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Online ISSN 1827-1707
Iversen B. F. 1,2, Levi N. 1,3
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
3 Department of Orthopaedic Surgery Sunderby Hospital Lulea, Sweden
Aim. Component placement critically affects the performance and longevity of total hip replacement and malpositioned components can result in dislocation, impingement, limited range of movement and increase polyethylene wear. The use of standard mechanical guides often provided by the manufacturers of the implants has been shown to result in large variations of cup inclination and version. Computer-based surgical navigation has been used to improve the accuracy of component placement. However, there has been criticism of these new devises, mainly of the extra cost and often difficult and time consuming intraoperative procedures. In this paper we describe a new mechanical navigation system and determine its accuracy.
Methods. Bilateral total hip replacement was performed on 10 cadavers. On one side, the prosthesis was inserted in accordance with the standard surgical procedure with the goal to orient the cup to 45° of abduction and a sum of 30° of anteversion for the cup and stem. The new mechanical navigation system was used in the contralateral hip.
Results. The median deviation from the intended total of 30° of anteversion with conventional technique was 9° (range 1-23°). With the revised technique, the median deviation from the intended 30° of anteversion was 4° (range 0-9°). The difference was statistically significant (P<0.05).
Conclusion. This cadaver study shows that a new mechanical navigation system allowed for more consistent placement of the acetabular cup.