Pilot Study of a 3-Dimensional Method for Analysis of Pronation of the First Metatarsal of Hallux Valgus Patients

Weight-Bearing Computed Tomography of the Foot and Ankle-What to Measure?

Weight-bearing computed tomography (WBCT) was introduced in 2012 for foot and ankle applications as a breakthrough technology that enables full weight-bearing, three-dimensional imaging unaffected by x-ray beam projections or foot orientation. The literature describing the use of WBCT in the treatment of foot and ankle disorders is growing, and this article provides an overview of what can be measured with WBCT.

Preoperative Degenerative Changes at the Tibial Sesamoid-Metatarsal Joint in Hallux Valgus: Association With Postoperative Patient-Reported Outcomes After Modified Lapidus Procedure

Background

Degenerative changes at the sesamoid-metatarsal joints (SMJs) may be a source of pain following hallux valgus surgery. The aims of this study were to describe degenerative changes at the SMJs on weightbearing computed tomography (WBCT) scans and, secondarily, investigate their association with 1-year patient-reported outcome scores following a modified Lapidus procedure for hallux valgus. We hypothesized that reduced joint space in the SMJs would correlate with worse patient-reported outcomes.

Methods

Fifty-seven hallux valgus patients who underwent a modified Lapidus procedure had preoperative and minimum 5-month postoperative WBCT scans, and preoperative and at least 1-year postoperative PROMIS physical function (PF), pain interference, and pain intensity scores were included. Degenerative changes at the SMJs were measured using distance mapping between the sesamoids and first metatarsal head on preoperative and postoperative WBCT scans. The minimum and average distances between the first metatarsal head and tibial sesamoid (tibial-SMJ) for each patient preoperatively and postoperatively were measured. Sesamoid station was measured on WBCT scans using a 0 to 3 grading system. Linear regression was used to investigate the correlations between minimum preoperative and postoperative tibial-SMJ distances and 1-year postoperative PROMIS scores.

Results

The median minimum and average tibial-SMJ distances increased from 0.82 mm (interquartile range [IQR] 0.40-1.03 mm) and 1.62 mm (IQR 1.37-1.75 mm) preoperative to 1.09 mm (IQR 0.96-1.23 mm) and 1.73 mm (IQR 1.60-1.91 mm) postoperative (P < .001 and P < .001), respectively. In a subset of patients with complete sesamoid reduction, we found an association between preoperative minimum tibial-SMJ distance and 1-year postoperative PROMIS PF scores (coefficient 7.2, P = .02).

Conclusion

Following the modified Lapidus procedure, there was a statistically significant increase in the tibial-SMJ distance. Additionally, in patients with reduced sesamoids postoperatively, reduced preoperative tibial-SMJ distance correlated with worse PROMIS PF scores.

Level of Evidence

Level IV, case series.

Hallux Valgus: The Influence of Intersesamoid Crista's Osteoarthritis on Frontal Plane Pronation

A frontal plane metatarsal rotational (pronation) has been documented in a high percentage of hallux valgus patients. Pathoanatomical concepts leading to pronation are still debated. Nevertheless, there is no consensus on how to measure this component of the deformity. The aim of the present study was to find potential associations between sesamoid's crista osteoarthritis and the frontal plane deformity in HV cases. Our study showed a moderate correlation between the crista's OA and the intermetatarsal angle (IMA), the hallux valgus angle (HVA) and the alpha angle. In severe hallux vulgus deformed specimens, with an eroded intersesamoid crista, frontal plane pronation was not as prevalent nor severe as in those without osteoarthritic degeneration. Severe hallux valgus cases with a completely eroded crista, showed lower pronation, and higher IMA, when compared to specimens with a preserved anatomy. This brings to light the intersesamoid crista's unique function in retaining the IMA. Understanding the role the frontal plane plays in hallux valgus' biomechanics and in its radiographic appearance is vital to change the current paradigm.

Validity and Reliability of a New Radiological Method to Estimate Medial Column Internal Rotation in Hallux Valgus Using Foot Weight-Bearing X-Ray

BACKGROUND

Medial column internal rotation in hallux valgus (HV) can be measured using weight-bearing computed tomography (WBCT). Anteroposterior weight-bearing foot radiographs' (WBXR) ability to estimate medial column internal rotation in HV was evaluated comparing these measurements with those obtained from WBCT.

METHODS

Three observers evaluated WBCT and WBXR of 33 HV feet twice. Medial column internal rotation was measured with WBCT and classified into 3 levels according to WBXR findings. Intra- and interobserver reliability were obtained for WBXR and WBCT, in addition to WBXR-WBCT correlation.

RESULTS

WBXR and WBCT intraobserver agreement was substantial and near perfect, respectively (κ 0.79 and 0.84). Their interobserver agreement was excellent (intraclass correlation 0.85 and 0.9, respectively). The WBXR-WBCT correlation was substantial (κ 0.68). WBXR diagnostic accuracy to predict the WBCT results was 85%.

CONCLUSIONS

The proposed method for medial column internal rotation measurement using WBXR is reliable and has a substantial agreement with WBCT measurements.

LEVELS OF EVIDENCE

Level III.

Evaluate the Influencing Factors of Congruency of the First Metatarsophalangeal Joint in Hallux Valgus Based on Weightbearing CT

The purpose of this study was to explore the difference between congruency and incongruency of the first metatarsophalangeal (MTP) joint in hallux valgus using weightbearing CT (WBCT) and to identify the risk factors for incongruency. From January 2019 to January 2021, WBCT scans were retrospectively analyzed for 110 (191 feet) consecutive patients. According to whether the metatarsal articular surface and phalanx articular surface were parallel, they were divided into congruency (73 feet) and incongruency groups (118 feet). The age, intermetatarsal angle (IMA), hallux valgus angle (HVA), distal metatarsal articular surface angle (DMAA), first metatarsal coronal pronation angle (α angle), tibial sesamoid 7 positions (TSP), and tibial sesamoid coronal grading (TSCG) were compared between the 2 groups. Binary logistic regression was used to analyze the influencing factors of incongruency. Receiver operating characteristic (ROC) curve analysis was applied to determine the cutoff value. There were significant differences in IMA, HVA, DMAA, α angle, age, TSP, and TSCG between congruency and incongruency groups (p < .05). Binary logistic regression analysis showed that TSCG, HVA, α angle were the influencing factors of incongruency. ROC curve analysis demonstrated that the cutoff values for incongruency were 1 position for TSCG (sensitivity: 0.835; specificity: 0.884) with the area under curve (AUC) of 0.892, 30° (sensitivity: 0.795; specificity: 0.812) for HVA with the AUC of 0.878, and 24° (sensitivity: 0.530; specificity: 0.797) for α angle with the AUC of 0.686. Incongruency of the first MTP joint indicated a more severe hallux valgus, and was associated with increased HVA, α angle, and TSCG.

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.

Weight-Bearing Computed Tomography of the Foot and Ankle-What to Measure?

Weight-bearing computed tomography (WBCT) was introduced in 2012 for foot and ankle applications as a breakthrough technology that enables full weight-bearing, three-dimensional imaging unaffected by x-ray beam projections or foot orientation. The literature describing the use of WBCT in the treatment of foot and ankle disorders is growing, and this article provides an overview of what can be measured with WBCT.

Three-dimensional morphological variations in the calcaneus and talus in relation to the hallux valgus angle

BACKGROUND

The present study aimed to clarify the morphological patterns of the calcaneus and talus that are associated with hallux valgus angle (HVA) by quantifying the differences in the hindfoot bone morphology between left and right sides in HV patients with clear bilateral difference of HVA.

METHODS

Three-dimensional (3D) computed tomography scans of 32 feet of 16 patients with HV who had right-to-left HVA differences of more than 5 degrees (68.8 ± 8.6 years) were enrolled, and 3D surface models of the calcaneus and talus were generated. A total of 556 and 430 landmarks were placed on the calcaneal and talar surfaces, respectively, to calculate the principal components (PCs) of shape variations. The PC scores were compared between the small and large HVA sides within an individual.

RESULTS

The calcaneus in patients with a larger HVA (mean, 43.2 degrees) possessed slender calcaneal tuberosity, more medially oriented posterior articular surface in the coronal plane, and narrower and more concave anterior-middle articular surfaces compared to those with a small HVA (mean, 33.7 degrees). The talus with a larger HVA exhibited more medially oriented talar head in the transverse plane and more anteriorly protruded lateral region of the talar head compared to the small HVA.

CONCLUSIONS

The morphological patterns of the calcaneus in patients with a larger HVA allows the hindfoot bones to easily rotate in the everting direction, while those of the talus could induce a larger internal rotation of the first metatarsal. These morphological patterns of the calcaneus and talus could be structural factors affecting the HV.

Intraoperative checking of the first ray rotation and sesamoid position through sonographic assistance

INTRODUCTION

Hallux valgus (HV) deformity affects the orientation of the metatarsophalangeal (MTP) joint in three planes. Displacement in the coronal plane results in axial rotation of the first metatarsal, with progressive subluxation of the first MTP joint. Multiple techniques have been described to correct the malrotation itself. However, none of them have checked intraoperatively the final position of the first metatarsal head and sesamoids previous to the fixation of the Lapidus procedure or first metatarsal bone osteotomies. The aim of this article is to describe a novel technique to check the first ray rotation and sesamoids position through sonographic assistance.

MATERIALS AND METHODS

Before fixation of the Lapidus procedure, with the ankle in maximal dorsiflexion, the surgeon takes the linear ultrasound probe and places it on the sole to visualize the sesamoids, which should be viewed at the same level, with the flexor hallucis longus (FHL) centered between both. Once the ideal position of the head of the first ray has been achieved, temporary fixation with K-wires is performed over the first TMT joint and M1-M2 joint for further sonographic verification of the sesamoids beneath the first metatarsal head. The height of the sesamoids relative to the second metatarsal head should be checked by sonographic control too.

RESULTS

Four patients were included. Three females and one male. Their mean age was 76.4 years (R 61-72). Their mean BMI was 29 (R 27.5-32.24). The mean IMA (intermetatarsal angle) was 18.2 (R 17.2-19) degrees and the mean MPA (metatarsophalangeal angle) was 50 (R 36-63) degrees.

CONCLUSIONS

Sonographic assistance, is a widely available, inexpensive, and comparative imaging technique that can guide the first ray rotation and sesamoids position in HV surgery, theoretically improving radiological outcomes.

Investigation on the site of coronal deformities in Hallux valgus

Hallux valgus (HV) is a common foot deformity that is more prevalent in females, characterised by abnormal adduction of the first metatarsal (MT) and valgus deviation of the phalanx on the transverse plane. Increasing evidence indicates that HV is more than a 2D deformity but a 3D one with rotational malalignment. Pronation deformity is seen during clinical examination for HV patients, but the exact origin of this rotational deformity is still unknown. Some attribute it to first tarsometatarsal (TMT) joint rotation, while others attribute it to intra-metatarsal bony torsion. In addition, the correlation between the rotational and transverse plane deformity is inconclusive. Identifying the origin of the rotational deformity will help surgeons choose the optimal surgical procedure while also enhancing our understanding of the pathophysiology of HV. This study aims to (1) develop an objective method for measuring the first MT torsion and first TMT joint rotation; (2) investigate the exact location of the coronal deformity in HV; (3) investigate the relationship between the severity of deformity on the transverse and coronal planes as well as the correlation between deformity severity and foot function/symptoms in HV. Age-matched females with and without HV were recruited at the Foot and Ankle Clinic of the Department of Orthopaedics and Traumatology. Computed tomography was conducted for all subjects with additional weight-bearing dorsal-plantar X-ray examination for HV subjects. Demographic information of all subjects was recorded, with symptoms and functions related to HV evaluated. The intra-class correlation was used to explore the relationship between deformities on different planes and the deformity severity and functional outcomes, respectively. An Independent t-test was used to compare joint rotation and bone torsion degrees. TMT joint rotation is significantly correlated with foot function. HV patients had more TMT joint rotation but not MT torsion compared to normal controls. No relationship was found between the coronal rotation and the 1,2-intermetatarsal angle (IMA) or Hallux valgus angle (HVA) on the transverse plane. Our results indicate that coronal deformities in HV may originate from TMT joint rotation. In addition, the severity of the TMT joint coronal rotation correlates with worse foot function; thus, multi-plane assessment and examination will be necessary for more precise surgical correction.

Proximal to distal phalangeal articular angle of the first proximal phalanx: Reliability and correlation with round sign

BACKGROUND

To reduce the rate of correction loss in hallux valgus surgery, a proximal to distal phalangeal articular angle (PDPAA) of the proximal phalanx of the greater toe of> 8° is considered an indication for a combined Akin and Chevron osteotomy. The PDPAA is measured between the articular surfaces of the proximal phalanx of the greater toe. Viewed from a sagittal perspective, the joint surfaces are not perpendicular aligned to the phalanx axis. Therefore, the PDPAA might be confounded by pronation. This study aims to, first, evaluate the intra- and interobserver reliability of the PDPAA and, second, to analyze the correlation to first ray pronation.

METHODS

In a consecutive series of 59 feet who underwent hallux valgus (HV) surgery, PDPAA, round sign and other angles were measured on weight-bearing radiographs pre- and postoperatively. After power analysis, the intraclass correlation coefficient (ICC) was used to calculate the intra- and interobserver reliability. The correlation of PDPAA with the round sign as well as angles defining the HV and the Hallux valgus interphalangeus (HVI) were evaluated.

RESULTS

The PDPAA showed an excellent intra- and interobserver reliability (ICC 0.92 and 0.89, p < 0.05). The round sign did not correlate significantly with the PDPAA (p = 0.51). However, the PDPAA showed a moderate correlation with the interphalangeal angle (r = 0.51, p < 0.05) and fair inversely with the intermetatarsal angle (r = -0.45, p < 0.05).

CONCLUSION

First, measurement of PDPAA is reliable. Second, PDPAA is not associated with first ray pronation, but a false low PDPAA is geometrically possible. A high PDPAA correlates with a relevant HVI and inversely correlates with the HV like the HVI. Hence, first ray pronation should be treated first and a remaining PDPAA of> 8° after intraoperatively reevaluation separately.

Radiological and Anatomical Evaluation of First Metatarsal Pronation in Hallux Valgus Deformity: A Comparison Between Three Different Methods

A frontal plane metatarsal rotational (pronation) has been documented in a high percentage of hallux valgus patients. Pathoanatomical concepts leading to pronation are still debated. Nevertheless, there is no consensus on how to measure this component of the deformity. The aim of the present study was to compare three commonly used radiographic methods to measure the frontal plane deformity in hallux valgus deformity, such as 1. Round sign of the lateral edge of the first metatarsal head on anterior-posterior radiograph, 2. Non-weightbearing CT-scan and 3. Bernard's axial projection of the first metatarsal head. Afterwards, feet were dissected, and a direct measurement of the pronation was done. Our data showed that alpha angle measurements made through the Bernard's axial projection were closer with those obtained during the dissection compared to those made through the CT-scan. The main finding of our study is that osteoarthritic changes at the metatarso-sesamoid joint play an important role in severe hallux valgus cases. The proposed radiographic methods allow surgeons to verify whether rotation can be corrected during Hallux Valgus procedures and to determine which procedure may be the best for each patient.

Reliability improvement in Hallux Valgus measurement using weight-Bearing CT scan

Background: Radiographic assessment of hallux valgus is an essential process. Residual rotational deformity was shown associated with higher recurrent rate. This study aims to comprehensively assess reliability of measurement of various parameters from plain films and weight-bearing CT scan. Methods: A total of 40 pre-operative plain radiographs, 40 post-operative plain radiographs, and 37 weight-bearing CT scan were evaluated to determine reliability of hallux valgus parameters. Results: TSP and head shape representing coronal plane deformity showed lower inter-observer reliability compared to other parameters using for transverse plane evaluation especially in post-operative period. (post-op TSP amongst 3 assessors: κ = 0.386, 0.520, 0.340; post-op head shape: κ = 0.374, 0.375, 0.295) Using α angle for evaluation 1^st metatarsal rotation in weight-bearing CT scan demonstrated very good reliability for inter-observer (ICC = 0.853 (95% CI = 0.715-0.925)) and intra-observer (ICC = 0.902 (95% CI = 0.844-0.939)). Conclusion: Weight-bearing CT scan can improve reliability in post-operative coronal plane assessment.

A Case-Control Study of 3D vs 2D Weightbearing CT Measurements of the M1-M2 Intermetatarsal Angle in Hallux Valgus

BACKGROUND

Weightbearing computed tomography (WBCT) 3-dimensional measurements may be reliable in assessing hallux valgus (HV). The objective of this study was to compare 2D and 3D WBCT measurements of the M1-M2 intermetatarsal angle (IMA) in patients with HV and in healthy controls. We hypothesized that 2D and 3D IMA measurements would correlate and have similar reliability in both HV and controls.

METHODS

Retrospective multicenter comparative study included WBCT scans from 83 feet (41 HV, 42 controls). IMA was measured on digitally reconstructed radiographs (DRR-IMA). 3D angle (3D-IMA) and its projection on the weightbearing plane (2D-IMA) were calculated from 3D coordinates of the first and second metatarsals. Intraobserver reliability and intermethod correlations were calculated using intraclass correlation coefficients (ICCs).

RESULTS

Intraobserver reliability was very strong for DRR-IMA (0.95) and 3D-IMA (0.99). Intermethod correlation between the 3 modalities in HV patients ranged from moderate (DRR vs 2D, 0.48; DRR vs 3D, 0.48) to very strong (2D vs 3D, 0.91). Similarly, intermethod correlation in the control group ranged from moderate (DRR vs 2D, 0.56; DRR vs 3D, 0.60) to very strong (2D vs 3D, 0.92).

CONCLUSION

Measurements for IMA are similar using DRR, 3D and 2D projected angles, with very strong intraobserver reliability and moderate to very strong intermethod correlations. This is the first head-to-head comparison between these measurement modalities in HV. Further investigations are warranted before formulating guidelines for the clinical use of 3D angles.

LEVEL OF EVIDENCE

Level III, case-control study.

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.

Clinical Outcomes and Rotational Correction of First Metatarso-Cuneiform Fusion With First Metatarsal to Second Cuneiform Fixation

Background:

The modified Lapidus procedure (first metatarso-cuneiform fusion) is a powerful technique for correcting triplanar deformity in hallux valgus. Although traditionally fixed with cross-screws (CS), growing awareness of intercuneiform stability and pronation deformity has led to fixation using a plate and first metatarsal–second cuneiform (1MT-2C) screw fixation (PS). We investigated Lapidus patient cohorts using CS vs PS fixation to understand patient-reported outcomes, angular and rotational correction, and complication rates.

Methods:

We retrospectively reviewed cases of modified Lapidus for hallux valgus by a single surgeon. Patients were divided into CS or PS groups according to fixation. All patients had preoperative Patient Reported Outcome Measurement Information System (PROMIS) scores and minimum 12 months of follow-up. PROMIS scores in 6 key domains were compared within and between groups. Radiographic assessment of hallux valgus angle and intermetatarsal angle were performed on pre- and postoperative XR. Pronation of the first ray was measured on pre- and postoperative weightbearing computed tomography.

Results:

We compared 42 patients with PS fixation to 43 with CS fixation. Both groups had significant improvement in hallux valgus angle and intermetatarsal angle (P < .001), with no difference between groups. PS patients experienced a greater correction of first metatarsal pronation, an average reduction of 11 degrees, compared to 8 degrees in the CS group (P < .039). Both cohorts experienced improvement in PROMIS physical function, pain interference, pain intensity, and global physical function. There were no differences in PROMIS score improvements between the cohorts. The CS group started weightbearing at 6 weeks vs 3.6 weeks for the PS group. Complication and revision rates were similar.

Conclusion:

A plate and 1MT-2C screw fixation provides safe, robust fixation of Lapidus procedure and prevents instability through the intercuneiform joint. We observed similar improvement in PROMIS compared with patients treated with cross-screws. Complications did not increase despite the PS group weightbearing much earlier. PS patients achieved greater first ray rotational correction.

Level of Evidence:

Level III, retrospective cohort study.

Imaging Findings and First Metatarsal Rotation in Hallux Valgus

BACKGROUND

Failure to identify and correct malrotation of the first metatarsal may lead to recurrent hallux valgus deformity. We aimed to identify the proportion of hallux valgus patients with increased first metatarsal pronation using weightbearing computed tomography (WBCT) and to identify the relationship with conventional radiographic measurements.

METHODS

WBCT scans were analyzed for 102 feet with a hallux valgus angle (HVA) and intermetatarsal angle (IMA) greater than or equal to 16 and 9 degrees, respectively. Metatarsal pronation angle (MPA), alpha angle, sesamoid rotation angle (SRA), and sesamoid position were measured on standardized coronal WBCT slices. Pronation was recorded as positive. Hindfoot alignment angle (HAA) was assessed using dedicated software. Pearson correlation and multiple regression analyses were used to assess differences between groups.

RESULTS

Mean HVA was 29.8±9.4 degrees and mean IMA was 14.1±3.7 degrees. Mean MPA was 11.9±5.8 (range 0-26) degrees and mean alpha angle was 11.9±6.8 (range -3 to 29) degrees. In a previous study, we demonstrated the upper limit of normal MPA as 16 degrees and alpha angle as 18 degrees. Based on these criteria, we identified abnormal metatarsal pronation in 32 feet (31.4%). We found a strong positive correlation between SRA and HVA/IMA (R = 0.67/0.60, respectively, P < .001). IMA and HAA weakly correlated with MPA and alpha angle (IMA: R = 0.26/0.27, respectively, P < .01; HAA: R = 0.26/0.27, respectively, P < .01). Regression analyses suggested that increasing IMA was the most significant radiographic predictor of increased pronation. In this cohort, there was no correlation between HVA or sesamoid position and MPA / alpha angle (HVA: P = .36/.12, respectively, sesamoid position, P = .86/.77, respectively).

CONCLUSION

In this cohort of 102 feet that met plain radiographic criteria for hallux valgus deformity, first metatarsal pronation was found abnormal in 31.4% of patients. We found a weak association between the IMA and hindfoot valgus, but not the HVA.

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.

Association of First Metatarsal Pronation Correction With Patient-Reported Outcomes and Recurrence Rates in Hallux Valgus

BACKGROUND

The purpose of this study was to determine if a postoperative decrease in first metatarsal pronation on 3-dimensional imaging was associated with changes in patient-reported outcomes as measured by the Patient-Reported Outcomes Measurement Information System (PROMIS) physical function, pain interference, and pain intensity domains or recurrence rates in patients with hallux valgus (HV) who undergo a first tarsometatarsal fusion (modified Lapidus procedure).

METHODS

Thirty-nine consecutive HV patients who met the inclusion criteria and underwent a modified Lapidus procedure had preoperative and ≥2-year postoperative PROMIS scores and had first metatarsal pronation measured on preoperative and at least 5-month postoperative weightbearing CT scans were included. Multivariable regression analyses were used to investigate differences in the change in PROMIS domains preoperatively and 2 years postoperatively between patients with "no change/increased first metatarsal pronation" and "decreased first metatarsal pronation." A log-binomial regression analysis was performed to identify if a decrease in first metatarsal pronation was associated with recurrence of the HV deformity.

RESULTS

The decreased first metatarsal pronation group had a significantly greater improvement in the PROMIS physical function scale by 7.2 points (P = .007) compared with the no change/increased first metatarsal pronation group. Recurrence rates were significantly lower in the decreased first metatarsal pronation group when compared to the no change/increased first metatarsal pronation group (risk ratio 0.25, P = .025).

CONCLUSION

Detailed review of this limited cohort of patients who underwent a modified Lapidus procedure suggests that the rotational component of the HV deformity may play an important role in outcomes and recurrence rates following the modified Lapidus procedure.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

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.

Assessing the Rotation of the First Metatarsal on Computed Tomography Scans: A Systematic Literature Review

BACKGROUND

Hallux valgus is a multiplanar deformity that is often treated on the basis of 2-dimensional (2D) parameters and radiographs. Recurrence rates after surgical correction remain high, and failure to correct pronation of the metatarsal is increasingly stipulated as being part of the problem. Multiple methods of assessing metatarsal pronation have been proposed.

METHODS

We performed a systematic literature review identifying studies that measured metatarsal pronation and torsion on computed tomography (CT) scans. Specific methodology, patient groups, results, and reliability assessments were all reported.

RESULTS

We identified 14 studies that fulfilled the inclusion criteria. Eleven studies measured 2D values on CT scan, and 3 studies used computer-based 3-dimensional (3D) modeling and artificial intelligence systems to help calculate pronation. Metatarsal pronation angle, α angle, sesamoid rotation angle, and measurements for torsion were the most commonly used methods. All angles and measurements were performed as 2D measurements, but the metatarsal pronation angle was also performed with 3D modeling. Reliability and reproducibility of the α angle and metatarsal pronation angle were excellent, despite being performed on studies with small numbers.

CONCLUSION

Multiple methods have been reported to demonstrate first metatarsal pronation on CT, of which the α angle and the metatarsal pronation angle are the most pragmatic and useful in a clinical setting. Further work is needed to further validate the reliability of these measurements in larger series and to identify normal pronation and metatarsal torsion on weightbearing imaging. Further work is required to determine whether addressing pronation reduces recurrence rates and improves outcomes in surgery for hallux valgus.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Association Between Hindfoot Alignment and First Metatarsal Rotation

BACKGROUND

The association between forefoot and hindfoot position for planus and cavus feet is fundamental to the treatment of these deformities. However, no studies have evaluated the association between hindfoot alignment and first metatarsal (M1) axial rotation. Understanding this possible relationship may help to understand the deformity and improve patient care. The purpose of this study is to determine a correlation between hindfoot alignment and metatarsal rotation as assessed by weightbearing computed tomography (WBCT).

METHODS

Patients who underwent weightbearing plain radiography (WBPR) and WBCT between 2015 and 2018 were evaluated. Hindfoot alignment was measured with the calcaneal moment arm (CMA). M1 rotation was measured using the Kim and Saltzman angles. Patient subgroups were created according to the severity of valgus/varus hindfoot alignment. Statistical analyses were performed to evaluate for association between variables.

RESULTS

Among the 196 patient feet included in the study, the average CMA was 6.0 ± 16.2 mm. The average Kim and Saltzman angles were 7.7 ± 12.9 degrees and 2.8 ± 13.1 degrees, respectively. The average Meary angle was 182.0 ± 11.9 degrees. A moderately strong association was found between the CMA and the Saltzman (r = 0.641, P < .01) and Kim angles (r = 0.615, P < .01). Hindfoot valgus was associated with M1 pronation and hindfoot varus with M1 supination. Additionally, inverse relationships between the Meary angle and the Saltzman (r = -0.600, P < .01) and Kim angles (r = -0.529, P < .01) were identified.

CONCLUSION

In this well-defined cohort, we found substantial correlation between hindfoot alignment and M1 rotation. Hindfoot valgus was associated with M1 pronation, and hindfoot varus was associated with M1 supination. Surgeons correcting cavovarus/planovalgus deformities should be aware of this association and evaluate the need for first-ray derotation.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Management of the Tarsometatarsal Joint in the Rotational Correction of Hallux Valgus by the Modified Lapidus Procedure: Intraoperative Technical Tips to Prevent Complications

The modified Lapidus procedure is considered a useful tool for correction of multiplanar deformities in the hallux valgus, including first metatarsal pronation. It offers a greater power of correction compared to most other osteotomies. However, postoperative complications can occur in up to 12% of cases. The aim of this study was to describe intraoperative technical tips in the management of the tarsometatarsal joint during multiplanar correction of severe hallux valgus deformity using the modified Lapidus procedure. It is not the authors' intention to describe a new technique, but to draw attention to intraoperative details in order to prevent complications as nonunion, extension of the first metatarsal and undercorrection of the deformity. Rotational correction of the first metatarsal with adequate bone coaptation of the first metatarsal and the medial cuneiform are the cornerstone for a satisfactory result.Levels of Evidence: Level V, expert opinion.

Correction Power of Percutaneous Adductor Tendon Release (PATR) for the Treatment of Hallux Valgus: A Cadaveric Study

Osteotomies are commonly used in order to correct hallux valgus deformity. However, soft tissue structures also play an essential role in the etiology, progression, and treatment of hallux valgus (HV). The purpose of the present study was to analyze the correcting power (varus), reduction strength (sesamoid) and rotation of metatarsal and proximal phalanx after percutaneous adductor tendon release (PATR). To date, no study addresses this issue. Eleven cadaveric fresh-frozen below-the-knee cadaveric lower limbs with associated hallux valgus deformity were used. These specimens were subjected to a constant abduction force after PATR. HV and intermetatarsal angles showed statistically significant differences when comparing the preoperative and postoperative periods. PATR showed to be a reliable technique as the adductor tendon was completely released in 9 cases, and 75% released in the remaining 2 feet. The study supports that PATR provides powerful and quantifiable correction of HV deformity and can be accurately performed percutaneously.

Evaluation of a Weightbearing CT Artificial Intelligence-Based Automatic Measurement for the M1-M2 Intermetatarsal Angle in Hallux Valgus

BACKGROUND

Weightbearing cone beam computed tomography (WBCT) has been gaining traction as a useful imaging modality in the diagnosis and follow-up of foot and ankle musculoskeletal pathologies due to the ability to perform quick, low-dose, 3-dimensional (3D) scans. However, the resulting wealth of 3D data renders daily clinical use time-consuming. The aim of this study was to evaluate a new artificial intelligence (AI)-based automatic measurement for the M1-M2 intermetatarsal angle (IMA) in hallux valgus (HV). We hypothesized that automatic and manual measurements would have a strong correlation, and that the AI software would yield better reproducibility and would be faster compared with manual measurements.

METHODS

This was a multicenter retrospective comparative case-control study in which a total of 128 feet were included from 93 patients who underwent WBCT scans as part of their routine follow-up: 59 feet with symptomatic HV and 69 controls. The IMA was measured automatically using the AI software and manually on digitally reconstructed radiographs (DRRs). The AI software produced both an automatic 2D (auto 2D) and 3D (auto 3D) measurement.

RESULTS

There were strong intermethod correlations between the DRR IMA and the auto 2D (HV, r = 0.61; control, r = 0.60; all P < .0001) and auto 3D (HV, r = 0.63; control, r = 0.52; all P < .0001) measurements, respectively. The intrasoftware reproducibility was very close to 100%. Measurements took 23.6 ± 2.31 seconds and 14.5 ± 1.18 seconds, respectively, when taken manually on DRRs and automatically. Controls demonstrated a mean DRR IMA of 8.6 (95% CI, 8.1-9.1), mean auto 2D of 11.2 (95% CI, 10.7-11.7), and mean auto 3D IMA of 11.0 (95% CI, 10.5-11.5). The HV group demonstrated significantly increased IMA compared with controls (P < .0001), with a mean DRR IMA of 15.4 (95% CI, 14.8-16.1), mean auto 2D of 17.8 (95% CI, 17.2-18.4), and mean auto 3D IMA of 16.8 (95% CI, 16.8-17.4).

CONCLUSION

Measurements generated by the WBCT AI-based automatic measurement system for IMA demonstrated strong correlations with manual measurements, with near-perfect reproducibility. Further developments are warranted in order to make this tool more usable in daily practice, particularly with respect to its use in the presence of hardware in the foot.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Preoperative Guidance With Weight-Bearing Computed Tomography and Patient-Specific Instrumentation in Foot and Ankle Surgery

The use of preoperative and intraoperative guidance in foot and ankle surgery has grown substantially in recent years. Weight-bearing computed tomography (WBCT) and patient-specific instrumentation (PSI) are used in total ankle arthroplasty (TAA) to achieve precise bone cutting and implant positioning, and intraoperative 3-dimensional (3D) imaging has been used to reduce complications and improve clinical outcomes in other foot and ankle surgical procedures. This narrative review of the literature focuses on the evidence supporting the use of WBCT and PSI in TAA and looks at other promising technologies used to guide foot and ankle surgery.

The Assessment of First Metatarsal Rotation in the Normal Adult Population Using Weightbearing Computed Tomography

BACKGROUND

The importance of the rotational profile of the first metatarsal is increasingly recognized in the surgical planning of hallux valgus. However, rotation in the normal population has only been measured in small series. We aimed to identify the normal range of first metatarsal rotation in a large series using weightbearing computed tomography (WBCT).

METHODS

WBCT scans were retrospectively analyzed for 182 normal feet (91 patients). Hallux valgus angle, intermetatarsal angle, anteroposterior/lateral talus-first metatarsal angle, calcaneal pitch, and hindfoot alignment angle were measured using digitally reconstructed radiographs. Patients with abnormal values for any of these measures and those with concomitant pathology, previous surgery, or hallux rigidus were excluded. Final assessment was performed on 126 feet. Metatarsal pronation (MPA) and α angles were measured on standardized coronal computed tomography slices. Pronation was recorded as positive. Intraobserver and interobserver reliability were assessed using intraclass correlation coefficients (ICCs).

RESULTS

Mean MPA was 5.5 ± 5.1 (range, -6 to 25) degrees, and mean α angle was 6.9 ± 5.5 (range, -5 to 22) degrees. When considering the normal range as within 2 standard deviations of the mean, the normal range identified was -5 to 16 degrees for MPA and -4 to 18 degrees for α angle. Interobserver and intraobserver reliability were excellent for both MPA (ICC = 0.80 and 0.97, respectively) and α angle (ICC = 0.83 and 0.95, respectively). There was a moderate positive correlation between MPA and α angle (Pearson coefficient 0.68, P < .001).

CONCLUSION

Metatarsal rotation is variable in normal feet. Normal MPA can be defined as less than 16 degrees, and normal α angle can be defined as less than 18 degrees. Both MPA and α angle are reproducible methods for assessing rotation. Further work is needed to evaluate these angles in patients with deformity and to determine their significance when planning surgical correction of hallux valgus.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Multiplanar instability of the first tarsometatarsal joint in hallux valgus and hallux rigidus patients: a case-control study

BACKGROUND

Hypermobility of the first ray has been considered associated with various forefoot diseases including hallux valgus (HV) and hallux rigidus (HR). Weightbearing CT scan can be a reliable method for analysis of the first tarsometatarsal (TMT) joint in axial, sagittal, and coronal planes. Our objective was to comparatively investigate signs of instability of the first TMT joint on weightbearing CT between three groups (control, HV, and HR).

METHODS

In this single-centre, retrospective, case-control study, 27 HV patients (30 feet; mean age 54.2 years), 26 HR patients (30 feet; mean age 56.6 years), and 30 controls (30 feet; mean age; 43 years) were enrolled. Measurements of signs of instability were performed in multiplanes including first TMT angle, dorsal translation of the first metatarsal (M1) at the first TMT joint, plantar distance between the medial cuneiform (C1) and M1 in sagittal plane, hallux valgus angle (HVA), intermetatarsal angle (IMA) in axial plane, rotational profiles of C1 and M1 in coronal plane. Analysis of variance (ANOVA) test and chi-square test were performed to compare each parameter between the three groups. Interobserver reliabilities were assessed using interclass correlation coefficients (ICCs).

RESULTS

The HV group had significantly increased first TMT angle (0.23° in controls, 1.15° in HV, 0.19° in HR, p < 0.001), HVA (7.52°, 33.50°, 11.21°, p < 0.001), IMA (9.46°, 16.98°, 11.87°, p < 0.001), C1-M1 angle (22.44°, 29.46°, 23.74°, p < 0.001), and rotational profile of the distal M1 (7.06°, 17.88°, 9.85°, p < 0.001) compared with the control and HR groups. Dorsal translation of M1 (23% in controls, 63% in HV, 70% in HR, p < 0.001) was frequently found in the HV and HR groups with significantly increased plantar distance (0.37 mm, 1.14 mm, 1.46 mm, p < 0.001) compared with controls.

CONCLUSIONS

Multiplanar instability of the first TMT joint was confirmed using weightbearing CT in HV and HR groups compared with controls. HV group demonstrated instability mainly in sagittal and axial planes; HR group had sagittal instability predominantly. Our measurement of rotational instability at the first TMT joint was not able to detect differences between groups. A surgical correction of the instability at the first TMT joint can be an option to address HV and HR.

CLINICAL RELEVANCE

First ray hypermobility at the first TMT joint is an important consideration when addressing HV and HR, a surgical correction of the instability at the first TMT joint should be taken in consideration as an option.

Correlation between indirect radiographic parameters of first metatarsal rotation in hallux valgus and values on weight-bearing computed tomography

PURPOSE

To verify if indirect radiographic signs of first metatarsal pronation, determined by the head round sign, correspond to weight-bearing computed tomography (WBCT) measurements.

METHODS

In this case-control retrospective study, we analyzed 26 hallux valgus (HV) feet and 20 controls through conventional radiograph (CR) and WBCT images. Two blinded orthopaedic foot and ankle surgeons performed the measurements. Pronation classification (head roundness), head diameter (HD), traditional HV angles, arthritis, sesamoid positioning, and first metatarsal rotation angle (MRA) (alpha angle) were evaluated. Comparisons were performed by Student's T-test and a multivariate regression was executed. P-values less than 0.05 were considered significant.

RESULTS

Mean values were higher in HV patients than controls when evaluating MRA (11.51 [9.42-13.60] to 4.23 [1.84-6.62], 95%CI), HD (22.35 [21.52-23.18] to 21.01 [20.07-21.96]), and sesamoid rotation angle (SRA) (26.72 [24.09-29.34] to 4.56 [1.63-7.50]). The MRA had a low influence in head roundness classification (R²: 0.15). Changes in the pronation classification were explained chiefly by the sesamoid station (SS) (R²: 0.37), where stations 4 to 7 were found to be strong predictors of roundness classifications 2 and 3.

CONCLUSION

Indirect signs of metatarsal pronation, determined by the head round sign, correlate weakly with the alpha angle measured in WBCT. The presence of arthritis and sesamoids displacement might modify the perception of first head roundness. The influence of MRA in the classification was low, where SS from 4 to 7 was strong predictors of a higher pronation classification.

Outcome of proximal triple derotational metatarsal osteotomy for three-dimensional correction of hallux valgus deformity

PURPOSE

To correct hallux valgus deformities in patients with a greater pronation of the first metatarsal, we designed a novel proximal triple derotational metatarsal osteotomy (PTDMO), which could be used to achieve three-dimensional correction of hallux valgus deformities at the proximal metatarsal level.

METHODS

We prospectively evaluated the radiographic and clinical outcomes of 13 consecutive cases underwent PTDMO between November 2018 and May 2020. The minimum follow-up for inclusion was 12 months. The hallux valgus angle (HVA), first-to-second intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), relative length of the second metatarsal, and medial sesamoid position on the weight bearing foot anteroposterior radiographs, and the degree of the first metatarsal pronation on forefoot axial radiographs were measured pre-operatively, at six weeks post-operatively, and at the final follow-up. The American Orthopaedic Foot and Ankle Society (AOFAS) score and Foot Ankle Outcome Scores (FAOS) were measured.

RESULTS

In the comparison of pre-operative and final follow-up parameters, HVA, IMA, and DMAA were significantly improved post-operatively (all, P < 0.001). The relative length of the second metatarsal did not differ significantly post-operatively (P = 0.724). The medial sesamoid was significantly reduced (P = 0.01), and the first metatarsal pronation decreased by 10.16° (P = 0.034). Regarding clinical parameters, the AOFAS score and FAOS in all categories significantly improved post-operatively (all, P < 0.001).

CONCLUSION

PTDMO resulted in satisfactory radiographic and clinical outcomes with respect to deformity correction and pain relief, with significant post-operative reduced pronation of the first metatarsal.

Correlation of Different Methods of Measuring Pronation of the First Metatarsal on Weightbearing CT Scans

BACKGROUND

There is no consensus in the foot and ankle literature regarding how to measure pronation of the first metatarsal in patients with hallux valgus. The primary purpose of this study was to compare 2 previously published methods for measuring pronation of the first metatarsal and a novel 3-dimensional measurement of pronation to determine if different measurements of pronation are associated with each other.

METHODS

Thirty patients who underwent a modified Lapidus procedure for their hallux valgus deformity were included in this study. Pronation of the first metatarsal was measured on weightbearing computed tomography (WBCT) scans using the α angle with reference to the floor, a 3-dimensional computer-aided design (3D CAD) calculation with reference to the second metatarsal, and a novel method, called the triplanar angle of pronation (TAP), that included references to both the floor (floor TAP) and base of the second metatarsal (second TAP). Pearson's correlation coefficients were used to determine if the 3 calculated angles of pronation correlated to each other.

RESULTS

Preoperative and postoperative α angle and 3D CAD had no correlation with each other (r = 0.094, P = .626 and r = 0.076, P = .694, respectively). Preoperative and postoperative second TAP and 3D CAD also had no correlation (r = 0.095, P = .624 and r = 0.320, P = .09, respectively). However, preoperative and postoperative floor TAP and α angle were found to have moderate correlations (r = 0.595, P = .001 and r = 0.501, P = .005, respectively).

CONCLUSION

The calculation of first metatarsal pronation is affected by the reference and technique used, and further work is needed to establish a consistent measurement for the foot and ankle community.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Normative Distribution of First Metatarsal Axial Rotation

BACKGROUND

First metatarsal (M1) axial rotation is recognized as a clinically relevant component of hallux valgus deformity. Methods to realign the M1 in 3 dimensions have been developed. One goal of these operations is to restore normal rotation of the first ray. The aim of this study is to provide estimates for the normal distribution of M1 rotation in patients without relevant anatomic pathology.

METHODS

Using stringent clinical and radiographic criteria, we evaluated a set of plain radiograph and weightbearing computed tomography (WBCT) images of 62 feet from a consecutive patient database. Subjects included had normal foot alignment without bunion symptoms. M1 rotation of each foot was measured using 2 unique methods (Saltzman et al and Kim et al methods). Measurement of rotation was performed by 2 observers from coronal WBCT images. Mean values and confidence intervals (CIs) of M1 rotation were calculated for each method. Inter- and intraobserver reliability values were also reported.

RESULTS

Mean M1 rotation values of 2.1 degrees (95% CI: 0.9-3.4) and 6.1 degrees (95% CI: 4.4-7.8) were identified using the Saltzman et al and Kim et al methods, respectively. Inter- and intraobserver reliability values were interpreted as excellent for both methods.

CONCLUSION

In this study, we describe the natural distribution of the M1 axial rotation in subjects without bunion or other identifiable bony foot deformities. This information should provide a normative reference for surgeons correcting rotational issues of the first metatarsal.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

A prospective study to compare the operative outcomes of minimally invasive proximal and distal chevron metatarsal osteotomy for moderate-to-severe hallux valgus deformity

PURPOSE

The effectiveness of minimally invasive surgery (MIS)-distal chevron metatarsal osteotomy (DCMO) for the correction of moderate-to-severe hallux valgus deformity is unclear. This study aimed to compare the radiographic and clinical outcomes of our novel MIS-proximal chevron metatarsal osteotomy (PCMO) with those of MIS-DCMO performed during the same timeframe.

METHODS

We prospectively compared the outcomes of patients who underwent MIS-PCMO (n = 20 patients; 22 cases) with those of patients who underwent MIS-DCMO (n = 23 patients; 26 cases) for moderate-to-severe hallux valgus deformity (hallux valgus angle [HVA] ≥ 30° and first-to-second intermetatarsal angle [IMA] ≥ 13°) between June 2017 and January 2019. The minimum follow-up duration for study inclusion was two years. The HVA, IMA, distal metatarsal articular angle (DMAA), relative length of the second metatarsal, medial sesamoid position, and Meary's angle to evaluate the degree of deformity correction and its maintenance were measured pre-operatively and at the final follow-up.

RESULTS

Compared with MIS-DCMO, MIS-PCMO resulted in significantly greater correction of the HVA (P < 0.001) and IMA (P = 0.01), along with Meary's angle improvement (P < 0.001); however, the DMAA worsened (P = 0 .01). Furthermore, a significantly greater change was found in the relative second metatarsal length in the MIS-DCMO group (P = 0.01). No significant between-group differences were noted in the correction of the medial sesamoid position (P = 0.445).

CONCLUSION

Compared with MIS-DCMO, MIS-PCMO can be a better option for correcting moderate-to-severe hallux valgus deformities. However, this technique should be applied carefully when the pre-operative DMAA is already large because the DMAA can become worse post-operatively.

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.

Geometric 3D analyses of the foot and ankle using weight-bearing and non weight-bearing cone-beam CT images: The new standard?

OBJECTIVES

We hypothesize that three-dimensional (3D) geometric analyses in weight bearing CT-images of the foot and ankle are more reproducible compared to two-dimensional (2D) analyses. Therefore, we compared 2D and 3D analyses on bones of weight-bearing and non weight-bearing cone-beam CT images of healthy volunteers.

METHODS

Twenty healthy volunteers (10 male, 10 female, mean age 37.5 years) underwent weight-bearing and non weight-bearing cone-beam CT imaging of both feet. Clinically relevant height and angle measurements were performed in 2D and 3D (for example: cuboid height, calcaneal pitch, talo-calcaneal angle, Meary's angle, intermetatarsal angle). Three-dimensional measurements were obtained using automated software. Intra-observer and inter-observer agreement were evaluated for all 2D measurements.

RESULTS

Overall intraclass correlation coefficients (ICC's) were higher than 0.750 for most 2D measurements, ranging from 0.352 to 0.995. Calcaneal pitch, angle between the first metatarsal (MT1) and proximal phalange 1, between the fifth metatarsal (MT5) and the calcaneus and heights of the sesamoid bones, navicular, cuboid and talus decreased during weight-bearing in both 2D and 3D results (p < 0.01). Meary's angle was not statistically different in 2D (p = 0.627) and 3D (p = 0.765). Higher coefficients of variation in 2D geometric analysis parameters (0.27 versus 0.16) indicate that 3D analyses are more precise compared to 2D (p < 0.01). Results of left and right feet are comparable for 2D and 3D analyses.

CONCLUSION

Although 2D and 3D geometrical analyses are fundamentally different, automated 3D analyses are more reproducible and precise compared to 2D analyses. In addition, 3D evaluation better demonstrates differences in bone configurations between weight-bearing and non weight-bearing conditions, which may be of value to demonstrate pathology.

The Role of Weightbearing Computed Tomography Scan in Hallux Valgus

BACKGROUND

Hyperpronation of the first metatarsal in hallux valgus (HV) is poorly understood by conventional weightbearing radiography. We aimed to evaluate this parameter using weightbearing computed tomography (WBCT) and to understand its association with other standard measurements.

METHODS

Retrospective evaluation of WBCT and weightbearing radiographs (WBXRs) was performed for 20 patients with HV feet and 20 controls with no such deformity. Axial computed tomography images of both groups were compared for the first metatarsal pronation angle (alpha angle) and tibial sesamoid subluxation (TSS) grades. The HV angle (HVA), first-second intermetatarsal angle (IMA), first metatarsal-medial cuneiform angle (MMCA), Meary's angle, and calcaneal pitch (CP) angle of the study and control groups were compared on both WBXR and the corresponding 2-dimensional images of WBCT. All measurements were independently performed by 1 musculoskeletal radiology fellow and 1 foot and ankle surgical fellow. Measurements were averaged and interobserver reliability was calculated.

RESULTS

The HV group demonstrated significantly higher values for TSS grade (P < .001) but not for alpha angle (P = .121) compared with controls. Likewise, significantly elevated HVA and IMA were noted in the HV group on both imaging modalities, while no such differences were observed for the CP angle. Higher MMCA and Meary's angle in the HV group were evident only on WBXR (MMCA, P = .039; Meary's, P = .009) but not on WBCT (MMCA, P = .183; Meary's, P = .171).Among all, the receiver operating characteristic (ROC) curves demonstrated the greatest area under the curve (AUC) for HVA, followed by IMA. The alpha angle performed only just outside the range of chance (AUC, 0.65; 95% CI, 0.52-0.69). The Pearson's correlations of the alpha angle, in the HV group, revealed a significant linear relationship with TSS grade and with HVA on WBXR, and only trended toward a weak linear relationship with IMA and with HVA on WBCT.

CONCLUSION

The alpha angle, a measure of abnormal hyperpronation of the first metatarsal, was an independent factor that may coexist with other parameters in HV, but in isolation had limited diagnostic utility. "Abnormal" alpha angles were even observed in individuals without HV. Increases in IMA and MMCA were not necessarily associated with similar increases in alpha angle, despite moderate correlations with TSS grade and HVA on WBXR. Nevertheless, the WBCT was a useful method for assessing hyperpronation and guiding surgical management in individual cases.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

A cone beam CT based 3D-assessment of bony forefoot geometry after modified Lapidus arthrodesis

BACKGROUND

Modified Lapidus arthrodesis (MLA) is a well-established treatment modality for hallux valgus deformities (HVD) associated with instability of the first ray. Although the three-dimensional (3D) nature of HVD has long been recognized, diagnostics still focus on plain radiographs. The objective of this study was to validate 3D Cone Beam CT (CBCT) in the perioperative assessment of HVD with focus on the alignment of the forefoot.

METHODS

In a prospective clinical study, MLA was performed on 30 patients (25 females, 5 males; mean age: 63.2 years). Pre- and postoperatively standard radiographs and CBCT with full weight-bearing were acquired. For the CBCT based assessment, reproducible criteria have been defined, measured, and correlated with established radiological indicators.

RESULTS

Evaluation of standard radiographic parameters (hallux-valgus angle [HVA], intermetatarsal angle 1-2 [IMA 1-2], distal metatarsal articular angle [DMAA], tibial sesamoid position [TSP]) showed significant improvement postoperatively. Comparison of measurements obtained from plain radiographs and CBCT were significantly correlated between both measuring techniques, indicating high reliability. Pronation of the first metatarsal and the sesamoids were significantly reduced by the procedure. Due to this repositioning effect, the second metatarsal head was elevated by 3.1mm, and the lateral sesamoid was lowered by 3.8mm. However, there was no correlation between the amount of pronation and conventional radiographic measures.

CONCLUSIONS

Compared to plain radiographs, CBCT allows a more detailed view of the forefoot alignment in the coronal plain after MLA. MLA was able to recenter the sesamoids under der first metatarsal head and conversely led to elevation of the second metatarsal head.

Weight-bearing CT Scans in Foot and Ankle Surgery

Weight-bearing CT (WBCT) scans of the foot and ankle have improved the understanding of deformities that are not easily identified on radiographs and are increasingly being used by orthopaedic surgeons for diagnostic and preoperative planning purposes. In contrast to standard CT scans, WBCT scans better demonstrate the true orientation of the bones and joints during loading. They have been especially useful in investigating the alignment of complex pathologies such as adult-acquired flatfoot deformity in which patients have been found to have a more valgus subtalar joint alignment than in a normal cohort and high rates of subfibular impingement. Studies using WBCT scans have also provided new insight into more common lower extremity conditions such as hallux valgus, ankle fractures, and lateral ankle instability. WBCT scans have allowed researchers to investigate pronation of the first metatarsal in patients with hallux valgus compared with normal feet, and patients with lateral ankle instability have been found to have more heel varus than healthy control subjects. Understanding the application of WBCT scans to clinical practice is becoming more important as surgeons strive for improved outcomes in the treatment of complicated foot and ankle disorders.

Metatarsal Pronation in Hallux Valgus Deformity: A Review

Hallux valgus deformity is a multiplanar deformity, where the rotational component has been recognized over the past 5 to 10 years and given considerable importance. Years ago, a rounded shape of the lateral edge of the first metatarsal head was identified as an important factor to detect after surgery because a less rounded metatarsal head was associated to less recurrence. More recently, pronation of the metatarsal bone was identified as the cause for the rounded appearance of the metatarsal head, and therefore, supination stress was found to be useful to achieve a better correction of the deformity. Using CT scans, up to 87% of hallux valgus cases have been shown to present with a pronated metatarsal bone, which highlights the multiplanar nature of the deformity. This pronation explained the perceived shape of the metatarsal bone and the malposition of the medial sesamoid bone in radiological studies, which has been associated as one of the most important factors for recurrence after treatment. Treatment options are discussed briefly, including metatarsal osteotomies and tarsometatarsal arthrodesis.

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

BACKGROUND

Weightbearing images are important to the diagnosis of foot pathologies as are the three dimensional views available from CT and MRI. Standard three-dimensional imaging hardware, however, does not have a simple tool to obtain weightbearing images. The current research aimed to design, build and test a simple device to apply load in a horizontal bore imaging facility.

METHODS

With the immediate need in hallux valgus studies, hallux valgus subjects were imaged using the new loading device, which could be easily transported and had no additional electronics.

RESULTS

Testing showed that the usual angular measures of the foot (intermetatarsal and hallux valgus) replicated the results from the standard of care standing plain film results. With application of load, HV angle changed from 29.9° non-weightbearing to 32.2° weightbearing, while IM angle changed from nonweightbearing 15.8° to weightbearing 16.5°.

CONCLUSION

The pedal-like device can provide weightbearing images in a horizontal bore MRI facility.

The influence of hallux valgus and flatfoot deformity on metatarsus primus elevatus: A radiographic study

BACKGROUND

Metatarsus primus elevatus (MPE), a dorsal elevation of the first metatarsal in relation to the lesser metatarsals on lateral-view radiographs, is an indicator of hallux rigidus. The angle between the articular surfaces of the base of the first metatarsal and the anterior part of the medial cuneiform (M₁C₁A) reflects the sagittal instability of the first tarsometatarsal (TMT) joint. MPE may also indicate instability of the first metatarsal. The purpose of this study was to identify the influence of hallux valgus (HV) and flatfoot (FF) deformities on measurements obtained from first metatarsal-related radiographic images.

METHODS

Standing radiographic images of 134 feet were investigated. In dorsoplantar-view radiographs, HV and intermetatarsal angles were evaluated. The position of the medial sesamoid was classified with a grading system (Hardy score). In lateral-view radiographs, MPE, M₁C₁A, and Meary's angle were measured. The subjects were divided into 4 groups: the normal group (G1), HV(-)FF(-); the HV group (G2), HV(+)FF(-); the FF group (G3), HV(-)FF(+); and the dual group (G4), HV(+)FF(+). The radiographic parameters were compared among the groups.

RESULTS

MPE in the HV patients (G2 and G4) was less than that in the non-HV participants (G1 and G3). MPE in G4 was less than that in G3. The odds ratios of the Hardy score were higher in G2, G3 and G4 than in G1. The ratios were higher in the FF patients (G3 and G4) than in the non-FF participants (G1 and G2) and were higher in G4 than in G2.

CONCLUSIONS

FF affects sesamoid dislocation, and the combination of HV and FF further increases sesamoid dislocation. Combined with M1C1A and the Hardy score, MPE may be a useful indicator of three-dimensional instability of the first TMT joint. First TMT joint-related operations may be considered for severe HV treatment in G4 patients.

Hypermobility in Hallux Valgus

The interaction between hypermobility and hallux valgus remains both contemporary and incendiary. The difficulty in setting clinical and radiological parameters to diagnose and the complexity of questions that circumnutate the philosophy among etiology and denouement, fires up the debate regarding these conditions. Outcomes among procedures that address or neglect ray instability are still used as argument for any group of believers or nonbelievers. Through proving the true existence of hypermobility and its relationship with bunions, our colleges and professors have produced an incredible amount of excellent data that helped us better comprehend the hallux valgus syndrome in a general manner.

Use of Advanced Weightbearing Imaging in Evaluation of Hallux Valgus

Hallux valgus (HV) represents a progressive 3-dimensional deformity that includes bone malalignment, hypermobility of the first ray, and imbalanced soft-tissue structures of the midfoot and forefoot. Conventional radiographs provide sectorized and limited information of the deformity in different planes. The literature evidence supporting the use of cone beam weightbearing computed tomography in the assessment of HV has been growing. It demonstrates important advances that include the ability to reliably perform traditional measurements such as HV angle and intermetatarsal angle in the 3-dimensional setting.

Effect of the Modified Lapidus Procedure on Pronation of the First Ray in Hallux Valgus

BACKGROUND

Hallux valgus (HV) is a triplanar deformity of the first ray including pronation of the first metatarsal with subluxation of the sesamoids. The purpose of this study was to investigate if a first tarsometatarsal fusion (modified Lapidus technique), without preoperative knowledge of pronation measured on weightbearing computed tomographic (CT) scans, changed pronation of the first metatarsal and determine if reduction of the sesamoids was correlated with changes in first metatarsal pronation.

METHODS

Thirty-one feet in 31 patients with HV who underwent a modified Lapidus procedure had preoperative and at least 5-month postoperative weightbearing CT scans and radiographs. Differences in preoperative and postoperative pronation of the first metatarsal using a 3-dimensional computer-aided design, HV angle, and intermetatarsal angle (IMA) were calculated using Wilcoxon signed-rank tests. After dividing patients into groups based on sesamoid station, Kruskal-Wallis H tests were used to compare first metatarsal pronation between the groups.

RESULTS

The mean preoperative and postoperative pronation of the first metatarsal was 29.0 degrees (range 15.8-51.1, SD 8.7) and 20.2 degrees (range 10.4-32.6, SD 5.4), respectively, which was a mean change in pronation of the first ray of -8.8 degrees (P < .001). There was no difference in pronation of the first ray when stratified by postoperative sesamoid position (P > .250). The average preoperative and postoperative IMA was 16.7 degrees (SD 3.2) and 8.8 degrees (SD 2.8), which demonstrated a significant change (P < .001).

CONCLUSIONS

The modified Lapidus procedure was an effective tool to change pronation of the first ray. Reduction of the sesamoids was not associated with postoperative first metatarsal pronation.

LEVEL OF EVIDENCE

Level IV, case series.

Relationship Between Demographic and Radiographic Characteristics and Second Ray Pathology in Hallux Valgus Patients

BACKGROUND

Hallux valgus can alter load bearing in the foot leading to abnormal forces on the second toe. The purpose of this study was to determine demographic and radiographic factors associated with second ray hammertoes in hallux valgus using 3-dimensional weightbearing CT scans.

METHODS

Seventy-one patients who underwent a modified Lapidus procedure for hallux valgus with preoperative weightbearing CT scans were separated into 2 groups: (1) hallux valgus only (47 feet) and (2) hallux valgus with second ray hammertoe (29 feet). Preoperative age, body mass index (BMI), sex, hallux valgus angle (HVA), intermetatarsal angle (IMA), absolute and effective metatarsal (MT) lengths, ratios between metatarsal lengths, Meary angle, metatarsus adductus angle (MAA), and pronation were measured. Mean values of continuous variables were compared and both simple and multivariable logistic regression models were used to evaluate associations between variables and hammertoe occurrence.

RESULTS

Patients in the hammertoe group were found to be significantly older and have higher BMIs, HVAs, effective second MT lengths, IMAs, and more apex plantar Meary angles (all P < .05). The multivariable analysis demonstrated that a higher IMA and a more apex plantar Meary angle were the only significant predictors of second ray hammertoe risk (P = .03 and P = .01, respectively) once corrected for age and BMI.

CONCLUSION

Significant associations were found between older age, higher BMI, and more severe deformity and the occurrence of hammertoe in hallux valgus patients. These results may help clinicians counsel hallux valgus patients about the risk of developing an advanced hammertoe deformity.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Relationships Between First Metatarsal and Sesamoid Positions and Other Clinically Relevant Parameters for Hallux Valgus Surgery

Relationships between hallux valgus (HV) and other measurements within the first ray have been extensively studied. It is becoming more popular to correct HV deformity with tarsometatarsal joint arthrodesis while internally (varus) rotating the first metatarsal. This, in turn, reduces the sesamoid position when viewed in the dorsoplantar projection on radiographs. However, it has been shown that not all HV deformities have pathological external (valgus) rotation of the first metatarsal. In this study, we explored the relationships between frontal-plane rotations of the first metatarsal as well as the sesamoids, and other factors not limited to the first ray, to better understand the pathological process of HV deformity and to assist in surgical planning. We found that when adjusting for these covariates, the only factor associated with first metatarsal external rotation was having less metatarsus adductus. Sesamoid rotation, on the other hand, was independently associated with the HV angle, tibial sesamoid position, and medial column collapse. When surgically treating HV, correction of sesamoid rotation may need to be prioritized.

Multicenter Early Radiographic Outcomes of Triplanar Tarsometatarsal Arthrodesis With Early Weightbearing

BACKGROUND

Hallux valgus is a multiplanar deformity of the first ray. Traditional correction methods prioritize the transverse plane, a potential factor resulting in high recurrence rates. Triplanar first tarsometatarsal (TMT) arthrodesis uses a multiplanar approach to correct hallux valgus in all 3 anatomical planes at the apex of the deformity. The purpose of this study was to investigate early radiographic outcomes and complications of triplanar first TMT arthrodesis with early weightbearing.

METHODS

Radiographs and charts were retrospectively reviewed for 57 patients (62 feet) aged 39.7 ± 18.9 years undergoing triplanar first TMT arthrodesis at 4 institutions between 2015 and 2017. Patients were allowed early full weightbearing in a boot walker. Postoperative radiographs were compared with preoperative radiographs for hallux valgus angle (HVA), intermetatarsal angle (IMA), tibial sesamoid position (TSP), and lateral round sign. Any complications were recorded.

RESULTS

Radiographic results demonstrated significant improvements in IMA (13.6 ± 2.7 degrees to 6.6 ± 1.9 degrees), HVA (24.2 ± 9.3 degrees to 9.7 ± 5.1 degrees), and TSP (5.0 ± 1.3 to 1.9 ± 0.9) from preoperative to final follow-up (P < .001). Lateral round sign was present in 2 of 62 feet (3.2%) at final follow-up compared with 52 of 62 feet (83.9%) preoperatively. At final follow-up, recurrence was 3.2% (2/62 feet), and the symptomatic nonunion rate was 1.6% (1/62 feet). Two patients required hardware removal, and 2 patients required additional Akin osteotomy.

CONCLUSION

Early radiographic outcomes of triplanar first TMT arthrodesis with early weightbearing were promising with low recurrence rates and maintenance of correction.

LEVEL OF EVIDENCE

Level IV, retrospective case series.