title: The impact of proximal femoral morphology on failure strength with a mid-head resection short-stem hip arthroplasty.
abstract: Mid-head resection short-stem hip arthroplasty is a conservative alternative to conventional total hip replacement and addresses proximal fixation challenges in patients not suitable for hip resurfacing. It is unclear whether proximal femoral morphology impacts the ultimate failure load of mid-head resection implanted femurs, thus the aim of this study was to investigate the effect of native neck-shaft angle (NSA) and coronal implant alignment on proximal femoral strength. In total, 36 synthetic femurs with two different proximal femoral morphologies were utilized in this study. Of them, 18 femurs with a varus NSA of 120° and 18 femurs with a valgus NSA of 135° were each implanted with a mid-head resection prosthesis. Femurs within the two different femoral morphology groups were divided into three equal coronal implant alignment groups: 10° valgus, 10° varus or neutral alignment. Prepared femurs were tested for stiffness and to failure in axial compression. There was no significant difference in stiffness nor failure load between femurs implanted with valgus-, varus- or neutrally aligned implants in femurs with a NSA of 120° (p = 0.396, p = 0.111, respectively). Femurs implanted in valgus orientation were significantly stiffer and failed at significantly higher loads than those implanted in varus alignment in femurs with a NSA of 135° (p = 0.001, p = 0.007, respectively). A mid-head resection short-stem hip arthroplasty seems less sensitive to clinically relevant variations of coronal implant alignment and may be more forgiving upon implantation in some femoral morphologies, however, a relative valgus component alignment is recommended.
authors.affiliation: Martin Orthopaedic Biomechanics Laboratory, Li Ka Shing Institute, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada michael.olsen@utoronto.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: Olsen
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Al Saied
authors.affiliation: Martin Orthopaedic Biomechanics Laboratory, Li Ka Shing Institute, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Morison
authors.affiliation: Martin Orthopaedic Biomechanics Laboratory, Li Ka Shing Institute, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Sellan
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: James P
authors.initials: JP
authors.lastname: Waddell
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Emil H
authors.initials: EH
authors.lastname: Schemitsch
mesh_terms: D019245:Compressive Strength; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D005269:Femur / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D011474:Prosthesis Design; D013314:Stress, Mechanical; D013718:Tensile Strength
keywords: Mid-head resection; biomechanical testing; femur; short-stem hip arthroplasty