Analysis of the Hindfoot Alignment Measured in 3D After a Medializing Calcaneal Osteotomy Using a Pre- and Postoperative Weightbearing CT

Category: Hindfoot Introduction/Purpose: An adult acquired flat foot (AAFD) is a complex 3D deformity. A medializing calcaneal osteotomy (MCO) is a surgical procedure frequently performed to correct the valgus alignment of the hindfoot in a stage II AAFD, when conservative measurements fail. However currently little is known on its accurate influence regarding the hindfoot alignment (HA). The aim is therefore to assess the influence of a MCO on the 3D HA using computer aided software analysis of the images retrieved from a weightbearing cone beam CT (WBCT). Methods: Twelve patients with a mean age of 49,4 years (range 18-67yrs) were prospectively included in a pre-post study design. Indications for surgical correction by a MCO with a solitary translation consisted of an AAFD stage II (N=10) and a posttraumatic valgus deformity (N=2). Fixation of the osteotomy was performed by a step-plate or double screw. WBCT was obtained pre- and post-operative. Images were subsequently segmented to allow a HA calculation in 3D(HA3D) by an angle between the anatomical tibia axis and the axis connecting the computed inferior calcaneuspoint and the centroid of the talus in the coronal plane based on a Cartesian coordinatesystem(Fig 1A, C). The tibia in the HA3D was separately assessed by the anatomical tibia axis (TAx 3D) and the axis to determine the tibial rotation(TR 3D) in the axial plane by connecting the computed most outer point of the anterior and posterior tubercle of the incisura fibularis(Fig 2A, D). Results: The mean medial translation of the calcaneal osteotomy during surgery was 5.72 mm (SD = 3.9). The mean HA3D pre-operatively equaled 18.21 degrees of valgus (SD = 6.6) and post-operatively 9.31 degrees of valgus (SD = 6.18). The Paired Student’s t-test showed a significant correction of 8.89 degrees (95%CI [5.99, 11.80], P<0.001). The mean TAX 3D pre-operatively was 6.80 degrees of valgus (SD = 3.38) and post-operatively 4.11 degrees of valgus (SD = 2.77), with a significant difference of 2.69 degrees (95%CI [1.79, 3.59], P <0.001). The mean TR3D pre-operatively was -27.11 degrees (SD = 4.77) and post-operatively - 28.80 degrees (SD = 5.98) and showed a significant difference of 1.69 degrees (95%CI [0.41, 2.97], P = 0,016). Conclusion: This study shows an effective correction of the valgus hindfoot in an AAFD. It appears that the correction is not only situated in the calcaneus but also to a lesser extent in the tibia and this resulted in 15% of the achieved HA correction. The novelty is the 3D weightbearing assessment of a hindfoot correction and the shown influence on the tibia. This information could be of use to take in to account when performing a pre-operative planning of a hindfoot deformity

Benefit of weight-bearing CT - what have we learned from more than 8,000 scans at a foot and ankle center

Category: Other 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 CT2. 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 July 1, 2013 until December 31, 2017 were included in the study. Age, sex and primary pathology were analyzed. The time spent for image acquisition (T) was calculated based on an analysis of a 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 uSv. For analysis of 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: 8,129 WBCT scans were obtained in 3,874 patients (3,874 (48%) preoperatively, 4,255 (52%) follow-up; mean age, 52.2; 39% male). Primary pathologies were forefoot deformities (n=728 (19%) and ankle osteoarthritis/cartilage defect (n=412 (11%)). 1,804 WBCT scans were obtained on average yearly, and 10 CTs (WBCT group). In 2012, 1,750 R and 250 CTs were obtained (R(+CT) group). Yearly RD was 4.3 uSv for WBCT group and 5.0 uSv for R(+CT) group (difference 0.6 uSv decrease with WBCT 13%, p<0.01). Yearly T was 105 hours in total (3.5 minutes per patient) for WBCT group and 961 hours in total (16.0 minutes per patient) for R(+CT) group (difference, 752.0 hours, decrease with WBCT, 78%, p<0.01). Yearly profit was 34,300 Euro for WBCT group, -846 Euro for R(+CT) group. Conclusion: 8,129 WBCT scans in 3,874 patients as substitution of R(+CT) over a 4.5 year period at a foot and ankle center resulted in 13% decreased RD (minus 0.7 uSV on average per patient). Yearly T decreased 752 hours (78%) in total (12.5 minutes per patient). Yearly financial profit increased 35,000 Euro in total (19 Euro per patient). RD decreased despite higher radiation dose for WBCT than for R alone, based on substitution of a high number of CTs by WBCT. Other centers with low usage of CT might not decrease RD by substituting R alone by WBCT

Application of External Torque Enhances the Detection of Subtle Syndesmotic Ankle Instability in a Weightbearing CT

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

A Case-control Study of 3D versus 2D Weight Bearing CT Measurements of the M1-M2 Intermetatarsal Angle in Hallux Valgus

Category: Midfoot/Forefoot Introduction/Purpose: Surgical planning based on angular measurements obtained on conventional radiographs is challenging due to perspective distortion and operator bias. Novel weightbearing CT (WBCT) three-dimensional (3D) measurements using coordinate systems may represent a more reliable and accurate evaluation of this 3D deformity. The objective of this study was to compare the M1-M2 intermetatarsal angle (IMA) obtained manually on WBCT digitally reconstructed 2D radiographs versus a set of coordinates from the full 3D dataset, in patients with hallux valgus (HV) deformity and in healthy controls. We hypothesised that the 3D measurements would be more reliably obtained, demonstrating different values when compared to 2D radiographic measurements. Methods: In this multicenter retrospective comparative study, 83 feet that underwent WBCT of the foot were included (41 HV: mean age 59, 81% female, 42 controls: mean age 52, 80% female). Datasets were analysed by three independent trained foot and ankle surgeons using the same protocol. Coordinates in three planes (x, y, z) of four different landmark points were harvested: center of the heads and midpoint of the proximal metaphysis of the 1st and 2nd metatarsal. The IMA measurements were then performed in reconstructed radiographic images (DRR-IMA). The data collected was then analyzed by a single 4th independent and blinded investigator who calculated the 3D angle (3D-IMA) and its projection on the weightbearing plane (2D-IMA). Intra-observer realiability was assessed by Pearson/Spearman’s correlation. Intermethod correlation was evaluated by intraclass correlation coefficient (ICC). Mean values for measures were comparared by One-way ANOVA. P-values of less than 0.05 were considered significant. Results: Intraobserver reliability was excellent for radiographic DRR-IMA (0.95) and 3D coordinates assessment (0.99). Intermethod correlation between the three different imaging modalities (DDR, 2D and 3D), considering bias and interactions, were respectively 0.71 and 0.51 in control and HV patients. IMA measurements were found to be similar when measured in DRR, 2D and 3D WBCT images, for both controls and HV patients. Mean values and confidence intervals (CI) for controls were 8.8 degrees (CI, 7.9-9.7) in DDR images, 9.8 degrees (CI, 8.7-10.9) in 2D images and 10.6 degrees (CI, 9.5-11.8) in 3D images. When compared to controls, HV patients demonstraded significantly increased IMA (p<0.05): 13.06 degrees (CI, 11.8-14.3) in DDR images, 12.1 degrees (CI, 10.8-13.3) in 2D images and 13.3 degrees (CI, 12.3-14.3) in 3D images. Conclusion: We found that similar values for IMA were measured in 2D reconstructed radiographs, WBCT 3D and 2D projected images. When compared to controls, HV patients were found to have increased IMA in all three different imaging types used (DDR, 2D and 3D). Intermethod correlation was higher for IMA performed in controls. Intraobserver reliability was excellent for both radiographic IMA measurements and WBCT 3D coordinates. Our study is the first study to evaluate measurements of the 3D-IMA in HV and control patients. Further investigations are required before guidelines for its clinical use can be formulated

Congruent Weber-B Ankle Fractures do not affect Tibiotalar Contact Mechanics: No Need for the Scalpel?

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

Effect of Dorsal Closing Wedge Calcaneal Osteotomy on Foot Alignment and Biomechanics in Patients with Insertional Achilles Tendinopathy

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

Should all Small Shell Posterior Malleolar Fractures be Considered for Fixation? Results from a 3D Fracture Mapping Study

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