Background

In the presence of pain over the lateral aspect of the foot or recurrent ankle sprain in children, medical imaging is often employed to investigate potential causes, such as a calcaneonavicular coalition or a too-long anterior process (TLAP) of the calcaneus. Diagnosis and categorization of calcaneonavicular coalitions (synostosis, synchondrosis, or synfibrosis) is generally facilitated through imaging, in contrast to TLAP, which lacks well-defined semiological characteristics, apart from a calcaneonavicular space measurement of less than 5 mm. However, this measurement initially performed on an oblique view radiograph can be subject to a lack of precision due to positional variations of the foot and overlapping bones. Furthermore, the differentiation between TLAP as an anatomical variant and TLAP syndrome (characterized by symptomatic presentation), remains a subject of uncertainty.

Objective

The objective of our retrospective study was to investigate the imaging diagnosis of TLAP syndrome.

Materials and methods

A retrospective unmatched case-control study was conducted, covering data from February 2014 to January 2021. All patients, included retrospectively and consecutively, were initially managed in our hospital with radiography and/or computed tomography (CT) and/or magnetic resonance imaging (MRI). Two radiologists independently reviewed the images taken (radiographs, CT scans, and MRIs) of patients undergoing treatment in pediatric orthopedics for TLAP syndrome and control subjects, utilizing a standardized questionnaire. The control group consisted of subjects with no features suggestive of TLAP syndrome. The questionnaire included measurements of the calcaneonavicular space and identification of indirect signs associated with calcaneonavicular coalitions, as described in the related literature.

Results

A total of 128 patients who met the inclusion criteria were included in the analysis, including 38 patients and 90 controls. The prevalence of TLAP was 71.5% in the study population and 62.6% among controls. A threshold measurement of the calcaneonavicular space at 3.2 mm favored TLAP syndrome (sensitivity=97%, specificity=70%, area under the curve [95% confidence interval] =0.881[0.812–0.949]), with better precision using CT. Three indirect signs were significant: the “anteater nose” sign, the talar beak, and the tapered anterior calcaneal process. These signs demonstrated an even stronger association with TLAP syndrome when observed in conjunction with a reduction in the calcaneonavicular space, particularly in CT scans.

Conclusion

TLAP is common among control subjects. Therefore, a variant appears to be the most plausible explanation and it can be considered a mild form of calcaneonavicular coalition. However, in conjunction with symptoms suggestive of TLAP syndrome, the diagnosis is further supported by imaging, specifically with a calcaneonavicular space measurement of less than 3.2 mm. This measurement is most accurately obtained using CT with 2-dimensional reconstructions in all three planes. The simultaneous presence of the “anteater nose” sign, the talar beak, or the tapered anterior calcaneal process provides additional diagnostic evidence. In the diagnostic approach of calcaneonavicular coalition, oblique foot radiography seems useful in initially detecting abnormal coalition (bony or not), and complementarily, CT emerges as the best modality to characterize TLAP syndrome.

Graphical Abstract

中文翻译：

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儿童青少年前突过长综合征的影像学特征

背景

当儿童出现脚外侧疼痛或反复发生踝关节扭伤时，通常采用医学影像来调查潜在原因，例如跟骨联合或跟骨前突 (TLAP) 过长。跟舟联合（骨联结、软骨联合或纤维化）的诊断和分类通常通过影像学来促进，而 TLAP 则相反，TLAP 除了跟舟间隙测量值小于 5 毫米外，缺乏明确的症状学特征。然而，由于足部和重叠骨骼的位置变化，最初在斜视图射线照片上进行的测量可能会缺乏精度。此外，TLAP 作为一种解剖变异与 TLAP 综合征（以症状表现为特征）之间的区别仍然是一个不确定的主题。

客观的

我们回顾性研究的目的是探讨 TLAP 综合征的影像学诊断。

材料和方法

进行了一项回顾性、非匹配病例对照研究，涵盖 2014 年 2 月至 2021 年 1 月的数据。所有患者（回顾性连续纳入）最初均在我院接受放射线摄影和/或计算机断层扫描 (CT) 和/或磁共振成像（核磁共振成像）。两名放射科医生使用标准化问卷独立审查了接受 TLAP 综合征儿科骨科治疗的患者和对照受试者的图像（放射线照片、CT 扫描和 MRI）。对照组由没有提示 TLAP 综合征特征的受试者组成。调查问卷包括跟舟间隙的测量以及与跟舟联合相关的间接体征的识别，如相关文献中所述。

结果

共有128名符合纳入标准的患者纳入分析，其中包括38名患者和90名对照。研究人群中 TLAP 的患病率为 71.5%，对照组中的患病率为 62.6%。跟舟间隙的阈值测量为 3.2 mm，有利于 TLAP 综合征（敏感性 = 97%，特异性 = 70%，曲线下面积 [95% 置信区间] = 0.881 [0.812–0.949]），使用 CT 的精度更高。三个间接标志很重要：“食蚁兽鼻子”标志、距骨喙和锥形前跟骨突。当与跟舟间隙缩小结合观察时，这些体征与 TLAP 综合征的关联性更强，尤其是在 CT 扫描中。

结论

TLAP 在对照受试者中很常见。因此，一种变异似乎是最合理的解释，并且可以被认为是跟舟联合的温和形式。然而，结合提示 TLAP 综合征的症状，影像学进一步支持诊断，特别是跟舟间隙测量值小于 3.2 毫米。使用 CT 在所有三个平面上进行二维重建可以最准确地获得此测量值。同时存在的“食蚁兽鼻”征、距骨喙或锥形前跟骨突提供了额外的诊断证据。在跟舟联合的诊断方法中，斜足X线检查似乎有助于初步检测异常联合（骨性或非骨性），并且CT作为补充，成为表征TLAP综合征的最佳方式。

图形概要