Controlling Femoral Derotation Osteotomy In Cerebral Palsy With Electromagnetic Tracking

The study is designed to evaluate the use of electromagnetic tracking in transversal plane femoral derotation osteotomies. The goal is to raise the precision of the surgical procedure in order to improve the outcome in short- and long term. All patients are examined with an instrumented 3D gait analysis pre- and one year postoperatively. The electromagnetic tracking system is evaluated against a base line CT or MRI scan serving as reference standard pre- and postoperatively.

Internal rotation gait is a common deformity in children, especially in those with spastic diplegia. The treatment includes soft tissue and bony correction. Especially the bony procedures e.g. femoral derotation osteotomies have proven to be effective both in short term and long term evaluation. Nonetheless there is still a relevant number of patients that suffer from over- or under-correction and recurrence over time. The reasons are diverse and include false measurement of the derotation in OR. The study now evaluates electromagnetic tracking for femoral derotation to improve these results. The patients are recruited from the outpatients department and included if they meet the criteria. A baseline rotational CT or MRI scan and a 3D gait analysis are performed preoperatively. The patients are randomized into a electromagnetic tracking group or a classical goniometer group. The derotation is measured with the EMT system or with a classic Moeltgen goniometer in the OR. Goal is to achieve the planned amount of derotation more accurately. The surgical procedure follows standard rules and does not need alterations because of the study. After the operation a second rotational CT or MRI scan is performed and the derotation precisely evaluated by two raters and later compared to the results of the intraoperative electromagnetic tracking system. One year postoperative a second 3D gait analysis is performed to measure and compare the functional and dynamic outcome.