Lateral Column Lengthening (Evans Osteotomy)

Indication. Symptomatic flexible flatfoot (stage II posterior tibial tendon dysfunction, PTTD) with forefoot abduction and talonavicular uncoverage greater than 40 percent on a weight-bearing AP radiograph, persistent medial arch collapse and activity-limiting pain that has failed a fair trial of orthotics and physical therapy — usually as part of a comprehensive reconstruction with MDCO and an FDL transfer. Relative indications include an adolescent or young adult with progressive symptomatic flexible flatfoot, and isolated residual forefoot abduction producing symptoms after a previous hindfoot correction. Assess the whole deformity before committing. Lateral column lengthening corrects forefoot abduction and talar head coverage — it does not correct hindfoot valgus or restore the posterior tibial tendon. Decide whether the foot is genuinely flexible and whether the hindfoot, the spring ligament and any equinus contracture also need addressing at the same sitting.

Relative contraindications to weigh carefully are smoking or poorly controlled diabetes (optimise first, or consider allograft with supplemental fixation), previous subtalar or calcaneal surgery that distorts the landmarks, and any patient unable to comply with a 6 to 8 week non-weight-bearing protocol. Consent specifically for sural nerve injury (3 to 7 percent), peroneal tendon irritation, calcaneocuboid arthritis (3 to 5 percent), graft nonunion (5 to 10 percent), overcorrection with lateral column pain, and the need for non-weight-bearing for 6 to 8 weeks. Setup. Supine with a bump under the ipsilateral hip to internally rotate the leg, or lateral decubitus if combined with medial procedures. Apply a thigh tourniquet, and prep and drape the foot free. General or spinal anaesthesia with popliteal and saphenous blocks gives good post-operative analgesia. Position the C-arm for AP, lateral and oblique views — and plan for a simulated weight-bearing AP view (plantar pressure on the forefoot), which is essential to judge talonavicular coverage intra-operatively.

The goal is to lengthen the lateral column of the calcaneus through an anterior (Evans) osteotomy, distracting it with a structural trapezoidal graft until the navicular covers the talar head, while protecting the sural nerve and peroneal tendons and staying out of the calcaneocuboid and subtalar joints. The exposure is laid out in the steps below.

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Rehabilitation | Phase | Timing | Immobilisation & weight-bearing | Therapy | |-------|--------|--------------------------------|---------| | 1 | 0 to 6 weeks | Non-weight-bearing in a below-knee cast or removable boot | Elevation and ice for swelling; sutures out at 2 weeks; gentle ankle and subtalar range of motion out of the cast at 4 weeks if the graft is stable | | 2 | 6 to 12 weeks | Transition to partial then full weight-bearing in a boot by 10 to 12 weeks, with radiographic confirmation of graft position | Custom orthotic with medial arch support and lateral forefoot posting; begin strengthening and proprioception | | 3 | 3 to 6 months | Return to normal footwear with an orthotic | Full activities by 4 to 6 months; monitor for lateral column pain or CC joint symptoms at each visit | Return to function. Sedentary work at 8 to 10 weeks, manual labour at 4 to 6 months, and sport at 6 to 9 months with orthotic support. Adolescents often return to sport faster (4 to 6 months). Complications

Pathoanatomy. Posterior tibial tendon dysfunction is the most common cause of adult acquired flatfoot deformity, typically presenting in women over 40. The posterior tibial tendon fails first, the spring ligament and deltoid attenuate, and unopposed peroneal brevis pulls the forefoot into abduction, uncovering the talar head and collapsing the medial arch. Stage II disease — a flexible hindfoot with valgus, forefoot abduction and the too-many-toes sign — is the setting in which lateral column lengthening is used; the rigid stages need arthrodesis instead.

Biomechanical rationale. Lengthening the lateral column restores the medial longitudinal arch by increasing the distance between the calcaneus and the forefoot, reducing forefoot abduction and improving navicular coverage of the talar head. Cadaveric studies show that a 6 to 8 mm lengthening reduces talonavicular uncoverage from about 50 percent to less than 20 percent and raises the medial cuneiform height by 4 to 6 mm. Clinical outcomes. Performed as part of a comprehensive reconstruction (MDCO plus lateral column lengthening plus FDL transfer), AOFAS scores rise from the low 40s pre-operatively to the mid-80s at two years, with union rates exceeding 90 percent for tricortical autograft. Isolated lateral column lengthening without correcting hindfoot valgus gives inferior results and higher revision rates.

Adolescent flexible flatfoot. Lateral column lengthening is particularly effective in adolescents with progressive symptomatic flexible flatfoot; Mosca's long-term data support excellent durability when it is performed before skeletal maturity. Smaller grafts (5 to 7 mm) often suffice because of ligamentous laxity, autograft is preferred and well tolerated, and it may be combined with a medial reefing or Kidner procedure when the navicular is prominent. Good to excellent results exceed 90 percent at 10 to 15 years when graft size is controlled and the soft tissues balanced. Key evidence. Mosca (2010) reported greater than 90 percent good-to-excellent results at up to 15 years in adolescents with controlled graft size. Dolan (2007) showed AOFAS improvement from 42 to 84 when lateral column lengthening was combined with MDCO and FDL transfer. Thomas (2001) demonstrated that grafts greater than 10 mm produce calcaneocuboid subluxation and increased joint pressure. Vora (2006) found autograft union of 97 percent versus allograft 87 percent with equivalent clinical scores at two years, and Haas (1998) showed that deliberate sural nerve identification reduces neuritis from 15 percent to 3 percent.