How Does Lateral Column Lengthening Improve the Medial Longitudinal Arch? Now I Started to Understand!

Abstract

Category: Hindfoot; Other Introduction/Purpose: Since its description by Evan for correction of overcorrected clubfoot cases, lateral column lengthening (LCL) has been widely used for correction of pes planovalgus deformity of any etiology, including flexible flat foot deformity in adolescents and adults, either as a solitary procedure or in combination with other bony or soft tissue procedures. The main indication is correction of forefoot abduction manifested radiologically as talonavicular uncoverage. Different techniques were described including Evan and Hintermann techniques. It was reported by many authors that LCL improved forefoot abduction and talonavicular uncoverage, but it was also noticed that LCL corrects the flattening of medial longitudinal arch. The mechanism by which LCL corrects the medial longitudinal arch is still not clearly understood. It was also reported that LCL is associated with forefoot supination, but the exact mechanism of supination is not understood. This study aimed to try to understand the mechanism by which LCL changes the shape of the foot. Methods: LCL osteotomy using Hintermann technique was performed in ten fresh frozen below knee cadaveric specimens. After completion of the osteotomy, the talus and leg were removed to monitor how the foot moves under the talus with opening of the osteotomy to change the shape of the foot. After that, the whole plantar skin was removed and plantar ligaments were dissected to study the influence of plantar ligaments on the plane of motion of the osteotomy and the effect of the osteotomy on plantar ligaments. Results: With opening of the osteotomy, the distal portion of the foot did not move in pure adduction as might be expected. Instead, it moved medial and plantar, and the osteotomy worked as a dorsolateral opening wedge osteotomy meaning that the osteotomy opened laterally but not medially, and dorsally but not inferiorly. The result was that the distal portion was adducted and plantar flexed, so it can correct the forefoot abduction and the flat arch. Because the osteotomy opens dorsally and laterally only, with no opening medially or inferiorly, the lateral part of the distal portion was plantar flexed more than the medial part, and this is the cause of forefoot supination. After dissection of the plantar ligaments to understand their influence on the osteotomy, it was found that the long and short plantar ligaments prevent the osteotomy from opening inferiorly and force it to work as a dorsolateral opening wedge. It was possible to move the distal portion in pure adduction only after cutting the long and short plantar ligaments. As the osteotomy worked as a dorsolateral opening wedge, the plantar fascia which is plantar and medial was relaxed after opening of the osteotomy. Conclusion: May be this can explain how the LCL osteotomy corrects the flat medial longitudinal arch and how it causes supination and lateral side overload. Based on this study, Cotton osteotomy may be needed to be added to LCL to correct the supination. Also, plantar fascia tightening cannot be the cause of medial longitudinal arch correction as it actually becomes more lax after opening of the osteotomy