Open AccessPrimary stability in total hip replacement
Author(s) -
Paul Schmitz,
Boyko Gueorguiev,
Ivan Zderic,
Christian Pfeifer,
Michael Nerlich,
Stephan Grechenig
Publication year - 2017
Publication title -
medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.59
H-Index - 148
eISSN - 1536-5964
pISSN - 0025-7974
DOI - 10.1097/md.0000000000008278
Subject(s) - medicine , cadaveric spasm , prosthesis , stiffness , biomechanics , initial stability , orthodontics , femur , total hip replacement , surgery , dentistry , implant , anatomy , structural engineering , engineering
Background: In total hip replacement (THR), it is essential to achieve a primary stability to guarantee good long-term results. A novel locking screw hip (LSH)-stem, anchored to the medial cortex of the proximal femur by 5 monocortical locking screws, was developed to overcome the shortcomings of uncemented press-fit and cemented straight stems while simultaneously achieving primary stability. The aim of this study was to investigate the biomechanical competence of the LSH-stem in comparison to an uncemented press-fit stem. Methods: Six pairs of embalmed human cadaveric femora from donors aged 68 to 84 years were assigned to 2 study groups (n = 6) with equal number of right and left bones. The specimens in each group and pair were implanted with either an uncemented press-fit stem or an LSH-stem and tested biomechanically under progressively increasing cyclic axial loading until catastrophic failure. Axial construct stiffness, failure load, and cycles to failure were detected and statistically evaluated at a level of significance P = .05. Results: Although the axial stiffness was comparable for both prosthesis types, the uncemented press-fit stem showed a significant lower stability in terms of failure load and cycles to failure in comparison to the LSH-stem, P = .04. Conclusion: Converting our results to percentage of bodyweight (BW) in an assumed adult patient of 80 kg shows that the LSH-stem achieves a primary stability allowing to carry average loads of up to 507% BW, whereas the uncemented press-fit stem carried average loads of up to 404% BW. We conclude that both stems achieve a primary stability strong enough to carry hip joint loads experienced in the immediate rehabilitation period after THR.