VALIDATING A NEW REFERENCE PLANE FOR IMAGE-FREE NAVIGATION OF ACETABULAR CUP PLACEMENT
Bibliographic record
Abstract
The existing image-free Total Hip Arthroplasty (THA) navigation systems conventionally utilise the patient-specific Anterior Pelvic Plane (APP) as the reference to calculate orientations of the implanted cup, e.g. anteversion and inclination angles. The definition of APP relies on the intra-operative digitisation of three anatomical landmarks, the bilateral Anterior Superior Iliac Spine (ASIS) and the pubicum. Due to the presence of the thick soft tissue around the patient's pubic region, however, the landmark on pubic area is hard to be digitised accurately. A novel reference plane called Intra-operative Reference Plane (IRP) was proposed by G. Zheng et al to address this issue. To determine the IRP, bilateral ASIS and the cup center of the operating side instead of the pubicum are digitised intra-operatively. It avoids the error-prone digitisation of pubicum, and the angle between the patient-specific APP and the suggested IRP can be computed pre-operatively by a single X-ray radiograph-based 2D/3D reconstruction approach developed by G. Zheng et al. Based on this angle, the orientation of the APP can be intra-operatively estimated from that of the IRP such that all measurements with respect to IRP can be transformed to measurements with respect to APP. In order to implement and validate this new reference plane for image-free navigation of acetabular cup placement, we developed an IRP-based image-free THA navigation system. All cup placement instruments were mounted with passive markers whose positions could be traced by a NDI Polaris® infrared camera (Northern Digital Inc, Ontario, Canada). The cup center was obtained by first pivoting a tracked impactor with appropriate size of the mounted trial cup and then calculating the pivoting center through a least-squares fitting. The bilateral ASIS landmarks were acquired through the percutaneous pointer-based digitisation. We tested this new IRP-based image-free THA navigation system in our laboratory by conducting twelve studies on two dry cadaver pelvises and two plastic pelvises. The ground truth for each study was established using the conventional APP-based method, i.e., in addition to those landmarks required by our IRP-based method, we also digitised the pubicum on respective pelvic bones and calculated cup orientations on the basis of the digitised APP. The mean and standard deviation of differences between the proposed IRP-based anteversion measurement and the ground truth are 1.0 degree and 0.7 degree, while the maximal and minimal differences are 2.1 degree and 0.3 degree respectively. The mean and standard deviation of differences between the proposed IRP-based inclination measurement and the ground truth are respective 0.2 degree and 0.2 degree. Moreover, the maximum of differences is 0.5 degree and the minimum is 0.0 degree. Our laboratory experimental results demonstrate that the new IRP-based image-free navigation system is accurate enough for acetabular cup placement. In comparison to existing image-free navigation systems that use APP as the reference plane, the newly developed system employs IRP as the reference plane, which has the advantage to eliminate the digitisation of landmarks around the pubic region. The successful validation with the laboratorial study has led us to the next step of clinical trials. We expect to report preliminary clinical cases in the near future.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.012 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".