Growth hormone-regulated intracellular signaling in UMR 106 osteosarcoma cells.

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are important growth factors for postnatal longitudinal bone growth. Although many effects of GH on bone growth are mediated by IGF-1, GH can directly influence bone cells. Limited knowledge exists regarding specific intracellular signaling pathways and genes activated by GH in bone cells. GH is known to activate several intracellular signaling pathways, among them the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway. GH mainly activates JAK2 and both isoforms of STAT5, A and B. STAT5 gene deletion experiments have shown the importance of these transcription factors for growth. To understand the molecular mechanism(s) behind this, different experimental models are needed. The UMR 106 cell line is a rat clonal osteosarcoma cell line with osteoblast-like phenotypic properties, one is the endogenous expression of GH receptor (GHR). The present study focused on whether these cells express a functional GH-responsive JAK2/STAT5 pathway. Analysis of cell extracts by immunoprecipitation and Western blot showed that physiological concentrations of GH activated JAK2. Western blot analysis of nuclear extracts from GH-stimulated UMR 106 cells showed that physiological concentrations of GH induced nuclear translocation of both STAT5 isoforms, but with STAT5A being predominant. Both isoforms displayed similar nuclear turnover after GH stimulation of cells. Gel electrophoretic mobility shift assay (GEMSA) of nuclear extract revealed that both STAT5A and STAT5B obtained DNA-binding capacity after GH stimulation. Thus, we have shown, for the first time, the expression and GH-induced activation of JAK2 and STAT5A/B in UMR 106 osteoblast-like cells. This study also shows that this cell line is a suitable experimental model to study unique GH effects in osteoblasts mediated by STAT5.

Does bone measurement on the radius indicate skeletal status? Concise communication.

Single-photon (I-125) absorptiometry was used to measure bone mineral content (BMC) of the distal third of the radius, and dual-photon absorptiometry (Gd-153) was used to measure total-body bone mineral (TBBM), as well as the BMC of major skeletal regions. Measurements were done in normal females, normal males, osteoporotic females, osteoporotic males, and renal patients. The BMC of the radius predicted TBBM well in normal subjects, but was less satisfactory in the patient groups. The spinal BMC was predicted with even lower accuracy from radius measurement. The error in predicting areal density (bone mass per unit projected skeletal area) of the lumbar and thoracic spine from the radius BMC divided by its width was smaller, but the regressions differed significantly among normals, osteoporotics, and renal patients. There was a preferential spinal osteopenia in the osteoporotic group and in about half of the renal patients. Bone measurements on the radius can indicate overall skeletal status in normal subjects and to a lesser degree in patients, but these radius measurements are inaccurate, even on the average, as an indicator of spinal state.

Prolactin binding sites in rat brain and liver: effects of long-term ovariectomy and ovarian steroids.

The effects of long-term ovariectomy on the levels of brain and liver lactogenic binding sites as well as plasma and liver prolactin (PRL) have been investigated in sham-operated and ovariectomized rats receiving either 17 beta estradiol (OVX-E), progesterone (OVX-P), or vehicle (OVX-V). The levels of lactogenic binding sites in the parietal and piriform cortices, amygdala, thalamus, hypothalamus, as well as in the liver were significantly decreased after long-term ovariectomy. Moreover, the levels of plasma and liver PRL were also significantly decreased. Exogenous estradiol and progesterone replacement restored the levels of lactogenic binding sites in the parietal cortex and hypothalamus as well as in the liver. However, plasma and liver PRL levels were significantly increased by estradiol but only restored by progesterone. These results suggest that ovarian steroids influence the levels of lactogenic binding sites and prolactin.

Prevention of ectopic bone formation by local application of ethane-1-hydroxy-1,1-diphosphonate (EHDP): an experimental study in rabbits.

This report shows that ectopic bone formation, a serious problem in orthopedic surgery, can be controlled in an animal model by local application of EHDP (disodium-ethane-1-hydroxy-1,1-diphosphonate). The results might be particularly pertinent to the clinical problem of preventing the recurrence of ectopic bone after surgical excision. Male New Zealand white rabbits were treated with immobilization and intermittent passive manipulation of the right knee. The treatment caused bone formation in the quadriceps muscle, which was visible on radiographs after 3 weeks. In this model, the effect of methacrylate implants containing EHDP was studied. A concentration of 16 g EHDP/100 g methacrylate inhibited bone formation in experimental cortical defects. Release of radiolabeled EHDP was studied in an in vitro system. The release of the drug was approximately 20 mg/day and implant initially, decreasing to about 0.1 mg/day/implant after 30 days. Standardized implants containing 16 g EHDP/100 g were then surgically attached to the femur, and the ectopic bone formation created by immobilization and intermittent manipulation was compared with that in rabbits treated with implants but without EHDP. The ectopic bone was measured from lateral and frontal radiograms and from radiograms of serial transverse sections of the thigh. We found that the EHDP implants were capable of preventing major ectopic bone formation in all cases, whereas all rabbits with an implant containing no EHDP had substantial ectopic bone formation at the end of the experiment. There was no difference between groups in the relative amount of cartilage, connective tissue, and normal bone. We conclude that local administration of EHDP may be a useful method for prevention of ectopic bone formation under the conditions and time employed.

Trauma type, age, and gender as determinants of hip fracture.

We determined the trauma type of femoral neck and trochanteric fractures in men and women aged greater than or equal to 20 years in 19, 128 fractures reported to a computerized medical information register during 1972-1981. We found that the earlier known exponential increase of fracture incidence by age started in early adulthood rather than during middle age. An age-related increase was found for each type of injury as well, although the incidence of fractures resulting from severe trauma increased less than that of fractures associated with moderate trauma. The incidence of low-energy fractures in men as well as in women displayed a constant increase rate with age from young adulthood on, impugning the widely held belief that the menopause is a significant risk factor for fractures. The dominating risk factor for proximal femoral fracture in adults appears to be age, irrespective of the cause of injury, with a chronological decline in bone strength as the most likely cause of the exponential increase in the fracture incidence during adult life.

Prediction of the outcome after hip fracture in elderly patients.

We report a prospective study of 232 consecutive patients with hip fractures. All were over 64 years of age and living independently before admission to a geriatric orthopaedic ward. We assessed the value, at admission, of predicting factors for independent living at one year after injury. The most important factors were: (1) preinjury function in activities of daily living (grade A or B on the Katz et al (1963) scale); (2) absence of other medical conditions which would impair rehabilitation; and (3) cognitive function better than 7 on the Pfeiffer (1975) mental questionnaire. The odds ratios (95% CI) for these three predictors were 3.5 (1.3 to 9.1), 2.9 (1.3 to 6.1) and 2.4 (1.9 to 4.9), respectively. When all predictors were positive at admission, 92% were living independently at one year; with one, two or three negative predictors, the percentages living independently were 76, 61 and 27, respectively. The median values of the total number of days in hospital, irrespective of diagnosis, during the first year were 12, 24, 29 and 149 days for the four groups. The mortality at one year was predictable on admission only by the number of medical conditions: with no other diagnosis than the fracture the mortality was 0%; with one or two additional conditions the mortality was 14%; and with three or more additional diagnoses it was 24%. These simple and robust predictors can be used to optimise resources for rehabilitation.

Assessment of foot disorders using biomechanical analysis of foot loads during locomotion.

The aim of this study was to investigate techniques for assessment of surgical procedures for foot disorders. An optoelectronic system was used to obtain position data during walking for the knee joint, ankle joint and the second metatarsal joint. The ground reaction forces were simultaneously measured and the moment of force at the mentioned joints were analysed. Pressure transducers in the shoe were used to measure the local pressure at the great toe, first and fifth metatarsal heads, and heel pad. Among studied procedures were Keller's operation for hallux rigidus and distal oblique osteotomy for hallux valgus. The study indicated that both methods can be used to assess mediolateral shifts of the centre of pressure on the foot due to the operation. A difference between operation results were that the moment arm of the ground reaction force with respect to the knee joint increased after distal oblique osteotomy, while it decreased after the Keller type operation. From a clinical point of view this can have the effect that the loads at the knee joint and especially at the medial condyle increases after the distal oblique osteotomy. The study showed that the described techniques have a potential for assessment of surgery for first metatarsophalangeal joint. Of special relevance is the possibility of studying the effect of foot pathologies on the loads at the knee joint.

Mitochondrial DNA depletion in single fibers in a patient with novel TK2 mutations.

The mitochondrial DNA (mtDNA) depletion syndrome is a genetically heterogeneous group of diseases caused by nuclear gene mutations and secondary reduction in mtDNA copy number. We describe a patient with progressive muscle weakness and increased creatine kinase and lactate levels. Muscle weakness was first noted at age 1.5 years and he died of respiratory failure and bronchopneumonia at age 3.5 years. The muscle biopsy showed dystrophic features with ragged red fibers and numerous cytochrome c oxidase (COX)-negative fibers. qPCR analysis demonstrated depletion of mtDNA and sequence analysis of the mitochondrial thymidine kinase 2 (TK2) gene revealed two novel heterozygous variants, c.332C > T, p.(T111I) and c.156 + 5G > C. Quantitative analysis of mtDNA in single muscle fibers demonstrated that COX-deficient fibers showed more pronounced depletion of mtDNA when compared with fibers with residual COX activity (P < 0.01, n = 25). There was no evidence of manifestations from other organs than skeletal muscle although there was an apparent reduction of mtDNA copy number also in liver. The patient showed a pronounced, albeit transient, improvement in muscle strength after onset of treatment with coenzyme Q10, asparaginase, and increased energy intake, suggesting that nutritional modulation may be a therapeutic option in myopathic mtDNA depletion syndrome.

Minimization of residual tin in the controlled Sn(II)octoate-catalyzed polymerization of epsilon-caprolactone.

By using less catalyst in the ring-opening polymerization of epsilon-caprolactone, a residual tin content of 5 ppm was reached without the need for additional purification. The initial amount of tin (II) 2-ethylhexanoate [Sn(Oct)(2)] was varied using catalyst:monomer ratios of 1:1000, 1:10,000, and 1:20,000. The impact on the final conversion, reaction control, average molecular weight, and polydispersity was studied. The amount of Sn(Oct)(2) could be significantly reduced without influencing the reaction results. The residual amount of tin was reduced from 176 ppm with a catalyst:monomer ratio of 1:1000 in the polymer, to 5 ppm with the ratio 1:10,000. It was thus concluded that a catalyst:monomer ratio of 1:10,000 or lower is required to achieve a polymer with tin content suitable for biomedical applications. The materials were also tested in a proliferation study with mesenchymal stem cells from mouse. Porous scaffolds were fabricated from the polymers, using a salt leaching technique, and the cell growth on the porous scaffolds as well as on homogeneous films was determined by light absorbance measurements. In this study, the cell proliferation results showed that cells could grow on all polymers with an efficiency equal to or better than that on normal tissue culture plastic.

Reliability of radiological and cosmetic measurements in hallux valgus.

PURPOSE: To evaluate the reliability of angular, linear, and sesamoid position measurements on preoperative and postoperative radiographs in hallux valgus (HV), as well as cosmetic foot appearance. MATERIAL AND METHODS: Radiographs and photographs from 100 patients undergoing HV surgery were evaluated by two independent observers. RESULTS: Interobserver and intraobserver agreements for HV angle using coefficient of repeatability measures were 4.4 degrees and 3.7 degrees, respectively. Intraclass correlation coefficient measures within and between agreements were 0.97 for HV angle. For intermetatarsal distance, interobserver and intraobserver values were 0.90 and 0.94 when measuring from the midline of each metatarsal and 0.75 and 0.92 when measuring between cortices. Using the visual analog scale to evaluate esthetic appearance, interobserver and intraobserver agreements were 0.59 and 0.79, respectively. Sesamoid position values were also measured. Interobserver and intraobserver kappa values for preoperative and postoperative evaluations with two established methods (Mann or Smith) were 0.47 and 0.70 or 0.65 and 0.75, respectively. CONCLUSION: Intraobserver reliability was higher than interobserver for intermetatarsal distance, cosmetics, and sesamoid position. Angular measurements were more accurate than linear. Esthetic evaluation was less reliable than radiographic, except in the case of sesamoid position measurements.

The effect of thyroparathyroidectomy: development of disuse osteoporosis in adult rats.

The present investigation was undertaken in order to study the role played by the thyroid and the parathyroid glands in the development of osteoporosis induced by immobilization. One hundred and fifty-three male adult Sprague-Dawley rats were divided into 2 groups. The animals of one group were thyroparathyroidectomized; those of the other group were left intact. Each group was then divided into two subgroups in one of which the right hind leg of the animals were immobilized by elastic adhesive bandages. The animals were observed for varying periods of time up to 16 weeks. Bone mass and composition was determined and the results indicated that disuse osteoporosis occurs in rats in the virtual absence of the thyroid and parathyroid glands. The bone loss of the immobilized femur and tibia is however less pronounced in thyroparathyroidectomized than in intact rats.

Functional significance of heterotopic bone formation after total hip arthroplasty.

The effects of heterotopic bone formation on hip function after arthroplasty was studied in 145 cases of total hip arthroplasty. Hip muscle strength was determined 1.8-2.9 years after the operation, using a Cybex II dynamometer. Heterotopic bone formation was seen after 75% of the operations, and in 21% significant amounts developed (Brooker's classes III and IV). The gain in range of motion after surgery was significantly less in the groups with class III or IV heterotopic bone than in those without heterotopic bone formation. Heterotopic bone did not cause pain or Trendelenburg's limp after surgery; in fact, patients with trochanteric pain had less heterotopic bone than those without this pain. Hip flexion strength was greater in men with heterotopic bone than in those without heterotopic bone. Also, men with heterotopic bone formation had a higher mean maximum strength in extension but lower mean strength in abduction than did men without heterotopic bone (NS). When only patients with unilateral hip disease were considered, the same differences were found around the healthy hip; men with heterotopic bone formation had greater strength in flexion and extension than men without heterotopic bone formation and the same tendencies were seen in women. Accordingly, heterotopic bone had no serious impact on hip muscle strength in this study.

A new transtrochanteric approach to the hip.

This transtrochanteric approach to the hip maintains continuity between the greater trochanter and the vastus lateralis muscle, thereby preventing the gross displacement of the greater trochanter and preserving the branches of the lateral circumflex vessels to it. The procedure offers the advantages of easy exposure and a high rate of bony union between trochanter and femur. We have used the procedure in 189 consecutive operations; in only four cases did union between the bones not occur. The trochanter was never cranially displaced more than three cm, and even in the cases of non-union abductor power was good. Although we do not recommend trochanteric osteotomy for every case of total hip replacement, we suggest that the approach be used for cases where technical problems are anticipated.

The influence of mediolateral deformity, tibial torsion, and foot position on femorotibial load. Prediction of a musculoskeletal computer model.

The influence of mediolateral deformity, tibial torsion, and different centers of foot support was studied with a three-dimensional computer model that incorporates the significant muscles of the lower extremities needed for quasi-static walking. This theoretical method avoids the variability in gait pattern from the pain and discomfort associated with deformity in patients. The study illustrates the possible importance of the muscle force on the load across the knee and ankle. High strains in the medial gastrocnemius and the medial hamstring created particularly high loads in the medial compartment of the knee. Internal torsion and varus deformity were associated with the highest loads in the medial compartment of the knee, although the peak load for each deformity occurred in different phases of the gait cycle. Both external torsion and valgus deformity generally decreased the load in the medial compartment, but early in the gait cycle external torsion increased the loads on the medial side. In addition, when the center of support of the body was in the forefoot, the loads through the knee were lower than when foot support was at the heel. As expected, if the center of support was on the lateral foot line, the lateral compartment was subjected to more load and, conversely, when the center of support was on the medial part of the foot the medial compartment of the knee was more loaded. Although the predicted forces agree well with those found with other methods, we think that the model is best used to measure the direction of influence of specific factors.

Metatarsal osteotomy using internal fixation with compression screws.

Forty-six metatarsal osteotomies in 25 feet were performed in order to treat forefoot deformity. The authors used an exacting operative procedure based on oblique osteotomies of the metatarsal and rigid internal fixation. All osteotomies healed and only one patient was not satisfied with the operation. This technique provided predictable long-term results in the authors' hands, and also involved an easier postoperative course than conventional methods.

The fine structure of the parathyroid glands of rats with disuse osteoporosis.

The parathyroid glands were studied ultrastructurally in two groups of rats: one control group and one group with an immobilized hindleg. The aim was to see whether immobilization has any effect on the fine structural appearance of the parathyroid glands. No morphological differences were recorded between the two groups. Nor were any signs of increased functional activity observed. The results denote that no increased parathyroid activity occurs after immobilization of an extremity in rats.

Late hematogenous infection in total joint replacement: studies of gentamicin and bone cement in the rabbit.

Hematogenous infection of total joint replacements was experimentally produced in rabbits with cemented endoprostheses in both knees. One one side the bone cement contained gentamicin. Bacteremia was induced six to eight weeks postoperatively using a strain of Staphylococcus aureus. Twenty-five days after the induction of bacteremia approximately a third of the artificial joints were infected, whereas no bacteria were found in blood and viscera. Although the gentamicin cement still possessed anti-bacterial activity in vitro, it did not prevent hematogenous infection. Thus, gentamicin cement would not protect the joint against delayed hematogenous infection.