Weightbearing CT Research Articles

Classification and Nomenclature: Progressive Collapsing Foot Deformity.

The historical nomenclature for the adult acquired flatfoot deformity (AAFD) is confusing, at times called posterior tibial tendon dysfunction (PTTD), the adult flexible flatfoot deformity, posterior tibial tendon rupture, peritalar instability and peritalar subluxation (PTS), and progressive talipes equinovalgus. Many but not all of these deformities are associated with a rupture of the posterior tibial tendon (PTT), and some of these are associated with deformities either primarily or secondarily in the midfoot or ankle. There is similar inconsistency with the use of classification schemata for these deformities, and from the first introduced by Johnson and Strom (1989), and then modified by Myerson (1997), there have been many attempts to provide a more comprehensive classification system. However, although these newer more complete classification systems have addressed some of the anatomic variations of deformities encountered, none of the above have ever been validated. The proposed system better incorporates the most recent data and understanding of the condition and better allows for standardization of reporting. In light of this information, the consensus group proposes the adoption of the nomenclature "Progressive Collapsing Foot Deformity" (PCFD) and a new classification system aiming at summarizing recent data published on the subject and to standardize data reporting regarding this complex 3-dimensional deformity. Level V, consensus, expert opinion. CONSENSUS STATEMENT ONE: We will rename the condition to Progressive Collapsing Foot Deformity (PCFD), a complex 3-dimensional deformity with varying degrees of hindfoot valgus, forefoot abduction, and midfoot varus.Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.(Unanimous, strongest consensus)CONSENSUS STATEMENT TWO: Our current classification systems are incomplete or outdated.Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.(Unanimous, strongest consensus)CONSENSUS STATEMENT THREE: MRI findings should be part of a new classification system.Delegate vote: agree, 33% (3/9); disagree, 67% (6/9); abstain, 0%.(Weak negative consensus)CONSENSUS STATEMENT FOUR: Weightbearing CT (WBCT) findings should be part of a new classification system.Delegate vote: agree, 56% (5/9); disagree, 44% (4/9); abstain, 0%.(Weak consensus)CONSENSUS STATEMENT FIVE: A new classification system is proposed and should be used to stage the deformity clinically and to define treatment.Delegate vote: agree, 89% (8/9); abstain, 11% (1/9).(Strong consensus).

Consensus for the Use of Weightbearing CT in the Assessment of Progressive Collapsing Foot Deformity.

There is evidence that the use of WEIGHTBEARING imaging aids in the assessment of progressive collapsing foot deformity (PCFD). The following WEIGHTBEARING conventional radiographs (CRs) are necessary in the assessment of PCFD patients: anteroposterior (AP) foot, AP or mortise ankle, and lateral foot. If available, a hindfoot alignment view is strongly recommended. If available, WEIGHTBEARING computed tomography (CT) is strongly recommended for surgical planning. When WEIGHTBEARING CT is obtained, important findings to be assessed are sinus tarsi impingement, subfibular impingement, increased valgus inclination of the posterior facet of the subtalar joint, and subluxation of the subtalar joint at the posterior and/or middle facet. Level V, consensus, expert opinion.

Change in the First Cuneiform-Second Metatarsal Distance After Simulated Ligamentous Lisfranc Injury Evaluated by Weightbearing CT Scans.

This study aimed to investigate the widening between the first cuneiform (C1) and second metatarsal (M2) in a Lisfranc ligamentous complex (LLC) joint injury model subjected to successive ligament dissections evaluated by weightbearing computed tomography (CT) scans. Twenty-four intact cadaveric feet served as the control (condition 1). Each component of the LLC (dorsal, interosseous, and plantar ligaments-conditions 2, 3, and 4, respectively) were then sequentially dissected. The specimens were equally randomized to 1 of 3 additional dissections (first or second tarsometatarsal [TMT] joint capsule or first-second intercuneiform ligament [ICL]-conditions 5a, 5b, and 5c, respectively). One additional ligament was then randomly transected (eg, condition 6ac-transection of the first TMT capsule and ICL). Finally, the remaining ligament was transected (condition 7). After each dissection, CT scans were acquired under nonweightbearing (NWB, 0 kg), partial-weightbearing (PWB, 40 kg), and full-weightbearing (FWB, 80 kg) conditions. The distance between the lateral border of C1 and the medial border of M2 was assessed to evaluate diastasis. Linear regressions with 95% CIs and converted q values were used to compare the measured data. No significant differences were found within the control. In condition 4, an average axial plane widening relative to control of 1.6 mm (95% CI, 1.5-1.8) and 2.1 mm (95% CI, 1.9-2.2) was observed under PWB and FWB. A coronal plane widening of 1.5 mm (95% CI, 1.3-1.6) and 1.9 mm (95% CI, 1.7-2.1) under PWB and FWB, respectively, was measured. A 95% CI of at least a 2-mm widening during PWB was demonstrated in 5c, 6ac, 6bc, and 7. Weightbearing computed tomography (WBCT) scans were used to detect ligamentous Lisfranc injuries in a cadaveric model. Relative axial widening greater than 1.5 mm under PWB conditions could indicate a complete LLC injury. Complete transection of the intercuneiform 1-2 ligament was required to detect a 2-mm widening in the nonweightbearing condition. This study provides insight on the detection of various severities of LLC injuries using WBCT imaging.

Hinge fracture in lateral closed-wedge distal femoral osteotomy in knees undergoing double-level osteotomy: assessment of postoperative change in rotational alignment using CT evaluation.

The purpose of this study was to examine the radiological features of hinge fracture occurring at the distal medial femoral cortex in knees undergoing biplanar lateral closed-wedge distal femoral osteotomy (LCW-DFO) in double-level osteotomy (DLO) based on pre- and postoperative CT image analyses. It was hypothesised that medial hinge fractures in LCW-DFO would occur with a similar incidence to that in high tibial osteotomy, and its occurrence would affect the clinical/radiological outcomes and induce unintended change in alignment depending on the fracture type (direction of the fracture). A consecutive series of 36 knees (31 patients) with primary varus osteoarthritis undergoing DLO comprised the study population. The mean age at surgery was 62.0 ± 5.9years. Presence of hinge fracture was assessed on radiographs and CT images at 1week. The fracture type was classified depending on the direction of the fracture line: crack propagation in line with the osteotomy (type 1) and fractures extending proximally (type 2) or distally (type 3) from the tip of the wedge. Computer-assisted assessments of bony limb alignment and bony geometry were conducted on a full-length weight-bearing radiograph and CT images using image analysis software. In addition, subjective clinical results were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Radiological and clinical follow-up results at 1 and 2years were compared to the preoperative data, while comparative analysis was made between the subjects with and without a hinge fracture. Postoperative image examinations revealed type 1 and 2 medial femoral hinge fractures in 4 and 7 knees, while no type 3 fracture was identified in the study population. Consequently, the overall incidence of the hinge fracture was 30.6% (11 of the 36 knees). Four of those 11 fractures (36.4%) could not be detected on plain radiographs. CT image analysis for three-dimensional bony geometry showed greater increase in internal rotation of the distal bony segment (increased femoral antetorsion by 9.5° on average) after surgery compared to the knees without a hinge fracture (P = 0.01). Clinical evaluation using the KOOS at 2years showed no significant difference between the groups with and without hinge fractures. In LCW-DFO, medial femoral hinge fractures occurred in 30.6% of the cases. Knees with type 1 hinge fracture exhibited significantly greater increase in femoral antetorsion as compared to those without hinge fracture. In this case series, postoperative weight-bearing protocol was delayed for knees with hinge fracture. Consequently, surgical results were not affected by the occurrence of hinge fracture for up to 2years. IV (case series).

3D imaging for hindfoot alignment assessment: a comparative study between non-weight-bearing MRI and weight-bearing CT.

The authors compared measurements of hindfoot alignment on MR imaging with weight-bearing CT (WB-CT) to establish the degree of correlation. Forty-seven feet in 44 patients had weight-bearing CT and MRI studies performed on the same day. Hindfoot alignment on MRI was assessed by two radiologists who calculated tibiocalcaneal angle (TCA) and calcaneofibular ligament angle (CFLA). On WB-CT, foot ankle offset (FAO), calcaneal offset (CO) and hindfoot angle (HA) were assessed by a senior Foot and Ankle Surgeon using dedicated software. Pearson correlation coefficient was used to evaluate the correlation between these measurements. The study group comprised 27 males and 17 females with a mean age of 45years (range 13-79years). A statistically significant positive correlation was identified between TCA on MRI and all measurements of hindfoot alignment on WB-CT (p = 0.001-0.005). The CFLA on MRI only had significant correlation with CO on WB-CT (p = 0.03). A significant negative correlation was observed between both MRI parameters (p < 0.001). A highly significant correlation between tibiocalcaneal angle on non-weight-bearing ankle MR imaging and hindfoot alignment measurements on weight-bearing CT was identified.

Comparison of External Torque to Axial Loading in Detecting 3-Dimensional Displacement of Syndesmotic Ankle Injuries.

Current imaging techniques try to quantify 3-dimensional displacement of syndesmotic ankle injuries using 2-dimensional measurements, which may obscure an exact diagnosis. Therefore, our aim was to determine 3-dimensional displacement of syndesmotic ankle injuries under load and torque using a weightbearing computed tomography (WBCT) and to assess the relation with previously established 2-dimensional measurements. Seven paired cadaver specimens were mounted into a radiolucent frame. WBCT scans were obtained to generate 3-dimensional models after different patterns of axial load (0 kg, 85 kg) combined with external torque (0, 10 Nm). Sequential imaging was repeated in ankles containing intact syndesmotic ligaments, sectioning of the anterior inferior tibiofibular ligament (AITFL; condition 1A), deltoid ligament (DL; condition 1B), combined AITFL+DL (condition 2), and AITFl+DL+interosseous membrane (condition 3). Reference anatomical landmarks were established relative to the intact position of the fibula to quantify displacement. A subsequent correlation analysis was performed between the obtained 2- and 3-dimensional measurements. Axial load increased lateral translation (mean = -0.9 mm, 95% confidence interval [CI]: 1.3, -0.1) significantly in condition 2 relative to the intact ankle (P < .05) but did not demonstrate other significant displacements. External torque increased displacement significantly in all directions (P < .05), except for dorsal translation of the fibula (P > .05). The highest displacement could be detected when external torque was applied in condition 3 and consisted of posterior translation (mean = -3.1 mm; 95% CI: -4.8, -2.7) and external rotation (mean = -4.7 degrees; 95% CI: -5.6, -2.9). Pearson correlation coefficients between the 2-dimensional and 3-dimensional measurements were moderate and ranged from 0.31 to 0.56 (P < .05). External torque demonstrated superiority over axial load in detecting syndesmotic ankle instability. Axial load increased lateral translation; however, differences were submillimeter in magnitude until torque was applied. A moderate correlation was found with previously established 2-dimensional measurements. In clinical practice these findings substantiate application of external torque in current imaging modalities to improve detection of syndesmotic ankle injuries.

Impact of Coleman Block Test on Adult Hindfoot Alignment Assessed by Clinical Examination, Radiography, and Weight-Bearing Computed Tomography.

Background:Cavovarus foot constitutes a complex 3-dimensional deformity. The Coleman block test has traditionally been used to distinguish between forefoot- and hindfoot-driven deformity. However, there has been no objective evaluation of the Coleman block test using radiographs or weightbearing computed tomography (WBCT). The purpose of this study was to compare hindfoot alignment in adult cavovarus feet with and without the Coleman block using clinical examination, radiography, and WBCT.Methods:Six feet in 6 patients with a clinical diagnosis of cavovarus foot deformity were prospectively enrolled. All feet underwent clinical photography with the camera positioned at 0 degrees to the heel, hindfoot alignment view radiography with the beam positioned 20 degrees off the ground, and WBCT, both with and without the Coleman block in place. Clinical photos were characterized using the standing talocalcaneal angle (STCA), radiographs were characterized using the hindfoot alignment angle (HAA), and WBCTs were characterized using manual and automated hindfoot alignment angle (HAA) and foot and ankle offset (FAO). Using paired analyses, measurements taken with the Coleman block in place were compared to those taken without the Coleman block. Finally, the different methods of measuring hindfoot alignment were tested for correlation with each other. Mean age was 56 years (range 38-69).Results:On clinical photography, the STCA decreased by 3.8 degrees with addition of the block (from 10.0±6.6 degrees varus without block to 6.2±7.1 degrees varus with block; P = .001). On radiograph, HAA decreased by 9.0 degrees with addition of the block (from 16.8±8.4 degrees varus without block to 7.5±6.3 degrees varus with block; P = .07). On WBCT, hindfoot alignment angle changed an average of 3.2 degrees (33.4 degrees varus without block, 30.2 degrees varus with block; P = .008). On WBCT, FAO decreased by 1.4% (from 11.3% varus without block to 10.1% varus with block; P = .003). Clinical examination and automated WBCT measurements were strongly correlated with each other.Conclusion:Clinical examination, radiograph, and WBCT demonstrated improvements in hindfoot varus using the Coleman block test in adults, but no patient demonstrated complete resolution of deformity regardless of the measurement modality. Clinical examination correlated strongly with automated WBCT measurements.Level of Evidence:Level IV, retrospective case review.

Assessment of Posterior and Middle Facet Subluxation of the Subtalar Joint in Progressive Flatfoot Deformity.

Adult acquired flatfoot deformity (AAFD) is a complex 3-dimensional pathology characterized by peritalar subluxation (PTS) of the hindfoot. For many years, PTS was measured at the posterior facet of the subtalar joint. More recently, subluxation of the middle facet has been proposed as a more accurate and reliable marker of symptomatic AAFD, enabling earlier detection. The objective of this study was to compare the amount of subluxation between the medial and posterior facets in patients with AAFD. In this institutional review board-approved retrospective comparative study, a total of 76 patients with AAFD (87 feet) who underwent standing weightbearing computed tomography (WBCT) as a standard baseline assessment of their foot deformity were analyzed. Two blinded fellowship-trained orthopedic foot and ankle surgeons with >10 years of experience measured subtalar joint subluxation (as a percentage of joint uncoverage) at the both posterior and middle facets. One of the readers also measured the foot and ankle offset (FAO). PTS measurements were performed at the sagittal midpoint of the articular facets using coronal plane WBCT images. Intra- and interobserver agreement was measured for PTS measurements using the intraclass correlation coefficient (ICC). The intermethod agreement between the posterior and middle facet subluxation was assessed using Spearman's correlation and bivariate analysis. Paired comparison of the measurements was performed using the Wilcoxon test. A multivariate analysis and a partition prediction model were used to assess influence of PTS measurements on FAO values. P values of <.05 were considered significant. ICCs for intra- and interobserver reliabilities were 0.97 and 0.93, respectively, for posterior and 0.99 and 0.97, respectively, for middle facet subluxation. The intermethod Spearman's correlation between subluxation of the posterior and middle facets was measured at 0.61. In a bivariate analysis, both measurements were found to be significantly and linearly correlated (P < .0001; R2 = 0.42). Measurements of middle facet subluxation were found to be significantly higher than those for posterior facet subluxation, with a median difference (using the Hodges-Lehman factor) of 17.7% (P < .001; 95% CI, 10.9%-23.6%). We also found that for every 1% increase in posterior facet subluxation there was a corresponding 1.6-fold increase in middle facet subluxation. Only middle facet subluxation measurements were found to significantly influence FAO calculations (P = .003). The partition prediction model demonstrated that a middle facet subluxation value of 43.8% represented an important threshold for increased FAO. This study is the first to compare WBCT measurements of subtalar joint subluxation at the posterior and middle facets as markers of PTS in patients with AAFD. We found a positive linear correlation between the measurements, with subluxation of the middle facet being significantly more pronounced than that of the posterior facet by an average of almost 18%. This suggests that middle facet subluxation may provide an earlier and more pronounced marker of progressive PTS in patients with AAFD. Level III, retrospective comparative cohort study.

Results from more than 13,000 Weight-Bearing CT scans over 6.8 years. Impact on costs, radiation exposure and time spent

BackgroundThe purpose of this study was to assess the benefit of using Weight-Bearing CT (WBCT) instead of radiographs (R) and/or CT in a foot and ankle center regarding time spent for image acquisition, radiation dose, and cost effectiveness. Material and MethodsAll patients who obtained WBCT (PedCAT) from July 1, 2013 until March 15, 2020 were included in the study. Age, sex, primary pathology were analyzed. All parameters were compared between the time period using WBCT (yearly average) with the parameters from 2012, i.e. before availability of WBCT. The time spent for image acquisition (T) and radiation dose (RD) was calculated based on measured values from previous studies. For analysis cost effectiveness, device cost, reimbursement and working time cost of radiology technicians were taken into consideration within the local circumstances. Results13,156 WBCT scans were obtained in 5,798 patients (5,798 (44%) before treatment; 7,358 (56%) follow-up; mean age, 52.2; 46% male). Primary pathologies were forefoot deformities (n=1,189 (21%) and ankle instability/cartilage defect (n=832 (14%)), and hindfoot deformity (n=765 (13%)). 1,935 WBCT scans were obtained on average yearly, and 10.2 CTs (WBCT group). In 2012, 1,850 R and 254 CTs were obtained (R(+CT) group). Yearly RD was 4.3 uSv for WBCT group and 4.8 uSv for R(+CT) group (difference 0.5 uSv decrease with WBCT 10%, p<0.01). Yearly T was 113hours in total (3.5minutes per patient) for WBCT group and 493hours in total (16.0minutes per patient) for R(+CT) group (difference, 380hours, decrease with WBCT, 77%, p<0.01). Yearly profit was 53,543 Euro for WBCT group, -723 Euro for R(+CT) group. Conclusions13,156 WBCT scans in 5,798 patients as substitution of R(+CT) over a 6.8 year period at a foot and ankle center resulted in 10% decreased RD (minus 0.5 uSV on average per patient). Yearly T decreased 380hours (77%) in total (12.0minutes per patient). Yearly financial income increased more than 54,000 Euro in total (58 Euro per patient). RD decreased despite higher radiation dose for WBCT than for R alone, based on substitution of a high number of CTs by WBCT. Other centers with low usage of CT might not decrease RD by substituting R alone by WBCT.

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

IntroductionThe 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. MethodsIn 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. ResultsIn 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. ConclusionDistance 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 evidenceLevel III, case-control study.

Reliability of measurements assessing the Lisfranc joint using weightbearing computed tomography imaging.

Subtle Lisfranc joint injuries remain challenging to diagnose in clinical practice. Although of questionable accuracy, bilateral weightbearing radiographs are considered the current gold standard to assess these injuries. However, weightbearing computed tomography (WBCT), which provides clearer visualization of bony landmarks, can also be used for evaluation. This study aims to design a protocol that reliably measures the distance between the medial cuneiform (C1) and second metatarsal (M2) to assess the Lisfranc joint using WBCT imaging. Two unique methods of measuring the C1-M2 distance were designed that localize the center of the interosseous Lisfranc ligament (ILL, reference point). This reference point was located by (I) measuring a specific distance at the M2 base, or (II) approximating from nearby bony landmarks, on both axial (Ax) and coronal (Cor) WBCT images. Four parameters (I-Ax, I-Cor, II-Ax, and II-Cor) were evaluated for each of 96 specimens. Measurements were recorded by three independent observers and repeated for inter- and intra-observer agreement. In total, 96 patient image series were included and assessed in our study with an average age of 46 (19-66, SD 16.1) and average BMI of 25.8 (17.8-30.5, SD 4.3). I-Ax showed excellent agreement for intra-observer evaluation (R = 0.802) and good agreement for inter-observer evaluation (R = 0.727). I-Cor demonstrated excellent inter- (R = 0.814) and intra-observer (R = 0.840) agreement. Good agreement was found for both II-Ax and II-Cor for both intra- (R = 0.730, R = 0.708) and inter-observer (R = 0.705, R = 0.645) evaluation. Measuring the C1-M2 joint space with coronal WBCT imaging through a protocol that localizes the ILL is reproducible, simple, and can potentially be utilized clinically to evaluate the Lisfranc joint.

Asymmetric lambda sign of the second tarsometatarsal joint on axial weight-bearing cone-beam CT scans of the foot: preliminary investigation for diagnosis of subtle ligamentous Lisfranc injuries in a cadaveric model.

Subtle Lisfranc joint injuries remain challenging to diagnose. Although of questionable accuracy, the current gold standard to assess these injuries is through bilateral weight-bearing radiography. However, weight-bearing cone beam-computed tomography (CBCT), providing clearer visualization of bony landmarks, can also be utilized for evaluation. This study aims to establish the hypothesis that a specific weight-bearing CBCT finding (asymmetric lambda sign) can serve as an independent indicator of a subtle Lisfranc injury. Weight-bearing CBCT images of 24 match-paired cadaveric legs were acquired, initially intact, and then following sequential dissection of each aspect (dorsal, interosseous, and plantar ligaments, respectively) of the Lisfranc ligamentous complex (LLC). All scans were taken in non- (NWB, 0kg), partial- (PWB, 40kg), and full-weight-bearing (FWB, 80kg) manners. The lambda sign was then inspected axially for asymmetry (positive sign) by identifying three symmetrical joint spaces created between the medial cuneiform and the second metatarsal base (C1-M2), the medial and middle cuneiform (C1-C2), and the second metatarsal base and middle cuneiform (M2-C2). A positive sign was observed in 25.6% (221/864) of all studies. Most notably, the fully dissected specimens demonstrated an asymmetric lambda sign in 33.3%, 72.2%, and 83.3% in NWB, PWB, and FWB conditions, respectively. The inter- and intra-observer reliability kappa value was calculated to be 0.843 and 0.912. An asymmetric lambda sign is a simple and useful indicator for a complete LLC injury in PWB and FWB conditions using a cadaver model.

Weight-bearing radiographs and cone-beam computed tomography examinations in adult acquired flatfoot deformity

BackgroundOptimal characterization of Adult acquired flatfoot deformity (AAFD) on two-dimensional radiograph can be challenging. Weightbearing Cone Beam CT (CBCT) may improve characterization of the three-dimensional (3D) structural details of such dynamic deformity. We compared and validated AAFD measurements between weightbearing radiograph and weightbearing CBCT images. Methods20 patients (20 feet, right/left: 15/5, male/female: 12/8, mean age: 52.2) with clinical diagnosis of flexible AAFD were prospectively recruited and underwent weightbearing dorsoplantar (DP) and lateral radiograph as well as weightbearing CBCT. Two foot and ankle surgeons performed AAFD measurements at parasagittal and axial planes (lateral and DP radiographs, respectively). Intra- and Inter-observer reliabilities were calculated by Intraclass correlation (ICC) and Cohen’s kappa. Mean values of weightbearing radiograph and weightbearing CBCT measurements were also compared. ResultsExcept for medial-cuneiform-first-metatarsal-angle, adequate intra-observer reliability (range:0.61−0.96) was observed for weightbearing radiographic measurements. Moderate to very good interobserver reliability between weightbearing radiograph and weightbearing CBCT measurements were observed for the following measurements: Naviculocuneiform-angle (ICC:0.47), Medial-cuneiform-first-metatarsal-gapping (ICC:0.58), cuboid-to-floor-distance (ICC:0.68), calcaneal-inclination-angle(ICC:0.7), axial Talonavicular-coverage-angle(ICC:0.56), axial Talus-first-metatarsal-angle(ICC:0.62). Comparing weightbearing radiograph and weightbearing CBCT images, statistically significant differences in the mean values of parasagittal talus-first-metatarsal-angle, medial-cuneiform-first-metatarsal-angle, medial-cuneiform-to-floor-distance and navicular-to-floor-distance was observed (P < 0.05). ConclusionModerate to very good correlation was observed between certain weightbearing radiograph and weightbearing CBCT measurements, however, significant difference was observed between a number of AAFD measurements, which suggest that 2D radiographic evaluation could potentially underestimate the severity of AAFD, when compared to 3D weightbearing CT assessment.

Weight Bearing CT and Relative Orientation of Foot Bones: Effect of Loading and Heeled Shoes

The purpose of this article is to determine the orientation and relative position of the foot bones in Weight Bearing CT, highlighting the effect of the load and the shoe with the heel. Thanks to a Cone Beam CT (OnSight 3D Extremity System, Carestream) equipment, three scans of the foot of a healthy young subject were carried out in three conditions: "unloading", "loading", and wearing a shoe with "heel". In order to assess the accuracy of the articular angles of the foot through non-invasive measurements, a measurement was performed by Gait-Analysis with passive markers in the same conditions. The effect of the "load" resulted in a significant alteration of the foot posture especially in the sagittal plane, with crushing of the longitudinal medial arch. The heeled shoe involves enormous deformations at the level of the metatarsophalangeal joints and the ankle.

Weight Bearing CT and Relative Orientation of Foot Bones: Effect of Loading and Heeled Shoes

The purpose of this article is to determine the orientation and relative position of the foot bones in Weight BearingCT, highlighting the effect of the load and the shoe with the heel. Thanks to a Cone Beam CT (OnSight 3D ExtremitySystem, Carestream) equipment, three scans of the foot of a healthy young subject were carried out in three conditions:“unloading”, “loading”, and wearing a shoe with “heel”. In order to assess the accuracy of the articular angles ofthe foot through non-invasive measurements, a measurement was performed by Gait-Analysis with passive markers inthe same conditions. The effect of the “load” resulted in a significant alteration of the foot posture especially in thesagittal plane, with crushing of the longitudinal medial arch. The heeled shoe involves enormous deformations at thelevel of the metatarsophalangeal joints and the ankle.

Pes cavovarus in Charcot-Marie-Tooth compared to the idiopathic cavovarus foot: A preliminary weightbearing CT analysis

BackgroundPes cavovarus is a foot deformity that can be idiopathic (I-PC) or acquired secondary to other pathology. Charcot-Marie-Tooth disease (CMT) is the most common adult cause for acquired pes cavovarus deformity (CMT-PC). The foot morphology of these distinct patient groups has not been previously investigated. The aim of this study was to assess if morphological differences exist between CMT-PC, I-PC and normal feet (controls) using weightbearing computed tomography (WBCT). MethodsA retrospective analysis of WBCT scans performed between May 2013 and June 2017 was undertaken. WBCT scans from 17 CMT-PC, 17 I-PC and 17 healthy normally-aligned control feet (age-, side-, sex- and body mass index-matched) identified from a prospectively collected database, were analysed. Eight 2-dimensional (2D) and three 3-dimensional (3D) measurements were undertaken for each foot and mean values in the three groups were compared using one-way ANOVA with the Bonferroni correction. ResultsSignificant differences were observed between CMT-PC or I-PC and controls (p<0.05). Two-dimensional measurements were similar in CMT-PC and I-PC, except for forefoot arch angle (p=0.04). 3D measurements (foot and ankle offset, calcaneal offset and hindfoot alignment angle) demonstrated that CMT-PC exhibited more severe hindfoot varus malalignment than I-PC (p=0.03, 0.04 and 0.02 respectively). ConclusionsCMT-related cavovarus and idiopathic cavovarus feet are morphologically different from healthy feet, and CMT feet exhibit increased forefoot supination and hindfoot malalignment compared to idiopathic forms. The use of novel three-dimensional analysis may help highlight subtle structural differences in patients with similar foot morphology but aetiologically different pathology. Level of evidenceLevel III, retrospective comparative study.

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

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

A Comparison Between X-ray Imaging and an Innovative Computer-aided Design Method Based on Weightbearing CT Scan Images for Assessing Hallux Valgus

With the development of recent technology, radiographs can be saved digitally, and angular measurements can be processed using various software packages. We developed an innovative computer-aided design method with Materialize Interactive Medical Image Control System software to measure hallux valgus angle (HVA), the intermetatarsal angle (IMA), and the distal metatarsal articular angle (DMAA) and assessed its concordance with traditional X-ray imaging methods. All measurements were carried out on 42 feet from 26 adult patients diagnosed with hallux valgus who were prospectively selected from July 2016 to April 2018. Standing X-ray radiograph and weightbearing computed tomography scans were conducted on all patients, and HVA, IMA, and DMAA were generated using both a traditional X-ray method and our innovative method. Two different observers assessed measurements for each patient. Finally, statistical analyses were conducted to assess the reliability of the measurements. Both X-ray imaging and our innovative method had strong interobserver and test-retest reliability. The ICC of X-ray imaging was 0.945, p < .001, and the ICC of the innovative method was 0.915, p < .001. There was no statistical difference between the 2 methods for HVA and IMA measurements (p > .05); however, a difference was detected for DMAA (p < .05). Bland-Altman analyses demonstrated a high degree of agreement between the 2 methods for HVA and IMA, but a significant difference for DMAA. From the results, we concluded that our innovative computer-aided design method is a feasible, reliable way to quantitatively assess HVA, IMA, and DMAA, and it is likely more accurate for measuring DMAA.

Screw Versus Suture Button in Treatment of Syndesmosis Instability: Clinical and Radiographic Outcomes Using PROMIS and Weight Bearing CT Scan

Category:Trauma; Ankle; SportsIntroduction/Purpose:Traumatic injuries to the distal tibiofibular syndesmosis are relatively common and can be associated with ankle fractures or occur as purely ligamentous injuries. Unstable syndesmotic injuries require surgical repair, generally performed using either screw or suture button fixation. The superiority of either fixation method remains a subject of ongoing debate. The aim of this study is to compare both clinical and radiographic outcomes of screw and suture button fixation of syndesmosis instability using Patient-Reported Outcomes Measurement Information System (PROMIS) and weight bearing CT scan (WBCT).Methods:Medical records were reviewed to identify patients who had a unilateral syndesmotic injury requiring surgical stabilization and who were at least one year out from injury. Exclusion criteria included patients less than 18 years old, ipsilateral pilon fracture, history of contralateral ankle or pilon fracture or syndesmosis injury, BMI >40, and any neurological impairment. Twenty eligible patients were recruited to complete PROMIS questionnaires and undergo bilateral WBCT scan of both ankles, divided into two groups. In the first group (n=10) the patients had undergone screw fixation of the syndesmosis, while in the second group (n=10) the syndesmosis was fixed using a suture button construct. All patients completed PROMIS questionnaires for pain intensity, pain interference, physical function and depression. Radiographic assessment was performed using axial images of WBCT scan of both the injured ankle and the contralateral normal side at a level one cm proximal to the tibial plafond (Figure 1).Results:At an average follow up of three years, none of the recruited patients required a revision surgery. There was no significant difference between the two groups in terms of the four PROMIS questionnaires (P values ranged from 0.17 to 0.43). In the suture button group, the measurements of the injured side were significantly different from the normal side for the syndesmotic area (P=0.003), fibular rotation (P=0.004), anterior difference (P=0.025) and direct anterior difference (P=0.035).Other measurements of posterior difference, middle difference, direct posterior difference and fibular translation were not significantly different (P values ranged from 0.36 to 0.99). In the screw fixation group, the syndesmotic area was the only significantly different measurement in the injured side as compared to the normal side (P=0.006).Conclusion:Screw and suture button fixation for syndesmotic instability have similar clinical outcomes at average three years follow up as measured by PROMIS scores. Both screw and suture button did not entirely restore the syndesmotic area as compared to the contralateral normal ankle, suggesting some residual diastasis on weight bearing CT. In addition, as compared to screw fixation, the suture button did not seem to restore the normal fibular rotation, with residual external rotation of the fibula noted. Longer clinical follow up is necessary to understand the clinical implication of such malreduction.

Change in the C1-M2 Distance after Simulated Purely Ligamentous Lisfranc Injury as Evaluated by Weightbearing CT Scans: A Match-Paired Cadaveric Study

Category:Trauma; Midfoot/ForefootIntroduction/Purpose:Introduction: The incidence of Lisfranc injury is higher than previously estimated, and more than two- thirds of these injuries are caused by low-energy trauma. This low-energy mechanism, common to the athletic population, tends to be distinctly characterized by a primarily ligamentous Lisfranc injury. Bilateral weightbearing radiographs are widely accepted as the gold standard and are able to diagnose instability by contralateral comparison. However, contrary to radiography, CT imaging is not obscured by metatarsals overlapping each other and their adjacent tarsal bone and thus provides a better visualization of bony structure. This study’s purpose was to model a purely ligamentous Lisfranc joint injury to determine widening between the medial cuneiform (C1) and second metatarsal (M2) after each ligament dissection under non-weightbearing (NWB, 0 kg), partial weightbearing (PWB, 40 kgs.), and full weightbearing (FWB, 80 kgs.) conditions evaluated by weightbearing computed tomography (WBCT).Methods:Methods: Twelve paired through-knee cadavers were incised dorsally to visualize the Lisfranc joint complex. An intact ligament condition was the control (group 1). The dorsal ligament (group 2), interosseous ligament (group 3), and plantar ligament (group 4) were sequentially dissected. The twelve pairs were then equally randomized (groups 5a, 5b, and 5c). The first tarsometatarsal joint capsule (group 5a), the second tarsometatarsal joint capsule (group 5b), or the intercuneiform ligament (group 5c) was transected. The remaining intact ligaments of each subgroup were similarly randomized for transection (e.g., group 6ac: transection of the first tarsometatarsal joint, followed by transection of the intercuneiform ligament). Finally, the last ligament was transected (group 7). After each dissection, CT scans were taken for NWB, PWB, and FWB conditions. Distance between the lateral border of C1 and the medial border of M2 was used to evaluate diastasis for both coronal and axial views. Analysis of variance (ANOVA) tested for significant differences between all groups. Dependent t-test evaluated for significance of the weightbearing variable.Results:In group 1, C1-M2 distance was 3.9 mm (3.5-4.3, SD 0.3) for coronal imaging and 4.0 mm (3.6-4.5, SD 0.4) for axial imaging, and no statistically significant differences were found between paired feet (P = 0.61) or for weightbearing conditions (P = 0.34). In group 4, an average widening of 1.4-mm (0.8-2.1 mm, SD 0.4) and 1.8-mm (1.4-2.8 mm, SD 0.5) were observed for PWB and FWB in the coronal view, and an average widening of 1.5-mm (0.9-2.3 mm, SD 0.5) and 2.0-mm (1.4-3.0 mm, SD 0.5) were observed for PWB and FWB in the axial view, respectively. For the subsets of group 5, only 5c was found to have a majority of specimen (7/8, 87.5%) that had significant widening - at least 2 mm - between C1-M2 for the PWB condition in the axial view; for the FWB condition, significant widening was found in both the axial and coronal view. In groups 6ca, 6cb, and 7, a significant widening - at least 2 mm - was measured in both planes for the NWB condition.Conclusion:WBCT scans improve the ability to detect incomplete ligamentous Lisfranc injuries by comparing C1-M2 distance to the uninjured side. Widening exceeding 1 mm more than the normal contralateral side for the PWB condition could clinically indicate complete Lisfranc ligament injury (sensitivity 83.3%, specificity 88.9%, accuracy 87.5%).