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Background: Altered stress distribution in the lower limb may impact bone mineral density (BMD) in the ankle bones. The purpose of the present study was to evaluate the spatial distribution of BMD with use of weight-bearing cone-beam computed tomography (WBCT). Our hypothesis was that BMD distribution would be even in normal hindfeet, increased medially in varus hindfeet, and increased laterally in valgus hindfeet., Methods: In this study, 27 normally aligned hindfeet were retrospectively compared with 27 valgus and 27 varus-aligned hindfeet. Age (p = 0.967), body mass index (p = 0.669), sex (p = 0.820), and side (p = 0.708) were similar in the 3 groups. Hindfoot alignment was quantified on the basis of WBCT data sets with use of multiple measurements. BMD was calculated with use of the mean Hounsfield unit (HU) value as a surrogate. The HU medial-to-lateral ratio (HUR), calculated from tibial and talar medial and lateral half-volumes, was the primary outcome of the study., Results: The 3 groups significantly differed (p < 0.001) in terms of tibial HUR (median, 0.91 [interquartile range (IQR), 0.75 to 0.98] in valgus hindfeet, 1 [IQR, 0.94 to 1.05] in normal hindfeet, and 1.04 [IQR, 0.99 to 1.1] in varus hindfeet) and talar HUR (0.74 [IQR, 0.50 to 0.80] in valgus hindfeet, 0.82 [IQR, 0.76 to 0.87] in normal hindfeet, and 0.92 [IQR, 0.86 to 1.05] in varus hindfeet). Linear regression showed that all hindfoot measurements significantly correlated with tibial and talar HUR (p < 0.001 for all). The mean HU values for normally-aligned hindfeet were 495.2 ± 110 (medial tibia), 495.6 ± 108.1 (lateral tibia), 368.9 ± 80.3 (medial talus), 448.2 ± 90.6 (lateral talus), and 686.7 ± 120.4 (fibula). The mean HU value for each compartment was not significantly different across groups., Conclusions: Hindfoot alignment and medial-to-lateral BMD distribution were correlated. In varus hindfeet, an increased HU medial-to-lateral ratio was consistent with a greater medial bone density in the tibia and talus as compared with the lateral parts of these bones. In valgus hindfeet, a decreased ratio suggested greater bone density in the lateral as compared with the medial parts of both the tibia and the talus., Level of Evidence: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/H656 )., (Copyright © 2023 by The Journal of Bone and Joint Surgery, Incorporated.)

Ankle arthrodesis is commonly performed to treat end-stage ankle osteoarthritis. The aim of this study was to determine whether the use of fibular autograft might increase the fusion rate and decrease the complication rate in ankle arthrodesis (AA) fixed using cannulated screws. To perform this PRISMA-compliant proportional meta-analysis, multiple databases were searched for studies in which patients undergone AA (using exclusively cannulated screws and augmented with fibular bone graft) were followed. The characteristics of the cohort, the study design, surgical details, the nonunion and complication rate at the longest follow-up were extracted and recorded. The modified Coleman Methodology Score (mCMS) was applied to appraise the quality of studies. Two groups were built: arthrodeses fixed with screws combined with cancellous autograft (G1) and arthrodeses fixed with screws combined with cancellous autograft and augmented with a lateral fibular onlay (G2). A third group (arthrodeses fixed with screws and no graft, G3) was extracted from previous literature for a further comparison. Overall, we included 306 ankles (296 patients) from ten series (ten studies). In G1 and G2 there were 118 ankles (111 patients) and 188 ankles (185 patients), respectively. In patients where cancellous autograft was used, a further augmentation with a fibular lateral strut autograft did not change significantly the nonunion (4% [95% CI 1-9] in G1 vs. 2% [95% CI 0-5) in G2, p = 0.99) nor the complication rate (18% [95% CI 0-36] in G1 vs. 13% [95% CI 6-21) in G2, p = 0.71). Upon comparison with 667 ankles (659 patients, G3) in which arthrodeses had been performed without grafting, the nonunion and complication rates did not differ significantly either (pooled estimates: 3% [95% CI 1-3) in G1 + G2 vs. 3% [95% CI 2-4] in G3, p = 0.73 for nonunion; 15% [8-23] in G1 + G2 vs. 13% [95% CI 9-17] in G3, p = 0.93 for complications). In ankle arthrodesis fixed with cannulated screws combined with cancellous autograft at the fusion site, a construct augmentation with a distal fibular onlay strut graft positioned laterally at the ankle joint does not reduce the risk of nonunion or complication. In general, the use of bone graft does not influence significantly the nonunion nor the complication rate as compared to non-grafted screw-fixed ankle arthrodeses.Kindly check and confirm the corresponding author mail id is correctly identified.It's all correct., (© 2023. The Author(s).)

Objective: Ankle arthrodesis (AA) is often fixed using cannulated screws. The irritation from metalwork is a relatively common complication, but there is no consensus regarding the need to remove the screws on a systematic basis. The aim of this study was to determine (1) the proportion of screws removed after AA and (2) whether predictors of screw removal could be identified., Methods: This PRISMA-compliant systematic review was part of a larger previous protocol registered on the PROSPERO platform. Multiple databases were searched including studies in which patients undergone AA using screws as exclusive fixation method were followed. Data were harvested regarding the cohort, the study design, the surgical technique, the nonunion and complication rate at the longest follow-up. Risk of bias was assessed using the modified Coleman Methodology Score (mCMS)., Results: Forty-four series of patients from thirty-eight studies (1990 ankles, 1934 patients) were selected. The average follow-up was 40.8 months (range 12-110). In all studies, hardware was removed due to symptoms reported by patients and related to the screws. The pooled proportion of removal of metalwork was 3% (95% CI 2-4). The pooled proportion of fusion was 96% (95%CI 95-98), while the pooled proportion of complications and reoperations (excluding the removal of metalwork) stood at 15% (95% CI 11-18) and 3% (95% CI 2-4), respectively. The mean mCMS (50.8 ± 8.1, range 35-66) revealed only an overall fair quality of studies. The univariate analysis and the multivariate model showed that the year of publication (R = - 0.004; p = 0.01) and the number of screws (R = 0.08; p = 0.01) were associated with the screw removal rate. Specifically, we found that over time the removal rate decreased by 0.4% per year and that the use of three screws instead of two reduced the risk of removal of metalwork by 8%., Conclusions: In this review, removal of metalwork after ankle arthrodesis using cannulated screws was needed in 3% of cases at an average follow-up of 40.8 months. It was indicated only in case of symptoms related to soft tissue irritation from screws. The use of three screws was paradoxically related to a reduced risk of removal of screws as compared to two-screw constructs., Level of Evidence: Level IV, systematic review of Level IV., (© 2023. The Author(s).)

Introduction: The goal of this study was to describe the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints in patients presenting with Pes Planovalgus (PPV) using three-dimensional (3D) distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of PPVs to a series of normally-aligned feet. We hypothesized that in PPVs joint interactions would reveal significantly increased spaces in the medial side of the ankle, hindfoot and midfoot joints., Methods: In this case-control study, ten feet (10 patients) with asymptomatic PPV were compared to 10 matched-paired (by age, gender and body mass index) normally-aligned feet (10 patients). Three-dimensional models were produced from the images and distance maps representing joint surface configuration were generated for the ankle, hindfoot and midfoot joints. The distance maps for each joint were then compared between the two groups and between regions in the same group., Results: In PPV patients there was a significantly increased surface-to-surface distance anteromedially at the ankle joint (+46.3%, p < 0.001) along with an increased distance on the anterior halves of both the medial (+21.3%, p = 0.098) and lateral malleoli (+22.7%, p = 0.038). At the posterolateral corner of the posterior facet of the subtalar joint we found an increased surface-to-surface distance (by 57.1%, p < 0.001), while at the talonavicular joint there was a reduction of the distance at the superomedial corner (-20%, p = 0.097) along with a significant increase in the upper central (+20%, p = 0.039) and lateral (+30.7%, p = 0.015) zones. A reduction of the surface-to-surface distance was also observed in three of the four zones of the calcaneocuboid joint. Finally, a statistically significant increase in the mean distance was observed at the naviculocuneiform and tarsometatarsal joints in a range between 38% and 93.4% (p < 0.001 in all cases)., Conclusion: We found significant differences in surface-to-surface interaction at the foot and ankle joints between Pes Planovalgus and normally-aligned controls. Distance mapping on WBCT images could be used in clinical practice as a diagnostic support to gauge the morphological changes of articular spaces occurring in Pes Planovalgus., Level of Evidence: Level III, case-control study., (Copyright © 2021 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.)

Purpose: Multiple Level I meta-analyses were conducted comparing traditional static vs. more recently introduced dynamic strategies of fixation for injuries of the distal tibiofibular syndesmosis (TFS). The aim of this review was to assess their robustness and methodological quality, providing support in the choice of a treatment strategy in case of TFS injury using the highest level of evidence., Methods: In this systematic review, conducted in accordance with the PRISMA guidelines, meta-analyses/systematic reviews comparing static and dynamic fixation methods after acute TFS injury were identified. The robustness of studies was evaluated using the fragility index (FI) for meta-analysis and the fragility quotient (FQ). The risk of bias was evaluated using the Assessment of Multiple Systematic Reviews (AMSTAR) instrument. Finally, the Jadad was applied to select the study which provided the highest quality of evidence to develop recommendations for the fixation strategy of these lesions., Results: Out of 1.302 records, four Level I meta-analyses were included in this study. Analyzing the statistically significant dichotomous outcomes, the median FI was 3.5 (IQR, 2 to 5.5; range, 1 to 9), while the median FQ was 1.9% (IQR, 1 to 3.5; range 0.35 to 4.4). In total, 37% had an FI of 2 or less and 75% of outcomes had a FI of 4 or less. According to the AMSTAR score and Jadad algorithm, the largest meta-analysis was selected as the highest evidence provided so far., Conclusion: The meta-analyses with statistically significant dichotomous outcomes comparing dynamic and static fixation for treating injuries of the distal tibiofibular syndesmosis are fragile, with a change in less than four patients or less than 2% of the study population sufficient to reverse a significant outcome to nonsignificant., Level of Evidence: Level I., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Introduction: The goal of this study was to characterize the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints of the cavovarus foot using distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of cavovarus feet to a series of normally-aligned feet., Methods: In this case-control study, ten feet (10 patients) with asymptomatic cavovarus shape (cases; N = 10) were compared to 10 matched-paired (by age, gender and body mass index) normally-aligned feet (10 patients) (controls; N = 10). Three-dimensional models were produced from the images and distance maps representing joint surface configuration were generated for the ankle, hindfoot and midfoot joints. The distance maps for each joint were then compared between the two groups and between regions in the same group., Results: In the cavovarus group there was a significant increase in surface-to-surface distance at the posterior tibiotalar joint and a reduced distance at the anterior part, together with a greater distance at the posterior half of the medial gutter. Also, a decrease in surface-to-surface distance on the anterior half of the anterior facet and an increased distance on the posterior quadrants of the posterior facet of the subtalar joint were found. At the sinus tarsi, the lateral aspect of the talonavicular joint, the naviculocuneiform and the tarsometatarsal joints there was a statistically significant increase in surface-to-surface distance in cavovarus patients as compared to controls., Conclusion: Distance mapping analysis on WBCT images identified significant differences in surface-to-surface interaction at the foot and ankle joints between cavovarus and normally-aligned feet., Level of Evidence: Level III, case-control study., (Copyright © 2020 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.)

Background: Previous studies focusing on the effects of knee surgery on hindfoot alignment have suggested some degree of compensation between the knee and the hindfoot. However, these studies did not investigate a preoperative relationship in patients without end-stage knee osteoarthritis using 3-dimensional (3D) biometrics. The purpose of this study was to investigate the relationship between knee and hindfoot alignment using 3D weightbearing imaging., Methods: This retrospective comparative study included 95 lower limbs with weightbearing computed tomography and low-dose biplanar radiograph investigations. Cases with a history that may have caused a change in lower limb alignment were excluded. Hindfoot and knee alignments were measured using foot ankle offset (FAO) and hip-knee-ankle (HKA) angle, respectively. Patients were separated into 3 groups according to the knee deformity to investigate the distribution of FAO in each group., Results: The mean (SD) FAO was 2% (7%) for the knee varus group, 1% (6%) for the neutral knee group, and 4% (5%) for the valgus knee group ( P = .12). Fifty-three percent of patients with knee valgus showed a pathological hindfoot valgus ( P = .04). We found a positive but moderate correlation between hindfoot valgus and HKA (ρ = 0.53; P = .01). Female sex was associated with higher FAO (3% ± 4% vs 0.6% ± 6%; P = .009)., Conclusion: This feasibility study suggests a new opportunity using 3D biometrics to understand the relationship between knee and hindfoot alignment and to highlight different patterns of combined deformities in further investigations., Level of Evidence: Level III, comparative study.

Introduction: Pes cavovarus is a three-dimensional (3D) foot deformity. New 3D semi-automatic measurements utilising weightbearing computerised topography (WBCT) images have recently been proposed to assess hindfoot alignment, but reliability in pes cavovarus has never been investigated. The aim of this study was to assess intraobserver and interobserver reliability of the foot ankle offset (FAO), calcaneal offset (CO) and hindfoot alignment angle (HAA) in pes cavovarus., Methods: Anonymised WBCT datasets from 51 feet (17 Charcot-Marie-Tooth related cavovarus, 17 idiopathic cavovarus and 17 controls) were retrospectively reviewed. Three observers (two senior foot and ankle fellows and one orthopaedic resident) independently measured FAO, CO and HAA using dedicated software, with measurements repeated two weeks apart. Subgroup analysis was performed to assess whether aetiology or severity of varus deformity and level of seniority affected reliability., Results: Mean values for intra and interobserver reliability for FAO (r=0.98; ICC: 0.99), CO (r=0.97; ICC: 0.98) and HAA measurements (r=0.97; ICC: 0.98) were excellent. Subgroup analyses showed that FAO, CO and HAA's intra (r/ρ range, 0.77-0.95) and interobserver (ICC range, 0.88-0.98) reliability remained excellent in patients with Charcot-Marie-Tooth related cavovarus, idiopathic pes cavovarus and normal feet, regardless of the severity of deformity. No difference was found in FAO, CO and HAA mean values from three observers (p>0.05 in all cases)., Discussion: This study demonstrates that 3D semi-automatic measurements of WBCT images have excellent intra and interobserver reliability in the assessment of hindfoot alignment in pes cavovarus. Aetiology and severity of deformity, and level of seniority do not affect reliability of these measurements., Level of Evidence: Level III, retrospective comparative study., (Copyright © 2019 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.)

Background: We investigated the association between hindfoot residual malalignment assessed on weightbearing computed tomography (WBCT) images and the development of periprosthetic cysts (PPCs) after total ankle replacement (TAR). We hypothesized that PPCs would be found predominantly medially in the varus configuration and laterally in the valgus configuration., Methods: Cases of primary TAR with available WBCT imaging of the ankle were included in this retrospective study. The location of the PPC was marked and the following volumes were calculated: total (TCV), medial (MCV), central (CCV), and lateral (LCV) cyst volumes. Hindfoot alignment was measured as Foot and Ankle Offset (FAO), with 95% confidence intervals (95% CIs) calculated to define varus (<95% CI) and valgus (>95% CI) groups. Cyst volumes were compared between these 2 groups. The American Orthopaedic Foot & Ankle Society (AOFAS) score at the time of the WBCT was also retrieved. Receiver operating characteristic (ROC) curves were used to determine FAO thresholds for predicting an increased risk of PPC., Results: Forty-eight TARs (mean follow-up, 44.6 months) were included, 81% of which had at least 1 PPC. The mean FAO was 0.12% (95% CI, -1.12 to 1.36). Patients with greater residual malalignment ( P < .001) and those with longer follow-up ( P < .001) presented with increased TCV. In varus cases, the MCV was greater than the LCV ( P = .042), with a threshold FAO value of -2.75% or less predicting an increased MCV. In valgus cases, the LCV was greater than the MCV ( P = .049), with a FAO threshold value of 4.5% or more predicting an increased LCV., Conclusion: In this series, the PPC volume after primary TAR significantly correlated with postoperative hindfoot malalignment and longer follow-up., Level of Evidence: Level III, retrospective comparative series.

Introduction: In the treatment of osteoarthritis of the ankle, controversy persists between advocates of arthrodesis and of joint replacement., Hypothesis: Results of total ankle replacement (TAR) are equivalent to those of ankle arthrodesis (AA)., Material and Methods: A single-center continuous retrospective series included 50 patients (25 TAR, 25 AA) operated on by a single surgeon. TAR used the standard Salto ® mobile-bearing prosthesis, and arthrodesis used screws or plates. Results were assessed clinically on AOFAS score, visual analog scale (VAS) and satisfaction questionnaire, and radiologically on X-ray and CT. Survivorship in the 2 procedures was estimated on the Kaplan Meier method., Results: At a mean 67 months' follow-up (range, 40-105 months), mean AOFAS and VAS scores were significantly better in the AA group (74.1 and 1.9, respectively) than in the TAR group (67 and 3.5, respectively) (p<0.001). In the AA group, 80% of patients were satisfied or very satisfied, compared to 64% after TAR. Five-year survival without revision for non-union (AA) or implant removal (TAR) was similar between groups: AA, 96%; TAR, 90% (p=0.72). In contrast, survival with no revision procedures was significantly better with AA (96%) than TAR (75%) (p=0.03)., Discussion: At 5 years, surgical revision rates were significantly greater than after standard Salto ® mobile-bearing TAR than for arthrodesis, notably due to onset of cysts; we therefore decided to abandon this implant., Level of Evidence: IV, comparative retrospective study., (Copyright © 2018. Published by Elsevier Masson SAS.)

Background: Hindfoot alignment on 2D radiographs can present anatomical and operator-related bias. In this study, software designed for weightbearing computed tomography (WBCT) was used to calculate a new 3D biometric tool: the Foot and Ankle Offset (FAO). We described the distribution of FAO in a series of data sets from clinically normal, varus, and valgus cases, hypothesizing that FAO values would be significantly different in the 3 groups., Methods: In this retrospective cohort study, 135 data sets (57 normal, 38 varus, 40 valgus) from WBCT (PedCAT; CurveBeam LLC, Warrington, PA) were obtained from a specialized foot and ankle unit. 3D coordinates of specific anatomical landmarks (weightbearing points of the calcaneus, of the first and fifth metatarsal heads and the highest and centermost point on the talar dome) were collected. These data were processed with the TALAS system (CurveBeam), which resulted in an FAO value for each case. Intraobserver and interobserver reliability were also assessed., Results: In normal cases, the mean value for FAO was 2.3% ± 2.9%, whereas in varus and valgus cases, the mean was -11.6% ± 6.9% and 11.4% ± 5.7%, respectively, with a statistically significant difference among groups ( P < .001). The distribution of the normal population was Gaussian. The inter- and intraobserver reliability were 0.99 +/- 0.00 and 0.97 +/-0.02 Conclusions: This pilot study suggests that the FAO is an efficient tool for measuring hindfoot alignment using WBCT. Previously published research in this field has looked at WBCT by adapting 2D biometrics. The present study introduces the concept of 3D biometrics and describes an efficient, semiautomatic tool for measuring hindfoot alignment., Level of Evidence: Level III, retrospective comparative study.

Category: Hindfoot; Arthroscopy Introduction/Purpose: Supramalleolar osteotomies have been proposed as surgical option to realign the ankle joint in case of altered intra-articular loading. Little is known about the changes occurring at the tibiotalar joint after inframalleolar procedures, such as the corrective arthroscopic anterolateral subtalar arthrodesis (ALAPSTA). We set out to investigate changes in terms of joint interaction between the articular surfaces at the tibiotalar joint after corrective anterolateral arthroscopic subtalar arthrodesis (ALAPSTA) to treat Progressive Collapsing Foot Deformity (PCFD) with sinus tarsi impingement and subtalar joint degeneration. We hypothesized that ALAPSTA would improve hindfoot malalignment and that the distances between articular surfaces at the ankle would change significantly. Methods: In this retrospective study, we evaluated a consecutive series of 33 feet from 33 patients (mean age 60 years, SD 16.2; 16 right and 17 left) diagnosed with PCFD undergone ALAPSTA and reassessed at a mean follow-up of 7 months (range, 2 to 50). Weightbearing computed-tomography (WBCT) images were retrieved and the Foot and Ankle Offset (FAO) was calculated to assess the hindfoot alignment. Distance Mapping (DM) at the ankle joint (divided in 9 regions) allowed to assess changes in terms of joint interaction at this level between pre and postoperative images. Results: Hindfoot alignment significantly improved with a pre-operative FAO at 10.7 points (SD 4.7) and a post-operative FAO at 4.8 (SD 4.9) (p < 0.001). The mean improvement was 5.6 points. We found a significant increase in mean distances occurring posterolaterally at the ankle (from 4.5 mm (SD 1.2) to 5.4 mm (SD 1.5), p< 0.001) along with a significant decrease occurring anteromedially (from 9.1 mm (SD 1.2) to 8.3 mm (SD 1.4), p< 0.001). Conclusion: In this series, ALAPSTA was effective at correcting hindfoot malalignment in PCFD. After the procedure, the interaction at the ankle joint significantly changed with a reduction of anteromedial distance and an increase of posterolateral distance. Inframalleolar procedures seem to alter significantly the interaction between the tibia and the talus at the ankle. Further studies are warranted to ascertain whether changes in distances between surfaces correspond to changes in intra-articular pressures. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Ankle arthrodesis, well-known as a reliable option to treat end-stage ankle osteoarthritis (AO), may be fixed using screws in various configurations. The purpose of this study was to determine whether the number of screws and the use of a lateral distal fibular autograft during the procedure might influence the union and complication rate. We hypothesized that a greater number of screws and the use of a fibular autograft might increase the union rate and reduce the number of complications. Methods: Following the PRISMA-compliant PROSPERO-registered checklist, the Medline, Scopus, Web of Science and Cochrane databases were searched, including studies reporting patients affected by AO and undergone Ankle Arthrodesis (AA) using screws as exclusive fixation method. Data were harvested regarding the cohort (sample size, age, sex, etiology), the study design (type of study, level of evidence), the surgical technique (open/arthroscopic procedure, the number of screws, the use of autograft) and the final outcome (union, complication and reoperation rate) at the longest follow-up. The risk of bias was assessed using the modified Coleman Methodology Score (mCMS) was used to assess the methodological quality of studies. Three groups were built based on the type of fixation: arthrodeses fixed with 2 screws (Group 1, G1), with 3 screws (Group 2, G2), and those augmented with a lateral fibular autograft (Group 3, G3). Results: Twenty series of patients from nineteen studies (732 ankles) were selected (G1=252 ankles, G2=209, G3=271). The pooled proportion estimate revealed a similar nonunion rate in the 2-screw group as compared to the 3-screw group (6% vs 1%; p=0.43) The pooled proportion of complications appeared higher in G1 (18%) than in G2 (8%) but it was not significantly different either (p=0.27). After exclusion of 'symptomatic hardware and screw removal' the difference was still not significant (p=0.62) although it resulted lower in G1 than in G2 (3% vs 8%, respectively). The pooled proportion of nonunions (p=0.48) and complications (p=0.76) did not differ between the AA performed without or with a fibular autograft. Conclusion: Fixation of Ankle Arthrodesis using three screws as compared to two screws seems to be advantageous in terms of reduced risk of nonunion and complications, although the difference did not achieve statistical significance in this study. The use of an adjuvant lateral distal fibular autograft does not seem to significantly increase the chances of fusion as compared to a noautograft construct. The evidence provided so far is based on retrospective and short-term follow-up studies of moderate methodological quality. Further comparative and prospective analyses are warranted to define how to achieve the best outcome in Ankle Arthrodesis stabilized using screws. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: In varus-type osteoarthritis of the ankle (VAOA), it is known that the subtalar joint compensates in valgus/eversion for the malalignment of the tibiotalar joint. However, previous studies were mainly based on X-ray measurements and did not take into account peri-talar changes that extend to the subtalar and Chopart joints. Furthermore, the effect on peritalar compensation when tibio-talar arthrodesis is performed is still unclear. Distance Mapping (DM) is a technology that can produce a 3D point-to-point distance map of joint interactions from cone beam weight bearing CT (WBCT) images. The purpose of this study was to quantify the peri-talar changes that occur when the tibiotalar joint is fused. We hypothesized that talar varus would improve and that the Chopart/Subtalar joint complex would present compensatory varus/inversion. Methods: The subjects were 14 patients (15 feet) who underwent arthrodesis for VAOA at our institution. The average postoperative follow-up period was 6.6 months. Foot alignment (Foot Ankle Offset (FAO)) was measured from WBCT datasets pre and postoperatively. The pre to post op shift vectors of the weighted distance maps center points were measured for the tibiotalar, subtalar, calcaneocuboid and talonavicular joints. Statistical analysis was performed by paired T-test, and the significance level set at p<0.05. Results: FAO improved significantly from preoperative -12.9 +-7.4 % to postoperative -6.4 +-3.9 %. The DM vectors were 4.9 +- 2.8 mm (lateral direction) for the tibiotalar joint, 0.86 +-0.93 mm (posterior) for the subtalar joint and 4.9 +-2.6 mm (plantarmedial) for the talonavicular joint. Conclusion: The main finding in this study was that foot alignment was improved following tibiotalar arthrodesis with peritalar compensation, more so in the talonavicular than in the subtalar joint and not in the calcaneocuboid joint. The limitations of this study include the small number of cases and the short postoperative follow-up. Our results suggest that the flexibility of the talonavicular joint may be necessary when arthrodesis is performed on VAOA to contribute to the alignment correction. If it is not the case, TAR could be considered an alternative. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Abnormal Hindfoot Alignment (HA) has been correlated with increased complication rates in ankle fusion or replacement. Altered Bone Mineral Density (BMD) due to abnormal stress distribution could be predisposing factor for those unwanted outcomes. The objective of this study was to assess spatial distribution of BMD around the ankle joint in patients with normal or abnormal HA using cone beam Weight Bearing CT. Methods: Retrospective comparative study including 81 ankles allocated into 3 groups based on the Foot Ankle Offset (FAO): 27 normal (0%5%). groups were comparable by age (p=0.967), Body Mass Idex (p=0.669), sex (p=0.820) and side (p=0.708). Semiautomatic segmentation (BoneLogic, Disior) was applied to identify bones. Tibia and talus were digitally compartmented in medial (M) and lateral (L) volumes relative to the median sagittal plane. Mean Hounsfield Unit (HU) value per compartment was used to assess BMD and to calculate the Medial over Lateral HU ratio (M/L-HU). Comparisons among the three groups were performed using one-way ANOVA, Kruskal-Wallis and Chi2 tests. Results: Mean +- standard deviation HU values in the compartments in normal cases were 495.2+-110 (medial tibia), 495.6+- 108.1 (lateral tibia), 368.9+-80.3 (medial talus), 448.2+-90.6 (lateral talus) and 686.7+-120.4 (fibula). Upon comparison of the mean BMD value for each compartment in the three groups, the difference did not achieve statistical significance. Conversely, the tibia HU-M/L ratio (0.88+-0.14 in valgus cases, 0.99 +- 0.08 in normally-aligned cases and 1.04+-0.08 in varus cases) and the talar HUM/ L ratio (0.68+-0.18 in valgus cases, 0.82+-0.08 in normally-aligned cases and 0.96+-0.20 in varus cases) were significantly different in the three groups (p<0.001). Conclusion: We found that the BMD in distal tibia, fibula and the talus varies with hindfoot alignment. The increased HU mediolateral ratio in varus cases was consistent with a greater medial bone density in the tibia and talus, while the decreased ratio found in valgus cases suggested a more lateral concentration in both bones. This data supports the role of WBCT in analyzing BMD distribution. This method could be clinically useful in ankle OA to evaluate bone quality for such considerations as surgical indications or implant positioning. [ABSTRACT FROM AUTHOR]