title: Load distribution on the radio-carpal joint for carpal arthrodesis.
abstract: OBJECTIVE
  Carpal fusions are useful for treating specific carpal disorders, maximizing postoperative wrist motion, hand strength, reducing pain and instability of the joint. The surgeon selects the appropriate treatment by considering the degree of stability, the chronicity of the injury, functional demands of the patient and former patient's outcomes as well. However there are not many studies regarding the load distribution provided by the treatment. So, the purpose of this study is to analyze the load distribution through the wrist joint with an arthrodesis treatment and compare the results with a normal wrist.
  
  
  METHODS
  To this end the rigid body spring model (RBSM) method was used on a three-dimensional model of the wrist joint. The cartilage and ligaments were simulated as springs acting under compression and tension, respectively, while the bones were considered as rigid bodies. To simulate the arthrodesis, the fused bones were considered as a single rigid body.
  
  
  RESULTS
  The changes on the load distribution for each arthrodesis agree with the treatment objective, reducing load transmission through a specific articular surface. For example, for SLAC/SNAC II most of the treatments reduced the load transmitted through the radioscaphoid fossae, almost by 8%. However, the capitolunate (CL) arthrodesis was the treatment that managed to keep the load transmitted through the radiolunate joint closer to normal conditions. Also, in treatments where the scaphoid was excised (3-corner, 4-corner and capitolunate arthrodesis), the joint surface between the lunate surface compensates by doubling the transmitted force to the radius.
  
  
  CONCLUSIONS
  The common arthrodesis for treating SLAC/SNAC II-III, reduces, in fact, the load on the radioscaphoid joint. Alternative treatments that reduce load distribution on the radiocarpal joint should be three corner and capitolunate arthrodesis for treating SLAC/SNAC-II; and for SLAC/SNAC-III four corners with scaphoid excision. On Kienbock's disease. Scaphocapitate (SC) arthrodesis is more effective on reducing the load transmission through the radiolunate and ulnolunate joints. All arthrodesis treatment should consider changes on the load transmission, and also bones' fusion rates and pain reduction on patient's outcomes.
authors.affiliation: Department of Mechanical and Mechatronics Engineering, Numerical Methods and Modeling Group Research (GNUM), Universidad Nacional de Colombia, Bogotá, Colombia; Biological Reactives Group: Mechanobiology of Organs and Tissues, Instituto de Biotecnología, Universidad Nacional de Colombia, Bogotá, Colombia.
authors.forename: Kalenia
authors.initials: K
authors.lastname: Márquez-Florez
authors.affiliation: Department of Orthopaedic Surgery, School of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia.
authors.forename: Enrique
authors.initials: E
authors.lastname: Vergara-Amador
authors.affiliation: Department of Mechanical and Mechatronics Engineering, Numerical Methods and Modeling Group Research (GNUM), Universidad Nacional de Colombia, Bogotá, Colombia.
authors.forename: Maria
authors.initials: M
authors.lastname: Gavilán-Alfonso
authors.affiliation: Department of Mechanical and Mechatronics Engineering, Numerical Methods and Modeling Group Research (GNUM), Universidad Nacional de Colombia, Bogotá, Colombia; Biological Reactives Group: Mechanobiology of Organs and Tissues, Instituto de Biotecnología, Universidad Nacional de Colombia, Bogotá, Colombia. Electronic address: dagarzona@unal.edu.co.
authors.forename: Diego
authors.initials: D
authors.lastname: Garzón-Alvarado
mesh_terms: D001174:Arthrodesis; D050824:Carpal Joints / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008962:Models, Theoretical
keywords: Arthrodesis; Computational model; Hand loads; Wrist analysis