ABSTRACT
Modifications of a Type 1a external skeletal fixator (ESF) frame were evaluated by alternately placing transfixation pins on opposite sides of the connecting rod (Type 1a-MOD) or by placing additional connecting rods on either of the two inside (Type 1a-INSIDE) or two outside (Type 1a-OUTSIDE) transfixation pins. The objective of this study was to evaluate the stiffness of these modifications in terms of axial compression (AC), cranial-caudal bending (CCB), and medial-lateral bending (MLB). We hypothesized that these designs would allow significant increase in unilateral frame stiffness, over Type 1a, without proportional increase in frame complexity or technical difficulty of application. All of the ESF frames were constructed using large IMEX SKtrade mark clamps, 3.2 mm threaded fixation pins, 9.5 mm carbon fibre connecting rods and Delrin rods as bone models. Nine, eight pin frames of each design were constructed, and subjected to repetitive non-destructive loading forces (AC, CCB, MLB) using a materials testing machine. Frame construct stiffness for each force (AC, CCB, MLB) was derived from load-deformation curve analysis and displayed in N/mm. Data revealed the 1a-MOD and 1a-OUTSIDE constructs had significantly increased stiffness in CCB and AC as compared to the Type 1a constructs while all of the modified constructs were significantly stiffer in MLB than the Type 1a constructs.
Subject(s)
External Fixators/veterinary , Fractures, Bone/veterinary , Animals , Biomechanical Phenomena , Equipment Design , Fractures, Bone/surgery , Materials Testing , Radius Fractures/surgery , Radius Fractures/veterinary , Tibial Fractures/surgery , Tibial Fractures/veterinaryABSTRACT
A variety of hypotheses have been proposed to explain the premenstrual syndromes. These hypotheses serve as rationales for an equally diverse range of proposed treatments. To investigate these hypotheses, we obtained multiple blood samples across the menstrual cycle in women with well-characterized menstrually related mood disorder and in control subjects. No diagnosis-related differences were observed in the levels or patterns of secretion of progesterone, estradiol, follicle-stimulating hormone, luteinizing hormone, testosterone-estradiol-binding globulin, dehydroepiandrosterone sulfate, dihydrotestosterone, prolactin, or cortisol. Our data suggest that premenstrual syndrome does not represent a simple hormonal deficiency and that the cited rationales for several of the proposed treatments are of questionable merit.
