Quantitative Skeletal Imaging and Image-Based Modeling in Pediatric Orthopaedics.

PURPOSE OF REVIEW: Musculoskeletal imaging serves a critical role in clinical care and orthopaedic research. Image-based modeling is also gaining traction as a useful tool in understanding skeletal morphology and mechanics. However, there are fewer studies on advanced imaging and modeling in pediatric populations. The purpose of this review is to provide an overview of recent literature on skeletal imaging modalities and modeling techniques with a special emphasis on current and future uses in pediatric research and clinical care. RECENT FINDINGS: While many principles of imaging and 3D modeling are relevant across the lifespan, there are special considerations for pediatric musculoskeletal imaging and fewer studies of 3D skeletal modeling in pediatric populations. Improved understanding of bone morphology and growth during childhood in healthy and pathologic patients may provide new insight into the pathophysiology of pediatric-onset skeletal diseases and the biomechanics of bone development. Clinical translation of 3D modeling tools developed in orthopaedic research is limited by the requirement for manual image segmentation and the resources needed for segmentation, modeling, and analysis. This paper highlights the current and future uses of common musculoskeletal imaging modalities and 3D modeling techniques in pediatric orthopaedic clinical care and research.

Automatic anatomical foot and ankle coordinate toolbox.

Accurate analysis of bone position and orientation in foot and ankle studies relies on anatomical coordinate systems (ACS). Reliable ACSs are necessary for many biomechanical and clinical studies, especially those including weightbearing computed tomography and biplane fluoroscopy. Existing ACS approaches suffer from limitations such as manual input, oversimplifications, or non-physiological methods. To address these shortcomings, we introduce the Automatic Anatomical Foot and Ankle Coordinate Toolbox (AAFACT), a MATLAB-based toolbox that automates the calculation of ACSs for the major fourteen foot and ankle bones. In this manuscript, we present the development and evaluation of AAFACT, aiming to provide a standardized coordinate system toolbox for foot and ankle studies. The AAFACT was evaluated using a dataset of fifty-six models from seven pathological groups: asymptomatic, osteoarthritis, pilon fracture, progressive collapsing foot deformity, clubfoot, Charcot Marie Tooth, and cavovarus. Three analyses were conducted to assess the reliability of AAFACT. Firstly, ACSs were compared between automatically and manually segmented bone models to assess consistency. Secondly, ACSs were compared between individual bones and group mean bones to assess within-population precision. Lastly, ACSs were compared between the overall mean bone and group mean bones to assess the overall accuracy of anatomical representation. Statistical analyses, including statistical shape modeling, were performed to evaluate the reliability, accuracy, and precision of AAFACT. The comparison between automatically and manually segmented bone models showed consistency between the calculated ACSs. Additionally, the comparison between individual bones and group mean bones, as well as the comparison between the overall mean bone and group mean bones, revealed accurate and precise ACSs calculations. The AAFACT offers a practical and reliable solution for foot and ankle studies in clinical and engineering settings. It accommodates various foot and ankle pathologies while accounting for bone morphology and orientation. The automated calculation of ACSs eliminates the limitations associated with manual input and non-physiological methods. The evaluation results demonstrate the robustness and consistency of AAFACT, making it a valuable tool for researchers and clinicians. The standardized coordinate system provided by AAFACT enhances comparability between studies and facilitates advancements in foot and ankle research.

Morphologic analysis of the 1st and 2nd tarsometatarsal joint articular surfaces.

Tarsometatarsal joint arthrodesis is used to treat a variety of injuries and deformities in the midfoot. However, the surgical technique has not been optimized, in part due to limited knowledge of morphologic features and variation in the related joints. Previous research has relied primarily on dissection-based anatomical analysis, but quantitative imaging may allow for a more sophisticated description of this complex. Here, we used quantitative micro-CT imaging to examine dimensions, distance maps, and curvature of the four articular surfaces in the first and second tarsometatarsal joints. Image segmentation, articular surface identification, and anatomic coordinate systems were all done with semi or fully automatic methods, and distance and size measurements were all taken utilizing these anatomic planes. Surface curvature was studied using Gaussian curvature and a newly defined measure of curvature similarity on the whole joint and on four subregions of each surface. These data show larger articular surfaces on the cuneiforms, rather than metatarsals, and define the generally tall and narrow articular surfaces seen in these joints. Curvature analysis shows minimally curved opposing convex surfaces. Our results are valuable for furthering knowledge of surgical anatomy in this poorly understood region of the foot.

Statistical multi-level shape models for scalable modeling of multi-organ anatomies.

Statistical shape modeling is an indispensable tool in the quantitative analysis of anatomies. Particle-based shape modeling (PSM) is a state-of-the-art approach that enables the learning of population-level shape representation from medical imaging data (e.g., CT, MRI) and the associated 3D models of anatomy generated from them. PSM optimizes the placement of a dense set of landmarks (i.e., correspondence points) on a given shape cohort. PSM supports multi-organ modeling as a particular case of the conventional single-organ framework via a global statistical model, where multi-structure anatomy is considered as a single structure. However, global multi-organ models are not scalable for many organs, induce anatomical inconsistencies, and result in entangled shape statistics where modes of shape variation reflect both within- and between-organ variations. Hence, there is a need for an efficient modeling approach that can capture the inter-organ relations (i.e., pose variations) of the complex anatomy while simultaneously optimizing the morphological changes of each organ and capturing the population-level statistics. This paper leverages the PSM approach and proposes a new approach for correspondence-point optimization of multiple organs that overcomes these limitations. The central idea of multilevel component analysis, is that the shape statistics consists of two mutually orthogonal subspaces: the within-organ subspace and the between-organ subspace. We formulate the correspondence optimization objective using this generative model. We evaluate the proposed method using synthetic shape data and clinical data for articulated joint structures of the spine, foot and ankle, and hip joint.

Joint coverage analysis in progressive collapsing foot deformity.

Progressive collapsing foot deformity (PCFD) is characterized by a progressive subluxation of the peritalar bones and respective joints. Two-dimensional conventional radiographs are limited in their ability to visualize the peritalar bones and joints with adequate detail to describe the complex three-dimensional deformity. An improved understanding of the relationship between joint coverage and deformity would allow clinicians to use coverage analysis to distinguish among the stages of PCFD. The aim of this study was to analyze the joint coverage of the six articular relationships within the talocrural, subtalar, and Chopart joints using weightbearing computed tomography (WBCT) scans. Ten individuals with a flexible hindfoot and ten individuals with a rigid hindfoot presentation of PCFD were compared to twenty-seven asymptomatic control individuals. The three most relevant findings are: (I) the anterior-medial facet of the subtalar joint contains the greatest reduction in coverage for patients with a rigid deformity, (II) an increase in talonavicular overlap (TNO) moderately correlated with a decreased coverage in the: tibiotalar, anterior-medial subtalar, talonavicular joints, and (III) the calcaneocuboid joint lacks radiographic values to adequately quantify alignment and coverage. To conclude, there were significant differences in coverage area of various articulating regions throughout the hind- and midfoot when comparing PCFD patients to asymptomatic control individuals. Relevant radiographic measures correlating to articular coverage areas of clinical interest were identified, possibly helping to better quantify PCFD in clinical practice.

Biomechanical Insights Afforded by Shape Modeling in the Foot and Ankle.

Advancements in volumetric imaging makes it possible to generate high-resolution three-dimensional reconstructions of bones in throughout the foot and ankle. The use of weightbearing computed tomography allows for the analysis of joint relationships in a consistent natural position that can be used for statistical shape modeling. Using statistical shape modeling, a population-based statistical model is created that can be used to compare mean bone shape morphology and identify anatomical modes of variation. A review is presented to highlight the current work using statistical shape modeling in the foot and ankle with a future view of the impact on clinical care.

Acetabular labrum and cartilage contact mechanics during pivoting and walking tasks in individuals with cam femoroacetabular impingement syndrome.

Femoroacetabular impingement syndrome (FAIS) is a motion-related pathology of the hip characterized by pain, morphological abnormalities of the proximal femur, and an elevated risk of joint deterioration and hip osteoarthritis. Activities that require deep flexion are understood to induce impingement in cam FAIS patients, however, less demanding activities such as walking and pivoting may induce pain as well as alterations in kinematics and joint stability. Still, the paucity of quantitative descriptions of cam FAIS has hindered understanding underlying hip joint mechanics during such activities. Previous in silico studies have employed generalized model geometry or kinematics to simulate impingement between the femur and acetabulum, which may not accurately capture the interplay between morphology and motion. In this study, we utilized models with participant-specific bone and articular soft tissue anatomy and kinematics measured by dual-fluoroscopy to compare hip contact mechanics of cam FAIS patients to controls during four activities of daily living (internal/external pivoting and level/incline walking). Averaged across the gait cycle during incline walking, patients displayed increased strain in the anterior joint (labrum strain: p-value = 0.038, patients: 11.7 ± 6.7 %, controls: 5.0 ± 3.6 %; cartilage strain: p-value = 0.029, patients: 9.1 ± 3.3 %, controls: 4.2 ± 2.3). Patients also exhibited increased average anterior cartilage strains during external pivoting (p-value = 0.039; patients: 13.0 ± 9.2 %, controls: 3.9 ± 3.2 %]). No significant differences between patient and control contact area and strain were found for level walking and internal pivoting. Our study provides new insights into the biomechanics of cam FAIS, including spatiotemporal hip joint contact mechanics during activities of daily living.

Patients with cam-type femoroacetabular impingement demonstrate increased change in bone-to-bone distance during walking: A dual fluoroscopy study.

Cam-type femoroacetabular impingement (FAI) syndrome is a painful, structural hip disorder. Herein, we investigated hip joint mechanics through in vivo, dynamic measurement of the bone-to-bone distance between the femoral head and acetabulum in patients with cam FAI syndrome and morphologically screened controls. We hypothesized that individuals with cam FAI syndrome would have larger changes in bone-to-bone distance compared to the control group, which we would interpret as altered joint mechanics as signified by greater movement of the femoral head as it articulates within the acetabulum. Seven patients with cam FAI syndrome and 11 asymptomatic individuals with typical morphology underwent dual fluoroscopy imaging during level and inclined walking (upward slope). The change in bone-to-bone distance between femoral and acetabular bone surfaces was evaluated for five anatomical regions of the acetabulum at each timepoint of gait. Linear regression analysis of the bone-to-bone distance considered two within-subject factors (activity and region) and one between-subjects factor (group). Across activities, the change in minimum bone-to-bone distance was 1.38-2.54 mm for the cam FAI group and 1.16-1.84 mm for controls. In all regions except the anterior-superior region, the change in bone-to-bone distance was larger in the cam group than the control group (p ≤ 0.024). An effect of activity was detected only in the posterior-superior region where larger changes were noted during level walking than incline walking. Statement of clinical significance: Patients with cam FAI syndrome exhibit altered hip joint mechanics during the low-demand activity of walking; these alterations could affect load transmission, and contribute to pain, tissue damage, and osteoarthritis.

Medial Head of the Gastrocnemius Tenotomy Through a Posteromedial Approach Significantly Improves Surgical Accessibility of the Tibial Plateau.

OBJECTIVES: Compare accessible area of the posterior tibial plateau through a modified posteromedial (PM) approach before and after tenotomy of the medial head gastrocnemius. We report the outcomes of 8 patients who underwent gastrocnemius tenotomy during PM approach. METHODS: A modified PM approach was performed on 10 cadaveric legs, and the surgically accessible area was outlined. Next, a medial head gastrocnemius mid substance tenotomy was completed, and the accessible area was again outlined. Tibia specimens were imaged in a micro-CT scanner to measure accessible surface area and linear distance along the joint line. In addition, 8 patients who underwent tenotomy for tibial plateau fracture had outcomes recorded. RESULTS: The modified PM approach with tenotomy provided significantly more access to the posterior plateau than without tenotomy. The modified PM approach before tenotomy allowed access to 1774 mm 2 (SD = 274) of the posterior plateau surface and 2350 mm 2 (SD = 421, P < 0.0001) with tenotomy. A linear distance of 38 mm (SD = 7) and 57 mm (SD = 7, P < 0.00001) was achieved before and after tenotomy, respectively. In the clinical series, the average knee arc of motion was 116 degrees (95-135). CONCLUSIONS: The modified PM approach with medial head gastrocnemius tenotomy significantly improves surgical access to the posterior plateau. Patients who received tenotomy have acceptable functional outcomes. This cadaveric study provides an alternative approach for treatment of posterolateral tibial plateau fractures which may mitigate damage to neurovascular structures.

Multi-level multi-domain statistical shape model of the subtalar, talonavicular, and calcaneocuboid joints.

Traditionally, two-dimensional conventional radiographs have been the primary tool to measure the complex morphology of the foot and ankle. However, the subtalar, talonavicular, and calcaneocuboid joints are challenging to assess due to their bone morphology and locations within the ankle. Weightbearing computed tomography is a novel high-resolution volumetric imaging mechanism that allows detailed generation of 3D bone reconstructions. This study aimed to develop a multi-domain statistical shape model to assess morphologic and alignment variation of the subtalar, talonavicular, and calcaneocuboid joints across an asymptomatic population and calculate 3D joint measurements in a consistent weightbearing position. Specific joint measurements included joint space distance, congruence, and coverage. Noteworthy anatomical variation predominantly included the talus and calcaneus, specifically an inverse relationship regarding talar dome heightening and calcaneal shortening. While there was minimal navicular and cuboid shape variation, there were alignment variations within these joints; the most notable is the rotational aspect about the anterior-posterior axis. This study also found that multi-domain modeling may be able to predict joint space distance measurements within a population. Additionally, variation across a population of these four bones may be driven far more by morphology than by alignment variation based on all three joint measurements. These data are beneficial in furthering our understanding of joint-level morphology and alignment variants to guide advancements in ankle joint pathological care and operative treatments.

Dual Approach to Talar Dome Increases Access for Fracture Care Without Osteotomy.

BACKGROUND: There is no consensus surgical treatment algorithm for talar body fractures, with authors recommending both soft tissue-only and osteotomy-based approaches. This study evaluates talar dome access via dual approaches to the talar dome through anterolateral transligamentous (ATL) and modified posteromedial (mPM) approaches. METHODS: Ten cadaveric legs (5 matched pairs) were included. An mPM approach, between flexor hallucis longus and Achilles tendon, and an ATL approach, utilizing the anterolateral interval with transection of anterior talofibular ligament and calcaneofibular ligament, were performed on each specimen. Order of approach was alternated within each pair. Accessible dome surface area (DSA) was outlined by drilling with a 1.6-mm Kirschner wire at the visualized talar dome margin both with and without 4 mm of tibiotalar distraction using an external fixator. Specimens were analyzed by computed tomography (CT). Primary outcome was accessible DSA. Student t tests compared DSA accessed by different exposure methods. RESULTS: An initial mPM approach exposed 25.6% and 33.6% of DSA without and with distraction (P = .002). An initial ATL approach accessed 47.0% and 58.1% of DSA without and with distraction, respectively (P = .003). Accessibility via dual approaches was 71.7% and 93% of DSA without and with distraction with an initial ATL approach and 71.3% and 87.5% of DSA without and with distraction with an initial mPM approach (P = .96 and .37, respectively). The central talar dome was inaccessible in an almond-shaped area, tapered at the medial and lateral ends. Anterior, lateral, and posterior articular margins were able to be fully exposed, often with overlapping exposure between posterior and anterior approaches, with distraction reliably improving lateral visualization. CONCLUSION: Dual approaches provided access to greater than 70% and 85% of talar DSA without and with distraction, respectively. Order of approach did not significantly affect exposure and thus should be determined by surgeon discretion. These results may promote soft tissue-only treatment strategies in talar body fracture care with an extensile exposure of the talar dome surface. Careful preoperative planning optimizes the advantages of this approach. LEVEL OF EVIDENCE: Level IV, case series.

Total Ankle Replacement Provides Symmetrical Postoperative Kinematics: A Biplane Fluoroscopy Imaging Study.

BACKGROUND: In vivo measurements of tibiotalar and subtalar joint motion following TAR are unavailable. Using biplane fluoroscopy, we tested the hypothesis that the prosthetic tibiotalar joint and adjacent subtalar joint would demonstrate kinematic and range of motion differences compared to the contralateral untreated limb, and control participants. METHODS: Six patients of 41 identified candidates that all underwent unilateral Zimmer TAR (5.4 ± 1.9 years prior) and 6 control participants were imaged with biplane fluoroscopy during overground walking and a double heel-rise activity. Computed tomography scans were acquired; images were segmented and processed to serve as input for model-based tracking of the biplane fluoroscopy data. Measurements included tibiotalar and subtalar kinematics for the TAR, untreated contralateral, and control limbs. Statistical parametric mapping quantified differences in kinematics throughout overground walking and the double heel-rise activity. RESULTS: Patients with this TAR performed walking and heel-rise activities symmetrically with no significant kinematic differences at the tibiotalar and subtalar joints between limbs. Compared to control participants, patients exhibited reduced dorsi/plantarflexion range of motion that corresponded to decreased peak dorsiflexion, but only in the late stance phase of walking. This reduction in tibiotalar dorsi/plantarflexion range of motion in the TAR group became more apparent with double heel-rise activity. CONCLUSION: Patients with a Zimmer TAR had symmetric kinematics during activities of walking and double heel-rise, but they did exhibit minor compensations in tibiotalar kinematics as compared to controls. CLINICAL RELEVANCE: The lack of significant kinematic compensation at the subtalar joint may explain why secondary subtalar osteoarthritis is reported as being relatively uncommon in patients with some TAR designs.

Interaction of loading and ligament injuries in subtalar joint instability quantified by 3D weightbearing computed tomography.

Despite decades of research since its first description, subtalar joint instability remains a diagnostic enigma within the concept of hindfoot instability. This could be attributed to current imaging techniques, which are impeded by two-dimensional measurements. Therefore, we used weightbearing computed tomography imaging to quantify three-dimensional displacement associated with subtalar joint instability. Three-dimensional models were generated in seven paired cadaver specimens to compute talocalcaneal displacement after different patterns of axial load (85 kg) combined with torque in internal and external rotation (10 Nm). Sequential imaging was repeated in the subtalar joint containing intact ligaments to determine reference displacement. Afterward, the interosseus talocalcaneal ligament (ITCL) or calcaneofibular ligament (CFL) was sectioned, then the ITCL with CFL and after the ITCL, CFL with the deltoid ligament (DL). The highest translation could be detected in the dorsal direction and the highest rotation occurred in the internal direction when external torque was applied to the foot without load. These displacements differed significantly from the condition containing intact ligaments, with a mean difference of 1.6 mm (95% CI, 1.3 to 1.9) for dorsal translation and a mean of 12.4° (95% CI, 10.1 to 14.8) for internal rotation. Clinical relevance: Our study provides a novel and noninvasive analysis to quantify subtalar joint instability based on three-dimensional WBCT imaging. This approach overcomes former studies using trans-osseous fixation to determine three-dimensional subtalar joint displacement and implements an imaging device and software modalities that are readily available. Based on our findings, we recommend applying torque in external rotation to the foot to optimize the detection of subtalar joint instability.

Micro-CT analysis of the Lisfranc complex reveals higher bone mineral density in dorsal compared to plantar regions.

Injuries to the Lisfranc complex may require surgical fixation, the stability of which may be correlated with bone mineral density (BMD). However, there is limited research on regional BMD variations in the Lisfranc complex. This study used quantitative micro-CT to characterize regional BMD in the four bones (medial cuneiform, intermediate cuneiform, first metatarsal, and second metatarsal) of this complex. Twenty-four cadaveric specimens were imaged with a calibration phantom using micro-CT. Each bone was segmented and divided into eight regions based on an anatomical coordinate system. BMD for each octant was calculated using scan-specific calibration equations and average image intensity. Differences between regions were analyzed using ANOVA with post hoc analysis and differences between groups of four octants in each plane were analyzed with t-tests with significance level α = 0.05. The highest density region in the medial cuneiform was the distal-dorsal-lateral and dorsal regions showed significantly higher BMD than plantar regions. The intermediate cuneiform had the highest density in the distal-dorsal-medial region and the dorsal and medial regions had higher BMD than the plantar and lateral regions, respectively. The densest region of the first metatarsal was the distal-dorsal-lateral and distal regions had significantly higher BMD than proximal regions. In the second metatarsal, the distal-dorsal-medial region had the highest density, and the distal, dorsal, and medial regions had significantly higher BMD than the proximal, plantar, and lateral regions, respectively. The predominant finding was a pattern of increased density in the dorsal bone regions, which may be relevant in the surgical management of Lisfranc injuries.

Talar Dome Access Through Posteromedial Surgical Intervals for Fracture Care.

BACKGROUND: Posterior talar body fractures are rare injuries without a consensus surgical approach. This study evaluates the accessible area of the talar dome through 2 posteromedial approach intervals (posteromedial [PM] and modified posteromedial [mPM]) both with and without distraction. METHODS: Ten male cadaveric legs (5 matched pairs) were included. A PM approach, between flexor hallucis longus (FHL) and the tibial neurovascular bundle, and an mPM approach, between FHL and Achilles tendon, was performed on each pair. In total, 4 mm of distraction across the tibiotalar joint was applied with the foot held in neutral position. Accessible dome surface area (DSA) was outlined by drilling with a 1.6-mm Kirschner wire with and without distraction. Specimens were explanted and analyzed by micro-computed tomography with 3-dimensional reconstruction. Primary outcomes were total accessible DSA and sagittal plane access at predetermined intervals. RESULTS: The PM approach allowed access to 19.1% of the talar DSA without distraction and 33.1% of the talar dome with distraction (P < .001). The mPM approach provided access to 20.4% and 35.6% of the talar DSA without and with distraction (P < .001). Both approaches demonstrated similar sagittal plane access at all intervals except the lateral border of the talus, where the mPM approach provided greater access both without distraction (20.5% vs 4.38%, P = .002) and with distraction (34.3% vs 17.8%, P = .02). CONCLUSION: The mPM approach, using an interval between FHL and Achilles tendon, provides similar access to the posterior surface of talar dome and better sagittal plane access to the most lateral portion of the dome. The mPM interval provides the advantage of avoiding direct dissection of the tibial nerve or posterior tibial artery. Using an external fixator for distraction can improve talar dome visualization substantially. LEVEL OF EVIDENCE: Level V, Cadaveric Study.

Mechanics and energetics of human feet: a contemporary perspective for understanding mobility impairments in older adults.

Much of our current understanding of age-related declines in mobility has been aided by decades of investigations on the role of muscle-tendon units spanning major lower extremity joints (e.g., hip, knee and ankle) for powering locomotion. Yet, mechanical contributions from foot structures are often neglected. This is despite the emerging evidence for their critical importance in youthful locomotion. With rapid growth in the field of human foot biomechanics over the last decade, our theoretical knowledge of young asymptomatic feet has transformed, from long-held views of a stiff lever and a shock-absorber to a versatile system that can modulate mechanical power and energy output to accommodate various locomotor task demands. In this perspective review, we predict that the next set of impactful discoveries related to locomotion in older adults will emerge by integrating the novel tools and approaches that are currently transforming the field of human foot biomechanics. By illuminating the functions of feet in older adults, we envision that future investigations will refine our mechanistic understanding of mobility deficits affecting our aging population, which may ultimately inspire targeted interventions to rejuvenate the mechanics and energetics of locomotion.

Statistical shape modeling of the talocrural joint using a hybrid multi-articulation joint approach.

Historically, conventional radiographs have been the primary tool to morphometrically evaluate the talocrural joint, which is comprised of the distal tibia, distal fibula, and proximal talus. More recently, high-resolution volumetric imaging, including computed tomography (CT), has enabled the generation of three-dimensional (3D) reconstructions of the talocrural joint. Weightbearing cone-beam CT (WBCT) technology provides additional benefit to assess 3D spatial relationships and joint congruency while the patient is load bearing. In this study we applied statistical shape modeling, a computational morphometrics technique, to objectively quantify anatomical variation, joint level coverage, joint space distance, and congruency at the talocrural joint. Shape models were developed from segmented WBCT images and included the distal tibia, distal fibula, and full talus. Key anatomical variation across subjects included the fibular notch on the tibia, talar trochlea sagittal plane rate of curvature, tibial plafond curvature with medial malleolus prominence, and changes in the fibular shaft diameter. The shape analysis also revealed a highly congruent talocrural joint with minimal inter-individual morphometric differences at the articular regions. These data are helpful to improve understanding of ankle joint pathologies and to guide refinement of operative treatments.

Assignment of local coordinate systems and methods to calculate tibiotalar and subtalar kinematics: A systematic review.

The introduction of biplane fluoroscopy has created the ability to evaluate in vivo motion, enabling six degree-of-freedom measurement of the tibiotalar and subtalar joints. Although the International Society of Biomechanics defines a standard method of assigning local coordinate systems for the ankle joint complex, standards for the tibiotalar and subtalar joints are lacking. The objective of this systematic review was to summarize and appraise the existing literature that (1) defined coordinate systems for the tibia, talus, and/or calcaneus or (2) assigned kinematic definitions for the tibiotalar and/or subtalar joints. A systematic literature search was developed with search results limited to English Language from 2006 through 2020. Articles were screened by two independent reviewers based on title and abstract. Methodological quality was evaluated using a modified assessment tool. Following screening, 52 articles were identified as having met inclusion criteria. Methodological assessment of these articles varied in quality from 61 to 97. Included articles adopted primary methods for defining coordinate systems that included: (1) anatomical coordinate system (ACS) based on individual bone landmarks and/or geometric shapes, (2) orthogonal principal axes, and (3) interactive closest point (ICP) registration. Common methods for calculating kinematics included: (1) joint coordinate system (JCS) to calculate rotation and translation, (2) Cardan/Euler sequences, and (3) inclination and deviation angles for helical angles. The methods each have strengths and weaknesses. This summarized knowledge should provide the basis for the foot and ankle biomechanics community to create an accepted standard for calculating and reporting tibiotalar and subtalar kinematics.

Mapping of Posterior Talar Dome Access Through Posteromedial Versus Posterolateral Approaches.

OBJECTIVE: To evaluate the accessible area of the talar dome through 2 standard posterior approaches [posteromedial (PM) and posterolateral (PL)] with and without distraction. METHODS: A standard PM or PL approach was performed with and without external fixator distraction on 12 through-knee cadaveric legs (6 matched pairs). The accessible area of the talar dome was outlined and imaged in a microcomputed tomography scanner to achieve 3D reconstructions of the accessible surface area. The study outcomes were accessible surface area of the talar dome in (1) total surface area and (2) sagittal plane distance of the talar dome at predetermined intervals. RESULTS: The PM approach provided significantly more access to the talar dome than did the PL approach both with and without distraction (P < 0.001). The PM approach allowed access to 15.8% (SD = 4.7) of the talar dome without distraction and 26.4% (SD = 8.0, P < 0.001) of the talar dome with distraction. The PL approach provided access to 6.69% (SD = 2.69, P = 0.006 compared with PM) and 14.6% (SD = 6.24, P = 0.006 compared with PM) of the talar dome surface area without and with distraction. At the difficult to access posterocentral region (L50) of the talus, the PM approach without and with distraction allowed 26.7% (SD = 4.1) and 38.6% (SD = 5.6, P < 0.001) sagittal plane access compared with 18.7% (SD = 5.61, P = 0.03) and 27.5% (SD = 7.11, P = 0.003) through a PL approach. CONCLUSION: The PM approach provides greater access to the posterocentral and PM talus. Using an external fixator for distraction can improve intraoperative visualization by at least 40%. This study provides a roadmap that can help guide talar dome surgical access for treatment of posterior talus fractures and help determine when an approach that includes an osteotomy can be avoided.

Anatomy and biomechanics of the Lisfranc ligamentous complex: A systematic literature review.

Lisfranc injuries are challenging to treat and can have a detrimental effect on active individuals. Over the past decade researchers have investigated methods for the reconstruction of the Lisfranc ligamentous complex (LLC) to preserve its functional stability and mobility. To aid in this innovation, this study presents the current understanding of the anatomical and biomechanical characteristics of the LLC through a systematic review. Three medical databases (PubMed, Scopus, and Embase) were searched from inception through July 2019. Original studies investigating the anatomy and/or biomechanical properties of the LLC were considered for inclusion. Data recorded from each study included: number of cadavers, number of feet, gender, laterality, age, type of specimen, measurement methods, reported ligamentous bundles, ligament origins and insertions, geometric characteristics, and biomechanical properties of the LLC. The Quality Appraisal for Cadaveric Studies (QUACS) scale was used to assess the methodologic quality of included articles. Eight cadaveric studies investigating the LLC were included out of 1204 screened articles. Most articles described the LLC as three distinct structures: the dorsal- (DLL), interosseous- (ILL), and plantar- (PLL) Lisfranc Ligaments. The ILL had the largest thickness and insertional area of osseous attachment. Biomechanically, the ILL also had the highest stiffness and resistance to load prior to failure when loaded parallel to its fiber orientation. Current knowledge of the anatomical and biomechanical properties of the LLC are presented and highlight its significant role of stabilizing the tarsometatarsal articulation. Appreciating the biomechanical characteristics of the ILL may improve clinical insight in managing LLC injuries.