The effect of osseous ankle configuration on chronic ankle instability

Skeletal Features of Talus in Hepple V Lesion

The present study was to determine the characteristics of the ankle skeletal structure in patients with talus Hepple V type. We conducted a retrospective study on the skeletal structure of the talus in 110 patients with Hepple V osteochondral lesions of the talus and in control participants. The radiographic measurements taken include the following: in the coronal plane - depth of talus frontal curvature, length of the lateral and medial malleolus; in the sagittal plane - radius and height of talus, angle of tibial lateral surface, tibiotalar sector, and vertical neck angle. The osteochondral lesion of the talus showed a significantly larger mean radius (mean ± SD, 21.4 ± 2.5 mm; p < .001) and height (mean ± SD, 26.0 ± 2.7 mm; p < .005). It also demonstrated a longer mean medial malleolus length (mean ± SD, 15.7 ± 2.4 mm; p < .005), a larger mean vertical neck angle (mean ± SD, 86.2 ± 5.4°; p < .050), and a greater mean tibial lateral surface angle (mean ± SD, 80.0 ± 4.5°; p < .001). And there was a greater mean frontal curvature depth (mean ± SD, 3.9 ± 0.6 mm; p < .005). Overall, this study found that patients with Hepple V osteochondral lesions of the talus had a larger vertical neck angle and tibial lateral surface angle, a longer talus radius and medial malleolus length, a higher talus height, and a deeper frontal curvature depth. STUDY DESIGNS: Retrospective Case-Control Study.

A Smaller Tibiotalar Sector Is a Risk Factor for Recurrent Anterolateral Ankle Instability after a Modified Broström-Gould Procedure

BACKGROUND

Several demographic and clinical risk factors for recurrent ankle instability have been described. The main objective of this study was to investigate the potential influence of morphologic characteristics of the ankle joint on the occurrence of recurrent instability and the functional outcomes following a modified Broström-Gould procedure for chronic lateral ankle instability.

METHODS

Fifty-eight ankles from 58 patients (28 males and 30 females) undergoing a modified Broström-Gould procedure for chronic lateral ankle instability between January 2014 and July 2021 were available for clinical and radiological evaluation. Based on the preoperative radiographs, the following radiographic parameters were measured: talar width (TW), tibial anterior surface (TAS) angle, talar height (TH), talar radius (TR), tibiotalar sector (TTS), and tibial lateral surface (TLS) angle. The history of recurrent ankle instability and the functional outcome using the Karlsson Score were assessed after a minimum follow-up of 2 years.

RESULTS

Recurrent ankle instability was reported in 14 patients (24%). The TTS was significantly lower in patients with recurrent ankle instability (69.8 degrees vs 79.3 degrees) (P < .00001). The multivariate logistic regression model confirmed the TTS as an independent risk factor for recurrent ankle instability (OR = 1.64) (P = .003). The receiver operating characteristic curve analysis revealed that patients with a TTS lower than 72 degrees (=low-TTS group) had an 82-fold increased risk for recurrent ankle instability (P = .001). The low-TTS group showed a significantly higher rate of recurrent instability (58% vs 8%; P = .0001) and a significantly lower Karlsson score (65 points vs 85 points; P < .00001).

CONCLUSION

A smaller TTS was found to be an independent risk factor for recurrent ankle instability and led to poorer functional outcomes after a modified Broström-Gould procedure.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Morphological features of the non-affected side of the hindfoot in patients with unilateral varus ankle osteoarthritis

BACKGROUND

The innate shape characteristics of the hindfoot bones alter the loading conditions of the foot and thus may be associated with an increased risk of developing varus ankle osteoarthritis (OA). This study aimed to clarify the innate morphological patterns of the hindfoot bones that may be associated with ankle OA by analyzing the differences between the bone morphology of the non-affected side of patients with unilateral varus ankle OA and that of healthy participants.

METHODS

In this case-control study, computed tomography images were used to develop three-dimensional models of three hindfoot bones (distal tibia with fibula, talus, and calcaneus) from 23 non-affected sides of patients with radiography-diagnosed unilateral ankle OA and 22 healthy control participants. Anatomical and sliding landmarks were placed on the surface of each bone, and the principal components (PCs) of shape variation among specimens were independently calculated for each bone, preserving homology between individuals. The PC modes representing 5% or more of the overall variation were statistically compared between the ankle OA and control groups.

RESULTS

Significant differences were identified between the OA and control groups in the fifth PC mode for the tibia with fibula (proportion of variance, 5.1%; p =.025), fifth PC mode for the talus (6.7%, p =.031), and third PC mode for the calcaneus (7.4%, p =.001). The hindfoot bones of the participants who developed ankle OA had the following innate morphological characteristics: the lateral malleolar articular surface of the fibula was shifted superiorly, tibial plafond was enlarged posteroinferiorly, posterior width of the talar trochlea was narrower, talonavicular articular surface of the talus was oriented more frontally, anterior-middle talocalcaneal articular surfaces of the talus were more medially shifted and those of the calcaneus were flatter, calcaneal sustentaculum tali was less protruding, and lateral plantar process of the calcaneus was more superiorly positioned.

CONCLUSIONS

These distinctive morphological alterations may increase the incidence and progression of varus ankle OA through aberrant anterior translation, internal rotation, and varus tilting of the talus.

The morphology of osseous structure in subtalar joint with chronic ankle instability

BACKGROUND

Osseous structures have been demonstrated as risk factors for chronic ankle instability (CAI). Previously, the researchers only focused on the osseous structures of ankle, but ignored the osseous structures of subtalar joint(STJ). Accordingly, the aim of our study was to investigate the morphological characteristics of STJ osseous structures in CAI.

METHODS

52 patients with CAI and 52 sex- and age- matched control subjects were enrolled from The Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University. The lateral radiographs of ankle in weight-bearing were used to compare the diversity of the two groups. Specifically, The Length of calcaneus, Calcaneal facet height and Absolute foot height, Böhler's angle, Gissane's angle, Calcaneal inclination angle, Talocalcaneal angle, Tibiotalar angle, Tibiocalcaneal angle, Talar-horizontal angle, talar declination angle, facet inclination angle were gauged in the two groups.

RESULTS

The Böhler's angle, Calcaneal inclination, Talocalcaneal angle, Tibiotalar angle, Talar-horizontal angle, Talar declination angle, Facet inclination angle and Absolute foot height of CAI group were significantly higher than normal control group (P < 0.05). There were no significant differences in Gissane's angle, Tibiocalcaneal angle, Length of calcaneus and Calcaneal facet height between patients with CAI and normal controls (P > 0.05).

CONCLUSIONS

The osseous structures of STJ in CAI patients are different from normal people in morphology. Therefore, we should pay more attention to the changes of STJ anatomical parameters in the diagnosis and prevention of CAI.

LEVEL OF EVIDENCE

Ⅲ.

Validation of a personalized ligament-constraining discrete element framework for computing ankle joint contact mechanics

BACKGROUND AND OBJECTIVE

Computer simulations of joint contact mechanics have great merit to improve our current understanding of articular ankle pathology. Owed to its computational simplicity, discrete element analysis (DEA) is an encouraging alternative to finite element analysis (FEA). However, previous DEA models lack subject-specific anatomy and may oversimplify the biomechanics of the ankle. The objective of this study was to develop and validate a personalized DEA framework that permits movement of the fibula and incorporates personalized cartilage thickness as well as ligamentous constraints.

METHODS

A linear and non-linear DEA framework, representing cartilage as compressive springs, was established, verified, and validated. Three-dimensional (3D) bony ankle models were constructed from cadaveric lower limb CT scans imaged during application of weight (85 kg) and/or torque (10 Nm). These 3D models were used to generate cartilage thickness and ligament insertion sites based on a previously validated statistical shape model. Ligaments were modelled as non-linear tension-only springs. Validation of contact stress prediction was performed using a simple, axially constrained tibiotalar DEA model against an equivalent FEA model. Validation of ligamentous constraints compared the final position of the ankle mortise to that of the cadaver after application of torque and sequential ligament sectioning. Finally, a combined ligamentous-constraining DEA model was validated for predicted contact stress against an equivalent ligament-constraining FEA model.

RESULTS

The linear and non-linear DEA model reproduced a mean articular contact stress within 0.36 MPa and 0.39 MPa of the FEA calculated stress, respectively. With respect to the ligamentous validation, the DEA ligament-balancing algorithm could reproduce the position of the distal fibula within the ankle mortise to within 0.97 mm of the experimental observed distal fibula. When combining the ligament-constraining and contact stress algorithm, DEA was able to reproduce a mean articular contact stress to within 0.50 MPa of the FEA calculated contact stress.

CONCLUSION

The DEA framework presented herein offers a computationally efficient alternative to FEA for the prediction of contact stress in the ankle joint, manifesting its potential to enhance the mechanical understanding of articular ankle pathologies on both a patient-specific and population-wide level. The novelty of this model lies in its personalized nature, inclusion of the distal tibiofibular joint and the use of non-linear ligament balancing to maintain the physiological ankle joint articulation.

Current Challenges in Chronic Ankle Instability: Review and Perspective

Chronic ankle instability (CAI) is common, disabling, and represents a significant socioeconomic burden. Current treatment options are not adequately efficacious. CAI is multifaceted, yet it is commonly addressed in terms of either mechanical instability or functional impairment. Both are inherently linked. Basic research must be conducted to foster reliable translational research encompassing both mechanical and functional aspects. A review was conducted to identify CAI risk factors for inclusion in future studies, and we offer here opinions and perspectives for future research.

The Relationship Between Fibular Notch Anatomy and ATFL Rupture

The anterior talofibular ligament (ATFL) is the first to be damaged during a lateral ankle sprain. Dynamic and static structures have been investigated to better understand ATFL rupture, but the predisposing factors have not been fully elucidated. This study aims to define the fibular notch version that can evaluate the position of the fibular notch relative to the tibia and investigate the relationship between the fibular notch version (FNV) and ATFL rupture. This study included 71 patients with isolated ATFL rupture diagnosed clinically and radiologically and 71 control patients without any foot or ankle pathologies. Anterior facet length (AFL), posterior facet length (PFL), anterior-posterior facet angle (APFA), fibular notch depth (ND), and FNV measurements were performed on axial magnetic resonance images (MRI). We defined FNV as a parameter that evaluates the fibular notch's relative position to the distal tibia. The mean FNV was 16.6^° ± 4.9^° in patients with ATFL rupture and 12.4^° ± 5.6^° in the control group; when both groups were compared, FNV measurements were significantly higher in patients with ATFL rupture (p = .002). The mean APFA was 123.9^° ± 10^° in the group with ATFL rupture and 129.7^° ± 7.8^° in the control group. When both groups were compared, APFA was significantly lower in patients with ATFL rupture (p = .014). There was no significant difference between the groups regarding AFL, PFL, and ND. A more posterior (retroverted) fibular notch and a lower fibular notch angle seem to be associated with higher rates of ATFL rupture.

Comparison of effect of wobble board training with and without cognitive intervention on balance, ankle proprioception and jump landing kinetic parameters of men with chronic ankle instability: a randomized control trial

Background

The aim of the present study was to compare the effect of a wobble board training (WBT) course with and without cognitive intervention (CI) on balance, ankle proprioception and jump-landing kinetic parameters in active men with chronic ankle instability (CAI).

Methods

Twenty-one active men in the age range of 18–25 years with CAI were randomly divided into three groups of WBT for five weeks as follows: with CI (n = 7); without CI (n = 7); control (n = 7). In this study, balance was evaluated by Y-Balance Test and Balance Error Scoring System, proprioception was evaluated as active and passive replication of 15-degree inversion angle and Maximum inversion angle minus 5-degrees, and single-leg jump-landing test was used for measurement of kinetic variables as pre-test and post-test in similar conditions.

Results

Post-test of both groups of WBT with and without CI showed a significant improvement in all variables compared to pre-test (p ≤ 0.05); however, in post-test, there was no significant difference in any of the variables between WBT groups with and without CI (p ≥ 0.05).

Conclusions

A course of WBT with and without CI leads to a significant improvement in balance, proprioception and jump-landing kinetic parameters, including time to stabilization and center of pressure displacement in active men with CAI. Although the WBT group with CI showed a greater improvement in mean than WBT group without CI, but the difference was not significant in any of the variables.

Trial registration

Retrospectively Registered. irict.ir Identifier: IRCT20200617047818N1 on 05–02-2021.

Difference in orientation of the talar articular facets between healthy ankle joints and ankle joints with chronic instability

Since both the talocrural and subtalar joints can be involved in chronic ankle instability, the present study assessed the talar morphology as this bone is the key player between both joint levels. The 3D orientation and curvature of the superior and the posteroinferior facet between subjects with chronic ankle instability and healthy controls were compared. Hereto, the talus was segmented in the computed tomography images of a control group and a chronic ankle instability group, after which they were reconstructed to 3D surface models. A cylinder was fitted to the subchondral articulating surfaces. The axis of a cylinder represented the facet orientation, which was expressed by an inclination and deviation angle in a coordinate system based on the cylinder of the superior talar facet and the geometric principal axes of the subject's talus. The curvature of the surface was expressed as the radius of the cylinder. The results demonstrated no significant differences in the radius or deviation angle. However, the inclination angle of the posteroinferior talar facet was significantly more plantarly orientated (by 3.5°) in the chronic instability group (14.7 ± 3.1°) compared to the control group (11.2 ± 4.9°) (p < 0.05). In the coronal plane this corresponds to a valgus orientation of the posteroinferior talar facet relative to the talar dome. In conclusion, a more plantarly and valgus orientated posteroinferior talar facet may be associated to chronic ankle instability.

Weightbearing Radiography and MRI Findings in Ankle Fractures

Background. Static weightbearing radiography can be used to assess stability in ankle fractures by measuring lateral talar shift (medial clear space; MCS). However, the correlation of a stable ankle joint under weightbearing load and the structural integrity of the deltoid ligament has not been shown. In this study, we assessed deltoid ligament integrity on magnetic resonance imaging (MRI) and correlated that with weightbearing and gravity stress test radiography. Methods. Thirty-four patients with supination external rotation II-IV (SER) fractures underwent MRI, weightbearing radiography, and gravity stress test. On MRI, the deep anterior and posterior tibiotalar deltoid, tibionavicular and tibiocalcaneal ligaments, as well as the syndesmosis were assessed as intact, partial rupture, or complete rupture. The MCS was measured as the distance between the lateral border of the medial malleolus and the medial border of the talus at the level of the talar dome on the mortise view. Results. Twenty-three patients suffered a deep anterior tibiotalar ligament rupture (16 partial; 7 complete) and 2 a deep posterior tibiotalar ligament tear (1 partial; 1 complete). For MCS on weightbearing radiography, no statistically significant differences were identified between any of the individual groups. With gravity stress radiography, only a complete tear of the tibiocalcaneal ligament showed a significantly higher MCS than a partial tear or intact tibiocalcaneal ligament (P < .005). No other ligament disruption showed a significant difference between the complete rupture versus intact or partial tear. Conclusion. Weightbearing radiography does not show much variation in terms of MCS even with ligamentous disruption and fibula fracture. The talus often centers itself underneath the tibia with weightbearing radiography.Levels of Evidence: Level III: Retrospective cohort study.

Prognostic factors in ankle sprains: a review

Ankle sprains are one of the most common musculoskeletal injuries, being the most frequent musculoskeletal trauma among athletes.

Most of these injuries are successfully treated conservatively; however, up to 70% of patients can develop long-lasting symptoms. Therefore, understanding prognostic factors for an ankle sprain could help clinicians identify patients with poor prognosis and choose the right treatment.

A suggested approach will be presented in order to positively identify the factors that should warrant a more aggressive attitude in the initial conservative treatment.

There are some prognostic factors linked to a better recovery and outcome; nevertheless, prognostic factors for full recovery after initial ankle sprain are not consistent.

Cite this article: EFORT Open Rev 2020;5:334-338. DOI: 10.1302/2058-5241.5.200019

Assessing mechanical ankle instability via functional 3D stress-MRI - A pilot study

BACKGROUND

Quantitative measurement of the mechanical deficit in chronic ankle instability (CAI) is difficult. Therefore, the distinction between functional (FAI) and mechanical ankle instability (MAI) as well as the evaluation of surgical techniques is difficult. This pilot study uses a novel method of functional 3-dimensional stress ankle-MRI to test its applicability for assessing mechanical ankle instability.

METHODS

We used a custom-built ankle arthrometer that allows a stepless positioning of the foot and an axial in situ loading with up to 500 N combined with a 3-dimensional MRI protocol. We assessed four parameters (3D cartilage contact area (CCA) fibulotalar, tibiotalar horizontal and vertical and intermalleolar distance) under six different conditions (neutral-null, plantarflexion-supination and dorsiflexion-pronation each with and without loading) in n = 10 individuals (7 suffering from MAI and 3 healthy controls).

FINDINGS

The MAI group showed a substantially increased reduction of lateral osseous constraint compared to healthy controls when the foot was positioned in plantarflexion-supination (CCA fibulotalar 69% vs. 30% in controls). The reduction of the weight bearing surface in plantarflexion-supination was also more pronounced (CCA tibiotalar horizontal -49% in MAI vs. -28% in controls).

INTERPRETATION

This novel technique is valuable for assessing mechanical ankle instability in the target population and has a potential clinical benefit for assessing the mechanical deficit of individual patients. Further studies are needed to provide evidence for a possible prognostic value of this novel technique.

Weight, BMI and stability are risk factors associated with lateral ankle sprains and chronic ankle instability: a meta-analysis

IMPORTANCE

Lateral ankle sprains (LAS) are common in the general population and may lead to chronic ankle instability (CAI). If patients at risk could be identified, they could receive adequate and on-time treatment.

OBJECTIVE

The purpose of the current review was to identify all reported intrinsic factors associated with sustaining a LAS or progressing to CAI after an initial sprain.

EVIDENCE REVIEW

PubMed, Embase, MEDline, Cochrane and PEDro were searched for studies published until July 2019. Articles were selected if they included intrinsic factors related to LAS or CAI, subjects of at least 16 years old, and contained a minimum of 10 patients and 10 controls. Studies were excluded if they concerned reviews or case reports, included patients with previous surgical interventions, concomitant injuries or joint pathology other than ankle instability. Quality of included studies was assessed using the Quality in Prognostic Studies tool and quality of evidence was assessed using the GRADEpro tool. In case outcomes were described by at least three studies, data were pooled and assessed by performing a meta-analysis. Based on the pooled data, either a fixed-effects model or random-effects model was selected to correct for the degree of heterogeneity.

FINDINGS

The search resulted in a total of 4154 studies. After title and abstract screening and subsequent full-text screening, 80 relevant studies were included. Results of the meta-analyses indicated that, compared with healthy controls, patients with LAS had a higher mean body mass index (BMI). In patients with CAI, a higher weight and a longer time to stabilise after performing a task (eg, jumping) were found compared with healthy controls. Other outcomes could not be compared using a meta-analysis due to heterogeneity in outcome measurement and the great number of different outcomes reported. Identification of the risk factors when patients present themselves after a LAS may help to determine which patients are at risk of recurrent sprains or developing CAI.

CONCLUSIONS AND RELEVANCE

Based on the findings in this review, a higher BMI, and a higher weight and neuromuscular stability deficits may be regarded risk factors for sustaining a LAS or developing CAI, respectively.

LEVEL OF EVIDENCE

III.

Typical Shape Differences in the Subtalar Joint Bones Between Subjects with Chronic Ankle Instability and Controls

Bone shapes, particularly those defining the subtalar joint (STJ), have not received much attention yet as a risk factor for developing chronic ankle instability (CAI) after sustaining a lateral ankle sprain (LAS). This study aimed to compare three-dimensional (3D) shape variations in the STJ bones within individuals with CAI and healthy controls. 3D statistical shape models (SSMs) of the STJ bones were built to describe the bone shape variations observed within a population consisting of 26 individuals with unilateral CAI and 26 healthy controls. Using the SSMs and analysis of covariance test, age- and gender-adjusted shape variations in the bones were compared within individuals with CAI and healthy controls. The mean age of the CAI patients (14 males and 12 females) and healthy controls (12 males and 14 females) was 29 (standard deviation [SD] = 11) and 36 years (SD = 11), respectively. Tali and calcanei did not significantly vary between ipsilateral CAI and their contralateral ankle. Two shape modes, one for the talus (p = 0.015, variations in the curvature of the talar lateral process and the inclination angle of the talar neck relative to the body) and one for the calcaneus (p = 0.003, variations in the medial and lateral tuberosities, and the contour of the anterior articular surface), described significant shape differences between the CAI patients and healthy controls. The CAI patients generally had flatter talar joint surfaces and a flattened calcaneal ground-contact surface. These findings suggest that specific bone shapes may increase the risk of developing CAI after sustaining a LAS. © 2019 The Authors. Journal of Orthopaedic Research^® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:1892-1902, 2019.

A flexion osteotomy for correction of a distal tibial recurvatum deformity

Aims

There is little information about how to manage patients with a recurvatum deformity of the distal tibia and osteoarthritis (OA) of the ankle. The aim of this study was to evaluate the functional and radiological outcome of addressing this deformity using a flexion osteotomy and to assess the progression of OA after this procedure.

Patients and Methods

A total of 39 patients (12 women, 27 men; mean age 47 years (28 to 72)) with a distal tibial recurvatum deformity were treated with a flexion osteotomy, between 2010 and 2015. Nine patients (23%) subsequently required conversion to either a total ankle arthroplasty (seven) or an arthrodesis (two) after a mean of 21 months (9 to 36). A total of 30 patients (77%), with a mean follow-up of 30 months (24 to 76), remained for further evaluation. Functional outcome, sagittal ankle joint OA using a modified Kellgren and Lawrence Score, tibial lateral surface (TLS) angle, and talar offset ratio (TOR) were evaluated on pre- and postoperative weight-bearing radiographs.

Results

Postoperatively, the mean score for pain, using a visual analogue scale, decreased significantly from 4.3 to 2.5 points and the mean American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score improved significantly from 59 to 75 points (both p < 0.001). The mean TLS angle increased significantly by 6.6°; the mean TOR decreased significantly by 0.24 (p < 0.001). Radiological evaluation showed an improvement or no progression of sagittal ankle joint OA in 32 ankles (82%), while seven ankles (18%) showed further progression.

Conclusion

A flexion osteotomy effectively improved the congruency of the ankle joint. In 30 patients (77%), the joint could be saved, whereas in nine patients (23%), the treatment delayed a joint-sacrificing procedure. Cite this article: Bone Joint J 2019;101-B:682–690.

Medial Ankle Instability: The Deltoid Dilemma

Diagnosis and treatment of medial ankle instability (MAI) are still controversial and poorly discussed in literature. The purpose of this review is to highlight different clinical presentations of MAI and develop a guide for its management. The deltoid ligament complex is injured more commonly than expected, because deltoid ligament injuries may either be isolated or occur in combination with other lesions, such as lateral ankle ligament injury, posterior tibial tendon insufficiency, osteochondral lesion, and others. The presence of a pes planovalgus deformity in a patient without posterior tibial tendon insufficiency may indicate MAI.

Diagnosis, treatment and prevention of ankle sprains: update of an evidence-based clinical guideline

This guideline aimed to advance current understandings regarding the diagnosis, prevention and therapeutic interventions for ankle sprains by updating the existing guideline and incorporate new research. A secondary objective was to provide an update related to the cost-effectiveness of diagnostic procedures, therapeutic interventions and prevention strategies. It was posited that subsequent interaction of clinicians with this guideline could help reduce health impairments and patient burden associated with this prevalent musculoskeletal injury. The previous guideline provided evidence that the severity of ligament damage can be assessed most reliably by delayed physical examination (4-5 days post trauma). After correct diagnosis, it can be stated that even though a short time of immobilisation may be helpful in relieving pain and swelling, the patient with an acute lateral ankle ligament rupture benefits most from use of tape or a brace in combination with an exercise programme.New in this update: Participation in certain sports is associated with a heightened risk of sustaining a lateral ankle sprain. Care should be taken with non-steroidal anti-inflammatory drugs (NSAIDs) usage after an ankle sprain. They may be used to reduce pain and swelling, but usage is not without complications and NSAIDs may suppress the natural healing process. Concerning treatment, supervised exercise-based programmes preferred over passive modalities as it stimulates the recovery of functional joint stability. Surgery should be reserved for cases that do not respond to thorough and comprehensive exercise-based treatment. For the prevention of recurrent lateral ankle sprains, ankle braces should be considered as an efficacious option.

Chronic Ankle Instability (Medial and Lateral)

Ankle ligament injuries are among the most frequent reasons for emergency consultations of athletes. A majority of these can be treated conservatively; however, up to 40% develop chronic ankle instability requiring surgical reconstruction to restore functionality.

Subtalar joint configuration on weightbearing CT scan

BACKGROUND

Standard values that describe the morphology of the subtalar (ST) joint have previously been obtained from cadaveric studies or by using conventional unloaded radiographs. It is known that these parameters differ significantly from those measured in vivo and in loaded images, limiting the diagnostic value of the previously published morphological parameters in the literature. However, the morphology of the ST joint clearly affects its function. The objective of this study was to determine the morphology of the posterior facet of the ST joint using loaded computed tomography (CT) images and to describe the different configurations found in asymptomatic patients.

METHODS

A weightbearing CT scan was performed on 59 patients without any history of hindfoot and ankle pathology. The shape of the posterior facet and the subtalar vertical angle (SVA) were measured in 3 different coronal planes of the ST joint.

RESULTS

The posterior facet was concave in 88% and flat in 12%. The posterior facet was oriented in valgus in 90% and varus in 10% when measured in the middle coronal plane. However, the SVA changed depending on which coronal plane it was measured in.

CONCLUSION

We believe it is important to get a better insight into the morphological parameters of the ST joint.

CLINICAL RELEVANCE

Knowledge of subtalar joint morphology could help clarify why certain failures have occurred in reconstructive hindfoot surgery and thus might help plan the surgical procedure to reduce these failures in the future.

Articular and angular dimensions of the talus: inter-relationship and biomechanical significance

SUMMARY OF BACKGROUND DATA

Research on biomechanics of the ankle and foot has demonstrated a complex pattern of load distribution through the ankle joint.

OBJECTIVE

Investigating possible relationship between articular dimensions, angular parameters and overall talar morphology.

METHODS

Two linear dimensions, six articular surfaces and three angular parameters were measured from dried human talar bones (left=60; right=82). Angular parameters were measured at the neck of the bone (junction of the head and the body). Correlation and co-variation were worked out between the values of surface area parameters and the angular orientations measured from all the samples in context of load transmission across the talus.

RESULTS

The total trochlear surface area of the talus totaled approximately equal to the sum of areas at the head and the lower surface of the talus. The vertical angle showed a strong correlation with the articulating surface area below the head of the talus in contact with the spring ligament.

CONCLUSIONS

Articular surface areas as well as the angular orientations of talar components vary with the magnitude of stress subjected to the bone. The inter-relationship between articular and angular parameters within the talus demonstrates strong correlation for certain parameters.

The varus ankle and instability

Varus ankle associated with instability can be simple or complex. Multiple underlying diseases may contribute to this complex pathologic entity. These conditions should be recognized when attempting proper decision-making. Treatment options range from conservative measures to surgical reconstruction. Whereas conservative treatment might be a possible approach for patients with simple varus ankle instability, more complex instabilities require extensive surgical reconstructions. However, adequate diagnostic workup and accurate analysis of varus ankle instability provide a base for the successful treatment outcome.

Morphology of sustentaculum tali: Biomechanical importance and correlation with angular dimensions of the talus

SUMMARY OF BACKGROUND DATA

The talus and the calcaneus share the bulk of load transmitted from the leg to the skeleton of the foot. The present study analyses the inter-relationship between the superior articular surface and the angular dimensions of the talus with the morphology of the sustentaculum tali.

OBJECTIVE

Identification of possible relationships between different angular parameters of the talus morphology and the sustentaculum tali in context of load transmission through the foot.

METHODS

One articular surface and three angular parameters at the junction of the head and the body were measured from dried human talar bones. Corresponding calcaneal samples were measured for four dimensions at the sustentaculum tali. Correlation and regression statistical values between parameters were worked out and analysed.

RESULTS

Several parameters within the talus demonstrated significant correlations amongst themselves. The neck vertical angle showed a strong correlation with the articulating surface area below the head of the talus.

CONCLUSIONS

The inter-relationship between articular and angular parameters within the talus demonstrates strong correlation for certain parameters. Data presented in the study may be helpful to adjust calcaneal and talar screw placement techniques, prosthesis designing and bio-mechanical studies at this important region.

Chronic ankle instability: biomechanics and pathomechanics of ligaments injury and associated lesions

The objective of this study was to evaluate the conditions of ankle stability and the morphological and/or lesional factors in sprains that determine when instability becomes chronic. It is based on a review of the literature and the data from the 2008 Sofcot symposium. The biomechanics of the ankle cannot be reduced to a simple flexion-extension movement with one degree of freedom as characterized by the talocrural joint: its function cannot be dissociated from the subtalar joint, allowing the foot to adapt to the ground surface. Functional stability is related to the combination of the particular biometry of the joint surfaces and a multiaxial ligament system. The bone morphology of the talus, shaped like a truncated cone, explains the potential instability in plantar flexion; the radii of curvature of the talar dome have a variable mediolateral distribution: most often the medial radius of curvature is inferior to the lateral radius of curvature (66%), sometimes equal (19%), or inverted (15%). Joint kinematics, combining rotation and slide, can therefore be modulated by the talar morphology, explaining the occurrence of at-risk ankles. Ligament stability relies on the organization in three parts of the lateral collateral ligament and the specific subtalar ligaments: the cervical and the talocalcaneal interosseous ligament. The different injury mechanisms are largely responsible for the sequence of ligament lesions: the most frequent is inversion. The first ligament stabilizers correspond to the cervical and anterior talofibular ligaments; the talocalcaneal ligament, by its oblique orientation, is solicited when there is a dorsal varus-flexion component. In chronic instability, these mechanisms explain the onset of associated lesions (impingement, osteochondral lesions, fibular tendon pathology), which can play a role in instability syndrome. Ligament lesions determine laxity, characteristic of mechanical instability. Functional instability goes along with proprioceptive deficiency. There are postural factors such as varus of the hindfoot that favor instability. Knowledge of all these factors, often associated, will provide a precise lesional assessment and treatment adapted to the instability.

Clinical study of chronic lateral ankle instability: injured ligaments compared with stress X-ray examination

BACKGROUND

A comparative analysis of ankle stress X-ray findings and the condition of injured ligaments in patients with chronic lateral ankle instability was performed to determine a method of identifying the condition of injured ligaments prior to operation.

METHODS

Altogether, 36 males and 80 females were included in the study. The average age at the time of operation was 29.4 years. Anterior drawer distances and talar tilt angles were measured manually. During the operations, the injured ligaments were classified into 25 categories.

RESULTS AND CONCLUSION

The condition of the injured ligaments in patients with a talar tilt angle of more than 15 degrees had injured ligaments that were almost avulsed and degenerated or completely absent.

In vivo kinematics of the tibiotalar joint after lateral ankle instability

BACKGROUND

Previous studies have suggested that injury to the anterior talofibular ligament (ATFL) may be linked to altered kinematics and the development of osteoarthritis of the ankle joint. However, the effects of ATFL injury on the in vivo kinematics of the ankle joint are unclear.

HYPOTHESIS

Based on the orientation of the ATFL fibers, ATFL deficiency leads to increased anterior translation and increased internal rotation of the talus relative to the tibia.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The ankles of 9 patients with unilateral ATFL injuries were compared as they stepped onto a level surface. Kinematic measurements were made as a function of increasing load. With use of magnetic resonance imaging and orthogonal fluoroscopy, the in vivo kinematics of the tibiotalar joint were measured in the ATFL-deficient and intact ankles of the same individuals.

RESULTS

A statistically significant increase in internal rotation, anterior translation, and superior translation of the talus was measured in ATFL-deficient ankles, as compared with the intact contralateral controls. For example, at 100% body weight, ATFL-deficient ankles demonstrated an increase of 0.9 +/- 0.5 mm in anterior translation (P = .008), an increase of 5.7 degrees +/- 3.6 degrees in internal rotation (P = .008), and a slight increase of 0.2 +/- 0.2 mm in the superior translation (P = .02) relative to the intact contralateral ankles.

CONCLUSION

Deficiency of the ATFL increases anterior translation, internal rotation, and superior translation of the talus.

CLINICAL RELEVANCE

Altered kinematics may contribute to the degenerative changes observed with chronic lateral ankle instability. These findings might help to explain the degenerative changes frequently observed on the medial talus in patients with chronic ATFL insufficiency and so provide a baseline for improving ankle ligament reconstructions aimed at restoring normal joint motion.

Correlation of dynamic cartilage contact stress aberrations with severity of instability in ankle incongruity

Joint instability is presumed to cause abnormality in cartilage contact mechanics, which accumulatively damages the articular surface, leading to osteoarthritis. The purpose of this study was to clarify the effect of instability on dynamic cartilage contact mechanics. Using human ankle cadaver specimens, potentially unstable ankles were modeled by introducing a coronally directed step-off incongruity of the anterior tibial surface and/or by transecting the anterior talofibular ligament. Specimens were subjected to a duty cycle with quasi-physiologic stance-phase motion and loading. AP tibial forces were modulated, causing a controlled, quantifiable ankle subluxation during the duty cycle. Instantaneous changes in local articular contact stresses were continuously measured using a thin, flexible pressure transducer. Tests were repeated while varying the tibial surface condition (anatomic, 1-mm step-off, and 2-mm step-off), both before and after transection of the anterior talofibular ligament, with various AP force magnitudes, so that situations of various degrees of instability were created for each specimen. Instability events occurred when the step-off incongruity was introduced, with the abnormality in joint kinematics being greater after ligament transection. Contact stress data revealed that these instability events involved distinctly abrupt increases/decreases in local articular contact stresses, and that the degree of abruptness was correlated nearly linearly with the abnormality in kinematics. The severity of contact stress aberration appeared to be correlated with the degree of instability. Given this linear relationship, even small instability events presumably involve appreciable abnormality in dynamic joint contact mechanics.

The biomechanical influence of tibio-talar containment on stability of the ankle joint

Chronic ankle instability (CAI) is a frequent sport orthopaedic entity. Although many risk factors have been studied extensively, little is known how it is influenced by the osseous joint configuration. Based on lateral X-rays, the radius of the talar surface and the tibial coverage of the talus (sector alpha) were measured on a DICOM/PACS system in 52 patients with CAI and an age- and sex-matched control group. The talar radius was found to be larger in patients with CAI (21.2 +/- 2.4 mm) than in the control group (17.7 +/- 1.9 mm; P < 0.0001). The tibio-talar sector was smaller in patients with CAI (80 degrees +/- 5.1 degrees ) than in the control group (88.4 degrees +/- 7.2 degrees ; P < 0.0001). The aim of this study is to analyse the biomechanical influence of the clinical data on stability of the ankle joint. A two-dimensional model of the tibio-talar joint in the sagittal plane was developed. The joint configuration was described by the tibio-talar sector (alpha) and the radius (r) of the talus. The force (F = F (BW) tan alpha/2) and energy (E = F (BW) r [1 - cos alpha/2]) to dislocate the talus out of the tibial plafond were deduced. Ankle stability is a function of the tibio-talar sector: the force necessary to dislocate the joint is decreasing with a smaller sector. The clinical data show that the force needed to dislocate the ankle of CAI patients was 14% weaker than the one needed in the case of healthy subjects (P < 0.0001). The energy to dislocate the ankle depends both on the sector and the radius. The clinical data do not show a significant difference between the energy needed to dislocate the joint of CAI patients and the one of healthy subjects. This is because there is a correlation of a small sector and a large radius for CAI ankles. CAI is associated with an unstable osseous joint configuration, which is characterized by a larger radius of the talus and a smaller tibio-talar sector. The findings of the biomechanical model explain the clinical observations and demonstrate how stability of the ankle joint is influenced by the osseous configuration. Surgical ankle ligament stabilization might be more recommended in patients with an unstable osseous configuration as such patients have a disposition for recurrent sprains. Removing anterior osteophytes for anterior impingement should be done carefully in CAI patients because this would decrease the tibial coverage of the talus and thus dispose the talus to dislocate anteriorly. People who have an unstable ankle configuration and who nevertheless engage in activities with high risk of ankle sprains could be asked to wear ankle protecting sports equipment.

Chronische Instabilität des oberen Sprunggelenks

Chronic ankle instability represents a typical sports injury. After an acute ankle sprain 20-40% of the injured develop chronic ankle instability. From an orthopaedic point of view chronic ankle instability can be subdivided into lateral and medial instability or a combination of both, the so-called rotational ankle instability. From a pathophysiological point of view, chronic ankle instability can be either mechanical with a structural ligament lesion or functional with loss of neuromuscular control. For the physician chronic ankle instability is a difficult entity as the diagnosis is usually complex and the therapy often surgical. This review on chronic ankle instability deals with the pathomechanisms, diagnostics, indications for conservative and surgical treatments, and possible long-term sequelae, such as ligamentous osteoarthritis.