Flatfoot Model Research Articles

The reliability of talonavicular uncoverage to indicate forefoot abduction in progressive collapsing foot deformity: a finite element analysis

BackgroundProgressive Collapsing Foot Deformity (PCFD) presents various deformities. While medializing displacement calcaneal osteotomy (MDCO) and lateral column lengthening (LCL) are commonly employed as corrective surgeries, their impact on foot structure and functionality necessitates detailed biomechanical analysis. The objective of this study is to analyze the reliability of using talonavicular uncoverage percentage (TUP) as a metric for assessing the degree of forefoot abduction.MethodsSeven subject-specific flatfoot models were constructed based on previous study. Finite element analysis was conducted to simulate stress distribution and contact characteristics in PCFD. Models were categorized based on TUP values, and MDCO was performed to analyze stress changes in the medial longitudinal arch and contact characteristics of subtalar joint.ResultsThe study revealed discrepancies in TUP measurements between plain radiographs and three-dimensional models. Comparative analysis of the seven models showed that TUP exceeding 40% showed varied stress responses. A newly introduced parameter, the distance from the center of the head of the second metatarsal to the talar body axis (DSMT), demonstrated potential as a more dependable indicator. Models with DSMT below 20 mm experienced a remarkable reduction in ligamentous stress and notable change in region of stress concentration on the subtalar joint surface after MDCO, while those above 20 mm showed no noteworthy change.ConclusionThe study suggests that TUP may not be a reliable indicator for LCL surgery in PCFD, highlighting the need for improved assessment parameters. DSMT shows promise as a more dependable indicator, warranting further research to validate its efficacy. Enhanced indicators will facilitate better surgical planning in PCFD corrective procedures.Clinical relevanceAccurate assessment of flatfoot deformities is crucial for developing effective treatments. DSMT , which utilizes the talar body axis as a reference, is not affected by anatomical variations in the talar head body angle, rendering it more reliable for assessment of forefoot abduc tion. Improved indicators will contribute to better surgical decision making and patient outcomes in PCFD.

Validation of patient-specific flatfoot models on finite element analysis

Adult-acquired flatfoot causes various deformities. If a patient-specific foot model can be created using the finite element method, it can be used to study the appropriate surgical technique for each patient. Nine patient-specific flatfoot models were created, and loading simulations were performed. To validate the models, the patients’ weight-bearing radiographs were compared with the parameters of the models. The CCC values ranged from 0.917 to 0.993 , all exceeding the moderate threshold according to the McBride criteria. Our model reproduces the biomechanics of a patient’s foot under loading conditions, which may be useful for investigating patient-specific surgical procedures.

An ex vivo sequential ligament transection model of flatfoot

BackgroundThe ligaments implicated in the earliest stages of developing a progressive collapsing foot deformity are poorly understood. Commonly employed cadaveric flatfoot models are created from simultaneous transection of multiple ligaments, making it difficult to assess early changes in pressure distribution from ligaments critical for maintaining load distribution. A serial transection of ligaments may provide insight into changes in pressure distribution under the foot to identify a potential combination of ligaments that may be involved in early deformities. MethodsSpecimens were loaded using a custom designed axial and tendon loading system. Plantar pressure data for the forefoot and hindfoot were recorded before and after six sequential ligament complex transections. FindingsSectioning the plantar fascia (first) and short/long plantar ligaments (second) failed to generate appreciable differences in load distribution. Dividing the spring ligament (third) led to changes in hindfoot load distribution with a shift towards the lateral column indicative of hindfoot valgus angulation. All subsequent conditions resulted in similar patterns in hindfoot plantar load distribution. An anterior shift in the center of pressure only occurred after transection of all six ligament complexes. InterpretationLoss of the plantar fascia and short/long plantar ligaments are not critical in maintaining plantar load distribution or contact area. However, the additional loss of the spring ligament caused notable changes in hindfoot load distribution, indicating the combination of these three ligament complexes is particularly critical for preventing peritalar subluxation. Minimal changes in load distribution occurred when performing additional transections to reach a complete flatfoot deformity.

Biomechanical Effects of Subtalar Joint Fusion and Medial Ligament Reconstruction in Simulated Progressive Collapsing Foot Deformity.

The purpose of this study is to investigate the biomechanical effect of medial displacement calcaneal osteotomy (MDCO), subtalar joint fusion (SF), and medial ligament reconstruction (MLR: deltoid-spring ligament) in a severe flatfoot model. We hypothesized that (1) combination of MDCO and SF improves the tibiotalar and foot alignment in severe progressive collapsing foot deformity (PCFD) cadaver model. (2) However, if a residual valgus heel alignment remains after MCDO and SF, it can lead to increased medial ligament strain, foot malalignment, and tibiotalar valgus tilt, which will be mitigated by the addition of MLR. Ten fresh-frozen cadaveric foot specimens were used to create a severe flatfoot model. The foot alignment changes, including the talo-first metatarsal angle in the axial and sagittal planes, subtalar angle, and tibiotalar angle in the coronal plane, were measured. The angles were measured at the initial condition, after creating the severe flatfoot model, and after each successive reconstructive procedure in the following order: (1) MDCO, (2) SF, and (3) MLR. Tibiotalar valgus tilt was decreased with the MDCO procedure: 4.4 vs 1.0 degrees (P = .04). Adding in situ SF to the MDCO led to increased tibiotalar tilt to 2.5 degrees was different from the initial condition (P = .01). Although the tibiotalar valgus tilt was significantly decreased after adding the MLR to the MDCO/SF procedure compared with the severe flatfoot model (0.8 vs 4.4 degrees, P = .03), no significant difference in the tibiotalar valgus tilt was observed between MDCO/SF and MDCO/SF with MLR. Our results demonstrated that MDCO significantly improved forefoot abduction and medial arch alignment, with no significant additional improvement observed with addition of SF. Following SF, a residual valgus heel alignment can contribute to subsequent tibiotalar valgus tilt. The addition of MLR did not show significantly decreased tibiotalar valgus tilt following SF. Residual valgus heel alignment after subtalar joint fusion in the surgical treatment of PCFD can lead to increased medial ligament strain. Although MLR might be considered for providing medial stability, it may not necessarily prevent the development of tibiotalar valgus tilt.

The Role of the Plantar Fascia in Supporting the Arch in Flatfoot Deformity

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: The osseous structure of the foot has been described as an arch-like triangular structure or truss where the plantar fascia (PF) functions as the tensile element, maintaining the overall length of the arch. The importance of the PF in maintaining the arch has likely been underestimated because only minor abnormalities in its structure are seen on MRI studies in patients with flatfoot deformity. However, the importance of a ligament in preventing deformity may not be correlated with its attenuation seen on MRI. We hypothesized that the degenerative elongation of the plantar fascia would be a necessary precursor of arch collapse. The goal of this study was to evaluate the role of the plantar fascia in arch stability in flatfoot deformity. Methods: We used a validated finite element model of the foot reconstructed from CT scan of a female cadaveric foot weighing 60 kg. The model included 28 bones, 72 ligaments, cartilage, and an encapsulating soft tissue. The flatfoot model was created by simulated transection of the ligaments and unloading of the posterior tibial tendon. The model was used to assess the impact of isolated PF failure on the development of flatfoot deformity, evaluate the capability of the PF when reconstructed to restore foot alignment, and determine the amount of progressive strain that constitutes failure for each ligament. Foot alignment angles were used to evaluate the foot alignment. For comparison, the angles were also evaluated for other ligament tears. The impact of PF failure on force changes in the remaining ligaments was also investigated by quantifying ligament force changes during simulated PF cutting in the foot model. Results: When compared to the intact and flatfoot models, we found that the individual release of the PF cannot cause deformity (Figure 1). However, it significantly increased the force in the long (142%) and short plantar (156%), deltoid (45%), and spring ligaments (60%), potentially putting the foot at risk of arch instability over time. Moreover, we found that the PF was the structure most able to restore the arch (Figure 1a). The PF was also found to play a secondary role in reducing hindfoot valgus and forefoot abduction deformities (Figures 1b,1c). Moreover, to produce deformity, a considerable amount of attenuation in the spring (strain= 41%) and interosseous talocalcaneal ligament (strain= 27%), but only a small amount in the plantar fascia (strain= 10%) was needed. Conclusion: In comparing normal to flatfoot models of the foot, we found that isolated PF release did not cause arch collapse, but that arch collapse could not occur without elongation of the PF. While the progressive strain in the PF needed to enable arch collapse was small, the PF is a very long ligament, thus even small strain within the PF corresponds to substantial change in overall length of the arch. Chronic degeneration of the PF leading to plantar fasciitis may be an early sign of impending flatfoot deformity.

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.

A novel implantable mechanism-based tendon transfer surgery for adult acquired flatfoot deformity: Evaluating feasibility in biomechanical simulation.

Adult acquired flatfoot deformity becomes permanent with stage III posterior tibialis tendon dysfunction and results in foot pain and difficulty walking and balancing. To prevent progression to stage III posterior tibialis tendon dysfunction when conservative treatment fails, a flexor digitorum longus to posterior tibialis tendon transfer is often conducted. However, since the flexor digitorum longus only has one-third the force-capability of the posterior tibialis, an osteotomy is typically also required. We propose the use of a novel implantable mechanism to replace the direct attachment of the tendon transfer with a sliding pulley to amplify the force transferred from the donor flexor digitorum longus to the foot arch. In this work, we created four OpenSim models of an arched foot, a flatfoot, a flatfoot with traditional tendon transfer, and a flatfoot with implant-modified tendon transfer. Paired with these models, we developed a forward dynamic simulation of the stance phase of gait that reproduces the medial/lateral distribution of vertical ground reaction forces. The simulation couples the use of a fixed tibia, moving ground plane methodology with simultaneous activation of nine extrinsic lower limb muscles. The arched foot and flatfoot models produced vertical ground reaction forces with the characteristic double-peak profile of gait, and the medial/lateral distribution of these forces compared well with the literature. The flatfoot model with implant-modified tendon transfer produced a 94.2% restoration of the medial/lateral distribution of vertical ground reaction forces generated by our arched foot model, which also represents a 2.1X improvement upon our tendon transfer model. This result demonstrates the feasibility of a pulley-like implant to improve functional outcomes for surgical treatment of adult acquired flatfoot deformity with ideal biomechanics in simulation. The real-world efficacy and feasibility of such a device will require further exploration of factors such as surgical variability, soft tissue interactions and healing response.

The Effect of Progressive Lateral Column Lengthening in a Novel Stage II-B Flatfoot Cadaveric Model Evaluated Using Software-Guided Radiographic Measurements of Foot Alignment.

This work used software-guided radiographic measurement to assess the effects of progressive lateral column lengthening (LCL) on restoring alignment in a novel cadaveric model of stage II-B flatfoot deformity. A stage II-B flatfoot was created in 8 cadaveric specimens by transecting the spring ligament complex, anterior deltoid, and interosseous talocalcaneal and cervical ligaments. Weightbearing computed tomographic (WBCT) scans were performed with specimens under 450 N of compressive load in the intact, flat, and 6-, 8-, and 10-mm lateral column-lengthening conditions. Custom software-guided radiographic measurements of the lateral talo-first metatarsal (Meary) angle, anteroposterior talo-first metatarsal angle, naviculocuneiform overlap, and 2 new measures (plantar fascia [PF] distance and angle) were recorded on digitally reconstructed radiographs. Four anonymized analysts performed measurements twice. Intra- and interobserver agreement was assessed using intraclass correlation coefficients (ICCs). Six-millimeter LCL restored alignment closest to the intact foot in this new cadaveric model, whereas 10-mm lengthening tended toward overcorrection. The PF line displaced laterally in the flatfoot condition, and LCL restored the PF line to a location beneath the talonavicular joint. Interobserver agreement was excellent for PF distance (ICC = 0.99) and naviculocuboid overlap (ICC = 0.91), good for Meary angle (ICC = 0.81) and PF angle (ICC = 0.69), and acceptable for the talonavicular coverage angle (ICC = 0.65). In this stage II-B cadaveric flatfoot model, cervical ligament transection was essential to create deformity after the medial hindfoot ligaments were transected. Software-guided radiographic measurement proved reliable; standardized implementation should improve comparability between studies of flatfoot deformity. The novel PF distance performed most consistently (ICC = 0.99) and warrants further study. With this model, we found that a 6-mm LCL restored alignment closest to the intact foot, whereas 10-mm lengthening tended toward overcorrection. Future joint-sparing flatfoot corrections may consider using a relatively small LCL combined with other bony and/or anatomic ligament/tendon reconstructions.

Different Design Feature Combinations of Flatfoot Orthosis on Plantar Fascia Strain and Plantar Pressure: A Muscle-Driven Finite Element Analysis With Taguchi Method.

Customized foot orthosis is commonly used to modify foot posture and relieve foot pain for adult acquired flexible flatfoot. However, systematic investigation of the influence of foot orthotic design parameter combination on the internal foot mechanics remains scarce. This study aimed to investigate the biomechanical effects of different combinations of foot orthoses design features through a muscle-driven flatfoot finite element model. A flatfoot-orthosis finite element model was constructed by considering the three-dimensional geometry of plantar fascia. The plantar fascia model accounted for the interaction with the bulk soft tissue. The Taguchi approach was adopted to analyze the significance of four design factors combination (arch support height, medial posting inclination, heel cup height, and material stiffness). Predicted plantar pressure and plantar fascia strains in different design combinations at the midstance instant were reported. The results indicated that the foot orthosis with higher arch support (45.7%) and medial inclination angle (25.5%) effectively reduced peak plantar pressure. For the proximal plantar fascia strain, arch support (41.8%) and material stiffness (37%) were strong influencing factors. Specifically, higher arch support and softer material decreased the peak plantar fascia strain. The plantar pressure and plantar fascia loading were sensitive to the arch support feature. The proposed statistics-based finite element flatfoot model could assist the insole optimization and evaluation for individuals with flatfoot.

The Impact of Progressive Collapsing Foot Deformity on Foot &amp; Ankle Kinematics and Plantar Pressure During Simulated Gait

Category:Basic Sciences/Biologics; HindfootIntroduction/Purpose:Progressive collapsing foot deformity (PCFD) is a 3-dimensional pathology associated with insufficiency of the posterior tibial tendon (PTT), ligamentous failure, joint malalignment, and aberrant plantar force distribution. Existing knowledge of PCFD consists of static measurements, which provide information about the structure of the foot but none about its function. Cadaveric gait models provide an opportunity to measure motion both at the joints primarily affected in PCFD and the adjacent joints that are at risk for progressive subluxation and arthritis. This study sought to develop a flatfoot model for a robotic gait simulator and quantify gait kinematics and plantar pressure between normal and flatfoot conditions, which we hypothesized would be altered after the creation of a flatfoot deformity model.Methods:Cadaveric specimens were loaded on a 6-degree of freedom robotic gait simulator and the extrinsic tendons were attached to linear motors. Ground reaction forces and muscle forces were optimized utilizing an established iterative process. An 8-camera motion capture system was utilized to calculate joint kinematics using reflective markers attached by k-wires into bone. A plantar pressure mat attached to the force platform was used to calculate the center of pressure excursion index (CPEI) for each condition. The flatfoot model was created via sectioning of the spring ligament and medial talonavicular joint capsule followed by cyclic axial compression until 5-15° of talonavicular abduction was achieved in a static, loaded pose. Testing of the flatfoot state was then performed with inactivation of the PTT. Bias-corrected bootstrapped 95% confidence intervals were constructed from the repeated measures difference between flatfoot and normal conditions. Paired t-tests were used to compare the CPEI between conditions.Results:Twelve mid-tibia cadaveric specimens (mean age 73 years, 8 female) with no prior foot/ankle surgery were used. There were significant differences in kinematics between normal and PCFD conditions at the ankle, subtalar, and talonavicular joints (Figure). There was significantly increased ankle plantar flexion in flatfoot in the first 80% of stance phase. There was significantly greater subtalar eversion in flatfoot compared to normal from 10-90% of stance phase. Talonavicular abduction and eversion were also significantly greater in flatfoot from 10-100% of stance. The CPEI was significantly decreased in the flatfoot condition (Figure), indicating a medialization in center of pressure (p<0.0001).Conclusion:The results from this study support our hypothesis of altered kinematics and plantar pressure after flatfoot deformity creation and corroborate previous biomechanical studies of static alignment in PCFD. Increased talonavicular abduction and subtalar eversion are hallmarks of flatfoot deformity, and increased ankle plantarflexion may represent the plantarflexed position of the talus in PCFD. In addition, plantar pressure was significantly medialized with flatfoot deformity. These findings highlight the utility of the gait simulator as a tool for future study of PCFD, especially for analysis of deformity patterns and the specific effects of individual interventions.

Peritalar Kinematics Restored with Combined Subtalar Fusion and Medial Ligament Reconstruction in a Simulated Advance Progressive Collapsing Flatfoot Deformity Model

Category:Midfoot/Forefoot; OtherIntroduction/Purpose:Progressive collapsing flatfoot deformity (PCFD) leads to a disruption of the medial peritalar ligaments with progressive loss of the medial arch and further valgus alignment of the subtalar and tibiotalar joints. This ultimately leads to peritalar instability with subtalar and tibiotalar osteoarthritis. Conventional joint sparing reconstruction methods alone may not correct the valgus heel alignment. Some have suggested subtalar fusion (SF) with or without combined medializing calcaneal osteotomy (MCO) as an option. Although SF provides a more effective correction of hindfoot alignment, a resultant increase in valgus moment arm with a larger strain on the medial ankle ligament has been reported. The study aim is to investigate the efficacy of a combined MCO with SF and medial tibionavicular ligament (TNL) reconstruction on restoring peritalar stability.Methods:Ten fresh-frozen cadaveric foot specimens were employed to create a severe PCFD model. Reflective markers were placed on the tibia, talus, navicular, calcaneus, and first metatarsal. A multiple-camera motion capture system (OptiTrack, Prime13) was utilized to document peritalar joint kinematics. Severe AAFD model was created by sectioning the medial capsuloligamentous complex followed by cyclic axial loading. Sequential surgical procedures were performed, including MCO, SF, MCO + SF, and MCO + SF + medial tibionavicular ligament (TNL) reconstruction. Subtalar joint coronal angle, tibiotalar coronal angle, forefoot abduction axial angle, and talo-first metatarsus (Meary's) lateral angle were calculated for each sequential procedure and compared to the severe flatfoot model. The kinematic changes were calculated between groups utilizing a custom MatLab code and statistical significance was determined using a one-way ANOVA and a Tukey's multiple comparison test.Results:The subtalar joint valgus angle of the severe PCFD model (mean 8.1°) was significantly reduced by the MCO+SF+TNL reconstruction (mean 3.2°, p = 0.019). The tibiotalar joint valgus angle of the severe flatfoot model (mean 4.4°) was significantly reduced by the MCO (mean 1.0°, p = 0.04), but increased after combined MCO with SF (mean 2.5°, p = 0.01). The increased valgus tibiotalar angle of the MCO+SF was reduced by adding TNL reconstruction (mean 0.75°, p = 0.027). Forefoot abduction angle was found to be significantly reduced in all reconstruction methods compared to the severe flatfoot model. Meary's angle was also significantly improved after the MCO+SF and MCO+SF+TNL reconstruction (P= 0.015 and 0.006, respectively).Conclusion:Although addition of SF to MCO improved forefoot abduction and Meary's angles of advanced PCFD model, it resulted in increased tibiotalar valgus angle. The subsequent increase in medial ligament strain may be reduced by adding TNL reconstruction which can support medial stability while improve kinematics in all planes. Addition of TNL may be considered when performing SF for correction of PCFD, especially when a residual valgus heel alignment remains.

Surgical Reconstruction of Progressive Collapsing Foot Deformity Restores Kinematics during Simulated Level Walking

Category:Basic Sciences/Biologics; HindfootIntroduction/Purpose:Progressive collapsing foot deformity (PCFD) is a complex 3-dimensional pathology with a wide variety of surgical treatments. Regardless of technique, operative management of PCFD aims to restore normal foot architecture with attention to avoid the consequences of under- or over-correction. However, current methods of evaluating PCFD correction rely on static measurements, which do not assess dynamic function of the foot. Recent advances in robotic technology allow for the dynamic assessment of surgical correction of PCFD. This study sought to assess the effects of 2 osteotomies for PCFD, the medializing calcaneal osteotomy (MCO) and lateral column lengthening (LCL), on kinematics and plantar pressure during simulated gait. We hypothesized that the combination of LCL and MCO would restore joint kinematics and plantar pressure values to normal levels.Methods:Twelve cadaveric mid-tibia specimens (mean age 73 years, 8 female) were loaded on a 6-degree of freedom robotic gait simulator. Ground reaction forces and muscle forces were optimized utilizing an established iterative process. An 8-camera motion capture system was utilized to calculate joint kinematics using reflective markers attached by k-wires into bone. Plantar pressures were recorded using a pedography mat attached to the force platform. Testing was performed first in the native intact state, and again after creation of the flatfoot model. After flatfoot testing, surgical reconstruction and testing were performed in stages with MCO, and LCL with sequential 6mm and 8mm grafts. Bias-corrected bootstrapped 95% confidence intervals were calculated from the repeated measures difference between normal, flatfoot, post-MCO, post-MCO and post-reconstructive conditions. Center of plantar pressure excursion index (CPEI) was calculated and compared between conditions using a repeated measures ANOVA with Tukey post hoc analysis.Results:Overall, surgical correction restored kinematics to normal levels (Figure). MCO alone resulted in statistically significant improvement in subtalar eversion in the first 20% of stance, and post-MCO subtalar kinematics were statistically similar to normal. LCL (either 6mm and 8mm) alone did not significantly correct talonavicular abduction after PCFD. However, in conjunction with MCO, LCL was able to significantly correct talonavicular kinematics throughout the majority of stance phase, with kinematics statistically similar to normal levels. Each surgical step (LCL 6mm, LCL 8mm, MCO) resulted in sequential lateralization of the center of plantar pressure. At the culmination of surgical reconstruction (MCO + LCL), plantar pressure was significantly corrected compared to PCFD (P<0.0001). After surgical reconstruction, CPEI was slightly increased (lateralized) in comparison to normal, but was not significantly different from the normal state.Conclusion:The findings from this study support our hypothesis that surgical reconstruction of PCFD via MCO and LCL restores normal level walking kinematics. While the isolated effect of MCO and LCL resulted in significant changes in subtalar and talonavicular kinematics, the synergistic effect of combining MCO and LCL were most effective in restoring normal kinematics. However, lateralization of plantar pressure after combining MCO and LCL compared to the normal condition indicates the potential for overload of the lateral column, as described previously. Therefore, surgeons should be cautious in increasing osteotomy size at the lateral column to avoid overload.

Effects of extraosseous talotarsal stabilization on the biomechanics of flexible flatfoot subtalar joints in children: a finite element study

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Objective of the study was to generate an experimental foundation for the clinical application of extraosseous talotarsal stabilization (EOTTS) in treatment of flexible flatfeet in children by investigating the biomechanical characteristics of flexible flatfoot and the effects of EOTTS on hindfoot biomechanics.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; Three-dimensional finite element models of the foot and ankle complex were generated from computer tomography images of a volunteer’s left foot in three states: normal, flexible flatfoot, and post-EOTTS. After validation by X-ray, simulated loads were applied to the three models in a neutral position with both feet standing.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; In the flexible flatfoot model, the contact stress on the subtalar joint increased and contact areas decreased, resulting in abnormal stress distribution compared to the normal model. However, following treatment of the foot with EOTTS, these parameters returned to close to normal. Subtalar joint instability leads to a flexible flat foot. Based on this study, it is proposed that EOTTS can restore the normal function of the subtalar joint in and is an effective treatment for flexible flatfoot in children. We and many clinical data studies provide evidence for sinus tarsi implants in pediatric patients. It is showed that the formation of flexible flatfoot is induced by subtalar joint instability.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; Because of the EOTTS provides the best biomechanical solution to subtalar joint instability, the EOTTS became an effective form for subtalar joint instability treatment.&lt;/p&gt;

The role of medial ligaments and tibialis posterior in stabilising the medial longitudinal foot arch: a cadaveric gait simulator study

BackgroundDebate exists whether adult acquired flatfoot deformity develops secondary to tibialis posterior (TibPost) tendon insufficiency, failure of the ligamentous structures, or a combination of both. AimThe aim of this study is to determine the contribution of the different medial ligaments in the development of acquired flatfoot pathology. Also to standardise cadaveric flatfoot models for biomechanical research and orthopaedic training. MethodsFive cadaveric feet were tested on a dynamic gait simulator. Following tests on the intact foot, the medial ligaments – fascia plantaris (FP), the spring ligament complex (SLC) and interosseous talocalcaneal ligament (ITCL) – were sectioned sequentially. Joint kinematics were analysed for each condition, with and without force applied to TibPost. ResultsEliminating TibPost resulted in higher internal rotation of the calcaneus following the sectioning of FP and SLC (d>1.28, p = 0.08), while sectioning ITCL resulted in higher external rotation without TibPost (d = 1.24, p = 0.07). Sequential ligament sectioning induced increased flattening of Meary’s angle. ConclusionFunction of TibPost and medial ligaments is not mutually distinctive. The role of ITCL should not be neglected in flatfoot pathology; it is vital to section this ligament to develop flatfoot in cadaveric models.

Biomechanical comparison among five mid/hindfoot arthrodeses procedures in treating flatfoot using a musculoskeletal multibody driven finite element model

Background and objectiveMid/hindfoot arthrodesis could modify the misalignment of adult-acquired flatfoot and attenuate pain. However, the long-term biomechanical effects of these surgical procedures remain unclear, and the quantitative evidence is scarce. Therefore, we aimed to investigate and quantify the influences of five mid/hindfoot arthrodeses on the internal foot biomechanics during walking stance. MethodsA young participant with flexible flatfoot was recruited for this study. We reconstructed a subject-specific musculoskeletal multibody driven-finite element (FE) foot model based on the foot magnetic resonance imaging. The severe flatfoot model was developed from the flexible flatfoot through the attenuation of ligaments and the unloading of the posterior tibial muscle. The five mid/hindfoot arthrodeses simulations (subtalar, talonavicular, calcaneocuboid, double, and triple arthrodeses) and a control condition (no arthrodesis) were performed simultaneously in the detailed foot multibody dynamics model and FE model. Muscle forces calculated by a detailed multi-segment foot model and ground reaction force were used to drive the foot FE model. The internal foot loadings were compared among control and these arthrodeses conditions at the first and second vertical ground reaction force (VGRF) peak and VGRF valley instants. ResultsThe results indicated that the navicular heights in double and triple arthrodeses were higher than other surgical procedures, while the subtalar arthrodesis had the smallest values. Five mid/hindfoot arthrodeses reduced the peak plantar fascia stress compared to control. However, double and triple arthrodeses increased the peak medial cuneo-navicular joint contact pressures and peak foot pressures as well as the metatarsal bones stresses. ConclusionAlthough mid/hindfoot arthrodesis generally reduced the collapse of medial longitudinal arch and plantar fascia loading during the stance phase, the increased loading in the adjacent unfused joint and metatarsal bones for double and triple arthrodeses should be noted. These findings could account for some symptoms experienced by flatfoot patients after surgery, which may facilitate the optimization of surgical protocols.

Biomechanical assessment of two types and two different locations of subtalar arthroereisis implants for flexible flatfoot: A cadaveric study

BackgroundSubtalar arthroereisis refers to the implantation of a sinus tarsi implant for the treatment of flexible flatfoot. The purpose of this study was to compare the ability to correct the flatfoot deformity and contact pressure of the posterior subtalar joint between two types of self-locking wedge implants and between two different positions for the same device in a cadaveric flatfoot model. MethodsThe flatfoot model was created in ten cadaver feet through ligament sectioning and cyclic loading. Three kinds of arthroereisis procedures were evaluated: Talar-Fit (type I self-locking wedge implant) anchored in the sinus portion of the tarsal sinus (T-sinus group), Talar-Fit in the canalis portion (T-canalis group), and HyProCure (type II) in the canalis portion (H group). Corrective ability in the sagittal and transverse planes were measured with clinometers. Contact pressure was measured with pressure-sensitive films. FindingsT-canalis group provided more sagittal (mean difference for size 10 mm: 1.9°, P = 0.014; mean difference for size 11 mm: 3.1°, P = 0.037) and transverse (mean difference for size 8 mm: 1.8°, P = 0.049; mean difference for size 11 mm: 2.2°, P = 0.049) corrections than T-sinus group. The flattening process shifted the peak pressure of the posterior subtalar joint to the posteromedial side (P < 0.05) and arthroereisis helped the distribution of contact pressure restore uniformity (all P > 0.05). InterpretationA self-locking wedge implant inserted in the canalis portion of the tarsal sinus achieved better correction than an implant inserted in the sinus portion.

Biomechanical Evaluation of a Cadaveric Flatfoot Model and Lateral Column Lengthening Technique

Patients with adult acquired flatfoot have progressive worsening of bony alignment with many being unable to perform a heel rise. Following reconstruction, pathologic skeletal alignment is corrected and the ability to perform a heel rise is often restored. The purpose of this study was to evaluate the relationship between forefoot liftoff forces and skeletal alignment in a cadaveric flatfoot model by assessing the effect of sequential lengthening of the lateral column using an Evans-type calcaneal osteotomy. Bony alignment was measured in 8 cadaveric specimens with the use of a 3-dimensional digitizing system. Transection of the spring ligament, pie-crusting of the plantar fascia, and cyclic axial loading of the foot was performed to create an anatomic and functional flatfoot model. An Evans-type calcaneal osteotomy using 6, 8, 10, and 12 mm wedges was performed. Specimens were mounted to a custom jig that applies tensile loads to the Achilles, peroneus brevis, peroneus longus, and tibialis posterior tendons. Creation of a flatfoot reduced the lateral talo-first metatarsal angle (Meary's angle) by 13° (23.6° ± 2.8° vs 10.6° ± 3.8°, p < .05) and forefoot force by 7% (199.3 N ± 7.3 N vs 185.4 N ± 9 N, p < .05). Sequential lengthening of the lateral column restored skeletal alignment and force transfer to the forefoot (12 mm wedge: Meary's angle 22.7° ± 3.9°, liftoff force 206.8 N ± 7.5 N). The cadaveric flatfoot model demonstrated decreased forefoot forces that were restored with an Evans-type calcaneal osteotomy wedge. This highlights the importance of restoring skeletal alignment when correcting advanced adult acquired flatfoot.

Peritalar Kinematics With Combined Deltoid-Spring Ligament Reconstruction in Simulated Advanced Adult Acquired Flatfoot Deformity.

Adult acquired flatfoot deformity (AAFD) is a complex and progressive deformity involving the ligamentous structures of the medial peritalar joints. Recent anatomic studies demonstrated that the spring and deltoid ligaments form a greater medial ligament complex, the tibiocalcaneonavicular ligament (TCNL), which provides medial stability to the talonavicular, subtalar, and tibiotalar joints. The aim of this study was to assess the biomechanical effect of a spring ligament tear on the peritalar stability. The secondary aim was to assess the effect of TCNL reconstruction in restoration of peritalar stability in comparison with other medial stabilization procedures, anatomic spring or deltoid ligament reconstructions, in a cadaveric flatfoot model. Ten fresh-frozen cadaveric foot specimens were used. Reflective markers were mounted on the tibia, talus, navicular, calcaneus, and first metatarsal. Peritalar joint kinematics were captured by a multiple-camera motion capture system. Mild, moderate, and severe flatfoot models were created by sequential sectioning of medial capsuloligament complex followed by cyclic axial loading. Spring only, deltoid only, and combined deltoid-spring ligament (TCNL) reconstructions were performed. The relative kinematic changes were compared using 2-way analysis of variance (ANOVA). Compared with the initial condition, we noted significantly increased valgus alignment of the subtalar joint of 5.1 ± 2.3 degrees (P = .031) and 5.8 ± 2.7 degrees (P < .01) with increased size of the spring ligament tear to create moderate to severe flatfoot, respectively. We noted an increased tibiotalar valgus angle of 5.1 ± 2.0 degrees (P = .03) in the severe model. Although all medial ligament reconstruction methods were able to correct forefoot abduction, the TCNL reconstruction was able to correct both the subtalar and tibiotalar valgus deformity (P = .04 and P = .02, respectively). The TCNL complex provided stability to the talonavicular, subtalar, and tibiotalar joints. The combined deltoid-spring ligament (TCNL) reconstructions restored peritalar kinematics better than isolated spring or deltoid ligament reconstruction in the severe AAFD model. The combined deltoid-spring ligament (TCNL) reconstruction maybe considered in advanced AAFD with medial peritalar instability: stage IIB with a large spring ligament tear or stage IV.

Biomechanical Comparison of Hintermann and Evans Osteotomy for Lateral Column Lengthening

Category:Hindfoot, Midfoot/ForefootIntroduction/Purpose:Both Evans and Hintermann procedures are opening wedge calcaneal osteotomies used for lateral column lengthening in flatfoot reconstruction. Risks of lateral column lengthening include lateral forefoot overload and increased calcaneocuboid (CC) joint pressure. The Evans osteotomy is preformed closer to the CC joint increasing the theoretical risk of higher CC pressures. The Hintermann technique is a more posteriorly located osteotomy developed to avoid destabilization of the anterior calcaneal fragment and subsequent CC joint incongruency. The purpose of this study is to biomechanically compare the Evans and Hintermann osteotomies through analysis of CC joint pressures and forefoot plantar pressures after sequential lengthening of the lateral column.Methods:A flatfoot model with radiographic confirmation was created in 10 matched cadaveric specimens which were then randomly selected to undergo either the Evans or Hintermann osteotomy. Specimens were physiologically loaded and the peak pressure of the CC joint and forefoot plantar pressures were measured under the following conditions: (1) intact foot, (2) flatfoot, and (3) sequential lengthening of the lateral column from 6 mm to 14 mm, in 2 mm increments.Results:Lateral column lengthening lead to significantly increased pressure across the CC joint in both the Evans and Hintermann specimens. With increasing lateral column length, mean peak CC pressures ranged from 2.9–4.0 and 1.2–2.2 times intact CC pressure for the Evans and Hintermann group, respectively. Normalized mean and normalized peak CC pressures were significantly higher in the Evans osteotomy group compared to the Hintermann group at every level of distraction (see figure). The CC pressures under each testing condition were normalized with respect to the intact foot. Forefoot lateral plantar pressures were significantly increased in specimens corrected with Evans osteotomy at 10 mm and 12 mm of distraction compared to the intact foot.Conclusion:The Evans osteotomy lead to significantly higher CC pressures than the Hintermann osteotomy. This data suggests the Hintermann osteotomy for flatfoot reconstruction minimizes increase in CC joint pressures and could reduce the risk of subsequent CC osteoarthritis.

Investigation of Lateral Column Lengthening Osteotomy on the Movement of the Calcaneus: A Cadaveric Study

Category:HindfootIntroduction/Purpose:Lateral column lengthening calcaneus osteotomy has been used widely in treating Stage IIB flexible flatfoot deformity in order to shift the anterior segment of the calcaneus forwards, which improves the coverage of the talonavicular joint by forefoot adduction. The premise of this investigation is that in addition to shifting the forefoot anteriorly around the axis of the talar head, there is also a posterior translation of the tuberosity of the calcaneus which is detrimental in that the angle of Gissane then impinges upon the posterior facet of the subtalar joint causing pain. Our hypothesis is that in addition to anterior translation of the calcaneus, posterior shift of the calcaneal tuberosity occurs with lengthening osteotomy of the calcaneus.Methods:An acute cadaveric flatfoot model was created on 5 fresh frozen cadaver feet with no previous foot and ankle deformity. In order to simulate the surgical scenario, the study was performed with no external load on the limb. A vertical osteotomy was performed 1 cm posterior of the calcaneocuboid joint. Commercially available precut wedges of 6 mm, 8 mm, 10 mm, and 12 mm were used for lateral column lengthening. After the insertion of the bone grafts, positional changes in sagittal plane of both the anterior and posterior calcaneus segments were monitored on lateral views under both fluoroscopy and a 3D digital high-resolution motion capture system. Results were calculated in percentage change from the base line horizontal distance between the talar and both anterior and posterior calcaneus markers before insertion of the wedges.Results:According to fluoroscopic measurements, the anterior translation of the anterior calcaneus segment was 7.27%+/-0.06 for 6 mm wedge, 16.11%+/-0.06 for 8 mm wedge, 20.81%+/- 0.08 for 10 mm wedge and 18.16%+/-0.07 for 12 mm wedge. The posterior translation of the posterior calcaneus segment was 9.85%+/-0.09 for 6 mm wedge, 13.15%+/-0.09 for 8 mm wedge, 12.04+/-0.09 for 10 mm wedge, and 14.06%+/-0.10 for 12 mm wedge. Statistical analysis showed that: 6 mm wedges did not cause significant changes in the translation of both anterior and posterior calcaneus segments with respect to the talus. 8 mm, 10 mm and 12 mm wedges caused significant translations both anteriorly and posteriorly. There was no statistically significant difference in the amount of either anterior or posterior translation caused by 8 mm, 10 mm or 12 mm wedges. These results were corroborated by 3D measurements.Conclusion:Of interest is that a 6 mm graft did not cause any significant anterior or posterior shift of the calcaneus. Lateral column lengthening with the 8,10, and 12 mm grafts however caused forward shifting of the anterior calcaneus, but also statistically significant posterior translation of the tuberosity, causing impingement of the posterior facet which was visible in each cadaver tested. There was no statistical difference between the sizes of the wedge above 6 mm and the translations they caused either anteriorly or posteriorly. Surgeons should be aware of the potential for painful impingement with the lateral column lengthening osteotomy.