Purpose Accurate execution of preoperative plans in corrective femoral osteotomies remains a substantial challenge. Current techniques are limited by variable accuracy, invasiveness, and substantial radiation exposure, with free-hand methods and patient-specific instrumentation (PSI) often requiring <InlineEquation ID="IEq1"> <EquationSource Format="TEX">${>30}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>></mo> <mn>30</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${>6}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>></mo> <mn>6</mn> </mrow> </math></EquationSource> </InlineEquation> fluoroscopic images, respectively. This work addresses the need for an accurate navigation system that minimizes dissection and intraoperative fluoroscopy. Methods We present an integrated, electromagnetic tracking (EMT)-based navigation system for femoral osteotomies. The system couples CT-based preoperative bone planning with one-time intraoperative C-arm calibration and accurate X-ray-to-CT registration, based on two fluoroscopic images acquired at initialization. This registration is followed by real-time, fluoroscopy-free EMT-based navigation of the sawblade, and subsequently of the bone fragments, with respect to the preoperative plan, and is compatible with uniplanar and biplanar osteotomies. Results In a feasibility study utilizing 18 synthetic femora, EMT guidance significantly outperformed free-hand execution for total angular error (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$(3.05 \pm 0.75)^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mo stretchy="false">(</mo> <mn>3.05</mn> <mo>±</mo> <mn>0.75</mn> <mo stretchy="false">)</mo> </mrow> <mo>∘</mo> </msup> </math></EquationSource> </InlineEquation> vs. <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$(6.32 \pm 2.36)^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mo stretchy="false">(</mo> <mn>6.32</mn> <mo>±</mo> <mn>2.36</mn> <mo stretchy="false">)</mo> </mrow> <mo>∘</mo> </msup> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$p=0.031$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>=</mo> <mn>0.031</mn> </mrow> </math></EquationSource> </InlineEquation>). No EMT-guided trials exceeded the <InlineEquation ID="IEq6"> <EquationSource Format="TEX">${5}^{\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mn>5</mn> </mrow> <mo>∘</mo> </msup> </math></EquationSource> </InlineEquation> clinical threshold, whereas free-hand resulted in 4 outliers out of 6 trials while assuming the same full surgical exposure for both techniques. The system achieved statistical equivalence (<InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\pm 2^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>±</mo> <msup> <mn>2</mn> <mo>∘</mo> </msup> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq8"> <EquationSource Format="TEX">$\pm 2\,\text {mm}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>±</mo> <mn>2</mn> <mspace width="0.166667em" /> <mtext>mm</mtext> </mrow> </math></EquationSource> </InlineEquation>) to PSI for total angular (<InlineEquation ID="IEq9"> <EquationSource Format="TEX">$p \le 0.02$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>≤</mo> <mn>0.02</mn> </mrow> </math></EquationSource> </InlineEquation>) and total translational (<InlineEquation ID="IEq10"> <EquationSource Format="TEX">$p=0.048$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>=</mo> <mn>0.048</mn> </mrow> </math></EquationSource> </InlineEquation>) errors with no significant differences in user questionnaire scores. Conclusion The proposed EMT-based system enables transfer of preoperative plans to the OR using two fluoroscopic images and provides real-time intraoperative guidance. In a synthetic bone feasibility study, it substantially improved correction accuracy over free-hand execution and achieved equivalent accuracy to PSI, while no additional surgical exposure is needed and requiring substantially fewer fluoroscopic images, motivating subsequent cadaveric and clinical validation.

Electromagnetic navigation for femoral osteotomy using high-accuracy X-ray-to-CT registration

期刊论文
发表日期：

2026年6月20日

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Roman Flepp,
Arend Nieuwland,
Bastian Sigrist,
Philipp Fürnstahl,
Lilian Calvet,
Thomas Dreher

摘要

Purpose

Accurate execution of preoperative plans in corrective femoral osteotomies remains a substantial challenge. Current techniques are limited by variable accuracy, invasiveness, and substantial radiation exposure, with free-hand methods and patient-specific instrumentation (PSI) often requiring ${>30}$ $> 30$ and ${>6}$ $> 6$ fluoroscopic images, respectively. This work addresses the need for an accurate navigation system that minimizes dissection and intraoperative fluoroscopy.

Methods

We present an integrated, electromagnetic tracking (EMT)-based navigation system for femoral osteotomies. The system couples CT-based preoperative bone planning with one-time intraoperative C-arm calibration and accurate X-ray-to-CT registration, based on two fluoroscopic images acquired at initialization. This registration is followed by real-time, fluoroscopy-free EMT-based navigation of the sawblade, and subsequently of the bone fragments, with respect to the preoperative plan, and is compatible with uniplanar and biplanar osteotomies.

Results

In a feasibility study utilizing 18 synthetic femora, EMT guidance significantly outperformed free-hand execution for total angular error ( $(3.05 \pm 0.75)^\circ $ ${(3.05 \pm 0.75)}^{\circ}$ vs. $(6.32 \pm 2.36)^\circ $ ${(6.32 \pm 2.36)}^{\circ}$ , $p=0.031$ $p = 0.031$ ). No EMT-guided trials exceeded the ${5}^{\circ }$ $5^{\circ}$ clinical threshold, whereas free-hand resulted in 4 outliers out of 6 trials while assuming the same full surgical exposure for both techniques. The system achieved statistical equivalence ( $\pm 2^\circ $ $\pm 2^{\circ}$ , $\pm 2\,\text {mm}$ $\pm 2 mm$ ) to PSI for total angular ( $p \le 0.02$ $p \leq 0.02$ ) and total translational ( $p=0.048$ $p = 0.048$ ) errors with no significant differences in user questionnaire scores.

Conclusion

The proposed EMT-based system enables transfer of preoperative plans to the OR using two fluoroscopic images and provides real-time intraoperative guidance. In a synthetic bone feasibility study, it substantially improved correction accuracy over free-hand execution and achieved equivalent accuracy to PSI, while no additional surgical exposure is needed and requiring substantially fewer fluoroscopic images, motivating subsequent cadaveric and clinical validation.