• Birgit Zirngibl, Roland Biber, and Hermann Josef Bail.
• Department of Trauma and Orthopaedic Surgery, Klinikum Nuernberg, Breslauer Str. 201, 90471 Nuernberg, Germany. birgit.zirngibl@klinikum-nuernberg.de
• Int Orthop. 2013 Jul 1; 37 (7): 1363-8.

PurposeHip perforation is a major complication in proximal femoral nailing. For biaxial nails, knowledge of their biomechanics is limited. Besides re-evaluation of accepted risk factors like the tip-apex distance (TAD), we analysed the influence of anti-rotational pin length.MethodsWe compared 22 hip perforation cases to 50 randomly chosen controls. TAD, lag-screw position, angle between lag-screw and femoral neck axis, lag-screw gliding capacity, displacement and anti-rotational pin length were investigated.ResultsHip perforation was associated with a higher angle of deviation between lag-screw and femoral neck axis (p = 0.001), a lower telescoping capacity of the lag screw (p = 0.02), and higher TAD (p = 0.048). If the anti-rotational pin exceeded a line connecting the tip of the nail and the lag screw (NS line), hip perforation incidence was increased (p = 0.009). Inadequate pin length resulted in an odds ratio of 10.8 for hip perforation (p = 0.001).ConclusionsIn biaxial nails anti-rotational element positioning is underestimated, however, crucial.

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