Lateral column calcaneal lengthening, flexor digitorum longus transfer, and opening wedge medial cuneiform osteotomy for flexible flatfoot: a biomechanical study.

BACKGROUND: Lengthening of the lateral column is commonly used for reconstruction of the adult and pediatric flatfoot, but can result in supination of the foot and symptomatic lateral column overload. The addition of a medial cuneiform osteotomy has been used to redistribute forces to the medial column. The combined use of a lateral column lengthening and medial cuneiform osteotomy in a reproducible cadaver flatfoot model was evaluated.

METHODS: Twelve cadaver specimens were physiologically loaded and each was evaluated radiographically and pedobarographically in the following conditions: 1) intact, 2) severe flatfoot, 3) lateral column lengthening with simulated flexor digitorum longus transfer, and 4) lateral column lengthening and flexor digitorum longus (FDL) transfer with added medial cuneiform osteotomy. The lateral column lengthening was performed with a 10-mm foam bone wedge through the anterior process of the calcaneus, and the medial cuneiform osteotomy was performed with a dorsally placed 6-mm wedge.

RESULTS: Lateral column lengthening with simulated FDL transfer on a severe flatfoot model resulted in a significant change as compared with the flatfoot deformity in three measurements: in lateral talus-first metatarsal angle (-17 to -7 degrees; p<0.001), talonavicular angle (46 to 24 degrees; p<0.001), and medial cuneiform height (16 to 20 mm; p<0.001). Lateral forefoot pressure increased from 24.6 to 33.9 kPa (p<0.001) after these corrections as compared with the flatfoot. Adding a medial cuneiform osteotomy decreased the lateral talar-first metatarsal angle from -7 to -4 degrees, decreased the talonavicular coverage angle from 24 to 20 degrees, and increased the medial cuneiform height from 20 to 25 mm. After added medial cuneiform osteotomy, lateral pressure was significantly different from that of the flatfoot (p=0.01) and was not significantly different from that of the intact foot (p=0.14). Medial forefoot pressure was overcorrected as compared with the intact foot with added medial cuneiform osteotomy.

CONCLUSIONS: Lateral column lengthening increased lateral forefoot pressures in a severe flatfoot model. An added medial cuneiform osteotomy provided increased deformity correction and decreased pressure under the lateral forefoot.