Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study.
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.
Department of Orthopaedic and Trauma Surgery, University Hospital Heidelberg, Schlierbacher Landstraße 200a, Heidelberg 69117, Baden-Württemberg, Germany.
Andreas
A
Geisbüsch
Department of Orthopaedic and Trauma Surgery, University Hospital Heidelberg, Schlierbacher Landstraße 200a, Heidelberg 69117, Baden-Württemberg, Germany.
Christoph
C
Auer
Department of Medical Biometrics and Computer Sciences, University Hospital Heidelberg, Heidelberg 69117, Baden-Württemberg, Germany.
Hartmut
H
Dickhaus
Department of Orthopaedic and Trauma Surgery, University Hospital Heidelberg, Schlierbacher Landstraße 200a, Heidelberg 69117, Baden-Württemberg, Germany.
Mirjam
M
Niklasch
Department of Orthopaedic and Trauma Surgery, University Hospital Heidelberg, Schlierbacher Landstraße 200a, Heidelberg 69117, Baden-Württemberg, Germany.
Thomas
T
Dreher
D000328:Adult; D053587:Arthrometry, Articular / Q000379:methods*; D002648:Child; D055590:Electromagnetic Phenomena; D005269:Femur / Q000601:surgery*; D006801:Humans; D010027:Osteotomy / Q000379:methods*
cerebral palsy; electromagnetic bone segment tracking; femoral derotation osteotomy; goniometer; pediatric orthopaedics