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Strains caused by daily loading might be responsible for delayed healing of an incomplete atypical femoral fracture
Lund University, Sweden.
Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Orthopaedics in Linköping. Linköping University, Faculty of Medicine and Health Sciences.
Lund University, Sweden.
Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Orthopaedics in Linköping.
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2016 (English)In: Bone, ISSN 8756-3282, E-ISSN 1873-2763, Vol. 88, 125-130 p.Article in journal (Refereed) PublishedText
Abstract [en]

Atypical femoral fractures are insufficiency fractures in the lateral femoral diaphysis or subtrochanteric region that mainly affect older patients on bisphosphonate therapy. Delayed healing is often seen in patients with incomplete fractures (cracks), and histology of bone biopsies shows mainly necrotic material inside the crack. We hypothesized that the magnitude of the strains produced in the soft tissue inside the crack during normal walk exceeds the limit for new bone formation, and thereby inhibit healink. A patient specific finite element model was developed, based on clinical CT images and high resolution CT images of a biopsy from the crack site. Strain distributions in the femur and inside the crack were calculated for load cases representing normal walk. The models predicted large strains inside the crack, with strain levels above 10% in more than three quarters of the crack volume. According to two different tissue differentiation theories, bone would only form in less than 1-5% cif the crack volume. This can explain the impaired healing generally seen in incomplete atypical fractures. Furthermore, the microgeometry of the crack highly influenced the strain distributions. Hence, a realistic microgeometry needs to be considered when modeling the crack. Histology of the biopsy showed signs of remodeling in the bone tissue adjacent to the fracture line, while the crack itself contained mainly necrotic material and signs of healing only in portions that seemed to have been widened by resorption. In conclusion, the poor healing capacity of incomplete atypical femoral fractures can be explained by biomechanical factors, and daily low impact activities are enough to cause strain magnitudes that prohibit bone formation. (C) 2016 Elsevier Inc. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE INC , 2016. Vol. 88, 125-130 p.
Keyword [en]
Atypical femoral fracture; Finite element analysis; mu CT; Impaired healing
National Category
Orthopedics
Identifiers
URN: urn:nbn:se:liu:diva-130120DOI: 10.1016/j.bone.2016.04.020ISI: 000377925100015PubMedID: 27113528OAI: oai:DiVA.org:liu-130120DiVA: diva2:948605
Note

Funding Agencies|Swedish National Centre for Research in Sports; Swedish Foundation for Strategic Research [IB13-0021]; Ostergotland County Council

Available from: 2016-07-12 Created: 2016-07-11 Last updated: 2016-07-12

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Schilcher, JörgAspenberg, Per
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Division of Clinical SciencesDepartment of Orthopaedics in LinköpingFaculty of Medicine and Health Sciences
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