To better understand the bony component of pes planus and the means by which the Evans calcaneal lengthening corrects them, we studied the standing radiographs of seven adult patients who had undergone calcaneal lengthening to treat symptomatic pes planus. Weightbearing AP and lateral views done preoperatively and postoperatively were used for the study. For each set of films, the following parameters were measured: on the lateral view; overall length of the calcaneus, lateral talometatarsal angle, lateral talocalcaneal angle, and the calcaneal pitch angle; and on the dorsoplanar view, the talometatarsal and talocalcaneal angle. In addition, the relative coverage of the talus by the navicular was described by an angular measurement based on the relationship of the center of the talus to the center of the navicular. The average improvements in lateral talocalcaneal angle (a reflection of hind-foot valgus) was 6.4° when the long axis of the calcaneus was used and 6.8° when the inferior surface of the calcaneus was used for the measurement. The lateral talometatarsal angle improved an average 11.3° (from an average of 19.7° to 8.4°). The dorsoplantar talometatarsal angle (a measure of forefoot adduction/abduction) improved 15.8° (preoperative average 26.8°, postoperative average 11°). The calcaneal pitch angle improved an average 10.8° (preoperative average 3.2°, postoperative average 14°). The relationship between the talus and navicular was defined by an angular measurement based on the center of each articular surface before and after correction using this measurement. An average improvement of 26° occurred in the alignment of these two articular surfaces. This study confirms Evans' belief that significant correction can be obtained by lateral column lengthening, that the relationship between navicular and talus can be restored without fusion, and that the forefoot position corrects without operative intervention to the medial side of the foot. This study also provides numerical guidelines for the surgeon planning surgical correction of symptomatic pes planus, and since bony relationships can be observed before and after correction, some insight may be gained into tarsal morphology of pes planus.
Repeatability analysis of one-dimensional angular-measurement-based stitching interferometry
