Abstract
Category:
Bunion; Hindfoot; Midfoot/Forefoot
Introduction/Purpose:
The presence of hyperpronation of the first metatarsal (M1) seems to have a clinically significant role in Hallux Valgus (HV). Some authors reported a decrease in recurrence rates after M1 hyperpronation correction in HV. However, when measuring the M1 head pronation relative to the ground, we are assessing and quantifying the aggregate coronal rotational profile of each bone and joint throughout the medial column. Therefore, we do not know the location of this hyperpronation. Moreover, studies showed a strong influence of the hindfoot alignment on coronal rotational measurements and Progressive Collapsing Foot Deformity (PCFD) is a condition frequently associated with HV. Our study aimed to assess and compare coronal plane alignment of medial column bones in HV, PCFD, PCFD HV and controls.
Methods:
We performed a retrospective IRB approved study. We collected 33 feet who consulted our center with combinations of symptomatic PCFD and HV. We then matched 33 HV, 33 PCFD, and 33 controls for BMI, Gender, and Age to this group. We assessed the coronal plane rotation of the navicular, medial cuneiform, M1 at its base and head, the Sesamoid Rotation Angle (SRA) with respect to the ground, and the hallux valgus angle (HVA) using Weight-Bearing CT images (Figure).The positions of the different joints (first naviculocuneiform (NC1), first tarsometatarsal (TMT1) and metatarsosesamoid rotation angle (MSRA)) were found by subtracting the adjacent angles. Intrinsic torsion of M1 was calculated by subtracting the M1 base angle from the M1 head angle.Normality of different variables was assessed using the Shapiro-Wilk test. Groups were compared using t test or ANOVA for normal and Mann Whitney or Kruskal Wallis for nonnormal variables.
Results:
HV, PCFD and PCFD HV presented higher M1 intrinsic torsion when compared to controls (respectively 7.3°[CI95%:2.9-11.7], p<0.001; 7.5°[CI95%:2.5-12.6], p<0.001; 7.5°[CI95%: 2.9-12],p<0.001).The navicular was more pronated in PCFD HV compared to controls (respectively 20+/-5.2° vs 12.5+/-3.9°,p<0.001) whereas it was not for PCFD and HV.NC1 was 6.8° significantly more supinated in HV (p<0.001) and 5.7° in PCFD HV (p<0.001) compared to controls whereas there was no significant difference between PCFD HV and Controls.TMT1 was 7.3° significantly more pronated in HV (p<0.001) and 4.9° in PCFD HV (p<0.001) compared to controls whereas there was no significant difference between PCFD HV and Controls. MSRA was significantly higher in HV (p<0.001) and PCFD HV (p<0.001) compared to controls whereas there was no significant difference between PCFD and Controls. In multivariate analysis, MSRA (β=0.95,[0.83;1.07], p <0.0001) were associated with higher values of HVA whereas NC1 (β=-0.24,[-0.42;-0.06], p= 0.0076) were associated with lower values of HVA.
Conclusion:
The intrinsic increase in M1 pronation appears to be a shared developmental abnormality in PCFD and HV. Combination of PCFD and HV seems to originate from the presence of a paradoxical supinatory malposition of the NC1 which was not present in PCFD without HV in our study. The presence of this compensatory supination malposition might explain the presence of HV by causing a metatarsosesamoid dislocation in HV and PCFD HV. In contrast, hyperpronation compensation in PCFD without HV might be proximal to the navicular because there was no difference between PCFD and control regarding the navicular position in our study.
