title: Shortening of an anatomical stem, how short is short enough? An in vitro study of load transfer and primary stability.
abstract: An anatomical stem should be short enough to avoid distal locking and distal load transfer but long enough to ensure adequate primary stability of the stem. In this in vitro study, the cortical strains in the femur and the primary stability of the stem were measured after insertion of Anatomic Benoist Girard-I anatomical stems with gradually reduced stem length in six human cadaver femurs in order to find the optimal stem length. A shortening of 40-50 mm, corresponding to a stem extending 30-40 mm below the lesser trochanter, did not affect stem stability but nearly normalized the load distribution in the lower metaphysis and upper diaphysis. The large strain shielding observed in the calcar region was not influenced by shortening of the stem.
authors: Department of Orthopaedic Surgery, Trondheim University Hospital, Trondheim, Norway. Per-Olav.Ostbyhaug@stolav.no
authors: Per Olav
authors: PO
authors: Østbyhaug
authors: Jomar
authors: J
authors: Klaksvik
authors: Pål
authors: P
authors: Romundstad
authors: Arild
authors: A
authors: Aamodt
mesh_terms: D002102:Cadaver; D019245:Compressive Strength / Q000502:physiology; D055119:Elastic Modulus / Q000502:physiology; D019544:Equipment Failure Analysis; D005260:Female; D005270:Femur Head / Q000502:physiology* / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009038:Motion; D011474:Prosthesis Design; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*
keywords: Hip prosthesis; femoral stem; micromotion; primary stability; stem design; stem length; strain; stress shielding