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Harald Steen

Publications and source records attributed to Harald Steen.

14 recordsLinked to original sources
PubMed2006

Optimum loading mode for axial stiffness testing in limb lengthening.

The axial stiffness of the regenerate is an indicator of bone healing after fracture or distraction osteogenesis. The axial stiffness may be assessed clinically by measuring the sharing of load between fixator and limb during loading. The aim of this study was to find out how to perform the stiffness test in order to minimize the influence of confounding factors to the test result. We investigated whether the test score was influenced by two factors: 1) the magnitude of the external load applied to the limb during the test; and 2) the patient's position during the test. The problem was approached by both a clinical study and by theoretical calculations. Thirty-three patients undergoing leg lengthening were tested regularly during the consolidation period. The stiffness test was executed with both high and low load, and in a standing and sitting position. There were significant differences in results between both the tests with high and low load, and between the standing and sitting tests. This indicated that both the magnitude of force and patient position during the test influenced the test result. Accordingly, these factors represent sources of error and must be taken into consideration when performing an axial stiffness test. The result of the theoretical calculations confirmed the result. We recommend performing the test while the patient is sitting, and to apply no more than 20% of the individual's body weight. It is also recommended that the same load be used in every test, when testing a patient several times during the treatment period.

Adolescent↗
PubMed2006

No difference in tibial lengthening index by use of Taylor spatial frame or Ilizarov external fixator.

BACKGROUND: Different methods and devices are used to perform lengthening and deformity reconstruction in the tibia. Recently, the Taylor spatial frame (TSF) has been introduced as a computer-assisted and versatile external ring fixator. Lengthening index (LI) and complications are important result parameters, and the aim of this study was to review our first 20 tibial segments operated with the TSF and to compare the results with our experience of using the traditional Ilizarov external fixator (IEF). PATIENTS AND METHODS: We lengthened 20 tibial segments in 20 patients with the TSF. The results were compared with those of 27 tibial segments from 27 patients that were lengthened with the IEF. All segments were operated on with monofocal osteotomies. RESULTS: In the overlapping zone of comparable lengthening distances between 2.4 and 6.0 cm, the LI of 2.4 and 1.8 months/cm was not significantly different between the TSF and IEF groups, respectively (p = 0.17). This non-significant difference was confirmed after adjustment for age. INTERPRETATION: We found no difference between the TSF and IEF frames regarding LI and complication rate. However, rotational, translational, and residual deformity correction is easier to perform with the TSF.

Adolescent↗
PubMed2006

Small rodent winter survival: snow conditions limit access to food resources.

1. In Fennoscandia during winter small rodents spend most of their time in the subnivean space, between the snow cover and the ground. The subnivean space is probably not a uniform habitat, but broken into accessible and inaccessible patches by ice covering the vegetation. This might reduce access to otherwise available food resources. 2. To test whether ice formations reduce access to food and thus limit winter survival of small rodents, we conducted an experiment where we increased subnivean space by adding corrugated aluminium sheets on the ground before onset of winter. The sheets prevented ice formation, thus mimicking natural occurring subnivean space, and providing more room for animals living in the subnivean space to forage. 3. During the experiment 142 Microtus oeconomus were passive induced transponder (PIT)-tagged, and a system consisting of fixed tube-shaped antennas and PIT-tag readers were used to provide data to analyse winter survival and individual subnivean space use. The extent of winter grazing was measured after snow melt by examining percentage area grazed. 4. The treatment resulted in increased survival which corresponded well with significantly higher space use and more grazing under the sheets. 5. Females showed a positive correlation between probability of survival and body mass while no such effect was observed in males. 6. The results suggest that the snow cover reduces survival in winter by physically enclosing the vegetation in ice and thus reducing access to otherwise available food resources. The amount of ice and its configuration might vary between years due to changing weather patterns. Our results offer a mechanistic explanation for variations in winter survival and suggest incorporating climate variables in future small rodent models. 7. Directional and long-term changes in climate might result in increased ice formation in the subnivean system. Such deterioration may lead to reduced winter survival and act by stabilizing population dynamics and dampening vole cyclicity.

Animals↗
PubMed2005

Sheep grazing and rodent populations: evidence of negative interactions from a landscape scale experiment.

Inter-specific competition, facilitation and predation influence herbivore assemblages, but no study has experimentally explored the interactions between large ungulates and small rodents. In a fully replicated, landscape scale experiment, we manipulated densities of domestic sheep in mountain pastures in Norway. We then determined population growth and densities of rodents by live trapping in each of the areas with different sheep densities. We found that the (summer) population growth rate and autumn density of the field vole (Microtus agrestis) was lower at high sheep density. This provides the first experimental evidence of negative interactions between an ungulate and small rodent species. There was no effect on the bank vole (Clethrionomys glareolus), whose diet differs from sheep. Sheep density, therefore, potentially alters the pattern of inter-specific population synchrony amongst voles. Our study shows that negative interactions between large ungulates and small rodents may be species-specific and negative population consequences for the rodent population appear above threshold ungulate densities.

Animals↗
PubMed2005

In vivo assessment of regenerate axial stiffness in distraction osteogenesis.

This paper presents an in vivo test for assessment of regenerate axial stiffness after the distraction phase of lengthening therapy. The test result supplements radiography in evaluating bone healing and assists in determining when the regenerate stiffness is sufficient for removal of the external fixator. The test is non-invasive and does not require fixator removal. The theoretical basis for the method is that an externally applied load is shared between the fixator and the regenerating bone. The amount of load carried by the regenerate depends on its axial stiffness, which increases with advanced mineralization. By measuring the force in the fixator while applying a known external load to the limb, the load-share ratio between fixator and limb can be assessed. A load-share ratio of 100% indicates that the entire load is carried by the fixator. The ratio decreases as the regenerate structure gradually stiffens. In a clinical trial of 22 individuals with tibial lengthening, the fixator was removed when the load-share ratio dropped below 10%. None of the patients experienced fracture after removal of the fixator.

Biomechanical Phenomena↗
PubMed2004

Effect of neuromuscular training on proprioception, balance, muscle strength, and lower limb function in female team handball players.

OBJECTIVE: Introduction of a neuromuscular training program will increase muscle strength, balance, and proprioception in elite female handball players. DESIGN: Prospective intervention study. PARTICIPANTS: Thirty-five female team handball players from 2 teams in the elite division participated. Their mean age was 23 (+/-2.5) years, and their mean weight was 69.2 (+/-7.3) kg. They had played handball for 14.9 (+/-3.2) years, 4.7 (+/-2.8) years at the top level. The total number of training hours per week was 10 to 11. INTERVENTION: Based on earlier studies and knowledge about common risk situations in team handball, an anterior cruciate ligament (ACL) injury prevention program with 3 different sets of exercises was developed, each set with a 5-step progression from simple to more challenging exercises. The teams were instructed to use the program a minimum of 3 times a week during a training period of 5 to 7 weeks, and then once a week during the season. The duration of each training session was approximately 15 minutes. MAIN OUTCOME MEASURES: Balance (KAT 2000), proprioception (threshold to detection of passive motion), muscle strength (Cybex 6000), and 3 functional knee tests. The players were tested pretraining (test 1) and 8 weeks (test 2) and 12 months (test 3) after the training started. RESULTS: There was a significant improvement in dynamic balance between test 1 and test 2, with a balance index (BI) of 924 (+/-225) and 778 (+/-174), respectively (P = 0.01). The effect on dynamic balance was maintained 1 year after training (BI, 730 +/- 156). For static balance, no statistically significant changes were found. For the other variables measured, there were no statistical differences during the study period. CONCLUSION: The ACL injury prevention training program improved dynamic balance in an elite team handball players.

Adult↗
PubMed2003

Open versus arthroscopic subacromial decompression: a prospective, randomized study of 34 patients followed for 8 years.

In a randomized prospective study, we selected 15 patients for arthroscopic subacromial decompression (ASD) and 19 patients for open subacromial decompression (OSD). All had impingement syndrome (Neer grade II), and had been unsuccessfully treated without surgery for more than 6 months. The UCLA Shoulder Rating Scale, Visual Analogue Scales for pain and satisfaction, isokinetic dynamometer recordings and physical testing were assessed preoperatively and at 1 (except isokinetic testing), 3, 6, and 12 months, and, finally, 8 years after surgery. We found essentially no differences in the clinical tests between the groups during this period. The use of ASD or OSD seems to be a matter of cosmesis and personal preference.

Acromion↗
PubMed2003

Residual challenges after healing of congenital pseudarthrosis in the tibia.

The purpose of the current study was to evaluate the clinical results of the Ilizarov bone transport method in the treatment of congenital pseudarthrosis in the tibia. In seven patients operated on between 2.6 and 7.8 years of age, primary healing of the pseudarthrosis was achieved in all patients (after additional bone grafting in two patients). Within a followup of 6 to 8 years, major complications occurred in all patients. Five refractures occurred, and in one patient the refracture did not heal. At the last followup, axial deformities and an abnormal malalignment test with lateral mechanical axis deviation of 10 mm or greater was found in all patients. Three patients had leg length inequality of 20 mm or more. The Ilizarov bone transport method is useful in achieving primary healing in congenital pseudarthrosis of the tibia, but residual challenges with secondary reconstructive surgery caused by refracture and postoperative deformities must be expected.

Bone Transplantation↗
PubMed2002

[Complaints regarding lumbar disk herniation treatment reported to the Norwegian Compensation System].

BACKGROUND, MATERIAL AND METHODS: Over the 1993-99 period the Norwegian Patient Compensation System made decisions in 4,041 orthopaedic treatment injury cases. 700 cases were randomly selected and analysed in order to elucidate the reasons for complaints. 58 cases were related to lumbar disc herniation treatment. RESULTS: Of these 58 cases, 52 complaints were lodged against hospitals; six against primary health care providers. Seven patients had been primarily observed or non-operatively treated; 55 were eventually operated on, eight with recurrent disease. Nearly all complaints were related to the outcome of surgery (72%) and delay of diagnosis/surgery (21%). Several serious complications occurred; one patient died. Five patients had cauda equina syndrome; a further seven had neurological deficits from distal spinal nerve roots. In 17 cases (29%) the complaints were accepted, while 41 complaints (71%) were rejected. INTERPRETATION: In lumbar disc herniations both surgery, observation and non-operative treatment may lead to severe complications. It is important to select the right patients for surgery and to provide good information.

Adult↗
PubMed2002

Tissue response during monofocal and bifocal leg lengthening in patients.

The purpose of this investigation was to compare the tissue response during mono- and bifocal limb lengthening. The study includes four patients undergoing leg lengthening. All patients started out bifocally with a total diurnal distraction of 1.75 mm, but proceeded monofocally with a rate of 1 mm a day when the distal distraction was terminated due to contractures or pain. The tissue response was monitored by registration of axial force in the distraction rods. The force increased linearly during bifocal lengthening, but culminated or decreased in the period of monofocal lengthening. Average tissue stiffness, defined as the immediate force increase due to each 0.25 mm distraction increment, was significantly higher in the bifocal lengthening phase. The force decay between each distraction was significantly lower during bifocal lengthening, thus indicating decreased tissue accommodation. Details in the force registrations indicated that the soft tissue, not the regenerate, was the main contributor to the tensile force. Conclusively, the tissues at the two osteotomy sites do not lengthen independently. Bifocal lengthening exposes the entire soft tissue to large loads, resulting in increased tissue stiffness and reduced ability to adapt to the increased length. Accordingly, bifocal leg lengthening requires special attention to soft tissue adaptation.

Fracture Healing↗
PubMed2002

High frequency distraction improves tissue adaptation during leg lengthening in humans.

The present study investigates the effect of distraction frequency on the development of tensile force in the tissues during lengthening. Two patients with bilateral Ilizarov leg lengthening underwent distraction with high frequency in one leg and low frequency in the other. The clinical situation represented a unique model for investigating the effect of distraction frequency, as each individual served as its own control. Both patients had double level lengthening. Distraction frequency at the proximal lengthening zone was 0.25 mm x 4 in the first leg and 1/1440 mm once every minute in the other. Total diurnal distraction at the proximal metaphysis was 1 mm in both legs. In addition, a distal metaphyseal distraction of 0.25 mm x 3 daily was performed on each leg. The tissue's mechanical response was monitored by measuring the tensile force at the proximal osteotomy. Both patients experienced a significant lower level of force during the high frequency lengthening. The lower level of force was concluded to be due to improved soft tissue adaptation, rather than reduced bone regeneration. Accordingly, high distraction frequency was considered favourable to low frequency, and is recommended in large lengthenings where high force levels are expected.

Adaptation, Physiological↗
PubMed2002

Reduced lengthening index by use of bifocal osteotomy in the tibia: comparison of monofocal and bifocal procedures with the Ilizarov external fixator.

We lengthened 63 tibial segments in 49 patients, performing a monofocal osteotomy on 31 segments and a bifocal osteotomy on 32 segments. In the monofocal osteotomy group, the average lengthening was 4.8 (2.4-7.1) cm with a lengthening index (LI) of 1.7 (0.9-4.4) months/cm. In the bifocal osteotomy group, the average lengthening was 7.4 (4.9-10.0) cm and with a LI of 1.0 (0.7-2.1) months/cm. The difference in LI between the groups was statistically significant, but more major complications, like persistent ankle joint contracture and pseudarthrosis in the callotasis lengthening zone, occurred with bifocal lengthening.

Adolescent↗
PubMedDate not supplied

Effects of heel height and shoe shape on the compressive load between foot and base: a graphic analysis of principle.

Even in the ever-changing and increasingly technical realm of medicine, common sense approaches are needed. We can still learn from our predecessors by using their practical and simple methods. In this article a graphic approach in the sagittal plane is used to explain the relationship between the heel height of a shoe and load under the foot. By using an elementary theoretical model based on schematic sketches, an analysis of principle can be performed to calculate the change in the distribution of mechanical stress in the planta with change in foot orientation. The model shows that when standing posture remains unaltered, load under the forefoot increases and load under the heel decreases with elevated heel height and the corresponding changes in shoe shape. These results can be confirmed by pedobarographic and gait-analysis measurements, but the graphic method can be used without application of advanced instrumentation. The rationale behind the model is to use common terms and simple means to facilitate a more fundamental understanding of complex mechanical orthopedic problems. The method is meant to be a helpful supplement to clinical judgment in the many situations in which advanced instrumentation is not available.

Ankle Joint↗