Une longueur excessive des vis inter-fragmentaires de fixation de la paroi postérieure de l’acetabulum permet de prédire une pénétration intra-articulaire

Abstract

BackgroundThe fixation of posterior wall acetabular fractures often utilizes interfragmentary screws with varying length. Intricate pelvic anatomy and overhanging greater trochanter make obtaining proper screw trajectory difficult. A large measurement may represent aberrant trajectory and breach of the articular surface. This study aims to identify a preferred maximum screw length that avoids intraarticular penetration. HypothesisWe hypothesized that a screw measured 40mm or longer has a high likelihood of being intra-articular. Patients and MethodsA retrospective review included CT scans of 151 consecutive patients collected at a level-1 trauma center was analyzed by two observers. On axial imaging, a straight line was measured at the largest extraarticular portion of the posterior wall simulating ideal screw placement. Another line was measured tangent to the articular surface simulating longest possible extraarticular screw. Measurements were taken at 2-millimeter increments. ResultsThe intra-class correlation coefficient between both observers was excellent (0.75–1.00) for most recorded values. The maximum mean length for straight line measured (m=32.18mm, SD=3.74) which was smaller than the mean length for tangent line (m=38.44, SD=4.29). Exploratory multivariate logistic regression analyses demonstrated increased height, age, and acetabular version were associated with larger measurements greater than 40mm (p<0.05). DiscussionThis study demonstrates that most acetabular posterior walls cannot accommodate a 40mm lag screw. If the measured drill hole is greater than this length, then careful reconsideration of the screw trajectory is warranted to ensure the screw is not intraarticular. Older and taller patients may be able to accommodate longer screws. Level of EvidenceIII.