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Online ISSN 1827-1707
Iversen B. F. 1,2, Levi N. 1
1 Department of Orthopaedic Surgery Frederiksberg Hospital University of Copenhagen, Copenhagen Denmark
2 Department of Biomedical Engineering Institute of Orthopaedics University of London, London, UK
Aim. Range of motion (ROM) is a critical feature in the design of total hip arthroplasties. In contrast to the senile coxarthrosis patient, the free ROM available after the hip joint replacement is of great interest to the young patient. Many types of technology have been used to study ROM including either very simple manual goniometer, or much more complicated computer simulation, virtual reality computer animation and three-dimensional finite element analysis. The aim of the present study was to present a new experimental method by which the ROM of a total hip arthroplasty could be assessed.
Methods. An experimental rig comprising a hemipelvis and a proximal femur was supplied with a total hip arthroplasty. The rig was connected to a data acquisition system capable of measuring the three angles corresponding to flexion/extension, ab/adduction and external/internal rotation of the hip. Position in which impingement took place between the prosthetic neck and cup or between the bony structures of the femur and pelvis were recorded.
Results. Graphs, were created demonstrating the maximal ROM permitted by the prosthesis, with attention also paid to the way in which the bony structures of the femur and pelvis influenced the ROM of the total hip arthroplasty.
Conclusion. It appears that abduction and external rotation are indeed the safest area of movement.