Validation of a navigated hip replacement surgery system

Strathclyde theses - ask staff. Thesis no. : T13139Navigation of surgical instruments and implants plays an important role in the computer assisted surgery. OrthoPilot (TM) Hip Suite (BBraun Aesculap) is one such system used for hip navigation in orthopedic surgery. However the accuracy of this system remains to be determined independently of the manufacturer. The manufacturer supplies a technical specification for the accuracy of the system (± 2 mm and ± 2°) and previous research has been undertaken to compare its clinical accuracy against conventional hip replacements by x-ray. This clinical validation is important but contains many sources of error or deviation from an ideal outcome in terms of the surgeons' use of the system, inaccurate palpation of landmarks, variation in actual cup position from that given by the navigation system and measurement of the final cup position. It is therefore not possible to validate the claims of the manufacturer from this data. There is no literature evaluating the technical accuracy of the software i.e. the accuracy of the system given known inputs. The main aims of this study were to validate the OrthoPilot data capturing and to validate the cup navigation algorithm. The OrthoPilot was compared with the gold standard of a VICON movement analysis system. An aluminium pelvic phantom was machined with high accuracy to perform the experiments. Data were captured simultaneously from both OrthoPilot and VICON systems. Distances between the anatomical land marks, which defines the anterior pelvic plane on the pelvic phantom were compared to test the accuracy and the repeatability of the OrthoPilot data capturing. The accuracy of the hip navigation algorithm was tested by applying similar algorithm to calculate the native anteversion and inclination angles of the acetabulum using the VICON system. Both systems produce comparable results with small standard deviations. Finally, it can be concluded that from the laboratory based data, the OrthoPilot system, if used correctly, for the radiographic definition of the acetabular alignment using passive trackers, are sufficiently accurate for the orthopedic applications.Navigation of surgical instruments and implants plays an important role in the computer assisted surgery. OrthoPilot (TM) Hip Suite (BBraun Aesculap) is one such system used for hip navigation in orthopedic surgery. However the accuracy of this system remains to be determined independently of the manufacturer. The manufacturer supplies a technical specification for the accuracy of the system (± 2 mm and ± 2°) and previous research has been undertaken to compare its clinical accuracy against conventional hip replacements by x-ray. This clinical validation is important but contains many sources of error or deviation from an ideal outcome in terms of the surgeons' use of the system, inaccurate palpation of landmarks, variation in actual cup position from that given by the navigation system and measurement of the final cup position. It is therefore not possible to validate the claims of the manufacturer from this data. There is no literature evaluating the technical accuracy of the software i.e. the accuracy of the system given known inputs. The main aims of this study were to validate the OrthoPilot data capturing and to validate the cup navigation algorithm. The OrthoPilot was compared with the gold standard of a VICON movement analysis system. An aluminium pelvic phantom was machined with high accuracy to perform the experiments. Data were captured simultaneously from both OrthoPilot and VICON systems. Distances between the anatomical land marks, which defines the anterior pelvic plane on the pelvic phantom were compared to test the accuracy and the repeatability of the OrthoPilot data capturing. The accuracy of the hip navigation algorithm was tested by applying similar algorithm to calculate the native anteversion and inclination angles of the acetabulum using the VICON system. Both systems produce comparable results with small standard deviations. Finally, it can be concluded that from the laboratory based data, the OrthoPilot system, if used correctly, for the radiographic definition of the acetabular alignment using passive trackers, are sufficiently accurate for the orthopedic applications