Assessment of sagittal split ramus osteotomy rigid internal fixation techniques using a finite element method.

In this study, finite element analysis (FEA) was used to evaluate nine rigid internal fixation techniques for sagittal split ramus osteotomy. To achieve this, a computed tomography (CT) scan of a healthy patient was obtained and used to generate the geometry of a half-mandible. The geometries of bicortical screws, miniplates, and monocortical screws were designed and combined with the mandible in nine models simulating various techniques. Four models used bicortical screws in various arrangements and four used miniplates of various designs. One model represented a hybrid technique. A load of 500 N was applied to the posterior teeth and FEA was applied. The most stable techniques were the hybrid technique and a single straight miniplate, presenting the least displacement among all models. Bicortical screws, while presenting reasonable stability, showed high strain areas near the anterior ramus ridge, superoposterior to the screws, implying a risk of bone fracture in this area. On the other hand, the T-shaped and double Y-shaped miniplates were associated with high von Mises stresses that would impair their rigidity, especially where angles appeared in their designs. We recommend the use of a single straight miniplate because it provides sufficient stable fixation with minimal risks or disadvantages.

Anatomic relations between the lumbar pedicle and the adjacent neural structures.

STUDY DESIGN: The authors analyzed anatomic parameters between the lumbar pedicles and the dural sac as well as the spinal nerve roots. OBJECTIVES: To determine quantitatively the anatomic relations between the lumbar pedicle and adjacent dural sac and nerve roots. SUMMARY OF BACKGROUND DATA: Posterior transpedicular screw fixation is the most commonly used method of instrumentation for stabilization of the unstable lumbar spine. A thorough knowledge of the unique anatomy of the lumbar pedicle and adjacent neural structures may avoid or minimize neurologic complications with pedicular screw placement. METHODS: Fifteen adult cadavers were obtained to evaluate quantitatively the anatomic relations of the lumbar pedicle to the adjacent neural structures. After removal of the laminas and facets, the lumbar pedicles, dural sac, and nerve roots were exposed. Direct measurements were taken from the pedicle to the dural sac medially, to the nerve roots superiorly and inferiorly, and between the pedicles. Also, the superoinferior diameter of the nerve root and the frontal angle of the nerve root were measured. Symmetric structures were measured bilaterally. RESULTS: No consistent changes from L1 to L5 were found in all parameters. The mean distances from the lumbar pedicle to the dural sac medially and to the adjacent nerve roots superiorly and inferiorly for all levels were 1.5 mm, 5.3 mm, and 1.5 mm, respectively. The mean interpedicular distance ranged from 23.2 to 24.4 mm. The mean superoinferior diameter of the nerve root ranged from 3.8 to 4.6 mm. The mean nerve root angle ranged from 33.7 degrees to 39.2 degrees. CONCLUSIONS: On the basis of this study, improper placement of the pedicle screw medially or caudally in the lumbar spine should be avoided.

[Hydroelectrolytic requirements during the first week of life in premature infants weighing less than 1000 g. Physiopathology and recommendations]. / Besoins hydroélectrolytiques pendant la première semaine de vie chez les prématurés de moins de 1,000 g. Physiopathologie et recommandations.

Fluid and electrolyte maintenance in very low birth weight infants during the first week of life must be adapted to their physiological characteristics and to pathological events. Insensible water losses are elevated and may reach 100 mL/kg/24 h depending upon many factors, such as type of incubator, phototherapy, presence of respiratory distress syndrome, changes in transepidermal water losses and renal water and electrolyte regulation (prediuretic, diuretic and postdiuretic phases); there is also a major risk of hypernatremia and hyperkaliema. In cases of insufficient fluid intake the main complication is dehydration with hypernatremia. Excessive fluid intake results in increased incidence of bronchopulmonary dysplasia, patent ductus arteriosus and necrotizing enterocolitis. Hypernatremia is a major risk factor of intracranial hemorrhage. A careful management of water and electrolyte requirements is therefore mandatory in very low birth weight infants. Guidelines on daily maintenance and management are presented.

Open reduction and internal fixation with bone grafting of clavicular nonunion.

BACKGROUND: Although clavicular fractures are common, nonunion of the clavicle is a rare complication. However, it can be disabling, presenting mainly with pain, limitation of shoulder movement, and/or compression of the brachial plexus. The technical difficulty in securing adequate skeletal stabilization and the unique anatomic features of the clavicle pose a challenge for the orthopedic surgeon. METHODS: Sixteen patients with symptomatic nonunion of the clavicle were studied. They were nine men and seven women with a median age of 34 years (range, 15-52 years). The average follow-up was 12.9 months (range, 9-24 months). The nonunion was hypertrophic in 11 cases, atrophic in five cases, and showed pseudoarthrosis in one case. The primary indication for performing the operation was pain in all cases. Five of the 16 cases had previous operations. All cases were treated with open reduction and internal fixation using a reconstruction plate or a dynamic compression plate. Double plating was used in three cases. Autogenous bone grafting was applied in 14 cases and corraline hydroxyapatite in one case. RESULTS: Fifteen of the 16 fractures eventually healed with complete resolution of the preoperative pain, except in two cases who had persistent mild pain. The hardware was removed after union in one case. One hardware failure required revision and eventually went on to heal. Another hardware failure required removal because of pain. The pain subsided despite the persistent nonunion. The same patient had hematoma at the site of the bone graft and continued to have pain until the last follow-up. CONCLUSION: Plating and bone grafting of the clavicle is an effective method of management of painful nonunion, and it has minimal complications.

Effects of early indomethacin administration on oxygenation and surfactant requirement in low birth weight infants.

A previous study found that early intravenous indomethacin administration prolonged respiratory support in very low birth weight infants. We have, therefore, designed a randomized, double blind controlled study to evaluate the oxygenation, and surfactant requirements in preterm low birth weight infants receiving early indomethacin administration. Premature neonates who received surfactant therapy and on mechanical ventilation were prospectively randomized to receive either placebo or indomethacin (0.2 mg/kg intravenously at 12 postnatal hours and every 24 h for two more doses). Oxygenation was assessed by FiO2 required and arterial/alveolar oxygen (a/A O2) ratio during the first 48 h of life. The doses of surfactant were compared between the two groups. Twenty-seven infants (n = 14 of early indomethacin and n = 13 of placebo group) fulfilled inclusion criteria. At admission to the study, there were no differences in the birth weight, gestational age, sex, Apgar scores, a/A O2 ratio, and FiO2. The control group exhibited a significant improvement in oxygenation (FiO2 requirement and a/A O2 compared with the early indomethacin group at 24 (P = 0.026 and 0.02, respectively) and 48 h of life (P = 0.037 and 0.026, respectively). The requirement of surfactant was significantly larger in the early indomethacin group (P = 0.029). Early indomethacin administration increases oxygen and surfactant requirement.