Thesis
Validation of the OrthoPilot lower limb model : the accuracy of the calculated knee centre in computer navigated total knee replacement
- Creator
- Awarding institution
- University of Strathclyde
- Date of award
- 2014
- Thesis identifier
- T13892
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Total knee arthroplasties (TKA) are carried out as a last resort to relieve joint pain and disability in those with degenerative joint conditions. As failures in lower limb alignment are known to result in joint loosening, accurate patient-specific joint centre localisation is vital in order to minimise the risk of joint failure. The use of computers in TKA is becoming an increasingly vital tool to this procedure. These may actively help in the surgery itself in the form of robotic arms or passively by locating joint centres and calculating mechanical axes. Of interest to this project are the intra-operative navigation techniques which determine hip, knee, and ankle centres and the mechanical axes between them to direct the surgeon to make accurate resections. To do this, the kinematic centre of the knee must be calculated without error to produce a successful surgery. To determine the relationship between the kinematic and anatomical knee centre, post-operative CT images of 21 navigated (OrthoPilot; B. Braun, Aesculap, Tuttlingen, Germany) TKAs were analysed in this retrospective study. Also compared were relative ankle and knee widths, femur and tibia lengths and the mechanical femorotibial angle (MFT angle) in both data sets to find any significant differences. The main findings were that the OrthoPilot calculated knee centre was, on average, 33.8± 6.8mm proximal to the anatomical centre. Between all the relative distances, only the femoral length showed a significant difference (p=0.03) between the OrthoPilot and CT data which may be due to the large error in knee joint positions in each system. Post-operative alignment angles from CT data showed good alignments as one patient failed to achieve an alignment between 0°± 3°. From the intraoperative angles generated by the OrthoPilot, two patients had alignments outside of the 0°± 3° range which overall is a large percentage of the group, 10%). The effects of age and BMI on these values were also investigated to find no strong correlations. Based on these findings it was concluded that the OrthoPilot is capable of creating a highly accurate lower limb model which achieves good post-operative alignment. In the case of the outliers, further research with a larger group would be required to determine the cause of failure.
- Resource Type
- DOI
- Date Created
- 2014
- Former identifier
- 1041814
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