title: Relationship between bone adaptation and in-vivo mechanical stimulus in biological reconstructions after bone tumor: A biomechanical modeling analysis.
abstract: BACKGROUND
  Biomechanical interpretations of bone adaptation in biological reconstructions following bone tumors would be crucial for orthopedic oncologists, particularly if based on quantitative observations. This would help plan for surgical treatments, rehabilitative programs and communication with the patients. We aimed to analyze the biomechanical adaptation of a femoral reconstruction after Ewing sarcoma according to an increasingly-used surgical technique, and to relate in-progress bone resorption to the mechanical stimulus induced by different motor activities.
  
  
  METHODS
  We created a multiscale musculoskeletal and finite element model from CT scans and motion analysis data at a 76-month follow-up of a patient, to analyze muscle and joint loads, and to compare the mechanical competence of the reconstructed bone with the contralateral limb, in the current real condition and in a possible revision surgery that removed proximal screws.
  
  
  RESULTS
  Our results showed strategies of muscle coordination that led to differences in joint loads between limbs more marked in more demanding motor activities, and generally larger in the contralateral limb. The operated femur presented a markedly low ratio of physiological strain due to load-sharing with the metal implant, particularly in the lateral aspect. The possible revision surgery would help restore a physiological strain configuration, while the safety of the reconstruction would not be threatened.
  
  
  CONCLUSIONS
  We suggest that bone resorption is related to load-sharing and to the internal forces exerted during movement, and the mechanical stimulus should be improved by adopting modifications in the surgical treatment and by promoting physical therapy aimed at specific muscle strengthening.
authors.affiliation: Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy. Electronic address: valente@tecno.ior.it.
authors.forename: Giordano
authors.initials: G
authors.lastname: Valente
authors.affiliation: Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Pitto
authors.affiliation: Computational Bioengineering Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Schileo
authors.affiliation: Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Sabina
authors.initials: S
authors.lastname: Piroddi
authors.affiliation: Movement Analysis Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Leardini
authors.affiliation: Orthopedic and Traumatologic Clinic for Musculoskeletal Tumors, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Manfrini
authors.affiliation: Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Fulvia
authors.initials: F
authors.lastname: Taddei
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D001696:Biomechanical Phenomena; D001859:Bone Neoplasms / Q000503:physiopathology / Q000601:surgery*; D001862:Bone Resorption / Q000503:physiopathology; D002648:Child; D005269:Femur / Q000503:physiopathology / Q000601:surgery*; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D019651:Plastic Surgery Procedures / Q000379:methods; D012512:Sarcoma, Ewing / Q000503:physiopathology / Q000601:surgery*; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*
keywords: Biological reconstruction; Bone mechanical stimulus; Bone tumor; Subject-specific finite element modeling; Subject-specific musculoskeletal modeling