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The effect of prolonged physical and psychological stress on the testicular function was studied in 8 students (age 22–25 years) of the Norwegian Academy of War during a combat course of 5 days' duration. The average urinary excretion of free cortisol and 17‐ketogenic steroids was 81 and 129% higher than the respective control values one week after the course. Plasma cortisol levels increased from 21.7 μg/100 ml at 8 a. m. before the course to 24.6 (P < 0.05), and serum HGH rose from undetectable levels, < 0.08 ng/ml, to an average value of 12.9 ng/ml ± 3.7 (SD) at 8 a. m. during the course. A marked suppressive effect on plasma testosterone levels from 5.6 ng/ml ± 1.4 to 0.9 ± 0.5, and no adjustment to stress was observed over a 5 day period. TeBG increased gradually from 26.9 nmol/l ± 9.9 to 52.7 ± 17.7 on day 6, followed by a slow decrease without reaching control values on day 12, suggesting that the decreased plasma testosterone levels probably reflect reduced production and not increased metabolism of testosterone. LH fluctuated during the course, but was significantly higher in the morning immediately following the end of the course than at the start (P < 0.02). It is postulated that the effect of stress on the plasma testosterone levels is mediated via an action both on the hypothalamus‐pituitary level and on the testis.

To determine factors predictive of early healing disturbances after fixation of femoral neck fracture, the radiographic and clinical data of 149 patients were subjected to a logistic regression analysis comparing them with the results 3 months postoperatively. As in previous studies, fracture reduction distinguished between fractures with or without healing disturbances. The following signs in the preoperative radiographs were predictive of unfavorable outcome: small head fragment, comminution of the calcar femorale, and varus angulation of the head. Fractures with negative predictive signs may be selected for primary arthroplasty.

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When revising loosened joint prosthesis, impacted morsellized bone is frequently used as organic scaffolding. We studied the relative influence that different bone particle size, impaction energy, and liquid content had on impacted bone stiffness. Bovine bone was morsellized in a bone mill by three grinding drums to produce bone with different chip size distribution. Next, portions of bone chips of controlled sizes were produced by a five-leveled sieve. Layer by layer of bone are constructed into pellets by our experimental impaction method. This method allows us to vary one independent factor at a time in a controlled manner while keeping the other factors constant. Stiffness for all bone pellets were measured during impaction and loading. In earlier studies, we focused on how impaction force, number of impaction strokes, and bone liquid contents influence mechanical behavior. Here, we compare the outcome of all studies using general linear models. All five factors significantly contribute to stiffness of impacted morsellized bone. Changing bone moisture has major, while increasing the number of impaction strokes beyond five per layer has minor effect. Low water content is the main contributor to highest load stiffness. Optimal stability of impacted morsellized bone is achieved with dried and well-graded particles. The number of heavy impaction strokes can be restricted.

Bone changes 6-12 weeks after castration have been studied in 25 female and 27 male middle-aged rats. Castrated female rats gained more weight than their controls, but had decreased bone density and calcium and hydroxyproline content per cm3 bone volume of tibia. Castrated male rats did not differ from controls regarding body weight and the bone parameters. No influence of castration on the mechanical strength of the femora could be detected in either sex. At 2 weeks after castration, the circulating levels of immunoreactive calcitonin (iCT) were decreased in female rats compared to controls. In contrast, iCT was increased both in castrated male and female rats 10 weeks later. We conclude that castration of 6-month-old female rats causes osteoporosis, and therefore represents a promising experimental model for studying postmenopausal bone loss.

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Bone ingrowth into weight-bearing porous fiber Ti-6Al-4V implants in rat tibias was assessed for the amount, composition, and mineralization rate 3, 12, and 26 weeks after implantation. The data were compared with the ipsi- and contralateral metaphyseal controls and related to the ultimate bending stresses of the distal bone/implant interfaces. From the 3rd to the 12th week there was rapid bone ingrowth and also marked decline in mineralization rate of the ingrowing bone. After 12 weeks the implants were macroscopically pervaded by bone. The ultimate bending stresses increased from the 3rd to the 12th week and reached 45% of that of controls after 26 weeks. There was a linear proportionality between the amount of bone ingrowth and interfacial strength but a curvilinear relationship between bone maturity in terms of calcium/hydroxyproline and calcium/phosphorous ratios and interfacial strength. Stepwise multiple regression analysis showed that the interfacial strength depends on the amount and the maturity of the ingrown bone. Compared with the calcium/hydroxyproline ratio, the calcium/phosphorous ratio was an unreliable predictor of interfacial strength.