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Category: Ankle; Trauma Introduction/Purpose: Chaput tubercle fractures, which are thought to represent tibial-sided avulsions of the anterior inferior tibiofibular ligament (AITFL), are prevalent in up to 30% of trimalleolar ankle fractures. The optimal treatment of small Chaput avulsions is debatable; direct fixation with suture anchor devices and indirect (syndesmotic) fixation are considered as viable options, with proponents on both sides. Moreover, recent literature highlights the potential anatomical alterations to the incisura tibialis resulting from malreduction of large Chaput fragments, furthering the case for direct fixation. Hence, we performed a CT- based three-dimensional fracture mapping study to identify the morphological characteristics of these fractures, and to determine whether they consistently involve the AITFL, tibial plafond and incisura tibialis. Methods: This study included adult patients who had an ankle fracture with a Chaput component; the scheme described by Rammelt et al. was used to classify these fractures. CT scans were obtained, and 3D models were generated. The models were superimposed over a statistical shape model of the right tibia which served as a template and fracture lines were marked. The footprints of proximal and main bands of the AITFL and Basset’s ligament were also marked on the template tibia. The tibial template along with the fracture lines was then imported into MATLAB, and an automated script was used to determine the fragment size (length, breadth, and height), fracture surface area, involvement of the tibial plafond, tibial incisura, and the anterior inferior tibiofibular ligament (AITFL) and Basset’s ligament. Fracture maps and heat maps were generated. Agglomerative cluster analysis using Ward’s linkage was used to identify discrete fracture categories. Results: 76 patients, 21 males and 55 females were included in this study. Cluster analysis identified two distinct groups of fractures, each with two unique subgroups. We present this as a modification of the existing classification system. The first group, corresponded to Rammelt Type 1 fractures (sub centimetric extra-articular avulsion fractures, n=47). Of these, 19% (n=9) did not involve the AITFL, which we termed as Type 1a, and 91% (n=48) involved the AITFL, which we termed as Type 1b. The second group consisted of large intra-articular fractures that corresponded to Rammelt Type 2 injuries. Of these 23% (n=6) involved only the incisura, which we termed as Type 2a; 77 % involved both the incisura and the tibial plafond and were termed as Type 2b. Conclusion: We propose a modification of the existing classification of Chaput fractures on the basis of quantitative fracture mapping. This study provides new insights into the morphological characteristics of Chaput fractures. 19% of small Chaput fractures do not involve the AITFL and may not require direct fixation. Conversely, all large-sized fragments involve the incisura and necessitate anatomical reduction to achieve accurate syndesmotic reduction. Our proposed modification can aid in surgical decision-making, particularly in choosing between direct and indirect syndesmotic fixation.

Category: Hindfoot; Other Introduction/Purpose: Plantar fasciitis (PF), a leading cause of persistent heel pain, results in almost a million physician visits annually. Conservative treatment is often the first line of management with insoles being frequently prescribed. While multiple studies have compared insoles based on the degree of customization to foot contour, the literature is lacking in data comparing insoles based on their material. In this randomized clinical trial, we compared the early effects of foam, polyurethane, and carbon fiber insoles in the treatment of PF, using a robust set of PROMS. Methods: A randomized clinical trial was designed at the foot and ankle research center of a tertiary care hospital in Massachusetts. Adult patients diagnosed with PF who had not received injectable or surgical treatment for it were included. Participants who consented were randomly allocated one of the three prefabricated insoles – carbon fiber insole (Group 1, n=13), polyurethane insole (Group 2, n=13), or foam insole (Group 3, n=9) for regular use. Their response was recorded using PROMIS 3a (for pain intensity), PROMIS 4a (for pain interference), FAOS (Foot and Ankle Outcome Score), and VAS for pain at baseline (T0), two (T2), six (T6) and twelve weeks (T12). A per-proto analysis was undertaken using Kruskal Wallis and Friedman tests. P< 0.05 was set as the level of significance. Results: Among groups 1, 2 and 3, the mean age of participants was 51.9±13.2, 51±12.5, and 47.9±13.5 years respectively and baseline weight varied as 211.6±32.7 lbs, 193.6±59.3 lbs, and 180.7±33 lbs respectively (p>0.05 for both). The group-wise distribution of participants based on sex and laterality of the affected foot showed no difference. Participants in each group reported similar intensity of the pain (VAS) at baseline and at all follow-up time points (p>0.05). A comparison of outcomes between baseline and subsequent timepoints showed significant improvement in quality of life (FAOS) at T12 (p=0.047) for carbon fibre insole users (Figure 1), significant pain relief on PROMIS Pain intensity and Pain Interference questionnaires for foam insoles at T3 and T12 (p=0.0003, 0.036 respectively). Conclusion: Carbon fiber insoles offered slightly better pain relief as early as six weeks into treatment and improved quality of life after twelve weeks of use. A possible link between the material of insole used and effective treatment of PF may exist. Conducting further analyses on the position of the foot during gait while using insoles and designing the insoles based on patient-specific criteria should be considered for future research.

Category: Ankle; Trauma Introduction/Purpose: The term ‘quadrimalleolar fracture’ (QMF) describes a trimalleolar (TM) ankle fracture with an associated Chaput or Wagstaffe fracture. Optimal fixation of these injuries not only allows for bone-to-bone healing but also facilitates syndesmotic reduction. However, this is a relatively new concept, and the literature on QMFs is limited to a few case series. Hence, we conducted this study to determine the epidemiology, patterns, and clinicoradiologic correlations of QMFs. The primary objective of this study was to describe the prevalence and patterns of QMFs. The secondary objective was to determine if certain clinical or radiological parameters were associated with different types and patterns of QMFs. Methods: A retrospective analysis of ankle fractures presenting to three tertiary referral hospitals was undertaken. Adult patients (≥18 years) presenting with an acute, traumatic TM ankle fracture over 3 years (July 2018 to July 2021) were included. Isolated medial and lateral malleolar fractures, bimalleolar ankle fractures, pediatric patients, pilon fractures, pathological fractures, and those with delayed presentation or (≥3 weeks of injury) were excluded. Clinical demographic variables were obtained from the patients’ medical records. AP, lateral, and mortise ankle radiographs, and CT scans, (axial, coronal, and sagittal sections along with 3D volume reconstructed models) whenever available, were evaluated in detail. Demographics and radiological parameters were compared between TM and QMF, as well as between different types of QMFs. Odds ratios with 95% confidence intervals were determined to test the strength of association. Results: A total of 876 adult patients with ankle fractures were included after the screening, of which 323 had a TM ankle fracture for which a CT scan had been performed. A total of 159 AITFL avulsions were identified, yielding a prevalence of 18.2% amongst all ankle fractures and 26.1% in ankle fractures where a CT scan had been performed. TMFs had the significantly highest proportion of CT-confirmed AITFL avulsions (44.4%) in comparison to unimalleolar (4.4%) and bimalleolar fractures (6.4%) (P < 0.0001). Age and osteoporosis were significant associations of QMFs. Avulsion of the medial malleolus, Weber B fibular fracture, and supination external rotation mechanism were significantly associated with Wagstaffe fractures. Size of the Chaput fracture was inversely related to that of the posterior malleolar fracture. Conclusion: Quadrimalleolar ankle fractures account for a significant proportion of ankle fractures. The strengths of this study include a large sample size, which was derived from three different hospitals, consecutive inclusion (or exclusion) of cases, strict adherence to the STROBE guidelines, and the fact that only CT-confirmed cases were used to determine clinic-radiological associations. Wagstaffe and Chaput fractures have distinct clinical and radiological correlations. However, further research is needed to determine the optimal fixation protocols for these injuries.

Category: Midfoot/Forefoot; Other Introduction/Purpose: Up to one-third of Lisfranc injuries are missed on initial evaluation, resulting in significant morbidity. Prompt diagnosis of Lisfranc injuries is, therefore, critical in optimizing outcomes, and yet there remains a lack of consensus on diagnostic criteria to identify Lisfranc instability using anatomic measurements. Prior studies have underscored the utility of weight-bearing computed tomography (WBCT) in diagnosing Lisfranc instability, which allows for bilateral three-dimensional (3D) evaluation under physiologic load. The aim of this study was to quantify appropriate cutoff values using 3D anatomic measurements of Lisfranc instability under physiologic load and as compared to the uninjured extremity. Methods: A total of 234 adult patients with bilateral WBCT scans of the foot were included: 43 patients with Lisfranc instability & 191 patients without a history of midfoot injuries. Lisfranc instability was confirmed intraoperatively or by clinical evaluation by the surgeon. Patients with prior midfoot surgery, Charcot arthropathy, severe midfoot arthropathy, or significantly displaced fracture of the cuneiforms or 1st, 2nd, or 3rd metatarsal bases were excluded. Lisfranc joint measurements were conducted bilaterally, including C1-M2 diastasis, C1-M2 area and 3D WBCT volume. Patient demographics were collected. Descriptive statistics were calculated for quantitative variables. Percent difference as compared to the contralateral side was calculated for volume, area, and diastasis. Mann Whitney U tests were utilized to determine differences in measurements between patients in the Lisfranc cohort and patients in the uninjured cohort (p-value < 0.05). Diagnostic cutoffs for Lisfranc instability were determined with minimum distance to the corner analysis on ROC curves. Results: The distribution of patients with Lisfranc instability was 58% female with an average age of 38.5±17.6 years. Of the Lisfranc injuries, 36% were purely ligamentous, 18% demonstrated an avulsion injury, and 43% involved a metatarsal base fracture. In the Lisfranc cohort, the median percent difference between injured and uninjured feet was 28.2% (IQR: 20.9%) for volume, 36.3% (IQR: 31.1%) for C1-M2 area, and 40.0% (IQR: 23.3%) for C1-M2 diastasis. Mann-Whitney testing was significant for percent difference between left and right feet for Lisfranc patients versus patients with an uninjured midfoot (p < 0.001). The area under the curve and associated diagnostic cutoffs for Lisfranc instability, were 0.81 and 18% for volume, 0.84 and 20% for area, and 0.91 and 28% for diastasis (Figure 1). Conclusion: Diastasis (1D), area (2D), and volume (3D) measurements are effective measurements to diagnose Lisfranc instability on WBCT. With current diagnostic algorithms, however, 1D measurements afford superior diagnostic sensitivity as compared to 2D and 3D measurements when using WBCT, suggesting Lisfranc instability may be best appreciated in the axial plane. Additional studies are necessary to expand the sample population to assess for corroboration with the current results, especially for subtle Lisfranc instability.

Category: Midfoot/Forefoot; Other Introduction/Purpose: Lisfranc instability is often a challenging injury to diagnose, with up to one-third being missed on initial evaluation. Lisfranc instability is assessed by widening of the space between the second metatarsal base and the medial cuneiform. This space is visualized on X-Ray; however, in subtle Lisfranc instability cases computed tomography (CT) imaging is often obtained. Given the 1D nature of diastasis measurement, X-ray should be an adequate means of evaluating this widening, yet clinical practice suggests weightbearing CT (WBCT) is more sensitive. This suggests the 3D location of the diastasis measurement is crucial. This study aimed to first compare weight-bearing X-ray and WBCT diastasis and area measurements of the Lisfranc complex, and second to compare WBCT diastasis measurements at various locations in the coronal plane. Methods: A total of 90 patients with both weight-bearing foot X-ray and bilateral foot WBCT were included: 37 patients had confirmed Lisfranc instability, and 53 patients had no history of midfoot injury. Lisfranc instability was confirmed intraoperatively or by clinical examination performed by the surgeon. For all 90 patients, the interosseous diastasis and area between the medial cortex of the second metatarsal and the lateral cortex of the medial cuneiform were measured on both weightbearing X-ray and axial slices of WBCT. For a subset of patients (12 in each cohort) the diastasis between second metatarsal and medial cuneiform was measured at 4 distinct axial locations using coronal slices of the WBCT (Figure 1). Results: A Wilcoxon test comparison of diastasis and area measurements on weightbearing X-ray and axial slices of WBCT revealed a significant difference in the weightbearing X-ray and WBCT measurements (p < 0.001) for both the control and Lisfranc cohorts. A comparison of weightbearing X-ray diastasis to dorsal, interosseous, and plantar diastasis measurements on coronal slices using Kruskal Willis analysis for the control cohort revealed a significant difference in all three measurements (Figure 1, p-values listed). Kruskal Willis analysis of the Lisfranc cohort demonstrated a significant difference between the X-ray diastasis and the plantar WBCT diastasis (p=0.01), but no difference from interosseous (p=0.08) or dorsal (p=0.33) diastases. A comparison of the axial WBCT diastasis measurements compared to the three coronal diastasis measurements revealed no difference in either cohort. Conclusion: Our results showed that for assessing the Lisfranc joint in subtle cases and healthy individuals, WBCT remains the most accurate imaging tool. However, in patients with confirmed Lisfranc instability, X-ray measurements are more reliable if the instability is at the dorsal and interosseous levels and not the plantar level. Hence, to assess the Lisfranc joint at different levels, WBCT has superiority over X-ray. Additionally, the axial diastasis of the Lisfranc joint on WBCT seems similar to coronal diastasis rendering both views reliable for measurements.

Category: Ankle; Other Introduction/Purpose: Geospatial access to healthcare is defined as the ability of patients to obtain healthcare services based on their locations. Therefore, we aimed to investigate patients’ proximity to healthcare and its correlation with the complications of surgically treated Achilles tendon rupture (ATR), including venous thromboembolism (VTE), re-rupture, and wound dehiscence. The outcome of this study can help providers and policy makers to determine the equity of healthcare for these patients in the area under their coverage. Methods: We included 426 patients who lived in the United States (US) tri-state area who received surgical treatment for ATR. We used patient and hospital addresses and zip codes to calculate the distances to healthcare centers. A geographic information system (GIS) platform analysis in the tri-state was completed using Maptive, powered by Google Maps, to create heat maps displaying the geographical distribution of patients treated for ATR with and without complications (Figure 1). The Shapiro–Wilk test was used to determine normal distribution. Mann–Whitney U test was used to compare the groups with and without complication. The point biserial correlation test was used to determine any correlations between driving distance and the incidence of complications (p < 0.05 was considered significant). Results: The average driving distance to the patient’s specific healthcare center was 62.16 ± 76.54 km. There was no significant difference between the distances for patients with and without overall complications (p = 0.65), with and without VTE (p = 0.70), with and without re-rupture (p = 0.84), and with and without wound problems (p = 0.36). No correlation between complications and the distance to healthcare centers was found (p = 0.65; Table 1). Conclusion: Geospatial information is important within the context of healthcare accessibility and can provide crucial guidance to healthcare planning for patients and healthcare policymakers. Although this study showed that distance to healthcare facilities did not lead to significantly higher complication rates amongst ATR patients, it does not resolve the need for further studies looking at a larger population and broader geographical segments. These studies can be used to assess the equity of healthcare in specific areas and make modifications if needed.

Category: Midfoot/Forefoot; Midfoot/Forefoot Introduction/Purpose: Lisfranc injury consists of a spectrum of injuries affecting the tarsometatarsal joint. Various fixation methods are used to treat Lisfranc injuries and each show different outcomes. Metal implants have been used for open reduction and internal fixation (ORIF) of Lisfranc injuries routinely. However, other than the complications in these patients, such as non- anatomical reduction, implant loosening, breakage, and arthrosis, most of these patients will undergo a second surgery for implant removal. Using bio-degradable and bio-integrative materials in these implants reduces the need for these re-operations; however, whether other complications reported for metal implants occur by using bio-integrative materials has yet to be proven. The aim of our study is to assess patient-reported outcome measures (PROMs) and complications in patients received bio-integrative screws for Lisfranc fixation. Methods: The inclusion criteria were 1) ≥ 18 years old, and 2) had ORIF for Lisfranc injury using bio-integrative (OSSIOfiber ™) screws. The patients’ charts were reviewed, and the variables were gathered, including the type of injury, pain score, and PROMs. The questionnaires used to evaluate PROMs were Patient-Reported Outcome Measurement Information System (PROMIS) surveys for physical function, pain interference, pain intensity, and depression. We also reported the average scores for these PROMs among a randomly sampled population of patients who had ORIF with metal screws for Lisfranc injuries for comparison (n=12). Results: We recruited 12 patients for this study. The minimum follow-up time of the patients in this study was three months. Out of 12 patients, 1 patient showed non-union. The mean (SD) PROMIS scores for physical function, pain interference, pain intensity, and depression were 43.9 (14.9), 56.1 (13.9), 45.9 (10.1), and 43.5 (4.9) in patients who received bio-integrative screws, respectively. In the sampled population treated with metal screws, these PROMs were 42.1 (9.5), 55 (10.1), 46.4 (8.1), and 44.4 (6.4) for physical function, pain interference, pain intensity, and depression, respectively. No significant difference was observed between the two groups regarding physical function (P=0.72), pain interference (P0.82), pain intensity (P=0.88), and depression (P=0.69). Conclusion: The current report showed promising patient-reported outcomes after Lisfranc ORIF with bio-integrative screws. However, longer term follow-ups, as well as comparison with a larger population for both types of instruments, bio-integrative and metal, will shed light on the pros and cons of both materials. Moreover, cost-effective studies are highly suggested to assess the usefulness of these implants against their costs for the healthcare system and the patients.

Category: Sports; Ankle Introduction/Purpose: Acute Achilles tendon ruptures (ATRs) can be treated surgically through either open repair or minimally invasive surgical techniques (MIS). While the relative complication rates between these techniques, including wound dehiscence, re-rupture, and sural nerve injury, have been debated, many studies demonstrate no significant difference between these two approaches. In this study, we conducted a Kaplan-Meier survival analysis to compare the incidence and timing of complications between open and MIS repair of acute ATRs and examine factors that may influence these rates. Methods: A retrospective study was conducted to evaluate the outcomes of patients (≥18 years) who underwent surgical intervention for acute ATR within a four-week period following injury, with a minimum follow-up of three months. Data on demographic variables, type of surgical procedure (MIS or open approach), and the occurrence and timing of postoperative complications were collected. Postoperative complications were classified as venous thromboembolism (VTE), re-rupture, surgical site infecti+D2on (SSI), wound dehiscence, and sural nerve injury.The Kaplan-Meier method was employed to compare the complication rates between the MIS and open repair groups. The log-rank test was used to test the equality of survivor functions. The Cox proportional hazards model was employed to determine predictors of complications. Results: In total, 417 patients were included in the final analysis. The MIS group had a higher proportion of patients with tobacco use. Fifty-two complications in 50 patients were recorded (Table 1). We found no significant difference in the complication rates between the MIS and open repair groups. However, Cox proportional hazards modeling revealed that body mass index (BMI) was a significant predictor of re-ruptures (HR 1.2, 95% CI = 1.05–1.4) and that surgical delay was found to be a significant predictor of wound dehiscence (HR 1.2, 95% CI =1.01–1.3) and sural nerve injury (HR 1.2, 95% CI =1.1–1.3). A surgical delay of more than 2 weeks was noted to have a positive likelihood ratio of 2.3 for wound dehiscence and 3.1 for sural nerve injury. Conclusion: The results of this study indicate that MIS and open repair techniques for acute ATRs demonstrate comparable complication rates. However, patients with elevated BMI exhibit an increased risk of re-rupture. Those with surgical delay beyond two weeks have an elevated likelihood of wound dehiscence and sural nerve injury, presumptively due to associated scaring and the requisite tissue manipulation. Surgeons and patients may consider these variables when formulating a surgical treatment plan.

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: Ankle; Other Introduction/Purpose: Anatomical reduction of the distal syndesmosis can be challenging. There is ongoing debate and variability in the methods used for evaluating the accuracy of reduction, including radiography, intra-operative CT, arthroscopy, and direct visualization. Tornetta et al. have described a method called ‘the articular surface method’ that evaluates the relationship between the articular cartilage of the distal anteromedial fibula and the anterolateral tibia as being significantly more accurate for detecting malreduction. However, it entails an additional surgical incision over the distal aspect of the ankle. The aim of this study was to find a non-invasive method using ultrasound to assess the accuracy of reduction in syndesmotic injuries. Methods: A cadaveric syndesmotic instability model was created by dissecting the PITFL, IOL, and AITFL through a small posterior incision. The fibula was fixed in incremental degrees of rotational malreduction to achieve a malreduction of 3, 5, and 7 mm. A blinded observer assessed the syndesmosis using a portable ultrasound device. The probe was placed in its short axis at the level of the ankle joint then moved proximally until both the anteromedial fibular and anterolateral tibial articular surfaces were visualized simultaneously in one view. In a reduced syndesmosis, the distal articular surfaces of the tibia and fibula overlap. This relationship is altered in a malreduced syndesmosis, which allows ultrasonographic waves to ‘penetrate’ through the malreduced articular surfaces and be readily detected. This sign was graded positive if an acoustic signal penetrated between the distal articular surfaces of the tibia and fibula, and negative if no acoustic signal was detected. Results: The gap penetrance sign was positive in all 3 instances of malreduced syndesmoses, and negative in an anatomically reduced syndesmosis. Figure 1 illustrates the outcomes in a reduced syndesmosis and malreduced syndesmosis, respectively. Conclusion: We introduced a novel sign that can be used as a surrogate of the ‘articular surface method’ to detect syndesmotic malreduction. It is accurate, can obviate the need for a separate surgical incision for direct visualization, permits rapid point-of- care evaluation in the operating room, and minimizes radiation exposure

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.