Weight-bearing CT in foot and ankle pathology

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.

Enhancing precision in osteochondral lesions of the talus measurements and improving agreement in surgical decision-making using weight-bearing computed tomography and distance mapping

PURPOSE

Weight-bearing computed tomography (WBCT) enables the creation of a three-dimensional (3D) model that represents the ankle morphology in a standing position. Distance mapping (DM) is a complementary feature that uses color coding to represent the relative intraarticular distance and can be used to outline intraarticular defects. Consequently, DM offers a novel approach to delineating osteochondral lesions of the talus (OLT), allowing for the quantification of its surface, volume and depth. The reliability of DM for OLT measurements has yet to be thoroughly evaluated. This study primarily aims to determine the reliability of DM in measuring the surface, depth and volume of OLT. A secondary objective is to ascertain whether measurements obtained through DM, when integrated with a predefined treatment algorithm, can facilitate consensus among surgeons regarding the optimal surgical intervention.

METHODS

This cohort comprised 36 patients with 40 OLTs evaluated using WBCT and DM. Two raters used DM to determine the lesion boundary (LB) and lesion fundus (LF) and calculate the lesion depth, surface and volume. The raters were asked to choose between bone marrow stimulation, autologous matrix-induced chondrogenesis and osteochondral transposition based on the measurement. Inter-rater and intra-rater agreement was measured.

RESULTS

Interclass correlation of the lesion's depth surface produced an excellent inter-rater and intra-rater agreement of 0.90-0.94 p < 0.001. Cohen's κ agreement analysis of the preferable preoperative plan produced a κ = 0.834, p < 0.001, indicating a near-perfect agreement.

CONCLUSION

WBCT-based 3D modules and DM can be used to measure the lesion's surface, depth and volume with excellent inter-rater and inter-rater agreement; using this measurement and a predetermined treatment algorithm, a near-perfect inter-rater agreement for the preoperative planning was reached. WBCT in conjunction with AI capabilities could help determine the type of surgery needed preoperatively, evaluate the hindfoot alignment and assess if additional surgeries are needed.

LEVEL OF EVIDENCE

Level III.

A finite element model of human hindfoot and its application in supramalleolar osteotomy

BACKGROUND

The majority of the ankle osteoarthritis cases are posttraumatic and affect younger patients with a longer projected life span. Hence, joint-preserving surgery, such as supramalleolar osteotomy becomes popular among young patients, especially those with asymmetric arthritis due to alignment deformities. However, there is a lack of biomechanical studies on postoperative evaluation of stress at ankle joints. We aimed to construct a verifiable finite element model of the human hindfoot, and to explore the effect of different osteotomy parameters on the treatment of varus ankle arthritis.

METHODS

The bones of the hindfoot are reconstructed using normal CT tomography data from healthy volunteers, while the cartilages and ligaments are determined from the literature. The finite element calculation results are compared with the weight-bearing CT (WBCT) data to validate the model. By setting different model parameters, such as the osteotomy height (L) and the osteotomy distraction distance (h), the effects of different surgical parameters on the contact stress of the ankle joint surface are compared.

FINDINGS

The alignment and the deformation of hindfoot bones as determined by the finite element analysis aligns closely with the data obtained from WBCT. The maximum contact stress of the ankle joint surface calculated by this model increases with the increase of the varus angle. The maximum contact stresses as a function of the L and h of the ankle joint surface are determined.

INTERPRETATION

The relationship between surgical parameters and stress at the ankle joint in our study could further help guiding the planning of the supramalleolar osteotomy according to the varus/valgus alignment of the patients.

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.

Metatarsophalangeal and interphalangeal joint angle measurements on weight-bearing CT images

BACKGROUND

The aim of this study was to present and evaluate methods of measuring toe joint angels using joint-surface based and inertial axes approaches.

METHODS

Nine scans of one frozen human cadaveric foot were obtained using weight-bearing CT. Two observers independently segmented bones in the forefoot and measured metatarsalphalangeal joint (MTPJ) angles, proximal and distal interphalangeal joint (PIPJ and DIPJ) angles and interphalangeal angles of the hallux (IPJ) using 1) inertial axes, representing the long anatomical axes, of the bones and 2) axes determined using centroids of articular joint surfaces.

RESULTS

The standard deviations (SD) of the IPJ/PIPJ and DIPJ angles were lower using joint-surface based axes (between 1.5˚ and 4.1˚) than when the inertial axes method was used (between 3.3˚ and 16.4˚), for MTPJ the SD's were similar for both methods (between 0.5˚ and 2.6˚). For the IPJ/PIPJ and DIPJ angles, the width of the 95% CI and the range were also lower using the joint-surface axes method (95% CI: 2.0˚-4.1˚ vs 3.2˚-16.3˚; range: 3.1˚-7.4˚ vs 3.8˚-35.8˚). Intra-class correlation coefficients (ICC) representing inter- and intra-rater reliability were good to excellent regarding the MTPJ and IPJ/PIPJ angles in both techniques (between 0.85 and 0.99). For DIPJ angles, ICC's were good for the inertial axes method (0.78 and 0.79) and moderate for the joint-surface axes method (0.60 and 0.70).

CONCLUSION

The joint-surface axes method enables reliable and reproducible measurements of MTPJ, IPJ/PIPJ and DIPJ angles. For PIPJ and DIPJ angles this method is preferable over the use of inertial axes.

Weight-Bearing CT with Maximum Ankle Dorsiflexion to Identify Impingement and Tibial Plafond Stress Fracture: A Case Report

CASE

A 25-year-old male pole vaulter presented with several months of right ankle pain. Radiographs showed an anterior tibial osteophyte with a small intra-articular body suggesting impingement. Weight-bearing computed tomography (CT) revealed an associated tibial plafond stress fracture. Subsequent arthroscopy with osteophyte resection and loose body removal significantly improved symptoms, and he gradually resumed training.

CONCLUSION

Stress fractures should always be considered in athletes with ankle pain. A unique aspect of this case was the use of weight-bearing CT in diagnosis and surgical planning. To our knowledge, this is the first described case in which weight-bearing CT was used in this fashion.

The feasibility study of stress position device simulating standing weight-bearing applied in computed tomography examination

BACKGROUND

In order to simulate weight-bearing Computed Tomography (CT) examination, this study designed a simple stress position device. By analyzing the relevant data of stress position footprints and weight-bearing position footprints, the feasibility of the stress position device to simulate standing weight-bearing was verified.

METHODS

This study randomly selected 25 volunteers for standing weight-bearing and stress position footprints collection, and measured the relevant indicators of stress position footprints and standing weight-bearing position footprints. Two foot and ankle surgeons conducted two measurements respectively on the footprints. Intra-observer and inter-observer reliability were calculated using intra-class correlation coefficients (ICC). Pearson correlation coefficient, ICC, scatter plot analysis, and paired t-test were used to analyze the stress and weight-bearing position data.

RESULTS

The intra-observer and inter-observer measurement values were reliable. There was a certain degree of correlation between the stress position footprints and weight-bearing position footprints in terms of Pearson correlation coefficient, ICC, and scatter plot analysis. Paired t-tests showed significant differences in Clarke angle (t 2.636, p .012), C-S index (t 10.568, p .000), arch indx (t 2.176, p .035), and arch lower angle (t 6.246, p .000).

CONCLUSION

The stress position device can generate a certain degree of stress, and after further optimization and improvement of the stress position device, it is feasible to apply it to weight-bearing CT examination in clinical settings.

The ceramic coated implant (CCI). Evolution total ankle replacements: a retrospective analysis of 40 ankles with 8 years follow-up

Diminutive data is available on the outcome of several previously used total ankle replacement implants. The purpose of this study was to investigate the medium-term functional and radiological outcome and implant survival of the CCI Evolution implant. Consecutive series of 40 ankles operated in our hospital with primary TAR using the CCI Evolution implant in 2010-2013 were available for follow-up. The prospective clinical and radiographic data including the Kofoed score, subjective satisfaction and standard radiographs were collected preoperatively and at fixed time-points postoperatively. A CT was obtained in cases where osteolysis or loosening were suspected. The improvement of the Kofoed score and subjective satisfaction were statistically significant (p<0.0001). The implant survival was 97% (95% confidence interval (CI) 81%-100 %) at 5 years, and 81 % (95% confidence interval (CI) 60 %-92%) at 8 years. There were altogether 25 (64%) complications. Overall revision rate was 28% and failure rate 13%. The CCI implant outcome was not acceptable. The malposition of prosthetic components, subsidence, and peri-implant osteolysis were recorded often. Although the patient reported outcome measures improved, mostly due to positive changes in pain severity, overall revision and failure rates were high and comparable with previous findings of the CCI implant.

The Emerging Role of Automation, Measurement Standardization, and Artificial Intelligence in Foot and Ankle Imaging: An Update

In the past few years, advances in clinical imaging in the realm of foot and ankle have been consequential and game changing. Improvements in the hardware aspects, together with the development of computer-assisted interpretation and intervention tools, have led to a noticeable improvement in the quality of health care for foot and ankle patients. Focusing on the mainstay imaging tools, including radiographs, computed tomography scans, and ultrasound, in this review study, the authors explored the literature for reports on the new achievements in improving the quality, accuracy, accessibility, and affordability of clinical imaging in foot and ankle.

Unique shape variations of hind and midfoot bones in flatfoot subjects-A statistical shape modeling approach

Flatfoot deformity is a prevalent hind- and midfoot disorder. Given its complexity, single-plane radiological measurements omit case-specific joint interaction and bone shape variations. Three-dimensional medical imaging assessment using statistical shape models provides a complete approach in characterizing bone shape variations unique to flatfoot condition. This study used statistical shape models to define specific bone shape variations of the subtalar, talonavicular, and calcaneocuboid joints that characterize flatfoot deformity, that differentiate them from healthy controls. Bones of the aforementioned joints were segmented from computed tomography scans of 40 feet. The three-dimensional hindfoot alignment angle categorized the population into 18 flatfoot subjects (≥7° valgus) and 22 controls. Statistical shape models for each joint were defined using the entire study cohort. For each joint, an average weighted shape parameter was calculated for each mode of variation, and then compared between flatfoot and controls. Significance was set at p < 0.05, with values between 0.05 ≤ p < 0.1 considered trending towards significance. The flatfoot population showed a more adducted talar head, inferiorly inclined talar neck, and posteriorly orientated medial subtalar articulation compare to controls, coupled with more navicular eversion, shallower navicular cup, and more prominent navicular tuberosity. The calcaneocuboid joint presented trends of a more adducted calcaneus, more abducted cuboid, narrower calcaneal roof, and less prominent cuboid beak compared to controls. Statistical shape model analysis identified unique shape variations which may enhance understanding and computer-aided models of the intricacies of flatfoot, leading to better diagnosis and, ultimately, surgical treatment.

Etiology, Classification, Diagnostics, and Conservative Management of Osteochondral Lesions of the Talus. 2023 Recommendations of the Working Group "Clinical Tissue Regeneration" of the German Society of Orthopedics and Traumatology

METHODS

Peer-reviewed literature was analyzed regarding different topics relevant to osteochondral lesions of the talus (OLTs) treatment. This process concluded with a statement for each topic reflecting the best scientific evidence available for a particular diagnostic or therapeutic concept, including the grade of recommendation. Besides the scientific evidence, all group members rated the statements to identify possible gaps between literature and current clinical practice.

CONCLUSION

In patients with minimal symptoms, OLT progression to ankle osteoarthritis is unlikely. Risk factors for progression are the depth of the lesion on MRI, subchondral cyst formation, and the extent of bone marrow edema. Conservative management is the adaptation of activities to the performance of the ankle joint. A follow-up imaging after 12 months helps not to miss any progression. It is impossible to estimate the probability of success of conservative management from initial symptoms and imaging. Cast immobilization is an option in OLTs in children, with a success rate of approximately 50%, although complete healing, estimated from imaging, is rare. In adults, improvement by conservative management ranges between 45% and 59%. Rest and restrictions for sports activities seem to be more successful than immobilization. Intra-articular injections of hyaluronic acid and platelet-rich plasma can improve pain and functional scores for more than 6 months. If 3 months of conservative management does not improve symptoms, surgery can be recommended.

Cone-beam CT imaging with laterally enlarged field of view based on independently movable source and detector

BACKGROUND

CBCT imaging with field of views (FOVs) exceeding the size of scans acquired in the conventional imaging geometry, i.e. with opposing source and detector, is of high clinical importance for many medical fields. A novel approach for enlarged FOV scanning with one full-scan (EnFOV360) or two short-scans (EnFOV180) using an O-arm system arises from non-isocentric imaging based on independent source and detector rotations.

PURPOSE

The presentation, description, and experimental validation of this novel approach and the novel scanning techniques EnFOV360 and EnFOV180 for an O-arm system forms the scope of this work.

METHODS

We describe the EnFOV360, EnFOV180, and non-isocentric imaging techniques for the acquisition of laterally extended FOVs. For their experimental validation, scans of dedicated quality assurance as well as anthropomorphic phantoms were acquired, with the phantoms being placed both within the tomographic plane and at the longitudinal FOV border with and without lateral shifts from the gantry center. Based on this, geometric accuracy, contrast-noise-ratio (CNR) of different materials, spatial resolution, noise characteristics, as well as CT number profiles were quantitatively assessed. Results were compared to scans performed with the conventional imaging geometry.

RESULTS

With EnFOV360 and EnFOV180, we increased the in-plane size of acquired FOVs from 250 × 250 mm2 obtained for the conventional imaging geometry to up to 400 × 400 mm2 for the performed measurements. Geometric accuracy was very high for all scanning techniques with mean values ≤0.21 ± 0.11 mm. CNR and spatial resolution were comparable between isocentric and non-isocentric full-scans as well as EnFOV360, whereas substantial image quality deteriorations in this respect were observed for EnFOV180. Image noise in the isocenter was lowest for conventional full-scans with 13.4 ± 0.2 HU. For laterally shifted phantom positions, noise increased for conventional scans and EnFOV360, whereas noise reductions were observed for EnFOV180. Considering the anthropomorphic phantom scans, both EnFOV360 and EnFOV180 were comparable to conventional full-scans.

CONCLUSION

Both enlarged FOV techniques have high potential for imaging laterally extended FOVs. EnFOV360 revealed an image quality comparable to conventional full-scans in general. EnFOV180 showed an inferior performance particularly regarding CNR and spatial resolution.

A Cadaveric Comparison of the Kinematic and Anatomical Axes and Arthrokinematics of the Metatarsosesamoidal and First Metatarsophalangeal Joints

Presently, developments in weightbearing computed tomography and biplanar fluoroscopy technologies offer exciting avenues for investigating normative and pathologic foot function with increasing precision. Still, data quantifying sesamoid bone and proximal phalange motion are currently sparse. To express joint kinematics and compare various clinical cohorts, future studies of first ray motion will necessitate robust coordinate frames that respect the variations in underlying anatomy while also aligning closely with the functional, physiological axes of motion. These activity-dependent functional axes may be represented by a mean helical axis of the joint motion. Our cadaveric study quantified joint kinematics from weightbearing computed tomography scans during simulated toe lift and heel rise tasks. We compared the spatial orientations of the mean finite helical axes of the metatarsosesamoidal and metatarsophalangeal joints to the primary joint axis of two relevant methods for defining metatarsal coordinate frames: inertial axes and fitting of geometric primitives. The resultant kinematics exhibited less crosstalk when using a metatarsal coordinate system based on fitting cylindrical primitives to the bony anatomy compared to using principal component axes. Respective metatarsophalangeal and metatarsosesamoidal arthrokinematic contact paths and instantaneous centers of rotation were similar between activities and agree well with currently published data. This study outlines a methodology for quantitatively assessing the efficacy and utility of various anatomical joint coordinate system definitions. Improvements in our ability to characterize the shape and motion of foot bones in the context of functional tasks will elucidate their biomechanical roles and aid clinicians in refining treatment strategies.

Definitions and Measurements of Hindfoot Alignment and Their Biomechanical and Clinical Implications

This article presents a critical review of the past and the current state of the art in defining and measuring hindfoot, ankle, and subtalar alignment. It describes the transition occurring at present from two-dimensional to three-dimensional (3D) alignment measurements, which accompany the emergence of new, functional, high-resolution imaging modalities such as the weight-bearing cone-beam computerized tomography (CT) imaging. To ease and enhance the transition and acceptability of 3D alignment measurements, new acceptable standards for different clinical application are highly desirable.

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

Weight bearing CT (WBCT) of the lower extremity is gaining momentum in evaluation of the foot/ankle and knee. A growing number of international studies use WBCT, which is promising for improving our understanding of anatomy and biomechanics during natural loading of the lower extremity. However, we believe there is risk of excessive enthusiasm for WBCT leading to premature application of the technique, before sufficiently robust protocols are in place e.g. standardised limb positioning and imaging planes, choice of anatomical landmarks and image slices used for individual measurements. Lack of standardisation could limit benefits from introducing WBCT in research and clinical practice because useful imaging information could become obscured. Measurements of bones and joints on WBCT are influenced by joint positioning and magnitude of loading, factors that need to be considered within a 3-D coordinate system. A proportion of WBCT studies examine inter- and intraobserver reproducibility for different radiological measurements in the knee or foot with reproducibility generally reported to be high. However, investigations of test-retest reproducibility are still lacking. Thus, the current ability to evaluate, e.g. the effects of surgery or structural disease progression, is questionable. This paper presents an overview of the relevant literature on WBCT in the lower extremity with an emphasis on factors that may affect measurement reproducibility in the foot/ankle and knee. We discuss the caveats of performing WBCT without consensus on imaging procedures and measurements.

Ankle surgery in 2022: What do the scientific articles say, and what do the patients?

V.

Computed Tomography Scan Architectural Measurements in Adult Foot and Ankle Surgery: A Narrative Review for Orthopaedic Trainees

CT scan plays an important role in adult foot and ankle surgery. Plain radiographs are usually the first-line imaging modality for assessing foot and ankle bone and joint architectural abnormalities. However, despite the fact that a CT scan is more expensive and associated with higher radiation exposure, it offers better imaging quality for the assessment of bony lesions in orthopaedics and trauma. Evidence has shown that more accurate measurements can be obtained from a CT scan compared to plain radiographs. Weight-bearing multi-detection CT scanning goes the extra mile by providing a more detailed assessment, especially for intra-articular fractures, and mirrors the real-life foot and ankle dynamics compared to conventional non-weight-bearing CT scans. It also has a relatively lower radiation dose compared to conventional CT scans. CT scan is the best modality for assessing bony lesions whereas MRI is better for soft tissue pathology. An understanding of the role of CT scan in the anatomical assessment of the foot and ankle will help improve communication between orthopaedic surgeons, radiologists, and radiographers. A thorough understanding of when to use a CT scan compared to the other imaging modalities will also lead to better surgical outcomes, reduced cost, and reduced risk from radiation exposure. This review article analyzes the role of CT in assessing relevant radiographic architectural measurements for diagnosis and surgical planning in adult foot and ankle surgery.

3D measurement techniques for the hindfoot alignment angle from weight-bearing CT in a clinical population

Cone-beam CT (CBCT) scans now enable accurate measurements on foot skeletal structures with the advantage of observing these in 3D and in weight-bearing. Among the most common skeletal deformities, the varus/valgus of the hindfoot is the most complex to be represented, and a number of measure proposals have been published. This study aims to analyze and to compare these measurements from CBCT scans in a real clinical population with large such deformity. Ten patients with severe acquired adult flatfoot and indication for surgery underwent CBCT scans (Carestream, USA) while standing on that leg, before and after surgical correction. Corresponding 3D shape of each bone of the distal shank and hindfoot were defined (Materialise, Belgium). Six different techniques from the literature were used to calculate the varus/valgus deformity, i.e. the inclination of the hindfoot in the frontal plane of the shank. Standard clinical measurements by goniometers were taken for comparison. According to these techniques, and starting from a careful 3D reconstruction of the relevant foot skeletal structures, a large spectrum of measurements was found to represent the same hindfoot alignment angle. Most of them were very different from the traditional clinical measures. The assessment of the pre-operative valgus deformity and of the corresponding post-operative correction varied considerably. CBCT finally allows 3D assessment of foot deformities in weight-bearing. Measurements from the different available techniques do not compare well, as they are based on very different approaches. It is recommended to be aware of the anatomical and functional concepts behind these techniques before clinical and surgical conclusions.

International Foot and Ankle Osteoarthritis Consortium review and research agenda for diagnosis, epidemiology, burden, outcome assessment and treatment

OBJECTIVE

To summarise the available evidence relating to the diagnosis, epidemiology, burden, outcome assessment and treatment of foot and ankle osteoarthritis (OA) and to develop an agenda to guide future research.

METHOD

Members of the International Foot and Ankle Osteoarthritis Consortium compiled a narrative summary of the literature which formed the basis of an interactive discussion at the Osteoarthritis Research Society International World Congress in 2021, during which a list of 24 research agenda items were generated. Following the meeting, delegates were asked to rank the research agenda items on a 0 to 100 visual analogue rating scale (0 = not at all important to 100 = extremely important). Items scoring a mean of 70 or above were selected for inclusion.

RESULTS

Of the 45 delegates who attended the meeting, 31 contributed to the agenda item scoring. Nineteen research agenda items met the required threshold: three related to diagnosis, four to epidemiology, four to burden, three to outcome assessment and five to treatment.

CONCLUSIONS

Key knowledge gaps related to foot and ankle OA were identified, and a comprehensive agenda to guide future research planning was developed. Implementation of this agenda will assist in improving the understanding and clinical management of this common and disabling, yet relatively overlooked condition.

Assessment of Flatfoot Deformity Using Digitally Reconstructed Radiographs: Reliability and Comparison to Conventional Radiographs

BACKGROUND

Digitally reconstructed radiographs (DRRs) generated from weightbearing computed tomography (WBCT) may potentially substitute for weightbearing plain radiographs (XRs) but have not been clinically validated. This study aims to test the reliability of 6 radiographic parameters of progressive collapsing foot deformity (PCFD) as measured on DRR, to investigate whether DRR represents comparably to XR through the same measurements, and to compare agreement of DRR and XR measurements of a standardized arch height parameter with reference measurements made on WBCT.

METHODS

DRR generated from preoperative WBCT of 71 patients (72 feet) treated surgically for PCFD were retrospectively compared with preoperative weight-bearing XR after exclusion criteria were applied. Six radiographic measurements were performed, including Meary angle, calcaneal pitch (CPA), medial cuneiform height (MCH), AP talar-first metatarsal angle (T-1MT), talonavicular coverage (TNCA), and talar incongruency (TIA). Arch height was measured on XR, DRR, and WBCT using a validated, standardized, navicular-based index. Intraclass correlation coefficients assessed DRR intraobserver and interobserver reliability. Paired samples t tests tested differences between XR and DRR. Bland-Altman limits of agreement analysis compared DRR and XR agreement with WBCT measurements.

RESULTS

Measurements were within standard PCFD ranges on XR and DRR. All measurements demonstrated excellent intrarater reliability and good to excellent interrater agreement, consistent with previous literature on XR. No differences were found for Meary, CPA, or TNCA. Minor differences were observed for MCH, T-1MT, and TIA. DRR measurements demonstrated greater agreement with WBCT than XR measurements.

CONCLUSION

DRR from WBCT may be a promising substitute for XR in the clinical evaluation of PCFD. Radiographic measurements made on DRR demonstrated good to excellent reliability. Although small differences were found between XR and DRR for certain measurements, DRR more accurately represented medial arch anatomy compared to gold standard WBCT data than XR. If validated as a clinical substitute, DRR could eventually obviate XR where WBCT is available.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Early results and complication rate of the LapiCotton procedure in the treatment of medial longitudinal arch collapse: a prospective cohort study

INTRODUCTION

Instability/collapse of the medial column has been associated with many conditions, particularly progressive collapsing foot deformity (PCFD), hallux valgus (HV), and midfoot arthritis (MA). Restoration of first ray length and sagittal plane alignment to restore the foot tripod is essential when treating these deformities. This study aimed to assess early results, healing, and complication rate of a distraction dorsal opening plantarflexion wedge allograft first tarsometatarsal joint fusion (LapiCotton Procedure) in patients with collapse/instability of the medial column.

METHODS

In this prospective cohort study, we included PCFD, HV, and MA patients that underwent a LapiCotton procedure. Fusion site healing was defined by > 50% bone bridging in both interfaces between allograft wedge and host bone using weight-bearing computed tomography (WBCT) after 3 months. First ray collapse radiographic correction and minor and major complications (deep dehiscence, deep infection, and reoperation) were assessed.

RESULTS

A total of 22 patients (22 feet) were included (11 PCFD, 6 MA, and 5 of HV patients). Mean follow-up was 5.9 months (range 3-12) and median allograft size was 8 mm (range 5-19 mm). Bone healing was observed in 91% of cases. Two minor complications (9%, both superficial dehiscence) and one major complication (4.5%, deep infection) were observed. Statistically significant improvement of the sagittal plane talus-first metatarsal angle was observed, with mean improvement of 9.4° (95% CI 6.7-12.1°; p < 0.0001).

CONCLUSION

In this prospective cohort study of 22 patients treated with the LapiCotton procedure for medial longitudinal arch collapse/instability, we observed a low complication rate (9% minor, 4.5% major), high healing rate after 3 months (91%), one clinically stable radiographic non-union (4.5%) and one unstable non-union (4.5%) needing reoperation. Our results demonstrate promising initial results for LapiCotton technique in treating collapse of the medial longitudinal arch in patients with PCFD, MA and HV deformities. Long-term results are needed to confirm these promising results.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Multimodality imaging of the paediatric flatfoot

Flatfoot is commonly encountered in the paediatric population and describes a spectrum of clinical and radiological presentations which encompass both normally developing and pathological feet. Flatfoot can be categorised as flexible or rigid, a distinction which has important implications when considering the potential underlying aetiology and treatment options, and therefore imaging is an important component of the diagnostic workup. Weight-bearing plain radiographs are established initial investigations, although the significance of a number of the commonly derived quantitative parameters in children remains unclear. CT and MRI are important additional imaging modalities reserved for the investigation of symptomatic cases or those in which an underlying structural abnormality is suspected, rigid flatfoot commonly falling into one of these two categories. We review and illustrate the multimodality imaging of the paediatric flatfoot, with reference to both qualitative and quantitative radiographic assessment and cross-sectional imaging appearances.

Angular and linear measurements of adult flexible flatfoot via weight-bearing CT scans and 3D bone reconstruction tools

Acquired adult flatfoot is a frequent deformity which implies multiple, complex and combined 3D modifications of the foot skeletal structure. The difficult thorough evaluation of the degree of severity pre-op and the corresponding assessment post-op can now be overcome by cone-beam (CBCT) technology, which can provide access to the 3D skeletal structure in weight-bearing. This study aims to report flatfoot deformities originally in 3D and in weight-bearing, with measurements taken using two different bone segmentation techniques. 21 such patients, with indication for surgical corrections, underwent CBCT (Carestream, US) while standing on one leg. From these scans, 3D models of each bone of the foot were reconstructed by using two different state-of-the-art segmentation tools: a semi-automatic (Mimics Innovation Suite, Materialise, Belgium), and an automatic (Bonelogic Ortho Foot and Ankle, Disior, Finland). From both reconstructed models, Principal Component Analysis was used to define anatomical reference frames, and original foot and ankle angles and other parameters were calculated mostly based on the longitudinal axis of the bones, in anatomical plane projections and in 3D. Both bone model reconstructions revealed a considerable valgus of the calcareous, plantarflexion and internal rotation of the talus, and typical Meary’s angles in the lateral and transverse plane projections. The mean difference from these angles between semi-automatic and automatic segmentations was larger than 3.5 degrees for only 3 of the 32 measurements, and a large number of these differences were not statistically significant. CBCT and the present techniques for bone shape reconstruction finally provide a novel and valuable 3D assessment of complex foot deformities in weight-bearing, eliminating previous limitations associated to unloaded feet and bidimensional measures. Corresponding measurements on the bone models from the two segmentation tools compared well. Other more representative measurements can be defined in the future using CBCT and these techniques.

Weightbearing Computed Tomography for Assessment of Foot and Ankle Deformities: The Iowa Experience

BACKGROUND

Weightbearing computed tomography (WBCT) is a reliable and precise modality for the measurement and analysis of bone position in the foot and ankle, as well as associated deformities. WBCT to assess three dimensional relationships among bones allowed the development of new measurements, as the Foot and Ankle Offset (FAO), which has high inter and intra-rater reliability. This study reports the University of Iowa's experience utilizing WBCT for the care of foot and ankle patients by describing its utility across different orthopedic diseases in improving diagnostic assessment, aiding surgical planning, and expanding the use for objective clinical follow-up.

METHODS

The medical records of consecutive patients with various foot and ankle disorders that underwent WBCT examination as part of the standard of care at a single institution between November 2014 and August 2020 were retrospectively reviewed. Patient factors, including body mass index (BMI), sex, and patient comorbidities were collected. 3D coordinates for calculation of FAO were harvested using the Multiplanar Reconstruction (MPR) views were calculated from the obtained exams. Descriptive statistics were performed with Shapiro-Wilk test and the Anderson-Darling tests.

RESULTS

1175 feet and ankles (820 patients) had a WBCT performed over the studied 68 months. 53% of the subjects were male and 47% female. 588 of the acquisitions were from the right side (50.04%) and 587 from the left side (49.96%). Diabetes was present in 15.47% of, Rheumatic diagnoses in 4.52% and smoking habits in 44.10% of patients. Mean BMI of the sample was found to be 32.47 (32.03-32.90, 95% CI). The mean Foot and Ankle Offset (FAO) encountered in the study's population was 2.43 (2.05-2.82, 95% CI; min -30.8, max 37.65; median 2.39).

CONCLUSION

This study contains the largest cohort of WBCTs with accompanied FAO measurements to date, which can aid with establishing a new baseline FAO measurement for multiple pathological conditions. Acquiring WBCTs resulted in a variety of more specific diagnoses for patient with foot and ankle complaints. The ability to utilize WBCT for presurgical planning, the capability to provide a 3D reconstruction of patient anatomy, and its use for assessment of advanced relational foot and ankle measurements, such as FAO, demonstrate how WBCT may serve as a remarkable utility in clinical practice and has become a standard of care in our practice at the University of Iowa.Level of Evidence: IV.