Measured Resection and Gap Balancing Techniques Result in Similar Femoral Component Rotations Regardless of Preoperative Coronal Deformity: A Database Analysis of 3922 Cases
Bibliographic record
Abstract
A common goal in total knee arthroplasty (TKA) is to obtain collateral ligament balance in both flexion and extension while maintaining neutral overall coronal alignment. Femoral component rotation is a key variable in achieving this goal. There are two prominent techniques used in TKA to determine implant orientation, measured resection and gap balancing, but there is some controversy over which technique is superior. At our institution, we regularly use both techniques over a wide range of patients with varying degrees of preoperative coronal deformity. We therefore asked, using intraoperative measurements from a surgical navigation system, can we detect significant differences in external rotation of the femoral component between measured resection and gap balancing techniques, and do any such differences occur more frequently or at higher levels at particular values of preoperative coronal deformity? We analysed 3922 navigated TKA cases undertaken at our institution which had complete measurements of preoperative overall coronal alignment and external rotation of the femoral component relative to the dorsal condyles line. We then compared cases using measured resection to those using the gap balancing technique, stratifying patients by degree of preoperative coronal deformity and applying a two-sample t-test. A total of 1969 cases that used measured resection and 1953 cases that used the gap balancing techniques were identified. We found no significant differences between the two techniques across most of the preoperative coronal deformity groupings, though small differences were detected in two specific subgroups: the femoral component was slightly more externally rotated in the measured resection cohort when the preoperative coronal deformity was between neutral and 50 valgus (mean ± standard deviation - measured resection: 3.60 ± 1.10, gap balancing: 3.00 ± 1.10, p < 0.00625) and between 50 valgus and 100 valgus (measured resection: 4.30 ± 1.40, gap balancing: 3.70 ± 1.30, p < 0.00625). This study has shown that there were essentially no substantial differences between the external rotation of the femoral component between the gap balancing and measured resection techniques regardless of the degree of preoperative coronal deformity. Overall, we feel that surgical decisions regarding which technique to use should be based more on any correlations with other patient outcome measures that may be better elucidated in future studies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".