Computer-based periaxial rotation measurement for aligning fractured femur
fragments from ct: a feasibility study

Ofer Ron (1), Leo Joskowicz (1), Charles Milgrom (2), Ariel Simkin (2)


(1) School of Computer Science and Engineering The Hebrew University of
    Jerusalem, Jerusalem, Israel.

(2) Department of Orthopaedic Surgery Hadassah University Hospital,
    Jerusalem, Israel.


Abstract

A new computer-based method for periaxial rotation measurement of healthy
and fractured femurs during closed femoral fracture reduction surgery from
preoperative CT is described.  The method provides a comparative
quantitative measure to align the distal and proximal femur fragments based
on periaxial rotation.  The periaxial rotation is defined in terms of
patient-specific bone features. An algorithm for automatically extracting
these features from the CT based on this definition is developed.  The
algorithm extracts condyle landmarks and neck axis of the healthy bone,
determines its periaxial rotation, and extrapolates this data, assuming
mirror symmetry between the healthy and the fractured bone, to measure
periaxial rotation between the fractured fragments.  Unlike existing
techniques, method requires minimal user intervention.  In a feasibility
study, the method was applied to five dry femurs and one patient data set
and simulated a reduction based on the periaxial measurements with
satisfactory results.  The experiments showed the measured angle on the
fractured femur to be within 1-4.5 degrees of that of the healthy bone.

Keywords: computer-aided orthopaedic surgery, femoral fracture reduction,
periaxial rotation measurement.


Published in: Computer-Aided Surgery, Vol. 7(6), 2002, pp 332-341.