A robust method for automatic identification of femoral landmarks, axes, planes and bone coordinate systems using surface models

Abstract

The identification of femoral landmarks is a common procedure in multiple academic fields. Femoral bone coordinate systems are used particularly in orthopedics and biomechanics, and are defined by landmarks, axes and planes. A fully automatic detection overcomes the drawbacks of a labor-intensive manual identification. In this paper, a new automatic atlas- and a priori knowledge-based approach that processes femoral surface models, called the A&A method, was evaluated. The A&A method is divided in two stages. Firstly, a single atlas-based registration maps landmarks and areas from a template surface to the subject. In the second stage, landmarks, axes and planes that are used to construct several femoral bone coordinate systems are refined using a priori knowledge. Three common femoral coordinate systems are defined by the landmarks detected. The A&A method proved to be very robust against a variation of the spatial alignment of the surface models. The results of the A&A method and a manual identification were compared. No significant rotational differences existed for the bone coordinate system recommended by the International Society of Biomechanics. Minor significant differences of maximally 0.5° were observed for the two other coordinate systems. This might be clinically irrelevant, depending on the context of use and should, therefore, be evaluated by the potential user regarding the specific application. The entire source code of the A&A method and the data used in the study is open source and can be accessed via https://github.com/RWTHmediTEC/FemoralCoordinateSystem.

Implications of the uncertainty of postoperative functional parameters for the preoperative planning of total hip arthroplasty

“…Bone coordinate systems were calculated using automated methods introduced by Fischer et al 23 to define the neutral position of the bones. The pelvic coordinate system is based on the anterior pelvic plane (APP) 23 and the femoral coordinate system on the table top plane and the mechanical axis 24 . The components of the implant were reconstructed from the postoperative CT scans.…”

“…The well‐documented TLEM2.0 cadaver served as the underlying cadaver template that was individually scaled to the patient's anatomy using landmark‐deformable bone surfaces 25 . Most of the landmarks were detected on the patient's surface models of the bones using automated methods 23,24 . The automatically detected landmarks were reviewed and additional landmarks were manually identified by an experienced expert.…”

“…25 Most of the landmarks were detected on the patient's surface models of the bones using automated methods. 23,24 The automatically detected landmarks were reviewed and additional landmarks were manually identified by an experienced expert. The positions of the femur and pelvis relative to the hip joint center were based on the reconstructed postoperative anatomy of the patient.…”

The Patient-Specific Combined Target Zone for Morpho-Functional Planning of Total Hip Arthroplasty

“…The pelvic landmarks and coordinate system were automatically identified using the ITP method [ 70 ]. The landmarks required for the calculation of the femoral coordinate system were detected using the A&A method [ 71 ]. The automatically detected landmarks were reviewed and additional landmarks were manually identified by one experienced expert.…”

Detection of Pediatric Femur Configuration on X-ray Images

“…The femur coordinate system proposed in this study was not incorporated in any outgoing or previous studies. Other authors proposed different representations [35,36], but those do not apply for this specific image data. As far as the author's knowledge is concerned, there are no alternative configuration detectors of the pediatric femur bone in the lateral view.…”