Kinematic alignment without femoral cartilage‐wear compensation for apex‐distal joint line obliquity: Effects on component alignment
Bibliographic record
Abstract
ABSTRACT Purpose Pronounced apex‐distal joint line obliquity (JLO) complicates total knee arthroplasty (TKA) by challenging patellofemoral tracking and medial tibial bone support. Joint line obliquity–modified kinematic alignment (JLO‐KA)—a selective modification of kinematic alignment (KA) that omits femoral cartilage‐wear compensation and reallocates correction to the tibial side—was developed. This study quantified postoperative component and limb alignment with JLO‐KA versus true KA. Methods Retrospective comparison of 20 JLO‐KA knees and 15 true‐KA knees with preoperative apex‐distal JLO (CPAK I–III). Pre‐/postoperative computed tomography (CT) measured lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), femoral component rotation (FCR), arithmetic hip–knee–ankle angle (aHKA), and JLO; postoperative Coronal Plane Alignment of the Knee (CPAK) distribution was analysed ( Δ = JLO‐KA minus true KA). Results Groups were similar at baseline: preoperative LDFA 87.7° versus 87.6°, MPTA 83.5° versus 83.5°, aHKA −4.3° versus −4.1°, JLO 171.2° versus 171.2° (all p > 0.05). Postoperatively, JLO‐KA increased LDFA to 90.4° ± 2.3° versus 87.0° ± 1.9° ( Δ = +3.4°, 95% confidence interval [CI]: 1.9–4.8; p < 0.0001), MPTA to 88.0° ± 1.4° versus 85.6° ± 2.0° ( Δ = +2.4°, 1.1–3.7; p = 0.0015), and FCR to 3.1° ± 2.0° versus 0.1° ± 2.0° ( Δ = +2.9°, 1.5–4.3; p = 0.0002), while aHKA was similar (−2.4° ± 3.1° vs. −1.4° ± 2.8°; Δ = −1.0°; p = 0.324). JLO was closer to neutral with JLO‐KA (178.4° ± 2.2° vs. 172.7° ± 2.8°; Δ = +5.8°; p < 0.001). Neutral‐JLO CPAK types (IV–VI) occurred in 16/20 (80%) versus 2/15 (13%) ( p = 0.00013). The restricted KA 90° ± 5° range for LDFA and MPTA was met by 19/20 (95%) versus 7/15 (47%) ( p = 0.0019). Conclusion Reallocating cartilage‐wear compensation from the medial femur to the medial tibia within the same calliper‐verified workflow reduced femoral valgus, limited tibial varus, and increased femoral external rotation by ≈3° while maintaining aHKA. Shifts were consistent with lateralizing the prosthetic trochlear groove and preserving medial tibial bone support, positioning JLO‐KA as a targeted option for apex‐distal knees (CPAK I–III). Level of Evidence Level III, retrospective comparative study.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".