A simple method to predict postoperative relative first metatarsal length after proximal closing-wedge osteotomy

Abstract

Optimal relative first metatarsal length is one of the keys to achieving sufficient results after osteotomy of the first metatarsal. An excessive shortening of the first metatarsal was associated with postoperative metatarsalgia, whereas a long first metatarsal has been implicated as a cause of hallux valgus. To adjust the relative first metatarsal length to the optimal range during surgery, a predictive tool would be beneficial for preoperative planning. However, there is no established tool for predicting relative first metatarsal length. Here, we report a simple method to predict postoperative relative first metatarsal length after proximal rotational closing-wedge osteotomy for rheumatoid forefoot deformities. Two board-certified orthopedic surgeons performed relative first metatarsal length prediction retrospectively on a computed radiography system in nine consecutive cases. Most of them underwent simultaneous modified shortening oblique osteotomy of the second metatarsal (7/9 cases). The interclass correlation coefficients of intraobserver and interobserver reliability for relative first metatarsal length prediction were 0.96 and 0.94, respectively. The mean absolute error on relative first metatarsal length prediction was 1.5 mm at 3-month postoperatively in the same case series. The average time required to perform the relative first metatarsal length prediction was 44.1 s (standard deviation 9.0). Predicting relative first metatarsal length preoperatively in a simple manner, which takes less than a minute to complete, has the potential to improve the surgical outcome of rheumatoid forefoot surgery.

Keywords

• Forefoot deformities
• Forefoot joint-preserving arthroplasty
• Osteotomy
• Preoperative planning
• Rheumatoid arthritis