BACKGROUND:To provide improved treatment for hallux valgus (HV), we sought to understand more about the pathophysiologic connection between flatfoot deformity and HV by comparing coronal plane alignment of the medial column of the foot for patients with isolated HV, isolated flatfoot, and combined HV-flatfoot vs controls. METHODS:This study retrospectively assessed a consecutive series of 33 patients with combined symptomatic and radiographic HV and flatfoot, 33 isolated symptomatic HV, 33 isolated symptomatic flatfoot, and 33 controls. The medial column alignment was assessed in the coronal plane using 3-dimensional weightbearing computed tomography (WBCT); rotation was measured for the navicular, medial cuneiform, and first metatarsal (M1). The position of the first naviculocuneiform (NC) and tarsometatarsal (TMT) joints were determined. RESULTS:M1 intrinsic pronation was significantly greater in patients with combined HV-flatfoot (-12.0 ± 7.0 degrees; P < .001), isolated HV (-12.1 ± 6.6 degrees; P < .001), and isolated flatfoot (-11.8 ± 8.5 degrees; P < .001), compared with control patients (-19.4 ± 6.7 degrees). TMT was significantly more pronated in patients with combined HV-flatfoot (30.9 ± 6.2 degrees) compared with isolated flatfoot (25.3 ± 9.3 degrees; P = .007), and control (25.9 ± 5.2 degrees; P = .005), as it was in patients with isolated HV (33.2 ± 8.2 degrees) compared with isolated flatfoot (P < .001), and control (P < .001). NC was significantly more supinated in patients with combined HV-flatfoot (-23.7 ± 3.9 degrees) compared to isolated flatfoot (-18.0 ± 9.8 degrees; P = .001), and control (-18.0 ± 4.5 degrees; P < .001), as it was for patients with isolated HV (-24.8 ± 7.1 degrees) compared with isolated flatfoot (P = .003), and control (P < .001). CONCLUSION:In our study, we found that patients with isolated HV, isolated flatfoot, or combined HV-flatfoot presented a similar increase in M1 intrinsic pronation of approximately 7.5 degrees, compared with controls. Moreover, patients with isolated HV or combined HV-flatfoot had greater TMT pronation and NC supination, compared with patients with isolated flatfoot and controls.

Increasing utilization of weight-bearing computed tomography and fluoroscopy has driven the need for standardization of 3 dimensional (3D) measurements in the foot and ankle. These emerging imaging modalities are currently used to evaluate foot and ankle conditions including ankle osteoarthritis, progressive collapsing foot deformity, midfoot instability, and hallux valgus. This study aims first to provide a comprehensive review of clinical studies that have utilized these 3D methodologies. As a second goal, this study presents the methodological approach proposed by an international task force of experts toward addressing those concerns to provide validated guidelines for 3D static and dynamic measurements.

Background: Weightbearing cone-beam computed tomography (WBCT) has proven useful for analysis of structural changes of the foot and ankle when compared to conventional radiographs. WBCT allows for extraction of distance and coverage mapping metrics, which may provide novel insight into hallux rigidus (HR). This study retrospectively assessed HR joint space using distance and coverage mapping in a case-control study. Methods: WBCT images of the foot and ankle for 20 symptomatic HR and 20 control patients were obtained. Three-dimensional models were created and analyzed using a custom semiautomatic measurement algorithm. Distance and coverage mapping metrics for the first metatarsophalangeal and metatarsosesamoid joints were extracted from the models and compared between cohorts. Relationships between these metrics and visual analog scale (VAS) scores, a patient-reported outcome of pain, were assessed in HR patients. Results: Overall first metatarsophalangeal joint space narrowing was noted in HR patients when compared to controls by an average of 11.8% ( P = .02). However, no significant changes in the overall coverage of the joint were noted. Decreased joint space width and increased surface-to-surface coverage were only and particularly observed at the plantar medial quadrant of the first metatarsal head in HR patients relative to controls. VAS score was significantly but weakly correlated with dorsolateral quadrant coverage ( R2 = 0.26, P = .03). Conclusion: Distance and coverage mapping serve as a complementary option to current techniques of quantifying HR changes. These metrics can expand the scope of future work investigating joint articulation changes in HR.

Tarso-metatarsal joints and naviculocuneiform joints comprising midfoot is the second most commonly involved joints following the first metatarsophalangeal joint in the foot. However, related factors of midfoot arthritis (MA) have been rarely reported. The bony structure and alignment can be more precisely assessed using Weight-Bearing Computed Tomography (WBCT) than conventional radiographs. Therefore, the aim of this study was to investigate risk factors for MA related to medical history and comorbid foot deformities using WBCT. WBCT data from September 2014 to April 2022 were extracted from a single referral hospital. All cases were divided into two groups by the presence of MA. Twenty-five potential related factors including demographics, etiology, and common co-occurring foot deformities were collected for comparison. Six hundred six cases (247 males and 359 females) among consecutive 1316 cases between September 2014 to April 2022 were selected. One hundred thirty-nine male cases (56.3%) and 210 female cases (58.5%) showed MA. In stepwise multiple logistic regression analysis, 5 factors remained statistically significant. The multivariate-adjusted odds ratios for age, laterality, body mass index (BMI), Progressive Collapsing Foot Deformity (PCFD), and lesser toe deformities (LTD) were 1.08, 1.54, 1.05, 6.62, and 3.03 respectively. Risk factors for MA associated with medical history and foot deformities included age, laterality, BMI, PCFD, and LDT.

The 2019 progressive collapsing foot deformity (PCFD) consensus did not only change the disease nomenclature and provided a new classification for the condition formerly known as flatfoot deformity. It was also the pinnacle of a revolution in the field in terms of knowledge and clinical perspectives. The use of advanced imaging, such as weight-bearing computed tomography, three-dimensional algorithms, and magnetic resonance, expanded the way we understand peritalar subluxation and how we can address it. However, much of these improvements felt short in terms of global reproducibility due to economic restraints. The objective of this review study is to present PCFD new concepts through the lens and realities of developing countries, considering their potentially limited access to novel technologies. Level of Evidence V; Expert opinion.

Wrist and hand biomechanics under full-body load are not fully understood. To identify potential anatomy-related differences in hand loading, 15 former collegiate athletes completed a 45-second handstand on a novel emed (R) pressure platform system. Center of pressure (CoP) and force distribution across the palmar surface were analysed during the stabilised phase. Maximum force, mean pressure, and contact area were calculated in four palmar anatomic subregions: hypothenar, thenar, metacarpals, and fingers. These values were related to ulnar variance measurements obtained from a participant handstand hold in a weight-bearing computed tomography machine. About 93% of participants shifted their CoP towards their dominant hand (p < 0.001), and among all participants, the dominant hand applied an average of 8.91% (p = 0.002) higher maximum force than the nondominant hand. The proportion of total mean force was highest in the hypothenar (47.1%) and thenar regions (36.5%). Every 1.00 mm increase in ulnar variance corresponded to a 2.8% increase in maximum force in the hypothenar region (p = 0.037). This investigation emphasises the role of gymnastics hand dominance on left/right hand weight distribution and the importance of the hypothenar zone in distributing pressure during handstands. It also indicates that force transmission through the wrist to the palm is contingent on radioulnar positioning.

A CT-based method for objectively assessing fracture severity was previously developed and validated to address poor reliability in existing subjective fracture classification systems. The method involved quantifying the energy involved in creating a fracture. However, clinical utility of the method was hindered by reliance upon an intact contralateral CT and lengthy analysis time (8-10 h). Significant methodological improvements detailed here enable the assessment of fracture severity in any joints and bones, while obviating the need for an intact contralateral CT scan. Analysis time was reduced to <2 h per case. Fracture energies computed using the new methods showed strong agreement (R2 = 0.95, p < 0.001) with prior results in analyzing twenty tibial pilon fractures. New metrics, articular fracture edge length and subchondral energy, were developed to better describe joint injuries by incorporating knowledge of preferential chondrocyte death along fracture edges. Based on two-year radiographic grading for these pilon fractures, fracture energy, articular fracture edge length, and subchondral energy were all significantly different (p < 0.01) between cases that did or did not develop post-traumatic osteoarthritis. These developments enable measurement of fracture severity in larger populations and in more clinically relevant timeframes with articular fractures involving a variety of joints and bones. This generalized assessment method offers opportunity to change the way severity is considered in fracture treatment algorithms. Studies involving larger cohorts are anticipated to yield insights into the impact of fracture severity on PTOA risk and serve as a foundation for evaluating new treatment strategies.

Category: Trauma; Sports Introduction/Purpose: Prior studies have shown the potential of a rigid fixation, such as a trans-syndesmotic screw, to produce tibiofibular malreduction. Flexible implants, although capable of allowing forgiveness in these situations, may not provide sufficient initial stability for all injury patterns. The purpose of this study is to assess the malreduction forgiveness of a two-phase syndesmotic device that is designed to transition from a rigid screw construct to a flexible suture-type device upon weightbearing. Methods: Below-knee cadaveric specimens were mounted in a radiolucent frame with a static axial load of 356N under four conditions: native ankle (control), syndesmotic instability (injured ), malreduced with two-phase syndesmotic device engaged (malreduced ), and post-disengagement of the two-phase device (disengaged). A lateral approach was used to destabilize the joint. The malreduction targets for each group were 5mm anterior displacement, 5mm posterior displacement, 15° of rotation, and over-compressed (140N) states. Fixation was performed with a single implant 20mm proximal to the joint. Weightbearing Computed Tomography (WBCT) scans were obtained for each condition. The device was manually disengaged to allow for semi-constrained motion of the syndesmosis, reproducing the release that would occur when a patient initiates weightbearing. Anatomic axes of the tibia and fibula were extracted from WBCT scans to calculate tibiofibular joint position with an established orthogonal joint coordinate system representation. Results were normalized to the control states and compared. Results: A total of 42 limbs were included (anterior=10, posterior=11, rotation=12, over-compression=9). Anterior and posterior malreduction specimens demonstrated 2.50mm (SD: ±1.37mm) and 5.04mm (SD: ±2.23mm) of average malreduction in the malreduced state. The disengaged device condition resulted in an average recovery of 1.79mm (95%CI: 0.72mm, 2.85mm; p=0.0034; 72% recovery) and 1.69mm (95%CI: 0.09mm, 3.28mm; p=0.0006; 33% recovery) toward the control position of the joint, for anterior and posterior malreduction, respectively. Rotational malreduction specimens demonstrated 2.44° (SD: ±2.09°) of average absolute rotational malreduction, with 1.98° (95%CI: -0.13°, 4.09°; p=0.0707; 81% recovery) of recovery. Over-compression specimens demonstrated an average medial translation of 0.89mm (SD: ±1.10mm), and the disengaged device condition had 0.74mm (95%CI: 0.05mm, 1.51mm; p=0.0128; 82% recovery) of joint pose recovery. Conclusion: In this cadaveric study, malreduction forgiveness using a two-phase syndesmotic implant that transitions from a rigid screw to a flexible device was tested. Using the computational methods described, overall syndesmotic malreduction and specific corrective changes in fibular malpositioning following disengagement from a rigid construct were noted. The results support the implant concept on malreduction recovery in multiple planes, potentially impacting the clinical management of syndesmotic injuries. Application of this implant and our study methodology to a clinical cohort of patients with syndesmotic instability is paramount to confirm our findings.

Background:Recognizing ACL injuries on the field and in the office can be very challenging in awake and apprehensive patients. Despite high specificity, many published "pivot-shift" techniques have limited acceptance mainly because of unsatisfactory sensitivity. We describe in detail, four specific modifications and provide a critical review of our clinical experiences to empower the new user's readiness to master a novel screening procedure for ACL disruption. Methods:18 cadavers assessed instability kinematics of the novel technique. Clinical Exam Study Part II-A (ACL Disrupted): 208 awake, hemarthrosis patients with MRI evidence of ACL deficiency underwent 363 examinations by 41 examiners. Clinical Exam Study Part II-B: (ACL Intact) 47 consecutive posttraumatic hemarthrosis patients with intact ACLs underwent 76 examinations by 30 examiners. Results:Cadaveric study confirmed patterns of coupled, anterior translation-internal rotation pathologic laxity at 25.6±8.2 degrees flexion. Clinically, the novel test yielded sensitivity of 94.7% and Specificity of 97.3%. Potentially perplexing situations included: MRI availability; pain and anxiety-related traumatic hemarthrosis, protective hamstring antagonism and examiners experience. Conclusion:When the examiner and patient agree on a feeling of instability, the Albright-Losee Test maximizes ability to establish ACL status in the awake patient to the point that the sensitivity is even greater than the Lachman Test. Armed with background knowledge of our experiences confirms that, despite of impact of various challenging factors, the Positive Predictive Value 98.8% 95% CI (95.5%-99.7%) that a torn ACL exists in face of a positive exam confirms its value for sports medicine providers to master. Level of Evidence: II.

BACKGROUND:The diagnosis of syndesmotic instability is challenging, and chronically unstable injuries can potentially lead to ankle arthritic degeneration. The objective of this cadaveric study was to utilize a 3-dimensional (3D) weight-bearing computed tomography (WBCT) distance mapping algorithm for the detection of subtle syndesmotic instability, induced by complete syndesmotic ligament sectioning and stressed by isolated axial load. We hypothesized that this algorithm would accurately detect subtle syndesmotic instability. METHODS:Nineteen matched pairs of through-the-knee cadaveric specimens (38 legs) were utilized. Specimens were mounted in a frame that allowed simulated axial weight-bearing (356 N). Specimens were scanned using cone-beam WBCT in the normal pre-injury state and after complete syndesmotic ligament sectioning. The deltoid ligament was kept intact, and no external rotational stress was applied. Syndesmotic incisura and lateral gutter distances were assessed and compared between pre-injury ipsilateral, contralateral, and injured states using a 3D WBCT distance mapping algorithm. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were calculated for the comparison of syndesmotic distance measurements between injured specimens and controls. P values of <0.05 were considered significant. RESULTS:Overall, significantly increased distances were observed in injured specimens when compared with controls, with average relative syndesmotic widening in injured specimens of 16.9% (p = 0.0003), 11.3% (p = 0.0015), 6.4% (p = 0.0027), and 2.9% (p = 0.037) at the first 1, 3, 5, and 10 cm (proximal to the apex of the distal tibial articular surface), respectively. Widening was more pronounced in the anterior aspect of the syndesmosis, where the diagnostic accuracy was found to be highest at the first 1 and 3 cm of the syndesmotic incisura, with AUC values ranging from 80.9% to 83.0% (p < 0.0001) and with threshold diagnostic values of relative syndesmotic widening as low as 0.43 mm. CONCLUSIONS:The newly proposed 3D WBCT distance mapping algorithm was able to accurately detect subtle syndesmotic instability in a cadaveric model of complete syndesmotic sectioning under isolated axial weight-bearing load. This algorithm needs to be further validated in patients with suspected traumatic syndesmotic instability. CLINICAL RELEVANCE:This cadaveric study demonstrated high diagnostic accuracy of a 3D WBCT distance mapping algorithm to detect subtle syndesmotic instability when stressed with isolated axial loading and in the absence of deltoid injury. The future use of this algorithm in patients with suspected unilateral traumatic syndesmotic instability could hopefully optimize the diagnosis and treatment decision-making.

Computational models of the hip often omit patient-specific functional orientation when placing imaging-derived bony geometry into anatomic landmark-based coordinate systems for application of joint loading schemes. The purpose of this study was to determine if this omission meaningfully alters computed contact mechanics. Discrete element analysis models were created from non-weightbearing (NWB) clinical CT scans of 10 hip dysplasia patients (11 hips) and oriented in the International Society of Biomechanics (ISB) coordinate system (NWB-ISB). Three additional models were generated for each hip by adding patient-specific stance information obtained via weightbearing CT (WBCT) to each ISB-oriented model: (1) patient-specific sagittal tilt added (WBCT-sagittal), (2) coronal and axial rotation from optical motion capture added to (1; WBCT-combo), and (3) WBCT-derived axial, sagittal, and coronal rotation added to (1; WBCT-original). Identical gait cycle loading was applied to all models for a given hip, and computed contact stress and contact area were compared between model initialization techniques. Addition of sagittal tilt did not significantly change whole-joint peak ( p = 0.922) or mean ( p = 0.871) contact stress or contact area ( p = 0.638). Inclusion of motion-captured coronal and axial rotation (WBCT-combo) decreased peak contact stress ( p = 0.014) and slightly increased average contact area ( p = 0.071) from WBCT-sagittal models. Including all WBCT-derived rotations (WBCT-original) further reduced computed peak contact stress ( p = 0.001) and significantly increased contact area ( p = 0.001). Variably significant differences ( p = 0.001–1.0) in patient-specific acetabular subregion mechanics indicate the importance of functional orientation incorporation for modeling applications in which local contact mechanics are of interest.

BackgroundThe aim of this study was to investigate the epidemiology of Midfoot Arthritis (MA) and Lesser toe deformity (LTD) using Weight-Bearing Computed Tomography (WBCT).Methods606 cases (247 male, 359 female) among 1316 consecutive cases with WBCT data from September 2014 to April 2022 were retrospectively reviewed at a single referral institution. The Cochran-Armitage test was performed to evaluate the trend of prevalence with respect to age group and obesity classification.Results139 male (56.3%) and 210 female cases (58.5%) showed MA. 157 male (63.6%) and 222 female cases (61.6%) showed LTD. 115 male (19.0%) and 157 female cases (25.9%) showed both MA and LTD. The prevalence of MA and LTD increased with age in both genders. The incidence of MA in males showed an increasing tendency until obesity class II and then was slightly decreased in obesity class III. This is contrary to females whose prevalence increased with increasing obesity groups. LTD had a similar pattern in both genders to obesity classification.ConclusionsThe prevalence of MA and LTD increased with age and increasing obesity groups for both genders.Level of EvidenceLevel III, Retrospective Comparative Study.

Treatment of end-stage ankle conditions is a complex challenge in foot and ankle surgery. The talus is prone to issues such as osteoarthritis (OA) and avascular necrosis (AVN). Patient-specific total ankle and total talus replacement (TATTR) procedures have emerged as potential solutions, but the decision to include subtalar arthrodesis in these surgeries is multifaceted. In this study, we aimed to understand the relationship between past surgeon decisions for fusion with TATTR and three-dimensional joint health assessments using preoperative CT data. Twenty-seven TATTR with subtalar fusion and 19 TATTR without subtalar fusion were analyzed. Each patient underwent a bilateral computed tomography scan, which was segmented prior to surgery. Distance mapping of various subtalar regions was performed, and average distance was reported. For better analysis, the sinus tarsi was divided into four sectors and the calcaneus posterior facet into nine sectors. Statistical analysis involved calculating the difference in means between the fused and unfused cases. The fusion group exhibited significant joint space narrowing in the posterolateral aspect of the sinus tarsi (p = 0.021). Conversely, on the posterior facet of the subtalar joint, the fusion group showed significant joint space widening in both the anteromedial (p = 0.025) and middle/medial (p = 0.032) sections. Surgeons' decision to perform subtalar arthrodesis in TATTR procedures often aligns with clinical signs of sinus tarsi impingement, as evidenced by significant changes in joint space measurements. While joint health assessments play a pivotal role, other factors, such as surgeon preference and patient-specific considerations, also influence decision-making.

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: Progressive Collapsing Foot Deformity (PCFD) can present with independent deformities, characterized by five classes: hindfoot valgus (Class A), midfoot abduction (Class B), forefoot varus (Class C), Peritalar Subluxation (PTS) (Class D) and ankle valgus (Class E). Conservative treatment includes the use of corrective insoles and orthotics. Arch support inflatable Ankle-Foot orthoses (IAFO) can help control symptoms in PCFD patients. However, the ability of IAFOs to correct deformities in PCFD is unknown. The aim of this prospective comparative and controlled study was to assess the ability of arch support IAFOs to correct 3D overall PCFD alignment as well as the five different PCFD classes independently. We hypothesized that IAFOs would correct PCFD 3D overall alignment as well as the five independent classes of deformity. Methods: After IRB approval, we enrolled 24 symptomatic PCFD and 24 controls matched on age, sex, and BMI. Flexible PCFD patients and controls were scanned using Weight-Bearing CT (WBCT) with and without an arch support IAFO. The Foot and Ankle Offset (FAO) was used to assess the 3D foot overall alignment. We measured the Hindfoot moment arm (HMA, Class A), the Talonavicular coverage angle (TNCA, Class B), the Meary’s angle and medial cuneiform-to-floor distance (C1-floor) for the Class C and the middle facet uncoverage (MFunco, Class D). No Class E patients were included. Measurements were performed by two fellowship-trained surgeons. A power-analysis hypothesizing that IAFOs would be two times less efficient than the PCFD surgery in correcting the FAO, the requisite number of subjects was 24 per group. Data normality was assessed by Shapiro-Wilk test. Comparisons used normality based paired T-tests or paired-Wilcoxon tests. P-values < 0.05 were considered significant. Results: PCFD measurements performed in controls were all significantly less pronounced than unbraced PCFD patients, confirming the presence of collapse (ps < 0.0001). Comparing PCFD without and with IAFO, the FAO did not show significant improvement (respectively 6.6+/-3.7% vs 5.5+/-4.2%, p=0.101). The HMA (8.8+/-5.8 vs 8.1+/-5.8, p=0.66), the TNCA (24.2+/-10.6 vs 21.9+/-9.7, p=0.44) and the MFunco (37+/-12% vs 31+/-18%, p=0.17) also did not portray significant improvements when applying the IAFOs. The Meary’s angle (17.6+/-7.2 vs 10.8+/-7.3, p=0.002) and C1-floor (17.2+/-3.3mm vs 24.1+/-5.3mm, p< 0.001) were the only to improve significantly with use of IAFOs. When comparing braced PCFD and controls, the only measurement that improved to normal values, similar to controls, in braced PCFD was the C1-floor (24.1+/-5.3mm in PCFD with IAFO vs 25.7+/- 5.4mm in controls, p=0.31). Conclusion: In this prospective comparative and controlled study, we found that arch support IAFOs was not able to correct overall 3D deformity and most of the specific classes in PCFD. The orthosis did not improve hindfoot valgus (Class A), midfoot abduction (Class B) or peritalar subluxation (Class D) in PCFD. The only deformity pattern to improve with the use of IAFOs was the medial longitudinal arch height (Class C). These improvements were expected by the presence of the inflatable bladder of the IAFO on the plantar aspect of the foot, pushing the longitunal arch up but not correcting the entire PCFD.

Category: Ankle Arthritis; Other Introduction/ Purpose: Lower limb alignment assessment is commonly performed using two-dimensional (2D) conventional- radiographs. Weight-Bearing Computed-Tomography (WBCT) imaging that allows concomitant 3D imaging of the hip, knee, ankle, and foot, a more complete and multidimensional assessment of the entire overall lower limb alignment is now possible. The aims of this study were: (1) to characterize the normal relative 3D alignment of the center of the Hip, Knee, and Ankle joints in relation to the weight bearing Foot Tripod in a cohort of healthy control volunteers with no lower extremity pathologies, using WBCT imaging. (2) to perform the same 3D WBCT assessment in a cohort of patients with either hip osteoarthritis (HOA), knee osteoarthritis (KOA) or ankle osteoarthritis (AOA), and to compare the results between arthritic cases and controls. Methods: Prospective comparative and controlled cohort-study contained 7 HOA limbs (4 patients), 17 KOA limbs (10 patients), 7 AOA limbs (4 patients) and 10 control limbs (5 patients) that received WBCT imaging of the full lower extremity. Using multiplanar reconstruction WBCT images, 3D landmark coordinates (on X, Y, and Z planes) were manually measured by two observers. The utilized software (CubeVue ® ) generated an automatic calculation of the Foot-Hip Offset (FHO), Foot-Knee Offset (FKO) and Foot and Ankle Offset (FAO). The relationship between the center of the hip, knee and ankle joints and the bisecting line of the foot tripod was assessed and compared between HOA, KOA, AOA patients and controls. Examples of measurements for arthritic patients and controls is presented in Figure 1. Continuous data was assessed for normality with the Shapiro-Wilk test, and variables were compared using ANOVA or Kruskal- Wallis Rank Sum. P-Values of less than 0.05 were considered significant. Results: The average FAO and 95%-Confidence-intervals-(CI) for respectively HOA, KOA, AOA and controls were respectively: 3.62% (0.4 to 6.8) (neutral), 2.8% (0.78 to 4.9) (neutral), -4.68% (-7.8 to -1.4) (varus), and 2.12% (-0.5 to 4.8) (neutral). The FAO- differences were found to be significant between the groups (p=0.0077), with AOA patients being significantly different than all the other groups (Figure 2). Similarly, the HFO was found to be significantly different-between the groups (p=0.002), with the following average values and 95%CI for respectively HOA, KOA, AOA and controls: 0.7% (-6.4 to 7.8), 2.3% (-2.3 to 6.8), -10.1% (-17.2 to -3.0), and 5.3% (-0.6 to 11.3). Again, the AOA patients were found to be significantly different than the other groups. No significant differences were found between the groups when assessing the KFO (p=0.37). Conclusion: The baseline 3D lower limb alignment and relative position of the hip, knee, ankle and foot was assessed and established for the first time in the literature. When comparing 3D alignment in arthritic patients with hip, knee or ankle OA and controls, we observed that AOA was found to be the one affecting more the overall 3D alignment of the lower extremity, with no complete compensation of the deformity through the other joints, resulting in significantly different values of HFO, KFO and FAO in patients with ankle OA. Additional prospective studies with longer cohorts of patients are needed.

PURPOSE:Ulnar variance (UV) is a radiographic measurement relating the articular surface heights of the distal radius and ulna. Abnormal UV increases the risk for wrist pathology; however, it only provides a static measurement of an inherently dynamic bony relationship that changes with wrist position and loading. The purpose of this study was to investigate how full-body weight-bearing affects UV using weight-bearing computed tomography (WBCT). METHODS:Ten gymnasts completed two 45-second scans inside a WBCT machine while performing a handstand on a flat platform (H) and parallettes (P). A non-weight-bearing CT scan was collected to match clinical practice (N). Differences in UV between weight-bearing conditions were evaluated separately for dominant and nondominant sides, and then, UV was compared between weight-bearing conditions on pooled dominant/nondominant data. RESULTS:Pooled analyses comparing weight-bearing conditions revealed a significant increase in UV for H versus N (0.58 mm) and P versus N (1.00 mm), but no significant change in UV for H versus P (0.43 mm). Significant differences in UV were detected for H versus N, P versus N, and H versus P for dominant and nondominant extremities. The change from N to H was significantly greater in the dominant versus nondominant side, but greater in the nondominant side from N to P. CONCLUSIONS:Ulnar variance changed with the application of load and position of the wrist. Differences in UV were found between dominant and nondominant extremities. CLINICAL RELEVANCE:Upper extremity loading patterns are affected by hand dominance as defined by a cartwheel and suggest skeletal consequences from repetitive load on a dominantly used wrist. Although statistically significant, subtle changes detected in this investigational study do not necessarily bear clinical significance. Future WBCT research can lead to improved diagnostic measures for wrist pathologies affected by active loading and rotational wrist behavior.

Category: Hindfoot; Other Introduction/Purpose: Treatment of Progressive Collapsing Foot Deformity (PCFD) is controversial and surgical procedures utilized usually depend on the type and rigidity of deformities present (PCFD classes and stages), degree of soft tissue involvement, and surgeon’s preference. Multiple surgical procedures are usually performed concomitantly to achieve adequate correction. Prospective data regarding the utilization of hindfoot joint-sparing reconstructive procedures in the treatment of flexible PCFD is scarce, and little is known about the influence of the different procedures utilized to treat PCFD in deformity correction and patient-reported outcomes (PROs). The objective of this prospective study was to evaluate the most used hindfoot joint-sparing procedures utilized by a single-surgeon to treat flexible PCFD, and the influence of the utilized procedures in deformity pattern corrections, and PROs. Methods: IRB-approved, prospective, and comparative cohort study. Adult PCFD patients with flexible deformity (stage 1), no history of surgical treatment, and that failed conservative treatment for >3-months were enrolled. Patients underwent surgical treatment by a single-surgeon. Patients were excluded if a hindfoot fusion procedure was needed intra-operatively to achieve correction. Types, numbers, and sizes of surgical procedures utilized were recorded. Weight-bearing CT (WBCT) measurements of overall 3D deformity, Classes A (hindfoot valgus), B (abduction), C (medial column instability), D (peritalar subluxation), and E (ankle valgus tilt) were assessed preoperatively, and at first 3-months WBCT. PROs were recorded preoperatively and at the most recent follow-up. Descriptive statistics were used to report the frequency of deformity and procedures utilized. Pre and postoperative measurements and PROs were compared with paired T-tests/Wilcoxon. Multivariate regression analysis was used to correlate procedures utilized with deformity correction and PROs. P-values of >0.05 were considered significant. Results: A total of 29 patients included (28 feet, 79%F, 21%M), mean age and BMI of respectively 47.6-years and 34kg/m 2 . Average number of procedures performed was five and mean follow-up was 19.1 months (range, 3 to 40). Frequency and sizes of medial displacement calcaneal osteotomy (MDCO), first ray plantarflexion procedure (Cotton/LapiCoton), and lateral column lengthening (LCL) procedures were, respectively: 100% (8.9mm displacement), 100% (66% Lapicotton/34% Cotton, 8.3mm wedge-opening) and 39% (6.8mm wedge-opening). Soft-tissue procedures performed: 83% Posterior tibial tendon (re-tensioning/FDL transfer/allograft reconstruction), 34% peroneal tendon (brevis-to-longus and brevis lengthening), 76% gastrocnemius-recession, 38% spring ligament (re-tensioning/reconstruction/augmentation) and 31% deltoid ligament (re- tensioning/reconstruction/augmentation). Significant improvement postoperatively was observed in all PCFD measurements performed and PROs (Figure). However, no direct correlation was found between procedures performed/measurement improvements and PROs. Conclusion: In this prospective comparative cohort study of flexible PCFD patients undergoing surgical treatment with hindfoot joint sparing surgical procedures, we observed significant postoperative improvement in all deformity patterns assessed (Classes A, B, C, and D) as well as PROs. MDCO and first ray plantarflexion procedures (Cotton or LapiCotton) were the most commonly utilized procedures and were performed in all cases. Even though deformity correction and PRO improvements were observed postoperatively, no direct correlation was observed between PROs and specific surgical procedures performed or deformity pattern corrections (PCFD classes).

Category: Midfoot/Forefoot; Basic Sciences/Biologics; Hindfoot Introduction/Purpose: A recent study published in Nature (Venkadesan et al.) demonstrated that coupling the transverse arch (TA) with the medial longitudinal arch (MLA) significantly increased midfoot intrinsic stiffness. The contribution of the TA is substantial, suggested as the evolutionary advancement providing the foot stiffness required for human bipedalism. Progressive collapsing foot deformity (PCFD) is a complex deformity ultimately resulting in loss of stiffness and collapse of the MLA. The novel understanding of the TA may play a key role in the pathogenesis of this deformity. The objectives of this study were to assess and compare the TA curvature in PCFD and controls and to evaluate its relationship with accepted PCFD measures. We hypothesized that the curvature of the TA will be decreased in PCFD. Methods: A retrospective review was conducted for 32 PCFD and 32 controls. Measurements were performed using weight- bearing CT (WBCT). A novel measurement, the transverse arch plantar (TAP) angle, was designed to directly measure the TA in both PCFD (Figure 1a) and controls (Figure 1b). TA curvature was calculated using the equation described by Venkadesan et al. (Figure 6) utilizing width, length (Figure 3a), 3rd metatarsal thickness (Figure 3b), and 4th metatarsal torsion (Figure 4a, 4b). Finally, uni- and multivariate analyses were performed to analyze the relationship between the TAP angle, Foot and Ankle Offset (FAO), peritalar subluxation, and measurements associated with PCFD classes: hindfoot moment arm (class A), talonavicular coverage angle (class B), Meary angle (class C), medial facet uncoverage angle (class D), and talar tilt (class E). Normality of different variables was assessed using the Shapiro-Wilk test. Two groups were compared using t-test for normal, and Mann-Whitney for non-normal variables. Results: Measurements of the TAP angle were found to be significantly higher in the PCFD group than the control group with a mean angle of 115.24° (SD 10.68) and 100.76° (SD 7.92) respectively (p<0.001) (Figure 2).No significant difference was found in the calculated TA curvature between PCFD and controls with mean values of 17.84 (SD 4.41) and 18.18 (SD 3.68) respectively (p=0.741) (Figure 5).The univariate analysis performed showed a moderate positive correlation between the TAP angle and the FAO (ρ=0.58;r2=0.34;p <0.001).The multivariate analyses showed, among the different PCFD class measurements and the TAP angle, only the middle facet uncoverage (β=0.08,p<0.001) and hindfoot moment arm (β=0.32, p<0.001) were associated with higher values of FAO, while only the Meary (β=0.49,p=0.004) and the talonavicular coverage angles were associated with higher values of peritalar subluxation (β=0.75,p<0.001). Whereas, Meary's angle was the only predictive factor of higher TA collapse (β=0.55,p<0.001). Conclusion: Our direct measurement showed a collapsed of the TA in PCFD. However, this did not appear to be a consequence of insufficient bone torsion, but rather some other etiology, possibly a soft tissue failure. Considering the implication of the TA among the different PCFD classes, it did not appear to play a significant role on the overall PCFD deformity. TA collapse seemed mainly influenced by Meary's angle, which assess the MLA. This further supports the idea behind TA and MLA coupling suggesting that when the TA is collapsed, the foot does not possess the required stiffness to maintain the MLA.

Category: Other; Midfoot/Forefoot Introduction/Purpose: WBCT provides anatomical imaging that allows for extraction of metrics characterizing three-dimensional (3D) joint surface interactions. Three-dimensional (3D) Distance-Mapping (DM) and Coverage-Mapping (CM) use WBCT images to evaluate multiplanar elements of Hallux Rigidus (HR) through analyzing joint space and joint coverage across entire bony interfaces. Previous methods have struggled to characterize reliable assessment of these deformity patterns is essential in guiding HR treatment and impacts recurrence rates following correction. The objective was to (1) develop a 3D WBCT CM and DM algorithm to characterize the surface interaction of the 1st metatarsophalangeal-joint (MTPJ) and metatarsal-sesamoid joints (MTSJ) in HR patients and controls (2) correlate DM and CM with Body-Mass-Index (BMI), Coughlin and Shurnas classification- score (CGS), and pre-operative Visual-Analog-Scale (VAS). Methods: Retrospective case-control-study with Forty-one patients (20 HR and 21 controls). Semi-automatic segmentation protocol extracted bone models, which were analyzed with specialized-software. The 1st-MTPJ-surface was divided into two-by- two grids to provide a more detailed analysis. Distance measurements obtained were used to create color-coded distance maps. Blue color was represented expected distances in joint interaction (1 to 5 mm), red or yellow color represented arthritis or impingement (0 to 1mm), and pink color represented subluxation (>5mm). Further, color-coded coverage maps highlighted areas of relative coverage( < 5mm) or uncoverage(>5mm) contrasting areas with normal joint interaction or subluxation (Figure). Pearson correlations were computed between mapping metrics and the following for HR patients: Body-Mass-Index (BMI), Coughlin and Shurnas classification-score (CGS), and pre-operative Visual-Analog-Scale (VAS). Intraclass correlation coefficients (ICCs) were calculated to evaluate the interobserver reliability of the CCA selections and CGS obtained by two raters. One rater’s CCA selections and CGS were used for analysis. Results: HR patients displayed joint space narrowing at the first MTP joint when compared to controls (difference in means (DIM) = -11.8%,p=0.02). Quadrant analysis revealed first MTP joint space narrowing in HR patients for the plantar medial quadrant (DIM = -16.8%,p=0.002). Overall coverage in first MTPJ interaction for HR was increased, but not significant compared to controls (DIM = 9.2%,p=0.084). Quadrant analysis revealed increased coverage in first MTP joint surface-to-surface interaction for the plantar medial quadrant of the first metatarsal head (DIM = 13.7%,p=0.005) in HR patients when compared to controls. BMI was moderately positively correlated with mean first metatarsal head JSW (Joint space width) in HR patients (r=0.552,p=0.011). CGS was negatively correlated with mean first metatarsal head JSW for the HR cohort (r= -0.534,p=0.015). Conclusion: We developed a quantifiable WBCT distance and coverage map algorithm to assess 3D joint interaction, joint coverage, and subluxation in patients with HR. Compared to healthy controls, HR patients had increased joint space narrowing at the first metatarsal joint, both overall and specifically at the plantar medial aspect of the joint. Significantly increased coverage at the plantar medial quadrant was also observed in HR patients. Significant narrowing was not observed at the MTSJ. We found a significant correlation between Distance/Coverage mapping, Body-Mass-Index, and Coughlin and Shurnas classification score.