Fat extravasation due to unreamed and experimentally reamed intramedullary nailing of the sheep femur

Aim

To compare systemic fat extravasation in unreamed and experimentally reamed nailing.

Methods

An osteotomy was created in the proximal third of the femoral shaft in 16 sheep, and intramedullary pressure increase and fat extravasation were monitored for the two nailing techniques.

Results

The highest intramedullary pressures, median 2700 mmHg, and highest percentages of fat extravasation, peaking at almost 90% of fat, were found for the unreamed nailing technique. The values for the reamed group were significantly lower.

Conclusions

The extravasation of intramedullary fat can be attributed to the great increase in intramedullary pressure that occurs during unreamed nailing. Correctly performed intramedullary reaming with the new reaming system produces lower pressures and much less systemic fat extravasation, reducing the risk for fat embolism.     

Serial measurement of lymphocytotoxic antibody and response to nonmatched platelet transfusions in alloimmunized patients

Serial evaluations of lymphocytotoxic antibody (LCTAb) and responsiveness to random donor platelet transfusion were reviewed in 234 patients who had developed LCTAb at some time during their treatment course. Seventy (30%) of these patients had significant falls in antibody levels. In 44 patients these declines occurred after further antigenic exposure was reduced either because no transfusions were administered or only histocompatible platelets were transfused. Forty patients with declines in LCTAb levels who were previously refractory to platelet transfusion were rechallenged with random donor platelets. Thirty-four of 35 clinically evaluable patients had good responses to these unmatched transfusions for 2 weeks to 36 months, and in 21 patients antibody did not return despite repeated transfusions. Thus, serial LCTAb measurements are helpful in the management of alloimmunized patients. Many patients will have decreases or a loss of LCTAb, either permanently or transiently, and can be successfully supported with more easily available unmatched random donor platelet transfusions.     

Biomechanics of the craniocervical region: the alar and transverse ligaments

In the treatment of spine fractures and fracture-dislocations, stability of the spine is one of the major objectives. In the craniocervical joint, the alar and transverse ligaments provide much of the stability of the healthy spine. Because the anatomy appears well described, the contribution of each of these structures so far has received little attention. The alar ligament restrains rotation of the upper cervical spine, whereas the transverse ligament restricts flexion as well as anterior displacement of the atlas. A lesion in one or both structures can produce damage to the neural structures and/or cause pain. To investigate the possible role of each of these ligaments, a mechanical and histologic study of the upper cervical spine was made. The bone-ligament-bone complex of the alar and transverse ligaments was subjected to uniaxial mechanical testing in seven specimens. The alar ligaments had an in vitro strength of 200 N, and the transverse ligaments had an in vitro strength of 350 N. Histologic analysis revealed a mainly collagenous nature of these ligaments. Clinical evidence (broken odontoid processes) suggests that the transverse ligament is strong enough to withstand physiologic loads. The alar ligament, on the other hand, due to its lower strength and its axial direction of loading, might be prone to injury and therefore require stabilization of the appropriate vertebra more often than normally is assumed.     

Hemostatic plug formation in normal and von Willebrand pigs: the effect of the administration of cryoprecipitate and a monoclonal antibody to Willebrand factor

Hemostatic plug (HP) formation was investigated in the ear bleeding time incision in normal and von Willebrand pigs. HP volume was calculated by integrating the areas of serial sections. In normal pigs (n = 11), platelets immediately formed a layer on the surface of the cut channel. Platelet aggregates formed at the ends of transected vessels and gradually enlarged. Finally, all transected vessels were occluded by HP and bleeding stopped. In contrast, large HPs were formed in the incision in von Willebrand's disease (vWD) pigs (n = 4); these HPs did not cover the ends of the transected vessels, which continued to bleed, allowing the formation of large hemostatically ineffective platelet aggregates in the incision. Canals traversed these HPs, and bleeding from the open vessels may have continued through them. After infusion of cryoprecipitate into a vWD pig, the bleeding time shortened, and the morphological findings of the HPs were similar to those of normal pigs. In normal pigs (n = 3) infused with an anti- Willebrand factor monoclonal antibody, which prolonged the bleeding time, a large HP formed in the incision, similar to that observed in the vWD pig. The volume of the normal and vWD HPs increased with time. These in vivo findings suggest that Willebrand factor is involved in the localization of the HP to the damaged vessel and may also play a role in platelet-platelet interaction. A computerized morphometric technique was used for measuring the volume of the hemostatic plugs and the distance of sequential points on the perimeter of the HP from the center of selected bleeding vessels.     

Diffusion in the gas phase: the effects of ambient pressure and gas composition.

Gas transport across the pores of a hen's egg shell occurs by a process of diffusion in the gas phase and for any particular gas depends upon its diffusion coefficient and the pore geometry. The egg shell is thus a convenient model for measuring the diffusive permeability of the shell to a given gas species when its diffusion coefficient is altered by either a change in ambient pressure or by changing the second gas in the diffusion pathway. In this study the permeability of the shell to water vapor and O2 was inversely proportional to ambient pressures over the range of .06 to 8 atmospheres' absolute (ata). The permeability of the shell to water vapor in a He environment (KH20, He) was 2.4 times KH20, air. If KO2, N2 is taken as unity, the permeabilities of the shell to O2 in He, Ar, CO2 and SF6 are 3.38, 0.95, 0.88, and 0.52, respectively. The results are interpreted in terms of the Chapman-Enskog equation, from which binary diffusion coefficients can be predicted for given gas pairs and ambient pressures. These results also provide explantations for the structural modification of egg shells in altitude-adapted chickens, and for the reduced insensible water loss in man at high ambient pressure.     

VerstÄrkung der radiotherapeutischen wirkung auf HeLa-Zellen durch gemcitabine

BACKGROUND: Gemcitabine (2'.2'-difluorodeoxycytidine; dFdC) is a new nucleoside analog with promising activity in different solid tumors in vivo and in vitro. As published up to now, combined with irradiation dFdC demonstrates a radiosensitizing effect on pancreas and colon carcinoma cell lines. We investigated the influence of dFdC on the radiosensitization of human squamous carcinoma cells of the cervix (HeLa-cells, ATCC CCL-2). MATERIAL AND METHODS: Under standardized conditions monolayer cultures of HeLa-cells were incubated in medium with dFdC for different times (4 to 24 hours) and exposed to different concentrations (0.003, 0.01 and 0.03 mumol/l). Irradiation (2 to 6 Gy, electron beam) followed immediately or 12 hours after dFdC-exposure. Cell survival was determined by colony forming assay. Using the linear-quadratic model cell survival curves were fit after correction for drug-induced cytotoxicity and the mean inactivation dose (MID) was calculated. Radiation enhancement was defined as the ratio MIDRT(= Control)/MIDRT + dFdC > 1. RESULTS: Exposed to gemcitabine for 4 and 8 hours and followed by immediate irradiation the radiation enhancement ratio (Table 1) is 1.07 to 1.14 and 1.04 to 1.22, respectively, if dFdC concentration is > or = 0.01 to 0.03 mumol/l. Further increase of the irradiation effect is demonstrated in cells exposed to > or = 0.003 to 0.03 mumol/l dFdC for 16 and 24 hours (radiation enhancement ratio 1.08 to 2.0 and 1.08 to 2.48, respectively) (Figure 3). If irradiation is applied 12 hours after 24-hour-exposure (0.01 and 0.03 mumol/l) the enhancement ratio was 1.18 and 1.7, respectively (Figure 4). CONCLUSIONS: In cell cultures the assays combining irradiation with dFdC demonstrate that dFdC is a potent radiation sensitizer of HeLa-cells. The effect of irradiation on cells pre-treated with non- and hardly cytotoxic concentrations of dFdC is increased in dependence of dose and time of exposure.