Cavus Foot Deformity with Calcaneonavicular and Medial Cuneiform–Navicular Coalition: A Case Series

Abstract

Tarsal coalitions have only very infrequently been observed in the context of cavus foot abnormalities. Recognizing this diagnosis could be crucial to effective cavus repair. We report tarsal coalitions observed in cavus deformity here. Between 2022 and 2023, the records of every patient treated by one of the authors for a varus deformity who was later determined to have either a unilateral or bilateral tarsal coalition were examined. Two patients with cavus deformities who were treated by one of the authors have either a unilateral or bilateral tarsal coalition. Three foot (medial cuneiform–navicular n = 1 and calcaneonavicular n = 2) with tarsal coalition were examined. All of these cases occurred in patients with idiopathic cavus deformity. Computed tomography scans were used to make a firm diagnosis for each patient. We advise surgeons to keep an awareness for this potential comorbid issue in all cavus foot abnormalities and to take advanced imaging into consideration. In these uncommon cases, the medial cuneiform–navicular and calcaneonavicular joints formed an osseous coalition with pes cavus deformity, which successfully resolved with conservative and surgical treatment, respectively. Level of Clinical Evidence: IV.

Introduction

Foot abnormality known as tarsal coalitions cause an unnatural bridge to develop between two or more tarsal bones causing planus deformity. This coalition's bridging structure, which might be bone, fibrous, or cartilaginous in origin, results from a failure of segmentation and mesenchymal differentiation [1]. Pain reduction and functional improvement are the main targets of tarsal coalition treatment. The initial line of therapy is conservative treatment [2]. For individuals who have not responded to conservative treatment, surgery is the preferred course of action [3]. It is debatable what kind of treatment should be carried out. The most common surgical procedure is a coalition excision and interposition with muscle, fat, or bone wax. In patients with talocalcaneal coalitions, the hindfoot alignment and soft tissue problems must be taken into account [4].

Few cases have been documented in the literature that describe the relationship between tarsal coalition and the cavovarus foot deformity. Three examples, including one calcaneonavicular and two subtalar coalitions, were reported by Stuecker and Bennett [5]. A case of severe cavovarus deformity with talocalcaneal and calcaneonavicular coalitions was described by Charles et al., whereas a case of mild cavus deformity with a single talocalcaneal coalition was described in the left foot [6]. Kurashige and Suzuki present case of tibialis spastic varus foot with calcaneonavicular coalition [7].

In two cases that follows, tarsal coalitions resulted in mild cavovarus foot deformities when the neurologic system was still intact. These odd situations have been rarely documented in the literature to our knowledge. To provide a thorough examination of the pathologic mechanism causing this unusual etiology of cavovarus foot deformity, preoperative fine-wire electromyogram (EMG), magnetic resonance image (MRI), and computed tomography (CT) image were evaluated.

Case 1

A 12-year-old boy who had cavovarus deformity in his right foot arrived at our clinic. The child's parents did not become aware of a noticeable foot abnormality, and his family history was unremarkable. His main symptoms were escalating discomfort in the sinus tarsi area in the right foot, ongoing right ankle sprains, and moderate pain in the left foot. Immobilization in a cast for 5 weeks has failed to provide relief.

A cavus deformity with its apex at the talonavicular level, a stiff talocalcaneal complex in varus position, and a plantarflexed first ray were all seen during a clinical examination of the right foot. The heel of the contralateral foot was aligned varus, while the forefoot was normal (Fig. 1). Dorsiflexion and plantarflexion were each 15° on both sides. Subtalar joint range of movement was in the range of 5° to 10° in inversion and 0° in eversion, on both sides, respectively. There were not any stiffness of the Achilles–gastrocnemius–soleus complex on both sides. Transverse tarsal motion was restricted. Stressing the coalition by manipulating the subtalar and transverse tarsal joints elicited pain directly at the site between the anterior process of the calcaneus and the navicular. During heel block test, talocalcaneal complex’s varus deformity did not correct to neutral position.

Fig. 1.

Preoperative photographs. A Medial view of the left foot demonstrating mild cavus deformity with apex at talonavicular level. B Medial view of the right foot demonstrating mild cavus deformity with apex at talonavicular level and plantarflexion of the first ray

As physical examination demonstrates cavovarus deformity, the neuromuscular system was tested. The results showed that the leg's muscle strength and reflex patterns were both normal. There was no sign of spastic activity. An underlying neuromuscular illness like Charcot–Marie–Tooth disease was ruled out because the nerve conduction velocities in the lower limbs were normal. The tibialis anterior and posterior muscles in particular showed regular muscular activity without any indications of spasticity in fine-wire EMGs.

Lateral view of the right ankle demonstrates lengthening of the calcaneal anterior process and irregularities of the calcaneal and navicular borders, suggestive of calcaneonavicular coalition on both sides (Fig. 2). It showed specific radiographic changes of calcaneonavicular coalition such as anteater sign [8]. The preoperative oblique radiograph of both sides showed calcaneonavicular bars (Fig. 2). Computed tomography image revealed an osseous calcaneonavicular coalition on both sides (Figs. 3, 4). Secondary osteoarthritic changes were not identified.

Fig. 2.

Preoperative radiographs. A AP radiograph of left foot. B Oblique radiograph of left foot showed calcaneonavicular bar. C Lateral radiograph of the left foot. D AP radiograph of right foot. E Oblique radiograph of right foot showed calcaneonavicular bar. F Lateral radiograph of the left foot

Fig. 3.

Preoperative CT of both feet. A Calcaneonavicular of right foot and B calcaneonavicular coalition of left foot

Fig. 4.

Preoperative CT scan with 3D reconstruction of both feet. A Lateral aspect of left foot; B Medial aspect of left foot; C Medial aspect of right foot; D Lateral aspect of right foot

Due to 5-week unresponsiveness to cast treatment, bilateral coalition resections were deemed necessary to correct deformity. The patient is positioned supine. Operation has begun with right foot. The incision has begun 1 cm distal to the tip of the fibula and has been carried obliquely to the base of the third metatarsal under spinal anesthetic with a thigh tourniquet. The origin of the extensor digitorum brevis muscle has been detached from the lateral surface of the talus and reflected distally. The anterior process of the calcaneus has been identified and traced toward the navicular. The coalition has been identified as a broad surface of bone connecting the anteromedial aspect of the calcaneus to the plantar–lateral portion of the navicular. The parameters of the coalition have been carefully identified to avoid violation of the articular surface of the navicular or the calcaneocuboid joint. For confirmation, the surgeon has used intraoperative fluoroscopy. The ligaments between the talus and navicular and the calcaneus and cuboid have been preserved. With a straight osteotome, the navicular portion of the coalition has been resected with an oblique angle, ensuring that the plantar–lateral portion is resected. The calcaneal portion has been resected with a parallel cut beginning at the superior–medial articular surface of the calcaneocuboid joint. The block of bone and fibrous tissue have been removed as large as 2 cm using these resection margins. Bone wax has been applied to all cut bone surfaces. The tourniquet has been deflated before closure to minimize the risk of hematoma and subsequent scar formation. The extensor fascia has been approximated, as the subcutaneous tissue and skin. A plaster splint limiting inversion and eversion has been applied intraoperatively. Same procedure has been applied to left foot. After coalition resections, the position of talocalcaneal complex relocated physiological valgus position. Additional procedures were not necessary. Plantigrade foot was achieved by this bilateral coalition resection. The postoperative oblique radiograph of both sides showed resected calcaneonavicular bars (Fig. 5).

Fig. 5.

Postoperative radiographs. A Oblique radiograph of left foot showed resected calcaneonavicular bar. B Oblique radiograph of right foot showed resected calcaneonavicular bar

The patient had no subjective functional limits or complaints of pain 5 months after surgery. He could put on regular shoes. Only after soccer matches or lengthy walks was fatigue of the foot and ankle noticed. Coalitions were removed both clinically and radiographically, and the medial arch and hindfoot kept their plantigrade alignment (Fig. 6). There was 15° of dorsiflexion and 15° of plantarflexion in the bilateral passive ankle range of motion. Standing lateral radiographs of bilateral feet postoperatively demonstrated well alignment (Fig. 7). Subtalar joint range of movement was in the range of 15° to 20° in inversion and 10° in eversion, on both sides, respectively.

Fig. 6.

Postoperative clinical photograph showing the plantigrade position of the right foot. A Medial of left foot and lateral of right foot; B Frontal, C medial of right foot and lateral of left foot, and D posterior views

Fig. 7.

Postoperative radiographs: A AP radiograph of right foot; B Lateral radiograph of the right foot; C AP radiograph of left foot; D Lateral radiograph of the left foot

Case 2

A 9-year-old girl who had a slight cavovarus deformity of the left foot arrived at our clinic. Her family history was negative. Her main symptoms were left-side sinus tarsal pain that was getting worse. No additional studies had been conducted.

A minor cavus deformity with its apex at the talonavicular level, a rigid medial cuneiform–navicula complex in varus position, and a plantarflexed first ray were all seen during a clinical examination of the left foot. Subtalar joint range of movement was in the range of 10° to 15° in inversion and 0° to 5° in eversion, respectively. Transverse tarsal motion was restricted. Stressing the coalition by manipulating transverse tarsal joints elicited pain directly at the site between medial cuneiform and the navicula. The forefoot and heel were aligned normally on the other foot (Fig. 8). On both sides, dorsiflexion and plantarflexion were both 20 degrees.

Fig. 8.

Clinical photographs. A Frontal view of the left foot demonstrating mild abduction deformity. B Posterior view showing heel varus deformity of the left foot. C Medial view of the left foot demonstrating cavus deformity with apex at naviculo-cuneiform level and plantarflexion of the first ray

As physical examination demonstrates cavovarus deformity, the neuromuscular system was tested. Testing of the neuromuscular system revealed no evidence of spastic activity, and the leg's muscle strength and reflex patterns were normal. Lower limb nerve conduction velocities were normal, ruling out an associated neuromuscular condition such Charcot–Marie–Tooth disease. The tibialis anterior and posterior muscles in particular showed regular muscular activity without any indications of stiffness in fine-wire EMGs.

Lateral view of the left foot demonstrates lengthening of irregularities of the cuneiform bones and navicular borders, suggestive of cuneiforms–navicula coalition (Fig. 9). Sagittal CT image revealed an osseous medial cuneiform–navicular coalition on left side. Sagittal and axial MRI revealed an osseous medial cuneiform–navicular coalition. T2-weighted with fat suppression images demonstrate at the periphery of coalition adjacent edema (Fig. 10). Secondary osteoarthritic changes were not identified.

Fig. 9.

Radiographs: A Lateral radiograph of the left foot; B Lateral radiograph of the right foot; C AP radiograph of left foot; D AP radiograph of right foot

Fig. 10.

CT and MRI of left feet. A Sagittal MRI of medial cuneiform–navicular coalition demonstrates at the periphery of coalition adjacent edema. B Coronal MRI medial cuneiform–navicular coalition. C CT image of medial cuneiform–navicular coalition

Medial arch supporting and hindfoot alignment preserving shoe insert and analgesics were deemed for treatment. A shoe insert has a recess beneath the first metatarsal head to support the downward bending of the first ray and permit slight eversion of the hindfoot. Additionally, a slanted section in the front of the insert, starting next to the recess under the first metatarsal, extends to the outer edge of the insert to replicate the pronation of forefoot. Treatment were applied 6 weeks to left foot. After 6 weeks, the patient had no complaints of pain or subjective functional limitations.

Discussion

Tarsal coalition should be included in the differential diagnosis of a cavovarus foot deformity without underlying neuropathology [6]. In the presence of tarsal coalition, the pathologic mechanism causing cavovarus foot deformity is complex, and a number of factors may affect the pathology.

The failure of the fetal tarsal’s normal segmentation is the most likely cause of tarsal coalition, despite the fact that its pathogenesis is unknown [9]. Regardless of the presence of a coalition at birth, symptoms usually develop as the child ages. The tarsal coalition may result in anomalous midfoot and hindfoot motion that causes the muscle to become painful [10].

Tarsal coalitions have been described in conjunction with various varus foot abnormalities, including pes varus [11, 12]. It has been postulated that tarsal coalitions can cause a varus deformity by causing the tibialis muscles to spasm [13]. The forefoot is pulled inward and the heel is positioned in a varus position by increased tone in the tibialis posterior muscle. The medial arch is then raised by the tibialis anterior muscle's overpull [6]. A painful varus rearfoot deformity and tibialis muscle spasm forcing the foot into adduction were seen in a case series with three occurrences of calcaneonavicular coalition in adolescents [11]. There was a theory that this spasm would not only impact the peronei muscles but other muscles as well, resulting in a separate clinical deformity from peroneal spastic flatfoot. The tibialis anterior's increased muscle tone and subsequent tendon shortening, according to Barrett and Johnson, may cause the medial arch to rise and result in a cavovarus deformity [14].

According to these findings and the results of the current case series, we do not think that real spasticity of the tibialis anterior and posterior occurs, but we do think that a gradual, modestly elevated muscle tone linked to pain could result in an adaptive shortening of these tendons. As demonstrated in similar abnormalities brought on by neurologic conditions, muscular imbalance most likely does not play a major role in this condition. A shortening of the tibialis posterior tendon could result in a cavus alignment with adduction of the midfoot and forefoot and a varus rearfoot even in the presence of an intact peroneus brevis.

The treatment of tarsal coalition alone is a complex task; adding cavus deformity produces a bigger complexity. Our study demonstrates examples of both conservative and operative treatment methods. Only one-third of patients were found to respond to conservative measures in tarsal coalition with planus deformity [15, 16]. As tarsal coalition with cavus deformity is a very rare disease, treatment modalities for this disease are unclear in the literature. Our cases’ complaints of pain and subjective functional limitations resolved with both conservative and operative treatment methods. Difference of coalition type might have effect on success of treatments.

A medial cuneiform–navicular coalition with cavovarus deformity appears to be very unusual. According to the report, talocalcaneal and calcaneonavicular coalitions make up 48 and 44% of all tarsal coalitions, respectively. Talonavicular and calcaneocuboid coalitions make up 1% each. Other coalitions such as medial cuneiform–navicular coalition accounting for the remaining approximately 6% [17].

Conclusion

Tarsal coalition is a relatively uncommon cause of cavovarus foot deformity, but it should be considered, particularly if the foot hurts without a neurologic explanation. In these uncommon cases, the medial cuneiform–navicular and calcaneonavicular joints formed an osseous coalition with pes cavus deformity, which successfully resolved with conservative and surgical treatment, respectively.

Author Contributions

All authors have read and agreed to this manuscript being submitted for publication. All listed authors meet the criteria, and nobody who qualifies for authorship has been omitted from the list. Contributors have been properly acknowledged, and all authors and contributors have approved their being listed and/or acknowledged. MAI conceived the idea of the study and supervised the IRB proposal, study design, collection of data and wrote the first and edited subsequent drafts. SO and MAG worked in collection and analysis of the data. GU and HS participated in study design and edited the subsequent drafts.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Data availability

A data availability statement is not applicable for this study.

Declarations

Conflict of Interest

The authors have no relevant financial or non-financial interests to disclose.

Ethical Standard Statement

Ethical approval not required as per our institute review board. All procedures performed in this study involving human participants were in accordance with the ethical standard of the institutional and/ international research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Patients and their parents were informed that data concerning the case would be submitted for publication, and they provided consent.