Weight-bearing cone-beam CT: the need for standardised acquisition protocols and measurements to fulfill high expectations-a review of the literature

Utility of Weight-Bearing Computed Tomography in the Postoperative Assessment of Ankle Fractures

Background: Ankle fractures are among the most common injuries requiring surgical intervention. Standard radiographs are typically used for postoperative assessment; however, some patients continue to experience residual symptoms despite satisfactory radiographic outcomes. Weight-bearing computed tomography (WBCT), though not yet widely integrated into clinical practice, offers potential advantages in evaluating lower-limb deformities, injuries, and arthritis. This study explores the utility of WBCT for the midterm assessment following ankle fracture fixation and compares its findings with those obtained from standard radiographs. Methods: In this retrospective case study, we analyzed the correlations between the functional outcome scores approximately one year post-surgery and parameters assessed using WBCT. Pearson's correlation coefficient was used to evaluate these correlations, and a t-test was performed to assess their statistical significance, with a threshold p-value of 0.05. Additionally, Spearman's rank correlation coefficient was calculated as a supplementary descriptive measure, without significance testing. These correlations were then compared with those obtained from standard ankle radiographic views (anteroposterior, lateral, and mortise). Results: Several correlations were identified between WBCT parameters and functional scales, with certain parameters demonstrating high statistical significance (p < 0.05). Overall, the correlations observed for WBCT were stronger than those for standard radiographs. Conclusions: Although the study cohort was limited, the findings suggest that WBCT may provide additional insights beyond conventional radiography. Further research with larger patient groups is needed to establish its clinical relevance.

Inducible displacement of cementless total knee arthroplasty components with conventional and weight-bearing CT-based radiostereometric analysis

Aseptic loosening remains one of the top causes of revision surgery of total knee arthroplasty (TKA). Radiostereometric analysis (RSA) is used in research to measure implant migration, however limitations prevent its clinical use. New methods have allowed the same measurements as RSA to be performed with computed tomography (CT) scanners (CT-RSA). The objective of this study is to determine inducible displacement measurements from weight-bearing computed tomography (WBCT) and conventional RSA to assess implant stability. Participants (n = 17) completed RSA exams in the supine and standing position, and WBCT exams in the seated (leg extended) and standing position. Double examinations were performed in the seated (WBCT) or supine (RSA) positions. Inducible displacements were measured with model-based RSA (MBRSA) for RSA exams, and a novel CT-RSA software, V3MA, for WBCT exams. Precision of each technique was calculated between double examinations. Precision data for tibial component total translations and rotations were 0.05 mm and 0.118°, respectively with WBCT-RSA, and were 0.108 mm and 0.269°, respectively with MBRSA. MTPM precision was 0.141 mm with WBCT-RSA and was 0.168 mm with MBRSA. Inducible displacement MTPM of the tibial component was 0.244 ± 0.220 mm with WBCT-RSA and 0.662 ± 0.257 mm with MBRSA. Inducible displacement measurements with MBRSA were significantly different from WBCT-RSA for tibial component anterior tilt (p = 0.0002). WBCT-RSA demonstrated comparable precision to MBRSA, and both techniques measured inducible displacements consistent with stable components. Clinical Significance: As the availability of WBCT increases, its use as an alternative to MBRSA is supported to measure the instantaneous fixation of implant components.

Radiologic evaluation of ankle fracture malunions of the fibula

Ankle fractures involving the distal fibula are common injuries. Malreductions and subsequent malunions of the distal fibula can result in worse clinical outcomes and posttraumatic arthritis. The ability to accurately evaluate and identify malreductions and malunions of the distal fibula is important. A number of different radiographic and CT measurements have been described to assess fibular length and rotation. This review highlights various radiologic measures and discusses their advantages and limitations.

Trends in the Use of Weightbearing Computed Tomography

Background: This review aimed to critically appraise the most recent orthopedic literature around cone beam weightbearing computed tomography (WBCT), summarizing what evidence has been provided so far and identifying the main research trends in the area. Methods: This scoping review was performed on studies published between January 2013 and December 2023 on the Pubmed database. All studies (both clinical and nonclinical) in which WBCT had been used were critically analyzed to extract the aim (or aims) of the study, and the main findings related to the role of this imaging modality in the diagnostic pathway. Results: Out of 1759 studies, 129 were selected. One hundred five manuscripts (81%) dealt with elective orthopedic conditions. The majority of the analyses (88 studies; 84%) were performed on foot and ankle conditions, while 13 (12%) studies looked at knee pathologies. There was a progressive increase in the number of studies published over the years. Progressive Collapsing Foot Deformity (22 studies; 25%) and Hallux Valgus (19 studies; 21%) were frequent subjects. Twenty-four (19%) manuscripts dealt with traumatic conditions. A particular interest in syndesmotic injuries was documented (12 studies; 60%). Conclusions: In this review, we documented an increasing interest in clinical applications of weightbearing CT in the orthopedic field between 2013 and 2023. The majority of the analyses focused on conditions related to the foot and the ankle; however, we found several works investigating the value of WBCT on other joints (in particular, the knee).

Morphological changes in flatfoot: a 3D analysis using weight-bearing CT scans

BACKGROUND

Flatfoot is a condition resulting from complex three-dimensional (3D) morphological changes. Most Previous studies have been constrained by using two-dimensional radiographs and non-weight-bearing conditions. The deformity in flatfoot is associated with the 3D morphology of the bone. These morphological changes affect the force line conduction of the hindfoot/midfoot/forefoot, leading to further morphological alterations. Given that a two-dimensional plane axis overlooks the 3D structural information, it is essential to measure the 3D model of the entire foot in conjunction with the definition under the standing position. This study aims to analyze the morphological changes in flatfoot using 3D measurements from weight-bearing CT (WBCT).

METHOD

In this retrospective comparative our CT database was searched between 4-2021 and 3-2022. Following inclusion criteria were used: Patients were required to exhibit clinical symptoms suggestive of flatfoot, including painful swelling of the medial plantar area or abnormal gait, corroborated by clinical examination and confirmatory radiological findings on CT or MRI. Healthy participants were required to be free of any foot diseases or conditions affecting lower limb movement. After applying the exclusion criteria (Flatfoot with other foot diseases), CT scans (mean age = 20.9375, SD = 16.1) confirmed eligible for further analysis. The distance, angle in sagittal/transverse/coronal planes, and volume of the two groups were compared on reconstructed 3D models using the t-test. Logistic regression was used to identify flatfoot risk factors, which were then analyzed using receiver operating characteristic curves and nomogram.

RESULT

The flatfoot group exhibited significantly lower values for calcaneofibular distance (p = 0.001), sagittal and transverse calcaneal inclination angle (p < 0.001), medial column height (p < 0.001), sagittal talonavicular coverage angle (p < 0.001), and sagittal (p < 0.001) and transverse (p = 0.015) Hibb angle. In contrast, the sagittal lateral talocalcaneal angle (p = 0.013), sagittal (p < 0.001) and transverse (p = 0.004) talocalcaneal angle, transverse talonavicular coverage angle (p < 0.001), coronal Hibb angle (p < 0.001), and sagittal (p < 0.001) and transverse (p = 0.001) Meary's angle were significantly higher in the flatfoot group. The sagittal Hibb angle (B =  - 0.379, OR = 0.684) and medial column height (B =  - 0.990, OR = 0.372) were identified as significant risk factors for acquiring a flatfoot.

CONCLUSION

The findings validate the 3D spatial position alterations in flatfoot. These include the abduction of the forefoot and prolapse of the first metatarsal proximal, the arch collapsed, subluxation of the talonavicular joint in the midfoot, adduction and valgus of the calcaneus, adduction and plantar ward movement of the talus in the hindfoot, along with the first metatarsal's abduction and dorsiflexion in the forefoot.

Cone-beam computed tomography imaging and three-dimensional analysis of midfoot joints during non-weightbearing and weightbearing in 11 healthy feet

BACKGROUND

Studies report that Lisfranc injury is more common than thought. Several imaging methods for assessing the stability of Lisfranc injury have been described but many are impossible to standardize and not accurate enough.

PURPOSE

To present a three-dimensional (3D) method for analyzing the changes in the joint space width of the midfoot joint and the joints of the medial part of the Lisfranc complex in healthy individuals.

MATERIAL AND METHODS

Non-weightbearing and weightbearing cone-beam computed tomography (CBCT) images of 11 healthy feet were acquired and analyzed with 3D software. The mean range of joint space width changes of each joint was computed from the changes in individual image pairs.

RESULTS

3D analysis software was used to analyze the medial part of the Lisfranc complex. In this sample of healthy feet, the changes in the joint spaces in the medial part of Lisfranc complex, calculated with 3D analysis software, was less than 0.6 mm. The distance between bones increased or decreased, depending on which part of the joint surface the measurements were taken.

CONCLUSION

In this study, we present a 3D analysis method to evaluate midfoot joint space width changes. Our analysis revealed that in healthy feet there are only minimal changes in the joint space width between weightbearing and non-weightbearing indicating minimal movement of the midtarsal joints. The 3D analysis of weightbearing CBCT data provides a promising tool for analyzing the small midfoot joints in a variety of conditions.

Cone-Beam CT of the Extremities in Clinical Practice

Cone-beam CT (CBCT) is a promising tool with increasing applications in musculoskeletal imaging due to its ability to provide thin-section CT images of the appendicular skeleton and introduce weight bearing, which accounts for loading forces that typically interact with and affect this anatomy. CBCT devices include an x-ray source directly opposite a digital silicon detector panel that performs a single rotation around an object of interest, obtaining thin-section images. Currently, the majority of research has been focused on the utility of CBCT with foot and ankle pathologic abnormalities, due to the complex architectural arrangement of the tarsal bones and weight-bearing nature of the lower extremities. Associated software can provide a variety of options for image reconstruction, including metal artifact reduction, three-dimensional biometric measurements, and digitally reconstructed radiographs. Advancements in this technology have allowed imaging of the knee, hip, hand, and elbow. As more data are published, it is becoming evident that CBCT provides many additional benefits, including fast imaging time, low radiation dose, lower cost, and small equipment footprint. These benefits allow placement of CBCT units outside of the traditional radiology department, including the orthopedic clinic setting. These technologic developments have motivated clinicians to define the scope of CBCT for diagnostics, surgical planning, and longitudinal imaging. As efforts are made to create standardized protocol and measurements, the current understanding and surgical approach for various orthopedic pathologic conditions will continue to shift, with the hope of improving outcomes. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Quantitative Skeletal Imaging and Image-Based Modeling in Pediatric Orthopaedics

PURPOSE OF REVIEW

Musculoskeletal imaging serves a critical role in clinical care and orthopaedic research. Image-based modeling is also gaining traction as a useful tool in understanding skeletal morphology and mechanics. However, there are fewer studies on advanced imaging and modeling in pediatric populations. The purpose of this review is to provide an overview of recent literature on skeletal imaging modalities and modeling techniques with a special emphasis on current and future uses in pediatric research and clinical care.

RECENT FINDINGS

While many principles of imaging and 3D modeling are relevant across the lifespan, there are special considerations for pediatric musculoskeletal imaging and fewer studies of 3D skeletal modeling in pediatric populations. Improved understanding of bone morphology and growth during childhood in healthy and pathologic patients may provide new insight into the pathophysiology of pediatric-onset skeletal diseases and the biomechanics of bone development. Clinical translation of 3D modeling tools developed in orthopaedic research is limited by the requirement for manual image segmentation and the resources needed for segmentation, modeling, and analysis. This paper highlights the current and future uses of common musculoskeletal imaging modalities and 3D modeling techniques in pediatric orthopaedic clinical care and research.

Current Trends in Total Ankle Replacement

Ankle arthritis can result in significant pain and restriction in range of motion. Total ankle replacement (TAR) is a motion-preserving surgical option used as an alternative to total ankle arthrodesis to treat end-stage ankle arthritis. There are several generations of TAR techniques based on component design, implant material, and surgical technique. With more recent TAR implants, an attempt is made to minimize bone resection and mirror the native anatomy. There are more than 20 implant devices currently available. Implant survivorship varies among prosthesis types and generations, with improved outcomes reported with use of the more recent third- and fourth-generation ankle implants. Pre- and postoperative assessments of TAR are primarily performed by using weight-bearing radiography, with weight-bearing CT emerging as an additional imaging tool. Preoperative assessments include those of the tibiotalar angle, offset, and adjacent areas of arthritis requiring additional surgical procedures. US, nuclear medicine studies, and MRI can be used to troubleshoot complications. Effective radiologic assessment requires an understanding of the component design and corresponding normal perioperative imaging features of ankle implants, as well as recognition of common and device-specific complications. General complications seen at radiography include aseptic loosening, osteolysis, hardware subsidence, periprosthetic fracture, infection, gutter impingement, heterotopic ossification, and syndesmotic nonunion. The authors review several recent generations of TAR implants commonly used in the United States, normal pre- and postoperative imaging assessment, and imaging complications of TAR. Indications for advanced imaging of TAR are also reviewed. ©RSNA, 2023 Supplemental material is available for this article. Test Your Knowledge questions for this article are available through the Online Learning Center.

Diagnostic applications and benefits of weightbearing CT in the foot and ankle: A systematic review of clinical studies

BACKGROUND

Foot and ankle weightbearing CT (WBCT) imaging has emerged over the past decade. However, a systematic review of diagnostic applications has not been conducted so far.

METHOD

A systematic literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines after Prospective Register of Systematic Reviews (PROSPERO) registration. Studies analyzing diagnostic applications of WBCT were included. Main exclusion criteria were: cadaveric specimens and simulated WBCT. The Methodological Index for Non-Randomized Studies (MINORS) was used for quality assessment.

RESULTS

A total of 78 studies were eligible for review. Diagnostic applications were identified in following anatomical area's: ankle (n = 14); hindfoot (n = 41); midfoot (n = 4); forefoot (n = 19). Diagnostic applications that could not be used on weightbearing radiographs (WBRX) were reported in 56/78 studies. The mean MINORS was 9.8/24 (range: 8-12).

CONCLUSION

Diagnostic applications of WBCT were most frequent in the hindfoot, but other areas are on the rise. Post-processing of images was the main benefit compared to WBRX based on a moderate quality of the identified studies.

3-D joint space mapping at the ankle from weight-bearing CT: reproducibility, repeatability, and challenges for standardisation

OBJECTIVES

We present a 3-D approach to joint space width (JSW) measurement across the ankle from weight-bearing CT (WBCT) to demonstrate inter-operator reproducibility, test-retest repeatability, and how differences in angulation affect ankle JSW distribution.

METHODS

One side from repeat WBCT imaging of both feet and ankles was analysed from 23 individuals as part of their routine clinical care pathway. Joint space mapping was performed at four facets across the talus: talonavicular, talar dome and medial gutter (dome-medial), lateral gutter, and posterior subtalar. Inter-operator reproducibility was calculated for two users, while test-retest repeatability was calculated by comparing the two visits, both presented as Bland-Altman statistics. Statistical parametric mapping determined any significant relationships between talocrural joint space angulation and 3-D JSW distribution.

RESULTS

The average ± standard deviation interval between imaging was 74.0 ± 29.6 days. Surface averaged bias ± limits of agreement were similar for reproducibility and repeatability, the latter being: talonavicular 0.01 ± 0.26 mm, dome-medial 0.00 ± 0.28 mm, lateral gutter - 0.02 ± 0.40 mm, and posterior subtalar 0.02 ± 0.34 mm. Results are presented as 3-D distribution maps, with optimum test-retest repeatability reaching a smallest detectable difference of ± 0.15 mm.

CONCLUSIONS

Joint space mapping is a robust approach to 3-D quantification of JSW measurement, inter-operator reproducibility, and test-retest repeatability at the ankle, with sensitivity reaching a best value of ± 0.15 mm. Standardised imaging protocols and optimised metal artefact reduction will be needed to further understand the clinical value of these 3-D measures derived from WBCT.

CLINICAL RELEVANCE STATEMENT

Weight-bearing computed tomography is an increasingly important tool in the clinical assessment of orthopaedic ankle disorders. This paper establishes the performance of measuring 3-D joint space width using this technology, which is an important surrogate marker for severity of osteoarthritis.

KEY POINTS

• Joint space width values and error metrics from across the ankle measured from weight-bearing CT can be presented as 3-D maps that show topographic variation. • The best sensitivity for detecting meaningful change in 3-D joint space width at the ankle was ± 0.15 mm, a value less than the isotropic imaging voxel dimensions. • Standardised imaging protocols and optimised metal artefact reduction will be needed to understand the clinical value of 3-D measures from weight-bearing CT.