Dorsiflexion contracture after the weil osteotomy: Results of cadaver study and three-dimensional analysis

For metatarsalgia caused by a dislocated lesser metatarsophalangeal (MTP) joint isolated over-long lesser metatarsals, surgical treatment options without sacrificing the joint are limited. Recently the Weil osteotomy has been advocated for the treatment of this deformity. In our experience preliminary results with this technique have revealed a high rate of dorsiflexion contracture of the MTP joints at follow-up. We performed a cadaver study a three-dimensional analysis on sawbones to investigate this phenomenon. In the cadaveric portion of this study, the second MTP joints of two fresh-frozen cadavers were dissected; the entire ray, with the metatarsal shaft, MTP joint, toe, plantar fascia, was removed en bloc. After gross anatomic structures were photographed, a Weil osteotomy was performed at 25° relative to the long axis of the metatarsal shaft. The positions of muscles, ligaments, tendons were noted photographed before after the osteotomy. In the sawbones portion of this study a Weil osteotomy was performed at four different angles (25°, 30°, 35°, and 40°) relative to the long axis of the metatarsal. To ensure reproducibility the sawbone models were fixed proximally to a vertical milling machine with the second metatarsals inclined 15° to simulate the anatomic position. After making the cut, the plantar fragment was translated along the dorsal fragment proximally for a distance of 5 mm. Before after the osteotomy, selected x, y, z coordinates were obtained using a Microscribe 3D digitizer. Data analysis was performed with Microsoft Excel ANOVA was used to determine significant differences (p < 0.05) between the various osteotomies. Analysis of the cadaver dissection revealed that after the Well osteotomy, the tendons of the interosseous muscles move dorsally with respect to the axis of the MTP joint due to the depression of the plantar fragment of the metatarsal. The loss of their flexion effect on the joint permits the pull of the extensor to dorsiflex the toe. The size of the depression for the various osteotomies averaged: 25° osteotomy, 3.03 mm (range 1.8 to 3.8 mm); 30° osteotomy 3.2 mm (range, 1.9 to 4.0 mm); 35° osteotomy 3.5 mm (range, 1.7 to 5.7 mm); 40° osteotomy, 4.2 mm (range, 2.8 to 6.4 mm). Amounts of shortening relative to the long axis of the metatarsal for the various osteotomies averaged: 25° osteotomy, 5.03 mm (range, 4.77 to 5.30 mm); 30° osteotomy, 4.59 mm (range, 3.47 to 5.19 mm); 35° osteotomy, 4.27 mm (range, 2.87 to 5.00 mm; 40° osteotomy, 3.65 mm (range, 3.20 to 4.31 mm). According to our analysis depression of the plantar fragment always occurs after a Well osteotomy. This depression changes the center of rotation of the MTP joint, the interosseous muscles then act more as dorsiflexors than as plantarfexors.