A Novel Manipulation Technique for Lapidus Fusion in Correction of Hallux Valgus Deformity With Underlying Metatarsus Adductus: A Case Series.

Underlying metatarsus adductus (MA) is commonly seen in patients with hallux valgus (HV) deformity, with implications regarding procedure selection and hallux valgus recurrence. Lapidus, or first tarsometatarsal fusion, is commonly performed allowing reduction in intermetatarsal angle (IMA) but this procedure has not been established as an approach to provide partial correction of MA deformity. Retrospective assessment of preoperative and postoperative metatarsus adductus angle (MAA), IMA and hallux abductus angle (HAA) in patients treated with Lapidus fusion for HV. Significance was determined via paired t test with a p value of <.05. All cases involved manual transverse plane manipulation to reduce both IMA and MAA during screw insertion. Intermetatarsal angle and Engel's angle were measured on preoperative AP radiographs to determine the presence of underlying MA in patients undergoing Lapidus fusion for HV. Ten weeks and 1 year postoperative radiographs were measured to determine degree of correction of IMA, HAA, and MAA. Thirty-four patients met inclusion criteria, which is approximately 46% of our sample population. The average preoperative IMA was 19.4˚ (range 12-32) and the average postoperative IMA was 9.7˚ (range 6-14). The average preoperative Engel's angle was 27.4˚ (range 24-34) and the average postoperative Engel's angle was 22.6˚ (range 15-28) with mean improvement in MA of 6.6˚. Of the 34, 27 (79.4%) patients had a normal Engel's angle at 10 weeks postoperatively. All measures of change met level of significance (p < .05). Of the 34 patients, 21 had radiographs taken beyond the 1 year mark (average 53 weeks). These patients were found to have an average Engel's angle of 23.0˚, which is not statistically significantly different from their 10 week measurements. Of the 21 patients, 17 (81%) maintained normal Engel's angle past 1 year. Metatarsus adductus varies regarding degree of reducibility and complicates preoperative angular measurement and correction of HV. Based on these findings, we recommend Lapidus fusion using this specified manipulation technique to obtain comprehensive transverse plane correction.