PULMONARY EFFECTS OF FIXATION OF A FRACTURE WITH A PLATE COMPARED WITH INTRAMEDULLARY NAILING - A CANINE MODEL OF FAT-EMBOLISM AND FRACTUREFIXATION

Fat-embolism syndrome and pulmonary dysfunction may develop in multipl y injured patients who have a fracture of a long hone, Although early fixation of a fracture is beneficial, intramedullary nailing may exace rbate pulmonary dysfunction by causing additional embolization of marr ow fat, We examined the pulmonary effects of the timing and method of fixation of a fracture in a canine fat-embolism model, Fat embolism wa s induced in forty-one adult dogs by reaming the ipsilateral femur and tibia followed by pressurization of the intramedullary canal, The ani mals were divided into a control group of eight dogs that had inductio n of fat embolism alone and an experimental group of thirty-three dogs that had induction of fat embolism and internal fixation of a transve rse fracture of the middle of the contralateral femoral shaft, In the control group, four dogs each were killed four hours and twenty-four h ours after induction of fat embolism. In the experimental group, a fem oral fracture was created and fixation was performed four hours after embolic showering in fifteen animals and twenty-four hours after embol ization in eighteen animals, The two experimental groups were subdivid ed according to the method of fixation of the fracture: eleven dogs ea ch had application of a plate, nailing without reaming, and nailing wi th reaming, The pulmonary arterial pressure and the alveolar-arterial gradient were measured preoperatively during induction of fat embolism , and as long as one hour after fixation of the fracture but before th e animal was killed, The lungs, brain, and kidneys were examined for p athological and physiological evidence of intravascular fat, The intra vascular fat persisted for twenty-four hours after induction of pulmon ary fat embolism, Pulmonary arterial pressure remained elevated at fou r hours after the embolic showering, before creation and fixation of t he fracture, By twenty-four hours after the induction of fat embolism, pulmonary arterial pressure had returned to the baseline level, Neith er the creation nor the fixation of the fracture affected pulmonary ar terial pressure, In the animals that had fixation of a fracture four h ours after embolization, both nailing with reaming and nailing without reaming produced alveolar-arterial gradients that were higher than th e baseline values, whereas fixation with a plate did not change the al veolar-arterial gradient significantly from the baseline value, In add ition, the alveolar-arterial gradients in the animals that had nailing with reaming and nailing without reaming four hours after embolizatio n were, respectively, four and 3.5 times higher than that in the anima ls that had fixation of the femur with a plate, In the animals that ha d fixation twenty-four hours after embolization, none of the methods f or fixation affected the alveolar-arterial gradient, The amount of emb olic fat in the lungs, brain, and kidneys was not affected by fixation of the fracture when it was performed at either the four-hour or the twenty-four-hour time-interval, Scores for pulmonary edema were increa sed by fixation of the fracture, but there was no difference among the scores associated with the three methods of fixation, CLINICAL RELEVA NCE; The findings of the present study indicated that the amount of in travascular fat persisting in the lungs, kidneys, and brain twenty-fou r hours after pressurization of the intramedullary canal is not affect ed by the method of fixation of the fracture, Fixation of a fracture i s associated with minimum evidence of acute inflammation and has no ef fect on pulmonary artery pressure. The development of pulmonary dysfun ction from fat emboli depends on other factors, not just on the presen ce of fat in pulmonary vessels. It appears that the method of fracture fixation has little influence on the outcome of treatment.