Surgical management of an isolated symptomatic talonavicular coalition: a paediatric perspective

Presentation

A 4-year-old girl (now aged 10) was referred by the family practitioner with a medial prominence of the right foot. The child reported mild discomfort without limitation of function. She was otherwise fit and healthy with no relevant family history. Examination yielded a flexible flatfoot with forefoot abduction and a rigid hindfoot. Isolated tenderness was elicited at the medial prominence.

Investigations

The initial radiographs demonstrate a plano-valgus right foot with a complete osseous talonavicular coalition and a prominent medial navicular mass (figures 1 and 2). Bilateral MRI scans were conducted to assess the coalition, identify any associated pathology and compare to the contralateral side (figure 3A,B). There was minimal bone oedema at the site of the coalition, with no associated tendinopathy or evidence of concurrent tarsal coalition.

Figure 1

Weight bearing lateral radiograph of right foot demonstrating talonavicular coalition and pes planus(flatfoot).

Figure 2

Weight bearing anterior-posterior radiograph of right foot demonstrating talonavicular coalition and medial navicular prominence (yellow dotted line).

Figure 3

Sagittal T1 weighted stir MRI of both feet. (A) – right foot demonstrating talonavicular coalition (TNC). (B) – left foot demonstrating normal talonavicular anatomy (T=talus, n=navicular).

Treatment

Initial treatment was non-operative with analgesia and orthotics. The patient developed progressive medial prominence pain, callosity, difficulty with footwear and limitation of sports activity over the ensuing 3 years from her initial clinical encounter. At the age of 7, a shared decision was made to undergo reconstructive foot surgery. Surgical treatment was principled on the pathoanatomical and biomechanical features of the deformity.

The procedure was conducted under general anaesthesia with antibiotic prophylaxis and the use of an intra-operative image intensifier. An Ollier’s incision was utilised and the lateral calcaneus exposed. Two-millimetre Kirschner wires (K-wires) were introduced in a retrograde manner from the distal cuboid into the distal calcaneus, proximal to the proposed osteotomy site, to prevent subluxation of the calcaneo-cuboid joint during lengthening.

The modified Evans calcaneal osteotomy as popularised by Mosca was utilised.11 An oblique, proximal-lateral to distal-medial extra-articular osteotomy of the anterior process of the calcaneus was performed at the isthmus of the calcaneus (narrowest cranio-caudal region). The osteotomy was approximately 2 cm posterior to the calcaneocuboid joint, ending medially between the anterior and middle facets of the subtalar joint. The osteotomy was distracted using laminar spreaders until satisfactory clinical (absence of midfoot break) and radiological correction (coverage of exposed talonavicular coalesced bone by the medial cuneiform) was achieved. The distraction gap was measured at 15 mm and a corresponding graft was harvested. An ipsilateral tricortical trapezoid autologous iliac crest bone graft measuring 15 mm by 20 mm by 5 mm was sited at the osteotomy. The graft was secured by advancing the retrograde K-wires into the proximal calcaneus (figures 4 and 5). The patient was placed in a below-knee cast and advised not to bear weight for 6 weeks. At the end of this period, the K-wires were removed in the clinic and progressive weight-bearing in a walker boot was commenced.

Figure 4

Intra-operative image intensifier picture demonstrating laminar spreader opening calcaneal osteotomy site.

Figure 5

Intra-operative image intensifier picture demonstrating grafted osteotomy site secured with K-wires.

Outcome and follow-up

The patient had an uneventful recovery with post-operative radiographs demonstrating complete graft union and coverage of the medial bony prominence, resulting in resolution of the midfoot break following lateral column lengthening (figure 6). Three years following her right foot procedure she remains asymptomatic with no functional limitation and full participation in physical activities.

Figure 6

20 week post-op anterior-posterior radiograph of the foot demonstrating adequate medial navicular coverage (yellow dotted line) by the medial cuneiform as a result of the lateral column lengthening procedure (red arrow shows the healed lengthening calcaneal osteotomy).