Comparison of Modified Transiliac Internal Fixators: Mechanical Testing on Pelvic Models.

PURPOSE OF THE STUDY Vertically unstable transforaminal sacral fractures can be stabilized with several types of transiliac internal fixators (TIFI): the classical one (TIFI-C), the supraacetabular one (TIFI-A) and by dual application of TIFI (DTIFI). MATERIAL AND METHODS Pelvic models made of solid foam (Sawbones 1301) were used in the study. Mechanical loading tests were performed in order to assess the stiffness of the studied pelvic structures. The stiffness of the intact model was approximated as the slope of load/displacement curve. Then vertically unstable right-sided linear transforaminal fracture was created and subsequently fixed by TIFI-C, TIFI-A and DTIFI (each fixator for a separate model). The fixation techniques were compared based on the ratio between the stiffness of the treated and of the intact pelvis. Motion of the posterior pelvic structures and their deformations were measured using a photogrammetric system with four synchronous cameras. Loads applied at the base of sacrum and sacral base displacements were recorded by the testing device and used to assess the stiffness of the model structure. A dedicated load cell and a monoaxial extensometer were utilised. Every measurement was repeated at least 10 times. Obtained data were analysed by one way ANOVA test with post hoc comparison by Tukey HSD test. RESULTS Mean stiffness ratio (±1SD) of pelvic structure was 0.638 ± 0.005 for TIFI-C, 0.722 ± 0.014 for TIFI-A and 0.720 ± 0.008 for DTIFI. Dual transiliac internal fixation and supraacetabular fixation were superior to the classical one (p < 0.0001), but DTIFI and TIFI-A stiffness ratios were statistically equivalent (p = 0.9112). CONCLUSIONS Results of the mechanical analysis using pelvic models indicate that for linear vertical transforaminal sacral fracture without comminuted zone, an application of either TIFI-A or DTIFI provides significantly higher stiffness of the lateral pelvic segment than application of TIFI-C. Key words: transforaminal sacral fracture, transiliac internal fixator, dual TIFI, stability, biomechanics, digital image correlation.

[Mediolateral episiotomy and anal sphincter trauma]. / Mediolaterální epiziotomie a poranení análního sfinkteru.

OBJECTIVE: A summary of recent knowledge of the correlation between mediolateral episiotomy and anal sphincter injury. DESIGN: Review. SETTING: Department of Gynaecology and Obstetrics, Charles University and University Hospital Pilsen. CONCLUSIONS: The methodology of most studies is not well managed. Four problematical points were identified: definition of the mediolateral episiotomy, practical execution of the mediolateral episiotomy, diagnostics of perineal trauma and classification of the perineal trauma. Mediolateral episiotomy is often deficiently defined. Definitions differ depending on individual textbooks or departments. The majority of studies gives no definition and no description of the practical execution of an episiotomy or describes it inadequately. To the current knowledge there is no international consensual definition, which is used universally. Until 2003, there was no study evaluating adequate implementation of the mediolateral episiotomy. It appears that most of executed mediolateral episiotomies are not truly mediolateral. The angle of inclination between 40-60 degrees was suggested. According to the latest study, the lower limit of the mediolateral episiotomy definition (40 degrees) appears to be insufficient. At the present time, the correlation between mediolateral episiotomy and perineal trauma cannot be precisely evaluated. Before analyzing the benefits and risks of mediolateral episiotomy, an international consensus must be found, that would establish an exact definition of mediolateral episiotomy.