Should We Use Intermetatarsal Angle as Primary Determinant to Define the Limits of Distal Chevron Osteotomy?

Abstract

Classic treatment algorithms limit the use of distal chevron osteotomy (DCO) to cases with an intermetatarsal angle (IMA) <14°. As the IMA increases, it is accepted that the contact between the metatarsal head and shaft will be insufficient. We have investigated the reliability of IMA to predict contact area percentage after DCO. Preoperative radiographs of patients with hallux valgus were subdivided as mild, moderate, and severe using traditional algorithms. After excluding the mild cases, we randomly selected 100 patients (50 moderate and 50 severe) and calculated the estimated bony contact (EBC) with our method and investigated the percentage of patients who could have >50% contact area if we perform a DCO. Thirty of 50 (60%) and 17 of 50 (34%) patients had >50% EBC in moderate and severe groups, respectively. We performed DCO for 24 patients (14 moderate and 10 severe cases). The 100-point American Orthopaedic Foot and Ankle Society (AOFAS) hallux-metatarso-phalangeal-interphalangeal scale was used to assess the clinical outcome. For the moderate group, we calculated mean IMA 16° (standard deviation [SD] ± 1.4°) and mean EBC 66.9% (SD ± 10.8%). For the severe group, we calculated mean IMA 20.9° (SD ± 0.7°) and mean EBC 63.1% (SD ± 10.4%). Paired t tests showed significant improvement comparing preoperative and postoperative AOFAS scores, IMA, hallux valgus angle, and sesamoid position for all operated patients (p < .001). We did not see any recurrence of hallux valgus or hallux varus and had only 1 minor complication that we managed conservatively. IMA may not always be a reliable parameter to predict the stability of DCO. Because the stability depends on the contact surfaces of osteotomy fragments, metatarsal head diameter and remaining bone contact should be the primary concerns. Two patients with the same IMA can have a different contact surface varying on a broad spectrum.