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J Orthop Res. 2018 Oct 22. doi: 10.1002/jor.24165. [Epub ahead of print]

Method for quantitative assessment of acetabular bone defects.

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Aesculap AG, Research & Development, Am Aesculap-Platz, 78532 Tuttlingen, Germany.
Ludwig-Maximilians-University Munich, Department of Orthopaedic Surgery, Physical Medicine & Rehabilitation, Campus Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany.
1000shapes GmbH, 12247 Berlin, Germany.
Department for Arthroplasty and General Orthopaedic Surgery, Orthopaedic Hospital Lindenlohe, Lindenlohe 18, 92421 Schwandorf, Germany.
Department of Orthopaedic Surgery, König-Ludwig-Haus, Julius-Maximilians-University Würzburg, Brettreichstraße 11, 97074 Würzburg, Germany.
University of Messina, Via Consolare Valeria 1, 98124 Messina, Italy.
Istituto Ortopedico Rizzoli, Via Giovanni Pupilli 1, 40136 Bologna, Italy.


The objective of the study was to suggest a novel quantitative assessment of acetabular bone defects based on a statistical shape model, validate the method, and present preliminary results. Two exemplary CT-data sets with acetabular bone defects were segmented to obtain a solid model of each defect pelvis. The pathological areas around the acetabulum were excluded and a statistical shape model was fitted to the remaining healthy bone structures. The excluded areas were extrapolated such that a solid model of the native pelvis per specimen resulted (i.e., each pelvis without defect). The validity of the reconstruction was tested by a leave-one-out study. Validation results showed median reconstruction errors of 3.0 mm for center of rotation, 1.7 mm for acetabulum diameter, 2.1° for inclination, 2.5° for anteversion, and 3.3 mm3 for bone volume around the acetabulum. By applying Boolean operations on the solid models of defect and native pelvis, bone loss and bone formation in four different sectors were assessed. For both analyzed specimens, bone loss and bone formation per sector were calculated and were consistent with the visual impression. In specimen_1 bone loss was predominant in the medial wall (10.8 ml; 79%), in specimen_2 in the posterior column (15.6 ml; 46%). This study showed the feasibility of a quantitative assessment of acetabular bone defects using a statistical shape model-based reconstruction method. Validation results showed acceptable reconstruction accuracy, also when less healthy bone remains. The method could potentially be used for implant development, pre-clinical testing, pre-operative planning, and intra-operative navigation. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 9999:1-9, 2018.


acetabular bone defects; quantification; statistical shape model; volume analysis


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