A simple foot pedal device in a horizontal bore imaging facility replicates weightbearing outcomes for Hallux Valgus patients

A Comparison of Imaging Outcomes From 2 Weightbearing CT Modalities

BACKGROUND

The use of weightbearing images to diagnose foot and ankle injuries continues to offer hope for improved insight into pathologies, but weightbearing CT imaging has been limited by availability. The ability to apply force to the lower limb in a horizontal bore CT system may offer an adaptation to currently available imaging systems that provides access to weightbearing images without the acquisition of additional expensive imaging space or equipment.

METHODS

In order to determine whether a horizontal CT system could produce the same results as a standing CT, 3 images of one foot from 10 subjects was obtained and standard measures were calculated. Each subject underwent a standing CT scan, a scan in a horizontal bore CT machine while the subject pressed against a pedal with spring resistance and a finally a scan with the foot placed on the pedal but without any pressure.

RESULTS

No statistically significant difference between the standing and pedal-based CTs resulted. Navicular height and Meary angle (axial) were statistically different from nonweightbearing for both standing and horizontal systems. The horizontal results were statistically different from nonweightbearing in IM angle, talocalcaneal angle, and talonavicular coverage. No differences from nonweightbearing were found for either system in talar tilt, talocrural angle, or the lateral Meary angle.

CONCLUSION

The results in this initial study of normal control subjects suggest that a pedal-based loading mechanism may adapt a horizontal-bore CT system for the acquisition of weightbearing images.

CLINICAL RELEVANCE

The ability to acquire a weightbearing CT from a horizontal bore CT machine can make these images more available.

The feasibility study of stress position device simulating standing weight-bearing applied in computed tomography examination

BACKGROUND

In order to simulate weight-bearing Computed Tomography (CT) examination, this study designed a simple stress position device. By analyzing the relevant data of stress position footprints and weight-bearing position footprints, the feasibility of the stress position device to simulate standing weight-bearing was verified.

METHODS

This study randomly selected 25 volunteers for standing weight-bearing and stress position footprints collection, and measured the relevant indicators of stress position footprints and standing weight-bearing position footprints. Two foot and ankle surgeons conducted two measurements respectively on the footprints. Intra-observer and inter-observer reliability were calculated using intra-class correlation coefficients (ICC). Pearson correlation coefficient, ICC, scatter plot analysis, and paired t-test were used to analyze the stress and weight-bearing position data.

RESULTS

The intra-observer and inter-observer measurement values were reliable. There was a certain degree of correlation between the stress position footprints and weight-bearing position footprints in terms of Pearson correlation coefficient, ICC, and scatter plot analysis. Paired t-tests showed significant differences in Clarke angle (t 2.636, p .012), C-S index (t 10.568, p .000), arch indx (t 2.176, p .035), and arch lower angle (t 6.246, p .000).

CONCLUSION

The stress position device can generate a certain degree of stress, and after further optimization and improvement of the stress position device, it is feasible to apply it to weight-bearing CT examination in clinical settings.

Pronation on weightbearing radiographs does not correlate with pronation from weightbearing CT scans

INTRODUCTION

In hallux valgus (HV), first metatarsal pronation is increasingly recognized as an important aspect of the deformity. The purpose of this study was to compare pronation in HV patients determined from the shape of the lateral head of the first metatarsal on AP weightbearing radiographs with pronation calculated from weightbearing CT (WBCT) scans.

METHODS

Patients were included in this study if they had preoperative and 5-month postoperative WBCT scans and corresponding weightbearing AP radiographs of the affected foot. Pronation of the first metatarsal on WBCT scans was measured using a 3D CAD model and the alpha angle and categorized into four groups on radiographs. Association between pronation groups on radiographs and WBCT scans was determined using Spearman correlation coefficients (r_s) and by comparing mean WBCT pronation of the first metatarsal between plain radiograph pronation groups.

RESULTS

Agreement between the two observers' pronation on radiographs was good (k = 0.634) and moderate (k = 0.501), respectively. There was no correlation between radiographic pronation and the 3D CAD model (r_s < 0.15). Preoperatively, there was weak correlation between the alpha angle and the radiographic pronation groups (r_s = 0.371, P = 0.048) although this relationship did not hold postoperatively (r_s = 0.330, P = 0.081). There was no difference in mean pronation calculated on WBCT scans between the plain radiographic groups.

CONCLUSION

Pronation of the first metatarsal measured on weightbearing AP radiographs had moderate interobserver agreement and was only weakly associated with pronation measured from WBCT scans. These results suggest that first metatarsal pronation measured on weightbearing radiographs is not a substitute for pronation measured on WBCT scans.

LEVEL OF EVIDENCE

III, retrospective cohort study.

The Association of Crista Volume With Sesamoid Position as Measured From 3D Reconstructions of Weightbearing CT Scans

BACKGROUND

Malposition of the sesamoids relative to the first metatarsal head may relate to intersesamoid crista underdevelopment or erosion. Using 3-dimensional models created from weightbearing CT (WBCT) scans, the current work examined crista volume and its relationship to first metatarsal pronation and sesamoid station.

METHODS

Thirty-eight hallux valgus (HV) patients and 10 normal subjects underwent weightbearing or simulated WBCT imaging. The crista was outlined by the inferior articular surface, and a line was drawn to connect the lowest point of each sulcus on either side of the intersesamoidal crista throughout the length of the crista. The volume was calculated. Sesamoid station and first metatarsal pronation were calculated from the 3D reconstructions. The mean crista volumes between HV and normal patients were statistically compared, as were the crista volume and pronation angle between sesamoid stations.

RESULTS

The mean crista volume in HV patients was 80.10 ± 35 mm³ and in normal subjects was 150.64 ± 24 mm³, which differed significantly between the 2 groups (P < .001). Mean crista volumes were found to be statistically significantly different between the sesamoid stations (P < .001) with decreasing crista volumes significantly and strongly correlated with increasing sesamoid station (r = -0.80, P < .001). There was no difference in the mean pronation angle between the 4 sesamoid stations (P = .37). The pronation angle was not associated with crista volume (P = .52).

CONCLUSION

HV patients have lower mean crista volume than normal patients. Crista volume is correlated with sesamoid station. Pronation of the first metatarsal was not associated with crista volume.

CLINICAL RELEVANCE

Crista volume may offer an additional determinant for the severity of hallux valgus.