Measurement of the Micromotion and Migration of an Un-cemented Stem in an In-vitro Test

J.P. Clements, S. Gheduzzi, J. Heal, I.D. Learmonth, and A.W. Miles (UK)


Orthopaedics, Hips and femurs, Total hip replacement,postoperative stability, micromotion,


Objective. This study investigates the postoperative stability of the cement-less IPS hip stem (De Puy) by means of measuring the relative motion of the implant with the host bone. Background. Primary stability of a cement-less hip stem is considered as one of the key factors for promoting good oesteoingeration helping to achieve long-term clinical success. The motion of the implant relative to the bone is catagorised into two modes, micromotion and migration. Method. Six IPS hip stems were implanted into six composite femora. A six degrees of freedom displacement transducer was attached to the implant and composite femur to record the motion under two loading regimes, single leg stance and stair climbing. Results. The motions measured were very small in all three orthogonal directions. The displacement transducer did not record any significant migration as motions detected were within the error range. Conclusion. The IPS hip stem is extremely stable and shows that the design philosophy of this stem is effective producing excellent postoperative stability.

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