Fast digitally reconstructed radiograph generation using particle-based statistical shape and intensity model.

Purpose: Statistical shape and intensity models (SSIMs) and digitally reconstructed radiographs (DRRs) were introduced for non-rigid 2D-3D registration and skeletal geometry/density reconstruction studies. The computation of DRRs takes most of the time during registration or reconstruction. The goal of this study is to propose a particle-based method for composing an SSIM and a DRR image generation scheme and analyze the quality of the images compared with previous DRR generation methods. Approach: Particle-based SSIMs consist of densely scattered particles on the surface and inside of an object, with each particle having an intensity value. Generating the DRR resembles ray tracing, which counts the particles that are binned with each ray and calculates the radiation attenuation. The distance between adjacent particles was considered to be the radiologic path during attenuation integration, and the mean linear attenuation coefficient of the two particles was multiplied. The proposed method was compared with the DRR of CT projection. The mean squared error and peak signal-to-noise ratio (PSNR) were calculated between the DRR images from the proposed method and those of existing methods of projecting tetrahedral-based SSIMs or computed tomography (CT) images to verify the accuracy of the proposed scheme. Results: The suggested method was about 600 times faster than the tetrahedral-based SSIM without using the hardware acceleration technique. The PSNR was 37.59 dB, and the root mean squared error of the normalized pixel intensities was 0.0136. Conclusions: The proposed SSIM and DRR generation procedure showed high temporal performance while maintaining image quality, and particle-based SSIM is a feasible form for representing a 3D volume and generating the DRR images.

Postoperative Stability in Displaced Ankle Fractures With Concomitant Ligamentous Injuries.

Ankle instability, which can be attributed to either the deltoid or lateral ligamentous complex, may be both a cause and a consequence of ankle fractures. This study aimed to assess postoperative ankle instability in patients with displaced ankle fractures. A total of 54 patients with displaced ankle fractures were included. Malleolar fractures were surgically reduced and fixated, and if necessary, the syndesmosis was stabilized. Concomitant deltoid injuries were left unrepaired. Ankle stress radiographs were taken approximately 25.4 months after surgery, with a standard deviation of 20.5 months. Radiographic measurements included the tibiotalar tilt angle (TT) on varus stress view, anterior translation of the talus (AT) on the anterior drawer view, and the medial clear space (MC) and tibiotalar tilt angle on the valgus stress view. These measurements were compared between the injured and the noninjured contralateral ankle for all patients as well as in a subgroup of 19 patients with concomitant deltoid and syndesmosis injuries. There were no significant differences in Varus TT (p = .675, p = .394), AT (p = .516, p = .967), Valgus MC (p = .190, p = 0.498), and Valgus TT (p = .173, p = .442) between the injured and noninjured ankles in the whole group of patients as well as in the subgroup of patients with concomitant deltoid and syndesmosis injuries. Patients with displaced ankle fractures exhibited radiographically stable ankles postoperatively. Syndesmosis fixation without deltoid ligament repair is a viable treatment option for achieving ankle stability postoperatively in fractures with both ligament injuries.

Hindfoot joint kinematics analysis after the resection of talocalcaneal coalition.

BACKGROUND: The subtalar joint movement between the talus and calcaneus is restricted in patients with talocalcaneal coalition (TCC). When the motion of the subtalar joint is restricted, shock absorption in the foot decreases, leading to pain during walking. Resection methods to maintain subtalar motion by removing abnormal unions have been proposed. The purpose of this study was to analyze the joint kinematics of patients who underwent TCC resection and to quantitatively evaluate the results of the surgery based on the measured kinematics. METHODS: Joint kinematics of five patients with TCC were obtained using a biplane fluoroscopic imaging system and an intensity-based two-/three-dimensional registration method. The joint kinematics of the tibiotalar and subtalar joints and the tibiocalcaneal motion during the stance phase of walking were obtained. From the kinematics of the hindfoot joints, the inversion/eversion range of motion (ROM) of the patients before and after resection was statistically analyzed using the Wilcoxon signed-rank test to test whether TCC resection improved the ROM. RESULTS: During the loading response period, the eversion ROM of the subtalar joint and tibiocalcaneal motion significantly increased postoperatively. In addition, a significant postoperative increase was observed in the subtalar and tibiocalcaneal inversion ROM during the pre-swing period. SIGNIFICANCE: TCC resection surgery increased the ROM of the subtalar joint, which in turn contributed to the increase in tibiocalcaneal ROM. Increased subtalar and tibiocalcaneal ROM could result in increased shock attenuation and may be a contributing factor to pain relief during walking.

Dynamic Foot Pressure During Walking: A Potential Indicator of Bone Mineral Density.

BACKGROUND: Physical skeletal loading can affect the bone mineral density (BMD). This study investigated the association between BMD and dynamic foot pressure during gait. METHODS: A total of 104 patients (mean age, 62.6 ± 12.4 years; 23 male and 81 female) who underwent dual x-ray absorptiometry and pedobarography were included. BMD values of the lumbar spine, femoral neck, and total femur were assessed. The mean and maximum pressures were measured at the hallux, lesser toes, 1st metatarsal head, 2nd and 3rd metatarsal heads, 4th and 5th metatarsal heads, midfoot, medial heel, and lateral heel. Multivariable regression analysis was performed to identify factors significantly associated with BMD. RESULTS: The lumbar spine BMD was significantly associated with the mean pressure at the 4th and 5th metatarsal heads (p = 0.041, adjusted R 2 of model = 0.081). The femoral neck BMD was significantly associated with the maximum pressure at the 2nd and 3rd metatarsal heads (p = 0.002, adjusted R 2 = 0.213). The total femoral BMD also showed a significant association with the maximum pressure at the 2nd and 3rd metatarsal heads (p = 0.003, adjusted R 2 = 0.360). CONCLUSIONS: Foot plantar pressure during gait was significantly associated with BMD, and could potentially be used to predict the presence of osteoporosis. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Higher coactivations of lower limb muscles increase stability during walking on slippery ground in forward dynamics musculoskeletal simulation.

The energy efficiency theory of human bipedal locomotion has been widely accepted as a neuro-musculoskeletal control method. However, coactivation of agonist and antagonist muscles in the lower limb has been observed during various limb movements, including walking. The emergence of this coactivation cannot be explained solely by the energy efficiency theory and remains a subject of debate. To shed light on this, we investigated the role of muscle coactivations in walking stability using a forward dynamics musculoskeletal simulation combined with neural-network-based gait controllers. Our study revealed that a gait controller with minimal muscle activations had a high probability of falls under challenging gait conditions such as slippery ground and uneven terrain. Lower limb muscle coactivations emerged in the process of gait controller training on slippery ground. Controllers with physiological coactivation levels demonstrated a significantly reduced probability of falls. Our results suggest that achieving stable walking requires muscle coactivations beyond the minimal level of muscle energy. This study implies that coactivations likely emerge to maintain gait stability under challenging conditions, and both coactivation and energy optimization of lower limb muscles should be considered when exploring the foundational control mechanisms of human walking.

Effect of flatfoot correction on the ankle joint following lateral column lengthening: A radiographic evaluation.

OBJECTIVES: The effects of foot deformities and corrections on the ankle joint without osteoarthritis has received little attention. This study aimed to investigate the effect of flatfoot correction on the ankle joint of patients without osteoarthritis. METHODS: Thirty-five patients (24 men and 11 women; mean age 17.5 years) who underwent lateral column lengthening for flatfoot deformities were included. The mean postoperative follow-up period was 20.5 months (standard deviation [SD]: 15.7 months). Radiographic indices were measured pre- and postoperatively, including anteroposterior (AP) and lateral talo-first metatarsal angles, naviculocuboid overlap, position of the articulating talar surface, and lateral talar center migration. Postoperative changes in the radiographic indices were statistically analyzed. RESULTS: There was significant postoperative improvement in flatfoot deformity in terms of AP and lateral talo-first metatarsal angles (p<0.001 and p<0.001, respectively) and naviculocuboid overlap (p<0.001). On lateral radiographs, the talar articulating surface dorsiflexed by 7.3% (p<0.001), and the center of the talar body shifted anteriorly by 0.85 mm (p<0.001) postoperatively. CONCLUSIONS: Flatfoot correction using lateral column and Achilles tendon lengthening caused dorsiflexion and an anterior shift of the articular talar body in patients without osteoarthritis. Correction of flatfoot deformity might affect the articular contact area at the ankle joint. The biomechanical effects of this change need to be investigated further.

Greater Knee Rotatory Instability After Posterior Meniscocapsular Injury Versus Anterolateral Ligament Injury: A Proposed Mechanism of High-Grade Pivot Shift.

Background: For anterolateral rotatory instability as a result of secondary soft tissue injuries in anterior cruciate ligament (ACL)-deficient knees, there is increasing interest in secondary stabilizers to prevent internal rotation (IR) of the tibia. Purpose: To determine which secondary stabilizer is more important in anterolateral rotatory instability in ACL-deficient knees. Study Design: Controlled laboratory study. Methods: The lower extremities of 10 fresh-frozen cadavers (20 extremities) without anterior-posterior or rotational instability were included. Matched-pair randomization was performed, with each side per specimen assigned to 1 of 2 groups. In group 1, the ACL was sectioned, followed by the anterolateral ligament (ALL); in group 2, the ACL was sectioned, followed by sequential sectioning of the posterolateral meniscocapsular complex (PLMCC) and posteromedial meniscocapsular complex (PMMCC). The primary outcome was the change in relative tibial IR during a simulated pivot-shift test with 5 N·m of IR torque and 8.9 N of valgus force. The secondary outcomes were the International Knee Documentation Committee grade in the pivot-shift test and the incidence of the grade 3 pivot shift. Results: In group 1, compared with baseline, the change in relative tibial IR at 0° of knee flexion was 1.4° (95% CI, -0.1° to 2.9°; P = .052) after ALL release. In group 2, it was 2.5° (95% CI, 0.4° to 4.8°; P = .007) after PLMCC release and 4.1° (95% CI, 0.5° to 7.8°; P = .017) after combined PLMCC and PMMCC release. Combined PLMCC and PMMCC release resulted in greater change of tibial IR with statistical significance at 0°, 15°, and 30° of knee flexion (P = .008, .057, and .004, respectively) compared with ALL release. The incidence of grade 3 pivot shifts was 10% in group 1 and 90% in group 2. Conclusion: Posterior meniscocapsular laxity caused an increase in relative tibial IR as much as ALL injury in ACL-deficient knees in our simulated laboratory test, and greater anterolateral rotatory instability occurred with posterior meniscocapsular injury compared with ALL injury. Clinical Relevance: Repair of the injured posterior meniscocapsular complex may be an important treatment option for reducing anterolateral rotatory instability in the ACL-deficient knee.

Increase in lateral contact force in the tibiotalar joint during walking in flatfoot patients with reduced stiffness of the spring ligament.

Foot deformities in patients with flexible flatfeet, such as the flattened medial arch and hindfoot valgus, affect the force distribution around the tibiotalar joint during walking and increase the risk of secondary injuries. In this study, we developed a multi-segment foot model that could calculate the dynamics around the tibiotalar joint and investigated the difference in the kinetics between normal feet and feet with flatfoot. Ten participants with normal feet and ten with flexible flatfoot were enrolled in the study. The body kinematics, ground reaction force, and foot pressure of the participants were recorded during walking. A five-segment foot model was developed to calculate contact forces in the tibiotalar joint. A flatfoot model was developed by modifying the stiffness of the spring ligaments of a normal foot model. Ground reaction force was applied to the plantar surface of the foot models. The foot models were attached to a full-body musculoskeletal model to conduct inverse dynamic simulations of walking. Participants with flatfoot had significantly greater lateral contact force (1.19 BW vs. 0.80 BW) and more posteriorly located center of pressure (33.7 % vs. 46.6 %) in the tibiotalar joint than those with normal feet (p < 0.05). The average and peak posterior tibialis muscle forces were significantly larger in participants with flatfoot than in those with normal feet (3.06 BW vs. 2.22 BW; 4.52 BW vs. 3.33 BW). The altered mechanics may influence the risk of arthritis.

Radiographic Measurements Associated With Ankle Power Generation During Gait in Patients With Cerebral Palsy.

BACKGROUND: Pes planovalgus (PV) deformity accounts for lever arm dysfunction and compromises gait in patients with cerebral palsy (CP). However, the association between ankle power generation and radiographic indices is not yet understood. We aimed to investigate the association between ankle power and radiographic indices during gait in patients with CP concomitant with PV deformity. METHODS: Patients older than 14 years with ambulatory CP and PV deformity were included. All the patients underwent 3-dimensional gait analysis and weight-bearing foot radiography. Gait data were collected, including foot progression angle, tibial rotation, hip rotation, and ankle power generation. Radiographic measurements included anteroposterior (AP) talo-first metatarsal angle, lateral talo-first metatarsal angle, and hindfoot angle. A linear mixed-effects model was performed to identify significant radiographic indices associated with ankle power generation. RESULTS: Thirty-one limbs from 15 patients with spastic diplegia and 6 with spastic hemiplegia were included. Statistical analysis demonstrated that ankle power generation was significantly correlated with the CP type ( P =0.0068) and AP talo-1 st metatarsal angle ( P =0.0230). CONCLUSION: Ankle power generation was significantly associated with the AP talo-first metatarsal angle. Surgeons might need to pay attention to correcting forefoot abduction to restore ankle power when planning surgeries for pes PV deformities in patients with CP. LEVEL OF EVIDENCE: Prognostic Level III.

Influences of Partial Anterior Cruciate Ligament Injury on Anterior Cruciate Ligament Tensional Force and Kinematic Stability During Walking.

Injuries in the anterior cruciate ligament (ACL), including partial tear and lengthening of the ACL, change the dynamic function of the knee. However, there is a lack of information on the effect of ACL partial tear on knee kinematics during walking. This study aimed to investigate the effects of different levels of ACL injuries on knee stability and ACL tensional force to identify the critical injury level. Motion data of five normal subjects were acquired along with the ground reaction force. A knee model with 14 ligaments was developed using cadaveric specimen data. The initial length and stiffness of the ACL were changed to develop ACL-injured knee models. Musculoskeletal simulations of the knee models were performed using the measured gait data. The average tibial anterior translation increased significantly by 2.6 ± 0.7 mm when the ACL stiffness decreased to 25% of its original stiffness. The average tibial anterior translation increased significantly by 2.6 ± 0.3 mm at an increase in initial length of 10%. The knee with partial ACL tear had a nonlinear decrease in ACL forces owing to the increase in the level of ACL injury, while the knee with ACL lengthening had linear decreased ACL forces. The partial tear of the ACL caused translational instability, while the complete tear caused both rotational and translational instabilities during the musculoskeletal walking simulation. This study presents the effects of partial ACL injuries on joint kinematics and ACL tensional force during the dynamic motion of walking.

Physical factors that differentiate body kinematics between treadmill and overground walking.

Treadmills are widely used in rehabilitation and gait analysis. However, previous studies have reported differences in terms of kinematics and kinetics between treadmill and overground walking due to physical and psychological factors. The aim of this study was to analyze gait differences due to only the physical factors of treadmill walking. Walking motions of a male participant were captured at 0.63, 1.05, 1.33, and 3.91 m/s. A gait controller of a virtual subject (63 kg) was trained for ground walking at each walking speed via a reinforcement learning method. Additionally, the gait controllers of virtual subjects with different body masses of 47, 79, and 94 kg were trained for ground walking at 1.05 m/s. The gait controllers and virtual subjects were tested for treadmill walking, and their lower-limb joint kinematics were compared with those for ground walking. Treadmill conditions of maximum allowable belt force and feedback control frequency of belt speed were set between 100 and 500 N and between 10 and 50 Hz, respectively. The lower-limb kinematics were identical between the two conditions regardless of the body mass and walking speed when the belt could provide a constant speed regardless of external perturbation in the ideal treadmill. However, kinematic differences were observed when simulation was performed on a non-ideal treadmill with a relatively low belt force and control frequency of belt speed. The root-mean-square differences of the hip, knee, and ankle flexion angles between treadmill and overground running at 3.91 m/s increased by 3.76°, 3.73°, and 4.91°, respectively, when the maximum belt force and control frequency decreased from infinity to 100 N and 10 Hz, respectively. At a maximum belt force exceeding 400 N or a control frequency exceeding 25 Hz, the root-mean-square difference of the joint kinematics was less than 3° for all body masses and walking speeds. Virtual subjects walking on non-ideal treadmills showed different joint kinematics from ground walking. The study identified physical factors that differentiate treadmill walking from overground walking, and suggested the belt forces and control frequencies of a treadmill to achieve the desired limit of kinematic differences.

Anomalous Gait Feature Classification From 3-D Motion Capture Data.

The gait kinematics of an individual is affected by various factors, including age, anthropometry, gender, and disease. Detecting anomalous gait features aids in the diagnosis and treatment of gait-related diseases. The objective of this study was to develop a machine learning method for automatically classifying five anomalous gait features, i.e., toe-out, genu varum, pes planus, hindfoot valgus, and forward head posture features, from three-dimensional data on gait kinematics. Gait data and gait feature labels of 488 subjects were acquired. The orientations of the human body segments during a gait cycle were mapped to a low-dimensional latent gait vector using a variational autoencoder. A two-layer neural network was trained to classify five gait features using logistic regression and calculate an anomalous gait feature vector (AGFV). The proposed network showed balanced accuracies of 82.8% for a toe-out, 85.9% for hindfoot valgus, 80.2% for pes planus, 73.2% for genu varum, and 92.9% for forward head posture when the AGFV was rounded to the nearest zero or 1. Multiple anomalous gait features were detectable using the proposed method, which has a practical advantage over current gait indices, including the gait deviation index with a single value. The overall results confirmed the feasibility of using the proposed method for screening subjects with anomalous gait features using three-dimensional motion capture data.

Intrasubject Radiographic Progression of Hallux Valgus Deformity in Patients With and Without Metatarsus Adductus: Bilateral Asymmetric Hallux Valgus Deformity.

This study was to analyze intrasubject radiographic progression of the hallux valgus deformity by comparing the mildly and severely affected sides in patients with bilateral asymmetric hallux valgus in the whole group as well as the metatarsus adductus and the nonmetatarsus adductus subgroups. A total of 186 patients with bilateral asymmetrical hallux valgus deformity with a difference of 5° or greater in the hallux valgus angle were included, and 11 radiographic measurements were analyzed. The radiographic differences between the mildly and severely affected sides were compared. Correlation between the changes in the hallux valgus angle and those in other measurements was analyzed, and multiple regression analyses were performed. The anteroposterior talo-second metatarsal angle showed no significant difference between the mildly and severely affected sides. Changes in the intermetatarsal angle and sesamoid rotation angle were significantly associated with the progression of hallux valgus angle in the whole group as well as the nonmetatarsus adductus subgroup. Change in the intermetatarsal angle (p = .006) was the significant factor associated with the progression of hallux valgus angle in the metatarsus adductus subgroup. The anteroposterior talo-second metatarsal angle might be useful in evaluating the overall foot shape in the hallux valgus deformity. Progression of the hallux valgus deformity might be pathophysiologically different between those with and without metatarsus adductus.

Relationship between radiographic measurements and knee adduction moment using 3D gait analysis.

BACKGROUND: Radiographic factors estimate the state of the static knee joint, and it is questionable how well these parameters reflect the dynamic knee condition. The external knee adduction moment (KAM) during gait is known to be a kinetic variable contributing to osteoarthritis progression. This study aims to investigate the effects of static radiographic parameters on the dynamic KAM during gait. METHODS: Overall, 123 patients (mean age, 65.7 years; standard deviation, 8.1 years; 34 men and 89 women) were included. Seven radiographic parameters including the mechanical tibiofemoral angle (mTFA), Kellgren-Lawrence grade, and ankle joint line orientation (AJLO) were measured on radiographs, and the maximum KAM and KAM-time integral in the stance phase were obtained using three-dimensional gait analysis. The correlation and multiple regression analyses were performed for identifying significant radiographic measurements associated with the KAM. RESULTS: Most of the radiographic measurements correlated with the maximum KAM and KAM-time integral. As a result of multiple regression analysis, the mTFA (p < 0.001) and AJLO (p = 0.003) were identified as significant factors associated with the KAM-time integral (R2 = 0.450); the mTFA (p < 0.001) and AJLO (p = 0.003) were identified as a significant factor associated with the maximum KAM (R2 = 0.352) in multiple regression analysis. The discriminant validity of KAM was highest at varus 5.7 degree of the mTFA and 7.5 degree of the AJLO. SIGNIFICANCE: The mTFA and AJLO were significantly associated with the KAM. However, to be used as a surgical indication for corrective osteotomy, a longitudinal study is needed to validate whether the mTFA and AJLO values directly cause osteoarthritis progression as we have suggested. LEVEL OF EVIDENCE: III.

Kinematic instability in the joints of flatfoot subjects during walking: A biplanar fluoroscopic study.

Abnormal foot kinematics is observed in flatfoot subjects with postural foot deformity. We aimed to investigate joint instability in flatfoot subjects by analyzing the abnormal rotational position and speed of their joints while walking. Five flatfoot subjects participated in our study. Three-dimensional motions of the tibia, talus, calcaneus, navicular, and cuboid were obtained during walking using the biplanar fluoroscopic motion analyses. An anatomical coordinate system was established for each bone. The rotations and ranges of motion (ROMs) of the joints from heel-strike to toe-off were quantified. The relative movements on the articular surfaces were quantified by surface relative velocity vector analysis. The data from flat foot subjects were compared with the data from normal foot subjects in previous studies. The average relative speed on the articular surface of the tibiotalar, subtalar, and calcaneocuboid joints for the flatfoot subjects was significantly higher (p < 0.05) than that for the normal foot subjects. The flatfoot subjects exhibited increased movements toward plantar flexion in the tibiotalar joint, and eversion and external rotations in the talonavicular joint during the stance phase, compared to the normal subjects (p < 0.01). Furthermore, the flatfoot subjects had a significantly larger ROM along with the inversion/eversion rotations (5.6 ± 1.8° vs. 10.7 ± 4.0°) and internal/external rotations (7.1 ± 1.5° vs. 10.5 ± 3.5°) in the tibiotalar joint. The flatfoot subjects demonstrated abnormal kinematics and larger joint movements in multiple joints during the mid-stance and terminal stance phases of walking. This demonstrates their high instability levels.

Uniqueness of gait kinematics in a cohort study.

Gait, the style of human walking, has been studied as a behavioral characteristic of an individual. Several studies have utilized gait to identify individuals with the aid of machine learning and computer vision techniques. However, there is a lack of studies on the nature of gait, such as the identification power or the uniqueness. This study aims to quantify the uniqueness of gait in a cohort. Three-dimensional full-body joint kinematics were obtained during normal walking trials from 488 subjects using a motion capture system. The joint angles of the gait cycle were converted into gait vectors. Four gait vectors were obtained from each subject, and all the gait vectors were pooled together. Two gait vectors were randomly selected from the pool and tested if they could be accurately classified if they were from the same person or not. The gait from the cohort was classified with an accuracy of 99.71% using the support vector machine with a radial basis function kernel as a classifier. Gait of a person is as unique as his/her facial motion and finger impedance, but not as unique as fingerprints.

Application of Principal Component Analysis Approach to Predict Shear Strength of Reinforced Concrete Beams with Stirrups.

The reinforced concrete (RC) member's shear strength estimation has been experimentally studied in most cases due to its nonlinear behavior. Many empirical equations have been derived from the experimental data; however, even those adopted in the construction codes do not thoroughly and accurately describe their shear behavior. Theoretically explained equations, on the other hand, are aligned with the experiment; however, they are complicated to use in practice. As shear behavior research is data-driven, the machine learning technique is applicable. Herein, an artificial neural network (ANN) algorithm is trained with 776 experiment results collected from available publications. The raw data is preprocessed by principal component analysis (PCA) before the application of the ANN technique. The predictions of the trained algorithm using ANN with PCA are compared to those of formulae adopted in a few existing building codes. Finally, a parametric study is conducted, and the significance of each variable to the strength of RC members is analyzed.

Relationship between ankle varus moment during gait and radiographic measurements in patients with medial ankle osteoarthritis.

BACKGROUND: Kinetic data obtained during gait can be used to clarify the biomechanical pathogenesis of osteoarthritis of the lower extremity. This study aimed to investigate the difference in ankle varus moment between the varus angulation and medial translation types of medial ankle osteoarthritis, and to identify the radiographic measurements associated with ankle varus moment. METHODS: Twenty-four consecutive patients [mean age 65.8 (SD) 8.0 years; 9 men and 15 women] with medial ankle osteoarthritis were included. Fourteen and 10 patients had the varus angulation (tibiotalar tilt angle≥3 degrees) and medial translation (tibiotalar tilt angle<3 degrees) types, respectively. All patients underwent three-dimensional gait analysis, and the maximum varus moment of the ankle was recorded. Radiographic measurement included tibial plafond inclination, tibiotalar tilt angle, talar dome inclination, and lateral talo-first metatarsal angle. Comparison between the two types of medial ankle osteoarthritis and the relationship between the maximum ankle varus moment and radiographic measurements were analyzed. RESULTS: The mean tibial plafond inclination, tibiotalar tilt angle, talar dome inclination, lateral talo-first metatarsal angle, and maximum ankle varus moment were 6.4 degrees (SD 3.3 degrees), 5.0 degrees (SD 4.6 degrees), 11.4 degrees (SD 5.2 degrees), -6.5 degrees (SD 11.7 degrees), and 0.185 (SD 0.082) Nm/kg, respectively. The varus angulation type showed a greater maximum ankle varus moment than the medial translation type (p = .005). The lateral talo-first metatarsal angle was significantly associated with the maximum ankle varus moment (p = .041) in the multiple regression analysis. CONCLUSION: The varus angulation type of medial ankle osteoarthritis is considered to be more imbalanced biomechanically than the medial displacement type. The lateral talo-first metatarsal angle, being significantly associated with the ankle varus moment, should be considered for correction during motion-preserving surgeries for medial ankle osteoarthritis to restore the biomechanical balance of the ankle.

Posterior Tibial Tendon Integrity Can Be Screened With Plain Anteroposterior Foot Radiography.

Posterior tibial tendon integrity is an important consideration when treating adult-acquired flatfoot caused by posterior tibial tendon dysfunction. The condition of this tendon traditionally has been evaluated with ultrasonography or magnetic resonance imaging, but recent advances in radiography have increased the resolution of radiographic soft tissue images. The authors examined whether the posterior tibial tendon could be screened with anteroposterior foot radiographs, based on interobserver agreement and accuracy. The authors retrospectively evaluated consecutive patients who underwent weight-bearing foot radiography and ultrasonography based on suspicion of posterior tibial tendinopathy. The integrity of the posterior tibial tendon was evaluated by 2 orthopedic surgeons with foot radiographs and scored as normal or abnormal. The authors evaluated interobserver agreement and compared the findings of ultrasonography and radiography to evaluate diagnostic accuracy. The study included 21 patients with a mean age of 51.5±15.7 years. Ultrasonography showed that 4 patients had normal tendon integrity, 6 patients had tenosynovitis and no tendinopathy, 8 patients had tendinopathy and tendon continuity, and 3 patients had loss of tendon continuity. The surgeons provided consistent radiographic findings for 81.0% of patients (17 of 21). On the basis of the ultrasonographic findings, the surgeons' accuracy was 76.2% (16 of 21) and 61.9% (13 of 21). The results indicate that weight-bearing anteroposterior foot radiography can be used to evaluate posterior tibial tendon integrity, which may allow orthopedic surgeons to predict the prognosis of patients with posterior tibial tendon dysfunction, determine the extent of surgical treatment, and evaluate tendon integrity postoperatively. [Orthopedics. 2020;43(6):e503-e507.].