Biomedical subjects

T O Fjeld

Publications and source records attributed to T O Fjeld.

9 recordsLinked to original sources

PubMed1995

Changes in Na+, K(+)-adenosinetriphosphatase, citrate synthase and K+ in sheep skeletal muscle during immobilization and remobilization.

The K+ balance and muscle activity seem to interact in a complex way with regard to regulating the muscle density of Na(+)-K+ pumps. The effect of immobilization was examined in ten sheep that had low muscle K+ content. Three additional sheep served as untreated controls. After being brought from pasture to sheep stalls one hindlimb was immobilized in a plaster splint for 9 weeks, and in five of the animals remobilization was carried out for a further 9 weeks. The weight bearing of the leg in plaster was recorded by a force plate. Open muscle biopsies from the vastus lateralis muscle were obtained before the study, after 9 weeks of immobilization, and after another 9 weeks of remobilization. The Na(+)-K+ pump density was measured as [3H]-ouabain binding to intact tissue, and citrate synthase activity was measured in tissue homogenate. The tissue content of K+ was measured in fat-free dried tissue. Muscle K+ content increased linearly by almost 70% through the 18-week period independent of intervention. Immobilization reduced thigh circumference by 8% (P < 0.05). A slight decrease in the area of type I fibres at 9 weeks and a slight increase at 18-weeks was found. The [3H]-ouabain binding was reduced by 39% and 22% in the immobilized and control legs, respectively, whereas citrate synthase activity was reduced by about 30% in both legs after 9 weeks of immobilization. During remobilization both the [3H]-ouabain binding and the citrate synthase activity increased to the same level as in the control animals. The plaster cast significantly reduced mass bearing of the immobilized leg, and a corresponding reduction in muscle activity must be assumed to have occurred in both legs as judged from citrate synthase activity. We concluded from this study that the reduction in the [3H]-ouabain binding during immobilization independent of an increase in muscle K+ content points to muscle activity as a strong stimulus for control of Na(+)-K+ pump density.

Animals↗

PubMed1990

Biomechanical factors in the metaphyseal- and diaphyseal-lengthening osteotomy. An experimental and theoretic analysis in the ovine tibia.

A post hoc comparison of the mechanical factors that affected the outcome of experimental metaphyseal- and diaphyseal-lengthening osteotomies in sheep tibiae was performed. The resulting motions between bone segments at the metaphyseal and diaphyseal levels were estimated using measured fixator stiffnesses, postural muscle activity, ground reaction forces, and calculated internal and external loads. Relative displacements of bone segments of up to 2.8 degrees were estimated in postural activities; displacements were up to 4.9 times larger at the metaphyseal than at the diaphyseal osteotomy level. The results suggest that due to these increased motions, mechanically inferior conditions for healing at the metaphyseal-lengthening osteotomy level may counteract any supposedly superior biologic healing potential that the metaphyseal region of the bone may have compared with the diaphyseal region. These results correlate well with the clinical findings of the earlier animal study.

Animals↗

PubMed1989

Limb lengthening by epiphyseal distraction in chondrodystrophic bone: an experimental study in the canine femur.

Epiphyseal distraction of the left distal femur was accomplished in 18 chondrodystrophic dogs (age 19-22 weeks). A distraction rate of 0.5 mm/day was applied by means of a unilateral device. Epiphysiolysis occurred after 4 to 9 days. Lengthening was continued for 3 weeks. The animals were killed at 3 (Group 1; n = 5), 19 (Group 2; n = 10), and 71 (Group 3; n = 3) weeks after the end of distraction to verify the magnitude of elongation at removal of the device (Group 1) and at the time of growth cessation (Groups 2 and 3), and to register possible permanent secondary joint changes (Group 3). The average lengthening of 1.2 cm (12.3%) at removal of the device was reduced to 0.7 cm (6.4%) at cessation of growth. The middiaphyseal diameter of the elongated femur was enlarged after the lengthening procedure in all animals. The average torsional strength of the elongated femur compared with the contralateral control was 83% in Group 1, 98% in Group 2, and 107% in Group 3. Degenerative changes were observed in the knee joints of three animals in each group. A two-way analysis of variance was applied for all data sets to test differences between control and elongated bones and between time periods. The reduction in gained length by retardation of residual growth in the distal femur was significant (p less than 0.05). The difference in external diameter between lengthened and control bones was significant in Groups 1 and 3 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Achondroplasia↗

PubMed1989

Lengthening osteotomy in the metaphysis and diaphysis. An experimental study in the ovine tibia.

In 20 sheep, aged seven to eight months, a tibial lengthening osteotomy was performed to compare the process of repair of the metaphyseal and diaphyseal regions of the bone. Analogous to clinical lengthening, two frame configurations of a bilateral external fixation device were used to obtain adequate fixation of the bone segments in the metaphyseal and diaphyseal lengthening osteotomies. A daily distraction rate of 1 mm for 4.5 weeks yielded an average length increase of 2.6 cm (12.5%). After death at 4.5 weeks postdistraction, the elongated bones were tested mechanically with the contralateral tibiae as controls. No significant difference in relative torsional strength of the elongated tibiae was found between the two groups. Inferior mechanical stability of the bone segments in metaphyseal compared with diaphyseal lengthening (due to differences in frame rigidity and distribution of muscular moments) influenced healing to such an extent that any superior biologic, osteogenic potential in the metaphyseal bone region was nullified. With the clinical use of two configurations of a given external device necessary for fixation of the bone segments in a metaphyseal or diaphyseal lengthening osteotomy, the empirically accepted idea that metaphyseal healing is superior may not be correct.

Animals↗

PubMed1988

Limb lengthening by low rate epiphyseal distraction. An experimental study in the caprine tibia.

Low-rate epiphyseal distraction of the left proximal tibia using a modified bilateral Hoffmann external fixation device, was accomplished in 14 goats (age 6-7 months). Daily distraction at a rate of 0.5 mm was continued for 5.5 weeks. Epiphysiolysis occurred after 5-9 days. After distraction had been discontinued, the external device was left in situ for fixation for 4 weeks. The animals in group 1 (n = 6), group 2 (n = 3), and group 3 (n = 5) were killed at 4, 16, and 32 weeks, respectively, from the end of the distraction period. The proximal growth plate of the elongated tibia appeared radiolucent at the conclusion of the study but was less distinct and reduced in height as compared with the control leg. The gained length at the end of the distraction period was on the average 2.2 cm (11.9%). This gain in length was reduced with further growth. In group 3, the final gain in length was reduced to half. A reduced cortical thickness of the bone within the area subjected to distractional force was observed. This finding is attributable to stress protection. An interesting observation comparing control and operated tibia was an increase of the cross-sectional diameter of the elongated bone. Both tibiae of all animals were tested mechanically. The torsional strength of the elongated tibiae as compared with controls was on the average 29% in group 1, 79% in group 2, and 95% in group 3. We conclude that leg lengthening by low-rate epiphyseal distraction in the proximal tibia is a justifiable alternative to other lengthening procedures in individuals approaching adolescence. In juveniles, lengthening by epiphyseal distraction may result in reduction in the longitudinal growth.

Animals↗

PubMed1988

Limb lengthening by diaphyseal corticotomy, callus distraction, and dynamic axial fixation. An experimental study in the ovine femur.

Limb lengthening of the left femur was performed in 12 sheep, 7-8 months of age. After weakening of the cortex by drill holes, a controlled fracture was created in the diaphysis. The bone segments were fixed in reduced position using a unilateral external fixation device. The fixator was left in neutral position for 10 days postoperatively when lengthening started. By means of daily distraction at a rate of 1.0 mm once a day for 3 weeks, an average lengthening of 1.9 cm (11.9%) was obtained. Two weeks after distraction had been discontinued, distinct callus bridging of the lengthening zone was confirmed radiographically in all animals. At this time the rigid state of fixation was converted to a system allowing axial compression by loading in half the animals. The other half of the animals served as controls with the fixator remaining unchanged. The external device was left on until 5 weeks after the end of distraction. At this time the animals were killed. Both femora of all animals were tested mechanically in torsion. The average ultimate torsional strength of the elongated femur compared with control was 71% in the group with dynamic axial fixation and 65% in the control group. No significant difference in relative strength of the tested bones in the two groups was found. We conclude that intermittent axial compression by loading during consolidation had no significant effect on the bone-healing process evaluated by radiography and mechanical testing.

Animals↗

PubMed1987

Limb lengthening by epiphyseal distraction. An experimental study in the caprine femur.

Epiphyseal distraction of the left distal femur was accomplished in 10 goats (aged 3-4.5 months). A modified Hoffmann external fixation device was used as a unilateral distraction frame. A distraction rate of 1.5 mm/day was applied for 5.5 weeks. Epiphysiolysis occurred after 3-7 days of distraction. After the lengthening procedure, the growth plate had reduced in height in eight animals on radiographic examination. In two animals the growth plate was fused. Three animals were killed at 4 (Group 1) and 8 (Group 2) weeks and four animals at 16 (Group 3) weeks after the end of the distraction period. The gain in leg length obtained by distraction was reduced owing to growth retardation in the distal femur of the operated limb. The average final lengthening was 24.9, 19.4, and 13.4% in Groups 1, 2, and 3, respectively. Femur and tibia from both sides were tested mechanically in torsion. Only one femur fractured in the elongation area. All but one elongated femur fractured in the area of the diaphysis subjected to distractional force. The torsional strength of the elongated femur compared with control was reduced to approximately 50% in all groups. The corresponding torsional strength of the tibia on the elongated extremity compared with control was reduced to approximately 75% in all groups. The difference in relative strength of femur compared with that of tibia was statistically significant. This finding can be explained by a stress-protective effect on the femur in the distraction area caused by the external device.

Animals↗

PubMed1985

Morphological changes in continuously stretched skeletal muscles in sheep.

The effects of continuous elongation of skeletal muscles were studied on six sheep who underwent a lengthening osteotomy of the right tibia. Open muscle biopsies were taken from the biceps femoris muscle preoperatively (Group A), after 5 weeks of bone distraction (Group B) and after another 5 weeks without further distraction (Group C). The size and distribution of type 1 (slow-twitch) and type 2 (fast-twitch) muscle fibres were determined from sections stained for myofibrillar ATPase activity. All sections were also evaluated by light microscopy, especially with regard to myopathic changes. The type 2 fibres showed a significant decrease in size from group A to B and from group B to C. The reduction in fibre size from group A to C was 44.2%. The type 1 fibres, on the other hand, showed no significant differences in mean fibre size between the groups. However, there were considerable individual variations in type 1 fibre size between the groups. The distribution of both fibre types was similar in groups A and B (appr. 17% type 1 fibres) whereas the relative number of type 1 fibres was reduced to 12.4% in group C (P less than 0.01). Myopathic changes, i.e. muscle fibre necroses, were not seen in any of the groups. It is concluded that the type 2 fibre atrophy is mainly caused by muscular inactivity during the postoperative period, but an additional effect of continuous stretching of the muscle cannot be excluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Growth retardation after experimental limb lengthening by epiphyseal distraction.

Growth retardation occurring as a result of limb lengthening by epiphyseal distraction in two animal species was quantified by using femur or tibia as the experimental bone. The growth plate subjected to distraction appeared radiolucent after the lengthening procedure but was less distinct and had reduced height as compared with the control. In seven of 22 animals, the growth plate of the lengthened bone appeared to close earlier than in the control. After lengthening, bilateral longitudinal growth was evaluated semiquantitatively from radiographs until growth had ceased or residual growth was negligible. Growth retardation was consistently experienced in all animals, with an average reduction in growth potential of each study ranging from 40 to 70%. The results show that epiphyseal distraction is a valid method of limb lengthening, but it appears to have a consistently harmful effect on the growth plate and should be used clinically only in patients close to maturity.

Age Factors↗