Combination of PedCAT Weightbearing CT With Pedography Assessment of the Relationship Between Anatomy-Based Foot Center and Force/Pressure-Based Center of Gravity

Fit of fire boots: exploring internal morphology using computed tomography

Fit of fire boots is a crucial factor in the safety and performance of firefighters on the hostile fireground. Firefighters have reported that ill-fitting fire boots restrict their lower body movement and sometimes cause very dangerous situations by falling off behind the wearer. By using computed tomography, this study demonstrates the potential to quantify and visualize the fit of fire boots, which previously relied on subjective feedback from the wearers. The high-resolution three-dimensional (3D) models of two fire boot products allowed a detailed observation and measurement of the internal space of the boots. Also, the boot's internal dimension was compared to the foot measurement of local firefighters, showing the significant differences between the two boots. Lastly, simulation wrapping the 3D scanned foot with the boot revealed large void spaces around the toe box and ankle, as well as the narrower ball width of the boot than the foot.

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.

Medializing Calcaneal Osteotomy for progressive collapsing foot deformity alters the three-dimensional subtalar joint alignment

BACKGROUND

A medializing calcaneal osteotomy (MCO) is considered as one of the key inframalleolar osteotomies to correct progressive collapsing foot deformity (PCFD). While many studies were able to determine the post-operative hind- and midfoot alignment, alternations of the subtalar joint alignment remained obscured by superposition on plain radiography. Therefore, we aimed to assess the hind-, midfoot- and subtalar joint alignment pre- compared to post-operatively using 3D weightbearing CT (WBCT) imaging.

METHODS

Seventeen patients with a mean age of 42 ± 17 years were retrospectively analyzed. Inclusion criteria consisted of PCFD deformity corrected by a medializing calcaneal osteotomy (MCO) as main procedure and imaged by WBCT before and after surgery. Exclusion criteria were patients who had concomitant calcaneal lengthening osteotomies, mid-/hindfoot fusions, hindfoot coalitions, and supramalleolar procedures. Image data were used to generate 3D models and compute the hindfoot (HA), midfoot (MA) - and subtalar joint (STJ) alignment in the coronal, sagittal and axial plane, as well as distance maps.

RESULTS

Pre-operative measurements of the HA and MA improved significantly relative to their post-operative equivalents p < 0.05). The post-operative STJ alignment showed significant inversion (2.8° ± 1.7), abduction (1.5° ± 1.8), and dorsiflexion (2.3° ± 1.7) of the talus relative to the calcaneus (p < 0.05) compared to the pre-operative alignment. The displacement between the talus and calcaneus relative to the sinus tarsi increased significantly (0.6 mm±0.5; p < 0.05).

CONCLUSION

This study detected significant changes in the sagittal, coronal, and axial plane alignment of the subtalar joint, which corresponded to a decompression of the sinus tarsi. These findings contribute to our clinical practice by demonstrating the magnitude of alteration in the subtalar joint alignment that can be expected after PCFD correction with MCO as main procedure.

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.

Can Weight-Bearing Computed Tomography Be a Game-Changer in the Assessment of Ankle Sprain and Ankle Instability?

Ankle sprain and chronic lateral ankle instability are complex conditions and challenging to treat. Cone beam weight-bearing computed tomography is an innovative imaging modality that has gained popularity, with a body of literature reporting reduced radiation exposure and operating time, and shortened examination time and a decreased time interval between injury and diagnosis. In this article, we make clearer the advantages of this technology and encourage researchers to investigate the area, and clinicians to use it as a primary mode of investigation. We also present clinical cases provided by the authors to illustrate those possibilities using advanced imaging tools.

Diagnostic accuracy of measurements in progressive collapsing foot deformity using weight bearing computed tomography: A matched case-control study

BACKGROUND

We aimed to investigate the diagnostic accuracy of known two-dimensional (2D) and three-dimensional (3D) measurements for Progressive Collapsing Foot Deformity (PCFD) in weight-bearing computed tomography (WBCT). We hypothesized that 3D biometrics would have better specificity and sensitivity for PCFD diagnosis than 2D measurements.

METHODS

This was a retrospective case-control study, including 28 PCFD feet and 28 controls matched for age, sex and Body Mass Index. Two-dimensional measurements included: axial and sagittal talus-first metatarsal angles (TM1A and TM1S), talonavicular coverage angle (TNCA), forefoot arch angle (FFAA), middle facet incongruence angle (MF°) and uncoverage percentage (MF%). The 3D Foot Ankle Offset (FAO) was obtained using dedicated semi-automatic software. Intra and interobserver reliabilities were assessed. Receiver Operating Characteristic (ROC) curves were calculated to determine diagnostic accuracy (Area Under the Curve (AUC)), sensitivity and specificity.

RESULTS

In PCFD, mean MF% and MF° were respectively 47.2% ± 15.4 and 13.3° ± 5.3 compared with 13.5% ± 8.7 and 5.6° ± 2.9 in controls (p < 0.001). The FAO was 8.1% ± 3.8 in PCFD and 1.4% ± 1.7 in controls (p < 0.001). AUCs were 0.99 (95%CI, 0.98-1) for MF%, 0.96 (95%CI, 0.9-1) for FAO, 0.90 (95%CI, 0.81-0.98) for MF°. For MF%, a threshold value equal or greater than 28.7% had a sensitivity of 100% and specificity of 92.8%. Conversely, a FAO value equal or greater than 4.6% had a specificity of 100% and a sensitivity of 89.2%. All other 2D measurements were significantly different in PCFD and controls (p < 0.001).

CONCLUSIONS

MF% and FAO were both accurate measurements for PCFD. MF% demonstrated slightly better specificity. FAO better sensitivity. A combination of threshold values of 28.7% for MF% and 4.6% for FAO yielded 100% sensitivity and specificity.

Automatic software-based 3D-angular measurement for Weight-Bearing CT (WBCT) provides different angles than measurement by hand

BACKGROUND

Purpose of this study was to compare automatic software-based angular measurement (AM, Autometrics, Curvebeam, Warrington, PA, USA) with previously validated measurement by hand (MBH) regarding angle values and time spent for the investigator for Weight-Bearing CT (WBCT).

METHODS

Five-hundred bilateral WBCT scans (PedCAT, Curvebeam, Warrington, PA, USA) were included in the study. Five angles (1st - 2nd intermetatarsal angle, talo-metatarsal 1-angle (TMT) dorsoplantar and lateral projection, hindfoot angle, calcaneal pitch angle) were measured with MBH and AM on the foot/ankle (side with pathology). Angles and time spent of MBH and AM were compared (t-test, homoscedatic).

RESULTS

The specific pathologies were ankle osteoarthritis/instability, n = 147 (29%); Haglund deformity/Achillodynia, n = 41 (8%); forefoot deformity, n = 108 (22%); Hallux rigidus, n = 37 (7%); flatfoot, n = 35 (7%); cavus foot, n = 10 (2%); osteoarthritis except ankle, n = 82 (16%). The angles differed between MBH and AM (each p < 0.001) except the calcaneal pitch angle (p = 0.05). The time spent for MBH / AM was 44.5 ± 12 s / 1 ± 0 s on average per angle (p < 0.0011).

CONCLUSIONS

AM provided different angles as MBH and can currently not be considered as validated angle measurement method. The investigator time spent is 97% lower for AM (1 s per angle) than for MBH (44.5 s per angle). Cases with correct angles in combination with almost no time spent showed the real potential of AM. The AM system will have to become reliable (especially in diminishing positive and negative angle values as defined) and valid which has to be proven by planned studies in the future.

LEVEL OF EVIDENCE

Level III.

Semi-automatic software-based 3D-angular measurement for Weight-Bearing CT (WBCT) in the foot provides different angles than measurement by hand

BACKGROUND

The purpose of this study was to compare semi-automatic software-based angular measurement (SAM) with previously validated measurement by hand (MBH) regarding angle values and time spent for the investigator for Weight-Bearing CT (WBCT).

METHODS

In this retrospective comparative study, five-hundred bilateral WBCT scans (PedCAT, Curvebeam, Warrington, PA, USA) were included in the study. Five angles (1st - 2nd intermetatarsal angle (IM), talo-metatarsal 1-angle (TMT) dorsoplantar and lateral projection, hindfoot angle, calcaneal pitch angle) were measured with MBH and SAM (Bonelogic Ortho Foot and Ankle, Version 1.0.0-R, Disior Ltd, Helsinki, Finland) on the right/left foot/ankle. The angles and time spent of MBH and SAM were compared (t-test, homoscesdatic).

RESULTS

The angles differed between MBH and SAM (mean values MBH/SAM; IM, 9.1/13.0; TMT dorsoplantar, -3.4/8.2; TMT lateral. -6.4/-1.1; hindfoot angle, 4.6/21.6; calcaneal pitch angle, 20.5/20.1; each p < 0.001 except the calcaneal pitch angle, p = 0.35). The time spent for MBH / SAM was 44.5 ± 12 s / 12 ± 0 s on average per angle (p < 0.001).

CONCLUSIONS

SAM provided different angles as MBH (except calcaneal pitch angle) and can currently not be considered as validated angle measurement method (except calcaneal pitch angle). The investigator time spent is 73% lower for SAM (12 s per angle) than for MBH (44.5 s per angle). SAM might be an important step forward for 3D-angle measurement of WBCT when valid angles are provided.

Weightbearing CT assessment of foot and ankle joints in Pes Planovalgus using distance mapping

INTRODUCTION

The goal of this study was to describe the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints in patients presenting with Pes Planovalgus (PPV) using three-dimensional (3D) distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of PPVs to a series of normally-aligned feet. We hypothesized that in PPVs joint interactions would reveal significantly increased spaces in the medial side of the ankle, hindfoot and midfoot joints.

METHODS

In this case-control study, ten feet (10 patients) with asymptomatic PPV were compared to 10 matched-paired (by age, gender and body mass index) normally-aligned feet (10 patients). Three-dimensional models were produced from the images and distance maps representing joint surface configuration were generated for the ankle, hindfoot and midfoot joints. The distance maps for each joint were then compared between the two groups and between regions in the same group.

RESULTS

In PPV patients there was a significantly increased surface-to-surface distance anteromedially at the ankle joint (+46.3%, p < 0.001) along with an increased distance on the anterior halves of both the medial (+21.3%, p = 0.098) and lateral malleoli (+22.7%, p = 0.038). At the posterolateral corner of the posterior facet of the subtalar joint we found an increased surface-to-surface distance (by 57.1%, p < 0.001), while at the talonavicular joint there was a reduction of the distance at the superomedial corner (-20%, p = 0.097) along with a significant increase in the upper central (+20%, p = 0.039) and lateral (+30.7%, p = 0.015) zones. A reduction of the surface-to-surface distance was also observed in three of the four zones of the calcaneocuboid joint. Finally, a statistically significant increase in the mean distance was observed at the naviculocuneiform and tarsometatarsal joints in a range between 38% and 93.4% (p < 0.001 in all cases).

CONCLUSION

We found significant differences in surface-to-surface interaction at the foot and ankle joints between Pes Planovalgus and normally-aligned controls. Distance mapping on WBCT images could be used in clinical practice as a diagnostic support to gauge the morphological changes of articular spaces occurring in Pes Planovalgus.

LEVEL OF EVIDENCE

Level III, case-control 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.

The Assessment of Ankle Osteoarthritis with Weight-Bearing Computed Tomography

The standard for diagnostic radiographic imaging in foot and ankle surgery was until 2012 radiographs with full weight-bearing without any useful alternative. Weight-bearing cone-beam computed tomography (WBCT) was introduced 2012 for foot and ankle use as a new technology that allows 3D imaging with full weight-bearing which should be not influenced by projection and/or foot orientation. The assessment of ankle osteoarthritis with WBCT including the description of healthy status, effect of alignment and7or (in)stability is extensively illustrated in this review article.

An Innovative Weightbearing Device for Weightbearing 3-Dimensional Imaging for Foot and Ankle Surgery Preoperative Planning

Three-dimensional preoperative planning has demonstrated multiple surgical advantages. Currently, we cannot carry out preoperative 3-dimensional planning of foot and ankle orthopedics in most hospitals due to the impossibility of performing weightbearing CT imaging. Our objective is to describe and evaluate an innovative accessible, simple, and effective device that simulates standing while in a supine position, to obtain 3-dimensional images supporting bodyweight load with a conventional CT machine. From a group of 30 volunteers, 10 patients were randomly selected and pressure and its distribution were analyzed while in a standing position in both feet. Differences between both feet were considered normal intrapersonal variability. Subsequently, the right footprint of the same 10 subjects was evaluated in the proposed loading device. Then, their pressures and distribution were compared with respect to standing and with respect to intrapersonal variability. The mean total standing pressure was 93 Kpa (standard deviation [SD] 14.32), which was reduced to 81.95 Kpa (SD 19.54) in the loading device. The load device reduced the pressure by a mean of16% (SD 22% (range -25% to -0.03%). At the hindfoot level, the loading device increased pressure by a mean of 20.59 Kpa, which expressed percentage implies an increase of 14% compared to standing. Due to its easy construction and effectiveness, this is the first device that opens the door of foot and ankle orthopedics in any hospital to 3D preoperative planning and the benefits derived from it.

Is Advanced Imaging a Must in the Assessment of Progressive Collapsing Foot Deformity?

Advanced imaging modalities have, in very recent years, enabled a considerable leap in understanding progressive collapsing foot deformity, evolving from a simple confirmation of clinical diagnostic using basic measurements to minute understanding of soft tissue and bone involvements. MRI and weight-bearing cone-beam computed tomography are enabling the development of new 3-dimensional measurement modalities. The identification of key articular and joint markers of advanced collapse will allow surgeons to better indicate treatments and assess chances of success with conservative therapies and less invasive surgical procedures, with the hope of improving patient outcomes.

Distance mapping of the foot and ankle joints using weightbearing CT: The cavovarus configuration

INTRODUCTION

The goal of this study was to characterize the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints of the cavovarus foot using distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of cavovarus feet to a series of normally-aligned feet.

METHODS

In this case-control study, ten feet (10 patients) with asymptomatic cavovarus shape (cases; N = 10) were compared to 10 matched-paired (by age, gender and body mass index) normally-aligned feet (10 patients) (controls; N = 10). Three-dimensional models were produced from the images and distance maps representing joint surface configuration were generated for the ankle, hindfoot and midfoot joints. The distance maps for each joint were then compared between the two groups and between regions in the same group.

RESULTS

In the cavovarus group there was a significant increase in surface-to-surface distance at the posterior tibiotalar joint and a reduced distance at the anterior part, together with a greater distance at the posterior half of the medial gutter. Also, a decrease in surface-to-surface distance on the anterior half of the anterior facet and an increased distance on the posterior quadrants of the posterior facet of the subtalar joint were found. At the sinus tarsi, the lateral aspect of the talonavicular joint, the naviculocuneiform and the tarsometatarsal joints there was a statistically significant increase in surface-to-surface distance in cavovarus patients as compared to controls.

CONCLUSION

Distance mapping analysis on WBCT images identified significant differences in surface-to-surface interaction at the foot and ankle joints between cavovarus and normally-aligned feet.

LEVEL OF EVIDENCE

Level III, case-control study.

Techniques for 3D foot bone orientation angles in weight-bearing from cone-beam computed tomography

BACKGROUND

For the diagnosis and treatment of foot and ankle disorders, objective quantification of the absolute and relative orientation angles is necessary. The present work aims at assessing novel techniques for 3D measures of foot bone angles from current Cone-Beam technology.

METHODS

A normal foot was scanned via weight-bearing CT and 3D-model of each bone was obtained. Principal Component Analysis, landmark-based and mid-diaphyseal axes were exploited to obtain bone anatomical references. Absolute and relative angles between calcaneus and first metatarsal bone were calculated both in 3D and in a simulated sagittal projections. The effects of malpositioning were also investigated via rotations of the entire foot model.

RESULTS

Large angle variations were found between the different definitions. For the 3D relative orientation, variations larger than 10 degrees were found. Foot malposition in axial rotation or in varus/valgus can result in errors larger than 5 and 3 degrees, respectively.

CONCLUSIONS

New measures of foot bone orientation are possible in 3D and in weight-bearing, removing operator variability and the effects of foot positioning.

Weight-bearing CT in foot and ankle pathology

Cone-beam scanners (CBCT) enable CT to be performed under weight-bearing - notably for the foot and ankle. The technology is not new: it has been used since 1996 in dental surgery, where it has come to replace panoramic X-ray. What is new is placing the scanner on the ground, so as to have 3D weight-bearing images, initially of the foot and ankle, and later for the knee and pelvis. This saves time, radiation and money. It is now increasingly used, but is unfortunately limited by not having specific national health insurance cover in France, and by the psychological reticence that goes with any technological breakthrough. A review of the topic is indispensable, as it is essential to become properly acquainted with this technique. To this end, we shall be addressing 5 questions. What biases does conventional radiography incur? Projecting a volume onto a plane incurs deformation, precluding true measurement. Conventional CT is therefore often associated with an increased dose of radiation. What is the impact of CBCT on radiation dose, costs and the care pathway? The conical beam turns around the limb (under weight-bearing if so desired) in less than a minute, making the radiation dose no greater than in standard X-ray. What does the literature have to say about CBCT, and what are the indications? CBCT is indicated in all foot and ankle pathologies, and indications now extend to the upper limb and the knee, and will soon include the pelvis. How are angles measured on this 3D technique? The recently developed concept of 3D biometry uses dedicated software to identify anatomic landmarks and automatically segment the bones, thereby enabling every kind of measurement. What further developments are to be expected? CBCT may become indispensable to lower-limb surgical planning. Artificial Intelligence will reveal novel diagnostic, prognostic and therapeutic solutions. LEVEL OF EVIDENCE: V; expert opinion.

Weight-bearing cone-beam computed tomography in the foot and ankle specialty: where we are and where we are going - an update

Cone-beam computed tomography (CBCT) has been applied in dentistry and medicine for nearly two decades. Its application in the foot and ankle specialty has grown exponentially in recent years. Weight-bearing CBCT allows clinicians to obtain weight-bearing images that can be viewed in all three planes and to construct three-dimensional models, similar to those constructed from traditional CT scans, as well as exposing patients to less radiation than do traditional CT scans. This technology has revolutionized diagnoses, improving the understanding of various lesions and surgical planning in the foot and ankle specialty. Ongoing studies of the use of weight-bearing CBCT in foot and ankle surgery are focused on fully automated and semi-automated three-dimensional measurements, as well as bone segmentation, mapping of the distances/orientation of the joints, and the production of customized implants. The aims of this review article are to show the evolution of this emerging tool in the foot and ankle specialty, to update those in related specialties on its use in current clinical practice, and to indicate where the research community is heading.

Correlations between weight-bearing 3D bone architecture and dynamic plantar pressure measurements in the diabetic foot

BACKGROUND

Measurements of plantar loading reveal foot-to-floor interaction during activity, but information on bone architecture cannot be derived. Recently, cone-beam computer tomography (CBCT) has given visual access to skeletal structures in weight-bearing. The combination of the two measures has the potential to improve clinical understanding and prevention of diabetic foot ulcers. This study explores the correlations between static 3D bone alignment and dynamic plantar loading.

METHODS

Sixteen patients with diabetes were enrolled (group ALL): 15 type 1 with (N, 7) and without (D, 8) diabetic neuropathy, and 1 with latent autoimmune diabetes. CBCT foot scans were taken in single-leg upright posture. 3D bone models were obtained by image segmentation and aligned in a foot anatomical reference frame. Absolute inclination and relative orientation angles and heights of the bones were calculated. Pressure patterns were also acquired during barefoot level walking at self-selected speed, from which regional peak pressure and absolute and normalised pressure-time integral were worked out at hallux and at first, central and fifth metatarsals (LOAD variables) as averaged over five trials. Correlations with 3D alignments were searched also with arch index, contact time, age, BMI, years of disease and a neuropathy-related variable.

RESULTS

Lateral and 3D angles showed the highest percentage of significant (p < 0.05) correlations with LOAD. These were weak-to-moderate in the ALL group, moderate-to-strong in N and D. LOAD under the central metatarsals showed moderate-to-strong correlation with plantarflexion of the 2nd and 3rd phalanxes in ALL and N. LOAD at the hallux increased with plantarflexion at the 3rd phalanx in ALL, at 1st phalanx in N and at 5th phalanx in D. Arch index correlated with 1st phalanx plantarflexion in ALL and D; contact time showed strong correlation with 2nd and 3rd metatarsals and with 4th phalanx dorsiflexion in D.

CONCLUSION

These preliminary original measures reveal that alteration of plantar dynamic loading patterns can be accounted for peculiar structural changes of foot bones. Load under the central metatarsal heads were correlated more with inclination of the corresponding phalanxes than metatarsals. Further analyses shall detect to which extent variables play a role in the many group-specific correlations.

Weight-bearing CT Scans in Foot and Ankle Surgery

Weight-bearing CT (WBCT) scans of the foot and ankle have improved the understanding of deformities that are not easily identified on radiographs and are increasingly being used by orthopaedic surgeons for diagnostic and preoperative planning purposes. In contrast to standard CT scans, WBCT scans better demonstrate the true orientation of the bones and joints during loading. They have been especially useful in investigating the alignment of complex pathologies such as adult-acquired flatfoot deformity in which patients have been found to have a more valgus subtalar joint alignment than in a normal cohort and high rates of subfibular impingement. Studies using WBCT scans have also provided new insight into more common lower extremity conditions such as hallux valgus, ankle fractures, and lateral ankle instability. WBCT scans have allowed researchers to investigate pronation of the first metatarsal in patients with hallux valgus compared with normal feet, and patients with lateral ankle instability have been found to have more heel varus than healthy control subjects. Understanding the application of WBCT scans to clinical practice is becoming more important as surgeons strive for improved outcomes in the treatment of complicated foot and ankle disorders.

Results of more than 11,000 scans with weightbearing CT - Impact on costs, radiation exposure, and procedure time

BACKGROUND

Weightbearing CT (WBCT) has been proven to more precisely measure bone position than conventional weightbearing radiographic series (R) and conventional CT (CT). The purpose of this study was to assess the benefit of using WBCT instead of R and/or CT as the standard imaging modality, evaluating image acquisition time, radiation dose, and cost-effectiveness.

METHODS

All patients who obtained a WBCT as part of standard of care from July 1, 2013 until March 15, 2019 were included in the study. Image acquisition time (T), radiation dose (RD) per patient, and cost-effectiveness were analyzed and compared between the time period using WBCT (yearly average) and the parameters from 2012, i.e. before the availability of WBCT (RCT group).

RESULTS

11,009 WBCT scans were obtained from 4987 patients (4,987 scans (45%) before treatment; 6,022 scans (55%) at follow-up). On a yearly average, 1,957 WBCTs (bilateral scans) and an additional 10.6 CTs (bilateral feet and ankles) were obtained (WBCT group). In 2012, 1,850 Rs (bilateral feet, dorsoplantar and lateral, metatarsal head skyline view) and 254 CTs were obtained from 885 patients (RCT group). The mean yearly RD was 4.3/4.8uSv for the WBCT/RCT groups (mean difference of .5uSv; a decrease of 10% for the WBCT group; p<.01). Yearly mean T was 114/493h in total (3.3/16.0min per patient) for WBCT/RCT groups (mean difference of 379h; a 77% decrease for the WBCT group; p<.01). Yearly cost-effectiveness was a mean profit of 43,959/-723 Euros for WBCT/RCT groups.

CONCLUSIONS

11,009 WBCT scans from 4,987 patients over a period of 5.6 years at a foot and ankle department resulted in 10% decreased RD, 77% decreased T, and increased financial profit (51 Euros per patient) for the institution.

Use of Advanced Weightbearing Imaging in Evaluation of Hallux Valgus

Hallux valgus (HV) represents a progressive 3-dimensional deformity that includes bone malalignment, hypermobility of the first ray, and imbalanced soft-tissue structures of the midfoot and forefoot. Conventional radiographs provide sectorized and limited information of the deformity in different planes. The literature evidence supporting the use of cone beam weightbearing computed tomography in the assessment of HV has been growing. It demonstrates important advances that include the ability to reliably perform traditional measurements such as HV angle and intermetatarsal angle in the 3-dimensional setting.

Centre of Rotation of the Human Subtalar Joint Using Weight-Bearing Clinical Computed Tomography

Accurate in vivo quantification of subtalar joint kinematics can provide important information for the clinical evaluation of subtalar joint function; the analysis of outcome of surgical procedures of the hindfoot; and the design of a replacement subtalar joint prosthesis. The objective of the current study was to explore the potential of full weight-bearing clinical computed tomography (CT) to evaluate the helical axis and centre of rotation of the subtalar joint during inversion and eversion motion. A subject specific methodology was proposed for the definition of the subtalar joint motion combining three-dimensional (3D) weight-bearing imaging at different joint positions with digital volume correlation (DVC). The computed subtalar joint helical axis parameters showed consistency across all healthy subjects and in line with previous data under simulated loads. A sphere fitting approach was introduced for the computation of subtalar joint centre of rotation, which allows to demonstrate that this centre of rotation is located in the middle facet of the subtalar joint. Some translation along the helical axis was also observed, reflecting the elasticity of the soft-tissue restraints. This study showed a novel technique for non-invasive quantitative analysis of bone-to-bone motion under full weight-bearing of the hindfoot. Identifying different joint kinematics in patients with ligamentous laxity and instability, or in the presence of stiffness and arthritis, could help clinicians to define optimal patient-specific treatments.

Reliability of distal tibio-fibular syndesmotic instability measurements using weightbearing and non-weightbearing cone-beam CT

BACKGROUND

To investigate the reliability and reproducibility of syndesmosis measurements on weightbearing (WB) cone-beam computed tomography (CBCT) images and compare them with measurements obtained using non-weightbearing (NWB) images.

METHODS

In this IRB-approved, retrospective study of 5 men and 9 women with prior ankle injuries, simultaneous WB and NWB CBCT scans were taken. A set of 21 syndesmosis measurements using WB and NWB images were performed by 3 independent observers. Pearson/Spearman correlation and intra-class correlation (ICC) were used to assess intra- and inter-observer reliability, respectively.

RESULTS

We observed substantial to perfect intra-observer reliability (ICC=0.72-0.99) in 20 measurements. Moderate to perfect agreement (ICC=0.45-0.97) between observers was noted in 19 measurements.

CONCLUSION

Measurements evaluating the distance between tibia and fibula in the axial plane 10mm above the plafond had high intra- and inter-observer reliability. Mean posterior tibio-fibular distance, diastasis, and angular measurement were significantly different between WB and NWB images.

Hindfoot alignment of adult acquired flatfoot deformity: A comparison of clinical assessment and weightbearing cone beam CT examinations

BACKGROUND

Clinical assessment of hindfoot alignment (HA) in adult acquired flatfoot deformity (AAFD) can be challenging and weightbearing (WB) cone beam CT (CBCT) may potentially better demonstrate this three-dimensional (3D) deformity. Therefore, we compared clinical and WB CBCT assessment of HA in patients with AAFD.

METHODS

In this prospective study, we included 12 men and 8 women (mean age: 52.2, range: 20-88) with flexible AAFD. All subjects also underwent WB CBCT and clinical assessment of hindfoot alignment. Three fellowship-trained foot and ankle surgeons performed six hindfoot alignment measurements on the CT images. Intra- and Inter-observer reliabilities were calculated using intra-class correlation (ICC). Measurements were compared by paired T-tests, and p-values of less than 0.05 were considered significant.

RESULTS

The mean of clinically measured hindfoot valgus was 15.2 (95% confidence interval [CI]: 11.5-18.8) degrees. It was significantly different from the mean values of all WB CBCT measurements: Clinical Hindfoot Alignment Angle, 9.9 (CI: 8.9-11.1) degrees; Achilles tendon/Calcaneal Tuberosity Angle, 3.2 (CI: 1.3-5.0) degrees; Tibial axis/Calcaneal Tuberosity Angle, 6.1 (CI: 4.3-7.8) degrees; Tibial axis/Subtalar Joint Angle 7.0 (CI: 5.3-8.8) degrees, and Hindfoot Alignment Angle 22.8 (CI: 20.4-25.3) degrees. We found overall substantial to almost perfect intra- (ICC range: 0.87-0.97) and inter-observer agreements (ICC range: 0.51-0.88) for all WB CBCT measurements.

CONCLUSIONS

Using 3D WB CBCT can help characterize the valgus hindfoot alignment in patients with AAFD. We found the different CT measurements to be reliable and repeatable, and to significantly differ from the clinical evaluation of hindfoot valgus alignment.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

Three-dimensional kinematic change of hindfoot during full weightbearing in standing: an analysis using upright computed tomography and 3D-3D surface registration

Background

Weightbearing of the hindfoot affects positional changes of the ankle joint and subtalar joint (ankle-joint complex [AJC]). However, it is difficult to assess the kinematic changes in the hindfoot in a natural full weightbearing condition using conventional CT or cone beam computed tomography (CT) due to limitations of acquiring foot images under a physiological weightbearing condition using those imaging modalities. Analysis of AJC kinematics using fluoroscopy and 2D-3D registration technique requires data on the number of steps and amount of time to build and match the bones. This study aimed to analyze the effect of full weightbearing on hindfoot motion when standing using upright CT and 3D-3D surface registration.

Methods

Forty-eight AJCs of 24 asymptomatic volunteers (13 women, 11 men) were examined under no weightbearing, 50% weightbearing, and single leg full weightbearing conditions while standing. The CT images were acquired from the distal femur to the whole foot using a 320-row upright CT scanner. The condition of each weightbearing stance was measured using a pressure mat. Bone-to-bone rotations of the talus relative to the tibia and calcaneus relative to the talus were evaluated using the surface registration technique. Image quality of the CT and intra- and interobserver reliabilities of the rotation angle were also evaluated.

Results

All CT images were excellent or good quality and the intra- and interobserver correlation coefficients for the angle were 0.996 and 0.995, respectively. The motion of the ankle joint and subtalar joint under 50% and 100% weightbearing were as follows (in degrees); the talus plantarflexed (5.1 ± 4.5 and 6.8 ± 4.8), inverted (1.3 ± 1.4 and 2.0 ± 1.6), and internally rotated (2.4 ± 4.2 and 4.3 ± 4.6) relative to the tibia, and the calcaneus dorsiflexed (2.8 ± 1.4 and 3.8 ± 1.7), everted (5.3 ± 2.6 and 8.0 ± 3.6), and externally rotated (3.0 ± 2.0 and 4.1 ± 2.4) relative to the talus, respectively.

Conclusions

The effect of weightbearing was clearly identified using an upright CT and the 3D-3D registration technique. Three-dimensional kinematics under static full weightbearing were opposite between the ankle and subtalar joints on their respective axes.

3D Biometrics for Hindfoot Alignment Using Weightbearing Computed Tomography

BACKGROUND

Weightbearing computed tomography (WBCT) is a useful tool for the assessment of hindfoot alignment (HA). Foot ankle offset (FAO) is a recently introduced parameter, determined from WBCT images using semiautomatic software. The aim of this study was to determine the clinical relevance and reproducibility of FAO for the evaluation of HA.

METHODS

A prospective comparative study was performed on consecutive patients requiring bilateral WBCT between September 2017 and April 2018. Based on the clinical assessment of HA, patients were divided into 3 groups: (1) normal alignment group (G1), (2) valgus (G2), and (3) varus (G3). FAO and long axial view (HACT) were measured on WBCT images, and the groups were compared. The reproducibility of FAO and HACT was determined through intraclass correlation coefficients (ICCs). Regression analysis was performed to investigate the correlation between the 2 methods. Overall, 249 feet (126 patients) were included (G1 = 115, G2 = 78, and G3 = 56 feet).

RESULTS

The mean values for FAO and HACT were 1.2% ± 2.8% and 3.9 ± 3.1, respectively, in G1; 8.1% ± 3.7% and 9.7 ± 4.9 in G2; and -6.6% ± 4.8% and -8.2 ± 6.6 in G3. Intra- and interobserver reliability was 0.987 and 0.988 for FAO and 0.949 and 0.949 for HACT, respectively. There was a good linear correlation between HACT and FAO ( R² = 0.744), with a regression slope of 1.064.

CONCLUSIONS

WBCT was a useful method for the characterization of HA. FAO was reproducible and correlated well with physical examination.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Foot Alignment in Symptomatic National Basketball Association Players Using Weightbearing Cone Beam Computed Tomography

Background:

Weightbearing cone beam computed tomography (WB CBCT) allows detailed 3-dimensional imaging of the foot and ankle in a weightbearing state and provides improved accuracy and reliability of foot alignment measures, especially when compared with conventional radiographic views.

Purpose:

To describe the foot alignment in National Basketball Association (NBA) players with different symptomatic foot and ankle injuries using WB CBCT and to determine if any predominant morphotype would be identified.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 45 active NBA players (mean age, 24.4 years [range, 20-34 years]; N = 54 feet [29 right, 25 left]) were assessed using WB CBCT. Measurements included the following: (1) foot and ankle offset (FAO), (2) calcaneal offset (CO), (3) hindfoot alignment angle (HAA), (4) angle between the inferior and superior facets of the talus (Inftal-Suptal), (5) angle between the inferior facet of the talus and the horizontal floor line (Inftal-Hor), (6) forefoot arch angle (FAA), (7) navicular-to-floor distance, and (8) medial cuneiform–to-floor distance. Measurements were then compared with values available in the literature for a “normal” foot morphotype.

Results:

Among the 54 feet, the mean FAO was 0.48% (95% CI, –0.25% to 1.21%), the mean CO was 1.18 mm (95% CI, –0.50 to 2.87 mm), and the mean HAA was 1.42° (95% CI, –0.80° to 3.65°). The mean Inftal-Suptal angle was 5.31° (95% CI, 3.50°-7.12°), while the mean Inftal-Hor angle was 4.04° (95% CI, 2.56°-5.51°). The mean FAA was 15.84° (95% CI, 14.73°-16.92°), the mean navicular-to-floor distance was 38.30 mm (95% CI, 36.19-40.42 mm), and the mean medial cuneiform–to-floor distance was 26.79 mm (95% CI, 25.30-28.28 mm). None of these values were found to be significantly different when comparing forwards, guards, and centers.

Conclusion:

NBA players presenting with symptomatic foot and ankle injuries had a fairly “normal” foot morphology, with a tendency toward a varus hindfoot and a high-arched morphotype. No significant differences were found between players based on their position on the court. WB CBCT may help to shed light on anatomic risk factors for common injuries in professional players and may aid in the planning of specific prevention programs.

Weight-bearing cone beam CT scans in the foot and ankle

The 3D anatomical complexity of the foot and ankle and the importance of weight-bearing in diagnosis have required the combination of conventional radiographs and medical CT.

Conventional plain radiographs (XR) have demonstrated substantial limitations such as perspective, rotational and fan distortion, as well as poor reproducibility of radiographic installations. Conventional CT produces high levels of radiation exposure and does not offer weight-bearing capabilities.

The literature investigating biometrics based on 2D XR has inherent limitations due to the technology itself and thereby can focus only on whether measurements are reproducible, when the real question is whether the radiographs are.

Low dose weight-bearing cone beam CT (WBCT) combines 3D and weight-bearing as well as ‘built in’ reliability validated through industry-standardized processes during production and clinical use (quality assurance testing).

Research is accumulating to validate measurements based on traditional 2D techniques, and new 3D biometrics are being described and tested.

Time- and cost-efficient use in medical imaging will require the use of automatic measurements. Merging WBCT and clinical data will offer new perspectives in terms of research with the help of modern data analysis techniques.

Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170066