Effects of stem design and material properties on stresses in hip endoprostheses

The influence of cement mantle thickness and stem geometry on fatigue damage in two different cemented hip femoral prostheses

“…Failure can occur in the short term (Hertzler et al, 2002) and can be related to the geometry of the stem and skill of the surgeon. Other factors are type of cement, surface finish and cement mantle thickness and these have been correlated with long-term failure (Fisher et al, 1997;Graham et al, 2000;Herberts and Malchau, 2007;Lewis, 1997;Rohlmann et al, 2000;Stauffer, 1982).…”

The Effect of Distal Ulnar Implant Stem Material and Length on Bone Strains

“…In the current study, it was found that stresses in the distal region were lowered with increasing stem length; however, this effect seemed to level off for stem lengths greater than 4.5 cm. Rohlmann et al 10 showed that the effect of femoral stem length had only a minor effect on the stress on the implant, cement, and surrounding bone, but saw significant increases with extremely short stem lengths. This trend was not observed for the distal ulnar stem lengths that were tested in this study, as smooth transitions and trends were observed between stem lengths.…”

“…However, optimal design parameters for distal ulnar replacements, such as the length and material of the stem, are currently unknown. In general, the preferable stress distribution after implantation should be as close to the intact bone as possible 8,10 and should be without high concentrations of stress. 10 One design parameter that has been hypothesized to contribute to early failure is stem length, 11 and some studies have investigated the effect of femoral component stem length on load transfer in the proximal femur.…”

“…8,10 -12 The material of the stem may also affect load transfer as shown in several studies related to hip implants. 10,[13][14][15][16] To the authors' knowledge, no studies have investigated the effect of length or material of distal ulnar stems on the surrounding bone strains. Currently available designs employ stems that range between 3 to 7 cm in length and are made from either titanium (elastic modulus [E] ϭ 100 GPa) or cobalt chrome (E ϭ 200 GPa).…”

Bone stresses before and after insertion of two commercially available distal ulnar implants using finite element analysis

“…11 Ideally, the stress distribution post-implantation should be close to that of the intact bone. 10,12 The extent to which the differences between the currently available designs affect the success of the implant is unclear because clinical data are currently scarce. 13 Some preliminary results from follow-up studies that examined patients approximately 6 months after surgery reported radiographic bone resorption in the region 2-3 mm proximal to the ulnar head for the cobalt chrome stemmed SBI implant 7 and 1-2 mm for the titanium stemmed Herbert implant.…”