The C sign: more specific for flatfoot deformity than subtalar coalition

Review of the role of bone-SPECT/CT in tarsal coalitions

Tarsal coalition (TC) is a congenital abnormal connection (fibrous, cartilaginous, or osseous) between two or more bones in the hind and midfoot, mostly consisting of calcaneonavicular or talocalcaneal coalition, and is often asymptomatic. However, TCs may result in foot motion limitation and pain with or without flatfoot (pes planus), arising in adolescents and young adults. Appropriate imaging is needed to pinpoint foot pain in the (suspected) TC, starting with plain radiographs. Still, normal radiographs do not exclude TCs. Computed tomography (CT) and MRI are frequently used advanced imaging techniques. CT alone has known limited sensitivity in cartilaginous and fibrous TCs and correlation between CT abnormalities and pain may be challenging, as solely anatomical changes in TCs are often asymptomatic. MRI can depict soft tissue abnormalities in TC with high accuracy. Nonetheless, after the implantation of metallic osteosynthesis material, MRI is often limited due to image distortion, signal loss, and misregistration. Bone scintigraphy with [99mTc]Tc-diphosphonate single photon emission computed tomography/CT (bone-SPECT/CT) is a known sensitive tool to detect osteoblastic bone pathology. However, the literature concerning bone-SPECT/CT in TC patients is limited. This article reviews bone-SPECT/CT patterns in TCs, how it complements other imaging techniques and their relation to clinical complaints. Bone-SPECT/CT excels in accurate bone pathology characterization in TC, confidently excluding synchronous lesions elsewhere, and offering optimal insight into osseous structures and 3D-localization of bone metabolism for surgery planning. Furthermore, even with implanted osteosynthesis material, bone-SPECT/CT can pinpoint the culprit pain generator, where MRI is either contra-indicated or considerably hampered.

Tarsal Coalitions

Tarsal coalitions are recognized as a congenital anomaly whereby the two or more bones of the hindfoot and midfoot are fused resulting in limitation of foot motion and pain. Tarsal coalitions were found to be the cause of painful flatfeet in adolescents and young adults. Developing a clinical understanding of tarsal coalitions as well as developing a step-wise conservative and surgical approach for their treatment can alleviate patient symptomatology and provide excellent long-term benefits. Conservative treatment consists of immobilization, NSAIDs, and casting for symptomatic patients, and surgical treatment for symptomatic tarsal coalition consists of resection and/or arthrodesis.

Outcomes of Posterior Arthroscopic Subtalar Arthrodesis for Medial Facet Talocalcaneal Coalition

BACKGROUND

Medial facet talocalcaneal coalition can be a painful condition. This study aimed to determine clinical and radiographic outcomes of posterior arthroscopic subtalar arthrodesis (PASTA) for adult patients presenting with symptomatic medial facet talocalcaneal coalition and normal hindfoot alignment, with a minimal follow-up of 18 months.

METHODS

Between June 2017 and July 2019, this procedure was performed on 8 feet (8 patients; mean age, 55 [42-70] years; mean BMI, 29.8 [24.4-45.0] kg/m²). Clinical assessment was performed using Visual Analog Scale for Pain (VAS-P), Foot and Ankle Outcome Score (FAOS) and the 36-Item Short-Form Health Survey (SF-36). Patient satisfaction was assessed at the last available follow-up as "very satisfied", "satisfied" or "unsatisfied". Radiographic analysis was performed using plain radiography, computed tomography (CT) scan and magnetic resonance imaging (MRI). The primary outcome was to determine both clinical and radiographic outcomes.

RESULTS

The mean follow-up was 25.1 (18.2-34.2) months. The authors found statistically significant improvement on all clinical scores (VASP-P, FAOS and SF-36). They registered 6 "very satisfied" patients, 2 "satisfied" patients and no "unsatisfied" patient. Fusion of the subtalar joint was observed in all patients by 12 weeks and in 5 of them as soon as 8 weeks postoperatively (mean, 9.5 [8-12] weeks). There were no cases of delayed fusion or nonunion of the subtalar joint, superficial or deep infection, neurovascular damage, thromboembolic event, screw breakage, need for hardware removal or revision surgery.

CONCLUSION

This study found that PASTA is a safe and reliable technique for adult patients presenting with symptomatic medial facet talocalcaneal coalition and normal hindfoot alignment, demonstrating and maintaining clinical improvement at an average follow-up of 2 years.

LEVEL OF EVIDENCE

Level IV, case series.

The C-sign in normal feet: a prospective study and novel imaging algorithm for subtalar joint tarsal coalition

OBJECTIVE

The C-sign on lateral radiographs has been subject to considerable debate with respect to its reliable association to subtalar joint tarsal coalition. The purpose of this study was to determine to what degree subtalar joint pronation factors into (a) the appearance of both complete and incomplete type A C-signs and (b) the conspicuity of the middle facet in both flatfeet and rectus feet.

STUDY DESIGN

Forty-seven normal adult volunteers were enrolled into the study with a total of 92 feet, of which 42 were flexible flatfeet and 50 were rectus feet with normal subtalar joint range of motion. Lateral weight-bearing radiographs were taken of each foot in a position of (a) standing and (b) maximum subtalar joint pronation. Investigators evaluated images for the visibility of the middle facet, and the presence or absence of a continuous or interrupted type A C-sign.

PRINCIPAL RESULTS

No continuous C-signs were produced with extreme pronation in either the rectus/normal or flatfoot populations. Three incomplete type A C-signs were produced with pronation, two of which were in rectus feet. Two absent middle facet signs were also produced with pronation. Absent visualization of the facet had high positive and negative predictive values (1.00 and 0.99 respectively) for the presence of an incomplete C-Sign.

MAJOR CONCLUSIONS

The standard, routine lateral foot/ankle radiographic image protocol for suspected talocalcaneal coalition should be modified routinely positioning the foot maximally supinated, thereby minimizing the possibility of producing C-signs (complete or type A incomplete) and/or absent middle facet signs with pronation in either normal or flatfeet. A novel algorithmic approach can then be simply applied to determine when ancillary CT scanning is warranted for suspected posterior facet coalition.

Anteroposterior Radiograph of the Ankle with Cross-Sectional Imaging Correlation

The focus of this article is to illustrate various pathologic entities and variants, heralding disease about the ankle, based on scrutiny of AP radiographs of the ankle, with correlative findings on cross-sectional imaging. Many of these entities can only be detected on the AP ankle radiograph and, if not recognized, may lead to delayed diagnosis and persistent morbidity to the patient. However, a vigilant radiologist, equipped with the knowledge of the characteristic appearance and typical locations of the imaging findings, should be able to make the crucial initial diagnosis and surmise additional findings to be confirmed on cross-sectional imaging.

Coalitions of the Tarsal Bones

Tarsal coalitions are the result of impaired mesenchymal separation of the tarsal bones. The most common types include calcaneonavicular or talocalcaneal coalitions. Subtalar stiffness results in pathologic kinematics with increased risk of ankle sprains, planovalgus foot deformity, and progressive joint degeneration. Resection of the coalition yields good results. Tissue interposition may reduce the risk of reossification, and concomitant deformity should be addressed in the same surgical setting.

Subtalar coalitions in the adult

Tarsal coalitions, while relatively uncommon, are typically identified in adult patients during an evaluation for ankle instability, sinus tarsus pain, and/or pes planovalgus. The true incidence of tarsal coalition is unknown with estimates ranging from 1% to 12% of the overall population. The most common area of involvement of the subtalar joint is the middle facet, and heightened awareness should be present in adult patients with limited motion of the subtalar joint. Standard radiographic imaging, to include a Harris heel view, is recommended initially, although computerized tomography scan and MRI are often necessary to confirm the diagnosis.

Subtalar coalition in pediatrics

Subtalar tarsal coalition is an autosomal dominant developmental maldeformation that affects between 2% and 13% of the population. The most common locations are between the calcaneus and navicular and between the talus and calcaneus. If prolonged attempts at nonoperative management do not relieve the pain, surgery is indicated. The exact surgical technique(s) should be based on the location of the pain, the size and histology of the coalition, the health of the other joints and facets, the degree of foot deformity, and the excursion of the heel cord.

The use of a portable CT scanner for the intraoperative assessment of talocalcaneal coalition resections

BACKGROUND

Intraoperative assessment of talocalcaneal (TC) coalition resection can be challenging, with no reliable plain radiographic view available for evaluation. Therefore, in March of 2011, we began using a CereTom portable CT scanner to assess TC coalition resections intraoperatively. This study evaluates the use of intraoperative CT during surgical resection of TC coalitions.

METHODS

Patients who received CT scans before and after TC coalition resection, by a single surgeon, were included. Those treated without (control group, n=12 feet) and with (intraoperative CT group, n=14 feet) intraoperative CT scan were retrospectively compared. Two blinded pediatric orthopaedic surgeons assessed the quality of resection using a side-by-side comparison of preoperative and postoperative CT scans. Each resection was rated as "excellent," "fair," or "poor," and medical records were reviewed to evaluate clinical outcome.

RESULTS

Substantial agreement was found between blinded reviewers (κ=0.71, 81% absolute agreement). Quality of resection was improved in the intraoperative CT group, with 57% of patients receiving an excellent rating compared with 25% in the control group. Patients in the intraoperative CT group were 4.0 times more likely to have a complete resection as compared with patients in the control group; however, this was not statistically significant (odds ratio, P>0.05; 95% confidence interval, 0.74-21.5). Intraoperative CT altered surgical decision making in 3 feet (21%) in the intraoperative CT group, leading to further resection and a subsequent excellent postoperative rating in 2 of these patients. There was 1 reoperation in the control group for continued pain and residual coalition identified on postoperative CT scan. In the intraoperative CT group there have been no reoperations for recurrent or residual qcoalition.

CONCLUSIONS

This study illustrates that intraoperative CT can alter surgical decision making and may improve the ability to obtain a complete resection in TC coalition surgery. In these technically challenging cases, intraoperative scans give immediate imaging feedback to surgeons, allowing intervention if residual resection is identified. If intraoperative CT scan is available, it should be considered for surgical treatment of TC coalition resections.

LEVEL OF EVIDENCE

Level III retrospective case-control study.

Talocalcaneal coalition combined with flatfoot in children: diagnosis and treatment: a review

Talocalcaneal coalition often leads to a flatfoot deformity in children. Previous reports have uncovered many aspects of tarsal coalition and flatfoot respectively, including the etiology, clinical presentation, and diagnostic imaging, as well as treatment. However, the optimum surgical procedure for talocalcaneal coalition combined with flatfoot has not been definitively determined. The nonconformity of treatment options is due to our incomplete knowledge of biomechanics, diagnosis, and indication of treatment for talocalcaneal coalition with flatfoot. The objectives of this review are to provide an overview of the current knowledge about etiology, biomechanics, classification, diagnosis, and treatment options for talocalcaneal coalitions with flatfoot and highlight its therapies in children.

C sign: talocalcaneal coalition or flatfoot deformity?

BACKGROUND

C sign is used to alert the physician of the possible presence of talocalcaneal coalition (TCC), so that advanced imaging can be ordered. The purpose of this study was to know the prevalence of the C sign among patients with TCC and its relationship to the presence of a TCC or to hindfoot alignment.

METHODS

Retrospective reviews of the presence of C sign in radiographs of 88 feet with TCC (proved by computed tomography scan or surgical findings) and 260 flexible flatfeet were conducted. C sign was classified as complete and interrupted (types A, B, and C). The interobserver variability of the C sign was studied. Seven radiographic parameters were measured to analyze the relationship of these measurements with the presence or absence of the C sign.

RESULTS

C sign was present in 68 feet (77%) with TCC: 14.5% complete and 62.5% interrupted (26% type A, 19.5% type B, and 17% type C). C sign was present in 116 flatfeet (45%), all of them interrupted (0.4% type A, 5.5% type B, and 39% type C). The talo-first metatarsal angle, the talohorizontal angle, the calcaneal pitch, the calcaneo-fifth metatarsal angle, and the naviculocuboid overlap presented a more pathologic value when a C sign was present. The κ-value for the presence of a C sign was 0.663.

CONCLUSIONS

The so-called true C sign (complete or interrupted type A) indicates the presence of a TCC and it is not related to flatfoot deformity. However, it is only present in 41% of the cases. The interrupted C sign is much more likely to be related to flatfoot deformity than to the presence of a TCC, specifically when a type C is found.

LEVEL OF EVIDENCE

Diagnostic Study level I.

Tarsal Coalitions: Radiographic, CT, and MR Imaging Findings

BACKGROUND

Tarsal coalitions affect up to 13% of the population and can be a cause of chronic ankle and hindfoot pain. They can be subdivided as osseous, cartilaginous, or fibrous types, each with unique radiographic, CT, and MR imaging findings. In particular, MR imaging offers the unique ability to determine the exact type of tarsal coalition that is present as well as whether any associated soft tissue abnormalities are present.

QUESTIONS/PURPOSES

The purposes of this paper were to (1) review the anatomy of the hindfoot; (2) review the radiographic, CT, and MR imaging findings of tarsal coalitions; and (3) review the imaging appearance of the specific types of tarsal coalitions.

METHODS

Online searches were performed using Google Scholar with the search criteria of "tarsal coalition," "hindfoot anatomy," and "subtalar coalition," and limiting the searches to papers published in the last 10 years in major radiology journals.

RESULTS

The anatomy of the hindfoot is complex but essential to understand. There are various radiographic, CT, and MR imaging findings that can be consistently noted in cases of tarsal coalition. The specific types of tarsal coalition demonstrate characteristic imaging findings.

CONCLUSIONS

Knowledge of the normal anatomy of the foot, in particular the hindfoot, combined with the knowledge of the imaging characteristics of different histologic subtypes of coalitions (osseous, cartilaginous, and fibrous) is essential for interpreting radiographic, CT, and MR images of the ankle and foot.

Ultrasound of talocalcaneal coalition: retrospective study of 11 patients

OBJECTIVE

To present the ultrasound appearance of talocalcaneal coalitions (TCC).

MATERIALS AND METHODS

We present a retrospective review of 11 patients (8 women and 3 men, age range 17-58 years, mean age 35.3 years) in which ultrasound, the first imaging study carried out, detected a TCC that was not known or suspected clinically. Patients were subsequently examined by standard radiographs, computed tomography (CT) or magnetic resonance imaging (MRI).

RESULTS

In 9 patients with fibrous coalition ultrasound showed a reduced joint space of the medial aspect of the anterior talocalcaneal joint associated with an irregular, pointed appearance of its outline. In 2 patients with osseous coalitions ultrasound revealed a smooth continuity of the hyperechoic bone surface between the medial talus and the substentaculum tali. The diagnosis was confirmed in 4 patients with CT and in 3 with MRI. In the remaining 4 patients standard radiographs were consistent with TCC.

CONCLUSION

Owing to its tomographic capabilities ultrasound can detect TCC. We suggest that study of the anterior subtalar joint should be a part of every ankle ultrasound examination as it can show a clinically unsuspected TCC. Confirmation of the coalition by CT or MRI is required in the preoperative assessment to better assess the type and extent of the congenital anomaly as well as the adjacent joints.

Bilateral tarsal coalition in a National Collegiate Athletic Association Division I basketball player: a case report

OBJECTIVE

To present a case of bilateral subtalar joint coalition in a National Collegiate Athletic Association Division I basketball player and the treatment plan that was used to manage the coalition from the beginning of conference play through the postseason.

BACKGROUND

A 20-year-old male basketball athlete (height = 182.8 cm, mass = 83.4 kg) presented with bilateral subtalar joint tarsal coalition that became symptomatic in 2006 and resulted in constant pain with any form of activity.

DIFFERENTIAL DIAGNOSIS

Traumatic injury of the talocalcaneal joint.

TREATMENT

Nonsurgical intervention of conservative therapy was elected.

UNIQUENESS

Less than 13% of the overall population is affected with tarsal coalition, so it is safe to assume that very few athletes competing at the collegiate or elite level suffer from this condition. This is the first report in the literature to document conservative manual therapies used to manage the symptoms of subtalar joint tarsal coalition in a Division I basketball player.

CONCLUSIONS

After the intensive treatment program for tarsal coalition was implemented, the patient experienced pain relief and was able to continue to compete at a competitive level. This case represents the need to further explore and document a conservative treatment protocol for tarsal coalition.

Tarsal coalitions in the adult population: does treatment differ from the adolescent?

There is a paucity of information on adult coalitions without large, well-designed outcome studies. Current recommendations are thus similar to those for adolescents. Based on the available literature, current recommendations include an initial trial of adequate nonoperative treatment in symptomatic coalitions. Unlike adolescent coalitions, nonoperative treatment may be even more effective in the adult patient as many are asymptomatic or discovered after injury. If nonoperative treatment fails, then surgical intervention is considered and tailored to the location of the coalition, existing advanced arthrosis, and any existing deformity. Similar to the adolescent, surgical treatment for adult calcaneonavicular coalitions typically involves an attempt at resection with some type of interposition. Resection can be attempted for talocalcaneal coalitions that do not present with advanced arthrosis or significant hindfoot malalignment. For those patients with advanced arthrosis, more than 50% involvement of the joint hindfoot malalignment, subtalar or triple arthrodesis is recommended. The decision between resection and arthrodesis is controversial in the adolescent population. With few outcome studies in adults, it is even more difficult to make definitive treatment recommendations; however, the indications for resection are likely even more limited. It is likely that the adult subtalar coalition that becomes symptomatic and fails nonoperative treatment will require arthrodesis for full pain relief and improvement in objective outcome measures, such as the AOFAS hindfoot score. Our treatment algorithm focuses first on a trial of nonoperative treatment of at least 3 months regardless of coalition location. After failed nonoperative treatment, calcaneonavicular coalitions are in most cases treated with excision and interpositional fat graft. For talocalcaneal coalitions, resection is offered to patients with neutral hindfoot alignment, some preservation of subtalar joint motion and no adjacent joint arthrosis. The patients are advised that the outcome after resection of talocalcaneal coalitions is less predictable than resection of calcaneonavicular coalitions. Those patients with absent subtalar motion and relatively normal hindfoot alignment are candidates for in situ fusion of the subtalar joint. For those patients with greater than 15° of valgus hindfoot malalignment on a weight-bearing hindfoot alignment view or adjacent joint arthrosis, a triple arthrodesis is recommended with or without medial displacement osteotomy of the calcaneus. Adjacent joint arthrosis may be determined by radiographs, CT scan, or preoperative MRI.

Tarsal coalitions

A tarsal coalition is an aberrant union between 2 or more tarsal bones and can be classified as osseous (synostosis) or nonosseous (cartilaginous [synchondrosis] or fibrous [syndesmosis]). This union may be complete or partial and the joints in the hindfoot and midfoot are most commonly affected. The resulting abnormal articulation presents as a noncorrectable flat foot, usually during adolescence, leading to accelerated degeneration within adjacent joints. An understanding of the condition and presenting symptoms enable the clinician to correctly diagnose and initiate appropriate treatment. This review discusses the evidence-based literature on the cause, diagnosis, and current management of tarsal coalition.

SPECT/CT in imaging foot and ankle pathology-the demise of other coregistration techniques

Disorders of the ankle and foot are common and given the complex anatomy and function of the foot, they present a significant clinical challenge. Imaging plays a crucial role in the management of these patients, with multiple imaging options available to the clinician. The American College of radiology has set the appropriateness criteria for the use of the available investigating modalities in the management of foot and ankle pathologies. These are broadly classified into anatomical and functional imaging modalities. Recently, single-photon emission computed tomography and/or computed tomography scanners, which can elegantly combine functional and anatomical images have been introduced, promising an exciting and important development. This review describes our clinical experience with single-photon emission computed tomography and/or computed tomography and discusses potential applications of these techniques.

A review of tarsal coalition and pes planovalgus: clinical examination, diagnostic imaging, and surgical planning

Pediatric pes planovalgus deformity may be classified as flexible or rigid. The rigid pes planovalgus is often a result of a tarsal coalition, which is typically characterized as a painful unilateral or bilateral deformity, frequently associated with peroneal spasm. However, many tarsal coalitions are asymptomatic and demonstrate no peroneal spasm or pes planovalgus deformity. Likewise, the severe pes planovalgus foot type can demonstrate some of the same clinical and radiographic features of a tarsal coalition, especially in the obese adolescent patient. Also, peroneal spasm may occur in the noncoalesced foot, making diagnosis and etiology more difficult to elucidate. The authors believe that many patients with a pes planovalgus deformity lie in this "gray zone": somewhere between the frank osseous coalition and the flexible pes planovalgus. The "step-forward Hubscher maneuver" is introduced as an effective means of evaluating the flexibility of a pes planovalgus foot by negating the effects of a gastrocnemius or gastrocnemius-soleus equinus. This article focuses on the clinical examination and findings of specific imaging studies to assist in an accurate diagnosis of these complicated patients. This will also help to reveal the various surgical options that are appropriate for the individual patient. Emphasis is placed on computerized tomography (CT) imaging and offers enhanced methods for ordering this test to specifically evaluate middle facet coalitions of the subtalar joint. The authors also introduce "lateral tarsal wedging," an image finding associated with severe deformities, the implications of this finding, as well as its impact on surgical planning.

Tarsal coalitions: etiology, diagnosis, imaging, and stigmata

Tarsal coalition is a congenital condition characterized by the aberrant union (osseous or fibrous) between 2 bones in the rearfoot, most commonly talocalcaneal coalition, calcaneonavicular coalition, and talonavicular coalition, that results in a restriction or absence of motion. The association between tarsal coalition and a variety of coexisting conditions has been reported over the past 60 years and continues to be better understood. These coexisting conditions (the stigmata of tarsal coalition) have been believed to be secondary effects of the coalition and/or fixed rearfoot position. Advanced imaging has provided significant insights into the concomitant pathology and understanding of tarsal coalition that the symptoms associated with tarsal coalition can be present for a myriad of different reasons. One should consider all the stigmata of tarsal coalition when considering a surgical reconstruction.

Radiographic diagnosis of tarsal coalition

OBJECTIVE

The objective of this study was to evaluate the sensitivity of unenhanced radiographic diagnosis of tarsal coalition.

MATERIALS AND METHODS

The study had two phases. The first was a retrospective case and control review. Radiographs of 37 feet (15 talocalcaneal coalitions and 15 calcaneonavicular coalitions) and of 17 patients with foot pain and no coalition used as controls were reviewed independently by three observers who had no prior knowledge of the cases. Each observer reviewed the cases for individual signs of coalition and then decided if coalition was present. The second phase of the study was a prospective evaluation by a single observer of 150 consecutive weightbearing foot radiographs obtained to evaluate nontraumatic foot pain. Patients diagnosed as positive for coalition underwent CT.

RESULTS

On retrospective review of unenhanced radiographs, observers achieved 100% sensitivity and 88% specificity in the diagnosis of talocalcaneal coalitions. Sensitivity and specificity for calcaneonavicular coalitions ranged from 80% to 100% and 97% to 98%, respectively. Several previously unpublished radiographic signs increased sensitivity of diagnosis. For calcaneonavicular coalition, the new signs were altered navicular morphology and visualization of the bar on the anteroposterior radiograph. For talocalcaneal coalition, the new signs were a dysmorphic sustentaculum tali, nonvisualization of the middle subtalar facet, and shortening of the talar neck. In the prospective phase of the study, three talocalcaneal coalitions were detected with no false-positive results.

CONCLUSION

Routine anteroposterior and lateral unenhanced radiographs are a valuable screening tool for tarsal coalition, even when used by inexperienced observers. The newly described signs increase sensitivity of radiographic diagnosis.

“Absent Middle Facet”:A Sign on Unenhanced Radiography of Subtalar Joint Coalition

OBJECTIVE

We compared the accuracy of the previously unevaluated "absent middle facet" sign with the more commonly used "talar beak" sign and C sign for the detection of coalition of the subtalar joint middle facets on lateral foot radiographs obtained with the patient standing.

MATERIALS AND METHODS

Three musculoskeletal radiologists graded the visibility of these three signs on standing lateral radiographs of 32 feet that had been proven to have coalitions of the middle facets of the subtalar joint and 62 feet that had normal subtalar joints. The reviewers were unaware of the presence or absence of subtalar coalitions in these feet.

RESULTS

The absent middle facet sign had a sensitivity, specificity, and accuracy of 75%, 98%, and 90%, respectively, for the diagnosis of subtalar joint coalition in this patient population, whereas these values were 56%, 100%, and 85% for the C sign and 53%, 90%, and 78% for the talar beak sign, respectively. A finding of either a positive absent middle facet sign or a positive C sign resulted in a sensitivity, specificity, and accuracy of 84%, 98%, and 94%, respectively.

CONCLUSION

In this study population, the absent middle facet sign was more sensitive than and nearly as specific as the talar beak sign and C sign for diagnosing subtalar coalition on standing lateral foot radiographs. The highest accuracy was obtained when a finding of either a completely absent middle facet or a complete C sign was considered as a positive indicator of a subtalar coalition.