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Background: Tendinopathy alters the compositional properties of the Achilles tendon by increasing fluid and glycosaminoglycan content. It has been speculated that these changes may affect intratendinous pressure, but the extent of this relationship remains unclear. Therefore, we aimed to investigate the impact of elevated fluid and glycosaminoglycan content on Achilles tendon intratendinous pressure and to determine whether hyaluronidase (HYAL) therapy can intervene in this potential relationship. Methods: Twenty paired fresh-frozen cadaveric Achilles tendons were mounted in a tensile-testing machine and loaded up to 5% strain. Intratendinous resting (at 0% strain) and dynamic pressure (at 5% strain) were assessed using the microcapillary infusion technique. First, intratendinous pressure was measured under native conditions before and after infusion of 2 mL physiological saline. Next, 80 mg of glycosaminoglycans were administered bilaterally to the paired tendons. The right tendons were additionally treated with 1500 units of HYAL. Finally, both groups were retested, and the glycosaminoglycan content was analyzed. Results: It was found that both elevated fluid and glycosaminoglycan content resulted in higher intratendinous resting and dynamic pressures (p

Purpose: Emerging reports suggest an important involvement of the ankle/hindfoot alignment in the outcome of knee osteotomy; however, a comprehensive overview is currently not available. Therefore, we systematically reviewed all studies investigating biomechanical and clinical outcomes related to the ankle/hindfoot following knee osteotomies. Methods: A systematic literature search was conducted on PubMed, Web of Science, EMBASE and Cochrane Library according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered on international prospective register of systematic reviews (PROSPERO) (CRD42021277189). Combining knee osteotomy and ankle/hindfoot alignment, all biomechanical and clinical studies were included. Studies investigating knee osteotomy in conjunction with total knee arthroplasty and case reports were excluded. The QUality Appraisal for Cadaveric Studies (QUACS) scale and Methodological Index for Non-Randomized Studies (MINORS) scores were used for quality assessment. Results: Out of 3554 hits, 18 studies were confirmed eligible, including 770 subjects. The minority of studies (n = 3) assessed both high tibial- and distal femoral osteotomy. Following knee osteotomy, the mean tibiotalar contact pressure decreased (n = 4) except in the presence of a rigid subtalar joint (n = 1) or a talar tilt deformity (n = 1). Patient symptoms and/or radiographic alignment at the level of the ankle/hindfoot improved after knee osteotomy (n = 13). However, factors interfering with an optimal outcome were a small preoperative lateral distal tibia angle, a small hip–knee–ankle axis (HKA) angle, a large HKA correction (>14.5°) and a preexistent hindfoot deformity (>15.9°). Conclusions: Osteotomies to correct knee deformity alter biomechanical and clinical outcomes at the level of the ankle/hindfoot. In general, these changes were beneficial, but several parameters were identified in association with deterioration of ankle/hindfoot symptoms following knee osteotomy.

Background: Given the inherent variability in walking speeds encountered in day-to-day activities, understanding the corresponding alterations in ankle biomechanics would provide valuable clinical insights. Therefore, the objective of this study was to examine the influence of different walking speeds on biomechanical parameters, utilizing gait analysis and musculoskeletal modelling.Methods: Twenty healthy volunteers without any lower limb medical history were included in this study. Treadmill-assisted gait-analysis with walking speeds of 0.8 m/s and 1.1 m/s was performed using the Gait Real-time Analysis Interactive Lab (GRAIL®). Collected kinematic data and ground reaction forces were processed via the AnyBody® modeling system to determine ankle kinetics and muscle forces of the lower leg. Data were statistically analyzed using statistical parametric mapping to reveal both spatiotemporal and magnitude significant differences.Results: Significant differences were found for both magnitude and spatiotemporal curves between 0.8 m/s and 1.1 m/s for the ankle flexion (p < 0.001), subtalar force (p < 0.001), ankle joint reaction force and muscles forces of the M. gastrocnemius, M. soleus and M. peroneus longus (α = 0.05). No significant spatiotemporal differences were found between 0.8 m/s and 1.1 m/s for the M. tibialis anterior and posterior.Discussion: A significant impact on ankle joint kinematics and kinetics was observed when comparing walking speeds of 0.8 m/s and 1.1 m/s. The findings of this study underscore the influence of walking speed on the biomechanics of the ankle. Such insights may provide a biomechanical rationale for several therapeutic and preventative strategies for ankle conditions.

Abstract Detection of syndesmotic ankle instability remains challenging in clinical practice due to the limitations of two-dimensional (2D) measurements. The transition to automated three-dimensional (3D) measurement techniques is on the verge of a breakthrough but normative and side-to-side comparative data are missing. Therefore, our study aim was two-fold: (1) to establish 3D anatomical reference values of the ankle syndesmosis based on automated measurements and (2) to determine to what extent the ankle syndesmosis is symmetric across all 3D measurements. Patients without syndesmotic pathology with a non-weight-bearing CT scan (NWBCT; N = 38; Age = 51.6 ± 17.43 years) and weight-bearing CT scan (WBCT; N = 43; Age = 48.9 ± 14.3 years) were retrospectively included. After training and validation of a neural network to automate the segmentation of 3D ankle models, an iterative closest point registration was performed to superimpose the left on the right ankle. Subsequently, 3D measurements were manually and automatically computed using a custom-made algorithm and side-to-side comparison of these landmarks allowed one to investigate symmetry. Intra-observer analysis showed excellent agreements for all manual measurements (ICC range 0.85–0.99) and good (i.e. 0.05). In clinical practice, our novel algorithm could surmount the current limitations of manual 2D measurements and distinguish patients with a syndesmotic ankle lesion from normal variance.

Category: Sports; Trauma Introduction/Purpose: Syndesmotic ankle injuries are present in one-fourth of all ankle trauma and may lead to syndesmotic instability or posttraumatic ankle osteoarthirtis on the long term. At present, they continue to impose a diagnostic dilemma our clinical practice. While magnetic resonance imaging lacks application of load to the ankle joint, plain weightbearing radiographs are skewed by superposition of the osseous structures. The recent advent of weightbearing cone-beam CT (WBCT) overcomes these drawbacks by imaging both ankles during bipedal stance. However, it remains debated whether syndesmotic ankle injuries should be imaged under weightbearing conditions and/or during application of external rotation. Therefore, we aimed to implement both weightbearing and external rotation in the assessment of syndesmotic ankle injuries using WBCT imaging combined with 3D measurement techniques. Methods: In this retrospective study, patients with an acute syndesmotic ankle injury were analyzed using a WBCT (N= 21; Age= 31.64±14.07 years 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. For the external rotation protocol, the patient was asked to internally rotate the shin while ensuring that the foot remained firmly plantigrade until pain (Visual Analogue Scale > 8/10) or a maximal range of motion was reached. 3D models were generated from the CT slices. Tibiofibular displacement and Talar Rotation were quantified by automated 3D measurements using a custom-made Matlab® script; Anterior Tibiofibular distance (ATFD), Alpha angle, posterior Tibiofibular distance (PTFD) and Talar rotation (TR) angle in comparison to the contralateral non-injured ankle. Results: 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 (P = 0.492; P = 0.152, respectively). Conclusion: Application of combined weightbearing-external rotation reveals an increased ATFD in patients with syndesmotic ligament injuries (Figure 1). 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, future studies are required to determine cut-off values that may indicate the amount of displacement that might lead to chronic instability and require a certain type of treatment strategy.

Category: Ankle; Trauma Introduction/Purpose: Approximately 10-15% of posterior malleolar fractures (PMFs) are "small shell," extra-articular fragments. Current classification systems present difficulties to perform a uniform typification of PMFs and contain no consensus on whether they should be fixed. Anatomical studies have identified two distinct components of the posterior inferior tibiofibular ligament (PITFL); the superficial band is thought to be more important than its deep counterpart in imparting syndesmotic stability. However, the involvement of one or both bands of the PITFL by small shell PMFs has not been evaluated so far. Hence, we conducted this study to perform 3D mapping of small shell PMFs and to determine whether surgeons should fix these routinely. Methods: Ankle fracture patients with a ‘small shell’ PMF (Haraguchi 3/Mason 1/Bartoníček 1 or 2) were included. Demographics, radiological features, treatment, and outcomes were recorded. 3D models of the fractured tibiae were generated from CT scans and superimposed on a statistical shape model of the right tibia, which served as a template. Fracture lines along with footprints of superficial and deep PITFL were marked on the template. 3D fracture heat maps were generated. Size of the fracture fragments and involvement of the superficial and deep PITFL footprints were quantified using a custom MATLAB script (Figure 1). Sparing of the footprint was defined as an overlap of < 1% between the fracture line and the footprint areas. Odds ratios (OR) with 95% confidence intervals (CI) were determined to determine which variables correlated with sparing of the PITFL footprint; P-values of < 0.05 were considered significant. Results: Thirty-nine patients were included. The superficial PITFL footprint was spared in 15 (38%), deep PITFL in 10 (26%), and both in 4 cases (10%). Males and Weber C fractures had a higher likelihood of sparing the superficial and deep PITFL footprints, respectively (P = 0.04). Supination external rotation (SER) patterns were less likely to demonstrate syndesmotic widening if either PITFL footprint was spared. Direct fixation of the PMF was done in 1 case; syndesmotic fixation in 25 cases and in 14 cases, no syndesmotic fixation was done. Of these, 11 were SER injuries where stability was achieved after fixation of medial and lateral malleoli. In 1 SER and pronation external rotation (PER) injury case, the syndesmosis was stable after fixation of a large Chaput fragment. Conclusion: This study demonstrated that 48% of small shell PMFs spare either the superficial or deep footprint of the PITFL; in 10% both PITFL footprints were spared. Hence, 58 % of small-shell PMFs may not benefit from direct fixation. Additionally, SER injuries with small shell PMFs that spare either PITFL footprint may not demonstrate radiographic instability and may not need direct or indirect fixation after addressing other components of the ankle fracture. However, given the fact that syndesmotic stability is not dictated by the PITFL alone, it remains prudent to stress the syndesmosis per-operatively to determine if syndesmotic fixation is needed.

Category: Hindfoot; Sports Introduction/Purpose: The use of a dorsal closing wedge calcaneal osteotomy (DCWCO) in the treatment of insertional Achilles tendinopathy (IAT) has recently gained popularity. The anatomical changes imposed by the osteotomy are believed to improve both the biological and mechanical processes involved in IAT. However, the impact of shortening the Achilles leverage arm after DCWCO and the full impact of DCWCO on foot anatomy and function is not well understood. This study aimed to examine the effects of DCWCO on the 3D alignment and biomechanics of the foot and ankle in IAT patients through simulated models of DCWCO. The hypothesis was that DCWCO would significantly impact foot alignment and decrease gastrocsoleus lever arm. Methods: Six weightbearing ankle CTs of patients with IAT were identified from the clinical database. Bone segmentation was performed and DCWCOs were conducted in standardized planes with six variations, resulting in a total of 36 foot models. Two plantar osteotomy starting points were defined as 1-cm anterior (posterior osteotomy) and 2-cm anterior (anterior osteotomy) to the most plantar point of calcaneus. The osteotomies were extended to dorsal surface at 1-cm anterior to posterosuperior calcaneus with 6, 10, or 14-mm wedges anteriorly. After the osteotomies, the posterior part of the calcaneus was rotated around the plantar starting point until proper bone contact was achieved. Achilles reconstruction was also performed using pre-defined Achilles insertion points. All models were then transferred to a MATLAB-based algorithm for automated measurements. These measurements included talocalcaneal, calcaneal pitch, Böhler, and Achilles tendon sagittal angles, Achilles moment arm, Achilles- posterosuperior calcaneus distance, and difference in soleus-Achilles length. Results: Anteriorly placed osteotomy caused more significant decrease in the Böhler angle (p < 0.001). Evaluation of the posteriorly placed osteotomy separately showed no significant decrease in the Böhler angle for patients with more than 30- degrees of preoperative Böhler angle (p=0.26). However, patients with a preoperative Böhler angle less than 30-degrees showed a significant decrease, approaching values close to 5-degrees (p=0.004). Gastrocsoleus moment arm decrease was found to be 2-3% by using force/moment equation. The change in the distance between Achilles tendon and the posterosuperior calcaneus was similar between anterior and posterior osteotomies, with less than 3-mm in a 6-mm wedge and more than 5-mm in a 10-mm wedge osteotomy. The calculations showed that ankle dorsiflexion can increase by one degree for each mm of resection. Conclusion: An anteriorly placed starting point for a DCWCO can negatively affect foot alignment and offer limited benefits for Achilles decompression. If the preoperative Böhler angle is less than 30, a DCWCO can significantly decrease the Böhler angle, potentially putting the subtalar joint at risk for arthritis by increasing the load as reported by some finite element studies. The maximum decrease in gastrocsoleus power is less than 3%, which may be clinically insignificant. A posterior starting point with 10- mm wedge can be adequate to move Haglund around 5-mm anteriorly and can move Achilles insertion 10-mm superiorly to decrease tension.

Category: Trauma; Ankle Introduction/Purpose: Weber-B ankle fractures represent an increasingly common injury world-wide, and the decision for operative fixation often hinges on the stability and congruency of the ankle. While tibiotalar displacement is typically evaluated using the medial clear space on plain radiographs, this method remains prone to inaccuracy because of x-ray beam rotation and manual measurement errors. Furthermore, the influence of these fractures on the mechanical environment of the ankle remains unknown. The recent advent of weightbearing cone-beam CT (WBCT) overcomes these drawbacks by imaging during bipedal stance, allowing a 3D anatomical and mechanical analysis. Therefore, the aim of this study was to analyze the 3D mortise displacement and contact mechanics in weber B ankle fractures by use of WBCT in comparison to their healthy contralateral side. Methods: In this retrospective study, our ankle trauma database was searched for Weber-B ankle fractures imaged by bilateral WBCT imaging between 2015 and 2022. Exclusion criteria consisted of metal or motion artifacts, presence of ankle osteoarthritis, and an age less than 18 years or more than 75 years. Segmentation into 3D models of bone was performed semi-automatically, while personalized cartilage layers were modeled based on a previously validated methodology. Bilateral ankle models were imported in custom-made Matlab® script for an automated anatomical and mechanical analysis. 3D mortise congruency was evaluated by use of following parameters: fibular length, talocrural angle, distance mapping of the medial gutter and tibiofibular clear space distance mapping. Contact mechanics were evaluated by the mean and maximum contact stress of the tibia and talus, as well as the contact area (Figure 1). A student’s T-test was performed to investigate the difference between the fractured and healthy side. Results: Thirty-two patients, with mean age 38.50 years (SD = 15.81 ) and weight 79.12 kg (SD = 16,24), were confirmed eligible for analysis. Statistical analysis revealed that there were no significant differences for all anatomical parameters (P > 0.05). The mean contact stress of the fractured and healthy side was 2.10 (SD = 0.42) MPa and 2.10 (SD = 0,41) MPa, respectively, whereas the maximum stress was 7.67 MPa (SD = 1.55) and 7,47 MPa (SD = 1,67), respectively. No statistical significant differences were found between all mechanical parameters (P > 0.05). Conclusion: This study demonstrates that contact mechanics are not affected in Weber-B fractures with a congruent mortise. Therefore, non-operative treatment could be considered, as there will theoretically be no increased risk for the patients to develop posttraumatic osteoarthritis in the long term. In clinical practice, WBCT could prove useful to determine the 3D anatomical and mechanical environment of ankle fractures and guide patients towards (non-) operative treatment. However, further studies should focus on the minimal clinical important difference/rehabilitation factors associated with mortise malalignment based on concomitant contact stress increase, which would warrant and identify which cases need surgical reduction.

Background and Objective: As in vivo measurements of knee joint contact forces remain challenging, computational musculoskeletal modeling has been popularized as an encouraging solution for non-invasive estimation of joint mechanical loading. Computational musculoskeletal modeling typically relies on laborious manual segmentation as it requires reliable osseous and soft tissue geometry. To improve on feasibility and accuracy of patient-specific geometry predictions, a generic computational approach that can easily be scaled, morphed and fitted to patient-specific knee joint anatomy is presented.Methods: A personalized prediction algorithm was established to derive soft tissue geometry of the knee, originating solely from skeletal anatomy. Based on a MRI dataset (n = 53), manual identification of soft-tissue anatomy and landmarks served as input for our model by use of geometric morphometrics. Topographic distance maps were generated for cartilage thickness predictions. Meniscal modeling relied on wrapping a triangular geometry with varying height and width from the anterior to the posterior root. Elastic mesh wrapping was applied for ligamentous and patellar tendon path modeling. Leave-one-out validation experiments were conducted for accuracy assessment.Results: The Root Mean Square Error (RMSE) for the cartilage layers of the medial tibial plateau, the lateral tibial plateau, the femur and the patella equaled respectively 0.32 mm (range 0.14–0.48), 0.35 mm (range 0.16–0.53), 0.39 mm (range 0.15–0.80) and 0.75 mm (range 0.16–1.11). Similarly, the RMSE equaled respectively 1.16 mm (range 0.99–1.59), 0.91 mm (0.75–1.33), 2.93 mm (range 1.85–4.66) and 2.04 mm (1.88–3.29), calculated over the course of the anterior cruciate ligament, posterior cruciate ligament, the medial and the lateral meniscus.Conclusion: A methodological workflow is presented for patient-specific, morphological knee joint modeling that avoids laborious segmentation. By allowing to accurately predict personalized geometry this method has the potential for generating large (virtual) sample sizes applicable for biomechanical research and improving personalized, computer-assisted medicine.

Abstract The co-creation and sharing of knowledge among different types of actors with complementary expertise is known as the Multi-Actor Approach (MAA). This paper presents how Horizon2020 Thematic-Networks (TNs) deal with the MAA and put forward best practices during the different project phases, based on the results of a desktop study, interviews, surveys and expert workshops. The study shows that not all types of actors are equally involved in TN consortia and participatory activities, meaning TNs might be not sufficiently demand-driven and the uptake of the results is not optimal. Facilitators are key to contributing to the relationships and the mutual understanding between different actors. Moreover, a user-friendly digital knowledge platform linked to demonstration activities and peer-to-peer exchange can improve the sharing of knowledge, enhancing impact in agricultural and forestry innovation in the longer term.

Understanding the mechanisms of hip disease, such as osteoarthritis (OA), is crucial to advance their treatment. Such hip diseases often involve specific morphological changes. Genetic variations, called single nucleotide polymorphisms (SNPs), influence various hip morphological parameters. This study investigated the biological relevance of SNPs correlated to hip morphology in genome-wide association studies (GWAS). The SNP-associated genes were compared to genes associated with OA in other joints, aiming to see if the same genes play a role in both hip development and the risk of OA in other lower limb joints. A systematic literature review was conducted to identify SNPs correlated with hip morphology, based on the Population, Intervention, Comparison, Outcome, and Study (PICOS) framework. Afterwards, Gene Ontology (GO) analysis was performed, using EnrichR, on the SNP-associated genes and compared with non-hip OA-associated genes, across different databases. Reviewing 49 GWAS identified 436 SNPs associated with hip joint morphology, encompassing variance in bone size, structure and shape. Among the SNP-associated genes, SOX9 plays a pivotal role in size, GDF5 impacts bone structure, and BMP7 affects shape. Overall, skeletal system development, regulation of cell differentiation, and chondrocyte differentiation emerged as crucial processes influencing hip morphology. Eighteen percent of GWAS-identified genes related to hip morphology were also associated with non-hip OA. Our findings indicate the existence of multiple shared genetic mechanisms across hip morphology and OA, highlighting the necessity for more extensive research in this area, as in contrast to the hip, the genetic background on knee or foot morphology remains largely understudied. [ABSTRACT FROM AUTHOR]

Despite various proposed measurement techniques for assessing syndesmosis integrity, a standardized protocol is lacking, and the existing literature reports inconsistent findings regarding normal and abnormal relationships between the fibula and tibia at the distal level. Therefore, this study aims to present an overview of two- (2D) and three-dimensional (3D) measurement methods utilized to evaluate syndesmosis integrity. A topical literature review was conducted, including studies employing 2D or 3D measurement techniques to quantify distal tibiofibular syndesmosis alignment on computed tomography (CT) or weight-bearing CT (WBCT) scans. A total of 49 eligible articles were included in this review. While most interclass correlation (ICC) values indicate favorable reliability, certain measurements involving multiple steps exhibited lower ICC values, potentially due to the learning curve associated with their implementation. Inconclusive results were obtained regarding the influence of age, sex, and height on syndesmotic measurements. No significant difference was observed between bilateral ankles, permitting the use of the opposite side as an internal control for comparison. There is a notable range of normal and pathological values, as evidenced by the standard deviation associated with each measurement. This review highlights the absence of a consensus on syndesmotic measurements for assessing integrity despite numerous CT scan studies. The diverse measurement techniques, complexity, and inconclusive findings present challenges in distinguishing between normal and pathological values in routine clinical practice. Promising advancements in novel 3D techniques offer potential for automated measurements and reduction of observer inaccuracies, but further validation is needed.

Category: Hindfoot; Ankle Introduction/Purpose: Several emerging reports suggest an important involvement of the hindfoot alignment in the outcome of knee osteotomy. At present these studies are scattered across the literature and lack a comprehensive overview. Therefore, we aimed to systematically review all biomechanical and clinical studies investigating the role of the hindfoot alignment in the setting of osteotomies around the knee. Methods: A systematic literature search was conducted on following databases: Pubmed, EMBASE, Cochrane Library and Web of Science. Search terms consisted of 'knee osteotomy' combined with 'hindfoot/ankle alignment'. Inclusion criteria were all English language studies analyzing the association between knee osteotomy and hindfoot alignment comprising biomechanical or clinical outcomes. Exclusion criteria consisted of knee osteotomy performed in conjunction with total knee arthroplasty and level V studies. A quality assessment was conducted using the Quality Appraisal for Cadaveric Studies (QUACS) - and modified methodologic index for non-randomized studies (MINORS) scales. This protocol was performed according to the PRISMA guidelines and registered on PROSPERO (CRD42021277189). Results: Eighteen studies were confirmed eligible and consisted of a cadaveric (n=3) -, retrospective cohort (n=14) - and case- control (n=2) study design. Following knee osteotomy, biomechanical hindfoot characteristics were also positively affected (n=4), except in rigid subtalar joint (n=1) or talar tilt (n=1) deformity. Patient symptoms and/or radiographic alignment (Fig. 1a) at the level of the hindfoot did also improve after knee osteotomy (n=13). However this did not apply in case of a small pre-operative lateral distal tibia- and hip knee ankle (HKA) angulation (Fig. 1b) or in case of a large HKA correction (>14.5°). Additionally, a pre- existent hindfoot deformity (>15.9°) was associated with undercorrection of lower limb alignment following knee osteotomy. The mean QUACS score was 61.3% (range: 46-69%) and mean MINORS score was 9.2 out of 16 (range 6-12) for non-comparative and 16.5 out of 24 (range 15-18) for comparative studies. Conclusion: Osteotomies performed to correct knee deformity have also an impact on biomechanical and clinical outcomes of the hindfoot. In general, these are reported to be beneficial, but several parameters were identified that are associated with newly onset - or deterioration of hindfoot symptoms following knee osteotomy. These results should be interpreted in light of the moderate methodological quality of the included studies. Therefore, further prospective studies are warranted to assess how diagnostic and therapeutic algorithms based on the identified criteria could be implemented to optimize the overall outcome of knee osteotomy in relation to the foot and ankle.

Category: Trauma; Ankle Introduction/Purpose: Forced external rotation is hypothesized as the key mechanism of syndesmotic ankle injuries, inducing a three-dimensional deviation from the normal distal tibiofibular joint alignment. These lesions, especially when subtle, present a deceitful diagnostic challenge. Current diagnostic imaging modalities are impeded by a two-dimensional assessment, without considering ligamentous stabilizers. Accurate diagnosis of syndesmotic lesions should involve 3D weightbearing osseous imaging in combination with - preferably automated- inclusion of patient-specific ligamentous information. Therefore, our aim is two-fold: (1) to construct a three-dimensional articulated statistical shape model of the normal distal tibiofibular joint with inclusion of ligamentous morphometry and (2) to detect differences in predicted syndesmotic ligament length of patients with syndesmotic lesions with respect to normative data. Methods: Training data comprised non-weightbearing CT scans from asymptomatic controls (N= 76, Mean age 63 +/- 19 years), weightbearing CT scans from patients with syndesmotic ankle injury (N = 13, Mean Age 35 +/- 15 years) and their weightbearing healthy contralateral side (N = 13). CT scan segmentation was used to generate 3D bone models in the control and patient group. All ankles were aligned based on the tibia. Path and length of the syndesmotic ligaments were predicted using a discrete element model, wrapped around bony contours. Statistical shape model evaluation was based on accuracy, generalization and compactness. The predicted ligament length in patients with syndesmotic lesions was compared to healthy controls by use of two-tailed Two- Sample student's t-test. Results: Our presented skeletal shape model described the training data with an accuracy of 0.23 +/- 0.028 mm. Mean prediction accuracy of ligament insertions was 0.53 +/- 0.12 mm. Mean length of the Anterior inferior tibiofibular ligament was 12.26 +- 1.89mm for the control cases, 12.32 +- 1.58 mm for the contralateral cases and 14.13 +- 1.48 mm for the cases with syndesmotic lesions. Statistically significant differences were found between the latter two (95% CI [ 0.323.29], p = 0.017) There was a significant correlation between presence of syndesmotic injury and the positional alignment between the distal tibia and fibula (r = 0.873, p < 0,001). Conclusion: Statistical shape modelling combined with patient-specific ligament wrapping techniques can facilitate the diagnostic workup of syndesmotic ankle lesions under weightbearing conditions. In doing so, an increased anterior tibiofibular distance was detected, corresponding to an 'anterior open-book injury' of the ankle syndesmosis as a result of anterior inferior tibiofibular ligament elongation/rupture (Figure 1).

ABSTRACT Imaging plays a key role in the preoperative diagnosis, surgical planning, and postsurgical assessment of the foot, ankle, and knee pathologies. Interpreting diagnostic imaging accurately is crucial for the clinical practice of orthopedic surgeons. Although among the most used imaging modalities, radiographic assessments are amenable to errors for various technical reasons and superposition of bones. Computed tomography (CT) is a conventional imaging procedure that provides high-resolution images, but fails in considering a truly weight-bearing (WB) condition. In an attempt to overcome this limitation, WB cone beam CT technology has being successfully employed in the clinical practice for the past decade. Besides economically viable and safe, the WB cone beam CT considers WB conditions and provides high-quality scans, thus allowing an equitable and correct interpretation. This review aims to address extensive description and discussion on WBCT, including imaging quality; costs; time consumption; and its applicability in common foot, ankle, and knee, conditions. With this technology increasing popularity, and considering the extensive literature on medical research, radiologists and orthopedic surgeons need to understand its potential applications and use it optimally. Level of Evidence III, Systematic review of level III studies.

• Intratendinous pressure of the Achilles tendon increases during tensile loading. It is unknown whether tendinopathic changes, namely fluid and glycosaminoglycan accumulation, may impact this. • Intratendinous pressure of 20 Achilles tendons was measured at rest and during loading under natural conditions and after administration of fluid and glycosaminoglycans. Additionally, half of the tendons were treated with hyaluronidase. • Elevated fluid and glycosaminoglycan content resulted in higher intratendinous pressures. Hyaluronidase reduced glycosaminoglycan content and lowered intratendinous pressures. • These findings show that fluid and glycosaminoglycan accumulation lead to increased intratendinous pressures and that hyaluronidase may serve as a potential treatment by restoring intratendinous pressures. Tendinopathy alters the compositional properties of the Achilles tendon by increasing fluid and glycosaminoglycan content. It has been speculated that these changes may affect intratendinous pressure, but the extent of this relationship remains unclear. Therefore, we aimed to investigate the impact of elevated fluid and glycosaminoglycan content on Achilles tendon intratendinous pressure and to determine whether hyaluronidase (HYAL) therapy can intervene in this potential relationship. Twenty paired fresh-frozen cadaveric Achilles tendons were mounted in a tensile-testing machine and loaded up to 5% strain. Intratendinous resting (at 0% strain) and dynamic pressure (at 5% strain) were assessed using the microcapillary infusion technique. First, intratendinous pressure was measured under native conditions before and after infusion of 2 mL physiological saline. Next, 80 mg of glycosaminoglycans were administered bilaterally to the paired tendons. The right tendons were additionally treated with 1500 units of HYAL. Finally, both groups were retested, and the glycosaminoglycan content was analyzed. It was found that both elevated fluid and glycosaminoglycan content resulted in higher intratendinous resting and dynamic pressures (p < 0.001). HYAL treatment induced a 2.3-fold reduction in glycosaminoglycan content (p = 0.002) and restored intratendinous pressures. The results of this study demonstrated that elevated fluid and glycosaminoglycan content in Achilles tendinopathy contribute to increased intratendinous resting and dynamic pressures, which can be explained by the associated increased volume and reduced permeability of the tendon matrix, respectively. HYAL degrades glycosaminoglycans sufficiently to lower intratendinous pressures and may, therefore, serve as a promising treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Weightbearing computed tomography (WBCT) scans allow for a better understanding of foot alignment in patients suffering from progressive collapsing foot deformity (PCFD). However, soft tissue integrity (eg, spring ligament complex or tibialis posterior tendon) cannot be easily assessed via WBCT. As performing both WBCT and magnetic resonance imaging (MRI) might not be cost effective, we aimed to assess whether there is an association between osseous and soft tissue findings in WBCT and MRI. Methods: In this observational study, a consecutive cohort of 24 patients of various stages of PCFD (mean age 51 ± 18 years) underwent WBCT scans and MRI. Twenty-four healthy individuals of similar age, body mass index (BMI), and sex with WBCT scans were used as a control group. In addition to of osseous sinus tarsi impingement, 4 commonly used 3-dimensional (3D) measurements (talocalcaneal overlap [TCO], talonavicular coverage [TNC], Meary angle [MA], axial/lateral) were obtained using a dedicated postprocessing software (DISIOR 2.1, Finland) on the WBCT data sets. Sinus tarsi obliteration, spring ligament complex, tibiospring ligament integrity, as well as tibialis posterior tendon degeneration were evaluated with MRI. Statistical analysis was performed for significant (P <.05) correlation between findings. Results: None of the assessed 3D measurements correlated with either spring ligament complex or tibiospring ligament tears. BMI and TCO were found to be associated with tibialis posterior tendon tears. Seventy-five percent of patients with osseous sinus tarsi impingement on WBCT also showed signs of sinus tarsi obliteration on MRI. Conclusion: Although WBCT reflects foot alignment and can reveal osseous sinus tarsi impingement in PCFD patients, the association between WBCT-based 3D measurements and ligament or tendon tears assessed via MRI is limited. WBCT appears complimentary to MRI regarding its diagnostic value. Both imaging options add important information and may impact decision making in the treatment of PCFD patients. Level of Evidence: Level IV, observational study. [ABSTRACT FROM AUTHOR]

Category: Ankle; Ankle Arthritis; Hindfoot Introduction/Purpose: While correction of varus alignment at the level of the ankle joint has been investigated extensively after supramalleolar osteotomy (SMOT), the effect on the hindfoot alignment remains unclear. This can be attributed to the limitations of former 2-dimensional radiographic measurements used to quantify the complex 3-dimensional subtalar joint alignment. Therefore, we aimed to determine both the ankle and subtalar joint alignment before and after SMOT using a weightbearing CT and autogenerated 3-dimensional measurements. Methods: Twenty-seven patients with a mean age of 53 years (SD=10.1; range=25-73) were retrospectively analyzed in a pre- post study design using weightbearing CT images. Inclusion criteria were correction of ankle varus deformity by either an opening wedge (N=19) or dome osteotomy (N=8). Exclusion criteria consisted of an additional inframalleolar bony correction, i.e. calcaneal osteotomy or subtalar arthrodesis. Corresponding three-dimensional bone models were reconstructed to compute the autogenerated measurements: tibial anterior surface (TAS) -, tibiotalar surface (TTS)-, talar tilt (TT) - and talocalcaneal (TC) angle. Results: The pre-operative (TAS=86.9°, SD=4.9; TTS=79.8°, SD=5.6; TT=8.8°, SD=4.3) radiographic parameters of the ankle joint alignment improved significantly compared to the post-operative parameters (TAS=92.4°, SD=4.9; TTS=87.1°, SD=6.3; TT=5.1°, SD=2.7; P

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: Dome shaped supramalleolar osteotomies are a well-established treatment option for correcting ankle deformity. However, the procedure remains technically demanding and is limited by a two-dimensional (2-D) radiographic planning of a three-dimensional (3-D) deformity. Therefore, we implemented a weight-bearing CT-scan (WBCT) to plan a 3-D deformity correction using patient specific guides. Methods: A 3-D guided dome shaped supramalleolar osteotomy was performed to correct ankle varus deformity in a cohort of 5 patients with a mean age of 53,8 years (range: 47-58). WBCT images were obtained to generate 3-D models, which enabled a deformity correction using patient specific guides. These technical steps are outlined and associated with a retrospective analysis of the clinical outcome using the EFAS score, Foot and Ankle Outcome Score (FAOS) and Visual Analog Pain scale (VAS). Radiographic assessment was performed using the tibial anterior surface angle (TAS), tibiotalar angle (TTS), talar-tilt angle (TTA), hindfoot angle (HA), tibial lateral surface angle (TLS) and tibial rotation angle (TRA). Results: The mean follow-up was 40,8 months (range 8-65) and all patients showed improvements in the EFAS score, FAOS and VAS (p < 0.05). A 3-month postoperative WBCT confirmed healing of the osteotomy site and radiographic improvement of the TAS, TTS and HA (p0.05). Conclusion: Dome shaped supramalleolar osteotomies using 3-D printed guides designed on WBCT, are a valuable option in correcting ankle varus deformity and mitigates the technical drawbacks of free-hand osteotomies.

Category: Hindfoot; Midfoot/Forefoot; Other Introduction/Purpose: In progressive collapsing foot deformity (PCFD), hind- and midfoot deformities are paramount. However, an accurate assessment thereof, using weightbearing radiography, remains challenging. Automated three-dimensional (3D) measurements derived from weightbearing computed tomography (WBCT) scans may provide a more accurate approach for deformity assessment. In this study, automated 3D measurements based on WBCT were compared to two-dimensional (2D) measurements performed on weightbearing radiographs. Furthermore, it was investigated whether various stages of PCFD could be identified using automated 3D measurements. Methods: Twenty patients treated at our institution with either a flexible (N=10) or rigid (N=10) PCFD were identified, retrospectively analyzed and compared to a control group of thirty healthy individuals. Four angles and two distances measured on weightbearing radiographs were compared to the automated 3D measurements derived from WBCT scans. Results: In 5 out of 6 variables, the reliability of the measurements derived from weightbearing radiographs was lower than the automated measurements that derived from WBCT scans. The automated 3D measurements showed: the talar tilt in the ankle mortise was more valgus in patients with a rigid PCFD when compared to patients with a flexible PCFD; medial facet subluxation was present in all but one patient; patients with a sinus tarsi impingement evidenced a higher overlap between the talus and calcaneus (12.4+-2.6 mm) compared to patients without impingement (7.8+-3.9 mm; P=0.020). Conclusion: A higher reliability of automated 3D measurements derived from WBCT scans, was evident for most variables when compared to measurements based on weightbearing radiographs. Besides being less prone to errors, automated 3D measurements may provide more reliable information regarding the hind- and midfoot alignment in patients with PCFD. Future studies may show to what extent 3D measurements could contribute to current diagnostic algorithms and treatment concepts of patients with PCFD.

Background: A convincing association between the foot and ankle alignment (FAA) and patellofemoral pain syndrome (PFPS) remains debatable in the literature. Therefore, all studies investigating the role of FAA in patients with PFPS were systematically reviewed. Methods: A systematic literature search was performed on the databases PubMed, Embase, Cochrane Library, and Web of Science. Inclusion criteria were all studies investigating static and/or dynamic FAA factors and PFPS. Studies with less than 20 patients or with patellofemoral osteoarthritis were excluded. The quality assessment was based on Cochrane study criteria, and the maximum score was set at eight. Results: Of 2246 articles, only 13 case-control studies were eligible. Considering static FAA factors, two studies found an association with rearfoot eversion and one with rearfoot inversion. While examining dynamic FAA characteristics, one study found an association with rearfoot eversion range of motion and three with gait kinematics. No further associations were reported. The quality assessment mean score was 5.5 (SD = 0.97) corresponding to moderate quality. Conclusions: In contrast to our expectations, a limited number of studies were founded supporting an association between FAA and PFPS. At present, the quality of the literature is still poor and conflicting, thus the need for further studies to determine any association between FAA and PFPS.

Pro-inflammatory factors implicated for the onset of arthritis often have systematic effects, yet arthritis symptoms are mostly limited to the joints. Here the authors show that mechanical strain at the joints promotes the recruitment of monocyte and their differentiation into bone-eroding osteoclast to contribute this tissue specificity.

Category: Ankle Introduction/Purpose: Syndesmotic ankle injuries are challenging to diagnose, since current 2D imaging techniques try to quantify a 3D displacement. Therefore, our aim was two-fold: to determine displacement of sequential syndesmotic ankle injuries under various amounts of load using a 3D weightbearing CT (WBCT) and to assess the relation with current 2D imaging. Methods: Seven paired male cadaver specimens were included (tibia plateau to toe-tip) and mounted into a custom-built frame. WBCT scans were obtained after different patterns of load (0 kg or 85 kg) were combined with torque (0 Nm or 10 Nm external rotation). These conditions were repeated after each ligament condition: intact ligaments, sequential sectioning of the anterior inferior tibiofibular ligament (AITFL), deltoid ligament (DL), and interosseous membrane (IOM). CT images were segmented to obtain 3D models. These allowed quantification of displacement based on the position of computed anatomical landmarks in reference to the intact position of the fibula. A correlation analysis was performed between the 2D and 3D measurements. Results: The effect of torque caused significant displacements in all directions (P0.05). Weight caused a significant lateral (mean=-1.4 mm, SD=1.5) and posterior translation (mean=-0.6 mm, SD=1.8). The highest displacement consisted of external rotation (mean=-9.4°, SD=6.5) and posterior translation (mean=6.1 mm, SD=2.3) after IOL sectioning combined with torque (Fig. 1). Pearson correlation coefficients were moderate (range 0.31-0.51, P

Category: Hindfoot Introduction/Purpose: An adult-acquired flatfoot deformity is a three-dimensional (3D) condition characterized by a loss of the medial longitudinal arch, valgus alignment of the hindfoot, and abduction of the midfoot. When conservative measures are not sufficient, a medializing calcaneal osteotomy (MCO) is frequently performed to correct the deformity, but there is lack of data on the associated three-dimensional variables defining the final correction. A possible reason for this shortcoming could be the current image-based analyses, mainly performed on bi-dimensional radiographs. These are hampered by errors in 3D rotations and superimposition of bony structures. The aim of this study was therefore to assess the correlation between the preoperative hindfoot valgus deformity and calcaneal osteotomy angle and the postoperative calcaneal displacement by use of weightbearing CT (WBCT). Methods: Weight-bearing CT scans obtained pre- and post-operatively were analyzed for sixteen patients with a mean age of 49.4 years (range: 18-66 years). Indication for surgery was adult-acquired flat foot deformity stage II. Based on the WBCT images, pre- and post-operative 3D bone morphological models of the tibia, talus, calcaneus, and the second metatarsal were created, on which anatomical bony landmarks were computationally identified to define a Foot Anatomical reference Frame (FAF). This FAF was used to measure valgus deformity pre- and post-operatively, inclination of the osteotomy plane, and displacement of the calcaneus (Fig. 1). Linear regression was conducted to assess the relationship between these measurements. Results: On average, the hindfoot valgus changed from 13.1° (±4.6) preoperatively to 5.7° (±4.3) postoperatively. A mean inferior displacement of 3.2 mm (±1.3) was observed along the osteotomy with a mean inclination angle of 54.6° (±5.6), 80.5° (±10.7), - 13.7° (±15.7) in the axial, sagittal and coronal planes, respectively. A statistically significant positive relationship (P < .05, R2 = 0.6) was found between the preoperative valgus, the axial osteotomy inclination, and the inferior displacement. Conclusion: This study shows that the degree of preoperative valgus of the hindfoot and the axial osteotomy angle are predictive factors for the amount of postoperative plantar displacement of the calcaneus. These findings contrast the general recommendation of performing a 90° calcaneal osteotomy angle, i.e. perpendicular to the lateral calcaneal wall in every patient. The obtained factors should be taken into account when performing a MCO and could be integrated in a computer-based pre- operative planning.

Category: Hindfoot, Trauma Introduction/Purpose: Accurate assessment of subtalar joint stability is difficult. Weightbearing CT (WBCT) scans have increased in popularity among foot and ankle surgeons as it offers an accurate representation of hindfoot joint alignment under weightbearing conditions. However, the clinical utility of this imaging modality to diagnose subtalar joint instability has yet to be investigated. The purpose of this study was to assess the impact of load and torque application on the assessment of subtalar joint instability when using WBCT scans. We hypothesized that load and torque application would improve the ability to identify subtalar joint instability. Methods: Fourteen paired male cadavers (tibial plateau to toe-tip) were included. A radiolucent frame held specimens in a plantigrade position while non-weightbearing and weightbearing CT scans (with and without torque application) were taken. First, intact ankles (Native) were scanned. Second, one specimen from each pair underwent interosseous talo-calcaneal ligament (ITCL) transection (Condition 1A), while the contralateral underwent calcaneo-fibular ligament (CFL) transection (Condition 1B). Third, the lesions were reversed on the same specimens and the remaining intact ITCL or CFL was transected (Condition 2). Finally, the deltoid ligament was transected in all ankles (Condition 3). Two radiographic measurements were performed on the level of the ankle joint (talar tilt [TT], anterior talar translation [ATT]), while the subtalar tilt (STT) was measured at the anterior, middle, and posterior plane of the subtalar joint. Inter- and intra-observer agreement calculations were additionally performed. Results: Weight did not impact most measurements, while the majority of measurements differed significantly within each condition after torque application. Measurements performed at the level of the subtalar joint were more reliable and better predictors for subtalar joint instability compared to measurements performed at the level of the ankle joint. Discrete ITFL, combined ITFL/ CFL, and combined ITFL/ CFL/ deltoid ligament injuries had significantly different STT values than native ankles (Figure 1). Conclusion: Measurements to assess the stability of the subtalar joint should primarily be performed at the level of the subtalar joint rather than at the level of the ankle joint when using WBCT scans. Torque application is crucial for identifying subtalar joint instability, while the application of load should be avoided. Future clinical studies will therefore face substantial technical challenges should they attempt to determine the clinical utility of WBCT scans for assessment of subtalar joint instability.

Category: Hindfoot Introduction/Purpose: Patients with a hindfoot deformity pose a particular challenge when performing a total knee arthroplasty (TKA). This could be attributed to the lack of insights concerning hindfoot alignment outcome. Our objective was to perform a systematic review of the literature to investigate the influence of TKA on hindfoot alignment and vice-versa. Methods: This systematic review was performed in accordance to PRISMA guidelines; the original protocol is registered on PROSPERO (ID: 106980). The following electronic databases were searched to identify capable studies: Pubmed, EMBASE, Web of Science, Google Scholar, and Cochrane Library. To ensure the quality of the review, a quality assessment was performed according to the MINORS criteria. The mean MINORS score was 9.5 (range 7-12) and concurred with a good quality of the obtained studies. Results: Sixteen identified articles met the review criteria: six prospective cohort studies, nine retrospective studies, and one case-control study. Five articles reporting on clinical outcomes were identified; a pre-operative hindfoot deformity negatively influenced TKP outcome (N=4) or demonstrated no influence (N=1). Thirteen articles reporting on radiographic outcomes were identified. Five studies reported a significant improvement (P < 0.05) of hindfoot alignment after TKA, two studies demonstrated improvement limited to valgus hindfeet, seven studies observed a significant (P < 0.05) correlation between knee and hindfoot alignment, and two studies reported the association between hindfoot OA in patients undergoing TKA. Two studies reporting biomechanical outcomes were identified; these reported a shift of the weighbearing axis after TKA as a result of the remaining hindfoot deformity. Conclusion: TKA can improve the alignment of valgus hindfeet, but improvement was less pronounced in varus hindfeet. Furthermore, a worse clinical outcome is expected after TKA in patients with concomitant ankle OA. A remaining hindfoot deformity shifts the weightbearing axis, which could shorten the survival of the total knee prosthesis.

Category: Hindfoot Introduction/Purpose: The exact relationship between different types of hindfoot deformities and the full leg alignment is currently unclear. Therefore, our aim is to assess hindfoot alignment on a weight-bearing CT (WBCT) and its association with the full leg radiographic alignment. Methods: A retrospective analysis was performed on a study population of 109 patients (mean age of 53 years ± 14.49) with a varus or valgus hindfoot deformity and the presence or absence of ankle osteoarthritis (OA) based on the Takakura classification. The mechanical hindfoot - (mHA) and subtalar vertical angle (SVA) were determined on WBCT, while the mechanical tiba – (mTA) and mechanical tibiofemoral angle (mTFA) were measured on full leg radiographs. Results: In patients with ankle OA, a hindfoot valgus deformity was associated with a significantly higher mean varus alignment of the knee (mTFA = -1.8°±2.1; mTAx= -4.3°±1.9) compared to a valgus alignment of the knee (mTFA = 0.3°±2.6; mTAx= -1.4°±2.2; P 0.05). Conclusion: A valgus hindfoot deformity demonstrated a higher varus alignment of the knee when compared to patients with a hindfoot varus deformity, if ankle OA was present. The subtalar joint did not attain an overall compensatory correction towards the hindfoot deformity as opposed to a compensatory orientation of the tibia alignment. In clinical practice, these findings could improve the current understanding of both joint preserving as well as joint replacing procedures of the hindfoot and the knee.

Category: Radiolography Introduction/Purpose: Weight-bearing CT (WBCT) has been proven to allow for more precise and valid measurement of bone position than conventional weight-bearing radiographs (R) and conventional CT without weight-bearing (CT). Time spent for image acquisition has been shown to be lower for WBCT than for R and CT. Radiation dose for WBCT has been shown to be lower for WBCT than for CT. A WBCT device (PedCAT, Curvebeam, Warrington, PA, USA) had been brought on line July 1, 2013 in the first author´s foot and ankle department. The purpose of this study was to assess the benefit of using WBCT instead of R and/or CT in a foot and ankle center regarding time spent for image acquisition, radiation dose, disturbances, and cost effectiveness. Methods: All patients who obtained WBCT (PedCAT)from July 1, 2013 until September 30, 2018 were included in the study. Age, sex, primary pathology were analyzed. The time spent for image acquisition (T) was calculated based on an analysis of previous study as follows: R (bilateral feet dorsoplantar and lateral, metatarsal head skyline view), 902 seconds; CT (bilateral feet and ankle), 415 seconds; WBCT (bilateral), 207 seconds. Radiation dose (RD) per patient was calculated based on previous phantom measurements as follows: R, 1.4 uSv; CT, 25 uSv; WBCT 4.2 uSv1. For analysis cost effectiveness, device cost, reimbursement and working time cost of radiology technicians were taken into consideration within the local circumstances. All parameters were compared between the time period using WBCT (yearly average) with the parameters from 2012, i.e. before availability of WBCT. Results: 10,087 WBCT scans were obtained in 4,702 patients (4,702 (47%) before treatment; 5,385 (53%) follow-up; mean age, 52.0; 40% male). Primary pathologies were forefoot deformities (n=916 (20%) and ankle instability/cartilage defect (n=534 (13%)), and hindfoot deformity (n=480 (10%)). 1,940 WBCT scans were obtained on average yearly, and 10.4 CTs (WBCT group). In 2012, 1,850 R and 254 CTs were obtained (R(+CT) group). Yearly RD was 4.4 uSv for WBCT group and 4.8 uSv for R(+CT) group (difference 0.4 uSv decrease with WBCT 8%, p