Update on Subtalar Joint Instability

Importance of observer experience in clinical assessment of ankle and subtalar joint laxity: Validation of a multidirectional 3D opto-electronic motion analysis protocol

BACKGROUND

Role of ankle and subtalar ligaments remains poorly understood due to inconsistent literature. This study validates a protocol for analyzing multidirectional foot and ankle motions and assesses the impact of experience on clinical evaluations of ankle and subtalar instability.

METHODS

Five cadaveric feet were tested using a 3D opto-electronic system to measure talus, tibia, and calcaneus motions under varying ligament conditions. Anterior Drawer Test (ADT), varus talar tilt test in neutral flexion (VTTT), and in dorsiflexion (VTTTF) were tested by one experienced and one inexperienced observer. The system measured multidirectional angular rotations.

RESULTS

Intra-observer ICC exceeded 0.97. For ADT, flexion/extension and internal/external rotation correlated significantly with laxity scores for both observers (p < 0.05). For VTTT, varus/valgus correlations were stronger for the experienced observer, VTTTF correlations were significant only for the experienced observer.

CONCLUSION

3D opto-electronic is reliable for foot and ankle multidirectional motion analysis. Experience improves subtalar instability assessment accuracy.

LEVEL OF EVIDENCE

Level 5 (cadaveric study).

Impact of subtalar joint mobilization on walking ability in patients with intra-articular varus of the hindfoot joint with chronic ankle instability

BACKGROUND

Patients with chronic ankle instability (CAI) often experience recurrent swelling and pain, which hinder their ability to walk long distances. Emerging evidence suggests that joint mobilization can enhance ankle function in patients with CAI.

OBJECTIVE

The aim of this study is to investigate the effects of subtalar joint mobilization on enhancing ankle stability, alleviating ankle pain, and improving the walking ability of patients diagnosed with CAI.

METHODS

A retrospective analysis was conducted on 46 patients who were treated between April 2022 and October 2023. They were randomly divided into two groups: a treatment group with 23 cases receiving conventional treatment along with subtalar joint mobilization treatment, and a control group with 23 cases receiving only conventional treatment. The treatment duration was eight weeks. Pain levels and walking ability were assessed before and after the treatment period.

RESULTS

After eight weeks of treatment, the treatment group showed significant increases in the number of heel raises on the affected leg (NLHSL), improvements in the star excursion balance test (SEBT), and higher American Orthopedic Foot and Ankle Society (AOFAS) scores compared to the control group. Additionally, resting pain (RVAS) and walking pain (WVAS) scores were significantly lower in the treatment group. However, there was no statistically significant difference in single-leg standing time (SLT) between the two groups. Within the control group, post-treatment assessments indicated significant improvements in dynamic balance and control measures (SLT, NLHSL, SEBT), but no significant changes were observed in pain levels (RVAS, WVAS) or rear foot function (AOFAS). In contrast, the treatment group showed significant improvements across all measured parameters (RVAS, WVAS, SLT, NLHSL, SEBT, and AOFAS) following treatment.

CONCLUSION

Subtalar joint mobilization effectively reduces ankle pain and enhances walking ability among patients with CAI by improving ankle stability. The observed improvements in walking ability may stem from mitigating compensatory mechanisms associated with varus of the calcaneus and ankle instability.

Reconstruction of the interosseous talocalcaneal ligament using allograft for subtalar joint stabilization is effective

PURPOSE

The aim of this study was to assess the biomechanical effects of subtalar ligament injury and reconstruction on stability of the subtalar joint in all three spatial planes.

METHODS

Fifteen fresh frozen cadaveric legs were used, with transfixed tibiotalar joints to isolate motion to the subtalar joint. An arthrometer fixed to the lateral aspect of the calcaneus measured angular displacement in all three spatial planes on the inversion and eversion stress tests. Stress manoeuvres were tested with the intact joint, and then repeated after sequentially sectioning the inferior extensor retinaculum (IER), cervical ligament (CL), interosseous talocalcaneal ligament (ITCL), arthroscopic graft reconstruction of the ITCL, and sectioning of the calcaneo-fibular ligament (CFL).

RESULTS

Sectioning the ITCL significantly increased angular displacement upon inversion and eversion in the coronal and sagittal planes. Reconstruction of the ITCL significantly improved angular stability against eversion in the axial and sagittal planes, and against inversion in the axial and coronal planes, at the zero time point after reconstruction. After sectioning the CFL, resistance to eversion decreased significantly in all three planes.

CONCLUSION

Progressive injury of ligamentous stabilisers, particularly the ITCL, led to increasing angular displacement of the subtalar joint measured with the inversion and eversion stress tests, used in clinical practice. Reconstruction of the ITCL using tendon graft significantly stabilised the subtalar joint in the axial and sagittal planes against eversion and in the axial and coronal planes against inversion, immediately after surgery.

Increased subtalar rotational motion in patients with symptomatic ankle instability under load and stress conditions

PURPOSE

Differentiating subtalar and ankle instability in the clinical setting is challenging. This study aims to analyze the rotational laxity of the subtalar joint bilaterally in patients with asymptomatic and symptomatic ankle instability under simulated load and stress-induced position of the subtalar joint.

METHODS

A case-control study was conducted using an adjustable load device (ALD). Patients with chronic ankle instability and healthy volunteers were included. Each subject underwent a CT scan under mechanical stress and simulated weight-bearing conditions, maintaining maximum eversion and inversion hindfoot positions. The images were obtained in a single model, allowing calculations of the motion vector as well as the helical axis. The helical axis was defined by a rotation angle and a translation distance.

RESULTS

A total of 72 feet were included in the study. Thirty-one patients with unilateral symptoms and five healthy controls were selected, defining two groups: symptomatic (n = 31) and asymptomatic (n = 41). An absolute difference of 4.6º (95%CI 2-11.1) rotation angle was found on the helical axis of the symptomatic vs. asymptomatic group (p = 0.001). No significant differences were detected in the translation distance (n.s.) between the groups. Additionally, a significant positive correlation was found between the rotation angle and translation distance through the helical axis in the asymptomatic group (r = 0.397, p = 0.027).

CONCLUSION

Patients with chronic ankle instability suspected of having subtalar joint instability showed a wider subtalar range of laxity in terms of rotation about the helical axis. Furthermore, differences in kinematics between symptomatic and asymptomatic hindfeet was demonstrated when both feet were compared.

LEVEL OF EVIDENCE

III.

Hindfoot motion through helical axis image-based on dynamic CT scan using an original simulated weightbearing device

BACKGROUND

Determining the treatment of subtalar joint (STJ) instability requires a better understanding of the biomechanical principles underlying the condition and, a proper diagnosis. This study aimed to analyze "in vivo" the range of motion of the subtalar joint (STJ) measured on two (2D) and three dimensions (3D) image-based on CT Scan using an original device that maintains a simulated weightbearing. The secondary goal was to correlate the 2D and 3D measurement.

METHODS

An observational study was conducted, using an original Dynamic Simulated Weightbearing Device. Asymptomatic ankles were included. Each subject underwent a CT scan under mechanical stress and simulated weightbearing conditions, maintaining maximum eversion and inversion hindfoot positions. The images were obtained, combining both inversion and eversion positions in a single model, which allows for to calculation of the motion vector as well as the helical axis. The helical axis (rotation angle and translation distance), subtalar tilt, anterior drawer, and, subtalar and calcaneocuboid uncoverage were the determinations.

RESULTS

Forty asymptomatic ankles were included. The average range of motion of the STJ amounts to 31.5° ± 9.1° of rotation and 1.56 ± 0.8 mm of translation distance. The anterior drawer and subtalar uncoverage variables were statistically significantly related to each other (r = 0.57; P = 0.00001). However, these 2-D measured variables were not related to kinematic measures of rotation through the helical axis (3D) (p = 0.14; p = 0.19) CONCLUSIONS: The average range of motion of the STJ amounts to 31.5° ± 9.1° of rotation and 1.56 ± 0.8 mm of translation distance. We found no significant correlation between 2D and 3D measurements. In our opinion, the rotation angle and translation distance should be considered the most accurate measurements and should be calculated on every STJ instability for comparison with the asymptomatic population LEVEL OF EVIDENCE: Observational study.

LEVEL OF EVIDENCE III

Decreased Peritalar Subluxation in Progressive Collapsing Foot Deformity with Ankle Valgus Tilting

Background

Middle facet subluxation (MFS) has been established as an early indicator of peritalar subluxation. However, when progressive collapsing foot deformity (PCFD) affects the ankle leading to a valgus talar tilt (Class E), structures and anatomic relationships distal to the ankle joint may be affected. Therefore, this study aimed to assess radiographic parameters of peritalar subluxation in patients with PCFD who either did or did not have a valgus ankle. Our hypothesis was that these parameters would differ in Class E patients, upsetting their capability to quantify deformity.

Methods

We performed a prospective comparative study utilizing weight-bearing computed tomography (WBCT) images of 21 feet with PCFD and with valgus of the ankle and 64 with flexible PCFD without ankle involvement. Parameters including MFS, the medial cuneiform-to-floor distance, the forefoot arch angle, the talonavicular coverage angle, the hindfoot moment arm (HMA), the foot-ankle offset (FAO), and the talar tilt angle (TTA) were measured and compared. Variables that influence the presence of ankle valgus and overall alignment were assessed by multivariable regression models.

Results

Patients with PCFD and ankle valgus demonstrated a higher mean HMA (20.79 mm [95% confidence interval (CI), 17.56 to 24.02 mm] versus 8.94 mm [95% CI, 7.09 to 10.79 mm]), FAO (14.89% [95% CI, 12.51% to 17.26%] versus 6.32% [95% CI, 4.96% to 7.68%]) and TTA (95% CI, 17.10° [14.75° to 19.46°] versus 2.30° [95% CI, 0.94° to 3.65°]) and lower mean MFS (21.84% [95% CI, 15.04% to 28.63%] versus 38.45% [95% CI, 34.55% to 42.34%]) compared with the group without ankle valgus (p < 0.0001 for all). The FAO was influenced by MFS in the group without ankle valgus (p <0.0001) but not in the group with ankle valgus (p = 0.9161). FAO values of ≥12.14% were a strong predictor (79.2%) of ankle valgus deformity.

Conclusions

Subluxation of the middle facet was not as severe and did not influence the overall alignment in patients with PCFD who had valgus of the ankle (Class E). These findings suggest a distal peritalar reduction in the presence of a proximal deformity, making MFS an imprecise disease parameter in this scenario. An FAO value of ≥12.14% was a strong indicator of ankle deformity in patients with PCFD.

Level of Evidence

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

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.

Subtalar instability

Subtalar instability is a confusing yet important condition in patients with lateral ankle instability. The author will explore subtalar kinematics, and how they are closely related to the joint stability of the subtalar joint, both with respect to its intrinsic ligaments and its extrinsic ligaments. As subtalar instability is difficult to diagnose, this article will provide readers with a better understanding of its clinical presentation. Discussions will also include useful radiographic modalities and the most recent evidence regarding their accuracy. The last section discusses surgical options and what the readers need to know in order to make a decision.

Allogeneic tendons in the treatment of malunited lateral malleolar avulsion fractures with chronic lateral ankle instability

BACKGROUND

The aim of this study is to report our institution's experience regarding the application of allogeneic tendons for the reconstruction of malunited lateral malleolar avulsion fractures with chronic lateral ankle instability.

METHODS

This retrospective study included 34 (34 ankles) patients surgically treated for malunited lateral malleolar avulsion fractures with chronic lateral ankle instability from January 2016 to December 2019. All patients underwent allogeneic tendon reconstruction. The pre- and postoperative American Orthopaedic Foot and Ankle Society (AOFAS) scores、Karlsson Ankle Functional Scores (KAFS) and visual analogue scale (VAS) scores were used to evaluate the functional recovery of the ankle joint. The final follow-up, based on radiographic assessment, including talar tilt and anterior talar translation, was performed to evaluate the stability of the postoperative ankle joints.

RESULTS

Thirty-two patients (32 ankles) returned for final clinical and radiologic follow-up at an average of 29 (range 24-35) months and 2 patients (2 ankles) were lost to follow-up. The preoperative talus inclination angle (13.6 ± 1.9°) and anterior displacement (9.6 ± 2.8 mm) were re-examined under X-ray and found to be reduced to 3.4 ± 1.2° and 3.8 ± 1.1 mm, respectively (p＜0.01). The AOFAS scores increased from 58.5 ± 4.0 to 90.9 ± 3.8 and the Karlsson scores improved from 52.2 ± 3.6 to 89.8 ± 4.5, which was obviously better and the difference was statistically significant (P < 0.01). The VAS scores were significantly reduced from a preoperative mean of 6.8 ± 1.0 to 2.8 ± 0.9 postoperatively (p＜0.01).

CONCLUSION

In this population and with this follow-up, the application of allogeneic tendons to treat malunited lateral malleolar avulsion fractures combined with chronic lateral ankle instability appeared safe and effective.

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.

Particularities on Anatomy and Normal Postsurgical Appearances of the Ankle and Foot

The anatomy of the ankle and foot is complex, allowing for a wide range of functionality. The movements of the joints represent a complex dynamic interaction. A solid understanding of the characteristics and actions of the anatomic elements helps explain the mechanisms and patterns of injury. This article reviews the anatomy, with special focus on concepts that are the object of recent study and the features that favor the development of symptoms. Good understanding of the surgical procedures helps in providing information to guarantee a favorable outcome. We review the commonly expected postsurgical appearances and the most common postsurgical complications.

Acute Ankle Sprains

Understanding the types of ankle sprains is essential in determining the most appropriate treatment and preventing substantial missed time from sports. Commonly known and recognized is an acute lateral ankle sprain, however, a differentiation should also be made to understand high (syndesmotic) ankle sprains as the mechanism of injury and recovery periods differ between these two types.

Reconstruction of the cervical ligament in patients with chronic subtalar instability

PURPOSE

Diagnosis and treatment of subtalar instability (STI) remains complicated and challenging. The purpose of this study was to investigate the outcome of an anatomical reconstruction of the cervical ligament in patients with suspected chronic STI.

METHODS

This prospective study assessed the results of a surgical reconstruction of the cervical ligament using a gracilis tendon graft in a group of 14 patients (16 feet). Diagnosis of STI was performed using a predefined algorithm including clinical signs, MRI and peroperative evaluation. All patients had symptoms of chronic hindfoot instability despite prolonged non-surgical treatment. At final follow-up the outcome was assessed using the Karlsson score, the Foot and Ankle Outcome Score and the American Orthopaedic Foot and Ankle Society score.

RESULTS

After an average follow up of 22.6 months (range, 15-36), all patients reported significant improvement compared to their preoperative symptoms. The mean preoperative Karlsson score improved from 36.4 ± 13.5 (median 37, range 10-55) to a mean postoperative Karlsson score was 89.6 ± 8.5 (median 90, range 72-100) (P < 0.0001). The cervical ligament reconstruction was combined with other procedures in 13 cases: calcaneofibular ligament (CFL) reconstruction (3), CFL and anterior talofibular ligament reconstruction (7), bifurcate ligament reconstruction (3).

CONCLUSION

Anatomical reconstruction of the cervical ligament is a valid technique to treat patients with STI. It is a safe procedure and produces good clinical results with minimal complications. This technique can be considered in more complex cases and can be combined with other procedures according to the specific location of the instability.

LEVEL OF EVIDENCE

Level III.

Summary Report of the Arthritis Foundation and the American Orthopaedic Foot & Ankle Society's Symposium on Targets for Osteoarthritis Research: Part 2: Treatment Options

This second of a 2-part series of articles recounts the key points presented in a collaborative symposium sponsored jointly by the Arthritis Foundation and the American Orthopaedic Foot & Ankle Society with the intent to survey current treatment options for osteoarthritis (OA) of the foot and ankle. A meeting was held virtually on December 10, 2021. A group of experts were invited to present brief synopses of the current state of knowledge and research in this area. Topics were chosen by meeting organizers, who then identified and invited the expert speakers. Part 2 overviews the current treatment options, including orthotics, non-joint destructive procedures, as well as arthroscopies and arthroplasties in ankles and feet. Opportunities for future research are also discussed, such as developments in surgical options for ankle and the first metatarsophalangeal joint. The OA scientific community, including funding agencies, academia, industry, and regulatory agencies, must recognize the importance to patients of addressing the foot and ankle with improved basic, translational, and clinical research.

LEVEL OF EVIDENCE

Level V, review article/expert opinion.

Exosomes derived from platelet-rich plasma administration in site mediate cartilage protection in subtalar osteoarthritis

Subtalar osteoarthritis (STOA) is often secondary to chronic ankle sprains, which seriously affects the quality of life of patients. Due to its etiology and pathogenesis was not studied equivocally yet, there is currently a lack of effective conservative treatments. Although they have been used for tissue repair, platelet-rich plasma-derived exosomes (PRP-Exo) have the disadvantage of low retention and short-lived therapeutic effects. This study aimed to determine whether incorporation of PRP-Exo in thermosensitive hydrogel (Gel) increased their retention in the joint and thereby playing a therapeutic role on STOA due to chronic mechanical instability established by transecting lateral ligaments (anterior talofibular ligament (ATFL)/calcaneal fibular ligament (CFL)). PRP-Exo incorporated Gel (Exo-Gel) system, composed of Poloxamer-407 and 188 mixture-based thermoresponsive hydrogel matrix in an optimal ratio, was determined by its release ability of Exo and rheology of Gel response to different temperature. The biological activity of Exo-Gel was evaluated in vitro, and the therapeutic effect of Exo-Gel on STOA was evaluated in vivo. Exo released from Exo-Gel continuously for 28 days could promote the proliferation and migration of mouse bone mesenchymal stem cells (mBMSCs) and chondrocytes, at the same time enhance the chondrogenic differentiation of mBMSCs, and inhibit inflammation-induced chondrocyte degeneration. In vivo experiments confirmed that Exo-Gel increased the local retention of Exo, inhibited the apoptosis and hypertrophy of chondrocytes, enhanced their proliferation, and potentially played the role in stem cell recruitment to delay the development of STOA. Thus, Delivery of PRP-Exo incorporated in thermosensitive Gel provides a novel approach of cell-free therapy and has therapeutic effect on STOA.

Graphical Abstract

Association between subtalar articular surface typing and flat foot deformity: which type is more likely to cause flat foot deformity

Background

Previous studies have shown a wide range of anatomical classifications of the subtalar joint (STJ) in the population and this is related to the different force line structures of the foot. Different subtalar articular surface morphology may affect the occurrence and development of flat foot deformity, and there are fewer studies in this area. The main objective of our study was to determine the association of different subtalar articular surface with the occurrence and severity of flat foot deformity.

Methods

We analyzed the imaging data of 289 cases of STJ. The articular surface area, Gissane’s angle and Bohler’s angle of subtalar articular surface of different types were counted. The occurrence and severity of flat foot deformity in different subtalar articular surface were judged by measuring the Meary angle of foot.

Results

We classified 289 cases of subtalar articular surface into five types according to the morphology. According to Meary angle, the flat foot deformity of Type I and Type IV are significantly severer than Type II (P < 0.05). Type II (7.65 ± 1.38 cm²) was significantly smaller than Type I (8.40 ± 1.79 cm²) in the total joint facet area(P < 0.05). Type III (9.15 ± 1.92 cm²) was smaller than Type I (8.40 ± 1.79 cm²), II (7.65 ± 1.38 cm²) and IV (7.81 ± 1.74 cm²) (P < 0.05). Type II (28.81 ± 7.44^∘) was significantly smaller than Type I (30.80 ± 4.61 degrees), and IV (32.25 ± 5.02 degrees) in the Bohler’s angle (P < 0.05). Type II (128.49 ± 6.74 degrees) was smaller than Type I (131.58 ± 7.32 degrees), and IV (131.94 ± 5.80 degrees) in the Gissane’s angle (P < 0.05).

Conclusions

After being compared and analyzed the measurement of morphological parameters, joint facet area and fusion of subtalar articular surface were closely related to the severity of flat foot deformity and Type I and IV were more likely to develop severer flat foot deformity.

Level of evidence

Level III, retrospective comparative study.

3D-CT stress test for the assessment of CFL insufficiency

BACKGROUND

Following ankle sprains, some patients complain of their ankles "giving way," characterized by functional instability with no positive findings in traditional stress tests. The calcaneofibular ligament (CFL) may contribute to the stabilization of the subtalar and talocrural joints, and some functional instability may be due to CFL insufficiency. We aimed to clarify and quantitatively assess CFL insufficiency with three-dimensional stress computer tomography (CT) using the Pronation-External Rotation Stress Test (PERST).

METHODS

Ten patients who tested positive under PERST and underwent an isolated CFL reconstruction were included. Using a custom-made loading jig, we used the Supination-Internal Rotation Stress Test (SIRST) and PERST to assess the function of anterior talofibular ligament (ATFL) and CFL, respectively. 3D-CT in neutral position was used as a baseline, and we quantified the distance between the origin and insertion of the CFL and ATFL at 2 years pre- and postoperatively.

RESULTS

Postoperative scores improved in all patients with no giving way symptoms. The preoperative length of the CFL increased by 14.0% from baseline under PERST, while the postoperative length only increased by 2.0% and was significantly restricted (P < .01). The pre- and postoperative length of ATFL was increased by 7.5% and 9.0% from baseline under SIRST, respectively, with no significant difference (P = .41). The clinical function improved with significantly less change in distance between the origin and insertion under PERST and showed no difference under SIRST.

CONCLUSION

The 3D-CT stress test may be useful for quantifying pre- and postoperative CFL function. CFL insufficiency is one of the main causes of subtalar joint instability; therefore, measuring the distance between the origin and insertion of the CFL could provide the means to quantify the instability of the subtalar joint.

Feasibility of MRI for the evaluation of interosseous ligament vertical segment via subtalar arthroscopy correlation: comparison of 2D and 3D MR images

Background

Interosseous ligament vertical segment (IOLV) and calcaneofibular ligament (CFL) have been reported to be important in stabilizing the subtalar joint. Unlike CFL, there is not much information regarding the comparison of MRI results with surgical evaluation of IOLV and the comparison between 2D and 3D MRI on IOLV evaluation. The feasibility of MRI in IOLV evaluation has yet to be reported. The purpose of this study was to evaluate the validity and reliability of MRI in IOLV tear detection via correlation with arthroscopic results. We also compared the diagnostic performance of 2D and 3D MR images.

Methods

In this retrospective study, 52 patients who underwent subtalar arthroscopy after ankle MRI were enrolled. Arthroscopic results confirmed IOLV tear in 25 cases and intact IOLV in 27 cases. Two radiologists independently evaluated the IOLV tears using only conventional 2D images, followed by isotropic 3D images, and comparison with arthroscopic results.

Results

Only the 2D sequences interpreted by two readers showed a sensitivity of 64.0–96.0%, a specificity of 29.6–44.4%, a positive predictive value of 51.6–56.4%, and a negative predictive value of 57.1–88.9%. Addition of isotropic 3D sequences changed the sensitivity to 60.0–80.0%, specificity to 63.0–77.8%, positive predictive value to 64.3–76.9%, and negative predictive value to 66.7–80.8%. The overall diagnostic performance of isotropic 3D sequences (AUC values: 0.679–0.816) was higher than that of 2D sequences (AUC values: 0.568–0.647). Inter-observer and intra-observer agreement between the two readers was moderate-to-good for both 2D and 3D sequences. The diagnostic accuracy in 19 patients with tarsal sinus fat obliteration tended to increase from 26.3–42.1% to 57.9–73.7% with isotropic 3D sequences compared with 2D sequences.

Conclusions

Isotropic 3D MRI was feasible for the assessment of IOLV tear prior to subtalar arthroscopy. Additional 3D sequences showed higher diagnostic accuracy compared with conventional 2D sequences in IOLV evaluation. Isotropic 3D sequences may be more valuable in detecting IOLV tear in case of tarsal sinus fat obliteration.

A mouse model of ankle-subtalar joint complex instability induced post-traumatic osteoarthritis

BACKGROUND

Ankle-subtalar joint complex instability is not uncommonly presented in the clinic, but symptoms and signs similar to other conditions can easily lead to its misdiagnosis. Due to the lack of appropriate animal models, research on ankle-subtalar joint complex instability is limited. The aims of the present study were to establish an animal model of ankle-subtalar joint complex instability in mice and to explore its relationship with post-traumatic osteoarthritis (PTOA).

METHODS

Twenty-one male C57BL/6J mice were randomly divided into three groups: SHAM group (sham surgery group), transected cervical ligament + anterior talofibular ligament (CL+ATFL) group, and transected cervical ligament + deltoid ligament (CL+DL) group. Two weeks after surgery, all mice underwent cage running training. Balance beam and gait tests were used to evaluate the changes in self-movement in the mice after ankle-subtalar ligament injury. Micro-CT and histological staining were used to evaluate the progress of PTOA.

RESULTS

Compared with the SHAM group, balance and gait were affected in the ligament transection group. Twelve weeks after surgery, the time required to cross the balance beam in the CL+ATFL group was 35.1% longer and the mice slipped 3.6-fold more often than before surgery, and the mean step length on the right side was 7.2% smaller than that in the SHAM group. The time required to cross the balance beam in the CL+DL group was 32.1% longer and the mice slipped 3-fold more often than prior to surgery, and the average step length on the right side was 5.6% smaller than that in the SHAM group. CT images indicated that 28.6% of the mice in the CL+DL group displayed dislocation of the talus. Tissue staining suggested that articular cartilage degeneration occurred in mice with ligament transection 12 weeks after surgery.

CONCLUSIONS

Transected mice in the CL+ATFL and CL+DL groups displayed mechanical instability of the ankle-subtalar joint complex, and some mice in the CL+DL group also suffered from talus dislocation due to ligament injury leading to loss of stability of the bone structure. In addition, as time progressed, the articular cartilage displayed degenerative changes, which affected the ability of animals to move normally.

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.

Imaging of Peritalar Instability

Undiagnosed medial ankle instability can be a prerequisite for pathogenic progression in the foot, particularly for adult acquired flatfoot deformity. With the complex anatomy in this region, and the limitations of each individual investigational method, accurately identifying peritalar instability remains a serious challenge to clinicians. Performing a thorough clinical examination aided by evaluation with advanced imaging can improve the threshold of detection for this condition and allow early proper treatment to prevent further manifestations of the instability.

Imaging Techniques for Assessment of Dynamically Unstable Sports Related Foot and Ankle Injuries

Foot and ankle instability can be seen both in acute and chronic settings, and isolating the diagnosis can be difficult. Imaging can contribute to the clinical presentation not only by identifying abnormal morphology of various supporting soft tissue structures but also by providing referring clinicians with a sense of how functionally incompetent those structures are by utilizing weight-bearing images and with comparison to the contralateral side. Loading the affected joint and visualizing changes in alignment provide clinicians with information regarding the severity of the abnormality and, therefore, how it should be managed.

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.

Classification of the subtalar articular surface and its matching situation: an anatomical study on Chinese subtalar joint

PURPOSE

The subtalar joint (STJ) is complex in anatomy and function. The purpose of this study is to classify the articular surface of the calcaneus in a sample Chinese population and discuss the relationship between its matching situation and the stability of STJ.

METHODS

328 patients with 445 STJs were measured and classified using CT three-dimensional reconstruction. The calcaneal facets were classified according to the morphological characteristics. According to the number, shape, and fusion of the calcaneus and talus facets, the matching situation was determined. The parameters of measurement: the Gissane's angle, the Böhler's angle, the long-axis sum and the short-axis sum, and the average total joint facet area.

RESULTS

The calcaneal surfaces in a sample Chinese population were classified into five types: Type I (219, 49.2%), Type II (102, 22.9%), Type III (68, 15.3%), Type IV (47, 10.6%) and Type V (9, 2%). The total matching rate of STJ is 98%. In terms of Gissane's angle, there was a significant difference between Type II and Type IV (P < 0.05). The long-axis sum of Type III (4.53 ± 0.58 cm) was significantly smaller than other types (P < 0.05). Type II (3.64 ± 0.47 cm) was statistically larger than other types in the short-axis sum (P < 0.05). The average total joint facet area of Type III (7.05 ± 1.40 cm²) was significantly smaller than other types (P < 0.05). Type V (9.31 ± 3.96 cm²) was statistical differences with Type II, Type III and Type IV (P < 0.05). There was no statistically significant difference between left and right sides of the articular facets in this study (P > 0.05).

CONCLUSIONS

According to Bunnins's classification, the type with separated facets predominated but the matching situation between STJ was not elaborated, which was closely linked to the stability of STJ and surgical strategy of calcaneus fracture. The calcaneus articular surfaces in a sample Chinese population were divided into five types. Type I was the most common type and Type V was the rarest. Type II have the highest stability, Type V may be the lowest stability and Type III was more prone to osteoarthritis. The STJ articular surfaces were basically matched, contributing to the coordinate movement of the STJ. The matching articular surfaces of STJ were more stable than the mismatching surfaces. To some extent that STJ facet number, shape, facet area, and matching situation are factors in STJ stability, and the anatomical variations of the STJ offer predictive value in determining the predisposition to STI.

Does subtalar instability really exist? A systematic review

BACKGROUND

Subtalar joint instability (STI) is considered as a potential source of chronic lateral hindfoot instability. However, clinical diagnosis of STI is still challenging. This systematic review was conducted to assess the consistency of the clinical entity "subtalar instability", to investigate the reliability of available diagnostic tools and to provide a critical overview of related studies.

METHODS

A systematic review of the Medline, Web of Sciences and EMBASE databases was performed for studies reporting on tests to investigate subtalar instability or lesions of the subtalar ligaments. To investigate the relation with chronic STI, studies focusing on sinus tarsi syndrome (STS) or acute lesions of the subtalar ligaments were also included in the search strategy and were assessed separately.

RESULTS

This review identified 25 studies focusing on different topics: chronic STI (16), acute lesions of the subtalar ligaments (5) and STS (4). Twelve studies, assessing STI, demonstrated the existence of a subgroup with instability complaints related to abnormal increased subtalar motion (7) or abnormalities of the subtalar ligaments (6). We found insufficient evidence for measuring subtalar tilting using stress radiographs. MRI was able to assess abnormalities of the ligaments and stress-MRI detected abnormally increased motion.

CONCLUSION

Complaints of instability can be related to subtalar ligaments injuries and an abnormally increased motion of the subtalar joint. Stress radiographs should be interpreted with caution and should not have the status of a reference test. Clinical diagnosis should rely on several parameters including MRI.

Centre of Rotation of the Human Subtalar Joint Using Weight-Bearing Clinical Computed Tomography

Accurate in vivo quantification of subtalar joint kinematics can provide important information for the clinical evaluation of subtalar joint function; the analysis of outcome of surgical procedures of the hindfoot; and the design of a replacement subtalar joint prosthesis. The objective of the current study was to explore the potential of full weight-bearing clinical computed tomography (CT) to evaluate the helical axis and centre of rotation of the subtalar joint during inversion and eversion motion. A subject specific methodology was proposed for the definition of the subtalar joint motion combining three-dimensional (3D) weight-bearing imaging at different joint positions with digital volume correlation (DVC). The computed subtalar joint helical axis parameters showed consistency across all healthy subjects and in line with previous data under simulated loads. A sphere fitting approach was introduced for the computation of subtalar joint centre of rotation, which allows to demonstrate that this centre of rotation is located in the middle facet of the subtalar joint. Some translation along the helical axis was also observed, reflecting the elasticity of the soft-tissue restraints. This study showed a novel technique for non-invasive quantitative analysis of bone-to-bone motion under full weight-bearing of the hindfoot. Identifying different joint kinematics in patients with ligamentous laxity and instability, or in the presence of stiffness and arthritis, could help clinicians to define optimal patient-specific treatments.

Biomechanical Considerations in Rearfoot Fusions

This article discusses rearfoot fusions for foot and ankle surgeons. It establishes normal foot and ankle function primarily in the stance phase of gait. The foot is greatly affected by external and internal forces, which contribute to normal function or the need for compensatory mechanisms. As a result of compensation, many symptoms develop, often leading to debilitating disorders such as degenerative joint disease. The interaction of the ankle, subtalar, and midtarsal joints are outlined. Congenital deformities, trauma and abnormal compensation are reviewed along with corresponding sequelae. Surgery is often indicated to reduce symptoms, improve position, and help stabilize the foot.

Currently used imaging options cannot accurately predict subtalar joint instability

PURPOSE

To give a systematic overview of current diagnostic imaging options and surgical treatment for chronic subtalar joint instability.

METHODS

A systematic literature search across the following sources was performed: PubMed, ScienceDirect, and SpringerLink. Twenty-three imaging studies and 19 outcome studies were included. The Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS 2) tool was used to assess the methodologic quality of the imaging articles, while the modified Coleman Score was used to assess the methodologic quality of the outcome studies.

RESULTS

Conventional radiographs were most frequently used to assess chronic subtalar joint instability. Talar tilt, anterior talar translation, and subtalar tilt were the three most commonly used measurement methods. Surgery often included calcaneofibular ligament reconstruction.

CONCLUSION

Current imaging options do not reliably predict subtalar joint instability. Distinction between chronic lateral ankle instability and subtalar joint instability remains challenging. Recognition of subtalar joint instability as an identifiable and treatable cause of ankle pain requires vigilant clinical investigation.

LEVEL OF EVIDENCE

Systematic Review of Level III and Level IV Studies, Level IV.

[The periosteal flap augmentation technique in chronic lateral ankle instability]

OBJECTIVE

Anatomic repair of the lateral ligament complex of the ankle joint and augmentation with an autologous pedicled periosteal flap of the distal fibula following identification and concomitant treatment of intra-articular pathologies.

INDICATIONS

Symptomatic chronic mechanical lateral ankle instability. As a modular step in the treatment of osteochondral lesions in conjunction with lateral ankle instability.

CONTRAINDICATIONS

Higher degree osteoarthritis of the ankle joint (>Kellgren/Lawrence 2 and 4 or Outerbridge 3 and 4) and/or hindfoot deformity; mechanical incompetence of both the fibulotalar anterior ligament and the fibulocalcaneal ligament preventing anatomical reinsertion; general risk factors.

SURGICAL TECHNIQUE

Diagnostic arthroscopy for identification and treatment of intraarticular pathologies; verification and grading of ligamentous instability (medial, lateral, combined). Open exposure of the distal fibula and the ruptured components of the lateral ankle ligament complex. Anatomic reinsertion of the original ligaments and assessment of their mechanical competence. Apart from the situation in the juvenile patient with a thick periosteal layer a doubled and pedicled periosteal strip of the distal fibular periosteum will suffice for the augmentation in one ligamentous component, only. Fixation in the talus or calcaneus is achieved via suture anchors, screws with a washer or transosseous fixation via interference screw.

POSTOPERATIVE MANAGEMENT

Postoperative immobilization in a lower leg split cast or a splint until wound healing (5-8 days), mobilization in a walker or an ankle orthosis with consecutive full weight-bearing for further 4-5 weeks. Proprioceptive and pronator muscle training, optionally insole or lateral wedge at the shoe sole for 6 months postoperatively. Avoidance of contact sports for 4-6 months.

RESULTS

Several studies have reported reliable restoration of ligamentous ankle stability with overall success rates >90% and good to excellent total results in >90% of patients with limited minor complications. In view of the heterogeneous data from previous studies, some recent studies have demonstrated that the outcome after periosteal augmentation is comparable to that after techniques employing free tendon graft for anatomic restoration of ligamentous ankle stability. The technique has been applied successfully in cases of poor mechanical properties of the formerly ruptured ligaments and in patients with a high functional demand.