Computer assistance in femoral derotation osteotomy: a bottom-up approach

Abstract

Severe gait abnormalities in patients with cerebral palsy are often treated by correction osteotomy. The established procedure of femoral derotation osteotomy (FDO) has proven effective to realign femur anteversion. Nevertheless, studies have revealed that therapy outcome is subject to substantial inter-patient variability and systematic loss of correction. Our previous work suggests that practical limitations in FDO may significantly contribute to this effect. In this work, we propose a novel computer assisted measurement system to support FDO with objective measurement (desired accuracy: ∼ ± 3°) and continuous monitoring of derotation. A prototype system based on the clinically emerging electromagnetic tracking technology is demonstrated which incorporates technical and operational considerations to enable continuous measurement in OR conditions while preserving the conventional workflow without disruptions. In phantom studies, the achieved measurement accuracy (standard error ≅±1.6)∘$\cong\pm 1.6{}^{\circ})$ proved high potential and may hugely benefit the quality of surgical execution. Currently, the prototype system is assessed under OR conditions in an in-vivo study with CP patients. Early experience shows high appreciation among surgeons and good potential for future application.

Keywords

• computer assisted surgery
• electromagnetic tracking
• femoral correction
• therapy monitoring