Interosseous Talocalcaneal Ligament Research Articles

Arthroscopic surgery for treatment of sinus tarsi syndrome

Objective To investigate the result of arthroscopic surgery in the treatment of sinus tarsi syndrome. Methods The study involved 15 patients (6 males and 9 females) with sinus tarsi syndrome admitted to First Hospital of Nanjing from July 2006 to May 2008. The age of the patients ranged from 23 to 63 years ( average 46.3 years). All the patients had one side involvement, including 10 patients with left side involvement and five with right side involvement. All the operations were performed under the tourniquet control and the patients were placed at the lateral decubitus position. The lateral, anterolateral and posterolateral portals were applied intraoperatively and the medial portal was applied when necessary. Visual analogue scale (VAS) and American orthopedic foot and ankle scale (AOFAS) ankle-hindfoot scale were used for follow-up evaluation. Results More than two lesions were found under arthroscope in all patients. The lesions included scar tissue hypertrophy and inflammation in the sinus tarsal canal, soft tissue impingement in the subtalar joint, synovitis, partial tears of subtalar capsule, interosseous talocalcaneal ligament or cervical ligament, cartilage injury and subtalar degeneration. All patients were followed up for 19-35 months (mean 26. 1 months). At the final follow-up, the VAS score was improved from preoperative 7.6 points ( range 6-9 points) to postoperative 2.5 points (range 1-4 points) (P＜0.01 ), and the AOFAS score improved from preoperative 41. 9 points (range 20-67 points) to postoperative 83. 1 points ( range 70-100 points) ( P ＜ 0. 01 ). The excellence rate of the AOFAS score reached 73% at the final follow-up. Conclusion For patients with sinus tarsi syndrome after a failed conservative treatment, arthroscopic surgery should be performed as soon as possible and the clinical result is satisfactory. Key words: Subtalar joint; Ankle injuries; Arthroscopy

Portal safety and efficacy of anterior subtalar arthroscopy: a cadaveric study

Anterior subtalar arthroscopy was performed in 14 feet of 7 cadaveric bodies using the primary visualization and working portals. The cartilage of the anterior/middle calcaneal facet that can be reached was marked. The feet were dissected and the distances between the portals and surrounding cutaneous nerves were measured. Any damage to the ligaments of the sinus tarsi was noted. The percentage area of the articular cartilage that was marked was measured. In all specimens, the primary visualization portal tract passed through the lateral root of the inferior extensor retinaculum. The primary working portal tract passed through the lateral root in nine specimens (64%). Cervical ligament was intact in all specimens. In three specimens (21%), the primary visualization portal tract passed through the posterior edge of the intermediate root of the inferior extensor retinaculum. The interosseous talocalcaneal ligament was intact in all specimens. The primary visualization portal tract passed through the medial root of the inferior extensor retinaculum in eight specimens (57%). The primary working portal tract passed through the medial root of the inferior extensor retinaculum in one specimen. The average working area on the calcaneal facet was 95% +/- 4% of the total articular surface. There was no case of nerve injury in all specimens. In conclusion, anterior subtalar arthroscopy is a minimally invasive approach to deal with pathologies of this joint without the need of extensive resection of the ligamentous structures of the sinus tarsi.

Mechanical Stability of the Subtalar Joint After Lateral Ligament Sectioning and Ankle Brace Application

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° ± 11.8° compared with 35.7° ± 6.0° 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° ± 7.3°) 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.

The ligaments and articular surfaces of the talocalcaneal joint: a cadaveric study

IntroductionThe articulation between the talus and the calcaneus, the subtalar joint, is important in chronic ankle instability. The relationship between the ligaments and the articular surfaces of this joint has not been thoroughly discussed in the literature. This study aims to describe and quantify the relationship between the morphology and attachments of the interosseous talocalcaneal ligament (ITCL) and the total surface area and configuration of the joint facets on the calcaneus.Methods20 subtalar joints from embalmed cadavers will be dissected and distracted. Measurements of the ITCL and the joint facets on the calcaneus will be reported.ResultsPreliminary results suggest a positive correlation between thickness of ITCL and total surface area of the talar facets on the calcaneus.DiscussionSubtalar joint instability may contribute to recurrent ankle sprains. Knowledge of the ligaments and articular surfaces of the joint is critical for effective diagnosis and treatment. Reconstruction of the ITCL could be crucial in the treatment of chronic ankle instability. Precise information about the morphology, attachments and relationship of the ITCL to the joint facets is necessary to maximize the positive results of reconstructive surgery. This work was supported by the Anatomy & Cell Biology Department at the University of Western Ontario and the Ontario Graduate Scholarship program.Grant Funding SourceOGS

Efficacy of MRI Versus Arthroscopy for Evaluation of Sinus Tarsi Syndrome

Magnetic resonance imaging (MRI) has been used to diagnose sinus tarsi syndrome (STS) because of its non-invasiveness and accuracy. The purpose of the present study was to evaluate the diagnostic efficiency of MRI compared with subtalar arthroscopy for STS. Twenty-eight patients (30 feet) who had undergone both MRI and subtalar arthroscopy for STS were evaluated. MRI results were compared with arthroscopic findings, which were considered the standard. Sensitivity, specificity, and positive and negative predictive values were calculated, and correlations between MRI and arthroscopic findings were investigated. MRI was found to detect interosseous talocalcaneal ligament (ITCL) tears, cervical ligament (CL) tears, sinus tarsi fat alterations, and synovial thickening, with sensitivities, specificities, positive and negative predictive accuracies of: 44%, 60%, 85%, 18% (ITCL tears); 73%, 89%, 80%, 86% (CL tears); 71%, 92%, 93%, 71% (sinus tarsi fat alterations); and 86%, 87%, 67%, 95% (synovial thickening). Correlations between MRI and arthroscopic findings showed full agreement in 10%, partial agreement in 50%, and no agreement in 40%. MRI is useful for detecting CL tears, sinus tarsi fat alterations, and synovial thickening, but is inadequate for correctly detecting ITCL tears.

Subtalar Arthroscopy for Sinus Tarsi Syndrome: Arthroscopic Findings and Clinical Outcomes of 33 Consecutive Cases

The purposes of this study were to identify the pathologic findings of sinus tarsi syndrome (STS) by subtalar arthroscopy and to evaluate the results of arthroscopic treatments in 33 consecutive cases. A retrospective review was performed in 31 consecutive patients (33 cases) who underwent subtalar arthroscopic treatment for STS. The mean follow-up duration was 24 months (range, 18 to 36 months). Patients were evaluated by use of arthroscopic findings (recorded on videotapes and photographs) and clinical outcomes, which included visual analog scale and American Orthopaedic Foot and Ankle Society ankle-hindfoot scores. Arthroscopic findings showed partial tear of the interosseous talocalcaneal ligament in 29 cases (88%), synovitis in 18 (55%), partial tear of the cervical ligament in 11 (33%), arthrofibrosis in 8 (24%), and soft-tissue impingement in 7 (21%). The mean visual analog scale score improved from 7.3 points (range, 6 to 9 points) preoperatively to 2.7 points (range, 1 to 4 points) postoperatively (P < .005), and the mean American Orthopaedic Foot and Ankle Society ankle-hindfoot score improved from 43.1 points (range, 21 to 65 points) preoperatively to 86.2 points (range, 72 to 100 points) postoperatively (P < .005). Of the cases, 16 (48%) had an excellent result, 13 (39%) had a good result, and 4 (12%) had a fair result. Subtalar arthroscopy identified pathologies in the subtalar joint in patients with STS and showed that treatment of these pathologies led to improved function. Level IV, therapeutic case series.

Is It Hazardous or Mandatory to Release the Talocalcaneal Interosseous Ligament in Clubfoot Surgery?

Extreme overcorrection and avascular necrosis are recognized complications in clubfoot surgery and are thought to be the result of division of the talocalcaneal interosseous ligament (TCIL). This is a preliminary report of a prospective study of the cases of 46 patients with 66 idiopathic clubfeet treated by means of soft tissue release using a posteromedial approach at a mean age of 9 months. The deformity was very severe in 51 feet and severe in 15. The feet were divided into 2 equal groups (33 feet each). In group A feet, the TCIL was released, whereas in group B, the ligament was left intact. At a mean follow-up period of 28 months, the result was satisfactory (excellent and good) in 96.9% of feet in group A and in 87.9% of feet in group B. When the mean overall clinical and radiological score was investigated, group A graded excellent whereas group B graded good. In feet with satisfactory outcome, group A showed statistically significant improvement of the anteroposterior and lateral talocalcaneal angles, talocalcaneal index, and lateral calcaneus-first metatarsal angles when compared with group B. This was reflected clinically on better hind foot correction with the release of the TCIL, with no evidence of significant overcorrection. Magnetic resonance imaging of the ankle and foot confirmed no evidence of talar avascular necrosis or extreme overcorrection in 40 feet (60.1%), 20 in each group. We conclude that it is advisable to release the TCIL in severe and very severe clubfeet.

Arthroscopic Subtalar Release of Post-traumatic Subtalar Stiffness

We describe an arthroscopic approach of subtalar release for post-traumatic subtalar stiffness that can allow early postoperative vigorous mobilization. The patient is placed in the lateral position. Subtalar arthroscopy is performed via the standard anterolateral portal at the angle of Gissane, the middle portal just distal and anterior to the tip of the lateral malleolus, and the posterolateral portal at the vertical limb of the old surgical scar, just above the posterosuperior tubercle of the calcaneus. Arthroscopic subtalar release is performed in stages. First, the fibrous bands at the sinus tarsi are debrided. The most lateral part of the interosseous talocalcaneal ligament is released. The dense fibrous tissue of the lateral subtalar gutter is then cleared. Most of the time, the subtalar motion gained at this stage is insignificant. At the second stage, the posterior capsule can be released and the fibrous tissue at the posterior corner of the joint can be debrided. Finally, the lateral subtalar capsule and lateral subtalar ligamentous structures are stripped from the lateral calcaneal cortical surface. Stripping should be done beyond the old surgical scar to release the adhesion of the surgical scar to the lateral calcaneal wall.

Anatomy of Ligamentous Structures in the Tarsal Sinus and Canal

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. 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. 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. 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.

Lateral swivel dislocation of the talo-navicular joint

A swivel dislocation is an uncommon variant of a sub-talar dislocation, where a medially or laterally directed force dislocates the talo-navicular joint, and subluxates but does not dislocate the subtalar joint. The calcanuem rotates or swivels on an intact interosseous talocalcaneal ligament without tearing it. It is important to recognise this injury as its treatment and prognosis differs form a subtalar dislocation. A case of lateral swivel dislocation of the talo-navicular joint treated by closed reduction and percutaneous wire fixation is reported. Excellent clinical and functional outcome were achieved.

Posterior Tibial Tendon Insufficiency: Which Ligaments are Involved?

The pathology manifested in posterior tibial tendon insufficiency (PTTI) is not limited to the posterior tibial tendon. The association of ligament failure with deformity has been discussed in numerous publications, but extensive documentation of the structures involved has not been performed. The purpose of this observational study was to identify the pattern of ligament involvement using standardized, high-resolution magnetic resonance imaging (MRI) in a series of 31 consecutive patients diagnosed with PTTI compared to an age matched control group without PTTI. The structures evaluated by MRI were the posterior tibial tendon, superomedial and inferomedial components of the spring ligament complex, talocalcaneal interosseous ligament, long and short plantar ligaments, plantar fascia, deltoid ligament, plantar naviculocuneiform ligament, and tarsometatarsal ligaments. Structural derangement was graded on a five-part scale (0 to IV) with level 0 being normal and level IV indicating a tear of more than 50% of the cross-sectional area of the ligament. Standard flatfoot measurements taken from preoperative plain standing radiographs were correlated with the MRI grading system. Statistically significant differences in frequency of pathology in the PTTI group and controls were found for the superomedial calcaneonavicular ligament (p < 0.0001), inferomedial calcaneonavicular ligament (p < 0.0001), interosseous ligament (p = 0.0009), anterior component of the superficial deltoid (p < 0.0001), plantar metatarsal ligaments (p = 0.0002) and plantar naviculocuneiform ligament (p = 0.0006). The ligaments with the most severe involvement were the spring ligament complex (superomedial and inferomedial calcaneonavicular ligaments) and the talocalcaneal interosseous ligament. Ligament involvement is extensive in PTTI, and the spring ligament complex is the most frequently affected. Because ligament pathology in PTTI is nearly as common as posterior tibial tendinopathy, treatment should seek to protect or prevent progressive failure of these ligaments.

The role of the interosseous talocalcaneal ligament in subtalar joint stability.

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. 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. 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). 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. 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.

Effect of arch supports on ankle-subtalar complex instability: a biomechanical experimental study.

Subtalar instability, which may cause persistent symptoms after severe inversion ankle sprains, often involves failure of the interosseous talocalcaneal ligament (ITCL). While several clinicians have reported surgical treatment for this pathology, nonsurgical management policy has not been well considered. Previously, it was proposed that ITCL failure possibly causes looseness of the tarsal arch construction resulting in abnormal ankle-subtalar kinematics occurring with axial forces. In the current study the author hypothesized that arch-support insole functions to improve abnormal joint kinematics in ankle-subtalar complex instability. Five fresh-frozen cadaver lower extremities with simulated ankle-subtalar complex instability, which was created by combined sectioning of the anterior talofibular ligament (ATFL) and the ITCL, were subjected to a biomechanical experiment. Cyclic axial loading from 9.8 to 668 N was applied with a material testing machine, while three-dimensional angular displacements in both the ankle and subtalar joints were determined with electric goniometers. The specimens were tested before and after inserting an arch-support insole that supports the medial-longitudinal and transverse arches of the foot. Inserting the insole decreased the maximum ankle internal rotation, from 3.3 degrees +/- 0.9 degrees to 2.3 degrees +/- 0.4 degrees (p = .028), while subtalar rotation was not significantly changed. The medial longitudinal arch-support insole reduced abnormal ankle internal rotation created by combined sectioning of the ATFL and ITCL, likely due to improved arch configuration stability.

Surgical aspects of the hindfoot MR anatomy

The extent of soft tissue trauma in hindfoot injury (calcaneus fracture, talus fracture) is currently being underestimated. A standardization of magnetic resonance (MR) imaging of the hindfoot is necessary for better definition of pathological changes. Standardized MR imaging projections of the hindfoot were illustrated by anatomic analysis of specimen sections using the same sectional plane as in MR imaging. The plastinated sections were obtained from the same specimen that had been scanned previously. MR imaging of the hindfoot enables the assessment of the calcaneocuboid ligament, the interosseous talocalcaneal ligament, trauma of the foot sole, intraosseous and extraosseous vascularization, muscle compartments in the evaluation of compartment syndrome, chondrai flake fractures, tendon dislocation, as well as tendon degeneration, and plantar fasciitis. These anatomical structures, which must be evaluated for preoperative planning, can be identified clearly by MR imaging.

Tarsal sinus: arthrographic, MR imaging, MR arthrographic, and pathologic findings in cadavers and retrospective study data in patients with sinus tarsi syndrome.

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

Computer-assisted assessment of lateral column movement following plantar fascial release: A cadaveric study

In patients who fail conservative treatment, releasing the plantar fascia relieves heel pain but destabilizes the lateral column of the foot. After surgery, pain can present in the area of the sinus tarsi, extensor digitorum brevis muscle, between the fourth and fifth metatarsals, and at the calcaneocuboid joint. The precise mechanism and involved structures for this painful compensation remains unclear. The authors hypothesized that the lateral plantar fascial band, bifurcate and cervical ligaments, lateral talocalcaneal ligament, and interosseous talocalcaneal ligament become excessively strained after this surgery. Using eight cadaver lower extremity limbs amputated 7 cm above the ankle joint, structural changes in the foot in response to staged release of the plantar fascia were measured. All ligament, tendon, and osseous structures were exposed along the plantar, medial, and lateral aspects of the foot and ankle. Using a servohydraulic system, compressive loads in increasing increments (50 lbs) were applied along the tibial axis. Tissue and bony structure displacement in the foot was measured using images electronically captured from two fixed cameras and a digital camera following each load change. All measurements were made in pixels and converted to millimeters in a spreadsheet program. Except for plantar fascial measurements, data were expressed as percentage of initial baseline. As expected, increasing compressive loads changed all measurements [repeated measures ANOVA, p<.04]. When releasing the plantar fascia, the inferior sinus tarsi space widened (intact, 85.4+/-10.8%; 1/4 release, 87.7+/-13.0; 1/2 release, 88.3+/-9.2; 3/4 release, 91.2+/-8.8; p<.04). Lateral length increased and medial height decreased, while medial length and lateral height were unchanged as the fascia was sequentially released. Significant movement of the inferior sinus tarsi strained the bifurcate and cervical ligaments, the lateral talocalcaneal ligament, and interosseous talocaneal ligament, which may account for pain following surgery. The initial 1/4 cut of the plantar fascia exerted the greatest mechanical alteration of the foot, suggesting that a partial release may relieve heel pain while optimizing the patient's chances of maintaining structural integrity with 75% of the plantar fascia intact.

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.

Stability of the Arch of the Foot

We defined the relative contributions of six ligaments in stabilizing the arch of the foot: plantar aponeurosis, long-short plantar ligaments, plantar calcaneonavicular ligament (spring ligament), medial talocalcaneal ligament, talocalcaneal interosseous ligament, and tibionavicular portion of the deltoid ligament. Nineteen fresh-frozen human foot specimens were used. A load of 445 N was applied axially to simulate standing-at-ease posture. Three-dimensional positions of tarsal bones before and after ligament sectioning were determined with the use of a magnetic tracking device. The motions were presented in the form of screw axis displacements, quantitating rotation, and axis of rotation orientation. After sectioning one structure, the arch did not collapse on any specimen and there was no obvious change by visual inspection. There were, however, measurable changes in tarsal bone position. Metatarsal-to-talus total rotation difference was greatest with spring ligament and deltoid ligament sectioning, with an average of 2.1 degrees +/- 1.7 degrees and 2.0 degrees +/- 0.2 degree difference, respectively. Calcaneus-to-talus rotation difference was greatest with talocalcaneal interosseous ligament sectioning, with an average of 1.7 degrees +/- 1.5 degrees. The spring ligament, deltoid ligament, and talocalcaneal interosseous ligament were most important for arch stability.

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.

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.