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Range of Motion in a Modular Femoral Stem System with a Variety of Neck Options.

J Arthroplasty. 2013 Jul 23;

Authors: Hariri S, Chun S, Cowan JB, Bragdon C, Malchau H, Rubash HE

Modular femoral stem systems decouple leg length, offset, and version. The hip ROM and type of impingement for 162 femoral head/neck combinations were measured at four extreme hip positions in a Sawbones pelvis and femur to identify constructs that lead to early impingement. Hip ROM increased in all positions with increasing head size and neck length. We identified a new type of impingement created by the build-up of the proximal femoral stem: femoral stem on acetabular liner impingement. Seventy percent of neutral neck options achieved our definition of acceptable ROM. In general, when utilizing a modular femoral stem, surgeons can minimize impingement by choosing the longest femoral neck that does not over-lengthen the limb, using the largest femoral head accommodated by the cup, and avoiding neck version unless the cup or stem is malaligned.

PMID: 23886407 [PubMed - as supplied by publisher]