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

For metatarsalgia caused by a dislocated lesser metatarsophalangeal (MTP) j oint and isolated over-long lesser metatarsals, surgical treatment options without sacrificing the joint are limited. Recently, the Well osteotomy has been advocated for the treatment of this deformity. In our experience, pre liminary results with this technique have revealed a high rate of dorsiflex ion contracture of the MTP joints at follow-up. We performed a cadaver stud y and a three-dimensional analysis on sawbones to investigate this phenomen on. 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, and plantar fascia, was removed en bloc. After gross anatom ic structures were photographed, a Well osteotomy was performed at 25 degre es relative to the long axis of the metatarsal shaft. The positions of musc les, ligaments, and tendons were noted and photographed before and after th e osteotomy. In the sawbones portion of this study, a Weil osteotomy was performed at fo ur different angles (25 degrees, 30 degrees, 35 degrees, and 40 degrees) re lative to the long axis of the metatarsal. To ensure reproducibility, the s awbone models were fixed proximally to a vertical milling machine with the second metatarsals inclined 15 degrees to simulate the anatomic position. A fter making the cut, the plantar fragment was translated along the dorsal f ragment proximally for a distance of 5 mm. Before and after the osteotomy, selected x, y, and z coordinates were obtained using a Microscribe 3D digit izer. Data analysis was performed with Microsoft Excel, and ANOVA was used to determine significant differences (p < 0.05) between the various osteoto mies. Analysis of the cadaver dissection revealed that after the Well osteotomy, the tendons of the interosseous muscles move dorsally with respect to the a xis of the MTP joint due to the depression of the plantar fragment of the m etatarsal. The loss of their flexion effect on the joint permits the pull o f the extensor to dorsiflex the toe. The size of the depression for the var ious osteotomies averaged: 25<degrees> osteotomy, 3.03 mm (range, 1.8 to 3. 8 mm); 30 degrees osteotomy, 3.2 mm (range, 1.9 to 4.0 mm); 35 degrees oste otomy, 3.5 mm (range, 1.7 to 5.7 mm); and 40 degrees osteotomy, 4.2 mm (ran ge, 2.8 to 6.4 mm). Amounts of shortening relative to the long axis of the metatarsal for the various osteotomies averaged: 25 degrees osteotomy, 5.03 mm (range, 4.77 to 5.30 mm); 30 degrees osteotomy, 4.59 mm (range, 3.47 to 5.19 mm); 35 degrees osteotomy, 4.27 mm (range, 2.87 to 5.00 mm); and 40 d egrees 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, and the interosseous muscles then act more as dorsiflexors t han as plantarfexors.