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.

Quality of Live of Patients in the Evaluation of Outcomes of Short Stem Hip Arthroplasty for Hip Osteoarthritis

“…Nie za ob ser wo wa no infek cji głę bo kich. Po dob ne wy ni ki le cze nia uzy ska li ba da cze z in nych ośrod ków [5,20,21,22,23].…”

Current Arthroplasty Options in the Young Adult Hip

“…Westphal et al report in an in vitro study that initial cyclic motion of the Proxima (DePuy, Warsaw, IN) shortstemmed prosthesis is similar to that for a clinically successful Summit (DePuy, Warsaw, IN) stemmed implant, and therefore, bony ingrowth with long-term consolidation can be expected [ 88 ] . The Proxima implant tended to migrate more than the longer shaft prosthesis in the initial phase.…”

“…Large migration and cyclic motion are related to poor bone quality in the Proxima prosthesis. Westphal et al conclude that only patients with good bone quality should be considered for short-stemmed devices [ 88 ] .…”

“…There are also potential but unproven problems regarding metalon-metal wear debris and serum ion concentrations [ 90 ] . Furthermore, no improvement in sport activity level has yet been proven [ 88 ] . 2.…”

Periprosthetic bone density changes after MiniHipTMcementless femoral short stem: one-year results of dual-energy X-ray absorptiometry study

“…The available short stems differ in designs and outcomes [5]. Short stems are categorized into four groups: Type 1 femoral neck only, Type 2 calcar loading, Type 3 lateral flare calcar loading, and Type 4 shortened tapered.…”