An Experimental Setup for Instrumental Analysis of Femoral Derotation Osteotomy

Auer, Christoph; Kallus, Sebastian; Eisenmann, Urs; Körber, Jürgen; Wolf, Sebastian I.; Dickhaus, Hartmut

doi:10.1515/bmt-2013-4302

Cited by 5 publications

(12 citation statements)

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“…The accessible bone surface between both k‐wires and the line of osteotomy were sampled with an EMT pointer device (FlexPointer E01 2002, fiagon GmbH, Berlin, Germany) for virtual reconstruction of local femur geometry, delivering the required context to calculate total derotation effect in the transversal plane. The bone shaft axis (rotational axis) is obtained using numerical optimization . Real time processing, analysis and documentation of the collected measurement data were carried out using previously developed research software interfacing with the tracking hardware (see Fig.…”

Section: Methodsmentioning

confidence: 99%

Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study

et al. 2016

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Correction of rotational gait abnormalities is common practice in pediatric orthopaedics such as in children with cerebral palsy. Femoral derotation osteotomy is established as a standard treatment, however, different authors reported substantial variability in outcomes following surgery with patients showing over- or under-correction. Only 60% of the applied correction is observed postoperatively, which strongly suggests intraoperative measurement error or loss of correction during surgery. This study was conducted to verify the impact of error sources in the derotation procedure and assess the utility of a newly developed, instrumented measurement system based on electromagnetic tracking aiming to improve the accuracy of rotational correction. A supracondylar derotation osteotomy was performed in 21 artificial femur sawbones and the amount of derotation was quantified during the procedure by the tracking system and by nine raters using a conventional goniometer. Accuracy of both measurement devices was determined by repeated computer tomography scans. Average derotation measured by the tracking system differed by 0.1° ± 1.6° from the defined reference measurement . In contrast, a high inter-rater variability was found in goniometric measurements (range: 10.8° ± 6.9°, mean interquartile distance: 6.6°). During fixation of the osteosynthesis, the tracking system reliably detected unintentional manipulation of the correction angle with a mean absolute change of 4.0° ± 3.2°. Our findings show that conventional control of femoral derotation is subject to relevant observer bias whereas instrumental tracking yields accuracy better than ±2°. The tracking system is a step towards more reliable and safe implementation of femoral correction, promising substantial improvements of patient safety in the future. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1106-1112, 2017.

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Section: Methodsmentioning

confidence: 99%

Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study

et al. 2016

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“…The intra‐operative derotation angle was controlled by the Electromagnitc tracking system operated by a technician. The system setup included a field generator (Aurora v.2, Northern Digital, Waterloo, Canada) in combination with EMT sensors embedded in a clamp shell (PointerShell E01 2902, fiagon GmbH, Berlin, Germany) . The sensors were attached to the same conventional k‐wires used for optical goniometric control as described in detail above.…”

Section: Methodsmentioning

confidence: 99%

“…Virtual reconstruction of local femur geometry and the osteotomy site was accomplished through sampling of the bone surface between both K‐wires and the line of osteotomy with an EMT pointer device (FlexPointer E01 2002, fiagon GmbH, Berlin, Germany) delivering the required context to calculate total derotation effect in the transversal plane. The bone shaft axis (rotational axis) is obtained using numerical optimization . Real time processing, analysis, and documentation of the collected measurement data was carried out using previously developed research software interfacing with the tracking hardware (Also see supplement Figs.…”

Section: Methodsmentioning

confidence: 99%

“…The system setup included a field generator (Aurora v.2, Northern Digital, Waterloo, Canada) in combination with EMT sensors embedded in a clamp shell (PointerShell E01 2902, fiagon GmbH, Berlin, Germany). 23 The sensors were attached to the same conventional k-wires used for optical goniometric control as described in detail above. Virtual reconstruction of local femur geometry and the osteotomy site was accomplished through sampling of the bone surface between both K-wires and the line of osteotomy with an EMT pointer device (FlexPointer E01 2002, fiagon GmbH, Berlin, Germany) delivering the required context to calculate total derotation effect in the transversal plane.…”

Section: Measurementmentioning

confidence: 99%

“…The bone shaft axis (rotational axis) is obtained using numerical optimization. 23 Real time processing, analysis, and documentation of the collected measurement data was carried out using previously developed research software interfacing with the tracking hardware (Also see supplement Figs. 1 and 2).…”

Section: Measurementmentioning

confidence: 99%

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Electromagnetic tracking for femoral derotation osteotomy—an in vivo study

Geisbüsch

Auer

Dickhaus

et al. 2017

Journal Orthopaedic Research

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Femoral derotation osteotomy delivers good to excellent results in the treatment of rotational gait abnormalities and especially in internal rotation gait. The outcome of the procedure has been evaluated in numerous short- and long-term studies. Although reasons for recurrence and over-/under-correction have been unveiled in earlier studies the mechanisms are still not fully understood. False intra-operative assessment of the derotation angle may contribute to imprecise outcomes. In a recent saw-bone study we evaluated an electromagnetic tracking system in comparison to conventional goniometer measurement and a CT reference measurement and found it to be extremely accurate, whereas the use of a conventional goniometer for derotation measurement showed a high inter- and intra-rater variability. The current study evaluates the electromagnetic tracking system for continuous intra-operative derotation control under real OR conditions. Adults (age: 18-40 years) with the diagnosis of internal rotation gait, independent of the underling pathology, undergoing a supracondylar deroation osteotomy were included. A rotational CT scan was conducted before and in close proximity after surgery and the difference served as reference for the electromagnetic tracking results. The results showed a mean deviation of 2.6° (1.2-5.5°) in comparison to the reference measurement of the pre- and post-operative CT scans. The system proved to be stable under OR conditions with a good usability and a small technical footprint. Electromagnetic tracking delivers a precise, reliable, and independent assessment of intra-operative derotation angles in femoral derotation osteotomies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2652-2657, 2017.

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Femoral derotation osteotomy—Does intraoperative electromagnetic tracking reflect the dynamic outcome?

Geisbüsch

Götze

Putz

et al. 2021

Journal Orthopaedic Research

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Femoral derotation osteotomy (FDO) is a well-established procedure for the correction of internal rotation gait in children with cerebral palsy. Various studies have demonstrated good results for FDO both in short-term and long-term evaluation with some describing recurrence and over-or under-corrections. The present study evaluates the use of an objective intraoperative derotation measurement through electromagnetic tracking. We report the static and dynamic results of 11 cases with internal rotation gait (8 male, 3 female, mean age 22.2 years), that underwent FDO with intraoperative electromagnetic tracking and conventional goniometric measurement of the correction. The dynamic and static changes were assessed through three-dimensional gait analysis after a mean of 12 months after surgery and rotational imaging preoperative and after a mean of eleven days postoperatively. Mean hip rotation in stance significantly decreased from 20.9°(SD 5.9) to 5.8°(SD 4.7°) after FDO. The mean amount of derotation quantified by electromagnetic tracking was 23.2°(16.5°-28.8°) and 25.1°(20.0°-33.0°) for goniometric measurement. Both measurement modalities showed small differences to rotational imaging (electromagnetic bone tracking [EMT]: 0.72°; goniometer: 1.19°) but a large deviation when compared to three-dimensional gait analysis (EMT: 8.5°, goniometer: 9.1°). In comparison to the static changes and EMT measurement, the dynamic changes measured during 3-D-gait analysis reflected only 66% of the actual derotation performed during surgery. Although electromagnetic tracking allows a precise intraoperative assessment of the derotation during FDO, the amount of intraoperative correction is not reflected in the improvements in three-dimensional gait analysis.

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An Experimental Setup for Instrumental Analysis of Femoral Derotation Osteotomy

Cited by 5 publications

References 0 publications

Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study

Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study

Electromagnetic tracking for femoral derotation osteotomy—an in vivo study

Femoral derotation osteotomy—Does intraoperative electromagnetic tracking reflect the dynamic outcome?

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