A 6-week-old female infant with congenital talipes equinovarus (CTEV) has undergone 4 weeks of serial casting using the Ponseti method. On review, the adductus and varus have been corrected, but residual equinus persists despite appropriate casting. The foot cannot be dorsiflexed beyond 5° plantarflexion. The treating orthopaedist plans a percutaneous tenotomy. Which tendon is being sectioned?

## Percutaneous Tenotomy in Ponseti Method for Residual Equinus ### The Ponseti Casting Sequence The Ponseti method corrects CTEV deformity in a specific order: ```mermaid flowchart TD A["CTEV Deformity<br/>(Equinus + Varus + Adductus)"]:::outcome A --> B["Week 1–2: Correct Adductus<br/>Lateral forefoot pressure"]:::action B --> C["Week 3–4: Correct Varus<br/>External rotation of foot"]:::action C --> D["Week 5–6: Correct Equinus<br/>Dorsiflexion pressure"]:::action D --> E{"Equinus corrected<br/>to 10–15° dorsiflexion?"}:::decision E -->|"No"| F["Percutaneous Achilles<br/>Tenotomy"]:::action E -->|"Yes"| G["Continue casting<br/>+ bracing"]:::action F --> H["Final cast for 3 weeks"]:::action H --> I["Long-term bracing<br/>Dennis-Brown splint"]:::outcome ``` ### Why Achilles Tenotomy? **Key Point:** The **Achilles tendon** (gastrocnemius + soleus) is the primary plantarflexor and is responsible for the **equinus component** of CTEV. After adductus and varus are corrected by casting, residual equinus is due to: - Tight, shortened Achilles tendon - Posterior capsular contracture - Intrinsic plantarflexor muscle tightness ### Technique & Timing | Aspect | Detail | |--------|--------| | **Timing** | After 4–6 casts if equinus not corrected to ≥10° dorsiflexion | | **Method** | Percutaneous (mini-open or needle-based) section at musculotendinous junction | | **Anesthesia** | Local or general (usually general in infants) | | **Post-tenotomy** | Final cast applied for 3 weeks to maintain correction | | **Success rate** | ~95% with Ponseti method + tenotomy | **High-Yield:** Percutaneous tenotomy is **NOT a failure** of the Ponseti method — it is an **integral part** of the protocol. ~80% of CTEV cases require tenotomy. ### Anatomy of the Achilles Tendon - **Formed by:** Gastrocnemius (medial and lateral heads) + soleus muscle - **Insertion:** Calcaneal tuberosity - **Action:** Plantarflexion of the ankle (primary deforming force in equinus) - **Innervation:** S1–S2 nerve roots (tibial nerve) **Clinical Pearl:** The tenotomy is performed **percutaneously** to avoid scar formation and preserve function. The tendon heals by secondary intention within the cast, allowing controlled lengthening. ### Why Not Other Tendons? | Tendon | Role in CTEV | Why Not Sectioned | |--------|--------------|-------------------| | **Tibialis posterior** | Causes varus (inversion) | Addressed by varus correction casting; not needed for equinus | | **Flexor digitorum longus** | Assists plantarflexion | Secondary plantarflexor; Achilles is primary | | **Peroneus longus** | Causes eversion | Not involved in equinus; would worsen valgus | **Mnemonic:** **"ACE for Equinus"** — **A**chilles tenotomy corrects **E**quinus in CTEV.