The Positive Association Between Metatarsal Length and Meary’s Angle and Hammertoe Deformity

Abstract

Category: Lesser Toes; Midfoot/Forefoot Introduction/Purpose: Hammertoe deformities are the most common pathology of the forefoot, accounting for up to 48% of all forefoot operations. There is currently limited evidence documenting differences in foot radiographs and radiographic measurements that may represent a predisposition to developing hammertoe deformity. The purpose of this study was to investigate whether patients with hammertoe deformity demonstrate increased radiographic measurements of first, second, or third metatarsal (MT) lengths as well as Meary’s angle compared to a healthy control group. Methods: Following IRB approval, an institutional radiology database was queried from January 2009-2018 for patients with ICD- 9 and ICD-10 diagnosis codes for hammertoe deformity of the 2nd or 3rd phalange. Control cases were selected using diagnosis codes for acute plantar fascial pain in the same timeframe with medical record review to exclude patients with prior lower extremity injury, surgery or pathology. 234 hammertoe and 110 control patients met inclusion and exclusion criteria. Automated 1:1 case-control matching was performed to control for age, sex and laterality. Following matching, the sample size consisted of 80 patients in each cohort. Proximal to distal end-to-end articular surface radiographic lengths were documented for metatarsals and phalanges of the 1st, 2nd and 3rd rays on anteroposterior radiographs. Lateral talar-first metatarsal (Meary’s) angle was measured using weightbearing sagittal radiographs by calculating the angle formed by lines that bisect the talar neck and anatomic neck of the first metatarsal. Results: A total of 160 patients (80 cases and 80 controls) were included in the study. Mean age was 47.7 years among hammertoe cases and 47.5 years among controls (p=0.92). 54 of 80 cases in each group were female. There was a statistically significant increase in the average Meary’s angle among hammertoe patients (5.23 +- 8.60°) compared to controls (2.15 +- 5.96°) (p<0.01). The average length for the 1st, 2nd and 3rd metatarsals were 65.6, 80.0, and 76.7 mm, respectively for the hammertoe patients and 62.8 mm, 76.0 mm, and 73.5 mm among control cases, respectively. For all three metatarsals, this difference was statistically significant (p<0.01; Table 1). There was no statistically significant difference between lengths of the proximal or distal phalanges. Conclusion: Patients with hammertoe deformity were associated with an increased length on the 1st, 2nd and 3rd metatarsals. Also, these patients demonstrated an increased Meary’s angle creating pes planus deformity. These results illustrate the importance of both medial column instability and long metatarsal length in the development of hammertoe deformity.