Tarsal coalitions typically occur at the talocalcaneal or calcaneonavicular joints. Common findings are pain, limited range of motion, and a pes planus deformity. The focus of this case report includes the presentation, imaging, treatment, and outcomes for a 21-year-old woman diagnosed with a rare lateral cuneocuboid coalition with chronic pain. Clinical and radiographic examinations, typically used to diagnose the common coalition, were unremarkable. Magnetic resonance imaging was diagnostic of the lateral cuneocuboid coalition, which was successfully treated with surgical resection. At 6-year follow-up, she reports resolution of symptoms and has returned to her normal presurgical activity level pain-free. This case is only the third lateral cuneocuboid coalition reported in the literature. The rarity of this coalition and its nonsuspicious clinical presentation make it worthy of acknowledgment.

Tarsal coalition is a condition that exists when a union occurs between two or more tarsal bones and causes restricted motion or absence of motion.1  One of the leading theories regarding the etiology of tarsal coalitions is the failure of differentiation of embryonic mesenchymal tissue. They can also occur as a result of arthritis, infection, neoplasm, or trauma.2  Tarsal coalitions are typically categorized into three types: fibrous, cartilaginous, and osseous.3  Patients with classic talocalcaneal and calcaneonavicular coalition typically present with a rigid pes planovalgus foot type, with pain that is exaggerated with activity, walking, or exercise; patients may also have a history of recurrent ankle sprains.2,3  Pain is likely secondary to mechanical stresses on the joint rather than frank inflammation, as there are abnormalities in normal joint formation.2,4  The talocalcaneal and calcaneonavicular are the two most commonly affected joints.3  Although tarsal coalitions are not uncommon, only two other reports of a lateral cuneocuboid coalition are present in the literature.5,6  Thus, descriptions of clinical presentation and treatment recommendations are sparse. We present a successful case of a surgically resected lateral cuneocuboid coalition that presented with unremitting pain.

Case Report

A 21-year-old female patient presented to the clinic complaining of left foot and ankle pain, which had been present for several years, with no known injury or inciting event. Her only previous treatment modality was an ankle brace that offered little benefit. She had a benign medical history and never had previous foot or ankle surgery. Physical examination revealed normal range of motion about the talonavicular, subtalar, and ankle joints. Tenderness was noted near the sinus tarsi without peroneal spasm or rigid deformity. Plain film radiographs showed no obvious abnormalities. The classic “anteater sign,” C sign, and talar beaking were absent. Conservative treatment efforts, including bracing and anti-inflammatory medication, were attempted but were ineffective; therefore, advanced imaging was ordered to elucidate the etiology of the patient's symptoms. Magnetic resonance imaging (MRI) showed a fibrous coalition of the lateral cuneiform and cuboid, with bone marrow edema on either side of the articulation (Fig. 1). The patient was taken to the operating room with a plan for resection of the coalition. Intraoperatively, the patient was placed in the supine position under general anesthesia, and a thigh tourniquet was used for hemostasis. The lateral cuneocuboid joint was identified using fluoroscopic imaging, and a linear incision was placed at the joint level, after which the extensor digitorum brevis muscle belly was identified and carefully reflected medially. A fibrous coalition at the proximal aspect of the lateral cuneocuboid articulation was resected with an osteotome until trabecular surfaces and cortical margins were exposed. Bone wax was interposed within the joint (Figs. 2 and 3). Postoperatively, the patient remained nonweightbearing for 2 weeks, followed by 4 weeks of protected weightbearing in a controlled ankle motion boot with aggressive physical therapy. At 8 weeks postoperatively, she was returned to full activity. At 6-year follow-up, she reports resolution of symptoms and has returned to her normal presurgical activity level pain-free.

Figure 1

Sagittal T2-weighted magnetic resonance imaging sections revealing a fibrous coalition of the lateral cuneiform and cuboid with associated edema within the bone and soft tissue.

Figure 1

Sagittal T2-weighted magnetic resonance imaging sections revealing a fibrous coalition of the lateral cuneiform and cuboid with associated edema within the bone and soft tissue.

Figure 2

Anteroposterior radiograph obtained following cuneocuboid coalition resection with bone wax interposition.

Figure 2

Anteroposterior radiograph obtained following cuneocuboid coalition resection with bone wax interposition.

Figure 3

Lateral radiograph following cuneocuboid coalition resection with bone wax interposition.

Figure 3

Lateral radiograph following cuneocuboid coalition resection with bone wax interposition.

Discussion

Cuneocuboid coalition is rare, and to our knowledge there are only two prior reports.5,6  Person and Lembach briefly mention one patient with lateral cuneocuboid coalition who was treated with semirigid orthoses.5  There was no mention of treatment outcome and there was no long-term follow-up. The other report was by Imai et al, which described a nonosseous coalition that presented with pain with passive plantar flexion in the posterior aspect of the lateral malleolus.6  There was tenderness detected in the peroneus brevis tendon and sinus tarsi. Plain radiographs showed irregularity of the cortical margins at the articular surfaces of the lateral cuneocuboid joint on the medial oblique view. Computed tomography showed these cortical irregularities but without distinct osseous bridging. An MRI scan revealed an irregular surface with soft-tissue continuation of the lateral cuneocuboid joint on the coronal view consistent with a fibrous coalition. Treatment was successful, with resection and interposition of bone wax.6  In the case of cuneocuboid coalition, the literature is sparse regarding patient symptoms and physical examination findings. In the present case, our patient did not present with rigid forefoot or rearfoot, peroneal spasms, loss of medial longitudinal arch, abnormal gait examination, or other clinical signs of tarsal coalition.2,6,7 

On most occasions, plain radiographs will provide enough information to make the diagnosis of tarsal coalition. Specifically, calcaneonavicular coalitions demonstrate an enlargement of the anterior process of the calcaneus, also known as the anteater sign,7,8  whereas hallmark signs of talocalcaneal coalitions include the C sign, which is formed by continuity of the inferomedial border of the talus with the sustentaculum tali and talar beaking on lateral views.7,8  Talocalcaneal coalitions can display an enlarged and rounded interior contour on lateral views and obliquity of the middle facet on Harris-Beath views.8  Talar beaking is an indirect sign of tarsal coalition that results from abnormal weightbearing mechanics at the talocalcaneal joint.3  Although these radiographic findings are nearly pathognomonic for calcaneonavicular and talocalcaneal coalitions, the absence of radiographic findings cannot be used to reliably exclude the presence of lateral cuneocuboid coalition. In the present lateral cuneocuboid coalition, standard radiographic imaging did demonstrate normal findings. It is possible that marked superimposition of the cortical margins of the lateral cuneiform and cuboid could mask the appearance of an underlying coalition.

In cases where plain radiographs do not show obvious signs of coalition, advanced imaging should be pursued. An MRI scan is beneficial to elucidate etiologic factors and sources of pain, and to evaluate any unsuspected lesions. Indeed, the diagnosis of lateral cuneocuboid coalition in our case was made with MRI. Magnetic resonance imaging of coalitions often shows bone marrow edema, subchondral cyst formation, and/or associated soft-tissue swelling in the involved joints, with findings varying depending on whether the coalition is osseous, fibrous, or cartilaginous.2,3,7,8  In the presented case, MRI showed bone marrow edema in the cuboid and lateral cuneiform, with evidence of fibrous coalition. Some investigators have advocated computed tomography over MRI because of thinner imaging slices and the ability to reveal arthritic changes. However, in our patient, arthritis in the affected joint or surrounding joints was unlikely given the patient's age. A computed tomographic scan likely would have been unremarkable, as was the case for Imai et al.6 

Surgical treatment will vary depending on the location of the coalition and extent of arthritic changes, but goals should include restoring motion and function and minimizing pain. A retrospective review by Scott and Tuten determined that young patients without deformity are typically treated successfully with surgical resection.9  Various surgical resection options are available, including interposition of fat, muscle, or bone wax.3-6,9-15  However, symptom recurrence after excision of a tarsal coalition occurs in approximately 20% of cases.16  Bone wax was used in our case to prevent bleeding and therefore postoperative fibrosis and ankylosis.17 

Previously reported cases presented with peroneal spasm and limited range of motion. However, the clinical and radiographic presentation of the present case report was in stark contrast to these reports. Therefore, this case report highlights the lack of knowledge and literature regarding this type of coalition. Our case report is an example of a fibrous lateral cuneocuboid coalition successfully diagnosed with MRI and treated surgically with resection and bone wax interposition. At 6-year follow-up, the patient has no pain and is back to her normal activities. It is our hope that this case report can offer insight into successful management of this rare type of coalition. The rarity of this coalition and unsuspecting clinical presentation make it worthy of acknowledgment.

Financial Disclosure: None reported.

Conflict of Interest: None reported.

References

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