine the condition of a healing bone would be of clinical importance. As a basis to developing this tool, it was important to determine whether a correlation exists between radiographic results and the stiffness index of bones during fracture healing. This experimental investigation in beagles showed that at 24 weeks after a unilateral femoral osteotomy, plain radiographs could be used to determine the stiffness index of healing bone. The results showed the cortex to callus ratio (the thickness of the cortex, including the periosteal callus, normalized by the thickness of the cortex of the bone not surgically treated) correlated positively with the stiffness index of the bones. This measurement might be useful in the clinical assessment of fracture healing. From a clinical point of view, caution is recommended after the removal of fracture plates when the cortex to callus ratio is low because such a low ratio may be associated with a low stiffness index of the healing bone. This information allows clinicians to adapt the postoperative regimen accordingly.

Masked rotatory subluxation of the atlas associated with fracture of the clavicle: a clinical and biomechanical analysis.

We report on two children who developed a fixed rotatory subluxation of the atlantoaxial joint due to torticollis being attributed to a fractured clavicle. Appropriate treatment was delayed for weeks to months; only after the fractured clavicle had healed and the torticollis persisted was the problem identified. Persisting rotatory subluxation also predisposes to further anterior displacement of C-1 due to an increased moment arm created by the forward displacement of the center of gravity of the head. The association of atlantoaxial subluxation should always be considered in children presenting with a clavicular fracture and an acute torticollis.

Efficacy and safety of hydrocortisone buteprate 0.1% cream in patients with atopic dermatitis.

This multicenter, double-masked, placebo-controlled, randomized study evaluated the efficacy, safety, tolerability, and cosmetic acceptability of hydrocortisone buteprate 0.1% cream in the treatment of patients with atopic dermatitis. One hundred ninety-four adults with clinically diagnosed atopic dermatitis were randomized to treatment with hydrocortisone buteprate 0.1% cream or placebo (the cream base of the medication) applied topically once daily for 14 days. Investigators assessed the severity of dermatitis signs on a four-point scale at baseline and on days 3, 7, and 14. Overall improvement was also assessed at each study visit using a seven-point scale. In addition, overall treatment efficacy, tolerability, and cosmetic acceptability of both treatments were evaluated at the last study visit. At each study visit, patients treated with hydrocortisone buteprate showed significant improvement in mean total lesion scores and overall improvement compared with those receiving placebo. Investigators and patients rated hydrocortisone buteprate significantly more effective and significantly more tolerable than placebo at the end of the treatment period. In general, most adverse effects were mild to moderate, with a burning sensation (4% of patients using placebo, 2% of patients using hydrocortisone buteprate) being the most commonly reported. Patients judged both hydrocortisone buteprate and placebo cosmetically acceptable for daily use.

Improved fracture healing with less rigid plates. A biomechanical study in dogs.

The effect of axial plate flexibility on bone healing was investigated with four experimental plating systems using elastic inserts to manage their axial flexibility in compression. The plates were tested in 72 dogs that underwent unilateral femoral osteotomy and noncompression plating on alternate sides. The femurs of 18 dogs were plated with each of the four plating systems: six for 8 weeks, six for 16 weeks, and six 6 for 24 weeks. Each osteotomized femur and its contralateral control were removed at the end of the plating periods and tested in multidirectional nondestructive bending to evaluate the polar distributions of their flexural rigidity. Results from each pair of bones were used to calculate parameters defining the relative mechanical status of the healing bone. These parameters were used to evaluate the effects of plating system axial flexibility and time on healing. It was found that: within the selected range of axial flexibility there was an optimal value that produced the best healing; healing progressed with a diminishing rate leading to a steady state; and all four plating systems produced healing superior to that obtained with dynamic compression plates.

Mechanical evaluation of four- versus eight-pin halo fixation.

Fixation of the halo device in the skulls of young children is sometimes compromised because of a thinner cortex and the increased jarring and trauma that small children experience during their everyday activities of life at that age. To assess the increased fixation that an eight-pin halo fixation would provide over the more standard four-pin fixation, the stiffness of fixation of a halo orthosis was evaluated in four dried human cadaver skulls. Two different fixation systems were used: the first one with four pins in the standard locations and the second with four additional pins. A compressive force was applied to the halo ring at a constant rate of 1.27 mm/min. Load and deflection data were recorded simultaneously until a force of 400 N was reached. Results for the two-pin systems were analyzed and compared statistically by using paired t tests. Statistically significant differences were established between the two sets of results with the 8-pin system providing an increase of 24.2% in the stiffness of fixation.

Degeneration at the insertion weakens the tensile strength of the supraspinatus tendon: a comparative mechanical and histologic study of the bone-tendon complex.

The purpose of this investigation was to determine the relationship between the degree of degeneration at the supraspinatus insertion, the tensile strength, and the site of failure of this tendon. Thirty-three fresh cadaveric shoulders (average age: 62 years; range: 39-83 years) were examined. A tensile load to failure was applied at a constant crosshead speed of 25.4 mm/min to a 10 mm wide strip of the supraspinatus tendon that remained attached to the bone. Preexisting degenerative changes at the insertion were assessed and scored histologically and compared with the ultimate tensile stress. Twenty tendons failed at the insertion (the insertion group), and 11 failed in the midsubstance (the midsubstance group). The histologic score of degeneration for the insertion group was significantly higher than that for the midsubstance group (p = 0.0026). There was a negative correlation between the ultimate tensile stress at the insertion and the degeneration score for the insertion group (r = -0.60; p = 0.013). Histologic observations revealed that disruptions of tendon fibers were located mostly in the articular half of the tendon and that they enlarged during mechanical testing in 90% of the specimens of the insertion group. It seems that degenerative changes at the supraspinatus insertion reduce the tensile strength of the tendon and constitute a primary pathogenetic factor of rotator cuff tear.

Flexural rigidity in partially demineralized diaphyseal bone grafts.

Control of biomechanical properties of demineralized diaphyseal bone allografts is required for their clinical application. Therefore, the changes in flexural rigidity in human fibulae were investigated as a function of the demineralization depth using a nondestructive bending test. Starting at the facies medialis, the flexural rigidity was determined in 24 planes at 15 degrees sequential angular increments, which allowed data collection around the circumference of the bone. Test bones included 4 pairs of left and right human fibulae and 15 single fibulae. The elliptical distribution of the flexural rigidity of left and right fibulae and single fibulae before and after demineralization was compared. The stiffness index and the area ratio were defined as parameters to describe the mechanical status of the test bones. Results show that the rigidity of diaphyseal bones is strongly dependent on the reduction of their cortical thickness by demineralization. A mathematical model allowing prediction of the reduction of the rigidity of diaphyseal bone grafts as a function of the demineralization depth is presented.

Two processes of bone remodeling in plated intact femora: an experimental study in dogs.

Bone loss is known to occur under plates used for internal fixation. Its exact location and extent and its relationship to the plate-bone contact area was investigated in 36 adult beagles. Plates with two different contact areas were fixed unilaterally to intact femora for periods of 8 and 24 weeks. After removal, the bones were assessed radiographically, histologically, histomorphometrically, and biomechanically. Two processes that affect the bone after plating became apparent. One is a short-term process, possibly caused by the interference of the plate with the blood supply to the cortex. This is followed by necrosis, which induces porosis. The second independent process is caused by the tendency of the bone to adapt to the new state of mechanical loads that results from the load sharing by the plate. The first stage of this process is expressed through swift changes in the bone cross-sectional area under the plate by remodeling in all three envelopes: haversian, periosteal, and endosteal. This stage is followed by a gradual remodeling towards a steady state, in which the final cross-section of the bone is attained. Both processes affected the bone simultaneously during plate fixation. The process caused by the vascular interference ceases after some time, and only the process due to stress-shielding prevails for a long period.

Suprofen. An overview of long-term safety.

Suprofen, a new oral peripherally acting analgesic agent, has been shown to be effective in the relief of acute and chronic pain. This paper reviews data relative to long-term safety from more than 800 patients who received suprofen. Some of these patients were followed up to 2 years. Suprofen was generally found to be at least as safe and as well tolerated as reference drugs of aspirin, propoxyphene and propoxyphene combination. The discontinuance rate because of side effects was 17.7% for patients receiving suprofen and 23.9% for patients receiving reference drugs. Gastrointestinal side effects were the most frequently reported reasons for all patient dropout in all treatment groups. Fewer patients receiving suprofen discontinued due to gastrointestinal side effects (10.9%) than with reference drugs (17.2%).

Does the choice of suture material affect the incidence of wound infection? A comparison of dexon (polyglycolic acid) sutures with other commonly used sutures in an accident and emergency department.

One hundred and four patients with superficial lacerations were sutured with either Dexon (polyglycolic acid), silk, polyethylene or nylon sutures. The incidence of postoperative tissue reaction and wound infection was compared. There were few complications and these occurred with almost the same frequency in each suture group, although there were slightly more cases of infection in the patients who were sutured with silk. Dexon was seen to possess certain advantages in that it caused as little tissue reaction as the other sutures but did not have to be removed subsequently. This could clearly be of benefit to the patients and hospital staff alike.