Abstract
To identify ideal screw placement for internal fixation of intra capsular fracture neck of femur to avoid fixation failures, 20 cadaveric bone measurements of the neck of femur in basal, midcervical and at sub capital regions were carried out using Vernial caliper and CT scan. Midcervical region of neck of femur measurements were further divided into upper half (Superior half) and Inferior half (Inferior Half).
AP and Lateral view X-rays were obtained following three parallel screws placements in Femur neck:
Configuration 1: Triangular configuration where two screws are inferior and one superior.
Configuration 2: Triangular configuration where two screws are placed superiorly and one screw inferiorly.
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Neck has wider diameter in the upper half of neck of femur than in the lower half in the mid cervical region.
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Placing two 7.0 mm cancellous screws (total 14 mm) in the lower half of the neck of femur, as widely practised, has more likely chances of not having purchase in the mid cervical region of the femur neck by at least one screw.
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Cannulated screws fixation carried out in reverse triangular configuration by placing two screws superiorly (superior-anterior and superior-posterior) and one screw inferiorly (inferior-central) has better fixation and avoids fixation failure.
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Reverse triangular configuration of fixation is also likely to support the weaker superior half of the neck which lacks stronger cortex and calcar part as in the inferior part of the neck
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We also recommend placing a larger screw in the superior half of femur neck and a smaller screw in the inferior half in recon-–IM nail fixation, based upon our experiment result.
