Metatarsal Pronation: Does It Matter?

CATEGORY: Bunion INTRODUCTION/PURPOSE: Hallux Valgus is a complex deformity with several attendant components that are present to varying degrees in each patient. Historically primary attention has been paid to correction of the coronal plane deformity, but recent investigations suggest a substantial contribution to the deformity from the axial rotational abnormality of the metatarsal. While the effect of this metatarsal pronation has been demonstrated, the relative contribution of this parameter compared to other components has not been considered. This study aims to investigate the rotational aspect of the deformity and its contribution to successful radiographic correction of the deformity. METHODS: A retrospective review of 100 consecutive Lapidus bunionectomy procedures was performed. There were 80 of patients and 89 feet. patients <18yrs, revision surgery and combined surgery, other than forefoot procedures were excluded. There were 79 (88%) females and 10 (12) males. The mean age was55. All feet were followed till radiographic healing was complete. Each foot was examined radiographically and pre and post-operative findings were compared. Along with the typical measurements of Hallux valgus parameters in the coronal plane, an additional measurement was included to estimate metatarsal head pronation (MT head shape and sesamoid position). The radiographic outcomes were then compared to determine the independent effect of metartarsal rotation on outcomes (recurrence, time to fusion). Pearson correlation was utilized to determine significant associations with the outcome parameters for recurrence, time to fusion, and failure to correct the hallux valgus angle (HVA). RESULTS: The average HVA correction was 20.08 degrees and 6.86 degrees for IMA. A total of 68 feet had a positive preop round head sign and correction to a normal MT head shape was observed in 47 feet. A significant increase in recurrence was associated with patients that had persistent MT round sign following correction (p=0.001) and in patients with a higher sesamoid position in the preop period p<0.001). The average time to fusion was 9.56 with 47 (52%) feet were healed at 6 weeks postop. A higher (more lateral) sesamoid position and a higher postop HVA were also associated with longer time to fusion or delayed union. CONCLUSION: Adequate preoperative radiographic assessment is of the utmost importance to assess the various forces that can contribute to hallux valgus deformity. Newer techniques address coronal and sagittal plane deformity. Failure to correct MT head pronation may lead to increased hallux valgus recurrence, despite sagittal correction measured by improvement of the HVA and IMA angles. Factors that impact time to fusion are also associated with a higher risk of HV recurrence. Sesamoid position and metatarsal head pronation should be considered, and correction of these parameters may be necessary to avoid delayed healing and persistent or recurrent HV.