Lateral Column Lengthening (Evans Osteotomy)

Surgical Indications

Absolute Indications

• Symptomatic flexible flatfoot (stage II PTTD) with greater than 40 percent talonavicular uncoverage on weight-bearing AP radiograph
• Persistent forefoot abduction and medial arch collapse after adequate trial of orthotics and physical therapy
• Combined procedure planned with medial displacement calcaneal osteotomy and FDL transfer for comprehensive stage II reconstruction

Relative Indications

• Adolescent or young adult flexible flatfoot with progressive deformity and activity-limiting pain
• Isolated forefoot abduction deformity after previous hindfoot correction where residual uncoverage produces symptoms
• Patient preference for joint-preserving reconstruction over arthrodesis when deformity is flexible

Contraindications

Absolute:

• Rigid flatfoot deformity (stage III or IV) with subtalar or midtarsal arthritis — arthrodesis is required
• Active infection or open wound at the surgical site
• Severe vascular insufficiency precluding wound healing

Relative:

• Smoker or diabetic with poor glycaemic control — optimise before surgery or consider allograft with supplemental fixation
• Previous subtalar or calcaneal surgery that distorts landmarks
• Patient unwilling or unable to comply with non-weight-bearing post-operative protocol

Evidence for Lateral Column Lengthening

Biomechanical Rationale

Lateral column lengthening restores the medial longitudinal arch by increasing the distance between the calcaneus and the forefoot, thereby reducing forefoot abduction and improving talar head coverage by the navicular. Cadaveric studies demonstrate that a 6-8 mm lengthening reduces talonavicular uncoverage from 50 percent to less than 20 percent and increases the medial cuneiform height by 4-6 mm.

Clinical Outcomes

When performed as part of a comprehensive flatfoot reconstruction (MDCO + LCL + FDL transfer), patient-reported outcomes improve significantly. AOFAS scores rise from the low 40s pre-operatively to the mid-80s at two years. Union rates exceed 90 percent with tricortical autograft. Isolated LCL without addressing hindfoot valgus produces inferior results and higher revision rates.

Graft Selection Evidence

Tricortical iliac crest autograft demonstrates the highest union rate (greater than 95 percent) but carries donor-site morbidity (pain, haematoma, nerve injury) in up to 20 percent of patients. Structural allograft union rates range from 85-92 percent with lower morbidity; supplemental bone morphogenetic protein or bone marrow aspirate is often used to augment healing in higher-risk patients.

Key Evidence

Relevant Anatomy for Lateral Column Lengthening

Calcaneal Osteotomy Landmarks

The Evans osteotomy is performed through the lateral wall of the calcaneus approximately 12-15 mm proximal to the calcaneocuboid joint. The anterior calcaneal process forms the distal fragment that is distracted. The osteotomy must remain parallel to the CC joint surface to avoid creating an oblique cut that produces unwanted plantarflexion or varus.

Neurovascular Structures

The sural nerve crosses the lateral calcaneus obliquely from posterior to anterior, lying in the subcutaneous tissue 2-3 cm proximal to the CC joint. It is accompanied by the lesser saphenous vein. The nerve must be identified and protected before any retraction.

The peroneus brevis and longus tendons lie immediately anterior and superior to the lateral calcaneal wall, held by the superior peroneal retinaculum. Elevation of the tendons as a subperiosteal sleeve with the retinaculum protects them during exposure and distraction.

Calcaneocuboid Joint and Ligamentous Restraints

The CC joint capsule and the calcaneocuboid ligament provide the primary stability once the osteotomy is distracted. An osteotomy placed too close to the joint (less than 10 mm) risks capsular disruption and graft instability. The long plantar ligament and plantar fascia insert on the anterior process and must be preserved to maintain arch support.

Talonavicular Joint and Medial Arch

The goal of lengthening is to restore coverage of the talar head by the navicular. On the standing AP radiograph, normal talonavicular coverage shows less than 20 percent uncoverage. In severe flatfoot, uncoverage often exceeds 50 percent. Lengthening the lateral column reduces abduction and improves coverage without directly operating on the medial column.

Positioning and Preparation

Patient position: Supine with a bump under the ipsilateral hip to internally rotate the leg, or lateral decubitus if combined with medial procedures. A thigh tourniquet is applied. The foot is prepped and draped free.

Anaesthesia: General or spinal with regional block. Consider popliteal and saphenous blocks for post-operative analgesia.

Fluoroscopy: C-arm positioned to obtain AP, lateral and oblique views of the foot and ankle. A simulated weight-bearing AP view (plantar pressure on the forefoot) is essential to assess talonavicular coverage intra-operatively.

Consent: Discuss risk of sural nerve injury (3-7 percent), peroneal tendon irritation, CC joint arthritis (3-5 percent), graft nonunion (5-10 percent), overcorrection with lateral column pain, and the need for non-weight-bearing for 6-8 weeks.

Surgical Approach

Incision

A 6-8 cm longitudinal incision is made along the lateral calcaneus, centred over the planned osteotomy site, 1 cm distal to the sural nerve crossing point. The incision begins at the anterior process and extends proximally toward the peroneal tubercle.

Nerve and Tendon Protection

The sural nerve is identified in the subcutaneous plane under loupe magnification and looped with a vessel loop. The peroneal tendons are exposed and elevated subperiosteally as a single sleeve with the superior peroneal retinaculum. A Hohmann retractor is placed on the anterior calcaneal process to maintain the tendons anteriorly and protect them during distraction.

Exposure of the Osteotomy Site

The periosteum is elevated from the lateral calcaneal wall. The CC joint is identified by palpation and confirmed with fluoroscopy. A K-wire is placed 15 mm proximal to the joint and parallel to the articular surface under fluoroscopic guidance. The wire serves as the osteotomy guide.

Osteotomy and Lengthening

Step 1: Perform the Osteotomy

Using a thin oscillating saw, the osteotomy is made parallel to the K-wire from lateral to medial, aiming slightly distal and lateral toward the sinus tarsi floor. The medial cortex is left intact initially and completed with an osteotome to avoid over-penetration into the medial soft tissues.

Step 2: Mobilise the Anterior Fragment

A laminar spreader is inserted into the osteotomy and gently opened. The anterior calcaneal process is mobilised while protecting the peroneal tendons and sural nerve. The long plantar ligament and plantar fascia are preserved.

Step 3: Determine Graft Size

A second laminar spreader or distraction device is used to open the osteotomy until the talar head is adequately covered on the simulated weight-bearing AP fluoroscopic view. The gap is measured. In most adults, 6-8 mm of lengthening is sufficient. Greater than 10 mm is rarely required and risks CC joint subluxation and lateral overload.

Step 4: Prepare and Insert the Graft

A tricortical iliac crest graft is harvested (or allograft prepared) in a trapezoidal shape with the wider base oriented laterally. The graft is impacted into the osteotomy with the cortical surface facing laterally. The anterior fragment is reduced over the graft.

Step 5: Fixation

A 3.5 mm cortical screw is placed from the anterior calcaneal process into the posterior calcaneal body, compressing the graft. Alternatively, a low-profile plate may be used if additional stability is required. The screw should not violate the subtalar joint.

Step 6: Verify Correction and Closure

Final fluoroscopic AP, lateral and oblique views confirm graft position, screw placement and talonavicular coverage. The wound is closed in layers over a drain if needed. A bulky compressive dressing and posterior splint are applied.

Post-operative Protocol

Early Phase (Week 0-6)

• Non-weight-bearing in a below-knee cast or removable boot for 6 weeks
• Elevation and ice for swelling control
• Suture removal at 2 weeks
• Begin gentle ankle and subtalar range-of-motion exercises out of cast at 4 weeks if graft stable

Intermediate Phase (Week 6-12)

• Transition to partial weight-bearing in boot at 6 weeks with radiographic confirmation of graft position
• Progressive weight-bearing to full by 10-12 weeks
• Custom orthotics with medial arch support and lateral forefoot posting if needed
• Begin strengthening and proprioception training

Late Phase (Month 3-6)

• Return to normal footwear with orthotics
• Full activities by 4-6 months
• Monitor for lateral column pain or CC joint symptoms at each visit

Return to Function

• Sedentary work: 8-10 weeks
• Manual labour: 4-6 months
• Sport: 6-9 months with orthotic support

Special Case: Adolescent Flexible Flatfoot

Indications and Timing

Lateral column lengthening is particularly effective in adolescents with progressive symptomatic flexible flatfoot. Mosca's long-term data support excellent durability when performed before skeletal maturity. The osteotomy heals rapidly in this age group and growth remodelling improves the final arch contour.

Technical Modifications

• Smaller graft size (5-7 mm) often sufficient due to ligamentous laxity
• Autograft preferred; donor-site morbidity well tolerated
• Combine with medial reefing or Kidner procedure if navicular prominence present
• Post-operative protocol similar but return to sport often faster (4-6 months)

Outcomes

Greater than 90 percent good to excellent results at 10-15 years when graft size is controlled and soft-tissue balancing performed.

Special Case: Combined Procedures in Stage II PTTD

Lateral column lengthening is almost never performed in isolation for adult acquired flatfoot. Standard reconstruction includes:

1. Medial displacement calcaneal osteotomy (MDCO) to correct hindfoot valgus
2. Lateral column lengthening (Evans) to correct forefoot abduction
3. Flexor digitorum longus transfer to the navicular for posterior tibial tendon reconstruction
4. Spring ligament repair or augmentation when attenuated
5. Gastrocnemius recession if equinus contracture present

The sequence is typically MDCO first, then LCL, then soft-tissue work. Intra-operative simulated weight-bearing views guide graft sizing after the heel is corrected.