Isolated injuries involving the calcaneocuboid joint are rare and frequently overlooked. Indeed, these injuries are a cause of symptoms after an inversion injury of the foot, and the resulting clinical manifestations may mimic a lateral ankle ligament injury, which is more common [1–4]. These injuries predominantly affect young and active persons and are of significant economic importance [1, 2]. Furthermore, patients with injuries involving the calcaneocuboid joint require different treatment approaches than those with the more frequently occurring lateral ankle ligament injury [1]. With a greater understanding of the morphological characteristics of the ligament, an accurate and timely diagnosis can be made, preventing late sequelae from developing and obviating complicated surgical procedures.
The calcaneocuboid joint is formed by the quadrilateral facets of the calcaneus and cuboid bones and the capsule, which is reinforced by ligaments. The four ligaments connecting the calcaneus and cuboid are: the medial calcaneocuboid ligament, a component of the bifurcate ligament; the dorsolateral calcaneocuboid ligament; the plantar calcaneocuboid ligament, or short plantar ligament; and the long plantar ligament [5, 6]. These ligaments play a major role in supporting the medial and lateral longitudinal arches. [7–9] However, the functional roles of the plantar calcaneocuboid ligaments have not been fully considered. It is thought that there are various configurations of the plantar calcaneocuboid ligaments as a factor.
Previous studies [5, 6, 10] referred to the plantar calcaneocuboid ligament that was then subdivided into the long plantar ligament (LPL) and the short plantar ligament (SPL); the SPL is also known as the plantar calcaneocuboid ligament. It is generally agreed that the LPL attaches posteriorly to the inferior surface of the calcaneus between the posterior and anterior tubercles [5]. It has been reported that the superficial fibers insert into the bases of the second to fourth metatarsals (MTs) and not the distal cuboid. Previous studies suggested that the superficial fibers insert variably to the metatarsal bone [6, 11]. One study [6] reported that, in all 59 specimens examined, the LPL had an hourglass shape, and structural variations were observed in the LPL in 20.3% (12 feet), in the form of medial twisting fibers in 11.8% (7 feet), lateral twisting fibers in 3.3% (2 feet), and additional bands in 5% (3 feet). In another study of 10 feet, the shape of the LPL was hourglass to rectangular in 100% [10]. The following morphological data have been reported: length 28.5 ± 10.5 mm [5], 44.2 ± 4.4 mm [6], 38.9 ± 2.1 (lateral) mm [10], and 61.4 ± 24.4 (medial) mm [10]; and width 10.7 ± 2.8 mm [5], 10.9 ± 2.8 mm [6], and 12.2 ± 1.1 mm [10].
The SPL passes anteromedially as a widening band from the anterior tubercle of the calcaneus to attach to the plantar surface of the cuboid posterior to the ridge for the tendon of peroneus longus, and it is often described as blending with and reinforcing the calcaneocuboid joint capsule [5, 6, 10]. Some displayed superficial and deep bands, and in 23 feet (39%) of the 59 specimens, the deep band had a distinct attachment to the calcaneus. [6] The overall shape and arrangement of the SPL was triangular in 21 feet (35%), rectangular in 34 feet (59%), and trapezoidal in 4 feet (6%). In addition, an extra band or bands were also observed in 19 feet (32%), in two of which the extra bands were also twisted [6]. In another study, every SPL had at least two bands: superficial and deep [10]. A rectangular or slightly triangular superficial band was seen in 6 feet (60%), and in the remaining 4 feet (40%), it was triangular with small separate bundles [10]. The following morphological data were reported: length 18.2 ± 4.3 mm [5], 19.4 ± 3.6 mm [6], and 21.0 ± 1.9 mm [10]; width 10.3 ± 4.4 mm [6], 11.2 ± 0.8 mm [10], and 12.2 ± 3.3 mm [5]; and thickness 4.8 ± 0.3 mm [10]. Thus, there are few morphological reports of the plantar calcaneocuboid ligaments, and there is no consensus.
Therefore, the aim of this study was to clarify the differences in morphological features (fiber bundle length, fiber bundle width, fiber bundle thickness) based on differences in the shape and number of LPL and SPL fiber bundles.