| 1. |
- Kaastad, T S, et al.
(författare)
-
Effect of intensive training on lower leg structural strength: an in vivo study in ovariectomized rats
- 1997
-
Ingår i: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 7:4, s. 220-225
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the effect of training on the in vivo tibial structural strength during the development of post-ovariectomy osteoporosis. Seventeen mature Wistar rats (215 g) were ovariectomized and randomized into two groups. The sedentary control group was kept cage confined, while 3 days postoperatively the trained group started treadmill running with high intensity for 1 h 5 days a week. All were given a low calcium diet (Ca 0.01%). After 8 weeks the animals were anaesthetized and the right lower legs fractured during muscle contraction in three-point ventral bending. The left legs were fractured at the same level after removal of all soft tissues. Histomorphometry of the meta- and diaphysis of the distal tibiae was performed. Weight-gain was higher in sedentary (108 g) than in trained (61 g) rats (P<0.0001). There were no significant differences in mechanical results between the groups at in vivo or in vitro fracture. Correcting for weight-gain differences did not change these results. Histomorphometry showed no differences between the groups. Corticosterone was higher in trained than in sedentary rats (P<0.02), and corticosterone may have had a negative influence both on muscle and bone. The study could not show an effect of high intensity training in the early phase after ovariectomy on in vivo or in vitro fracture strength.
|
|
| 2. |
- Kaastad, T S, et al.
(författare)
-
Effects of clodronate on cortical and trabecular bone in ovariectomized rats on a low calcium diet
- 1997
-
Ingår i: Calcified Tissue International. - : Springer Science and Business Media LLC. - 1432-0827 .- 0171-967X. ; 61:2, s. 158-164
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the contribution of a low calcium diet to the cortical and trabecular osteoporosis seen in ovariectomized rats after 7 weeks on a low calcium diet and to investigate the effects of the bisphosphonate clodronate on this development of osteoporosis. Thirty-six mature, female Wistar rats were randomized into four groups: Ovx-B (bisphosphonate) and Ovx-C (control) were ovariectomized, and Sham-Ca (low calcium) and Sham+Ca (normal calcium) were sham operated. The first three groups were fed a low calcium diet (0.01%) and Sham+Ca normal rat chow (Ca 1.1%). The Ovx-B received 10 mg/kg s.c. clodronate daily for nine weeks, and Ovx-C, Sham-Ca, and Sham+Ca received the same volumes of saline. Bone mineral turnover measured as 85Sr-uptake was increased in all low calcium groups compared to Sham+Ca. The Sham+Ca femora had higher dry weight and ash weight than the other groups, and Ovx-C had higher dry weight compared with Ovx-B and Sham-Ca. Calcium content was lower in both Ovx groups compared to both Sham groups. Magnesium was lower in all groups compared to Sham+Ca and higher in Ovx-B compared with Ovx-C. In the femoral shaft, Sham+Ca had significantly higher ultimate bending moment, energy absorption, and deflection compared to the other three groups. Ultimate bending moment was higher in Sham-Ca than in Ovx-C. Stiffness was increased in both Sham+Ca and Ovx-B compared to Ovx-C. The maximum stress in the femoral midshaft was higher in Sham+Ca than in the other groups, and higher in Ovx-B than in Ovx-C. Histomorphometry showed increased medullary area in all low calcium groups compared to Sham+Ca and larger cortical area in Sham+Ca and Ovx-B compared to Ovx-C. Compared to Sham+Ca the trabecular bone volume was decreased to 30% in Sham-Ca and to 9% in Ovx-C, but was unchanged in Ovx-B. The low calcium diet generally increased bone mineral turnover and reduced the tibial bone volume. Femoral changes led to a reduction of cortical fracture strength and maximal stress. Ovariectomy in addition to a low calcium diet reduced femoral strength even more. Daily injections of clodronate to ovariectomized rats on a low calcium diet increased femoral shaft stiffness and maximum stress, and clodronate preserved both trabecular and cortical tibial bone volume completely.
|
|
| 3. |
- Kaastad, T S, et al.
(författare)
-
Vitamin D deficiency and ovariectomy reduced the strength of the femoral neck in rats
- 2001
-
Ingår i: Calcified Tissue International. - : Springer Science and Business Media LLC. - 1432-0827 .- 0171-967X. ; 69:2, s. 102-108
-
Tidskriftsartikel (refereegranskat)abstract
- Vitamin D (vit D) deficiency is common in the elderly, and the aim of this study was to investigate whether vit D deprivation in ovariectomized (ovx) and normal rats would reduce fracture strength. Forty mature female Wistar rats were randomized into four groups: two were ovariectomized (ovx) and two were sham-operated (sham). One ovx and one sham group were fed a vit D-deficient diet (Ovx-D and Sham-D), and the control groups were fed normal rat chow (Ovx and Sham) for 12 weeks. Vit D deficiency was substantiated after 12 weeks by undetectable serum concentrations of 25OHD in the Sham-D and Ovx-D groups. 85Sr activity was lower in Sham-D than in the other groups (P < 0.005). Tibial and femoral weights and lengths showed no differences. Distal tibial trabecular bone volume was reduced in both ovx groups compare with sham (P < 0.005). Bone mineral density (BMD) was higher in sham than in Sham-D and both ovx groups (P < 0.005). Femoral area moment of inertia increased and ultimate stress decreased in Ovx-D compared with ovx (P < 0.05). Other biomechanical properties of the femoral shafts did not differ significantly. The femoral neck was significantly weaker in Ovx-D than in the other groups. In conclusion, ovx decreased tibial trabecular bone volume and both ovx and vit D depletion reduced femoral BMD in rats. Vit D depletion reduced the ultimate stress in the femoral shaft, and the combined depletion of estrogen and vit D significantly reduced the fracture strength in the femoral neck. This fits well with clinical evidence of how postmenopausal status combined with vit D deficiency lead to an increased risk of hip fractures, making this animal model a possible tool for investigating measures to prevent such fractures.
|
|
| 4. |
- Reikeras, O., et al.
(författare)
-
Bone ingrowths to press-fit and loose-fit implants: comparisons between titanium and hydroxyapatite
- 2006
-
Ingår i: J Long Term Eff Med Implants. - Boca Raton, Fl. : CRC Press. - 1050-6934 .- 1940-4379. ; 16:2, s. 157-64
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate whether the coating of titanium (Ti) implants with hydroxyapatite (HA) might create a better fixation when titanium implants are implanted into a gap. In each of 16 rats, the medullary cavity of both femurs was entered by an awl from the trochanteric area. With steel burrs it was successively reamed to a diameter of 1.5 mm. In a random manner the proximal part of the cavity in half of the bones was reamed once again to a diameter of 2.0 mm. Nails with a diameter of 1.5 mm and a length of 34 mm were then inserted into the medullary cavity of these bones with press fit at the distal half and a gap to the bone in the proximal half. In the remaining bones the whole medullary canal was reamed to a diameter of 2.0 mm, and nails with a diameter of 2.0 mm and a length of 34 mm were introduced. In all cases, either a pure Ti nail or a Ti nail entirely plasma sprayed with HA was used in a random manner. The surface roughness of the pure Ti was characterized by Ra 2.6 microm and Rt 22 microm. Ra of HA was 7.5 microm and Rt 52 microm. At sacrifice after 16 weeks, both femurs were dissected free from soft tissues and then immersed in fixative. A specimen slice of about 5 mm in thickness was prepared from the subtrochanteric region with a water-cooled band saw. Sample preparation for undecalcified tissue followed the internal guidelines at the laboratories of the Department of Biomaterials/Handicap Research. Generally, bone contact to the nails with HA coating was more predictable than was bone contact to the Ti nails. But due to rather large variations in bone contact between the samples, statistical analyses revealed non-significant differences between the 4 groups (p = 0.083). There were no significant differences between Ti and HA coated nails of 2.0 mm (p = 0.633), nor between Ti and HA coated nails of 1.5 mm (p = 0.924). The pooled values for the 2.0 mm nails showed significantly higher bone bonding contact than the pooled values of the 1.5 mm nails (p = 0.011). Our results, then, indicate that bone bonding contact to implants with a loose fit insertion is less predictable than in press fit insertion, and HA coating seemed to be more predictable than pure Ti. However, due to large variations between the samples, the differences did not reach significant levels.
|
|
| 5. |
- Reikeras, O., et al.
(författare)
-
Hydroxyapatite and carbon coatings for fixation of unloaded titanium implants
- 2004
-
Ingår i: Journal of Long-Term Effects of Medical Implants. - 1050-6934 .- 1940-4379. ; 14:6, s. 443-454
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the interaction between bone and pure titanium, titanium coated with hydroxyapatite (HA), and titanium coated with carbon in a rat femur model. In 25 rats, the medullary cavity of both femurs was entered by an awl from the trochanteric area. With steel burrs it was successively reamed to a diameter of 2.0 mm. Nails with a diameter of 2.0 mm and with a length of 34 mm were inserted in a random manner; either a pure titanium nail, a titanium nail entirely plasma-sprayed with a 75-100-microm layer of HA or a titanium nail coated with 2-10-microm carbon. The surface roughness of the pure titanium was characterized by Ra 2.6 microm and Rt 22 microm. Ra of HA was 7.5 microm and Rt 52 microm, and of carbon Ra was 0.4 microm and Rt 4.0 microm. Twelve rats were randomized to a follow up of 8 weeks, and the remaining 13 rats were followed for 16 weeks. At sacrifice both femora were dissected free from soft tissues and then immersed in fixative. A specimen slice of about 5 mm thickness was prepared from the subtrochanteric region with a water-cooled band-saw. Sample preparation for un-decalcified tissue followed the internal guidelines at the laboratories of Biomaterials/Handicap Research. At 8 weeks the median bone bonding contact of the implants was 43% (range 0-74) in the titanium group, 39% (0-75) in the HA group, and 3% (0-59) in the carbon group. At 16 weeks the corresponding figures were 58% (0-78) in the titanium group, 51% (15-75) in the HA group, and 8% (0-79) in the carbon group. In conclusion, we found great variability in bone bonding contact. In general, carbon-coated nails had reduced bone bonding contact both at 8 and at 16 weeks as compared to pure titanium or titanium coated with hydroxyapatite.
|
|
| 6. |
- Reikeras, O., et al.
(författare)
-
Hydroxyapatite enhances long-term fixation of titanium implants
- 2006
-
Ingår i: J Long Term Eff Med Implants. - Boca Raton, FL : CRC Press. - 1050-6934 .- 1940-4379. ; 16:2, s. 165-73
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate osseous integration of hydroxyapatite coated titanium implants over time as compared to pure titanium. In 20 rats the medullary cavity of both femoral bones was entered by an awl from the trochanteric area. With steel burrs it was successively reamed to a diameter of 2.0 mm. Nails with a diameter of 2.0 mm and with a length of 34 mm were inserted into the medullary cavity; a pure titanium nail on the left side and a titanium nail entirely plasma-sprayed with hydroxyapatite (HA) on the right side. The surface roughness of the pure titanium was characterized by Ra 2.6 microm and Rt 22 microm, and HA had a roughness of Ra 7.5 (arithmetical mean roughness) microm and Rt (maximum profile height) 52 microm. The rats were randomized to a follow-up of 6 and 12 months, respectively. At sacrifice the femoral bones were dissected free from soft tissues. The bones were radiographed and then immersed in fixative. A specimen-slice of about 5 mm thickness was prepared from the region under the trochanter minor with a water cooled band-saw. Sample preparation for undecalcified tissue followed the internal guidelines at the laboratories of Biomaterials/Handicap Research. At 6 months the median bone bonding contact of the implants was 40% (range 0-92) in the titanium group and 34% (0-86) in the HA group. At 12 months the median bone bonding contact was 51% (0-97) in the titanium group and 86% (72-98) in the HA group. In conclusion, we found a significant (p = 0.001) increase in bone bonding contact from 6 to 12 months of the HA coated nails and significantly (p = 0.043) enhanced bone bonding contact in HA coated nails at 12 months as compared to pure titanium nails.
|
|
