Brain tumors in children. I. Advances in diagnosis

This article emphasizes the contributions that new diagnostic techniques have made toward the management of children with brain tumors. The development of computerized tomographic (CT) scanning has revolutionized both the diagnosis and management of patients with brain tumors and has obviated the previously inevitable delays in diagnosis. The development of magnetic resonance imaging (MRI) has certainly facilitated diagnosis of brain tumors in certain locations with the brain, but it remains unproven in other locations. It is clear that at least some of the early promise of MRI scanning has not been realized. Neither CT nor MRI are able to provide functional detail within the brain, nor are they able to differentiate tumor from peritumoral edema to better delineate the tumor margins. It is hoped that the currently experimental techniques of Positron Emission Tomography (PET) scanning and contrast-enhanced MRI scanning will provide such information in the near future. Neurophysiologic methods of assessing brain tumors merit greater consideration than has been afforded to date. Sensory evoked-potential monitoring provides information about nervous system function. This information is useful both in diagnosis and in monitoring of brain tumors, since the functional information can be localized to discrete regions within the brain. The value of cerebrospinal fluid (CSF) evaluation, both for cytology and tumor markers, cannot be overstated. A significant proportion of childhood brain tumors tend to seed throughout the neuraxis by the CSF pathways. Thus, evaluation of CSF cytology prior to surgical perturbation of the primary tumor should be undertaken whenever safely feasible, in order to avoid the dilemma of postoperative positive CSF cytology and its questionable significance.     

FM sonography in diffuse liver disease: prospective assessment and blinded analysis

FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.     

In-vivo comparison of four absorbable sutures: Vicryl, Dexon Plus, Maxon and PDS

Absorbable sutures are initially equal or superior to nonabsorbable sutures in terms of tensile strength but are absorbed at variable rates by the action of hydrolysis. This study demonstrated that the in-vivo half-life tensile strength of the braided absorbable sutures polyglycolic acid (Dexon Plus) and polyglactin 910 (Vicryl) is 2 weeks, whereas those of the monofilament absorbable sutures polyglyconate (Maxon) and polydioxanone (PDS) are 3 and 6 weeks respectively. The addition of a single hitch or six knots reduced the in-vitro tensile strength by 30% to 35%. Polyglyconate (Maxon) suture demonstrated the best in-vitro knot security.     

Stability of the original Hoffmann and AO tubular external fixation devices

Detailed data of the stability of external fixation devices are needed by the orthopaedic surgeon to predict successful healing of a fracture. The stability (rigidity, yield and failure criteria) of four half-frame configurations (single, stacked, double and delta) of the original Hoffmann and AO tubular frame have been analysed under four loading conditions: axial compression, torsion, and both AP- and ML-bending. Overall the two systems' rigidities were the same between similar configurations. Both systems' single half-frames were particularly weak; however, as the number of components (rods, pins, clamps, couplings) on the frame increased, the rigidity of the frame increased. The difference in performance between the two systems lies in their yield and failure characteristics. The AO system exhibited excellent failure criteria in all modes of loading, i.e. no configuration failed within the test limits, whereas most Hoffman frames yielded and failed at low loads.