Tibial bone defect prediction based on preoperative artefact‐reduced CT imaging is superior to standard radiograph assessment

Abstract

Purpose The purpose of this study was to evaluate the accuracy of preoperative CT-based Anderson Orthopaedic Research Institute (AORI)-grading and to correlate Computed tomography (CT)-based volumetric defect measurements with intraoperative AORI findings. Methods 99 patients undergoing revision total knee arthroplasty (rTKA) with preoperative CT-images were identified in an institutional revision registry. CT-image segmentation with 3D-Slicer Software was used to create 3D tibial bone defects which were then graded according to the AORI-classification. The AORI classification categorizes tibial defects into three types: Type I has healthy cortical and cancellous bone near the joint line, Type II involves metaphyseal bone loss affecting one or both condyles, and Type III indicates deficient metaphyseal bone with distal defects and potential damage to the patellar tendon and collateral ligament attachments. These 3D-CT gradings were compared to preoperative X-ray and intraoperative AORI grading. The Friedman test was used to investigate differences between AORI values of each measurement method. Volumetric 3D-bone defect measurements were used to investigate the relationship between AORI classification and volumetric defect size in the three anatomic zones of the tibia. Results Substantial agreements between preoperative 3D-CT AORI and intraoperative AORI (kappa = 0.663; P < 0.01) and fair agreements between preoperative X-ray AORI and intraoperative AORI grading (kappa = 0.304; P < 0.01) were found. Moderate correlations between volume of remaining bone and intraoperative AORI grading were found in epiphysis (rS = – 0.529; P < 0.001), metaphysis (rS = – 0.557; P < 0.001) and diaphysis (rS = – 0.421; P < 0.001). Small volumetric differences between AORI I vs. AORI II defects and relatively large differences between AORI II and AORI III defects in each zone were detected. Conclusion Tibial bone defect prediction based on preoperative 3D-CT segmentation showed a substantial agreement with intraoperative findings and is superior to standard radiograph assessment. The relatively small difference in defect volume between AORI I, IIa and IIb suggests that updated CT-based classifications might hold benefits for the planning of rTKA. Level of evidence Retrospective Cohort Study; III

Imaging in revision total knee arthroplasty: A novel 3D classification system for tibial bone defects

“…This should be considered especially in younger patients, as the likelihood of radiation-induced malignancy is a function of the patients' age [23]. Nevertheless, previous studies reported a low sensitivity of X-ray in detecting osteolytic lesions around TKA implants (0% small defects [mean 0.7 cm³] -66% large defects [mean 3.5 cm³]) and only fair agreements between preoperative X-ray assessments and intraoperative grading (κ value of 0.304), highlighting the need for improvement of preoperative assessment [4,10,14]. This indicates that while X-rays may offer some preliminary insights, CT scans and the 3D-segmentations are more precise and offer the potential to assist in predicting the sizes of cones and sleeves that may be required.…”

“…In addition, the ratio of remaining tibial bone volume (bone volume minus total defect) to the total tibial bone was computed to allow comparison across bones of different sizes. This 3D segmentation method used in the current paper has been validated by comparing CT defect measurements to intraoperative surgeon assessment [10].…”

“…Improvements in computer tomography (CT) technology with reduced beam hardening allows three-dimensional (3D) reconstruction of remaining bone around TKA to be performed. In this context, it has already been demonstrated that preoperative CT imaging improves the prediction of intraoperative bone defects [10]. Defect volumes and defect location within the tibia can now be determined more precisely [11][12][13].…”