Objective: To develop distance-mapping and coverage-mapping algorithms to assess metatarsophalangeal and metatarsal-sesamoid joint interaction in hallux valgus patients, comparing them to a control group. Methods: A total of 9 hallux valgus patients (mean age 37.1 y; 6 F/3 M) and 5 controls (mean age 39 y; 4 F/1 M) underwent weight-bearing computed tomography. Specific software was used to obtain bone segmentation images of the first and second metatarsals, the first and second proximal phalanxes, and the tibial and fibular sesamoids. Joint interaction based on distance mapping and coverage mapping of the first and second metatarsophalangeal joints and the metatarsal-sesamoid joints were calculated. The surfaces of the metatarsophalangeal joints were divided in a 2-by-2 grid using the principal axes to provide a more detailed analysis. P-values <0.05 were considered significant. Results: Coverage maps of hallux valgus and control patients revealed marked lateral and dorsal displacement in joint interaction of the first metatarsophalangeal joint, including decreased joint coverage of the medial facet of the joint. When comparing first metatarsophalangeal joint coverage, hallux valgus patients had significantly lower coverage of the dorsomedial quadrant (77%, p=0.0002) than controls, as well as significantly higher coverage of the plantarlateral (182%, p=0.005) and dorsolateral quadrants (44.9%, p=0.035). Conclusions: In this case-control study, we developed a distance and coverage map weight-bearing computed tomography algorithm to objectively assess 3D joint interaction, joint coverage, and subluxation in hallux valgus deformity. We observed significantly greater first and second metatarsophalangeal joint subluxation in hallux valgus patients than controls. Level of Evidence III; Case Control 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.

Category: Hindfoot; Midfoot/Forefoot Introduction/ Purpose: Peritalar subluxation (PTS) is a crucial feature of Progressive Collapsing Foot Deformity (PCFD). Surrounding structures assume distinct behaviors, contributing to different disease deformities (classes). One of its most traditional aspects is the midfoot abduction (class B), usually noted by a lateral deviation of distal structures at the talonavicular joint. This finding commonly leads surgeons to perform a lateral column lengthening osteotomy for abduction correction, a complex surgery with potential complications. The first ray's ability to reestablish the tripod and restore the hindfoot by derotating structures under the talus was previously theorized. This study aimed to test the capability of the Lapidus and the Cotton procedures in conjunction with a calcaneus displacement osteotomy (MDCO) to improve midfoot abduction in the setting of a collapsed foot. Methods: In this IRB-approved, prospective cohort study, we analyzed patients undergoing medial column instability surgery and evaluated preoperatively with a weight-bearing CT (WBCT). We included individuals receiving a Lapidus bone block procedure or a Cotton for PCFD or Hallux Valgus (HV). Patients having a lateral column lengthening procedure of any type were excluded. Talonavicular coverage angle (TNCA) was measured as a marker of midfoot abduction. Medial arch collapse and forefoot varus were evaluated by the sagittal talus-first metatarsal angle (TFMA), and the forefoot arch angle (FFA) was measured. Associated procedures and the correction amount (displacement or wedge size) were recorded. Normality was estimated by the Shapiro- Wilk test and comparison among timelines by the one-way ANOVA. A multivariate regression analysis was executed to evaluate which of the measurements influenced abduction improvement. Statistical significance was considered for p-values of less than 0.05. Results: A total of 20 patients (age: 43.85 [19-72], BMI 30.98 [SD: 5.95]) were included, 11 PCFD (55%) and 9 HV (45%) with a mean follow-up of 7.5 months (3-12). Bone block Lapidus was performed in most subjects (90%), and the median wedge used was 9mm (5-12mm). MDCO occurred in 55% of patients. All measured variables had improvement with surgery (TNCA: 23.74 to 10.66, p< 0.0001; FFA: 6.27 to 12.67, p< 0.0001; TFMA: 11.73 to 4.22, p=0.0003). A correlation was found between TNCA improvement and FFA improvement (rs=0.46, p=0.0407), but not among TNCA improvement and TFMA improvement (rs=0.43, p=0.06). The size of the wedge did not strongly influence the TNCA correction (R2=0.016, p=0.0036), an improvement moderately explained by the MDCO amount (R2=0.186, p< 0.0001). Conclusion: This study demonstrated correction of midfoot abduction, translated by the TNCA, in the absence of lateral column lengthening procedures. When evaluating patients submitted to first ray procedures (bone block Lapidus and Cotton) in conjunction with MDCO, an enhancement on the talar head coverage was noted. Variables associated with arch height and forefoot varus (FFA and TFMA) were correlated with the TNCA improvement. Nevertheless, only the MDCO displacement amount and not the size of the used allograft wedge could explain changes in TNCA. The provided data might support surgeons when planning treatment in the PCFD scenario.

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.

Category: Midfoot/Forefoot Introduction/Purpose: Weight-Bearing Computed Tomography (WBCT) measurements represent a reliable tool for radiographic analysis of the first ray, including multiplanar assessment in the axial, sagittal, and coronal planes. WBCT can allow for more reliable studies of pathologies, such as Hallux Rigidus (HR), which permits several anatomical points to be evaluated for a correct clinical-radiographic diagnosis. In addition, new software with an advanced semi-automated segmentation system obtains semi-automatic 3D measurements of WBCT scan data sets, minimizing the errors in reading angular measurements. The study`s objective was (1) to assess the reliability of WBCT computer-assisted semi-automatic imaging measurements in HR, (2) to compare semi-automatic to manual measurements in the setting of HR, and (3) to compare semi-automatic measurements between a pathologic (HR) group and a control standard group. Methods: This was a retrospective, IRB approved study of patients with Hallux Rigidus deformity. The sample size calculation was based on the Metatarsus Primus Elevatus (MPE). A control group consisting of 20 feet without HR and a pathologic group consisting of 20 feet with HR was necessary for this study. All WBCT manual and semiautomatic 3D measurements were performed using the following parameters: (1) first Metatarsal-Proximal Phalanx Angle (1stMPP) (sagittal plane), (2) Hallux Valgus Angle (HVA), (3) first to second Intermetatarsal Angle (IMA), (4) Hallux Interphalangeal Angle (IPA), (5) first Metatarsal Lengths (1stML), (6) second Metatarsal Length (2ndML), (7) first Metatarsal Declination Angle (1stMD), (8) second Metatarsal Declination Angles (2ndMD), and (9) MPE. The semiautomatic 3D measurements were performed using the Bonelogic Software. The differences between pathologic and control cases were assessed with a Wilcoxon test and P<= 0.05 was considered significant. Results: Interobserver and intraobserver agreement and consistency for manual versus semi-automatic WBCT measurements assessed by ICC demonstrated excellent reliability. Manual and semi-automatic measurements were performed in individuals with HR. According to the Pearson's coefficient, there was a strong positive linear correlation between both methods for the following parameters evaluated: HVA, (ρ = 0.96); IMA, (ρ = 0.86); IPA, (ρ = 0.89); 1stML, (ρ = 0.96); 2ndML, (ρ = 0.91); 1stMD, (ρ = 0.86); 2ndMD, (ρ = 0.95) and, MPE, (ρ = 0.87). Agreement between the manual and semi-automatic methods was tested using a Bland- Altman plot and expressed excellent agreement between the methods. Comparison between the pathological group with HR and the control (standard) group allowed for the differentiating of the pathological (HR) from the non-pathological conditions for MPE (p < 0.05). Conclusion: Semiautomatic measurements are reproducible and comparable to measurements performed manually, showing excellent interobserver and intraobserver agreement and consistency. The software used differentiated pathological from non- pathological conditions only when submitted to semi-automatic MPE measurements. The development of advanced semi-automatic segmentation software with minimal user intervention is an essential step toward the establishment of big data and can be integrated into clinical practice, facilitating decision making.

Objective: The goal of this paper was to evaluate the validity of foot and ankle offset (FAO) measurements in the setting of severe foot and ankle deformities. Methods: This study included 57 feet (36 patients) that had a history of severe cavovarus deformity. Each participant received a weight-bearing computed tomography (WBCT) scan that was then used to measure FAO. This measurement was performed once using the traditional measurement technique and two additional times using a modified technique that allows for rotational correction of the images to align the talus. Results: Traditional FAO (TFAO) and modified FAO (MFAO) were found to have a significant correlation with one another (r (54)=0.92, p<0.001). There was a high positive correlation between the variables of the two techniques (r=0.92) with the intraobserver reliabilities (ICC=0.95) for FAO measurements. The agreement between TFAO and Modified foot and ankle offset (MFAO) measurements was also considered excellent (ICC=0.99). Conclusion: The MFAO method provides statistically similar FAO measurements compared to the TFAO method in this population. Thus, the TFAO method could potentially expand its patient population to provide surgeons with a reliable tool for assessing more severe deformities. Level of Evidence IV; Retrospective Study.

Objective: To assess the agreement between semiautomatic 3D measurements and manual measurements derived from WBCT images in patients with end-stage ankle osteoarthritis (AO) who underwent total ankle replacement (TAR). Methods: In this retrospective, IRB-approved study (ID #201904825), we evaluated patients who underwent TAR via the lateral trans-fibular approach for end-stage ankle OA. The study included 14 ankles from 14 patients. Raw multiplanar data were analyzed using CubeVue® software. Lateral talar station (LTS) was obtained in the sagittal plane, while hindfoot moment arm (HMA) and talar tilt angle (TTA) were calculated in the coronal view. Semiautomatic 3D measurements were performed using Disior® software. Intra-rater reliabilities were analyzed using the intraclass correlation coefficient (ICC). Agreement between methods was tested with Bland-Altman plots. Each measurement was assessed using the Wilcoxon signed-rank test. Alpha risk was set to 5% (α=0.05). P-values of ≤0.05 were considered significant. Results: ICC-measured reliabilities ranged from moderate to almost perfect for manual and semiautomatic WBCT measurements in the preoperative and postoperative groups for HMA and LTS. There was high correlation between parameters calculated from manual and semiautomatic measurements, and strong agreement between the readers and software in both groups. Conclusions: Manual (M) and semiautomatic (SA) 3D measurements expressed excellent agreement for pre- and postoperative groups, indicating a high correlation between the parameters calculated and strong agreement between the readers and the software in both groups. Level of Evidence III; Therapeutic Studies; Comparative Retrospective Study.

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