Background: We previously reported an increase in pronation of the first metatarsal (M1) head relative to the ground in hallux valgus (HV) patients compared to controls. Still, the origin and location of this hyperpronation along the medial column is unknown. Recent studies showed that presence of progressive collapsing foot deformities (PCFDs), which is a condition frequently associated with HV, can strongly influence the medial column coronal plane alignment. The objective of this study was to assess the coronal rotation of the medial column bones in HV feet, HV feet with radiologic markers of PCFD, and controls. We hypothesized that hyperpronation in HV will originate from a combination of M1 intrinsic torsion and first tarsometatarsal joint malposition. Methods: The same cohort of 36 HV and 20 controls matched on age, gender, and body mass index was used. Previously, a validation of the measurements was carried out through a cadaveric study. Using these metrics, we assessed the coronal plane rotation of the navicular, medial cuneiform, and the M1 at its base and head with respect to the ground using weightbearing CT images. We measured the Meary angle and the calcaneal moment arm in our 36 HV subjects. We subdivided our cohort into an HV group and a potential PCFD HV group according to these measurements. Comparisons on medial column bones coronal rotation were performed between HV, PCFD HV, and control groups. Results: Twenty-two HV cases were included in the HV group and 14 in the PCFD HV group. Both groups presented an increase in pronation of the first metatarsal head relative to the ground when compared to the control group ( P < .001). Comparing HV and controls showed an 8.3 degrees increase in pronation of M1 intrinsic torsion ( P < .001) and a 4.7 degrees pronated malposition of the first tarsometatarsal joint ( P = .02) in HV. A 9.7 degrees supinated malposition of the first naviculocuneiform joint ( P < .001) was also observed in HV. Comparing PCFD HV and controls showed a significant increase in pronation of the navicular (respectively, 17.2 ± 5.4 and 12.3 ± 3.4 degrees, P = .007) and a 5.5 degrees increase in pronation of M1 intrinsic torsion ( P = .02) in PCFD HV, without malposition of the first tarsometatarsal and naviculocuneiform joints. Conclusion: Hyperpronation of the M1 head relative to the ground originated from both increases in pronation of M1 intrinsic torsion and first tarsometatarsal joint malposition in HV, although partially counterbalanced by a supinated malposition of the first naviculocuneiform joint. On the other hand, PCFD HV patients showed a generalized pronated position throughout the medial column from the navicular to the M1 head and may be related to the midfoot and hindfoot deformities frequently present in PCFD. Level of Evidence: Level III, retrospective comparative study.

Objective: To assess interobserver reliability of previously described coronal plane rotation measurements of medial column bones and to assess their ability to accurately quantify changes in rotational profile. Methods: Two cadaveric below-knee specimens were implanted with pins in each bone of the medial column. Weight-bearing computed tomography (CT) scans were acquired in a simulated standing position under neutral, supinated, and pronated conditions. For each specimen and condition, 2 observers measured the coronal plane rotation of the navicular, medial cuneiform, first metatarsal base, shaft, and head, and proximal phalanx of the hallux as previously described. The rotation of each pin was measured relative to the ground in the coronal plane for each condition. These measurements were defined as benchmarks for the rotational profile of each bone. The correlation between these benchmarks and direct bone measurements was then assessed. Intraclass correlation coeficiente was used to assess interobserver reliability. Pearson’s coefficient was used to evaluate correlations. Results: The interobserver reliability of direct bone measurements ranged from 0.98 to 0.99. Correlations between pin rotation and direct measurements ranged from ρ=0.87 to 0.99 across the neutral, supinated, and pronated conditions. Conclusion: Coronal plane rotation measurements of medial column bones described in this study are reliable tools. Level of Evidence III; Case-Control Study.

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Little is known about the intersesamoid crista in Hallux Valgus (HV). However, this structure directly interfaces with the sesamoids and surrounding soft tissues and might play an important role in HV deformity. Our primary objective was to compare the angulation between the crista and first metatarsal (M1) longitudinal axis in HV and controls. Our secondary objective was to assess its correlation with the Distal Metatarsal Articular Angle (DMAA). We hypothesized that the longitudinal axis of the crista will be deviated in valgus in HV and that its position will be correlated with the DMAA. Methods: This IRB approved retrospective case control study evaluated 9 HV and 8 controls matched on age, BMI, and gender. The DMAA was measured as initially described on X-Rays, and then on weight-bearing CT images using a previously validated technique including pronation correction of the M1 called 3d-DMAA. To identify the angle of the inter-sesamoid crista relative to the shaft of the 1st metatarsal, CT scans were semi-automatically segmented to create 3D models of the forefoot. The crista was selected in Geomagic Design X and the resulting STL models were imported into MATLAB for analysis. Principal component analysis was used to identify the direction of both the crista and the 1st metatarsal shaft. The crista-shaft angle is the angle between the directions of greatest variation. Normality was assessed using Shapiro-Wilk tests. Comparisons were made using Student T-tests for normal variables and Mann-Whitney for non-normals. Correlations were assessed using Pearson's coefficients. Results: The crista deviated from the 1st metatarsal shaft in valgus in all the cases (HV and controls). There was a significant increase in valgus deviation of the crista in HV compared to controls (respectively 14.4+/-8.7 degrees and 5.5+/-3.2 degrees; p=0.017). Mean DMAA were respectively 25.1+/-7.9 degrees in HV and 7.4+/-2.9 in controls (p<0.001). Mean 3d-DMAA were respectively 12.5+/-5.6 degrees in HV and 3.1+/-2.4 in controls (p<0.001). There was a low positive non-significant correlation between the crista deviation and the DMAA (ρ=0.44; r2=0.193; p=0.078). There was a moderate positive significant correlation between Crista M1 Angle and 3D-DMAA (ρ=0.57; r2=0.326; p=0.017). Conclusion: The longitudinal axis of the inter-sesamoid crista deviates from the 1st metatarsal shaft in valgus in HV compared to controls. This follows the pattern of the 3d-DMAA which reflect the valgus deviation of the articular surface after exclusion of the pronation which is an important confounding factor of the original DMAA. The inter-sesamoid crista may play a role in HV pathophysiology as a possible lateral destabilizer of the surrounding soft tissues in HV. Surgically correcting the DMAA with a distal osteotomy might also correct the crista position in HV.