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Femoral Bone Adaptation to Stable Long-Term Cemented Total Hip Arthroplasty in Dogs

Authors

  • Mary Sarah Bergh DVM,

    1. From the Comparative Orthopaedic Research Laboratory, Department of Surgical Sciences and Department of Medical Sciences, University of Wisconsin-Madison, School of Veterinary Medicine, Madison, WI
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  • Peter Muir BVSc, MVetClinStud, PhD, Diplomate ACVS,

    1. From the Comparative Orthopaedic Research Laboratory, Department of Surgical Sciences and Department of Medical Sciences, University of Wisconsin-Madison, School of Veterinary Medicine, Madison, WI
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  • Mark D. Markel DVM, PhD, Diplomate ACVS,

    1. From the Comparative Orthopaedic Research Laboratory, Department of Surgical Sciences and Department of Medical Sciences, University of Wisconsin-Madison, School of Veterinary Medicine, Madison, WI
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  • Paul A. Manley DVM, MSc, Diplomate ACVS

    1. From the Comparative Orthopaedic Research Laboratory, Department of Surgical Sciences and Department of Medical Sciences, University of Wisconsin-Madison, School of Veterinary Medicine, Madison, WI
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  • Presented at the Orthopaedic Research Society, Dallas, TX, February 10–13, 2002, and the American College of Veterinary Surgeons Symposium, Chicago, IL, October 11–14, 2001.

  • Funding provided by the Companion Animal Fund and a Student Research Fellowship, University of Wisconsin School of Veterinary Medicine.

Address reprint requests to Paul A. Manley, DVM, Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Department of Surgical Sciences, 2015 Linden Drive, Madison, WI 53706. E-mail: manleyp@svm.vetmed.wisc.edu

Abstract

Objective— To quantify long-term bone adaptation after stable cemented total hip arthroplasty (cTHA) in dogs.

Study Design— Clinical study.

Animals— Fourteen dogs.

Methods— Femoral specimens were collected from client-owned dogs that were donated after death because of causes unrelated to their cTHA. Mean (±SEM) dog age was 11.4±0.7 years and implant duration was 5.3±0.7 years. Implant stability was established from radiographic signs and gross mechanical stability. Femurs were evaluated at 3 levels based on implant length: proximal stem (PS), mid-stem (MS), and distal to stem (DS). Cortical area, medullary area, and porosity were measured at each level. Implanted femurs were compared to contralateral nonimplanted femurs.

Results— Cortical area and cortical porosity were significantly increased in implanted femurs compared to nonimplanted femurs. Cortical area was increased at the MS and DS levels, and porosity was increased at the PS and MS levels in implanted femurs. Porosity was greatest in the endosteal region at the PS and MS levels in implanted femurs.

Conclusions— Significant differences in femoral geometry and cortical porosity were detected after long-term stable cTHA. Net bone loss proximally and increased bone mass distally support stress shielding as a important mechanical factor associated with bone adaptation. Distribution of porosity shifts to endosteal regions after long-term cTHA.

Clinical Relevance— Significant site-specific femoral adaptation occurs in response to stable cTHA and may precede implant loosening.

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