Weightbearing CT Images Research Articles

Three-Dimensional Assessment to Hallux Valgus Correction Using Lapicotton Technique

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: The first-ray and the medial column play a crucial role in preserving the tripod of the foot. Changes to structural properties of the first-ray, along with collapse of the medial-longitudinal-arch, have been associated with hallux valgus (HV). Thus, restoring the first-ray plays an important role when correcting the mechanical function of the foot tripod in the setting of HV combined with medial-longitudinal-arch collapse. The LapiCotton technique combines the mechanical advantages of Cotton osteotomy and modified Lapidus procedures by maintaining the length of the first-ray and preserving the medial- longitudinal-arch by plantar inclination of the distal part of first-ray. The aim of this study was to evaluate the effectiveness of the LapiCotton procedure in correcting selected radiographic parameters in patients with combined VH with medial-longitudinal arch collapse. Methods: Preoperative and postoperative Weight Bearing CT (WBCT) scans were obtained from HV patients who underwent unilateral LapiCotton procedure. Postoperative scans were obtained roughly three months after the date of surgery. Semi- automatic measurements were applied to 22 WBCT images across a total of 11 patients enrolled into the study using the Disior® Bonelogic® Software. Measurements of the hallux valgus angle (HVA), meary sagittal measurement, and intermetatarsal angles were taken from preoperative and postoperative scans. These scans were then compared using intraclass correlation coefficients and paired t-tests to evaluate the efficacy of the Lapicotton technique in treating HV with P-valus < 0.05 being significant. Results: HVA was found to be significantly larger (p=.026) in the preoperational group (Mdn = 27.52) than the postoperational group (Mdn = 20). In addition, the Meary sagittal measurement was found to be significantly different between groups (p=.033), with a larger value seen in the preoperational group (Mdn = -14.28) compared to the post-operational group (Mdn = -11.15). It was also observed that the IMA was significantly larger (p=.003) in the preoperative group (Mdn = 15.68) compared to the postoperative group (Mdn = 11.26). The sesamoid rotation was found to be higher in the preoperative group (Mdn = -17.71) than the post operative group (Mdn = -24.98), however, these values were not significantly different from one another (p=.203). Conclusion: The LapiCotton procedure proved to be effective in correcting radiographic parameters in patients with HV combined with collapse of the medial longitudinal arch. Reliable correction of HV, along with correction of medial longitudinal arch collapse, was quantified based on semi-automated WBCT measurements of HVA, IMA and Meary angle. LapiCotton produced significantly different measurements for both HVA and IMA postoperatively, providing evidence that the LapiCotton procedure can successfully correct medial longitudinal arch collapse in patients with HV, as well as radiographically reduce the severity of the deformity.

A Comparison of Imaging Outcomes From 2 Weightbearing CT Modalities.

The use of weightbearing images to diagnose foot and ankle injuries continues to offer hope for improved insight into pathologies, but weightbearing CT imaging has been limited by availability. The ability to apply force to the lower limb in a horizontal bore CT system may offer an adaptation to currently available imaging systems that provides access to weightbearing images without the acquisition of additional expensive imaging space or equipment. In order to determine whether a horizontal CT system could produce the same results as a standing CT, 3 images of one foot from 10 subjects was obtained and standard measures were calculated. Each subject underwent a standing CT scan, a scan in a horizontal bore CT machine while the subject pressed against a pedal with spring resistance and a finally a scan with the foot placed on the pedal but without any pressure. No statistically significant difference between the standing and pedal-based CTs resulted. Navicular height and Meary angle (axial) were statistically different from nonweightbearing for both standing and horizontal systems. The horizontal results were statistically different from nonweightbearing in IM angle, talocalcaneal angle, and talonavicular coverage. No differences from nonweightbearing were found for either system in talar tilt, talocrural angle, or the lateral Meary angle. The results in this initial study of normal control subjects suggest that a pedal-based loading mechanism may adapt a horizontal-bore CT system for the acquisition of weightbearing images. The ability to acquire a weightbearing CT from a horizontal bore CT machine can make these images more available.

Application of external torque enhances the detection of subtle syndesmotic ankle instability in a weight-bearing CT.

Acute syndesmotic ankle injuries continue to impose a diagnostic dilemma and it remains unclear whether weightbearing and/or external rotation should be added during the imaging process. Therefore, the aim of this study was to assess if combined weightbearing and external rotation increases the diagnostic sensitivity of syndesmotic ankle instability using weightbearing CT (WBCT) imaging, compared to isolated weightbearing. In this retrospective study, patients with an acute syndesmotic ankle injury were analysed using a WBCT (N = 21; Age = 31.6 ± 14.1years old). Inclusion criteria were an MRI confirmed syndesmotic ligament injury imaged by a WBCT of the ankle during weightbearing and combined weightbearing-external rotation. Exclusion criteria consisted of fracture associated syndesmotic injuries. Three-dimensional (3D) models were generated from the CT slices. Tibiofibular displacement and talar rotation were quantified using automated 3D measurements (anterior tibiofibular distance (ATFD), Alpha angle, posterior Tibiofibular distance (PTFD) and Talar rotation (TR) angle in comparison to the contralateral non-injured ankle. The difference in neutral-stressed Alpha angle and ATFD showed a significant difference between patients with a syndesmotic ankle lesion and contralateral control (P = 0.046 and P = 0.039, respectively). The difference in neutral-stressed PTFD and TR angle did not show a significant difference between patients with a syndesmotic ankle lesion and healthy ankles (n.s.). Application of combined weightbearing-external rotation reveals an increased ATFD in patients with syndesmotic ligament injuries. This study provides the first insights based on 3D measurements to support the potential relevance of applying external rotation during WBCT imaging. In clinical practice, this could enhance the current diagnostic accuracy of subtle syndesmotic instability in a non-invasive manner. However, to what extent certain displacement patterns require operative treatment strategies has yet to be determined in future studies. Level III.

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

ObjectivesWe present a 3-D approach to joint space width (JSW) measurement across the ankle from weight-bearing CT (WBCT) to demonstrate inter-operator reproducibility, test-retest repeatability, and how differences in angulation affect ankle JSW distribution.MethodsOne side from repeat WBCT imaging of both feet and ankles was analysed from 23 individuals as part of their routine clinical care pathway. Joint space mapping was performed at four facets across the talus: talonavicular, talar dome and medial gutter (dome-medial), lateral gutter, and posterior subtalar. Inter-operator reproducibility was calculated for two users, while test-retest repeatability was calculated by comparing the two visits, both presented as Bland-Altman statistics. Statistical parametric mapping determined any significant relationships between talocrural joint space angulation and 3-D JSW distribution.ResultsThe average ± standard deviation interval between imaging was 74.0 ± 29.6 days. Surface averaged bias ± limits of agreement were similar for reproducibility and repeatability, the latter being: talonavicular 0.01 ± 0.26 mm, dome-medial 0.00 ± 0.28 mm, lateral gutter − 0.02 ± 0.40 mm, and posterior subtalar 0.02 ± 0.34 mm. Results are presented as 3-D distribution maps, with optimum test–retest repeatability reaching a smallest detectable difference of ± 0.15 mm.ConclusionsJoint space mapping is a robust approach to 3-D quantification of JSW measurement, inter-operator reproducibility, and test–retest repeatability at the ankle, with sensitivity reaching a best value of ± 0.15 mm. Standardised imaging protocols and optimised metal artefact reduction will be needed to further understand the clinical value of these 3-D measures derived from WBCT.Clinical relevance statementWeight-bearing computed tomography is an increasingly important tool in the clinical assessment of orthopaedic ankle disorders. This paper establishes the performance of measuring 3-D joint space width using this technology, which is an important surrogate marker for severity of osteoarthritis.Key Points• Joint space width values and error metrics from across the ankle measured from weight-bearing CT can be presented as 3-D maps that show topographic variation.• The best sensitivity for detecting meaningful change in 3-D joint space width at the ankle was ± 0.15 mm, a value less than the isotropic imaging voxel dimensions.• Standardised imaging protocols and optimised metal artefact reduction will be needed to understand the clinical value of 3-D measures from weight-bearing CT.

Axial Plane Rotation of the Talus in Progressive Collapsing Foot Deformity: A Weightbearing Computed Tomography Analysis.

Progressive collapsing foot deformity (PCFD) is recognized as a 3-dimensional deformity centered around the talus. Previous studies have described some features of talar motion in the ankle mortise in PCFD, such as sagging in the sagittal plane or valgus tilt in the coronal plane. However, axial plane alignment of the talus in the ankle mortise in PCFD has not been investigated extensively. The purpose of this study was to examine this axial plane alignment of PCFD vs controls using weightbearing computed tomography (WBCT) images and to determine if talar rotation in the axial plane is associated with increased abduction deformity, as well as to assess the medial ankle joint space narrowing in PCFD that may be associated with axial plane talar rotation. Multiplanar reconstructed WBCT images of 79 patients with PCFD and 35 control patients (39 scans) were retrospectively analyzed. The PCFD group was divided into 2 subgroups depending on preoperative talonavicular coverage angle (TNC): moderate abduction (TNC 20-40 degrees, n=57) and severe abduction (TNC >40 degrees, n=22). Using the transmalleolar (TM) axis as a reference, the axial alignment of the talus (TM-Tal), calcaneus (TM-Calc), and second metatarsal (TM-2MT) were calculated. Difference between TM-Tal and TM-Calc was calculated to examine talocalcaneal subluxation. A second method to assess talar rotation within the mortise utilized an angle between the lateral malleolus and the talus (LM-Tal) in the axial slices of WBCT. In addition, the prevalence of medial tibiotalar joint space narrowing was assessed. These parameters were compared between the control and PCFD groups, and between moderate and severe abduction groups. The talus was significantly more internally rotated with respect to the ankle TM axis and the lateral malleolus in PCFD patients compared to controls, and in the severe abduction group compared with the moderate abduction group, using both measurement methods. Axial calcaneal orientation did not differ between groups. There was significantly greater axial talocalcaneal subluxation in the PCFD group, and this was also greater in the severe abduction group. The prevalence of medial joint space narrowing was higher in PCFD patients. Our findings suggest that talar malrotation in the axial plane should be considered an underlying feature of abduction deformity in PCFD. The malrotation occurs in both the talonavicular and ankle joints. This rotational deformity should be corrected at the time of reconstructive surgery, especially in cases of severe abduction deformity. In addition, medial ankle joint narrowing was observed in PCFD patients, with a higher prevalence of medial ankle joint narrowing in those with severe abduction. Level III, case-control study.

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

BackgroundThe aim of this study was to present and evaluate methods of measuring toe joint angels using joint-surface based and inertial axes approaches. MethodsNine 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. ResultsThe 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). ConclusionThe 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.

A Relationship between Anterior Talar Migration in the Sinus Tarsi on Weightbearing Computed Tomography and Failure of the Talocalcaneal Interosseous Ligament in Progressive Collapsing Foot Deformity

Category: Hindfoot; Midfoot/Forefoot Introduction/ Purpose: Progressive collapsing foot deformity (PCFD) is a complex condition thought to be incited by ligament failure. The spring ligament has been extensively studied, and its reconstruction as part of the PCFD correction is becoming more popular. Failure of the interosseous ligament may also be a key contributor, although its role is less described. Since the advent of weightbearing computed tomography (WBCT), the sinus tarsi talocalcaneal relationship has been shown to correlate with the foot deformity as well as the ligament status surrounding the talus. This study aimed to identify when the interosseous and spring ligaments begin to fail in PCFD. Both WBCT and high-quality magnetic resonance imaging (MRI) were used to identify sinus tarsi morphologies involved in failure of the interosseous and spring ligaments. Methods: This study included 82 PCFD patients (mean age: 51.8 years) who underwent preoperative WBCT and MRI. Sinus tarsi morphology on WBCT was categorized into two major categories based on the anterior migration of the talus over the calcaneus on sagittal images: No-migration (Type 1) and Migration (Type 2). Then, a subgroup was established based on the presence of bony impingement: a: no-impingement; b: impingement (Figure 1). Two radiologists evaluated the status of the ligaments around the talus, including the spring and interosseous ligaments, as normal, insufficiency, or tear. On WBCT images, axial plane talocalcaneal subluxation was determined by comparing the talar and calcaneal axes to the transmalleolar axis. The status of the ligaments, degree of talocalcaneal subluxation and calcaneofibular impingement on WBCT, and four plain radiographic parameters of each type were compared. A weighted kappa test was used to determine the interrater reliability of the classification system among six observers. Results: Major categorization revealed distinct differences between the two types, with the migration type (n=38) demonstrating a larger prevalence of torn spring (superomedial: 47.4% and inferomedial: 42.1%) and interosseous (47.4%) ligaments, a greater degree of internal rotation of the talus and talocalcaneal subluxation, and a greater deformity on plain radiographs than the no- migration type (n=44, Table 1). Out of 21 patients with torn interosseous ligament, only 6 (28.6%) exhibited bony calcaneofibular impingement, and these were all Type 2b patients. Except for differences in Meary's angle and Talonavicular coverage angle between Type1a and Type1b, subtypes based on impingement did not exhibit significant differences on MRI, WBCT, or plain radiographic findings. Interrater reliability testing showed substantial agreement between observers, with a kappa of 0.792 (95% confidence interval: 0.713-0.877). Conclusion: While failure of the interosseous ligament is known to occur at the latest stage of PCFD when there is bone on bone calcaneofibular impingement, our study reveals that failure commences during the transition from moderate to severe deformities. This correlates with the anterior migration of the talar process relative to the angle of Gissane in the sagittal plane as well as talar internal rotation in the axial plane. These findings imply that like spring ligament reconstruction, interosseous ligament reconstruction may serve a role in correcting PCFD in somewhat earlier as well as more advanced stages.

THE RELATIONSHIP BETWEEN KNEE JOINT ALIGNMENT, 3-D JOINT SPACE WIDTH AND SUBCHONDRAL BONE PARAMETERS IN INVIDUALS WITH RADIOGRAPHIC OSTEOARTHRITIS: A MOST INVESTIGATION

Joint alignment is an important factor in OA affecting how forces pass through the knee. The increasing use of weight bearing computed tomography (WBCT) in OA research has made the weight bearing stance an important consideration in 3-D imaging analysis, but its influence through biomechanics on the joint and subchondral bone is not fully understood. To investigate the relationship between knee joint alignment and 3-D joint parameters derived from joint space mapping of WBCT imaging in individuals with radiographic OA. WBCT of both knees was acquired at the 144-month visit of the Multicenter Osteoarthritis Study (MOST). Knees with a KLG ≥2 were included in the analysis, taking the side with higher KLG or averaging subsequent results from both sides if equal. Joint space mapping was performed to obtain the 3-D JSW distribution along with femoral (f) and tibial (t) subchondral bone thickness (ST) and trabecular attenuation (TA). Everyone's knee parameter maps were then transferred to a canonical joint surface. Alignment of the knee joint was measured as the angle between the central axis of the distal femur and proximal tibia in a coronal multiplanar reformat slab of the WBCT data: neutral alignment was set as zero with varus signed positive (figure part (a)). Statistical parametric mapping (SPM) was performed using a general linear model to test the dependence of each 3-D parameter distribution on alignment controlling for age, sex, mass, height, and joint space shape modes. SPM results were plotted on the canonical joint surface with unmasked regions representing a significance level of P<0.05. 136 knees were included in the analysis, 84 of which were females. Mean ± SD age was 66.4 ± 9.8 yrs; mass 85.3 ± 17.8 kg; height 1.69 ± 0.1 m. The distribution of radiographic grading was KL2 = 103; KL3 = 32; KL4 = 1. Mean alignment was 0.38 ± 3.80°. For each degree from valgus to varus, JSW was significantly narrower in the medial compartment and wider in the lateral compartment by up to 0.1 mm (figure part (d)). While TA was significantly greater by up to 10 AU in the medial femur (figure part (b)) and medial tibia (figure part (f)), there was up to 0.05 mm significantly thinner ST in the lateral femur (figure part (c)) and lateral tibia (figure part (e)). The opposite effects can be inferred for each degree towards valgus. The same analysis on KLG 0 and 1 knees in the same cohort (mean ± SD alignment 0.66 ± 2.94°) revealed no significant relationships. Subchondral bone plate and trabecular bone appear to behave differently in the medial and lateral compartments when considering knee joint alignment in individuals with OA. Greater subchondral trabecular bone attenuation was seen in the medial compartment with varus alignment, while greater subchondral bone plate thickness was seen in the lateral compartment with valgus alignment. Whether alignment is the cause or effect of OA and any altered biomechanics that may influence bone and joint space behaviour requires further investigation, but this study does establish that the forces associated with alignment appear to have different effects on subchondral bone in different compartments. National Institutes of Health, University of Kansas (R01AR071648), University of Iowa (U01AG18832) and University of California-San Francisco (U01AG19069). NS is a consultant for Integra BioLife, Trice Medical and Pacira Biosciences. TT has been a consultant for Curvebeam AI. The authors would like to thank participants and staff of the MOST study. CORRESPONDENCE ADDRESS: [email protected]

WEIGHT BEARING 3-D JOINT SPACE WIDTH DISTRIBUTION AT THE KNEE VARIES ACCORDING TO LOCATION AND EXTENT OF MENISCAL EXTRUSION: A MOST INVESTIGATION

Quantitative 3-D measurement of joint space width (JSW) from weight bearing computed tomography (WBCT) allows analysis of knee tibiofemoral compartments in a loaded stance without subregional constraints on analysis. The relationship between 3-D JSW distribution and meniscal extrusion is yet to be established. To demonstrate topographic variations in 3-D JSW distribution at the knee derived from WBCT imaging data according to meniscal extrusion location and extent. WBCT knee imaging was acquired at the 144-month visit of the Multicenter Osteoarthritis Study (MOST). A subset of individuals had medial and lateral meniscal extrusion grading according to the MRI Osteoarthritis Knee Score to identify medial extrusion of the medial meniscus (MMmed), anterior extrusion of the medial meniscus (MMant), anterior extrusion of the lateral meniscus (LMant), and lateral extrusion of the lateral meniscus (LMlat). The extent of extrusion was graded as 0: <2 mm; 1: 2 to 2.9 mm, 2: 3 to 4.9 mm; and 3: >5 mm. After semi-automatic segmentation of 663 baseline knees, joint space mapping was performed to create 3-D JSW maps for each knee registered to a template surface. Statistical parametric mapping (SPM) was performed using a general linear model to test the dependence of 3-D JSW distribution on each of meniscal extrusion type in turn. SPM results were plotted on the canonical joint surface, with unmasked regions demonstrating the topographic difference in JSW for each increment in extrusion score. 568 knees from 330 participants had meniscal extrusion grading available. Participants (178 female) had mean ± SD age 62.0 ± 9.3 years, body mass 82.2 ± 17.4 kg, height 170 ± 9.5 cm, and BMI 28.3 ± 4.8 kg/m2. Analysed knees were bilateral for 238 participants and unilateral for 92 participants. For MMmed (cohort score range 0-3), the central-to-posterior medial compartment had significantly lower JSW by up to 0.4 mm for each increment in meniscal extrusion grade. Both MMmed and MMant (score range 0-3) were associated with a small region of similarly significantly lower JSW along the medial margin of the lateral compartment, but also with significantly greater JSW at the anterior medial compartment of up to 0.6 mm per grade. The posterior medial joint space was significantly narrower (up to 3 mm) comparing knees with LMant scores of 0 vs 1. This same magnitude of narrowed JSW was detected along the periphery of the lateral joint space comparing grades in the lateral tibiofemoral compartment, but this was not statistically significant. LMlat (score range 0-2) was associated with a trend for greater reduction in JSW in the central lateral compartment of up to 0.5 mm per grade, but this was not statistically significant. Direction of meniscal extrusion is represented by the black arrowhead in the figure. Both medial and anterior extrusion of the medial meniscus are associated with significant reduction in JSW at the medial margin of the lateral joint space and widening of the anterior margin, likely from a posteromedial shift of the femoral condyles with respect to the tibia. Medial extrusion of the medial meniscus is also associated with narrowed JSW in the central to posterior medial joint space, likely as a direct effect of the loss of meniscal hoop tension. Anterior (but not lateral) extrusion of the lateral meniscus is associated with significantly lower JSW in the posterior medial joint space. These findings confirm that the extent and location of meniscal extrusion are key factors in weight bearing 3-D JSW distribution.

Axial Rotation of the Talus in Progressive Collapsing Foot Deformity: A Weightbearing Computed Tomography Analysis

Category: Hindfoot; Midfoot/Forefoot Introduction/ Purpose: Progressive collapsing foot deformity (PCFD) is recognized as a three-dimensional deformity centered around the talus. Although sagittal plane talar sagging or coronal plane valgus talar tilt have been well described, axial plane alignment referencing the talus, calcaneus and second metatarsal to the ankle has not been studied in PCFD patients. The purpose of this study was to examine the axial plane alignment of PCFD versus controls using weightbearing computed tomography (WBCT) and to determine if talar rotation in the axial plane is associated with increased abduction deformity. We hypothesized that the talus would exhibit greater internal rotation in PCFD patients than in control patients, and that this rotation would increase with worsening abduction deformity. Methods: Multiplanar reconstructed (MPR) WBCT scans of 79 patients with PCFD were analyzed. Patients were divided into two groups according to their preoperative talonavicular coverage angle (TNC): moderate abduction (TNC 20-40, n=57) and severe abduction (TNC &gt;40, n=22). 39 WBCT scans from healthy patients without PCFD or hindfoot deformity were included as controls. Using the MPR WBCT images, the axis of talus (TM [transmalleolar]-Tal), calcaneus (TM-Calc), and 2nd metatarsal (TM-2MT) were measured in reference to the transmalleolar axis (Figure 1). Smaller angles represented internal rotation relative to the TM axis. The difference between TM-Tal and TM-Calc was calculated to assess talocalcaneal subluxation. The prevalence of medial tibiotalar joint space narrowing, which was assessed with medial to dorsal tibiotalar joint space ratio (M/D ratio &lt; 0.5 was defined as ‘narrowing’), and medial ankle spurs were also evaluated. Results: TM-Tal was significantly smaller in PCFD patients compared to controls (Figure 2). This difference was accentuated in PCFD with severe abduction, who saw significantly smaller TM-Tal than the moderate abduction group. TM-Calc did not differ between groups, indicating similar axial calcaneal orientation. The TM-2MT revealed a significant difference between groups, reflecting foot abduction in PCFD. Diff Tal-Calc values were greater in PCFD patients, indicating that PCFD patients have more talocalcaneal subluxation in the axial plane. The severe abduction group had a higher Diff Tal-Calc value than the moderate abduction group. PCFD patients had a significantly higher prevalence of medial ankle joint space narrowing and medial spur formation than controls; however, there were no significant differences between the severe and moderate abduction groups. Conclusion: This study found that internal rotation of the talus is a key component of PCFD and is accentuated in more severe abduction deformities. These findings suggest that talar malrotation in the axial plane should be considered an underlying feature of abduction deformity and that this deformity should be corrected at the time of reconstructive surgery, especially in cases of severe abduction deformity. In addition, these findings support the observations of medial joint narrowing and medial spur formation in PCFD patients. Further research is warranted to identify optimal strategies for correction of talar rotation and how to reproducibly assess this intraoperatively.

Assessment of foot deformities in individuals with cerebral palsy using weight-bearing CT.

The aims of this study were to visualize and quantify relative bone positions in the feet of individuals with cerebral palsy (CP) with a foot deformity and compare bone positions with those of typically developed (TD) controls. Weight-bearing CT images of 14 individuals with CP scheduled for tendon transfer and/or bony surgery and of 20 TD controls were acquired on a Planmed Verity WBCT scanner. Centroids of the navicular and calcaneus with respect to the talus were used to quantify foot deformities. All taluses were aligned and the size and dimensions of the individuals' talus were scaled to correct for differences in bone sizes. In order to visualize and quantify variations in relative bone positions, 95% CI ellipsoids and standard deviations in its principle X-, Y-, and Z-directions were determined. In individuals with CP (age 11-17), a large variation in centroid positions was observed compared to data of TD controls. Radiuses of the ellipsoids, representing the standard deviations of the 95% CI in the principle X-, Y-, and Z-directions, were larger in individuals with CP compared to TD controls for both the calcaneus (3.16 vs 1.86mm, 4.26 vs 2.60mm, 9.19 vs 3.60mm) and navicular (4.63 vs 1.55mm, 5.18 vs 2.10mm, 16.07 vs 4.16mm). By determining centroids of the calcaneus and navicular with respect to the talus on WBCT images, normal and abnormal relative bone positions can be visualized and quantified in individuals with CP with various foot deformities.

Ankle syndesmotic instability assessment using a three-dimensional distance mapping algorithm: a cadaveric pilot WBCT study

Objective: This cadaveric pilot study was to develop a weight bearing computed tomography (WBCT) three-dimensional (3D) distance mapping algorithm that would allow for detection of syndesmotic instability. Methods: Pilot study, two cadaveric specimens. Syndesmotic instability was induced by release of all syndesmotic ligaments through a conventional lateral ankle approach. WBCT imaging under simulated weight bearing was acquired before and after syndesmotic destabilization. Syndesmotic incisura and ankle gutter distances were assessed using a 3D distance mapping WBCT algorithm. Results: We found increases in the overall mean syndesmotic distances in the injured syndesmosis when compared to pre-injury state, and color coded distance maps allowed easy interpretation of the syndesmotic widening following ligament sectioning and destabilization of the syndesmotic joint. Conclusion: The WBCT 3D distance mapping algorithm has the potential to allow detection of mild syndesmotic instability with a relatively ease of interpretation by using color-coded distance maps. Level of Evidence V; Cadaveric Study.

Three-dimensional assessment of hallux valgus correction using the Lapicotton technique

Objective: The objective of the study was to assess the efficacy of the LapiCotton procedure on patients with hallux valgus (HV) combined with medial longitudinal arch collapse. Methods: Preoperative and postoperative weight-bearing computed tomography (WBCT) scans were obtained from patients with HV submitted to the LapiCotton procedure. Semi-automatic measurements were applied to 22 WBCT images across 11 patients enrolled in the study using a software package (Bonelogic, Disior™, Helsinki, Finland). Significance level was set at 0.05. Results: The hallux valgus angle (HVA) was significantly larger (p=0.026) in the preoperative group (Mdn = 27.52) than in the postoperative group (Mdn = 20). In addition, the Meary sagittal measurement was found to be significantly increased (p=0.033) in the preoperative group (Mdn = -14.28) when compared to the postoperative group (Mdn = -11.15). It was also observed that the intermetatarsal angle was significantly larger (p=0.003) in the preoperative group (Mdn = 15.68) compared to the postoperative group (Mdn = 11.26). Conclusion: The LapiCotton procedure effectively corrected radiographic parameters in patients with HV combined with the medial longitudinal arch collapse. Level of Evidence III; Therapeutic Studies; Comparative Retrospective Study.

Improved responsiveness to change in joint space width over 24-month follow-up: comparison of 3D JSW on weight-bearing CT vs 2D JSW on radiographs in the MOST study

Radiographic joint space width (JSW) has been a standard for measuring knee osteoarthritis (OA) structural change. Limitations in the responsiveness of this approach might be overcome by instead measuring 3D JSW on weight-bearing CT (WBCT). This study compared the responsiveness of 3D JSW measurements using WBCT with the responsiveness of radiographic 2D JSW. Standing, fixed-flexion knee radiographs (XR) and WBCT were acquired ancillary to the 144- and 168-month Multicenter Osteoarthritis Study visits. Tibiofemoral JSW was measured on both XR and WBCT. Responsiveness to change was defined by the standardized response mean (SRM) for change in JSW (1) at predetermined mediolateral locations (JSWx) on both modalities and (2) in the following subregions measured on WBCT images: central medial and lateral femur (CMF/CLF) and tibia (CMT/CLT), and anterior and posterior tibia (AMT/ALT, PMT/MLT). Baseline and 24-month follow-up JSWx measurements were completed for 265 participants (58.1% women). Responsiveness of 3D JSWx for medial tibiofemoral compartment on coronal WBCT (SRM range:-0.18,-0.24) exceeded that for 2D JSWx (-0.10,-0.16). Responsiveness of 3D JSW subregional mean (-0.06,-0.36) and maximal (-1.14,-1.75) CMF and CMT and maximal CLF/CLT 3D JSW changes were statistically significantly greater in comparison with respective medial and lateral 2D JSWx (P≤0.002). Subregional 3D JSW on WBCT is substantially more responsive to 24-month changes in tibiofemoral joint structure compared to radiographic measurements. Use of subregional 3D JSW on WBCT could enable improved detection of OA structural progression over a 24-month duration in comparison with measurements made on XR.

Augmented stress weightbearing CT for evaluation of subtle tibiofibular syndesmotic injuries in the elite athlete.

We aim to present a novel imaging technique utilizing weight-bearing CT with syndesmotic stress to identify subtle, unstable syndesmotic injuries. We illustrate this with a case presentation of such an injury in an elite athlete that ultimately required operative fixation. In order to perform an augmented stress weightbearing CT, the patient is in the standing position, feet facing forward, and with weight distributed equally. The patient is then coached to internally rotate the shin and knee. This places an external rotational moment on the TFS due to the planted foot and ankle. The augmented stress images undergo 3D reconstruction and post-processing to render coronal and sagittal images. These are subsequently compared to standard, conventional weightbearing CT images performed without the external rotation stress. We illustrate this technique by presenting a case in which a 21-year-old collegiate athlete sustained a Grade II syndesmotic injury, diagnosed by MRI and clinical exam without evidence of instability by standard weightbearing CT or weightbearing radiographs. After undergoing the augmented stress weightbearing CT, the instability was noted. This prompted subsequent operative fixation and ultimately return to sport. We propose this technique for diagnosing unrecognized, subtle dynamically unstable syndesmosis injuries where clinical suspicion persists despite negative imaging, particularly in the elite athlete.

Sesamoid View X-ray vs Weightbearing Computed Tomography in the Measurement of Metatarsal Pronation Angle

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: First metatarsal (M1) axial rotation as measured by the metatarsal pronation angle (MPA) has increasingly become recognized as a clinically relevant component of hallux valgus deformity and methods to realign the M1 in 3 dimensions have been developed. Preoperative imaging with weightbearing computed tomography (WBCT) is considered the best way to image and measure the MPA, however WBCT is not available to many foot and ankle surgeons. The aim of this project is to investigate if the MPA measured on sesamoid view weight bearing radiographs is similar to that measured on WBCT. Methods: A retrospective analysis of patient imaging studies was performed. We identified 25 feet with both sesamoid WBR and WBCT images from a consecutive patient database. Included subjects had no trauma or foot and ankle operation between acquisition of the two scans. MPA of the WBCT for each patient was initially measured. After an appropriate washout period, the observer then measured MPA of the WBR for the cohort. Demographic statistics were calculated, a paired t-test was performed to evaluate for any significant difference in angular measurement between the two scans. Results: Patient characteristics: mean age 53 +- 16 years, mean BMI 32 +- 8 kg/m2, 13 right and 12 left feet, 19 females and 6 males. Average time between sesamoid view WBR and WBCT was 5.7 +- 9.5 months. Mean difference in MPA between WBR and WBCT = 0.6 +- 3.9 degrees (p= 0.444, t=0.777). Conclusion: Among the cohort assessed, we found no significant difference present in the measurement of the metatarsal pronation angle as evaluated on sesamoid view weightbearing radiography compared with weightbearing computed tomography (Figure 1). Routine acquisition of a sesamoid view weightbearing radiograph may be considered as an appropriate substitute for weightbearing computed tomography in the preoperative evaluation of M1 rotation in the coronal plane. These findings may benefit physicians who do not have access to weightbearing computed tomography in their clinics.

Radiographic Cut-Off Values for Predicting Lateral Bony Impingement in Progressive Collapsing Foot Deformity: A Correlation Analysis with Weightbearing Computed Tomography

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: Lateral bony impingement, one of the main causes of lateral foot pain in progressive collapsing foot deformity (PCFD), reflects disease severity and may affect surgical planning. Weightbearing computed tomography (WBCT) is known to provide better sensitivity in detecting impingement over simple radiographs, however, many Orthopaedic centers have not yet acquired WBCT imaging. This study aimed to (1) investigate the correlation of common radiographic parameters measured on standard weightbearing radiographs with talocalcaneal and calcaneofibular distance assessed with WBCT and (2) establish cut-off values for radiographic measurements on standard radiographs to detect lateral bony impingement as identified on WBCT. Methods: Ninety-one adult patients (mean age and standard deviation, 54.1 +- 17.2 years) treated for PCFD with standard preoperative radiographs and WBCT within 6 months of each other were retrospectively identified. Patients with previous ipsilateral foot and ankle surgery or asymmetric ankle arthritis (talar tilt &gt; 2 degrees) were excluded. The talocalcaneal distance at the sinus tarsi and subfibular calcaneofibular distance were measured in multiplanar reconstructed WBCT images. Bony impingement was defined as direct contact between the structures. The relationships between WBCT measurements and four common parameters (Talonavicular coverage angle [TNC], Talo-1st metatarsal angle, Calcaneal pitch, and hindfoot moment arm [HMA]) in standard radiographs were assessed with Pearson correlations. Receiver operating characteristic (ROC) curve analysis was performed to determine the ability of radiographic parameter thresholds to predict sinus tarsi or calcaneofibular bony impingement, and the area under curve (AUC), sensitivity, specificity, negative and positive predictive value were calculated. Results: Talocalcaneal distance narrowing at the sinus tarsi on WBCT was strongly correlated with TNC (r = 0.64, p &lt; 0.001), and the calcaneofibular distance narrowing on WBCT correlated with the HMA moderately yet best among the parameters (r=0.55, p&lt;0.001). Interrater and intrarater reliability of WBCT measurements was excellent. TNC (AUC=0.837, 95% confidence interval [CI], 0.745-0.906) and HMA (AUC=0.959, 95%CI, 0.895-0.989) provided the best predictive ability for sinus tarsi and calcaneofibular bony impingement, respectively (Figure 1). The cut-off value for TNC for predicting sinus tarsi bony impingement was 25.4 degrees, with a sensitivity of 80.4% and a specificity of 72.5%. The cut-off value for HMA for predicting calcaneofibular bony impingement was 25.4mm, with a sensitivity of 100% and a specificity of 81.2% (Table 1). Conclusion: This study provides evidence that common radiographic parameters in standard radiographs can be potentially used to detect lateral bony impingement in PCFD. Narrowing of talocalcaneal distance at the sinus tarsi was best correlated with abduction deformity of the foot, and the narrowing of calcaneofibular distance was best correlated with valgus hindfoot deformity. TNC and HMA on standard radiographs may be used for detecting sinus tarsi and calcaneofibular bony impingement, respectively.

Developing Objective Computational Methods for Quantifying Ankle Osteoarthritis using Low-Dose Weight Bearing CT

Category: Ankle Arthritis; Ankle; Other Introduction/Purpose: Decision regarding ankle osteoarthritis (OA) management varies depending on the severity and distribution of the associated joint degeneration. Disease staging is typically based on subjective grading of appearance on conventional plain radiographs, with reported sub-par reproducibility and reliability. Weight-bearing computed tomography (WBCT) offers clinical advantages in the setting of OA, where thinning of the ankle cartilage, softening of the cartilage, and other deformities become more apparent under load. WBCT also provides a better geometric representation of the ankle and allows for more accurate measurements when compared to a conventional radiograph. The purpose of this study was to develop and describe computational methods to objectively quantify radiographic changes associated with ankle OA apparent on low-dose WBCT images. Methods: We analyzed two patients with ankle OA and one healthy control that had all undergone WBCT of the foot and ankle. The severity of OA in the ankle of each patient was scored using the Kellgren-Lawrence (KL) classification by plain weight-bearing radiographs. For each ankle, the subsequent analysis focused on a volume of interest (VOI) centered on the tibiotalar joint. Within the VOI, the initial computational analysis focused on measuring the 3D joint space width (JSW). Subsequent analyses utilized WBCT image intensity (Hounsfield Unit, or HU) profiles along lines perpendicular to the subchondral bone/cartilage interface of the distal tibia extending across the entire VOI. The HU intensity profiles were recorded, and graphical plots of the HU distributions were generated for each line. These plots were then used to calculate the HU contrast, a novel measure of the regional variation in bone density. Results: The average JSW was 3.89 mm for the healthy control ankle, 2.69 mm for the mildly arthritic ankle (KL 2), and 1.57 mm for the severely arthritic ankle (KL 4). The average HU contrast was 72.31 for the healthy control ankle, 62.69 for the mildly arthritic ankle, and 33.98 for the severely arthritic ankle. The use of four projections at different locations throughout the joint allowed us to visualize specifically which quadrants have reduced joint space width and contrast. One projection in the severely arthritic ankle had JSW and contrast values of 0 due to complete joint space loss along with projection 4, which corresponds in this case to the posterolateral part of the joint (Figure). Conclusion: We presented a novel computational assessment of ankle osteoarthritis using low-dose WBCT imaging. We were able to demonstrate differences between normal ankles and ankles with mild and severe OA using JSW and HU contrast measurements. This methodology represents an important step towards a more reliable OA assessment when compared to the current standard qualitative evaluations, potentially serving as a starting point for the development of a more robust osteoarthritis staging system. Additional studies are needed to assess the algorithm more rigorously over a variety of radiographic presentations.

Coronal Plane Rotation of the Medial Column in Hallux Valgus (HV), Progressive Collapsing Foot Deformity (PCFD), and Combined PCFD HV: A Retrospective Case Control Study

Category: Bunion; Hindfoot; Midfoot/Forefoot Introduction/Purpose: The presence of hyperpronation of the first metatarsal (M1) seems to have a clinically significant role in Hallux Valgus (HV). Some authors reported a decrease in recurrence rates after M1 hyperpronation correction in HV. However, when measuring the M1 head pronation relative to the ground, we are assessing and quantifying the aggregate coronal rotational profile of each bone and joint throughout the medial column. Therefore, we do not know the location of this hyperpronation. Moreover, studies showed a strong influence of the hindfoot alignment on coronal rotational measurements and Progressive Collapsing Foot Deformity (PCFD) is a condition frequently associated with HV. Our study aimed to assess and compare coronal plane alignment of medial column bones in HV, PCFD, PCFD HV and controls. Methods: We performed a retrospective IRB approved study. We collected 33 feet who consulted our center with combinations of symptomatic PCFD and HV. We then matched 33 HV, 33 PCFD, and 33 controls for BMI, Gender, and Age to this group. We assessed the coronal plane rotation of the navicular, medial cuneiform, M1 at its base and head, the Sesamoid Rotation Angle (SRA) with respect to the ground, and the hallux valgus angle (HVA) using Weight-Bearing CT images (Figure).The positions of the different joints (first naviculocuneiform (NC1), first tarsometatarsal (TMT1) and metatarsosesamoid rotation angle (MSRA)) were found by subtracting the adjacent angles. Intrinsic torsion of M1 was calculated by subtracting the M1 base angle from the M1 head angle.Normality of different variables was assessed using the Shapiro-Wilk test. Groups were compared using t test or ANOVA for normal and Mann Whitney or Kruskal Wallis for nonnormal variables. Results: HV, PCFD and PCFD HV presented higher M1 intrinsic torsion when compared to controls (respectively 7.3°[CI95%:2.9-11.7], p&lt;0.001; 7.5°[CI95%:2.5-12.6], p&lt;0.001; 7.5°[CI95%: 2.9-12],p&lt;0.001).The navicular was more pronated in PCFD HV compared to controls (respectively 20+/-5.2° vs 12.5+/-3.9°,p&lt;0.001) whereas it was not for PCFD and HV.NC1 was 6.8° significantly more supinated in HV (p&lt;0.001) and 5.7° in PCFD HV (p&lt;0.001) compared to controls whereas there was no significant difference between PCFD HV and Controls.TMT1 was 7.3° significantly more pronated in HV (p&lt;0.001) and 4.9° in PCFD HV (p&lt;0.001) compared to controls whereas there was no significant difference between PCFD HV and Controls. MSRA was significantly higher in HV (p&lt;0.001) and PCFD HV (p&lt;0.001) compared to controls whereas there was no significant difference between PCFD and Controls. In multivariate analysis, MSRA (β=0.95,[0.83;1.07], p &lt;0.0001) were associated with higher values of HVA whereas NC1 (β=-0.24,[-0.42;-0.06], p= 0.0076) were associated with lower values of HVA. Conclusion: The intrinsic increase in M1 pronation appears to be a shared developmental abnormality in PCFD and HV. Combination of PCFD and HV seems to originate from the presence of a paradoxical supinatory malposition of the NC1 which was not present in PCFD without HV in our study. The presence of this compensatory supination malposition might explain the presence of HV by causing a metatarsosesamoid dislocation in HV and PCFD HV. In contrast, hyperpronation compensation in PCFD without HV might be proximal to the navicular because there was no difference between PCFD and control regarding the navicular position in our study.

The Longitudinal Axis of the Inter-Sesamoid Crista in Hallux Valgus and Its Relationship with the Distal Metatarsal Articular Angle. A Case Control Study

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Little is known about the intersesamoid crista in Hallux Valgus (HV). However, this structure directly interfaces with the sesamoids and surrounding soft tissues and might play an important role in HV deformity. Our primary objective was to compare the angulation between the crista and first metatarsal (M1) longitudinal axis in HV and controls. Our secondary objective was to assess its correlation with the Distal Metatarsal Articular Angle (DMAA). We hypothesized that the longitudinal axis of the crista will be deviated in valgus in HV and that its position will be correlated with the DMAA. Methods: This IRB approved retrospective case control study evaluated 9 HV and 8 controls matched on age, BMI, and gender. The DMAA was measured as initially described on X-Rays, and then on weight-bearing CT images using a previously validated technique including pronation correction of the M1 called 3d-DMAA. To identify the angle of the inter-sesamoid crista relative to the shaft of the 1st metatarsal, CT scans were semi-automatically segmented to create 3D models of the forefoot. The crista was selected in Geomagic Design X and the resulting STL models were imported into MATLAB for analysis. Principal component analysis was used to identify the direction of both the crista and the 1st metatarsal shaft. The crista-shaft angle is the angle between the directions of greatest variation. Normality was assessed using Shapiro-Wilk tests. Comparisons were made using Student T-tests for normal variables and Mann-Whitney for non-normals. Correlations were assessed using Pearson's coefficients. Results: The crista deviated from the 1st metatarsal shaft in valgus in all the cases (HV and controls). There was a significant increase in valgus deviation of the crista in HV compared to controls (respectively 14.4+/-8.7 degrees and 5.5+/-3.2 degrees; p=0.017). Mean DMAA were respectively 25.1+/-7.9 degrees in HV and 7.4+/-2.9 in controls (p&lt;0.001). Mean 3d-DMAA were respectively 12.5+/-5.6 degrees in HV and 3.1+/-2.4 in controls (p&lt;0.001). There was a low positive non-significant correlation between the crista deviation and the DMAA (ρ=0.44; r2=0.193; p=0.078). There was a moderate positive significant correlation between Crista M1 Angle and 3D-DMAA (ρ=0.57; r2=0.326; p=0.017). Conclusion: The longitudinal axis of the inter-sesamoid crista deviates from the 1st metatarsal shaft in valgus in HV compared to controls. This follows the pattern of the 3d-DMAA which reflect the valgus deviation of the articular surface after exclusion of the pronation which is an important confounding factor of the original DMAA. The inter-sesamoid crista may play a role in HV pathophysiology as a possible lateral destabilizer of the surrounding soft tissues in HV. Surgically correcting the DMAA with a distal osteotomy might also correct the crista position in HV.