CT in osteoarthritis: its clinical role and recent advances.

Computed tomography (CT) is a widely available imaging method and considered as one of the most reliable techniques in bone assessment. Although CT has limited tissue contrast and needs radiation exposure, it has several advantages like fast scanning time and high spatial resolution. In this regard, CT has unique roles in osteoarthritis (OA) and its variable utilities have been reported. Hence, this review highlights the clinical role of CT in OA of representative joints. In addition, CT showed the several technical advancements recently, for example, acquiring the CT image with standing, obtaining the dual-energy data, and novel photon-counting detector development. Therefore, the recent studies and potential utility of these new CT systems in OA are also discussed.

Impact of posterior femoral condylar cartilage and posterior intercondylar distance on rotation of femoral component in total knee arthroplasty.

BACKGROUND: Greater accuracy is needed when determining the final femoral component (FC) rotation during total knee arthroplasty (TKA), because this parameter affects soft tissue balance during flexion and patellar tracking. Anatomical markers, such as the epicondylar axis, are typically used to determine the final FC rotation, although intraoperative confirmation may be challenging. Therefore, rotational position is frequently determined with the posterior condylar axis (PCA) as a landmark. However, the thickness of the posterior condylar cartilage has not been considered and may not be represented on preoperative images. We used plain X-rays to measure the thickness of the medial and lateral posterior condylar cartilage fragments postoperatively, and investigated the effects of differences in cartilage thickness on final FC rotation. METHODS: Fifty knees (19 men, 31 women) underwent primary TKA to treat medial knee osteoarthritis at our hospital between August 2015 and May 2017. All knees were treated using an Attune PS (DePuy Synthes, Inc., Warsaw, IN). We first measured the distance between the posterior femoral condyles, resected the posterior condyle, and measured the thickness of the resected cartilage fragments. We then took X-ray images from a direction tangential to the osteotomy surface, secured the cartilage fragments with digital calipers, and measured the thickness of the cartilage. We investigated the effects of differences in cartilage thickness on final FC rotation of the residual medial and lateral cartilage with a trigonometric function. RESULTS: Medial condylar cartilage thickness averaged 0.6 ± 0.5 mm and the lateral condylar thickness averaged 1.8 ± 0.6 mm; posterior intercondylar distance averaged 46.1 ± 3.3 mm and average impact on rotation of the cartilage remnant was 1.5 ± 0.9° (- 0.1-3.9°). There may be measurement error of up to 4° in the maximum values compared with the preoperative plan in cases with short intercondylar distance. CONCLUSIONS: In cases where the FC external rotation angle is determined using the posterior condyles as landmarks, this angle can be affected by the intercondylar distance, especially in Japanese women who have small physical stature. This angle can potentially be much larger, so caution is advised. Our results suggest that several anatomical landmarks should be referenced to achieve accurate FC rotation.

Accuracy of Computed Tomography-Based Navigation-Assisted Total Knee Arthroplasty: Outlier Analysis.

BACKGROUND: Achieving neutral limb alignment during total knee arthroplasty (TKA) has been identified as a potential factor in long-term prosthesis survival. This study aimed to analyze the accuracy of component orientation and postoperative alignment of the leg after computed tomography (CT)-based navigation-assisted TKA, compare these parameters with those of a conventional technique, and analyze differences in the data of outliers. METHODS: We retrospectively compared the alignment of 130 TKAs performed with a CT-based navigation system with that of 67 arthroplasties done with a conventional system. The knee joints were evaluated using radiographs. RESULTS: Mean hip-knee-ankle (HKA) angle, frontal femoral component angle, and frontal tibial component angle were 180.7°, 88.8°, and 90.6°, respectively, for the navigation-assisted arthroplasties and 181.1°, 88.7°, and 90.2°, respectively, for the conventional arthroplasties. All preoperative leg axes of 10 outliers in the navigation group were >193°, whereas the data of 17 outliers in the conventional group were scattered. CONCLUSION: This study demonstrates significant improvements in component positioning with the CT-based navigation system. Furthermore, when analyzing cases with preoperative HKA angles ≤192°, no outliers were found in the navigation group, indicating high alignment accuracy. However, in cases with preoperative HKA angles ≥193°, outliers were found in both groups, and no significant difference between the groups was observed (P = .08). Detailed analysis of the outlier cases in the navigation group revealed that the femoral component was placed in the varus position. These findings indicate that the varus knee is an important factor influencing accurate positioning of the femoral component and the postoperative leg axis.