Acetabular defect classification in times of 3D imaging and patient-specific treatment protocols

Abstract

Parallel to the rising number of revision hip procedures, an increasing number of complex periprosthetic osseous defects can be expected. Stable long-term fixation of the revision implant remains the ultimate goal of the surgical protocol. Within this context, an elaborate preoperative planning process including anticipation of the periacetabular defect form and size and analysis of the remaining supporting osseous elements are essential. However, detection and evaluation of periacetabular bone defects using an unsystematic analysis of plain anteroposterior radiographs of the pelvis is in many cases difficult. Therefore, periacetabular bone defect classification schemes such as the Paprosky system have been introduced that use standardized radiographic criteria to better anticipate the intraoperative reality. Recent studies were able to demonstrate that larger defects are often underestimated when using the Paprosky classification and that the intra- and interobserver reliability of the system is low. This makes it hard to compare results in terms of defects being studied. Novel software tools that are based on the analysis of CT data may provide an opportunity to overcome the limitations of native radiographic defect analysis. In the following article we discuss potential benefits of these novel instruments against the background of the obvious limitations of the currently used native radiographic defect analysis.

Method for quantitative assessment of acetabular bone defects

“…The defined sectors were cranial roof, anterior column, posterior column, and medial wall (Fig. A), which were inspired by previous studies . In order to consider patient‐specific anatomy, the sectors were constructed on the acetabular plane, aligned to the patient coordinate system, and scaled in relation to the acetabulum diameter (Fig.…”

“…The reliability increases when using three‐dimensional (3D) computer tomography (CT) scans instead of 2D radiographs, but there still remains a bias related to subjective interpretation . Furthermore, the current classification schemes are mainly descriptive and hence it remains difficult to transfer them into pre‐clinical testing, implant development, and to anticipate the exact amount of bone loss in pre‐operative planning . Novel imaging techniques allow a 3D presentation of individual bone structures, but an objective and quantitative method to assess the bone defects is still not available.…”

“…A SSM can be altered via a unique set of parameters to reconstruct the native pelvis (i.e., the pelvis without bone defect) on the basis of a defect pelvis (i.e., the pelvis with bone defect). Recently published studies showed the feasibility to estimate the native pelvis anatomy using a SSM and thereby allow a novel view on defect classification . Among the estimation of bone loss, also bone formation due to remodeling processes could be identified when comparing the defect pelvis with the native pelvis .…”

“…Recently published studies showed the feasibility to estimate the native pelvis anatomy using a SSM and thereby allow a novel view on defect classification. 9,14,15 Among the estimation of bone loss, also bone formation due to remodeling processes could be identified when comparing the defect pelvis with the native pelvis.…”

A New Diagnostic Approach for Periprosthetic Acetabular Fractures Based on 3D Modeling: A Study Protocol

“…3D modeling allows of creating a 3D representation of surfaces or objects from a 2D slice images, such as CT and MRI scans. In case of periprosthetic acetabular fractures, 3D modeling medical software allows us to obtain precise tridimensional reconstructions of the bony surface, virtually removing the metallic implants trough image segmentation [8]. Additional tools consent to analyze the fracture extension, volumetric measurement of the remaining bone stock and the evaluation of implant bone interface [9].…”