By A. Larson. Jewish Theological Seminary. 2018.
Because the operating range is from 10 to 40% cheap minocin 50mg amex, it is extremely important to anchor the HEST with 20% strain onto the ligament in its rest position generic minocin 50 mg on line. Otherwise buy 50 mg minocin visa, one runs the risk of measuring in a nonlinear range with a linear calibration curve discount 50 mg minocin. There are two methods of anchoring an HEST to a ligament: suturing, or piercing the ligament with barbs. Both methods anchor the device by piercing the ligament substance. Buckle Transducer The buckle transducer works by slightly deflecting the normal configuration of a load-carrying flexible element in three-point bending due to interaction with the ligament. Tension in the ligament fibers causes the ligament to straighten, thereby bending the crossbar and frame of the regular buckle transducer and bending the buckle beam of the modified buckle transducer. The offset angle can be used to calculate the section modulus of the beam, where the maximum strain is set at the beam’s midsection. For this calculation, the transducer is modeled as a simply supported beam in bending, affected by an applied load P, as shown in the top portion of Fig. The tensile force can be determined from the product of the section modulus and the strain gage output. The dc is the center of deflection of the transducer, and Lc is the width of the clip. Photograph of a Hall effect strain transducer (HEST). Ligament strain and resulting force for two different ligaments with and without the buckle transducer indicating the pre-stress effect of the transducer itself. During installation, it is important to keep in mind that if too much tissue is inserted, excessive ligament shortening occurs. If not enough ligament tissue is inserted, the signal-to-noise ratio will be too small. This is done by clamping forceps on the ligament, only a few millimeters from the buckle frame, and then looping a string through the forceps. The other end of the string is attached to a calibrated spring scale. This drift in response is due to the morphological changes of the tissue; moreover, the cross-sectional area changes when the tissue is loaded infrequently, resulting in poor repeatability. The mere act of attaching the buckle transducer onto a ligament causes changes in its length. Once the buckle is locked in place, the resting length of the tissue is shortened because of the path it must take. The presence of the buckle transducer changes the local stresses and boundary conditions at the site to which it is attached. The main advantage of the buckle transducer is that it measures bulk ligament force directly. Roentgenstereophotogrammetric Analysis Stereophotogrammetry is the use of multiple two-dimensional pictures of three-dimensional objects to reassemble a three-dimensional image. Roentgenste- reophotogrammetry analysis (RSA) is a three-dimensional radiographic technique used to study joint motion pathways. W hile rigid body joint motion is the primary focus of this technique, it can also be © 2001 by CRC Press LLC FIGURE 7. The relationship of the time required for a ligament with a buckle transducer attached to regain its pre-conditioned state based on the time elapsed from pre-conditioning. Ligament strain and resulting forces for two different ligaments with and without the buckle transducer indicating the pre-stress effect of the transducer. Tantalum pellets are used as X-ray markers because of their excellent radiopaque characteristics and biocompatability.
The collagen fibrillar organization is clearly depicted buy 50 mg minocin otc. The disruption of the lamellar structure and properties at the tip of the lunate-shaped defect is observed discount minocin 50mg with visa. Macrotextured titanium hip implant surfaces have been investigated and include sintered com- mercially pure titanium (CPTi) beads buy generic minocin 50 mg, diffusion bonded titanium fiber metal pads minocin 50 mg low price, and plasma-sprayed CPTi coatings. The purpose of these porous-coated or roughened implant surfaces is to achieve an interlock with the surrounding bone, i. To manufacture sintered CPTi beads, layers of spherical CPTi beads are positioned on the femoral component with a binding substance. The femoral component with the applied binding substance–bead mixture is then subjected to the sintering process. Sintering is a high temperature process that dissipates © 2001 by CRC Press LLC the binding substance and fuses the beads to each other and to the femoral component. The high temperatures that the femoral component substrate is exposed to can significantly decrease the fatigue strength of the implant system. The porosity is controlled by the sizes of the spherical beads. Fiber metal pads are produced from wire that has been cut, kinked, and formed in a mold to a specific pattern and shape. The titanium fiber metal pads are positioned into recesses in the femoral component substrate and subjected to the diffusion bonding process. The diffusion bonding process employs the use of heat (lower temperatures than sintering) and pressure application to bond the fiber metal wires to the femoral component substrate. For the plasma-sprayed CPTi coating, the coating material is heated within a spray nozzle. The coating powder (CPTi) and a pressurized gas mixture are then injected into a high-energy arc created within the nozzle and the molten powder is propelled against the implant surface. The application of a plasma spray coating on titanium alloys also diminishes the fatigue performance of the implant due to the increase in sites for crack initiation and propagation. The characteristics of the plasma sprayed coating are controlled through variations in particle size of the CPTi powder and the pressure applied. In an attempt to improve the fixation of bone to implants, a key research focus has been the develop- ment of surfaces that encourage biological fixation. Bioactive ceramic coatings applied to the surfaces of metallic implants have been intensely investigated. Improved implant stability is achieved through this biochemical bond. HA has been shown to enhance the interfacial shear strength and bone contact in animal models when plasma sprayed on a titanium alloy (Ti + 6Al + 4V) implant. A macrotextured surface with a bioactive coating would have the advantages of enhanced early bone formation and the elimination of fibrous tissue formation, resulting in a strong mechanical fixation with the bone. The purpose of this study was to investigate arc deposition of CPTi, a new implant surface macrotex- turing technique, with AD/HA and a plasma-sprayed HA coating without arc deposition (AD). Multiple analysis techniques were utilized including acoustic microscopy, mechanical testing, qualitative histology, quantitative histomorphometry, and scanning electron microscopy. Ten purpose-bred coonhounds received staged bilateral hemiarthroplasties in the proximal femurs using the unique Harrington canine femoral component model (HARCMOD HIP). One femur received an uncoated Ti + 6Al + 4V alloy femoral stem with an arc-deposited commercially pure titanium (CPTi) surface. The arc deposition process was achieved by striking an electric arc between two pure titanium wires. A high pressure carrier gas passed through the arc and atomized the melt. This resulted in a spray directed at the alloy substrate.
Intubate the patient generic 50 mg minocin otc, administer hyperventilation to a PCO2 of 25 to 35 mm Hg buy 50 mg minocin with amex, and ask for emergent neurosurgery consult for evacuation of the hematoma C cheap 50mg minocin fast delivery. Intubate the patient minocin 50mg without prescription, administer hyperventilation to a PCO2 of 25 to 35 mm Hg, admit to ICU for close observation, and consult neurosurgery for intraventricular ICP monitoring D. Admit to ICU for further evaluation and start mannitol and steroids Key Concept/Objective: To understand the treatment of severe head injury In patients with severe brain injury, the first priority should be cardiopulmonary resusci- tation. Comatose patients with TBI are often hypoxic or hypercapnic, even though venti- lation may appear to be normal. Patients who are in a coma (GCS score of less than 8) should undergo gentle hyperventilation via intubation until a PCO2 of about 35 mm Hg is achieved. Short-term hyperventilation to levels of about 25 mm Hg can be lifesaving in the patient with impending herniation. Subdural and epidural hematomas should be evacu- ated promptly when associated with a significant mass effect, because it has been shown that there is a significant poorer outcome with surgical delays of greater than 4 hours. The literature supports a standard recommendation that corticosteroids should not be used for neuroprotection or control of ICP in patients with severe TBI. A 22-year-old man is transferred to your hospital from a local hospital, where he presented 3 hours ago with closed head trauma. At the first hospital where he was taken, he was given pain medications, and a CT scan was performed; the CT scan was negative. The patient is awake and complains only of moderate headache. The fam- ily is concerned about the development of seizures in the future, because they had a relative who had that problem. What would you recommend regarding prophylaxis for seizures in this patient? Phenytoin for 1 to 2 weeks B Carbamazepine for 6 months C. Obtain an electroencephalogram; if it is abnormal, start phenytoin D. Do not start any antiseizure medication at this time Key Concept/Objective: To understand the evaluation of the risk of posttraumatic epilepsy The risk of epilepsy in patients with closed-head injury is relatively small: 2% to 5% in all patients and about 10% to 20% in patients with severe closed-head injury. A higher inci- dence of seizures has been seen in patients with depressed skull fractures (15%), hematomas (31%), and penetrating brain wounds (50%). This patient has a mild, closed injury, and he is at very low risk for developing seizures. Because most patients who devel- op posttraumatic epilepsy in the first week after injury will have recurrent seizures for some time, anticonvulsant therapy is indicated in documented cases. Controlled, ran- domized studies have shown that the use of phenytoin, phenobarbital, carbamazepine, and valproate do not prevent the development of posttraumatic epilepsy beyond the first week after injury. It is recommended as a standard of care that these medications should not be used to prevent posttraumatic epilepsy in patients who have not had a seizure. A 44-year-old woman presents to your clinic complaining of persistent problems since being in a car acci- dent 2 years ago. At the time of the accident she suffered moderate head trauma, which required admis- sion to a hospital for 3 days. Since then, she has felt as if she is not the same person. She has had prob- 16 BOARD REVIEW lems with her husband, and she feels sad all the time. She also has lost interest in social activities, and she has lost 12 lb. What is the most likely diagnosis, and how would you treat this patient’s symptoms? The patient probably has a personality disorder; she should not have sequelae from accidents of this nature; refer for psychotherapy B. The patient probably has an undisclosed substance abuse problem; refer to psychiatry C. The patient probably has neuropsychiatric sequelae from the accident; educate her about the possible sequelae, and start a selective serotonin reuptake inhibitor (SSRI) for depression D.