title: Changes in strain patterns after implantation of a short stem with metaphyseal anchorage compared to a standard stem: an experimental study in synthetic bone.
abstract: Short stem hip arthroplasties with predominantly metaphyseal fixation, such as the METHA® stem (Aesculap, Tuttlingen, Germany), are recommended because they are presumed to allow a more physiologic load transfer and thus a reduction of stress-shielding. However, the hypothesized metaphyseal anchorage associated with the aforementioned benefits still needs to be verified. Therefore, the METHA short stem and the Bicontact® standard stem (Aesculap, Tuttlingen, Germany) were tested biomechanically in synthetic femora while strain gauges monitored their corresponding strain patterns. For the METHA stem, the strains in all tested locations including the region of the calcar (87% of the non-implanted femur) were similar to conditions of synthetic bone without implanted stem. The Bicontact stem showed approximately the level of strain of the non-implanted femur on the lateral and medial aspect in the proximal diaphysis of the femur. On the anterior and posterior aspect of the proximal metaphysis the strains reached averages of 78% and 87% of the non-implanted femur, respectively. This study revealed primary metaphyseal anchorage of the METHA short stem, as opposed to a metaphyseal-diaphyseal anchorage of the Bicontact stem.
authors.affiliation: Department of Orthopedic Surgery, Hannover Medical School , Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Gronewold
authors.affiliation: Biomechanics and Biomaterials Laboratory, Hannover Medical School , Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Berner
authors.affiliation: Biomechanics and Biomaterials Laboratory, Hannover Medical School , Germany.
authors.forename: Gavin
authors.initials: G
authors.lastname: Olender
authors.affiliation: Biomechanics and Biomaterials Laboratory, Hannover Medical School , Germany.
authors.forename: Christof
authors.initials: C
authors.lastname: Hurschler
authors.affiliation: Department of Orthopedic Surgery, Hannover Medical School , Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Windhagen
authors.affiliation: Department of Orthopedic Surgery, Hannover Medical School , Germany.
authors.forename: Gabriela
authors.initials: G
authors.lastname: von Lewinski
authors.affiliation: Department of Orthopedic Surgery, Hannover Medical School , Germany.
authors.forename: Thilo
authors.initials: T
authors.lastname: Floerkemeier
keywords: biomechanical testing; short stem hip arthroplasty; standard stem hip arthroplasty; strain gauges; strain patterns
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