Clarification of the anatomic definition of the bunion deformity

The position, orientation and morphology of the peroneus longus tubercle in hallux valgus - A weight-bearing CT assessment

BACKGROUND

Hallux valgus (HV) may be associated with a dysfunctional peroneus longus, however there is very little research into the link between these pathologies. The peroneus longus tubercle (PLT) may serve as a surrogate marker for peroneus longus function. Our objective was to compare the position, orientation and morphology of the PLT in feet with and without HV.

METHODS

In this single center series, we analyzed weight-bearing CT scans of 20 feet (12 patients) with HV and 20 feet (12 patients) without HV. Groups were age matched. We compared differences between groups for recently reported measurements assessing the PLT: tubercle-to-floor distance (T-F distance), bisecting angle of the PLT, tubercle-to-metatarsals angle (T-MT angle), and cross-sectional areas and roundness of the PLT.

RESULTS

The T-F distance was significantly lower in the HV group (p = 0.001). The bisecting angle was lower (less vertical) in the HV group (p = 0.017). T-MT angle was lower in the HV group (p = 0.041). There was no difference in the cross-sectional area or roundness of the PLT between groups.

CONCLUSION

We found patients with HV had differences in orientation of the PLT (with a less vertical tubercle). This could indicate a relationship between direction of pull of the peroneus longus and HV. There were no differences in size of the PLT suggesting strength of the peroneus longus may not play a role in developing HV. Further research is needed to build upon this preliminary work and determine the link between the observed differences and the pathogenesis of HV.

Midfoot width changes after first metatarsal osteotomy in hallux valgus surgery: A biomechanical effect?

Hallux valgus is a challenging pathology characterized by a valgus deformity in the metatarsophalangeal area of the first ray. The aim of this study was to analyze the influence of first metatarsal osteotomy on the relationship between midfoot bones in patients with hallux valgus. The sample consisted of patients from the orthopedics and traumatology outpatient clinic who underwent surgical treatment for hallux valgus. Preoperative and postoperative X-rays were compared regarding the width of the midfoot and the tarsometatarsal joint. The sample consisted of 17 women, with 22 feet assessed in each group. The distance from the medial cuneiform to the cuboid, the distance from the intermediate cuneiform to the cuboid, the distance between the first and fifth metatarsals, and the distance between the second and fifth metatarsals reduced significantly between pre- and postoperative assessments. Hallux valgus correction through osteotomy of the first metatarsal leads to a structural change in the midfoot. Further studies should determine whether these changes persist over time.

Multiple factors contributing to the metatarsal head eversion in hallux valgus deformity. A prospective study using weight-bearing CT

PURPOSE

Recently first tarsometatarsal arthrodesis for hallux abducto valgus (HAV) has been advocated as the sole procedure to correct the multiplanar components of the deformity. However, recent debate suggests other factors such as rearfoot pronation and metatarsal torsion affect frontal plane metatarsal eversion and sesamoid positioning. Using weight-bearing CT, 12 feet (12 subjects) with HAV deformities were placed in positions of maximum rearfoot pronation and supination in order to study the effects on metatarsal eversion, sesamoid rotation/displacement, and secondarily the influence of first metatarsal torsion. Sesamoid displacement was quantified by the novel use of the sesamoid displacement angle.

PRINCIPLE RESULTS

Although first metatarsal eversion was nearly double in the pronated versus supinated foot, the difference was not statistically significant. Therefore, the bulk of first metatarsal eversion was not secondary to rearfoot eversion. Conversely, a significant positive correlation was found between metatarsal torsion and metatarsal head eversion angles in both supinated and pronated foot positions, with the strongest correlation with rearfoot pronation. Finally, significant increases in sesamoid displacement angles were noted with pronation.

MAJOR CONCLUSIONS

The findings of the present study support the contention that multiple factors are associated with frontal plane first metatarsal eversion and sesamoid displacement. Weight-bearing CT scanning can be used to effectively evaluate the frontal plane components in HAV deformities. The sesamoid displacement angle appears to be a useful adjunct to evaluating the hallucal sesamoids. For surgical correction of the deformity, consideration should be given to pre-operative weight-bearing CT evaluation of the foot. This can illuminate the effects of rearfoot/medial column pronation and the potential influence of metatarsal torsion on the frontal plane components of this triplane deformity. In this way the potential for post-operative HAV recurrence can be minimized.

The distal metatarsal articular angle in hallux valgus deformities. Comparisons of radiographic and weightbearing CT scan measurements with variations in hindfoot position

BACKGROUND

When evaluating hallux valgus (HV) deformity with anteroposterior (AP) foot radiographs, the distal metatarsal articular angle (DMAA) has been the subject of frequent debate. Although a straightforward indicator of structural alignment of the distal first metatarsal articular surface, inter- and intraobserver measurements can vary widely. Alterations in the radiographic appearance of bony "structure" with positional changes of the foot/foot bones in HV deformities in no small part contributes to these inaccuracies. The aim of this study was to determine the effect of hindfoot position on the DMAA.

METHODS

Four different radiologic images were obtained for 15 subjects with HV: three AP foot radiographs (standard weightbearing, foot supinated, foot pronated) and one weightbearing CT (WBCT) scan. For each image, five investigators measured the DMAA in order to assess reliability.

RESULTS

Mean DMAA values measured from the images indicated that the angle was highest with the pronated foot (15.3 (95% CI, 10.3-20.3) degrees) and lowest when measured from the CT image (11.6 (95% CI, 7.3-16.0) degrees). For all image types, the intraclass correlation coefficient was greater than 0.9 and statistically significant (P < 0.0005).

CONCLUSION

Hindfoot positions affected radiographic DMAA/mean DMAA values, with values highest with feet in pronated attitudes. Unlike radiographic projections, the WBCT appears less likely to overestimate DMAA and is not subject to variations in foot positioning. In the preoperative evaluation of HV deformities, this points to the potential use of WBCT as a reference standard. For markedly severe HV deformities that may present with AP radiographs with marked first metatarsal head "roundness," the use of WBCT is the intuitive choice. The results indicate excellent reliability in measurements of DMAA between all five investigators. As such, the measurement method used to determine DMAA in this study was dependable and reproducible.

LEVEL OF EVIDENCE

Level II.

One- and Two-Year Analysis of a Five-Year Prospective Multicenter Study Assessing Radiographic and Patient-Reported Outcomes Following Triplanar First Tarsometatarsal Arthrodesis With Early Weightbearing for Symptomatic Hallux Valgus

We report one- and 2-year results of a prospective, 5-year, multicenter study of radiographic, clinical, and patient-reported outcomes following triplanar first tarsometatarsal arthrodesis with early weightbearing. One-hundred and seventeen patients were included with a mean (95% confidence interval [CI]) follow-up time of 16.6 (15.5, 17.7) months. Mean (95% CI) time to weightbearing in a boot walker was 7.8 (6.6, 9.1) days, mean time to return to athletic shoes was 45.0 (43.5, 46.6) days, and mean time to return to unrestricted activity was 121.0 (114.5, 127.5) days. There was a significant improvement in radiographic measures with a mean corrective change of -18.0° (-19.6, -16.4) for hallux valgus angle, -8.3° (-8.9, -7.8) for intermetatarsal angle and -2.9 (-3.2, -2.7) for tibial sesamoid position at 12 months (n = 108). Additionally, there was a significant improvement in patient-reported outcomes (Visual Analog Scale, Manchester-Oxford Foot Questionnaire, and Patient-Reported Outcomes Measurement Information System) and changes were maintained at 12 and 24 months postoperatively. There was 1/117 (0.9%) reported recurrence of hallux valgus at 12 months. There were 16/117 (13.7%) subjects who experienced clinical complications of which 10/117 (8.5%) were related to hardware. Of the 7/117 (6.0%) who underwent reoperation, only 1/117 (0.9%) underwent surgery for a nonunion. The results of the interim report of this prospective, multicenter study demonstrate favorable clinical and radiographic improvement of the HV deformity, early return to weightbearing, low recurrence, and low rate of complications.

Repeatability of Weightbearing Computed Tomography Measurement of First Metatarsal Alignment and Rotation

BACKGROUND

Weightbearing computed tomography (WBCT) can be used to assess alignment and rotation of the first metatarsal. It is unknown whether these measures remain consistent on sequential WBCTs in the same patient when a patient's standing position may be different. The aim of this study was to establish the repeatability (test-retest) of measurements of first metatarsal alignment and rotation in patients without forefoot pathology on WBCT.

METHODS

We retrospectively identified 42 feet in 26 patients with sequential WBCT studies less than 12 months apart. Patients with surgery between scans, previous forefoot surgery or hallux rigidus were excluded. Hallux valgus angle (HVA) and intermetatarsal angle (IMA) were measured using digitally reconstructed radiographs. Two methods of calculating metatarsal rotation (metatarsal pronation angle [MPA] and alpha angle) were measured on standardized coronal CT slices. Interobserver agreement and test-retest repeatability were assessed using intraclass correlation coefficients (ICCs). Standard error of measurement (SEM) and minimally detectable change (MDC95) were calculated.

RESULTS

Interobserver agreement was excellent for HVA and IMA (ICC 0.96 and 0.90, respectively) and was good for MPA and alpha angle (ICC 0.81 and 0.80, respectively). There was excellent test-retest repeatability for HVA (ICC=0.90) and good test-retest repeatability for IMA (ICC=0.77). There was excellent test-retest repeatability for MPA (ICC=0.91) and good test-retest repeatability for alpha angle (ICC=0.87). The MDC95 was 4.6 degrees for MPA and 6.1 degrees for alpha angle. Five percent of patients had a difference outside of the MDC95 for the alpha angle, compared with 2% for the MPA.

CONCLUSION

Measurements of first metatarsal alignment and rotation are reliable between assessors and repeatable between sequential WBCTs in patients without forefoot pathology. Subtle differences in patient positioning during image acquisition do not significantly affect measurements, supporting the validity of this method of assessment in longitudinal patient care.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Short Term Radiographic and Patient Outcomes of a Biplanar Plating System for Triplanar Hallux Valgus Correction

Hallux valgus is a complex deformity with a variety of techniques described for correction. A biplanar plating system for triplanar correction system has been developed to address both the translation and rotational component of the hallux valgus deformity and allow an accelerated weightbearing protocol. The purpose of this study was to determine the correction and complications using radiographic parameters and patient reported outcomes. We sought to determine prognostic factors for successful correction, including age, gender, and preoperative deformity. From the medical records, we collected preoperative data. Patient-reported outcomes were obtained using AOFAS Hallux Metatarsophalangeal-Interphalangeal score, FAAM, and SF-12 scores preoperatively and postoperatively. Imaging was reviewed at preoperative and postoperative visits to determine hallux valgus angle, intermetatarsal angle, and tibial sesamoid position. Fifty-seven procedures, in 55 patients, were performed. There were 7 complications and mean follow-up time was 45.7 weeks (+ 28.3 weeks). Age over 62.5 years were associated with an increased risk of complications (p = .018). Males had an increased rate of complications (71%) compared with females. Radiographic parameters were significantly improved from preoperative values at alltime points (p < .05). Only the AOFAS Hallux Metatarsophalangeal-Interphalangeal score was statistically significant at 3, 6 and 12 months. We sought to determine the effectiveness of biplanar plating and triplanar correction procedure with early weightbearing. Over a 12 month follow-up period, our results showed significant improvement in deformity and maintained correction. AOFAS Hallux Metatarsophalangeal-Interphalangeal scores significantly improved from the preoperative to the postoperative state. Our results show a nonunion rate of 5.2%, which is comparable to prior studies.

First Metatarsal Rotation in Hallux Valgus Deformity

Rotation of the first metatarsal (M1) as a potential etiological factor of hallux valgus (HV) deformity was described relatively early in the description of HV pathoanatomy. However, because biplanar radiographs have been the standard method for imaging HV, clinicians primarily developed measurement methods and corrective operations confined to 2 dimensions, medial-lateral and inferior-superior. Recently, as our understanding of HV pathoanatomy has further developed, aided in part by advanced imaging technology, M1 rotation about its axis ("axial rotation") and its implications for HV deformity and treatment has reemerged. The goal of this review is to summarize M1 rotation in HV from a historical perspective, to present the current understanding of its potential role in the etiology/pathogenesis of HV, and to summarize relevant imaging and operative considerations with respect to M1 rotation.Level of Evidence: Level III, systematic review.

Foot structural factors and ground reaction force in hallux valgus grades

BACKGROUND

Little attention has been paid to foot structural factors and ground reaction force in hallux valgus. Investigating the structural factors in detail and determining their biomechanical effects can help to better manage hallux valgus.

METHODS

In this case-control study, 120 females, 90 hallux valgus and 30 healthy, were recruited. Hallux valgus grades (mild, moderate, severe), first metatarsal mobility, foot pronation, hallux rotation, and pain were assessed by clinical tests. Ground reaction forces were measured in barefoot and shod conditions for both feet and analyzed using mixed within-between MANOVA. The association between structural factors and pain with force was analyzed using Spearman correlation coefficient.

RESULTS

The frequency of foot structural factors and pain severity were reported in hallux valgus grades. A significant difference was seen in the force values between groups (P<0.001). Bonferroni post hoc test indicated that the mean of the first peak for the severe group was significantly higher than the mild group (P=0.013) and the mean of second peak for the moderate group was higher than that of the healthy group (P=0.009). The force values were affected by wearing shoe (P<0.001) but not by foot side (P=0.086). There was a medium, positive correlation between the hallux rotation and force in the moderate group (r=0.39, P=0.03) and also between the pronation and force in the severe group (r=0.36, P=0.04).

CONCLUSION

Foot structural factors, pain, and force were different in each hallux valgus grads. Similar force in both feet, and increased force by wearing shoe were seen. The relationship between the pronation and hallux rotation with force revealed the importance of these factors from the biomechanical viewpoint.

Hallux Pronation in Hallux Valgus: Experimental and Radiographic Study

Toe pronation is a frequent sign in hallux valgus (HV), but it is difficult to assess and quantify. The aim of this study was to evaluate the relation between big toe pronation with both radiological and clinical findings and to determine if toe pronation is an influential factor in severity of HV. Six big toe donor proximal phalanges were used to create a radiographic calibrating system controlling their pronation at 0° to 60°. A linear regression model was used to predict proximal phalanx pronation in radiographs. Big toe pronation in HV was clinically evaluated with a prospective study using 132 patients from our surgical waiting list and a control group of 30 patients without HV. Patients standing barefoot on a rigid platform were used to obtain the nail-floor angle. We obtained the following angles: HV, intermetatarsal, interphalangeal, distal articular set angle, proximal articular set angle, first metatarsal pronation, proximal phalanx pronation, and sesamoid bones displacement. We obtained an equation to predict proximal phalanx pronation according to the proportion of the rotated phalanx (p < .001, r = 0.98), and used an intraclass reliability test to assess the intra-/interobserver reliability (p < .001, intraclass correlation [ICC] = 0.89/p < .001, ICC = 0.82). We found that the relation between HV severity and proximal phalanx pronation, nail-floor angle, and first metatarsal pronation was statistically significant (p < .0001, r = 0.64). Proximal phalanx pronation and nail-floor angle should be considered to classify the severity of HV. Using a mathematical formula, we can predict proximal phalanx pronation on radiographs. Clinical Level of Evidence.

Triplane Hallux Abducto Valgus Classification

One of the most common procedures performed in the foot and ankle is correction of hallux abducto valgus deformity or "bunion surgery." Most foot and ankle surgeons recognize the challenges associated with defining each patient's individual deformity and selecting the optimal procedure for the best long-term results. Using current 2-dimensional algorithms that focus on the severity of the transverse plane deformity, surgical outcomes have varied. In the past 10 years, high recurrence and complication rates for popular procedures have been reported. In the same period, the reported data have elucidated an evolving anatomic understanding of the bunion deformity, with an expansion to 3 dimensions, including the frontal/coronal plane. We present a new classification and approach for the evaluation and procedure selection for bunion surgery. We hope this conceptual treatise on hallux abducto valgus based on clinical consensus and current data will stimulate academic discussion and further research. This anatomic classification is based on the 3-dimensional anatomy of the first ray.

Triplanar Quantitative Radiographic Analysis of the First Metatarsal-Phalangeal Joint in the Hallux Abductovalgus Deformity

Although hallux abductovalgus (HAV) is widely considered to be a triplanar deformity involving the transverse, sagittal, and frontal planes, most of the published literature has focused on evaluating the deformity in only the transverse plane, and we are unaware of any investigation objectively evaluating the relationship among the 3 planes in the setting of HAV deformity. The objective of this investigation was to quantitatively evaluate radiographic measurement of the relationship between the transverse, sagittal, and frontal planes in the HAV deformity. Anteroposterior, lateral, and sesamoid axial radiographs from 42 consecutive feet were evaluated with measurement of the first intermetatarsal angle, hallux abductus angle, metatarsal sesamoid position, first metatarsal inclination angle, sesamoid rotation angle, and tibial sesamoid grade. Variables were graphically depicted against each other on frequency scatter plots with calculation of a regression line and Pearson's correlation coefficient. As transverse plane deformity increased, the frontal plane deformity also tended to increase and the first metatarsal inclination angle tended to decrease. And as frontal plane deformity increased, the first metatarsal inclination angle tended to decrease. To our knowledge, these are the first quantitative and objective data in support of a triplanar component to the HAV deformity, and we believe this reinforces the evaluation of this deformity with emphasis on all 3 planes.

Comparison of Tibial Sesamoid Position on Anteroposterior and Axial Radiographs Before and After Triplane Tarsal Metatarsal Joint Arthrodesis

We reviewed the radiographic results of a group of patients who had undergone triplane correctional tarsometatarsal arthrodesis for symptomatic hallux abducto valgus with metatarsus primus abducto valgus. Of the 21 feet included in the present review, 17 (81%) displayed radiographic findings of metatarsal pronation preoperatively based on axial sesamoid views and positive lateral round sign on anteroposterior radiographs. At a mean follow-up period of 5.2 ± 1.6 months, a significant improvement in the tibial sesamoid position (TSP) on both anteroposterior (AP) and axial radiographs was measured. A negative metatarsal round sign, indicating correction of coronal plane metatarsal rotation, was observed in 20 of the 21 feet (95.2%) on AP radiographic evaluation. All 21 patients (100%) had obtained resolution of sesamoid subluxation on the sesamoid axial view at the final follow-up examination. The sesamoid axial position was consistently normal when the round sign was absent, and the TSP was in the normal range of 1 to 3 on the AP radiograph. Sesamoid subluxation from the normal position with the tibial sesamoid on or lateral to the crista was noted in 4 feet (19%) preoperatively and 0 feet postoperatively. This confirmed that lateral round sign of the first metatarsal head and a high TSP noted on the AP radiograph are both related to metatarsal pronation and can be corrected concurrently with coronal plane varus rotation of the first metatarsal as a part of the procedure.

First Metatarsal Head and Medial Eminence Widths with and Without Hallux Valgus

BACKGROUND

Resection of the medial eminence in hallux valgus surgery is common. True hypertrophy of the medial eminence in hallux valgus is debated. No studies have compared metatarsal head width in patients with hallux valgus and control patients.

METHODS

We reviewed 43 radiographs with hallux valgus and 27 without hallux valgus. We measured medial eminence width, first metatarsal head width, and first metatarsal shaft width in patients with and without radiographic hallux valgus.

RESULTS

Medial eminence width was 1.12 mm larger in patients with hallux valgus (P < .0001). Metatarsal head width was 2.81 mm larger in patients with hallux valgus (P < .001). Metatarsal shaft width showed no significant difference (P = .63).

CONCLUSIONS

Metatarsal head width and medial eminence width are significantly larger on anteroposterior weightbearing radiographs in patients with hallux valgus. However, frontal plane rotation of the first metatarsal likely accounts for this difference.

Quantitative Analysis of the Degree of Frontal Rotation Required to Anatomically Align the First Metatarsal Phalangeal Joint During Modified Tarsal-Metatarsal Arthrodesis Without Capsular Balancing

The data from 35 consecutive patients with hallux valgus undergoing triplane arthrodesis at the first tarsal metatarsal joint were studied to determine the amount of first metatarsal frontal plane rotation (supination) needed to anatomically align the first metatarsal phalangeal joint on an anterior posterior radiograph without soft tissue balancing at the first metatarsal phalangeal joint. Radiographs were measured both pre- and postoperatively to assess the 1-2 intermetatarsal angle, hallux abductus angle, and tibial sesamoid position (TSP). The mean amount of varus (supination) rotation performed during correction was 22.1° ± 5.2° and the mean amount of intermetatarsal angle reduction achieved after completion of the procedure was 6.9° ± 3.0°. The TSP changed by a mean of 3.3° ± 1.2°. A series of univariate linear regression analyses was performed to analyze the relationship between the frontal plane rotation of the first metatarsal performed during the operation and the preoperative intermetatarsal angle, hallux abductus angle, and TSP. Greater preoperative TSP scores were associated with greater intraoperative varus (supination) rotation required for joint alignment. Direct observation of the alignment changes at the first metatarsal phalangeal joint after metatarsal rotation without distal procedures strengthened the notion that the frontal plane rotational position plays an important role in the bunion deformity.

Radiographic Relevance of the Distal Medial Cuneiform Angle in Hallux Valgus Assessment

The angle formed by the distal articular facet of the medial cuneiform has been evaluated and discussed by various investigators. However, no consistent method has been available to radiograph and measure this entity. The wide variability of the angle is not conducive to comparative analysis. Additionally, investigators have noted that the angles observed (obliquity) vary greatly because of changes in radiographic angle, foot position, rotation of the first ray, and declination of the first metatarsal. Recognizing that these variables exist, we propose a reproducible assessment using digital radiography and application of deformity of correction principles. Our results have indicated a mean distal medial cuneiform angle of 20.69° in normal feet, 23.51° with moderate hallux valgus, and 20.41° with severe hallux valgus deformity. The radiograph beam was kept at 15° from the coronal plane. An inverse relationship was found between the distal medial cuneiform angle and bunion severity. This was in contrast to our expected hypothesis. The overall angle of the first metatarsal-medial cuneiform did, however, correlate with the severity of the bunion deformity (p < .000). The obliquity values and intermetatarsal angles changed in direct relationship to the radiographic projection angle. This illustrates the importance of using standardized radiographic projection angles. We conclude that the 1-dimensional standard anteroposterior radiograph with assessment of the distal medial cuneiform angle cannot adequately demonstrate the pathologic features of hallux valgus. A better indicator appears to be the first metatarsal-medial cuneiform angle. This pathologic entity is a 3-dimensional one that incorporates the joint morphology of the first ray, triplane osseous positioning, and soft tissue imbalances. Perhaps, 3-dimensional computed tomography imaging will provide better insight into this entity.

Is our current paradigm for evaluation and management of the bunion deformity flawed? A discussion of procedure philosophy relative to anatomy

Of the >100 procedures that have been proposed to treat hallux valgus or the "bunion" deformity, most have focused on correction through metatarsal osteotomies at various levels combined with soft tissue balancing procedures at the first metatarsophalangeal joint. This paradigm of metatarsal osteotomy and soft tissue balancing has been so commonplace, any argument for a fundamental change to the approach becomes uncomfortable and seems unwarranted to most foot and ankle surgeons. However, the simple fact that so many procedures exist, with so many modifications of these procedures, can be interpreted as a failure of our basic paradigm of metatarsal osteotomy and soft tissue balancing. We have observed that failure to recognize frontal plane rotation of the first metatarsal and our willingness to ignore deformity correction principles and create osteotomies outside the center of rotation of angulation are factors that can result in inconsistent outcomes. Our current multiprocedural mindset drives the search for yet more procedures and modifications in an attempt to reduce the incidence of complications. We present an anatomic analysis of hallux abducto valgus and metatarsus primus adducto valgus and critically analyze some of the shortcomings of currently popular corrective procedures. We also review the available data regarding frontal plane rotation of the first metatarsal and propose a new paradigm that considers frontal plane rotation of the first metatarsal as a priority in choosing the most appropriate procedure for bunion correction.

Observed changes in radiographic measurements of the first ray after frontal and transverse plane rotation of the hallux: does the hallux drive the metatarsal in a bunion deformity?

It is well known that the pathologic positions of the hallux and the first metatarsal in a bunion deformity are multiplanar. It is not universally understood whether the pathologic changes in the hallux or first metatarsal drive the deformity. We have observed that frontal plane rotation of the hallux can result in concurrent positional changes proximally in the first metatarsal in hallux abducto valgus. In the present study, we observed the changes in common radiographic measurements used to evaluate a bunion deformity in 5 fresh frozen cadaveric limbs. We measured the tibial sesamoid position, 1-2 intermetatarsal angle, and first metatarsal cuneiform angle on anteroposterior radiographs after frontal and transverse plane manipulation of the hallux. When the hallux was moved into an abducted and valgus position, a statistically significant increase was found in the tibial sesamoid position (p = .016). However, we did not observe a significant increase in the intermetatarsal angle (p = .070) or medial cuneiform angle (p = .309). When the hallux was manipulated into an adducted and varus position, a statistically significant decrease in the intermetatarsal angle (p = .02) and a decrease in the tibial sesamoid position (p = .016) was seen, with no significant change in the medial cuneiform angle (p = .360). We also observed a consistent rounding of the lateral aspect of the first metatarsal head and an increase in the concavity of the lateral metatarsal shaft, with valgus rotation of the hallux. From these observations, it is possible that the hallux could drive the proximal changes in the first ray that lead to metatarsus primus adducto valgus deformity.