The anatomy and function of the contents of the human tarsal sinus and canal

Talocalcaneal Ligament Reconstruction Kinematic Simulation for Progressive Collapsing Foot Deformity

BACKGROUND

In progressive collapsing foot deformity (PCFD), an internal and plantar rotation of the talus relative to the calcaneus may result in painful peritalar subluxation. Medial soft tissue procedures (eg, spring ligament repair) aim to correct the talar position via the navicular bone if bony correction alone is not sufficient. The effect of the medial soft tissue reconstruction on the talar reposition remains unclear. We hypothesized that a subtalar talocalcaneal ligament reconstruction might be favorable in PCFD to correct talar internal malposition directly. This pilot study aims to evaluate the anatomical feasibility and kinematic behavior of a subtalar ligament reconstruction in PCFD.

METHODS

Three-dimensional surface model from 10 healthy ankles were produced. A total of 1089 different potential ligament courses were evaluated in a standardized manner. A motion of inversion/eversion and talar internal/external in relation to the calcaneus were simulated and the ligament strain, expressed as a positive length variation, for each ligament was analyzed. The optimal combination for the ligament reconstruction with increased length in internal rotation of the talus, isometric kinematic behavior in inversion/eversion, and extraarticular insertion on talus and calcaneus was selected.

RESULTS

A laterodistal orientation of the talar insertion point in respect to the subtalar joint axis and laterodistal deviation of the calcaneal insertion point presents the highest ligament lengthening in internal talar rotation (+0.56 mm [3.8% of total length]) and presented a near-isometric performance in inversion/eversion (+0.01 to -0.01 mm [0.1% of total length]).

CONCLUSION

This kinematic model shows that a ligament reconstruction in the subtalar space presents a pattern of length variation that may stabilize the internal talar rotation without impeding the physiological subtalar motion.

CLINICAL RELEVANCE

This study investigates the optimal location, feasibility, and kinematic behavior of a ligament reconstruction that could help stabilize peritalar subluxation in progressive collapsing foot deformity.

[Formula: see text].

The Evolution of Sinus Tarsi Syndrome-What Is the Underlying Pathology?-A Critical Review

Background and Objectives: Sinus tarsi syndrome (STS) is defined as pain located at the lateral opening of the tarsal sinus. The exact etiology of sinus tarsi syndrome is not completely understood. Some do not believe it to be a true pathology. This review aims to clarify the definition of sinus tarsi syndrome to better understand the underlying pathologies. We further propose an algorithm to evaluate sinus tarsi pain and provide advice for consecutive treatment options. Design: This is a narrative review. By searching PubMed, the available current literature was reviewed. Articles were critically analyzed to determine the pathoanatomy, biomechanics, and etiology of sinus tarsi pain. Algorithms for clinical evaluation, diagnosis, and treatment were also recorded. Finally, the authors approach to evaluating and treating sinus tarsi pain was included in this review. Results: Reviewing the available literature, STS seems to be a catch-all phrase used to describe any pain in this anatomic region. Many causes of sinus tarsi pain were listed, including impingement, subtalar instability, and many other pathologies around the ankle. Conclusions: A thorough evaluation of patients presenting with pain in the sinus tarsi or instability of the hindfoot is essential to determining the underlying cause. When the cause of pain is still not clear after clinical exam and radiologic assessment, subtalar arthroscopy can be helpful as both a diagnostic and treatment tool. We propose that the term of STS should be avoided and that a more accurate diagnosis be used when possible. Once a diagnosis is made, appropriate treatment can be initiated.

Evaluation of chronic ankle instability and subtalar instability using the angle between the anterior talofibular ligament and calcaneofibular ligament

PURPOSE

A series of studies have reported a change in the length or thickness of the anterior talofibular (ATFL) and calcaneofibular (CFL) ligaments in patients with chronic ankle instability. However, no study has examined the changes in the angle between the ATFL and CFL in patients diagnosed with chronic ankle instability. Therefore, this study analyzed the change in the angle between the ATFL and CFL in patients diagnosed with chronic ankle instability to confirm its relevance.

METHODS

This retrospective study included 60 patients who had undergone surgery for chronic ankle instability. Stress radiographs comprising the anterior drawer test, varus stress test, Broden's view stress test, and magnetic resonance imaging (MRI) were performed in all patients. The angle between the ATFL and CFL was measured by indicating the vector at the attachment site, as seen on the sagittal plane. Three groups were classified according to the angle between the two ligaments measured by MRI: group I when the angle was > 90°, Group II when the angle was 71-90°, and Group III when the angle was ≤ 70°. The accompanying injuries to the subtalar joint ligament were analyzed via MRI.

RESULTS

A comparison of the angles between the ATFL and CFL measured on MRI in Group I, Group II, and Group III with the angles measured in the operating room revealed a significant correlation. Broden's view stress test revealed a statistically significant difference among the three groups (p < 0.05). The accompanying subtalar joint ligament injuries differed significantly among the three groups (p < 0.05).

CONCLUSION

The ATFL-CFL angle in patients with ankle instability is smaller than the average angle in ordinary people. Therefore, the ATFL-CFL angle might be a reliable and representative measurement tool to assess chronic ankle instability, and subtalar joint instability should be considered if the ATFL-CFL angle is 70° or less.

LEVEL OF EVIDENCE

Level III.

Acute and Chronic Subtalar Joint Instability: Does It Really Exist?

Acute and chronic subtalar instability and commonly coexistent with other hindfoot pathology but can be difficult to diagnose. A high degree of clinical suspicion is required as most imaging modalities and clinical maneuvers are poor at detecting isolated subtalar instability. The initial treatment is similar to ankle instability, and a wide variety of operative interventions have been presented in the literature for persistent instability. Outcomes are variable and limited.

Sinus tarsi and sinus tarsi syndrome: An imaging review

The sinus tarsi is a funnel-shaped region at the junction of mid-foot and hind-foot which contains fat, vessels, nerves and ligaments. The ligaments help stabilise the subtalar joint and maintain the longitudinal arch of the foot. The nerve endings contain proprioceptive fibres indicating a role for the sinus tarsi in movement of the foot. Sinus tarsi syndrome is a clinical entity characterised by lateral hind-foot pain with worsening on palpation and weight-bearing, and perceived instability. It is associated with both traumatic and non-traumatic causes. Magnetic resonance imaging is the imaging modality of choice for assessment of the sinus tarsi and sinus tarsi syndrome. In this review article, we review the anatomy and various aetiologies of sinus tarsi syndrome, along with the imaging appearances.

Role of the intrinsic subtalar ligaments in subtalar instability and consequences for clinical practice

Subtalar instability (STI) is a disabling complication after an acute lateral ankle sprain and remains a challenging problem. The pathophysiology is difficult to understand. Especially the relative contribution of the intrinsic subtalar ligaments in the stability of the subtalar joint is still controversial. Diagnosis is difficult because of the overlapping clinical signs with talocrural instability and the absence of a reliable diagnostic reference test. This often results in misdiagnosis and inappropriate treatment. Recent research offers new insights in the pathophysiology of subtalar instability and the importance of the intrinsic subtalar ligaments. Recent publications clarify the local anatomical and biomechanical characteristics of the subtalar ligaments. The cervical ligament and interosseous talocalcaneal ligament seem to play an important function in the normal kinematics and stability of the subtalar joint. In addition to the calcaneofibular ligament (CFL), these ligaments seem to have an important role in the pathomechanics of subtalar instability (STI). These new insights have an impact on the approach to STI in clinical practice. Diagnosis of STI can be performed be performed by a step-by-step approach to raise the suspicion to STI. This approach consists of clinical signs, abnormalities of the subtalar ligaments on MRI and intraoperative evaluation. Surgical treatment should address all the aspects of the instability and focus on a restoration of the normal anatomical and biomechanical properties. Besides a low threshold to reconstruct the CFL, a reconstruction of the subtalar ligaments should be considered in complex cases of instability. The purpose of this review is to provide a comprehensive update of the current literature focused on the contribution of the different ligaments in the stability of the subtalar joint. This review aims to introduce the more recent findings in the earlier hypotheses on normal kinesiology, pathophysiology and relation with talocrural instability. The consequences of this improved understanding of pathophysiology on patient identification, treatment and future research are described.

Evaluation of the heel external rotation test in soft tissue deficiencies associated with adult acquired flatfoot deformity (AAFD). A cadaver sectioning analysis

BACKGROUND

To date, evaluation of the heel external rotation test has not been taken with respect to AAFD. Traditional 'gold standard' tests do not account for the contribution of the midfoot ligaments towards instability. These tests would be flawed as any midfoot instability may produce a false positive result.

AIMS

To evaluate the differential contribution of the spring, deltoid and other local ligaments in external rotation generated at the heel.

METHODS

Serial ligament sectioning was performed on 16 cadaveric specimens, with a 40 N-external rotation force applied to the heel. These were divided into four groups with different sequences of ligament sectioning. Measurements of the total amount/range of external, tibiotalar and subtalar rotation were made.

RESULTS

The deep component of the deltoid ligament (DD) was the main ligament influencing heel external rotation (P < 0.05, in all cases), and acted primarily at the tibiotalar joint (87.9 %). The spring ligament (SL) influenced heel external rotation predominantly (91.2 %) at the subtalar joint (STJ). Greater than 20 degrees external rotation could only be achieved with DD sectioning. The interosseous (IO) and cervical (CL) ligaments did not significantly contribute to external rotation at either joint (P > 0.05).

CONCLUSION

Clinically relevant external rotation (>20 degrees) is solely attributable to DD failure in the presence of intact lateral ligaments (LL). This test may improve detection of DD instability and allow clinicians to subclassify patients with Stage 2 AAFD into those where DD may or may not be compromised.

The different subtalar ligaments show significant differences in their mechanical properties

BACKGROUND

Today, the relative contribution of each ligamentous structure in the stability of the subtalar joint is still unclear. The purpose of this study is to assess the material properties of the different ligamentous structures of the subtalar joint.

METHODS

Eighteen paired fresh-frozen cadaveric feet were used to obtain bone-ligament-bone complexes of the calcaneofibular ligament (CFL), the cervical ligament (CL) and the anterior capsular ligament-interosseous talocalcaneal ligament complex (ACaL-ITCL). The samples were subjected to uniaxial testing to calculate their respective stiffness and failure load.

RESULTS

The stiffness of ACaL-ITCL complex (mean: 150 ± 51 N/mm, 95% confidence interval (CI): 125.0-176.6 N/mm) was significantly higher than both CFL (mean: 55.8 ± 23.0 N/mm, CI: 43.8-67.7 N/mm) and CL (mean: 63.9 ± 38.0 N/mm, CI: 44.4-83.3 N/mm). The failure load of both the ACaL-ITCL complex (mean:382.5 ± 158 N, CI: 304.1-460.8 N) and the CFL (mean:320.4 ± 122.0 N, CI: 257.5-383.2 N) were significantly higher than that of the CL (mean:163.5 ± 58.0 N, CI: 131.3-195.7 N). The injury pattern demonstrated a partial rupture in all CFL and ACaL-ITCL specimens and in 60% of the CL specimens.

CONCLUSION

The CFL, CL and ACaL-ITCL show significant differences in their intrinsic mechanical properties. Both the CFL and CL are more compliant ligaments and seem to be involved in the development of subtalar instability. Based on the material properties, a gracilis tendon graft seems more appropriate than a synthetic ligament to reconstruct a CL or CFL. A partial rupture was the most commonly seen injury pattern in all ligaments. A fibular avulsion of the CFL was only rarely seen. The injury patterns need further investigation as they are important to optimize diagnosis and treatment.

A high rate of talocalcaneal interosseous ligament tears was found in chronic lateral ankle instability with sinus tarsi pain

PURPOSE

To evaluate the arthroscopic findings of subtalar joints, including interosseous talocalcaneal ligament (ITCL) tear, in patients with chronic lateral ankle instability (CLAI) and sinus tarsi pain.

METHODS

A total of 118 ankles (109 patients) having CLAI with sinus tarsi pain who had undergone subtalar arthroscopy and lateral ankle ligament surgery were evaluated. The medical records, radiologic images, and the arthroscopic images and videos were reviewed. ITCL tears were classified into 4 grades: grade 0 (no tear), grade 1 (mild), grade 2 (moderate), and grade 3 (severe). The efficacy of magnetic resonance imaging (MRI) in diagnosing ITCL tears was also evaluated by comparing preoperative official readings of MRI to arthroscopic findings. The pre- and postoperative functional scores were also assessed.

RESULTS

The overall tear rate of ITCL was 107/118 (90.7%). There were 29 ankles (23.6%) with grade 1, 42 ankles (35.6%) with grade 2, and 36 ankles (30.5%) with grade 3 tears. Isolated lateral ankle instability (LAI) was diagnosed in 43 ankles (36.4%), subtalar instability (STI) in 30 ankles (25.4%), and LAI with STI in 45 ankles (38.1%). There was a statistically significant relationship between the ITCL tear grade and the final diagnosis. ITCL tear was confirmed or suspected in 81 ankles (68.6%) on preoperative MRI. Pain Visual Analog Score and functional outcome scores including the American Orthopaedic Foot & Ankle Society and Karlsson-Peterson scores showed significant improvement after the surgery.

CONCLUSION

A high rate (90.7%) of ITCL tears was noted in CLAI patients with sinus tarsi pain. ITCL damage may play an important role in subtalar instability in patients with CLAI and sinus tarsi pain. Subtalar arthroscopic evaluation for ITCL tear is important for correct diagnosis for CLAI with sinus tarsi pain.

LEVEL OF EVIDENCE

IV.

Current Concepts on Subtalar Instability

Subtalar instability remains a topic of debate, and its precise cause is still unknown. The mechanism of injury and clinical symptoms of ankle and subtalar instabilities largely overlap, resulting in many cases of isolated or combined subtalar instability that are often misdiagnosed. Neglecting the subtalar instability may lead to failure of conservative or surgical treatment and result in chronic ankle instability. Understanding the accurate anatomy and biomechanics of the subtalar joint, their interplay, and the contributions of the different subtalar soft tissue structures is fundamental to correctly diagnose and manage subtalar instability. An accurate diagnosis is crucial to correctly identify those patients with instability who may require conservative or surgical treatment. Many different nonsurgical and surgical approaches have been proposed to manage combined or isolated subtalar instability, and the clinician should be aware of available treatment options to make an informed decision. In this current concepts narrative review, we provide a comprehensive overview of the current knowledge on the anatomy, biomechanics, clinical and imaging diagnosis, nonsurgical and surgical treatment options, and outcomes after subtalar instability treatment.

The intrinsic subtalar ligaments have a consistent presence, location and morphology

BACKGROUND

Chronic subtalar instability is a disabling complication after acute ankle sprains. Currently, the literature describing the anatomy of the intrinsic subtalar ligaments is limited and equivocal which causes difficulties in diagnosis and treatment of subtalar instability. The purpose of this study is to assess the anatomical characteristics of the subtalar ligaments and to clarify some points of confusion.

METHODS

In 16 cadaveric feet, the dimensions and locations of the subtalar ankle ligaments were assessed and measured. CT-scans before dissection and after indication of the footprints with radio-opaque paint allowed to generate 3D models and assess the footprint characteristics.

RESULTS

The cervical ligament (CL) had similar dimensions as the lateral ligaments: anterior length 13.9 ± 1.5 mm, posterior length 18.5 ± 2.9 mm, talar width 13.6 ± 2.2 mm, calcaneal width 15.8 ± 3.7 mm. The anterior capsular ligament (ACaL) and interosseous talocalcaneal ligament (ITCL) were found to be smaller structures with consistent dimensions and locations.

CONCLUSION

This study identified consistent characteristics of the intrinsic subtalar ligaments and clarifies the local anatomical situation. The dimensions and footprints of the intrinsic ligaments of the subtalar joint suggest a more important role of the CL and ACaL in the stability of the subtalar joint. The results of this study are relevant to improve diagnostic tools and offer some guidelines when reconstructing the injured ligaments.

Biomechanical comparison of tenodesis reconstruction for subtalar instability: a finite element analysis

Background

There are several types of tenodesis reconstruction designed for subtalar instability. However, no comprehensive comparison has been conducted among these procedures in terms of their correcting power so far. The objective of this study is to evaluate the biomechanical behaviors of 5 representative procedures through finite element analysis.

Methods

Finite element models were established and validated based on one of our previous studies. The Pisani interosseous talocalcaneal ligament (ITCL) reconstruction, Schon cervical ligament (CL) reconstruction and Choisne calcaneofibular ligament (CFL) reconstruction were compared on the model with the CFL, ITCL and CL sectioned. The Schon triligamentous reconstruction and Mann triligamentous reconstruction were compared on the model with the CFL, ITCL and CL, as well as the ATFL sectioned. The inversion and external/internal rotation were quantified at different ankle positions based on the rotational moment. Then, the stress in ligaments and reconstructed grafts and the contact characteristics of the subtalar joint under inversional stress test were calculated and compared accordingly.

Results

For single ligament reconstruction, the Choisne CFL reconstruction provided the greatest degree of correction for subtalar instability, followed by the Schon CL reconstruction and then the Pisani ITCL reconstruction. For triligamentous reconstruction, the Mann procedure outperformed the Schon procedure in alleviating the subtalar instability.

Conclusion

The finite element analysis showed that the Choisne CFL reconstruction and Mann triligamentous reconstruction provided the greatest degree of immediate postoperative subtalar stability. However, both procedures could not restore the biomechanical behaviors of the subtalar joint to normal. The long-term efficacy of these procedures warrants further investigation using a substantially larger sample of clinical cases.

Surgical Treatment of Subtalar Joint Instability: Safety and Accuracy of a New Technique in a Cadaver Model

New surgical strategies to treat symptomatic subtalar joint (STJ) instability are evolving. We modified a previously described reconstruction strategy and then refined our new surgical technique through simulated surgery and subsequent cadaver dissections. Our purpose was to show that a tunnel intended to facilitate STJ stabilization surgery could safely be drilled across the footprints of the interosseous talocalcaneal ligament (ITCL). A percutaneous fluoroscopically guided tunnel for the purpose of ITCL reconstruction was created in 10 cadaveric below-knee specimens. Accuracy of the tunnel with relation to the anatomic boundaries of the ITCL attachment sites as well as damage to relevant structures at risk were recorded. Two sets of 5 surgeries were performed to assess for improvement in technique. Mean distances from the tunnel to the ITCL on the calcaneus improved between groups 1 and 2: 4.04 and 1.80 mm, respectively (p = .04). Mean distances from the tunnel to the ITCL on the talus improved between groups 1 and 2: 6.2 and 1.8 mm, respectively (p = .08). With information obtained from this study, an osseous tunnel can be safely placed within 2 mm of the ITCL footprints.

Estimating the stabilizing function of ankle and subtalar ligaments via a morphology-specific three-dimensional dynamic model

Knowledge of the stabilizing role of the ankle and subtalar ligaments is important for improving clinical techniques such as ligament repair and reconstruction. However, this knowledge is incomplete. The goal of this study was to expand this knowledge by investigating the stabilizing function of the ligaments using multiple morphologically subject-specific computational models. Nine models were created from the lower extremities of nine donors. Each model consisted of the articulating bones, articular cartilage, and ligaments. Simulations were conducted in ADAMS™ - a dynamic simulation program. During simulation, tibia and fibula were fixed while cyclic moments in all three anatomical planes were applied to the calcaneus one-at-a-time. The resulting displacements between the bones and the forces in each ligament were computed. Simulations were conducted with all ligaments intact and after simulated ligament serial sectioning. Each model was validated by comparing the simulation results to experimental data obtained from the specimen used to construct the model. From the results the stabilizing role of each ligament was established and the effect of ligament sectioning on Range of Motion and Overall Laxity was identified. On the lateral side, ATFL provided stabilization in supination, CFL restrained inversion, external rotation and dorsiflexion and PTFL limited dorsiflexion and external rotation. On the medial side, PTTL restrained dorsiflexion and internal rotation, ATTL limited plantarflexion and external rotation, and TCL limited dorsiflexion, eversion and external rotation. At the subtalar joint, ITCL limited plantarflexion and its posterior-lateral bundle restrained subtalar inversion. CL restrained plantarflexion/dorsiflexion, and internal and external rotation. The large inter-model variability observed in the results indicate the importance of using multiple subject-specific models rather than relying on one "representative" model.

Morphological features of the cervical ligament

PURPOSE

The purpose of this study was to clarify the morphological characteristics of the cervical ligament (CL).

METHODS

This study examined 80 legs from 40 Japanese cadavers. The CL was classified by the number of fiber bundles. The morphological features measured were fiber bundle length, width, thickness, and angle with the sagittal plane.

RESULTS

The CL was classified as follows: Type I, the CL is a single fiber; Type II, the CL consists of a superficial fiber and an inferior fiber; and Type III, the CL consists of a superficial fiber, intermediate fiber, and inferior fiber. Type I was seen in 15 feet, Type II in 57 feet, and Type III in 8 feet. In comparisons of morphological features within each type, significant differences were seen in fiber bundle length, width, and angle between superior fiber bundles and inferior fiber bundles of Type II and Type III. In comparison among types, the total fiber bundle width was significantly wider in Type II and Type III than in Type I, and the angle was significantly smaller in Type III than in Type I.

CONCLUSION

The results of this study suggested that each type may have different sub-talar joint control functions.

Anatomy of the Tarsal Canal and Sinus in Relation to the Subtalar Joint Capsule

BACKGROUND

Anatomical knowledge of the tarsal canal and sinus is still unclear owing to the complexity of the ligamentous structures within them, particularly the relationship with the capsules of the subtalar joints. The aim of this study was to examine the anatomical relationship between the fibrous tissues of the tarsal canal and sinus and the articular capsules of the subtalar joint.

METHODS

We conducted a descriptive anatomical study of 21 embalmed cadaveric ankles. For a macroscopic overview of the subtalar joint, we removed the talus in 18 ankles and separated the fibrous tissues from the surrounding connective tissues to analyze the layered relationship between the inferior extensor retinaculum (IER) and the subtalar joint capsule. Additionally, we histologically analyzed the tarsal canal and the medial and lateral sides of the tarsal sinus using Masson's trichrome staining in 3 ankles.

RESULTS

The medial and intermediate roots of the IER and interosseous talocalcaneal ligament (ITCL) were located in the same layer and were connected to each other, between the capsules of the posterior talocalcaneal and talocalcaneonavicular joints. The intermediate root of the IER and the cervical ligament (CL) had adjacent attachments on the tarsal sinus, and synovial tissues originating from the joint capsules filled the remaining area in the tarsal canal and sinus.

CONCLUSION

We determined that the tarsal canal and sinus tarsi contained 3 layered structures: the anterior capsule of the posterior talocalcaneal joint, including the anterior capsule ligament; the layer of ITCL and IER; and the posterior capsule of the talocalcaneonavicular joint, including the CL.

CLINICAL RELEVANCE

The results of this study may help with the understanding of the pathomechanism of subtalar instability and sinus tarsi syndrome, resulting in better treatment.

Anatomy of the Subtalar Joint

The subtalar joint is divided into the talocalcaneonavicular and the talocalcaneal joint, separated by a conical interosseous tunnel (canalis and sinus tarsi). The talocalcaneonavicular joint is a ball-and-socket articulation (coxa pedis). An important part of the coxa pedis is the spring ligament. The canalis and sinus tarsi are occupied by the roots of the inferior extensor retinaculum, cervical ligament, interosseous talocalcaneal ligament, and anterior talocalcaneal ligament. Three-dimensional motion in the subtalar joint complex (eversion/inversion) is guided by the axial alignment of the talus, calcaneus, and navicular; the ligaments; and the shape of the articular surfaces.

Differences Between Subtalar Instability and Lateral Ankle Instability Focusing on Subtalar Ligaments Based on Three Dimensional Isotropic Magnetic Resonance Imaging

OBJECTIVE

The purpose of this study was to assess the differences between subtalar instability (STI) and lateral ankle instability (LAI) focusing on subtalar ligaments using 3-dimensional (3D) isotropic magnetic resonance imaging (MRI).

METHODS

Preoperative MRIs of 10 patients with STI who failed nonoperative treatment and consequently underwent arthroscopic subtalar reconstruction were compared with preoperative MRIs of 23 patients with LAI who underwent ligament repair or reconstruction. Dimensions of anterior capsular ligament (ACL), interosseous talocalcaneal ligament (ITCL), calcaneofibular ligament (CFL), and anterior talofibular ligament (ATFL) were measured. Tears of ACL, ITCL, CFL, ATFL, cervical ligament, and inferior extensor retinaculum were analyzed.

RESULTS

Patients with subtalar instability had significantly lower ACL thickness and width than patients with LAI (thickness: 1.48 vs 2.12 mm, P = 0.045; width: 7.30 vs 8.64 mm, P = 0.029). An ACL thickness of 1.8 mm or less had sensitivity and specificity both at 75.0%, and an ACL width of 8 mm or less had sensitivity of 75.0% and specificity of 85.0% for discriminating STI from LAI. Absence or complete tear of ACL was more frequent in patients with STI than in patients with LAI (60.0% vs 13.0%, P = 0.010). The ATFL thickness was significantly greater in patients with LAI (P = 0.001). Complete tear of ATFL was more common in patients with LAI (P = 0.008). Complete tear of CFL was common in both the STI and LAI groups without significant difference (20.0% vs 21.7%). There was no significant difference in thickness and width of ITCL and in CFL thickness. Complete tear of ITCL, cervical ligament, and inferior extensor retinaculum were rare without significant difference.

CONCLUSION

In patients with STI, the ACL is thin and narrow and more commonly absent or torn compared with patients with LAI. Complete tear of ATFL was more common in patients with LAI. Complete tear of CFL was commonly encountered in both the STI and LAI groups.

Subtalar instability: imaging features of subtalar ligaments on 3D isotropic ankle MRI

BACKGROUND

MRI analysis of subtalar ligaments in the tarsal sinus has not been well performed. We retrospectively investigated the appearance of subtalar ligaments using 3D isotropic MRI and compared imaging findings of subtalar ligaments between patients with subtalar instability (STI) and controls.

METHODS

Preoperative MRIs of 23 STI patients treated with arthroscopic subtalar reconstruction were compared to MRIs of 23 age- and sex-matched control subjects without STI. Thickness and width of anterior capsular ligament (ACL) and interosseous talocalcaneal ligament (ITCL) as well as thickness of calcaneofibular ligament (CFL) and anterior talofibular ligament (ATFL) were measured. Abnormalities in ACL, ITCL, CFL, ATFL, cervical ligament, and inferior extensor retinaculum were analyzed.

RESULTS

STI patients had significantly smaller ACL thickness and ACL width than controls (ACL thickness: 1.73 mm vs. 2.22 mm, p = 0.007; ACL width: 7.21 mm vs. 8.80 mm, p = 0.004). ACL thickness of ≤2.1 mm had a sensitivity of 66.7% and a specificity of 66.7% for diagnosis of STI. ACL width of ≤7.9 mm had a sensitivity of 80.0% and a specificity of 76.2% for the diagnosis of STI. However, thickness and width of ITCL, thickness of CFL, or thickness of ATFL was not significantly different between the two groups. Absence or complete tear of ACL was significantly more frequent in STI patients than that in controls (34.8% vs. 8.7%, p = 0.035). Complete tear of CFL and ATFL was more common in STI patients than that in controls, although the difference between the two groups was not statistically significant. Abnormalities of ITCL, cervical ligament, or inferior extensor retinaculum were not significantly different between the two groups.

CONCLUSIONS

MRI features of thin or narrow ACLs may suggest STI. Absence or complete tear of ACL was significantly more common in STI patients than that in controls.

The dimensions of the tarsal sinus and canal in different foot positions and its clinical implications

This study presents a reference for the dimensions of the tarsal sinus and canal in healthy adults in different foot positions to facilitate understanding of the kinematics of the subtalar joint, the effect of an implant, and other clinical issues. In a 3D CT stress test on 20 subjects, the right foot was forced into a neutral and eight different extreme foot positions while CT scans were obtained. The bones were segmented in the neutral foot position. The kinematics of the bones in the extreme positions were determined relative to the neutral position. The dimensions of the tarsal sinus and canal were calculated by determining the radii of the maximal inscribed spheres at 20 equidistant locations along an axis in 3D surface models of the tali and calcanei in each foot position. The radii were small on the medial side and increased laterally. Medial from the middle, the radii were small and not significantly different among the various foot positions. At the lateral side, the dimensions were affected mainly by eversion or inversion and less by dorsiflexion or plantarflexion. The pattern was reproducible among subjects, but there were between-subject differences. The dimensions are mostly determined by rotation in the frontal plane. A pivot point was found medial from the middle. These data serve as a reference and model for predicting the effect of sinus implants and understanding such clinical problems as sinus tarsi syndrome. Between-subjects differences have to be taken into account. Clin. Anat. 30:1049-1057, 2017. © 2017 Wiley Periodicals, Inc.

Posteromedial subtalar coalitions: prevalence and associated morphological alterations of the sustentaculum tali

BACKGROUND

A variant form of subtalar coalition isolated to the posterior sustentaculum has been previously described, though its prevalence is not known and its relationship to the middle facet has not been characterized.

OBJECTIVE

To determine the prevalence and morphological alterations of isolated posteromedial subtalar coalitions.

MATERIALS AND METHODS

Computed tomography (CT) images of the foot or ankle performed from 2004 to 2012 were reviewed and 97 patients (mean age: 13.3+/-2.9 years; range: 9-19 years) with subtalar coalition were identified. In 41 (42%) of these, the condition was bilateral, yielding a total of 138 subtalar coalitions. In the 33 patients where CT demonstrated isolated posteromedial subtalar coalitions, multiplanar reformats along the long axis of the sustentaculum tali were generated, from which the anteroposterior dimensions of the sustentaculum tali and middle facet were measured. Posterior sustentaculum measurements defining the posterior extension of the sustentaculum beyond the middle facet were directly measured by two radiologists. Ratios of middle facet to posterior sustentaculum measurements were calculated. Thirty-three patients undergoing CT for ankle fracture served as controls.

RESULTS

Ninety-seven of 138 coalitions (70.2%) affected the middle facet and 2/138 (1.4%) involved the posterior facet. There were 39 (28.2%) posteromedial subtalar coalitions in 33 patients. Mean AP measurements of the middle facet and posterior sustentaculum in patients with posteromedial subtalar coalitions were 12.6 mm and 18.2 mm, respectively, compared to 16.6 mm and 9.2 mm in controls (P<0.001). Mean middle facet/posterior sustenaculum (MF/PS) ratios were 0.74 for posteromedial subtalar coalitions vs. 1.92 for controls (P<0.001).

CONCLUSION

Posteromedial subtalar coalitions comprise more than one-quarter of subtalar coalitions, and are associated with an intact, but shorter, middle facet and longer sustentaculum tali. This observation may aid in accurate diagnosis and management of this relatively common disorder.

Subtalar anatomy and mechanics

Understanding subtalar joint biomechanics and pathomechanics provides a framework for understanding both common pathologic hindfoot and forefoot conditions and surgical planning. It is important to identify mechanical impairment and to define what mechanical effect is needed to change a pathologic condition. It is also important to know what the initial problem is and what the consequences are in terms of soft tissue or bony stress leading to peritalar injury. Whenever possible, one should try to operate to change pathomechanics and facilitate spontaneous repair of stressed structures.

Ligament structures in the tarsal sinus and canal

BACKGROUND

The concrete anatomy and functional characteristics of the subtalar ligaments have been a matter of debate that some believe has hampered the progress of clinical ligament reconstruction.

METHODS

In 32 fresh-frozen cadaver feet, the course of the inferior extensor retinaculum (IER) and other subtalar ligaments was carefully measured and photographed both from the portal of the tarsal sinus and from a posterior view.

RESULTS

The IER inserted inside the tarsal sinus and canal by means of 3 roots: a lateral, an intermediate, and a medial one. These roots, along with the tarsal canal, divided the subtalar space into 3 parts. In front of the IER and inside the tarsal sinus, the thick cervical ligament (CL) lay at a 45-degree angle to the calcaneus. Behind the IER and inside the posterior capsule, in most cases (25 of 32 specimens), the posterior capsular ligament (PCaL) lay directly in front of the posterior talocalcaneal facet. Inside the tarsal canal, the fan-shaped medial root of the IER spread from outside upper lateral to lower medial, and the interosseous talocalcaneal ligament (ITCL) ran from upper medial to lower lateral; fibers of these 2 ligaments blended tightly together to form a V-shaped ligament complex. Just anterior to this complex in some cases (20 of 32 specimens), a short narrow upright ligament, the tarsal canal ligament (TCL), was located behind the middle talocalcaneal joint.

CONCLUSION

The results of this study show that the CL is the primary ligament in the tarsal sinus and that the ITCL is a thin single band rather than a strong bilaminar ligament located inside the tarsal canal. Instead, the medial root of the IER is the primary ligamentous structure in the tarsal canal.

CLINICAL RELEVANCE

The anatomical description provided here may provide a more accurate theoretical foundation for clinical subtalar stability restoration.

Subtalar instability: diagnosis and treatment

Subtalar instability is challenging to diagnose. It rarely follows a complete subtalar dislocation, an event more likely to result in subtalar pain, stiffness, and arthritis. By history, subtalar instability can be suggested by the patient’s feeling of ankle instability, easy “rolling over,” and a need to look at the ground constantly when walking. Clinical measures for inversion and eversion do not accurately reflect isolated subtalar motion, as soft tissue and other joint motion confound the examination. Stress radiographs have high false positive rates. Magnetic resonance imaging can show injured or disorganized ligaments suggestive of recurrent subtalar strain, but are not dynamic studies and cannot alone diagnose instability. Operative treatment, when elected, should focus on determining the source of the problem. Generally direct repair of the lateral ligaments is sufficient. Bony malalignment should always be considered especially in the setting when previous ligament reconstruction has failed.

J. Leonard Goldner Award 2010. Ligament balancing for total ankle arthroplasty: an in vitro evaluation of the elongation of the hind- and midfoot ligaments

BACKGROUND

The changes in length of the hindfoot ligaments in response to alterations in ankle and subtalar joint orientation under physiologic load in eight fresh-frozen cadaver limbs were documented.

RESULTS

In eversion, the tibiocalcaneal (11% ± 4%, mean ± SD], calcaneofibular (6% ± 4%), posterior talofibular (7% ± 4%), posterolateral talocalcaneal (21% ± 9%), posteromedial talocalcaneal (33% ± 45%) and calcaneonavicular (bifurcate) (8% ± 7%) ligaments were elongated relative to their lengths in inversion. In inversion, the anterior capsular (talocalcaneal) (5% ± 3%) and the plantar cuboidnavicular (5% ± 6%) ligaments were elongated relative to their everted lengths. In dorsiflexion, the superficial (26% ± 8%) and deep posterior tibiotalar (30% ± 13%), calcaneofibular (8% ± 4%), tibiocalcaneal (4% ± 2%) and lateral talocalcaneal (cervical) (2% ± 1%) ligaments were elongated. In plantarflexion, the tibionavicular (26% ± 5%) and the anterior talofibular (7% ± 4%) ligaments were lengthened. No statistically significant elongation was documented in any ankle position for the anterior tibiotalar, talocalcaneal interosseous, plantar calcaneocuboid, calcaneocuboid (bifurcate), all components of the spring ligament, and the dorsal cuboidnavicular ligaments.

CONCLUSION

Components of the deltoid ligament complex elongated largest at the ankle joint with any hindfoot movement but inversion. Therefore, selective release of components of the deltoid ligament complex may provide a means for achieving optimal ligament balancing in total ankle arthroplasty. Specifically, release of the superficial and deep posterior tibiotalar ligament may improve range of motion in total ankle arthroplasties, whereas the release of the tibiocalcaneal ligament may correct a varus talar tilt.

Subtalar instability: a biomechanical cadaver study

HYPOTHESIS

Subtalar instability is thought to be one of the possible causes for chronic functional instability of the foot and ankle. The purpose of this study was to determine the extent of ligament injury that is followed by subtalar instability and to depict consecutive pathologic joint motion.

METHODS

Twelve fresh human cadaver lower legs were investigated with respect to pathologic motion and mobility of the subtalar joint in a modified spinal column simulator after arthrodesis of the talocrural articulation and selective sectioning of the lateral ligaments of the subtalar joint. In order to simulate several injury mechanisms, ligaments were dissected starting anteriorly in group one (n = 6) and posteriorly in group two (n = 6).

RESULTS

Dissection of the bifurcate ligament in group one resulted in a significant increase in plantar- and dorsiflexion, dissection of the inferior extensor retinaculum resulted in a significant increase in eversion and inversion. Additional dissection of the lateral talocalcaneal ligament resulted in a significant increase in internal and external rotation. Dissection of the calcaneofibular ligament in group two was followed by significant kinematic changes regarding all degrees of motion in the subtalar joint.

CONCLUSIONS

The calcaneofibular ligament plays a key role in lateral stabilisation of the subtalar joint. Therefore, ligaments of the subtalar joint should be included in surgical repair.

Mechanical stability of the subtalar joint after lateral ligament sectioning and ankle brace application: a biomechanical experimental study

BACKGROUND

The roles of each ligament supporting the subtalar joint have not been clarified despite several biomechanical studies. The effects of ankle braces on subtalar instability have not been shown.

HYPOTHESIS

The ankle brace has a partial effect on restricting excessive motion of the subtalar joint.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten normal fresh-frozen cadaveric specimens were used. The angular motions of the talus were measured via a magnetic tracking system. The specimens were tested while inversion and eversion forces, as well as internal and external rotation torques, were applied. The calcaneofibular ligament, cervical ligament, and interosseous talocalcaneal ligament were sectioned sequentially, and the roles of each ligament, as well as the stabilizing effects of the ankle brace, were examined.

RESULTS

Complete sectioning of the ligaments increased the angle between the talus and calcaneus in the frontal plane to 51.7 degrees + or - 11.8 degrees compared with 35.7 degrees + or - 6.0 degrees in the intact state when inversion force was applied. There was a statistically significant difference in the angles between complete sectioning of the ligaments and after application of the brace (34.1 degrees + or - 7.3 degrees ) when inversion force was applied. On the other hand, significant differences in subtalar rotation were not found between complete sectioning of the ligaments and application of the brace when internal and external rotational torques were applied.

CONCLUSION

The ankle brace limited inversion of the subtalar joint, but it did not restrict motion after application of internal or external rotational torques.

CLINICAL RELEVANCE

In cases of severe ankle sprains involving the calcaneofibular ligament, cervical ligament, and interosseous talocalcaneal ligament injuries, application of an ankle brace might be less effective in limiting internal-external rotational instabilities than in cases of inversion instabilities in the subtalar joint. An improvement in the design of the brace is needed to restore better rotational stability in the subtalar joint.

[Sinus tarsi syndrome: what hurts?]

Sinus tarsi syndrome, described by O'Connor in 1958 and Brown in 1960, is a clinical finding often seen after an accident, consisting of a painful reaction to pressure on the sinus tarsi. This syndrome has also been described in dancers, volleyball and basketball players, overweight individuals, and patients with foot deformities (flatfoot). We looked for mechanical and functional macroscopic structures in the canalis and sinus tarsi that can be associated with sinus tarsi syndrome in order to deduce therapeutic consequences. We found a complex fibrous layer in the sinus and canalis tarsi that forms slips around the synovial sheats of the extensor tendons under the inferior extensor retinaculum. Both limbs run deep to the base of the sinus and canalis tarsi. The lateral band inserts into the sinus tarsi at the calcaneus, while the medial band inserts at the canalis tarsi at the talus and calcaneus. Instead of the term "interosseous ligaments," we recommend referring to the "fundiform ligament" with one lateral and one medial band. Regarding function, one can assume that the medial band of these fundiform ligaments controls the talus at eversion and inversion together with the well-vasculated and well-innervated interarticular fat pads in the sinus and canalis tarsi. While contracting the long extensor muscles of the toes, the ligament forms a control mechanism for the longitudinal arch of the foot in the moving phase.A question is how variations in vascularization or disorders in innervation will alter the turgor of the pads of fat tissue. That is, such alterations would influence the distribution of synovia in the neighboring joints as well as the tension of the involved ligaments.

Deep fascia on the dorsum of the ankle and foot: extensor retinacula revisited

This study revisits the anatomy of the deep fascia over the distal leg, ankle, and dorsum of the foot. The arrangement of the deep fascia in these regions was recorded in 14 lower limbs of adult cadavers using photographs and drawings. The fascial layer from all three sites was subsequently removed in toto, and serial thickness measurements were made along its entire length. In addition, fiber disposition was studied under polarized light, and sections were stained to demonstrate collagen. The arrangement of deep fascia is complex. A common and novel finding at all levels is a crisscross, lattice-like arrangement of fibers. There was little evidence of the clearly defined sturdy band of the superior extensor retinaculum (SER) or of the Y-shaped inferior retinaculum (IER) commonly illustrated in topographical anatomy texts. The SER is a complex area with several thickenings commencing about 3 cm proximal to the tip of the lateral malleolus and gradually increasing to reach a maximum of 270 microm about 5 cm above the malleolus, then gradually returning to original thickness, about 9 cm above the malleolus. Fibers crossing diagonally to each other are a feature of the region. The IER characteristically has two forms: either a cross-shaped band (9 specimens) or a thickened "node" with small extensions radiating toward the malleoli (5 specimens), located about 1-2 cm distal to the lateral malleolus and centred over the common tendon of extensor digitorum where it has maximum thickness (430 microm). The deep fascia is thickened and firmly attached over both malleoli and to the tarsals and metatarsals along both borders of the foot. In general, the deep fascial structures were thicker in males than those in females.

Anatomy of ligamentous structures in the tarsal sinus and canal

BACKGROUND

The descriptive morphology of the interosseous talocalcaneal ligament and other structures in the tarsal sinus and canal vary. An anatomical investigation of the ligamentous structures in the tarsal sinus and canal identified two distinct ligaments, the interosseous talocalcaneal ligament and the anterior capsular ligament, and three components of the medial root of the inferior extensor retinaculum.

METHODS

Forty embalmed cadaver feet were examined. After disarticulation of the ankle joint, the posterior half of the talus was removed. The length, width, and thickness of the two ligaments and the three components of the extensor retinaculum in the tarsal canal and sinus were measured with calipers. Anatomical variations were recorded.

RESULTS

The interosseous talocalcaneal ligament was band-like in 92.5% (38 of 40) of examined specimens, and the anterior capsular ligament was present in 95% (39 of 40) of specimens. The interosseous talocalcaneal ligament, the medial component of the inferior extensor retinaculum, and the talar component of the inferior extensor retinaculum had one or two distinct anatomical variations of morphology and attachments. The interosseous talocalcaneal ligament and the medial component of the extensor retinaculum formed a V shape in the tarsal sinus and canal.

CONCLUSION AND CLINICAL RELEVANCE

We demonstrated the morphology and dimensions of the ligaments and components of the extensor retinaculum in the tarsal sinus and canal. Precise anatomy of the structures in the tarsal sinus and canal will strengthen our understanding of their function in the motion or stabilization of the subtalar joint. There may be a functional link between the medial component of the inferior extensor retinaculum and the interosseous talocalcaneal ligament.

The anatomy of the calcaneus and surrounding structures

Appreciation of the normal anatomy of the calcaneus is significant for various reasons. Restoration of normal anatomy has been of particular interest for fracture care. In addition, knowledge of surrounding structures is important when planning surgical approaches and vital when performing percutaneous procedures. Understanding of anatomic relationships allows discernment of the pathophysiology that is related to chronic conditions. The biomechanics of normal structures provides a theoretic basis for reconstruction and rehabilitation, and individual variations in calcaneal anatomy can be a predisposition for pathology.

Complete dislocation of the talus unaccompanied by fracture

Total dislocation of the talus without a concomitant fracture is an extremely rare injury. Such a case was treated by immediate closed reduction and 6 weeks of cast immobilization. At the 9-year follow-up, the patient had a full range of ankle motion without any signs of avascular necrosis or arthritis.

Sinus tarsi syndrome and subtalar joint instability

Sinus tarsi syndrome is a poorly understood term in the orthopedic world. It is thought of as a painful condition of the sinus tarsi that often responds to corticosteroid injection and is associated with a feeling of instability in the hindfoot. Despite references in the literature, there is no agreement on pathognomonic history, clinical tests, or imaging studies that could help in confirming the diagnosis or establishing the etiology. Some authors relate the clinical condition of sinus tarsi syndrome with instability of the subtalar joint.

The role of the interosseous talocalcaneal ligament in subtalar joint stability

BACKGROUND

Injury of the interosseous talocalcaneal ligament (ITCL) has been recognized as a cause of subtalar instability, though lack of an accepted clinical test has limited the ability of clinicians to reliably make the diagnosis. Clinical effects of ITCL failure remain unclear because of insufficient understanding of the role of the ligament.

METHODS

Load-displacement characteristics of the subtalar joint were studied in six cadaver specimens using an axial distraction test and a transverse multi-direction drawer test. In all tests, cyclic loading (+/-60 N) was applied, and load-displacement responses were collected before and after sectioning of the ITCL. Two parameters were used to analyze the data: neutral-zone laxity as a measure of joint play, and flexibility as a measure of resistance to applied force.

RESULTS

In the axial distraction test, sectioning increased both neutral-zone laxity and flexibility (p =.01 and.02, respectively). In the transverse test, sectioning caused increase of both neutral-zone laxity and flexibility (p <.001, for each). Neutral-zone laxity increased most greatly along an axis defined roughly by the posterior aspect of the fibula and the central region of the medial malleolus. Flexibility increased most in the medial direction (p <.05, for each).

CONCLUSIONS

Results confirmed the role of the ITCL in maintaining apposition of the subtalar joint, as well as suggested its role in stabilizing the subtalar joint against drawer forces applied to the calcaneus from lateral to medial. The dominant direction of increased neutral-zone laxity described above suggests the optimal direction for detecting subtalar instability involved with ITCL injury.

CLINICAL RELEVANCE

ITCL failure may result in subtalar instability and should be examined with a drawer force along the preferential axis roughly from the posterior aspect of the fibula to the central region of the medial malleolus. Further clinical evaluation is required to determine whether ITCL failure is reliably detectable.

Role of passive structures in the mobility and stability of the human subtalar joint: a literature review

The subtalar joint plays a fundamental role in the transmission of loads between the leg and the foot. Although anatomical structures of this joint have been described extensively, much ambiguity about their location, shape, and function still persists. There is also disagreement regarding mobility, for example, whether the joint can be considered a hinge, screw-like, or a multiaxial joint. The most relevant studies from the literature are reported and the main experimental observations discussed. Recent studies have described the subtalar joint as a structure with no degrees of unresisted freedom, i.e., motion from the single neutral position is attained only by deformation of the ligaments and of the articular surfaces.

Subtalar instability. Etiology, diagnosis, and management

Subtalar instability is an evolving disorder that seems to cause a portion of chronic hindfoot instability. It can be seen as an isolated problem, or more commonly, in combination with ankle instability. There seems to be many injury mechanisms, most of which seem to involve supination of the hindfoot, and all seem to attenuate the lateral ligaments of the ankle and subtalar joints. As the condition progresses, and additional sprains occur as a result of the alteration in subtalar joint mechanics, the remaining ligaments become attenuated. There are many methods described to diagnose subtalar instability, but no conclusive test has been devised. Thus, the diagnosis must be inferred from an accurate history, physical examination, conferring radiographic studies, and failure of nonoperative management (often, for ankle instability). As with other hindfoot injuries, many patients improve with conservative measures. These measures are early (ice and immobilization) and late (bracing and proprioceptive training). When patients do not improve or cannot tolerate bracing, recent studies have shown there is a role for ligamentous reconstruction. Most procedures attempt to recreate the lateral ligament structures, including the calcaneofibular, the cervical, and the interosseous talocalcaneal ligaments, which seem to have the best stabilizing effect on the hindfoot. With the advent of newer procedures and more aggressive surgical management, there may be a role for early anatomic repair and rehabilitation.

Elongation behavior of calcaneofibular and cervical ligaments in a closed kinetic chain: pathomechanics of lateral hindfoot instability

Numerous reconstructive procedures are performed to correct both ankle and subtalar instability after trauma although the precise pathology which results in this chronic instability and pain is not yet known. This study examined the role of the calcaneofibular (CLFL) and cervical ligaments (CRVL) during physiologic loading and demonstrated the effect of CLFL deficiency on the CRVL. Talar and subtalar tilt as well as inversion range of motion before and after CLFL sectioning were studied. Eleven osteoligamentous fresh frozen cadaver legs were used in which each foot was taken through six positions: neutral, 35 degrees plantarflexion, dorsiflexion, inversion, plantarflexion-inversion, and dorsiflexion-inversion. The CLFL and CRVL stretched the greatest in dorsiflexion-inversion. The most interesting finding was that the CRVL was elongated relative to neutral in all other test positions of the foot. However, the CLFL was shortened relative to neutral in plantarflexion and plantarflexion-inversion. In the CLFL deficient state, CRVL ratios demonstrated significant increases in length of the CRVL. Talar tilt increased on average more than 9 degrees with CLFL deficiency (p < 0.008) while subtalar tilt did not change significantly. The maximum tibiocalcaneal angle, recorded for dorsiflexion-inversion, increased more than 5 degrees after sectioning the CLFL (p < 0.05).

Tarsal Sinus: Arthrographic, MR Imaging, MR Arthrographic, and Pathologic Findings in Cadavers and Retrospective Study Data in Patients with Sinus Tarsi Syndrome

PURPOSE

To evaluate the tarsal sinus by using different imaging techniques and specialized planes.

MATERIALS AND METHODS

Magnetic resonance (MR) imaging of the tarsal sinus was performed in 10 cadavers. Conventional arthrography of the anterior and posterior subtalar joints was then performed. Tarsal sinus ligaments were evaluated further on initial and reconstructed MR arthrograms along and perpendicular to their axes. Pathologic correlation was performed in five specimens suspected of having tarsal sinus lesions on the basis of initial imaging findings. In 37 patients with a clinical diagnosis of sinus tarsi syndrome, MR images of the ankle were obtained before and after intravenous gadolinium-based contrast material administration and were reviewed to verify the integrity of the tarsal sinus ligaments.

RESULTS

Two complete and three partial cervical ligament (CL) tears and one complete interosseous talocalcaneal ligament (ITCL) tear were diagnosed with MR imaging. Only one complete and one partial CL tear were seen after evaluation of both initial and reconstructed MR arthrograms and confirmed with pathologic correlation. In 18 patients, the diagnosis was confirmed at MR imaging, which depicted ITCL and CL tears in 11 patients, isolated CL tears in three patients, ganglia in three patients, and pigmented villonodular synovitis in one patient.

CONCLUSION

Cadaveric study results indicate that initial and reconstructed MR arthrograms along and perpendicular to the ligament axes are potentially useful for further evaluation of individual tarsal sinus structures.

Variations of anatomical elements contributing to subtalar joint stability: intrinsic risk factors for post-traumatic lateral instability of the ankle?

Ankle sprains are frequently followed by chronic lateral instability, often with talar hypermobility. This might be due to subtalar instability. Among intrinsic risk factors, anatomical variants are generally overlooked. In the subtalar region, anatomical variation is particularly frequent. On the talus as well as on the calcaneus, the anterior articular facets may be missing or fused with the medial facets, giving rise to three subtalar joint configurations: a three-joint configuration, a fused configuration with a relatively large anteromedial joint, and a two-joint configuration without anterior joint. Osteometry was performed on these joint facets (134 calcanei, 122 tali), demonstrating significant differences in the surface of these configurations and the existence of a supplementary supporting surface with grossly transverse orientation in the three-joint configuration. There are also several variants of stabilizing ligaments within the sinus tarsi. Some of these configurations might expose to increased risk of associated subtalar lesions, resulting in subtalar instability. A systematic look for these variants is recommended in order to evaluate the associated risk factors, eventually resulting in a better understanding, prevention and cure of sequellae.

Influence of the interosseous talocalcaneal ligament injury on stability of the ankle-subtalar joint complex--a cadaveric experimental study

The present study aims to clarify the influence of the interosseous talocalcaneal ligament (ITCL) injury associated with injury to the lateral ankle ligaments on the ankle-subtalar joint complex motion under conditions of physiologic loading. We conducted mechanical tests using five fresh cadaveric lower extremities. Each specimen was mounted in the loading device and an axial cyclic load from 9.8 to 686 N was applied. Three-dimensional rotations of the ankle and the subtalar joint were measured simultaneously by a linkage electric goniometer. Mechanical tests were repeated after sectioning of the anterior talofibular ligament (ATFL), and again after additional sectioning of the ITCL. In the intact condition, the ankle and the subtalar joints rotated consistently with increase of the load. The predominant rotations were plantar flexion and adduction at the ankle joint, with some eversion demonstrated at the subtalar joint. Although ATFL sectioning did not significantly change the motion of the two joints, additional sectioning of the ITCL significantly increased adduction and total rotation of the ankle joint. The present study demonstrated that a combined injury of the ATFL and the ITCL can induce anterolateral rotatory instability of the ankle joint under conditions of axial loading.

Elongation behavior of calcaneofibular and cervical ligaments during inversion loads applied in an open kinetic chain

The cervical ligament plays a significant role in lateral stability of the subtalar joint but has received little attention compared with other ankle and subtalar joint ligaments. The purpose of this research was twofold. First, the elongation behavior of the cervical ligament was assessed with the calcaneofibular ligament intact and cut during two different types of inversion loads (manual and mechanical). Second, inversion range of motion was determined concomitantly with inversion loading and the difference in inversion range of motion between the calcaneofibular ligament intact to cut state was compared. The mean elongation of the cervical ligament with the calcaneofibular intact was 0.58 mm (+/- 0.33 mm) and 0.46 mm (+/- 0.23 mm) for manual and mechanical methods, respectively, and 0.88 mm (+/- 0.37 mm) and 0.78 mm (+/- 0.37 mm), respectively, for the same methods in the absence of the calcaneofibular ligament. This difference was statistically significant (P < 0.05 manually and P < 0.02 mechanically). An average increase in the inversion range of motion was noted with both methods [7.5 degrees manually (+/- 2.75 degrees) and 7.7 degrees mechanically (+/- 2.95 degrees)] after lesioning of the calcaneofibular ligament. This difference was statistically significant (P < 0.001) for both manual and mechanical range of motion testing. The results of this study indicate that there is a significant increase in elongation of the cervical ligament in the absence of the calcaneofibular ligament during manual and mechanically applied inversion loads in a open kinetic chain. Clinical and theoretical implications of this data are discussed.

Subtalar joint stability. Talocalcaneal interosseous ligament function studied in cadaver specimens

We used 6 fresh-frozen foot specimens to evaluate the contribution of the talocalcaneal interosseous ligament (IOL) in stabilizing the subtalar (talocalcaneal) joint. The tibia and ankle joint were secured, and the calcaneus was subjected to a bending and axial force applied circumferentially. The position of the calcaneus relative to the talus was monitored with a magnetic tracking system. Motion was recorded at every half degree in the 0 degree to 360 degrees arc before and after sectioning of the IOL. The results in the intact feet indicated that, with circumferential loading of the subtalar joint, there were two stable zones (supination stable zone, pronation stable zone) during which little displacement occurred and two transition zones during which the supination and pronation movement occurred. There was a greater degree of supination displacement after IOL sectioning (p = 0.008), but no pronation displacement. The IOL contributed substantially to subtalar joint stability, particularly in supination.

Anatomic and MRI study of the subtalar ligamentous support

The diagnosis of subtalar instability remains difficult both clinically and radiographically. The authors present an anatomic and MRI study of the subtalar ligamentous support. The anatomic study has consisted in dissections and sections of cryoconserved hindfeet (15 cases) which precises the organisation of ligamentous bundles in the lateral (sinus tarsi) and central (canalis tarsi) subtalar compartments, mainly represented by the trilayered inferior extensor retinaculum, the cervical talo-calcaneal ligament and the interosseous talo-calcaneal ligament. MRI study (1.5 tesla) of anatomic specimens was performed according to defined types of sections: sagittal, coronal, coronal oblique, axial transverse. The correlations of anatomic and MRI sections allowed a precise interpretation of the subtalar ligamentous support as anatomically described. A complementary clinical MRI study was performed which allowed the validation of "the inversion test": this test optimizes the visualization of the different ligamentous structures. Relative to the difficulties of conventional imaging procedures, MRI appears of clinical relevance in the diagnosis of subtalar instabilities. This technique allows direct visualization of ligaments (or their rupture) and therefore a better evaluation of subtalar involvement in ankle sprain. This paper present a functional concept in MRI articular ligamentous restraints concern.

Sectional anatomy of connective tissue structures in the hindfoot of the newborn child and the adult

BACKGROUND

The knowledge of the normal anatomy of the newborn hindfoot is essential for the understanding of foot deformities. In the present study, we investigated tendons, ligaments, and soft tissue structures in the newborn foot.

METHODS

The sectional anatomy of eight newborn feet was studied in 300-500-microns-thick sections processed by plastination histology. For comparison, 3-5-mm-thick plastinated sheets of adult feet were investigated.

RESULTS

Our specimens show obvious differences of the newborn compared with the adult foot. In the subcutaneous adipose tissue, the heel pad and the fat pad of the Achilles tendon and the relative size and topography of adipose tissue pads are different. Moreover, the course of the flexor hallucis tendon and the insertion pattern of the Achilles tendon are distinct. Finally, there are differences in the course and in the relative length of some plantar ligaments.

CONCLUSIONS

Our data reveal that the differences between the newborn foot and the adult foot result mainly from the different shape and position of the tarsal bones. Our findings are of clinical importance for the evaluation of magnetic resonance imaging in the normal infant's foot and in foot deformities.

Arthroscopy of the subtalar joint

The purpose of this study was to determine the position and relative safety of the anterior, posterior, and newly defined middle portals by measuring their distance from the neurovascular structures and tendons on the lateral side of the foot and ankle. Furthermore, this study demonstrates specific components of the posterior subtalar joint and arthroscopic access to each utilizing a technique that allows direct anatomic correlation. The 15 specimens were divided into three groups of five feet each, with one arthroscopic portal site and one instrumentation portal site per group. Group I used the anterior portal for the arthroscope and the posterior portal for the curette. Group II used the posterior portal for the arthroscope and the anterior portal for the curette. In group III, the arthroscope was inserted through the anterior portal and the curette through the middle portal. The sural nerve and small saphenous vein were at risk with posterior portal placement. The anterior portal presented a minor risk of injury to the dorsal intermediate cutaneous branch of the superficial peroneal nerve. The middle portal was without risk to surrounding structures. Group I provided the best access to the posterior facet of the subtalar joint. Group II provided excellent arthroscopic visualization of the posterior facet, but poor access for instrumentation via the anterior portal. Group III provided the best access to the sinus tarsi. No combination of portals allowed visualization or instrumentation of the middle or anterior facets.