Stress protection by external fixation of the rabbit tibia

Osteopenia of the tibia and femur caused by an external fixator in the tibia was studied in 14 rabbits. Eight rabbits were treated with a complete unilateral external fixator in one tibia, whereas the other tibia served as control. The other 6 animals had one leg operated on with inserting of all the pins but without the frame. This technique was chosen to compare osteopenia caused by stress protection and the effect of the pins. After 6 weeks, we found a 7 percent reduction in the bone mineral content in the tibial diaphyseal segment between the pins of the external fixator and no bone loss in the tibia that were operated on with only pins. In the femurs, there was a smaller decrease in the bone mineral content: respectively 3.2 percent (complete frame) and 2.9 percent (only pins). On all the operated on tibiae, there was an increase in the bone mineral content around the pins both proximally and distally.     

Cytotoxic properties of eosinophil granule major basic protein for tumor cells

BACKGROUND: Eosinophil granule major basic protein (MBP) mediates many eosinophil-associated immune functions and it adheres eosinophils to parasite targets. METHODS: We compared the toxicities of MBP and melittin to K562 and HL-60 cells using five cytotoxicity methods. RESULTS: Trypan blue staining, propidium iodide/ CellTrackertrade markGreen staining and incorporation of 14C-leucine assays indicated that MBP damages most cells by 1 h. In contrast, 51Cr and lactic dehydrogenase (LDH) release assays indicated that MBP damages most cells only at 20 h. All five methods indicated that melittin damages nearly all cells by 1 h. To resolve these discrepancies, the procedures were modified. Without cell transfer, dye staining methods showed that MBP produces very little cytotoxicity at 4 h. 51Cr and LDH assays, modified to mimic cell transfer, showed increased cytotoxicities at 4 h. The 14C-leucine assay modified by solubilization of cells with SDS and by trichloroacetic acid precipitation showed increased recovery of labeled protein and, thus, lower cytotoxicity, about 50%, at 4 h. CONCLUSION: Overall, MBP's ability to cause molecular and cellular adhesion confounds cytotoxicity measurements. A modified 14C-leucine assay overcame MBP's adhesiveness and provided an accurate measure of cytotoxicity.     

No adverse effects of early weight bearing after uncemented total hip arthroplastyA randomized study of 20 patients

Experimental fibular defects in 16 rats were filled with an acid decalcified homogenous bone matrix (bone inductive material). Autogenous bone grafts in corresponding defects in the other legs of the same rats served as controls. After 3 months, 11 of the 16 defects filled with bone inductive material healed with bony union, but only 4 of the 16 defects treated with autogenous bone grafts had healed. The results suggest that bone inductive material can repair bone defects which are too large to be healed by autogenous bone grafts.     

Unstable versus stable uncemented femoral stems: a radiological study of periprosthetic bone changes in two types of uncemented stems with different concepts of fixation

Introduction Uncemented stems in total hip arthroplasty (THA) are used increasingly often because they are believed to offer a reliable long-term fixation. However, periprosthetic bone remodelling has been a worrying issue. A proximal demineralization has been noted in femurs with well-fixed stems, and it has been explained as by-passing of mechanical forces along the fixed implant (stress-shielding). Aseptic loosening has been a major problem in several uncemented series with earlier designs. The objective for this study was to investigate how the host bone adapts to a loose stem compared with a well-fixed stem after a long time.Materials and methods An investigation with dual-energy X-ray absorptiometry (DEXA), scintimetry and radiological assessment was carried out in 20 patients 8 years after a THA for arthrosis with two different uncemented stems. Ten patients received a stem coated with polytetrafluoroethylene (Anaform); all prostheses showed migration and were considered unstable. Ten patients received a hydroxyapatite-coated stem (Bi-Metric); no prosthesis migrated.Results Different remodelling patterns were seen. In the unstable group, the periprosthetic bone mineral density (BMD) was significantly reduced along the entire stem, while in the stable group only proximal bone loss was seen. The scintigraphic uptake was increased under the stem tip in both groups, and among unstable stems uptake was also increased in the calcar region.Conclusion The assessment of periprosthetic bone remodelling after uncemented THA with long-term observation shows a different host-bone response in stable versus unstable femoral implants. Prior to a femoral revision, measurement of the BMD could be beneficial; it may guide the surgeon when deciding which surgical technique to use.     

Bone mineral loss after Colles' fracture. Plaster case and external fixation equivalent

The bone mineral content of the radius and ulna was analyzed in 31 postmenopausal women with displaced Colles' fractures. Sixteen fractures were treated with a below-the-elbow plaster case and 15 with primary external fixation. The bone mineral content of the forearm bones was measured with a photon absorptiometer 9 (6-24) months later. There was a mean 15 percent mineral decrease in the radius, but no difference between the two treatment groups. The decrease did not correlate with the age of the patient, nor was there any correlation with grip strength or range of wrist motion. The more severe fractures, according to the Frykman classification, had a more pronounced mineral loss than the simpler fractures.     

Stress protection by external fixation of the rabbit tibia

Osteopenia of the tibia and femur caused by an external fixator in the tibia was studied in 14 rabbits. Eight rabbits were treated with a complete unilateral external fixator in one tibia, whereas the other tibia served as a control. The other 6 animals had one leg operated on with inserting of all the pins but without the frame. This technique was chosen to compare osteopenia caused by stress protection and the effect of the pins. After 6 weeks, we found a 7 percent reduction in the bone mineral content in the tibial diaphyseal segment between the pins of the external fixator and no bone loss in the tibia that were operated on with only pins. In the femurs, there was a smaller decrease in the bone mineral content: respectively 3.2 percent (complete frame) and 2.9 percent (only pins). On all the operated on tibiae, there was an increase in the bone mineral content around the pins both proximally and distally.     

Fractures of the ipsilateral femur after total hip arthroplasty

The aim of this study was to investigate the predisposing factors, fracture location, treatment, and final outcome of femoral fractures after total hip arthroplasty (THA). From 1975 to 1983, 28 patients were seen with 29 fractures on the same side as the prosthesis. Most of the fractures were caused by minor trauma, and prior hip surgery was the most common predisposing factor. Two patients underwent early operation and six were treated with protected weight bearing. Twenty-one underwent initial skeletal traction, and 14 of these fractures united without further surgery. Six of the patients treated with initial skeletal traction were operated on early, mainly by osteosynthesis, due to poor fracture alignment. Three of these fractures united, but one subsequently required revision arthroplasty because of loosening of the femoral component. Two patients died and three had a permanent pseudarthrosis or a Girdlestone resection. Nineteen of the 21 fractures not operated on united and five of the eight operated united. The results indicate that when good fracture alignment is achieved with traction, union is not jeopardized by either the prosthesis or the cement.     

Large femoral bone loss after hip revision using the uncemented proximally porous-coated Bi-Metric prosthesis: 22 hips followed for a mean of 6 years

Background and purpose Periprosthetic bone loss after uncemented femoral hip revision is a matter of concern. We have used a proximally porous- and hydroxyapatite-coated prosthesis (Bi-Metric) in revision since 1989 and now we report the bone changes. This prosthesis is intended to distribute the forces more evenly and to avoid proximal femoral unloading.Methods 22 patients were unilaterally reoperated because of aseptic loosening. Only patients with a healthy contralateral hip were included. Mean age at revision was 69 (55–80) years. Bone defects were graded by Gustilo-Pasternak and Endo-Klinik classifications. Clinical assessment was performed with Harris hip score. We used radiographs and dual-energy X-ray absorptiometry to evaluate migration, femoral remodeling, and bone mineral density after 72 (30–158) months.Results The mean Harris hip score was 74 (30–100) points at follow-up. Mild thigh discomfort was present in 1 patient and moderate thigh pain in 3 patients. There was no loosening or subsidence. Osteolysis seen at revision had diminished in 19 of the 22 hips at follow-up. We noted a large reduction in bone mineral density. It was most pronounced in Gruen regions 1, 2, 6, and 7.Interpretation Revision with this stem is a reliable procedure; however, we noted a large degree of proximal bone loss that could lead to later mechanical complications or fractures.     

Clodronate increases mineralization of callus after Colles' fracture: A randomized,double-blind,placebo-controlled,prospective trial in 32 patients

In a randomized study of 32 postmenopausal women with a Colles' fracture, we studied whether 8 weeks of treatment with clodronate, a bisphosphonate, could prevent posttraumatic osteopenia. The patients were treated with a plaster splint for 4 weeks. The bone mineral density (BMD) of the forearm bones was measured at 2 levels with dual-energy x-ray absorptiometry (DEXA) 2, 6 and 12 months after the fracture. At 2 months, in the clodronate group, there was a median 53% higher BMD in the fracture region of the radius than in the uninjured radius. In the placebo group, we found a 33% higher BMD in the fractured radius at that level than in the uninjured radius. This increase in BMD of the fractured radius, caused by clodronate, was statistically significant. At 12 months, the BMD of the fracture side had been reduced by 17% and 12%, respectively, at that time it was still significantly increased in the clodronate group alone. In the ulna at the same level, we found no significant changes in BMD in either group on either side at any time. At 2 months, at the level between the distal and middle thirds, in the fractured radius, the median BMD was 7% lower in the clodronate group and 6% lower in the placebo group than in the uninjured radius. Although the reduction in BMD at that level was significant, there was no difference between the two treatment groups. At this level, the ulna on the fractured side showed a similar pattern, with a 5% lower BMD in the clodronate group and a 4% lower BMD in the placebo group. This osteopenia showed a small but significant progression on the fractured side after 6 and 12 months.