Does Adding Information from Other Positions to Supine X-rays Change the Surgical Plan?

Q: Can it be applied directly to individual patients' treatment decisions?

Back-calculating the wedge cannot fully separate errors in surgical execution. The model was developed in subgroups defined by postoperative outcomes and has no external validation. Generalizability to centers that divide the sMCL is limited. Improvement in PROMs was not established.

In the valgus subgroup, mean error and RMSE were 0.0% ± 6.9% and 6.8% supine, −9.3% ± 7.8% and 12.1% standing, and +15.2% ± 6.7% and 16.6% under valgus stress.

A study chart comparing the predictive bias distribution of the WBLR in dormant posture and complex regression models, and JLCA subgroup bias. — Original Figure 4 compares prediction errors from supine simulation and a regression model combining several positions in the postoperative valgus subgroup. The combined model had smaller errors when positional differences in JLCA were large.
Geunwu Gimm, Hyunjeong Ra, Seok Gyun Yang, Byung Sun Choi, Du Hyun Ro, Hyuk-Soo Han. Complementary roles of standing, supine, and valgus-stress whole-leg radiographs in medial open-wedge high tibial osteotomy planning: supine minimizes bias, whereas standing and valgus-stress reduce outliers. Knee Surgery & Related Research (2026). https://doi.org/10.1186/s43019-026-00340-6
Evidence & Original Source Image use terms

The original surgery plan is also shown showing the reversal of angles corrected and the Miniaci-style WBLR simulation — Study design back-calculating correction from postoperative bone-angle changes and applying the same angle to each preoperative imaging position. It illustrates an analytical method, not a treatment guideline.
Geunwu Gimm, Hyunjeong Ra, Seok Gyun Yang, Byung Sun Choi, Du Hyun Ro, Hyuk-Soo Han. Complementary roles of standing, supine, and valgus-stress whole-leg radiographs in medial open-wedge high tibial osteotomy planning: supine minimizes bias, whereas standing and valgus-stress reduce outliers. Knee Surgery & Related Research (2026). https://doi.org/10.1186/s43019-026-00340-6
Evidence & Original Source Image use terms

Simulated versus actual postoperative WBLR from standing, supine and valgus-stress images. The upper row shows postoperative valgus and the lower row residual varus; distinguish correlation from agreement.
Geunwu Gimm, Hyunjeong Ra, Seok Gyun Yang, Byung Sun Choi, Du Hyun Ro, Hyuk-Soo Han. Complementary roles of standing, supine, and valgus-stress whole-leg radiographs in medial open-wedge high tibial osteotomy planning: supine minimizes bias, whereas standing and valgus-stress reduce outliers. Knee Surgery & Related Research (2026). https://doi.org/10.1186/s43019-026-00340-6 · Figure 2.
Evidence & Original Source Image use terms

Participants and Methods

This single-center retrospective study back-calculated the wedge angle from the actual ΔMPTA correction and reapplied that angle to preoperative standing, supine and valgus-stress images. Single-image simulations were compared with multivariable regression, using leave-one-out cross-validation (LOOCV). 71 MOWHTO patients. The main analysis involved 48 postoperative valgus patients; 23 had residual varus.

Main Findings

In the valgus subgroup, mean error and RMSE were 0.0% ± 6.9% and 6.8% supine, −9.3% ± 7.8% and 12.1% standing, and +15.2% ± 6.7% and 16.6% under valgus stress. The regression model combining standing and valgus-stress images had an R² of 0.606, compared with 0.080 for the supine-only model. Their RMSEs were 4.5% and 6.8%, respectively. In the subgroup with a standing–supine JLCA difference ≥ 2.7°, absolute prediction errors were 3.2% versus 6.8%, and RMSEs were 4.0% versus 9.0% (all P < 0.015).

The point of reading on surgery

This is an exploratory hypothesis: use supine images as the starting point and add standing and stress information when the JLCA difference between positions is large. The 2.7° threshold should not be treated as an established clinical criterion.

Limitations

Back-calculating the wedge cannot fully separate errors in surgical execution. The model was developed in subgroups defined by postoperative outcomes and has no external validation. Generalizability to centers that divide the sMCL is limited. Improvement in PROMs was not established.

Let's put it briefly.

What did this study confirm?

In the valgus subgroup, mean error and RMSE were 0.0% ± 6.9% and 6.8% supine, −9.3% ± 7.8% and 12.1% standing, and +15.2% ± 6.7% and 16.6% under valgus stress.

Can it be applied directly to individual patients' treatment decisions?

Keywords

High tibial osteotomy
Preoperative planning
Standing
Supine
Valgus-stress
Whole-leg radiograph
HTO
alignment

Abstract · Original text

Geunwu Gimm, Hyunjeong Ra, Seok Gyun Yang, Byung Sun Choi, Du Hyun Ro, Hyuk-Soo Han. Complementary roles of standing, supine, and valgus-stress whole-leg radiographs in medial open-wedge high tibial osteotomy planning: supine minimizes bias, whereas standing and valgus-stress reduce outliers. Knee surgery & related research. 2026;38(1):38. doi:10.1186/s43019-026-00340-6.

BACKGROUND

Accurate alignment correction is essential in medial open-wedge high tibial osteotomy (MOWHTO). However, conventional planning based on standing radiographs may not reflect postoperative intra-articular alignment changes. While differences between standing and supine radiographs have been investigated, the role of valgus-stress whole-leg radiographs in preoperative planning remains largely unexplored. This study evaluated the predictive accuracy of standing, supine, and valgus-stress whole-leg radiographs in MOWHTO planning and determined whether integrating these modalities improves alignment prediction compared with single-modality planning.

METHODS

This retrospective study included 71 patients who underwent MOWHTO. Preoperative standing, supine, and valgus-stress whole-leg radiographs, along with 1-year postoperative standing radiographs, were analyzed. To minimize the influence of surgical execution error and allow the analysis to focus on planning error, the achieved wedge angle was back-calculated from postoperative bony correction and reapplied to each preoperative modality to simulate the postoperative weight-bearing line ratio (Post-WBLR). Accuracy was assessed by comparing simulated and actual Post-WBLR. Multivariable regression was performed to identify predictors of actual Post-WBLR and to compare a multimodal model with the best-performing single-modality simulation.

RESULTS

In the postoperative valgus subgroup (n = 48), supine-based simulation showed no significant difference from actual Post-WBLR (mean difference, 0.0% ± 6.9%; root mean square error [RMSE], 6.8%). In contrast, standing-based simulation underestimated alignment (-9.3% ± 7.8%; RMSE, 12.1%), whereas valgus-stress simulation overestimated it (15.2% ± 6.7%; RMSE, 16.6%). A multimodal regression model incorporating simulated Post-WBLR from standing and valgus-stress radiographs demonstrated significantly improved predictive accuracy compared with the supine-only simulation (R2, 0.606 versus 0.080; RMSE, 4.5% versus 6.8%). Notably, in patients with a preoperative standing-to-supine joint line convergence angle difference (∆JLCAstanding-supine) ≥ 2.7°, the multimodal model significantly reduced prediction errors (absolute error: 3.2% versus 6.8%; RMSE: 4.0% versus 9.0%; all P < 0.015).

CONCLUSIONS

Supine radiographs generally provided the most accurate single-modality basis for MOWHTO planning. Standing and valgus-stress radiographs offered complementary information, and their integration improved prediction accuracy and reduced planning outliers. While further validation is required, a stepwise planning workflow-using supine radiographs as the default modality and multimodal integration when ∆JLCAstanding-supine ≥ 2.7°-may serve as an exploratory framework for reducing the risk of planning-related under- or overcorrection.

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The original paper.

Complementary roles of standing, supine, and valgus-stress whole-leg radiographs in medial open-wedge high tibial osteotomy planning: supine minimizes bias, whereas standing and valgus-stress reduce outliers

Geunwu Gimm, Hyunjeong Ra, Seok Gyun Yang, Byung Sun Choi, Du Hyun Ro, Hyuk-Soo Han
Knee Surgery & Related Research · 2026

DOI · 10.1186/s43019-026-00340-6 PubMed Based data

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