Feasibility of iliosacral screw placement in patients with upper sacral dysplasia
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(2019) 14:418
RESEARCH ARTICLE
Open Access
Feasibility of iliosacral screw placement in patients with upper sacral dysplasia Christoph J. Laux1*† , Lizzy Weigelt2†, Georg Osterhoff1,3, Ksenija Slankamenac4 and Clément M. L. Werner1
Abstract Background: Exact knowledge of the sacral anatomy is crucial for the percutaneous insertion of iliosacral screws. However, dysplastic anatomical patterns are common. In addition to a preoperative computed tomography (CT) analysis, conventional radiographic measures may help to identify upper sacral dysplasia and to avoid damage to surrounding structures. Aiming to further increase safety in percutaneous iliosacral screw placement in the presence of sacral dysmorphism, this study examined the prevalence of previously established radiographic signs and, in addition, defined the “critical SI angle” as a new radiographic criterion. Methods: Pelvic CT scans of 98 consecutive trauma patients were analysed. Next to assessment of established signs indicating upper sacral dysplasia, the critical sacroiliac (SI) angle was defined in standardized pelvic outlet views. Results: The critical SI angle significantly correlates with the presence of mammillary bodies and an intraarticular vacuum phenomenon. With a cut-off value of − 14.2°, the critical SI angle detects the feasibility of a safe iliosacral screw insertion in pelvic outlet views with a sensitivity of 85.9% and a specificity of 85.7%. Conclusions: The critical SI angle can support the decision-making when planning iliosacral screw fixation. The clinical value of the established signs of upper sacral dysplasia remains uncertain. Keywords: Iliosacral screw placement, Pelvic ring injury, Upper sacral dysplasia, Sacral dysmorphism, Radiographic signs, Safety
Introduction Exact knowledge of the sacral anatomy is crucial for the percutaneous insertion of iliosacral screws for fixation of posterior pelvic ring injuries. Despite its widespread use, this technique remains demanding. Due to the long screw trajectory and the proximity of neurovascular structures, even deviations of only a few degrees bear the risk of a cortical breach and neurovascular complications. This is true especially in patients with a dysmorphic upper sacral anatomy [1]. The lumbosacral nerve roots are the structures most at risk [1–3]. Miller and Routt identified radiographic signs indicating upper sacral dysmorphism on pelvic outlet and lateral plain films (collinearity, mammillary processes, noncircular and misshapen anterior first sacral neuroforamina, residual disc space S1/S2) [4]. However, their reliability
and clinical value for preoperative planning of iliosacral screw fixation remains unknown. To achieve adequate and safe fixation in dysplastic upper sacral segments, iliosacral screw insertion into the S2 segment was recommended [5–8]. As such dysplastic patterns are very common [9–11], preoperative computed tomography (CT) analysis is regarded to be mandatory in order to identify them and to consequently avoid damage to surrounding structures [6]. Aimi
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