Evaluation of a Femoral Stem With Reduced Stiffness

Long-term study of bone remodelling after femoral stem: A comparison between dexa and finite element simulation

“…The pattern of remodelling produced by this anatomic cementless stem was similar to those shown by other second-generation cemented stems, with a decrease of bone mass ranged between 20% and 25% in proximal areas, 5% and 15% in intermediate areas and with no significant loss in distal areas (Tonino et al, 2000;Gibbons et al, 2001;Ka¨rrholm et al, 2002). It was also shown in these studies that the changes remained stable after the first or second year of the operation.…”

“…This performance is quite similar to that produced by other second-generation cementless stems (Ka¨rrholm et al, 2002;Rahmy et al, 2004) and prove that this design fail to completely avoid stress-shielding both in clinical and FE studies (Rietbergen and Huiskes, 2001). Although the changes of BMD after a hip replacement are caused by mechanical and biological factors, most of the changes that occur immediately after the surgery are considered to have a mechanical origin.…”

“…In the femur with prosthesis the loads are fundamentally transmitted from the prosthetic head to its stem, producing the stress-shielding and loading the femur in the zones corresponding to the HA end, producing bottleneck effect. These changes explain that with first generation cemented stems the losses in density reached up to 45% (Sychter and Engh, 1996;McAuley et al, 2000;Sychter et al, 2002), with second generation stems still reaching between 20% and 25% at the end of the first or second year (Ka¨rrholm et al, 2002) and with tapered stems decreases between 10% and 30% were found with proximal predominance (Gibbons et al, 2001;Schmidt et al, 2004). Custom made implants had decreases in proximal areas of 10-15% at the end of the first year (Zerahn et al, 1998;Martini et al, 2000); femoral stems with reduced stiffness showed 15% reduction in the calcar at the end of the second year (Ka¨rrholm et al, 2002;Nagi et al, 2006).…”

Periprosthetic proximal bone loss after uncemented hip arthroplasty is related to stem size: DXA measurements in 138 patients followed for 2–7 years

“…Earlier isoelastic stems have suffered from early loosening and a high revision rate (Nistor et al 1991, Jacobsson et al 1993, Niinimäki et al 1994). However, Glassman et al (2001) and Kärrholm et al (2002) presented good results with the Epoch isoelastic stem. DXA is an accurate and reproducible method for measurement of bone remodeling (Kalender 1992).…”

“…However, Korovessis et al (1997) did not find any correlation between age and BMD changes; only body mass index correlated with BMD in zone 3 in their study. Kärrholm et al (2002) evaluated possible confounding factors (sex, age, weight, diagnosis, BMD and stem size) immediately after the operation, and found that periprosthetic BMD was influenced only by stem design. Kiratli et al (1996) reported that weight was the only variable that affected bone remodeling.…”