Biomechanical Evaluation of Screw‐In Femoral Implant in Cementless Total Hip System

Abstract

Helica femoral prosthesis alters strain distribution in the proximal aspect of the femur and exhibits initial micromotion. Failure load in axial compression of the Helica-implanted femur is less than that of the normal femur, but greater than that expected in vivo.

Biomechanical evaluation of the helica femoral implant system using traditional and modified techniques

“…Bone medial surface strain in this study and a recent Helica study revealed significantly different results after prosthesis implantation. Medial strain data for intact femora are comparable between studies (−570 µstrain in the current study vs. −800 µstrain in the study by Kim et al); however, medial strain becomes much less compressive (−190 µstrain) using the traditional technique in the previous study compared to greater compressive strain using both the traditional and modified techniques in the current study (−700 and −790 µstrain, respectively). There are several possible reasons for greater compressive medial strain after implantation in the current study—most notably implant size selection and surgical procedure.…”

“…Total hip replacement (THR) for treatment of coxofemoral osteoarthritis secondary to canine hip dysplasia, traumatic osteoarthritis, coxofemoral luxation, avascular necrosis of the femoral head, and failed femoral head and neck excision has been evolving in veterinary medicine since the 1970s . Despite great therapeutic potential, complications with varying degrees of clinical importance occur with cemented and cementless fixation systems.…”

“…One strategy for optimizing femoral cortex loads after prosthesis implantation is elimination of the diaphyseal component of the femoral implant stem and preservation of the neck of the femur. In theory, preservation of the femoral neck will result in a more physiologic fixation . Evidence that the femoral neck implant design may help achieve this goal was found in a cadaver study that observed more physiologic proximomedial femoral cortical bone strains in femora loaded after implantation with a femoral neck implant compared to a conventional stem implant …”

“…A clinical review of 39 dogs with 40 Helica THR revealed acetabular cup loosening in 4 patients; bone resorption subjacent the implant collar in two patients; and femoral neck fracture, femoral implant loosening, sciatic palsy, and fissure fracture, each in 1 patient . Radiolucency around the femoral implant and bone resorption around the collar indicate biological and/or mechanical loosening may be present.…”

Zurich Cementless Total Hip Replacement

“…achieve short-term stability by various methods depending on the implant system used (press-fit, locking screw fixation, or screw-in implants) and long-term stability via bone in-growth (on-growth) into implants. [5][6][7] The Zurich Cementless THR (Kyon, Zurich, Switzerland) was developed at the University of Zurich in the late 1990s 6 (Fig. 1).…”