Biomechanical evaluation of tenodesis reconstruction in ankle with deltoid ligament deficiency: a finite element analysis

Investigation into the effect of deltoid ligament injury on rotational ankle instability using a three-dimensional ankle finite element model

Background

Injury to the lateral collateral ligament of the ankle may cause ankle instability and, when combined with deltoid ligament (DL) injury, may lead to a more complex situation known as rotational ankle instability (RAI). It is unclear how DL rupture interferes with the mechanical function of an ankle joint with RAI.

Purpose

To study the influence of DL injury on the biomechanical function of the ankle joint.

Methods

A comprehensive finite element model of an ankle joint, incorporating detailed ligaments, was developed from MRI scans of an adult female. A range of ligament injury scenarios were simulated in the ankle joint model, which was then subjected to a static standing load of 300 N and a 1.5 Nm internal and external rotation torque. The analysis focused on comparing the distribution and peak values of von Mises stress in the articular cartilages of both the tibia and talus and measuring the talus rotation angle and contact area of the talocrural joint.

Results

The dimensions and location of insertion points of ligaments in the finite element ankle model were adopted from previous anatomical research and dissection studies. The anterior drawer distance in the finite element model was within 6.5% of the anatomical range, and the talus tilt angle was within 3% of anatomical results. During static standing, a combined rupture of the anterior talofibular ligament (ATFL) and anterior tibiotalar ligament (ATTL) generates new stress concentrations on the talus cartilage, which markedly increases the joint contact area and stress on the cartilage. During static standing with external rotation, the anterior talofibular ligament and anterior tibiotalar ligament ruptured the ankle's rotational angle by 21.8% compared to an intact joint. In contrast, static standing with internal rotation led to a similar increase in stress and a nearly 2.5 times increase in the talus rotational angle.

Conclusion

Injury to the DL altered the stress distribution in the tibiotalar joint and increased the talus rotation angle when subjected to a rotational torque, which may increase the risk of RAI. When treating RAI, it is essential to address not only multi-band DL injuries but also single-band deep DL injuries, especially those affecting the ATTL.

Safe Talar Tunnel Placement During Reconstruction of the Deep Layer of the Deltoid Ligament: A Comparison of 4 Different Anatomic Landmarks on the Lateral Malleolus

Background

Deltoid ligament reconstruction of the ankle can be considered when the ruptured ligament is insufficient for direct repair.

Purpose

To compare the safety of talar tunnels oriented toward 4 different anatomic landmarks on the lateral malleolus during reconstruction of the deep layer of the deltoid ligament (DDL).

Study Design

Descriptive laboratory study.

Methods

A total of 30 computed tomography scans of the ankle joint in healthy adults were collected to generate 3-dimensional models. Virtual talar tunnels with a diameter of 5 mm and with different lengths (20.0, 25.0, and 30.0 mm) were created from the talar insertion of the DDL and were oriented toward the talar neck as well as the most anterior, the most distal, and the most posterior points of the distal fibula. The minimal safe distance (MSD) of a drilling route was calculated for the tunnels, and the safe distance from the end of the tunnel to the bone surface was measured for each tunnel. The nonpaired Student t test was used to detect differences among the safe distances of the 4 different bone tunnels.

Results

For the 20.0-mm tunnels, the safe distance of the tunnel oriented toward the talar neck (5.90 ± 1.16 mm) did not meet the MSD (6.0 mm). For the 25.0-mm tunnels, the safe distances of the tunnels oriented toward the talar neck (4.53 ± 1.13 mm) and the anterior point of the fibula (5.91 ± 1.52 mm) did not meet the MSD (6.9 mm).

Conclusion

Tunnels that were 5 mm in diameter and 20.0 and 25.0 mm in length, oriented toward the most distal or most posterior point of the distal fibula, were safe for DDL reconstruction.

Clinical Relevance

Knowledge of safe talar tunnel placement is important, especially to avoid bone surface penetration during DDL reconstruction.

Syndesmosis dislocation and ankle ligament stress in the posterior malleolus fracture fixated - "in vitro analysis"

PURPOSE

The objectives of this study were to compare syndesmosis dislocation and ankle ligament stress after the fixation of the posterior malleolus fracture (PMF) with four different techniques by Finite Element Analysis (FEM).

METHODS

Four internal fixation techniques used for fixation of PMF were assessed by FEM: posterior one-third tubular 3.5 mm buttress plate (PP) with one screw (PP 1 screw), PP with two screws (PP 2 screws), two cannulated 3.5 mm lag screws in the anteroposterior (AP) direction (AP lag screws), and two posteroanterior (PA) cannulated 3.5 mm lag screws (PA lag screws). PMF with 30% fragment size was simulated through computational processing reconstructed from computed tomography (CT). The simulated loads of 700 N and 1200 N were applied to the proximal tibial end. The FEM evaluated the syndesmosis dislocation (mm) and stress values of the posterior tibiofibular ligament (PTFL) (in Kpa) and deltoid ligament (in Kpa) in the four mentioned subgroups.

RESULTS

We found that with a load of 700 N, syndesmosis dislocation varied from 6.5 to 7.9 mm, being the lowest and greatest for PA lag screw and PP 1 screw, respectively. In all groups was observed a greater dislocation in the syndesmosis at 1200 N of load. We observed that the stress values on the PTFL were lower for AP lag screws and PP 2 screws with 700 N and 1200 N, respectively. For both loads, PP 1 screw presented the greatest stress. Regarding the stress in the deltoid ligament, the AP lag screws presented the lowest stress for 700 N and PP 1 screw for 1200 N. For all fixation techniques, the syndesmosis displacement and ligament stresses were higher when 1200 N were imposed.

CONCLUSION

This study demonstrated that PMF fixed with lag screws presents greater stability in the distal tibiofibular syndesmosis and higher joint loadings promoted greater displacement and ligaments stress, regardless of the fixation technique. Besides, lower stress in the syndesmosis is accompanied by a greater load on the deltoid ligament.

Clinically useful finite element models of the natural ankle - A review

BACKGROUND

Biomechanical simulation of the foot and ankle complex is a growing research area but compared to simulation of joints such as hip and knee, it has been under investigated and lacks consistency in research methodology. The methodology is variable, data is heterogenous and there are no clear output criteria. Therefore, it is very difficult to correlate clinically and draw meaningful inferences.

METHODS

The focus of this review is finite element simulation of the native ankle joint and we will explore: the different research questions asked, the model designs used, ways the model rigour has been ensured, the different output parameters of interest and the clinical impact and relevance of these studies.

FINDINGS

The 72 published studies explored in this review demonstrate wide variability in approach. Many studies demonstrated a preference for simplicity when representing different tissues, with the majority using linear isotropic material properties to represent the bone, cartilage and ligaments; this allows the models to be complex in another way such as to include more bones or complex loading. Most studies were validated against experimental or in vivo data, but a large proportion (40%) of studies were not validated at all, which is an area of concern.

INTERPRETATION

Finite element simulation of the ankle shows promise as a clinical tool for improving outcomes. Standardisation of model creation and standardisation of reporting would increase trust, and enable independent validation, through which successful clinical application of the research could be realised.

Disease-Specific Finite element Analysis of the Foot and Ankle

Finite-element analysis is a computational modeling technique that can be used to quantify parameters that are difficult or impossible to measure externally in a geometrically complex structure such as the foot and ankle. It has been used to improve our understanding of pathomechanics and to evaluate proposed treatments for several disorders, including progressive collapsing foot deformity, ankle arthritis, syndesmotic injury, ankle fracture, plantar fasciitis, diabetic foot ulceration, hallux valgus, and lesser toe deformities. Parameters calculated from finite-element models have been widely used to make predictions about their biomechanical correlates.

Length change pattern of the ankle deltoid ligament during physiological ankle motion

BACKGROUND

Length change pattern of the ankle deltoid ligament during physiological ankle motion is still confused currently and had not been studied in vivo.

METHODS

The deltoid ligaments from 7 cadaveric specimens were dissected. Lengths of each band during 30° plantarflexion to 20° dorsiflexion were measured. A dual fluoroscopy imaging system was utilized to capture the images of hindfoot joint of 7 healthy subjects during the stance phase of walking. 3D bone models were reconstructed from CT images. Lengths of each band were calculated after model-image registration utilizing a solid modeling software. Percentage of length variation and poses when the bands were in maximum extension were documented among each band.

RESULTS

The anterior border of tibiocalcaneal ligament (TCL) had only 1.7% length variation in vitro and 5.7% length variation in vivo. The tibionavicular ligament, tibiospring ligament, and deep anterior tibiotalar ligament were in maximum extension at 30° plantarflexion, however, superficial posterior tibiotalar ligament, deep posterior tibiotalar ligament, and the posterior border of TCL were in maximum extension at 20° dorsiflexion. The tibionavicular ligament, tibiospring ligament, and deep anterior tibiotalar ligament were in maximum extension during foot flat. The TCL was in maximum extension during midstance. The superficial posterior tibiotalar ligament and deep posterior tibiotalar ligament were in maximum extension during heel off and toe off.

CONCLUSION

The length of TCL did not change during ankle dorsiflexion and plantarflexion. The bands anterior to and posterior to the TCL showed different length change pattern during physiological ankle dorsiflexion and plantarflexion.

A Review of Finite Element Models of Ligaments in the Foot and Considerations for Practical Application

PURPOSE

Finite element (FE) modeling has been used as a research tool for investigating underlying ligaments biomechanics and orthopedic applications. However, FE models of the ligament in the foot have been developed with various configurations, mainly due to their complex 3D geometry, material properties, and boundary conditions. Therefore, the purpose of this review was to summarize the current state of finite element modeling approaches that have been used in the ?eld of ligament biomechanics, to discuss their applicability to foot ligament modeling in a practical setting, and also to acknowledge current limitations and challenges.

METHODS

A comprehensive literature search was performed. Each article was analyzed in terms of the methods used for: (a) ligament geometry, (b) material property, (c) boundary and loading condition related to its application, and (d) model verification and validation.

RESULTS

Of the reviewed studies, 80% of the studies used simplified representations of ligament geometry, the non-linear mechanical behavior of ligaments was taken into account in only 19.2% of the studies, 33% of included studies did not include any kind of validation of the FE model.

CONCLUSION

Further refinement in the functional modeling of ligaments, the micro-structure level characteristics, nonlinearity, and time-dependent response, may be warranted to ensure the predictive ability of the models.

Biomechanics of Medial Ankle and Peritalar Instability

The deltoid and spring ligaments are the primary restraints against pronation and valgus deformity of the foot, and in preserving the medial arch. The posterior tibial tendon has a secondary role in plantar arch maintenance, and its biomechanical stress increases considerably when other tissues fail. A thorough understanding of the anatomy and biomechanics of the deltoid-spring ligament is crucial for successful reconstruction of the tibiocalcanealnavicular ligament, hence, to restore ankle and medial peritalar stability. Although effective in correcting the deformity, tibionavicular tenodesis might be critical, as it blocks physiologic pronation of the hindfoot, which may result in dysfunction and pain.

Current Concepts in Treatment of Ligament Incompetence in the Acquired Flatfoot

Flatfoot deformity consists of a loss of medial arch, hindfoot valgus, and forefoot abduction. Historically considered a posterior tendon insufficiency, multiple ligament damage and subsequent incompetence explain the different clinical presentations with varying degrees of deformity. When surgery is deemed necessary, depending on the apex of the deformity, skeletal and soft tissue procedures are considered to keep motion and restore function. Osteotomies are considered at every level where an apex of deformity is found. The recently designated tibiocalcaneonavicular ligament comprises the older superficial and deep deltoid and spring ligaments; its repair or reconstruction should be considered in most flatfoot cases.

Patient-specific instrument-assisted minimally invasive internal fixation of calcaneal fracture for rapid and accurate execution of a preoperative plan: A retrospective study

Background

Traditional methods for minimally invasive internal fixation (MIIF) of calcaneal fractures require extensive intraoperative fluoroscopy, and fracture recovery is usually not ideal. We developed a new surgical procedure using digital surgical simulation and constructed a patient-specific instrument (PSI) for calcaneal fracture that we used during the operation. This study investigated whether PSI-assisted MIIF of calcaneal fracture enables rapid and accurate execution of the preoperative plan.

Methods

We retrospectively analyzed patients with Sanders type III or IV fresh calcaneal fractures who had undergone PSI-assisted MIIF at our hospital from January 2016 to December 2018. We analyzed perioperative data including intraoperative fluoroscopy time, concurrence of internal fixation actual usage (IFAU) with the preoperative plan, surgery time, and complications. We also compared pre- and postoperative actual measurements from X-ray radiographs and computed tomography images including Böhler, Gissane, and calcaneus valgus angles; subtalar joint width; and calcaneal volume overlap ratio with the preoperative design. All patients had been followed up and their American Orthopedic Foot and Ankle Score (AOFAS) score was available.

Results

Mean intraoperative fluoroscopy time was 3.95 ± 1.78 h; IFAU in 16 patients (16 ft) was the same as the preoperative plan; mean surgery time was 28.16 ± 10.70 min; and none of the patients developed complications. Böhler, Gissane, and calcaneus valgus angles and subtalar joint width did not differ between pre- and postoperative plans; however, the actual preoperative values of each of these parameters differed significantly from those measured postoperatively. The calcaneal volume overlap ratio with the preoperative design was 91.2% ± 2.3%. AOFAS scores increased with time, with significant differences in the score at each time point.

Conclusions

The newly developed PSI-assisted calcaneal fracture MIIF method can rapidly and accurately execute the preoperative plan.

Identification of Surgical Plan for Syndesmotic Fixation Procedure Based on Finite Element Method

Syndesmosis injuries account for approximately 20% of ankle fractures that require surgery. Although multiple surgical options are available, all of them are based on metal screws. Serious complications that arise when applying metal screws include screw loosening or breakage. To prevent such complications, we applied a simulation method using a finite element (FE) analysis. We created a 3D FE model of an ankle joint and conducted an FE analysis focusing on syndesmosis in terms of the level, material, and diameter of the syndesmotic screw and the number of penetrated cortical bones. The magnitude and direction of the force applied to the tibia in the midstance state were considered for simulating the model. The maximum von-Mises stress and syndesmosis widening were analyzed in terms of different biomechanical parameters. We identified the characteristics of the most biomechanically stable syndesmotic screw and its fixation point on the basis of the two parameters. We demonstrated that the ideal syndesmotic screw fixation should be fixed at a level 20 to 25 mm above the ankle using a 4.5 mm titanium screw.

Arthroscopic ankle fusion only has a limited advantage over the open operation if osseous operation type is the same: a retrospective comparative study

Background

A great deal of research suggests that arthroscopic ankle fusion (AAF) has advantages over open ankle fusion (OAF), but these outcomes would be imprecise because of a selection bias. The purpose of this study is to verify which is better for ankle fusion, AAF or OAF. We regrouped the OAF group into two subgroups according to whether the osseous operation type is the same as AAF group. The goal is to minimize the impact of disease severity, thereby reducing selection bias to some extent.

Methods

We retrospectively analyzed the data of ankle fusion in our hospital between July 2015 and October 2018. Forty-three patients were enrolled and divided into AAF group (n = 17) and OAF group (n = 26). In order to eliminate selection bias, we divided OAF group into complex osseous operation subgroup (COO subgroup) (n = 15) and simple osseous operation subgroup (SOO subgroup) (n = 11). The osseous operation type of SOO subgroup is the same as AAF group. Then, we compared the differences between these groups. All patients were followed up at least 1 year after operation. We analyzed data, including etiology composition, surgical time, intra-op blood loss, reduction of albumin, total hospital stays, union time, fusion situation, complications, radiological examination, functional score, and questionnaire survey. Then we performed statistical analyses.

Results

We found that the etiological components of AAF group and OAF group were different; the etiological components of AAF group and SOO subgroup were similar. We found that AAF group has advantages over OAF group and COO subgroup in general. However, except in terms of surgical trauma, hospital stays, and short-term complications occurred, the AAF group has not obvious advantages over SOO subgroup, including intra-op blood loss, fusion condition, postoperative function score, and postoperative patient satisfaction; and AAF group need more surgical time than the SOO subgroup.

Conclusions

The arthroscopic ankle fusion can bring a good curative effect; however, if the osseous operation type is the same, the arthroscopic ankle fusion only has a limited advantage over the traditional open operation in perioperative soft tissue protection and enhanced recovery after surgery.

Nonanatomic versus anatomic techniques in spring ligament reconstruction: biomechanical assessment via a finite element model

Background

Several approaches to spring ligament reconstruction have been reported. However, a comparative study of nonanatomic and anatomic techniques with respect to biomechanical responses, such as kinematics and contact characteristics, has not been previously performed via a finite element analysis. The purpose of this study was to evaluate the biomechanical results of such spring ligament reconstructions via a finite element analysis.

Methods

A three-dimensional finite element model of the foot was developed and validated, and four reconstruction methods were simulated. The talonavicular dorsiflexion and abduction, hindfoot valgus, and contact characteristics in the Chopart joints were quantified in each model.

Results

Nonanatomic reconstructions corrected the talonavicular and hindfoot deformities to a greater extent than the anatomic reconstructions. The anatomic techniques also corrected the abduction and dorsiflexion deformities, although they presented insufficient power to correct for hindfoot valgus. None of the procedures restored the contact characteristics of the talonavicular and calcaneocuboid joints to those of a normal condition.

Conclusion

Nonanatomic reconstruction of the spring ligament complex provided the greatest correction for midfoot and hindfoot misalignments in flatfoot. Severe deformities with large amounts of midfoot pronation and hindfoot valgus may be better treated with nonanatomic reconstruction methods. The spring ligament reconstruction method may mitigate the need for nonanatomic bony procedures associated with complications and allows for the preservation of the triple joint complex.

Use of three-dimensional finite element models of the lateral ankle ligaments to evaluate three surgical techniques

Objective To compare three surgical techniques for lateral ankle ligament reconstruction using finite element (FE) models. Methods A three-dimensional FE model of the left foot of a healthy volunteer and lateral collateral ligament injury models were developed. Three tendons [one-half of the autologous peroneus longus tendon (PLT), one-half of the peroneus brevis tendon (PBT), and an allogeneic tendon] were used for lateral collateral ligament reconstruction. The ankle varus stress and anterior drawer tests were performed to compare the three surgical techniques. Results The ankle varus stress test showed that the equivalent stresses of the anterior talofibular ligament (ATFL) (84.00 MPa) and calcaneofibular ligament (CFL) (27.01 MPa) were lower in allogeneic tendon reconstruction than in the other two techniques but similar to those of normal individuals (138.48 and 25.90 MPa, respectively). The anterior drawer test showed that the equivalent stresses of the ATFL and CFL in autologous PLT reconstruction (31.31 and 28.60 MPa, respectively) and PBT reconstruction (31.47 and 29.07 MPa, respectively) were lower than those in allogeneic tendon reconstruction (57.32 and 52.20 MPa, respectively). Conclusions The allogeneic tendon reconstruction outcome was similar to normal individuals. Allogeneic tendon reconstruction may be superior for lateral ankle ligament reconstruction without considering its complications.

Analysis of 3-dimensional finite element after reconstruction of impaired ankle deltoid ligament

We compared four repair techniques for impaired ankle ligament deltoideum, namely Wiltberger, Deland, Kitaoka and Hintermann using a 3-dimensional finite element. We built an ankle ligament deltoideum model, including six pieces of bone structures, gristles and main ligaments around the ankle. After testing the model, we built an impaired ligament deltoideum model plus four reconstruction models. Subsequently, different levels of force on ankles with different flexion were imposed and ankle biomechanics were compared. In the course of bending, from plantar flexion 20° to back flexion 20°, the extortion of talus decreased while the eversion increased. Four reconstruction models failed to bring back the impaired ankle to normal, with an obvious increase of extortion and eversion. The Kitaoka technique was useful to reduce the extortion angle in a consequential manner. Compared with the other three techniques, the Kitaoka technique produced better results for extortion angle and the difference was statistically significant. However, in case of eversion, there was no significant difference among the four techniques (P>0.05). Lateral ligament's stress in all the four models was different from the normal one. When the ankle was imposed with extortion moment of force, stress of anterior talofibular ligament with the Kitaoka reconstruction method was close to that of the complete deltoid ligament. When ankle was imposed with eversion moment of force, stress of anterior talofibular ligament with Kitaoka and Deland reconstruction methods were close to that of the complete deltoid ligament. We concluded that Kitaoka and Deland tendon reconstruction technique could recover impaired ankle deltoid ligament and re-established its normal biomechanics characteristics.

Biomechanical evaluation of syndesmotic screw design via finite element analysis and Taguchi's method

BACKGROUND

Screw fixation of syndesmotic injuries facilitates ligament healing and restoration of ankle stability, but failure of the screw might threaten the success of the treatment. Screw design parameters, such as outer diameter, inner diameter, thread pitch, leading edge radius, trailing edge radius, leading edge angle, and trailing edge angle, might have effects on the stresses that occur in the screws. This is the first study, to our knowledge, to investigate which geometric screw parameters play key roles in stresses that occur in screws used for syndesmotic fixation.

METHODS

A three-dimensional finite element model of an ankle was reconstructed. Four different types of titanium screws—4.5-mm malleolar, 4-mm cancellous, 4-mm machine, and 3.5-mm cortical—were placed on this model. Physiologic load was applied to evaluate the stress in the screw. Then the contribution of each design factor to stress in the screws was analyzed systematically by Taguchi's robust design method.

RESULTS

The maximum equivalent ductile failure (von Mises equivalent stress) value was found in the 4-mm cancellous screw (402 MPa). Taguchi's analysis showed that the descending order of contribution of the design factors to stress emerging on the screw is inner diameter, leading edge angle, thread pitch, outer diameter, and trailing edge angle.

CONCLUSIONS

Stress that occurs in syndesmotic screws is closely related to their geometry and dimensions. According to the results, a 3.5-mm cortical screw with the ideal screw design regarding optimal parameters to resist against stresses in the syndesmosis seems more reasonable to choose in syndesmotic fixation.

Effects of inferior tibiofibular syndesmosis injury and screw stabilization on motion of the ankle: a finite element study

PURPOSE

Traditional studies of syndesmosis injury and screw stabilization have been conducted in cadaveric models, which cannot yield sufficient and exact biomechanical data about the interior of the ankle. The purpose of this study was to evaluate the effects of inferior tibiofibular syndesmosis injury (ITSI) and screw stabilization on the motion of the ankle with finite element analysis.

METHODS

Three-dimensional models of the ankle complex were created with CT images of a volunteer's right ankle in three states: normal, post-ITSI, and stabilization with a screw 2.5 cm above (parallel to) the ankle. Simulated loads were applied under three conditions: neutral position with single foot standing, internal rotation, and external rotation of the ankle.

RESULTS

Compared with the normal state, ITSI increased the relative displacement between the lower extremes of the tibia and fibula in the anteroposterior and mediolateral directions and the angular motion of the tibia, fibula, and talus at internal and external rotations (ERs). However, when stabilized with syndesmotic screws, the range of motion (ROM) and all these parameters significantly decreased.

CONCLUSION

ITSI can lead to internal and ER instability of the ankle joint. Screw stabilization is effective in controlling the instability, but may reduce markedly the ROM of the ankle joint. Through this study, it can be proposed that the screws should be removed once the healing is gained in order to restore normal function of the ankle joint as soon as possible.

Posterolateral ankle ligament injuries affect ankle stability: a finite element study

BACKGROUND

We have already discovered 23 patients during the work of the outpatient department and operations whose unstable signs on the posterolateral ankle. The anterior drawer test demonstrated normal during the physical examinations while the spaces of the posterior tibiotalar joints increased in stress X-ray plain films. ATFL intact and posterolateral ligaments lax were found during operations too. It is important to make existence claims and illuminate the mechanism of posterolateral ankle instability.

METHODS

A finite element model of the ankle was established for simulating to cut off posterolateral ligaments in turn. Ankle movements with tibia rotation under load on five forefoot positions were simulated as well.

RESULTS

The difference values with tibia external rotation were negative, and the positive results occurred with tibia internal rotation. The tibia-talus difference values in some forefoot positions were 2 ~ 3 mm after PTFL together with CFL or/and PITFL were cut off. The tibula-talus difference values were 2.21 ~ 2.76 mm after both PTFL and CFL were cut off. The tibia-fibula difference values were small. The difference values increased by 2 ~ 5 mm after cutting off the PITFL.

CONCLUSIONS

Posterolateral ankle ligaments, especially CFL and PITFL, play a significant role in maintaining ankle stability. The serious injuries of both CFL and PITFL would affect posterolateral ankle stabilities. PITFL was important to subtalar joint stability.

The role of the medial ligaments in lateral stabilization of the ankle joint: an in vitro study

PURPOSE

The deltoid ligament complex is known as medial stabilizer in the ankle against pronation/eversion. Lateral dual-ligament laxity often results in chronic ankle instability with recurring ankle sprain trauma. The goal of this study is to examine the lateral stabilizing role of the deltoid ligament complex against supination/inversion in case of existing lateral ligament instability.

METHODS

A torsion simulation was performed on 12 fresh human lower leg cadaver specimens in a loading frame and a specially designed mounting platform. The preset torsion between tibia and calcaneus was primarily set at 30° of internal rotation on specimen in plantar flexion and hindfoot inversion. The measured variable was the resisting torque recorded around mechanical tibial axis, which ensures stability in ankle sprain trauma. The first series of measurements were performed on healthy specimens and the following after transecting structures in following order: anterior talofibular ligament (ATFL) in combination with calcaneofibular ligament (CFL), followed by anterior tibiotalar ligament and posterior tibiotalar ligament and finally tibiocalcaneal ligament (TCL).

RESULTS

The combined lateral ATFL and CFL instability showed a decrease in the resisting torque, which ensures stability in ankle sprain trauma. Only a transection of TCL (superficial layer of deltoid ligament complex) with existing lateral dual-ligament instability results in a significant decrease in torque (p<0.0001).

CONCLUSION

The goal of the study was to provide the orthopaedic and/or trauma surgeon with quantitative data that may be referred to the substantial stabilizing effect of TCL against supination/inversion in the ankle joint in case of repetitive sprain trauma at a present lateral ligament lesion. Diagnostics of and treatment for lateral ligament instability need to consider the deltoid ligament complex,especially TCL in clinical routine.

Technical tips: reconstruction of deep and superficial deltoid ligaments by peroneus longus tendon in stage 4 posterior tibial tendon dysfunction

The deltoid ligament is composed of the superficial and deep layers. Disruption of the deltoid ligament can occur in rotational ankle fracture, chronic ankle instability, or stage 4 posterior tibial tendon dysfunction. Correcting valgus tilt at the time of flatfoot reconstruction in case of stage 4 posterior tibial tendon dysfunction may prevent future collapse and the need for ankle arthrodesis or possibly ankle arthroplasty. We describe a technique of reconstruction of both the superficial and deep deltoid ligaments by peroneus longus tendon.

The ligament anatomy of the deltoid complex of the ankle: a qualitative and quantitative anatomical study

BACKGROUND

The deltoid ligament has both superficial and deep layers and consists of up to six ligamentous bands. The prevalence of the individual bands is variable, and no consensus as to which bands are constant or variable exists. Although other studies have looked at the variance in the deltoid anatomy, none have quantified the distance to relevant osseous landmarks.

METHODS

The deltoid ligaments from fourteen non-paired, fresh-frozen cadaveric specimens were isolated and the ligamentous bands were identified. The lengths, footprint areas, orientations, and distances from relevant osseous landmarks were measured with a three-dimensional coordinate measurement device.

RESULTS

In all specimens, the tibionavicular, tibiospring, and deep posterior tibiotalar ligaments were identified. Three additional bands were variable in our specimen cohort: the tibiocalcaneal, superficial posterior tibiotalar, and deep anterior tibiotalar ligaments. The deep posterior tibiotalar ligament was the largest band of the deltoid ligament. The origins from the distal center of the intercollicular groove were 16.1 mm (95% confidence interval, 14.7 to 17.5 mm) for the tibionavicular ligament, 13.1 mm (95% confidence interval, 11.1 to 15.1 mm) for the tibiospring ligament, and 7.6 mm (95% confidence interval, 6.7 to 8.5 mm) for the deep posterior tibiotalar ligament. Relevant to other pertinent osseous landmarks, the tibionavicular ligament inserted at 9.7 mm (95% confidence interval, 8.4 to 11.0 mm) from the tuberosity of the navicular, the tibiospring inserted at 35% (95% confidence interval, 33.4% to 36.6%) of the spring ligament's posteroanterior distance, and the deep posterior tibiotalar ligament inserted at 17.8 mm (95% confidence interval, 16.3 to 19.3 mm) from the posteromedial talar tubercle.

CONCLUSIONS

The tibionavicular, tibiospring, and deep posterior tibiotalar ligament bands were constant components of the deltoid ligament. The deep posterior tibiotalar ligament was the largest band of the deltoid ligament.

CLINICAL RELEVANCE

The anatomical data regarding the deltoid ligament bands in this study will help to guide anatomical placement of repairs and reconstructions for deltoid ligament injury or instability.

Biomechanical evaluation of syndesmotic screw position: a finite-element analysis

OBJECTIVES

To evaluate the stresses in syndesmotic screws and widening of syndesmosis under loading after placement of the screws at different levels from the ankle joint line and to determine the optimal level.

METHODS

From a set of computed tomographic data of an ankle, a 3-dimensional finite-element model was reconstructed. Six fixation configurations of the syndesmosis with placement of 3.5 or 4.5 mm single tricortical screws at 20-45 mm from the tibiotalar joint were performed on this model. Physiological loads approximating those during both midstance and heel-off states of stance phase of normal walking were applied to evaluate the stress in the screw and widening of the syndesmosis.

RESULTS

Among the 6 fixation configurations, the lowest von Mises stress was found in the screws placed 30-40 mm above the joint line (373.31-380.17 MPa for 3.5 mm cortical screw and 284.06-327.31 MPa for 4.5 mm cortical screw in midstance phases), whereas the least syndesmosis widening was determined when the screw was placed 30 mm above the tibial plafond (0.005 mm) for 3.5 mm cortical screw and 20, 25, and 30 mm above the tibial plafond (0.004 mm for each, respectively) for 4.5 mm cortical screw during midstance phases.

CONCLUSIONS

This study showed that syndesmosis fixation at the level of 30-40 mm above the tibiotalar joint has advantages with regard to stress in screws in comparison with the other evaluated levels.