Biomechanics of a new short-stemmed uncemented hip prosthesis: An in-vitro study in human bone

Abstract

The migration pattern, cyclic motion, system stiffness and failure load of a new short-stemmed hip prosthesis were compared to a clinically successful shaft prosthesis during the initial loading phase. The influence of implant-sizing on mechanical stability was also investigated for the new stem, in particular with relation to the bone quality. Prostheses were implanted in paired human femora and loaded cyclically up to 3515 cycles. Relative displacements between prosthesis and bone were measured using a 3D-camera and reflective marker system. Migration of the new stem was predominantly into varus and was higher than for the shaft prosthesis. The test set-up was proposed to simulate a worst-case loading scenario since muscle forces, which tend to reduce bone deformation, were not simulated. It could therefore be expected that clinical migration of the implants would be less pronounced than that observed in this study. Cyclic motion for the new stem was similar to that for the clinically successful shaft prosthesis, suggesting that bone ingrowth could be expected for the new stem. No significant difference in fracture load was observed between the implants. The system stiffness with the new stem was lower than for the shaft prosthesis, indicating more physiological load transfer. Smaller implant sizing with 'cancellous' fixation seems favourable, as it led to similar migration and smaller cyclic motion values than with 'cortical' fixation. A trend for higher cyclic motion and migration was observed in femora with poor bone quality. Hence, sufficiently good bone stock is necessary, when implanting the new short-stemmed prosthesis.

Periprosthetic DXA after total hip arthroplasty with short vs. ultra-short custom-made femoral stems

“…It has been reported that a proximal-loading device with extended metaphyseal geometry (lateral flare) preserves bone mass and increases periprosthetic bone stock (Leali and Fetto 2004), and that changes in the pattern of proximal loading stimulate the formation of new bone trabeculae, which stream up to the level of the lateral flare (Walker et al 1999). Radiographic studies (Leali et al 2002) and biomechanical tests (Walker et al 1999, Kim et al 2001, Westphal et al 2006b) have confirmed that this kind of proximal geometry provides effective initial and long-term stability, suggesting that stems could be made shorter than designs that do not incorporate the lateral flare feature. Following this philosophy, an original custom-made ultra-short femoral stem with extensive proximal load transfer was developed (type 1).…”

Tri-Lock Bone Preservation Stem Versus Conventional Corail Stem in Primary Total Hip Arthroplasty via Direct Anterior Approach: A Short-Term, Retrospective, Comparative Study

“…In contrast, Guo et al [3] showed that Tri-Lock BPS and Corail stems exhibited favorable outcomes in most radiological indices without significant differences at 4-year follow-up, but Tri-Lock BPS outperformed Corail stems in reducing bone loss around the stem while ensuring initial stability of the prosthesis [3]. This may be attributed to the fact that short wedge stems can differentially reduce the effective load on the distal femur to achieve a better fit with the proximal femur, providing a relatively greater load on the proximal bone and thus reducing the stress shielding of the femur [48,49]. Nonetheless, comparison analyses of radiological indices of Tri-Lock BPS vs Corail stems in DAA-THA have not been conducted.…”

Method of computational design for additive manufacturing of hip endoprosthesis based on basic‐cell concept

“…4 Such an approach provides improved outcomes for patients' treatment and rehabilitation. 5,6 Furthermore, AM enables obtaining devices with complex unstructured geometry. Such structures may have not unique mechanical properties but even novel biological features.…”

“…Additive manufacturing (AM) brings many benefits to the fabrication of high‐quality porous patient‐specific implants 4 . Such an approach provides improved outcomes for patients' treatment and rehabilitation 5,6 . Furthermore, AM enables obtaining devices with complex unstructured geometry.…”