Tarsal Coalition Resection - Calcaneonavicular and Talocalcaneal

Indication. A symptomatic tarsal coalition in a child or adolescent — typically aged 10 to 16 years — with hindfoot pain (sinus tarsi or medial arch) worse with activity and sport, a rigid flatfoot with restricted subtalar motion, and peroneal spasm, that has failed conservative treatment (activity modification, a University of California Biomechanics Laboratory-style orthotic with a medial arch support and heel cup, NSAIDs, and physical therapy). Symptoms usually begin only as the bar ossifies and becomes rigid; around 25 percent of coalitions remain asymptomatic and are incidental findings. Clinical assessment. Ask about bilateral symptoms and family history (autosomal dominant inheritance with incomplete penetrance). On examination look for: - A rigid pes planovalgus, medial talar-head prominence, and a "too many toes" sign viewed from behind.

• Restricted subtalar motion (inversion and eversion limited to 0 to 10 degrees versus a normal 20 to 30 degrees) with normal ankle dorsiflexion and plantarflexion — the finding that separates coalition from ankle pathology.
• Sinus tarsi tenderness (suggesting a CN bar) or sustentaculum tenderness (suggesting a TC bar).
• A negative Jack test (dorsiflexing the great toe does not restore the arch, confirming rigidity).
• Peroneal spasm: attempted inversion provokes peroneal contraction and pain. Document intact neurovascular status, including tibial nerve function. Peroneal "spastic" flatfoot is a misnomer — the peroneals are tight rather than in true spasm; they contract to stabilise an unstable valgus hindfoot. Imaging protocol. Weight-bearing plain radiographs come first (AP, lateral, 45-degree oblique foot, and a Harris axial view). The CT scan is the gold standard — it confirms the diagnosis, defines the bar type (osseous, cartilaginous or fibrous), measures the proportion of the facet involved, locates the bar (middle versus posterior facet for TC), and assesses the adjacent joints for arthritis. MRI is the best adjunct for cartilaginous or fibrous bars in younger patients and for marrow oedema, but its bone detail is inferior to CT for surgical planning.

The 50-percent guide is not absolute. The classic "less than 50 percent of the posterior facet" cutoff (Wilde, 1994) is a useful guide, but the 2023 systematic review (Polt) found coalition size was not a strong determinant of outcome — selection should weigh arthritis, heel valgus and symptoms rather than a single percentage, and there is increasing interest in resecting larger or recurrent bars in motivated young patients to preserve subtalar motion and defer arthrodesis. Surgical planning checklist. CT reviewed (bar type, size, location confirmed); adjacent joints assessed (no arthritis on CT); hindfoot alignment measured (plan an adjunctive osteotomy if severe valgus); bilateral assessment (check the contralateral foot); interposition material planned (EDB or fat for CN; fat or wax for TC); consent covers nerve injury, recurrence, the possible need for fusion and possible osteotomy; equipment ready (image intensifier, 10 to 15 mm osteotomes, retractors, loupe magnification). Consent specifically for sural or superficial-peroneal-branch numbness or a painful neuroma, recurrence (10 to 20 percent), persistent flatfoot needing a later osteotomy, the small chance of progression to fusion, wound problems and CRPS. Setup. For a CN bar the patient is supine with a bump under the ipsilateral hip to internally rotate the limb for lateral access, the knee flexed 30 to 45 degrees, and a thigh or calf tourniquet (250 to 300 mmHg). For a TC middle-facet bar the patient is supine for the medial approach (lateral decubitus if a lateral sinus-tarsi approach to a posterior-facet bar is planned). An image intensifier is essential throughout, and loupe magnification (2.5 to 3.5 times) is mandatory for nerve identification.

The goal is to completely excise the bar, protect the adjacent nerves, vessels and the healthy subtalar joint, restore subtalar motion, and interpose tissue across the gap to prevent re-ossification. The exposure is laid out in full as the first steps of each timeline below. There are two distinct operations: the CN bar through a lateral (Ollier) approach, and the TC bar through a medial approach.

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Rehabilitation | Phase | Timing | Immobilisation | Therapy | |-------|--------|----------------|---------| | 1 | 0-2 weeks | Below-knee cast or walking boot (hindfoot neutral, slight inversion) | Elevation 48-72 hours; finger and toe range of motion only | | 2 | 2-6 weeks | Cast removed at 2-4 weeks; transition to walking boot or supportive shoe | Subtalar inversion and eversion, ankle motion, toe curls (start 2-4 weeks) | | 3 | 6-12 weeks | Boot for heavy tasks; custom orthotic (medial arch support, heel cup) | Peroneal and intrinsic strengthening; proprioception | | 4 | 3-4 months | Orthotic continues (often 6-12 months) | Jogging, sport-specific drills, graded return to sport | If a calcaneal osteotomy was added, the patient is non-weight-bearing for 6 weeks, then progresses to weight-bearing in a boot from weeks 6 to 10. Most patients return to light sport at 3 to 4 months once they are pain-free, have subtalar motion at 80 percent of the other side and strength at 85 percent, and pass a single-leg hop test at greater than 90 percent. Follow up at 2 weeks (wound check), 6 weeks, 3 months, 6 months and 1 year with radiographs; monitor the contralateral foot, which may become symptomatic later. Outcomes (verified ranges). CN bar resection gives high rates of good or excellent results and return to sport with adequate interposition — around 87 percent return to sport and around 5 percent reoperation in Mubarak's fat-graft series. TC bar resection is historically a little lower and more dependent on facet involvement, heel valgus and adjacent arthritis (Comfort and Johnson around 77 percent good or excellent when the coalition involved one third or less of the joint; Luhmann mean AOFAS around 82). Pooled open resection with interposition gives improved patient-reported outcomes in around 78.8 percent with around 4.96 percent complications (Polt, 2023). Recurrence or re-ossification is low with complete resection plus adequate interposition, and rises with incomplete resection or no interposition. Complications

Epidemiology. Tarsal coalition is present from birth (a failure of mesenchymal segmentation) and remains cartilaginous or fibrous until adolescence. It ossifies between 8 and 16 years — CN bars earlier than TC bars — which is why symptoms begin then. It is bilateral in 50 to 60 percent of patients (examine both feet), follows autosomal dominant inheritance with incomplete penetrance, and around 25 percent remain asymptomatic. Pathophysiology of the rigid flatfoot. The coalition restricts subtalar motion (normal 20 to 30 degrees of inversion and eversion falls to 0 to 10 degrees). A compensatory hindfoot valgus develops, the peroneals contract to stabilise the unstable hindfoot (peroneal spasm), and the talar head is uncovered medially (the "too many toes" sign). Secondary changes follow: talar beaking in around 25 percent (a dorsal talar-neck osteophyte from altered mechanics), a ball-and-socket ankle in around 5 percent (a compensatory change), and midfoot arthritis in chronic cases. Coalition types and distribution. Calcaneonavicular and talocalcaneal bars together account for about 90 percent of coalitions.