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

Outcome comparison of minimally invasive proximal and distal chevron Akin osteotomies in patients with severe hallux valgus deformity: A randomized prospective study

PURPOSE

To date, the surgical treatment of severe hallux valgus deformity remains challenging despite the various methods presented. This study aimed to compare the effectiveness of minimally invasive distal chevron Akin osteotomies (d-MICA) and minimally invasive proximal chevron Akin osteotomies (p-MICA) in correcting severe hallux valgus deformities.

METHODS

This prospective follow-up study included patients randomly assigned to undergo p-MICA or d-MICA for hallux valgus deformities with a preoperative hallux valgus angle (HVA) ≥ 40° and/or a first to second intermetatarsal angle (IMA) ≥ 16°. After a minimum follow-up period of two years, we compared various clinico-radiographic parameters of patients whose HVA exceeded 15° at the final follow-up.

RESULTS

In the p-MICA and d-MICA groups, seven of 40 cases (17.5%) and 16 of 41 cases (39.0%), respectively, exhibited HVA > 15° at the final follow-up (P = 0.048). The preoperative parameters showed no significant differences. However, at the first weight-bearing assessment, the HVA, IMA, and relative second metatarsal length were significantly smaller, and the distal metatarsal articular angle (DMAA) was greater in the p-MICA group (all P < 0.05) compared with the d-MICA group. Postoperatively, both groups exhibited significant decreases in HVA and IMA at the final follow-up (P < 0.001 for all parameters). The p-MICA group showed no significant changes in DMAA and the relative length of the second metatarsal (P = 0.253 and 0.185, respectively). However, the d-MICA group showed a significant decrease in DMAA (P < 0.001) and an increase in the relative length of the second metatarsal at the final follow-up (P = 0.01).

CONCLUSIONS

p-MICA and d-MICA procedures demonstrated effective correction potential for severe hallux valgus deformities; however, the d-MICA procedure exhibited a notably higher incidence of unsatisfactory correction at the final follow-up than p-MICA. Therefore, d-MICA may be less predictable in achieving successful outcomes than p-MICA in treating severe hallux valgus deformities.

Imaging of the post-operative hallux valgus: what do radiologists need to know?

Hallux valgus surgery concerns many patients and various techniques are performed. The assessment of the first toe deformity correction is mainly visual and imaging is required to analyze the intermetatarsal angle and depict complications. However, it is often difficult for the radiologist to distinguish normal and pathological conditions, especially in case of osteotomies which may show various aspects of bone mineralization and healing. In this review, the most relevant imaging features of the post-operative hallux valgus are summarized.

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.

First Metatarsal Rotation After Scarf Osteotomy for Hallux Valgus

BACKGROUND

Recurrence after surgical correction of hallux valgus may be related to coronal rotation of the first metatarsal. The scarf osteotomy is a commonly used procedure for correcting hallux valgus but has limited ability to correct rotation. Using weight-bearing computed tomography (WBCT), we aimed to measure the coronal rotation of the first metatarsal before and after a scarf osteotomy, and correlate these to clinical outcome scores.

METHODS

We retrospectively analyzed 16 feet (15 patients) who had a WBCT before and after scarf osteotomy for hallux valgus correction. On both scans, hallux valgus angle (HVA), intermetatarsal angle (IMA), and anteroposterior/lateral talus-first metatarsal angle were measured using digitally reconstructed radiographs. Metatarsal pronation angle (MPA), alpha angle, sesamoid rotation angle, and sesamoid position were measured on standardized coronal WBCT slices. Preoperative and postoperative (12 mo) clinical outcome scores (Manchester Oxford Foot Questionnaire and Visual Analogue Scores) were captured.

RESULTS

Mean HVA was 28.6 ± 10.1° preoperatively and 12.1 ± 7.7° postoperatively (P < .001). Mean IMA was 13.7 ± 3.8° preoperatively and 7.5 ± 3.0° postoperatively (P < .001). Before and after surgery, there were no significant differences in MPA (11.4 ± 7.7 and 11.4 ± 9.9°, respectively; P = .75) or alpha angle (10.9 ± 8.0 and 10.7 ± 13.1°, respectively; P = .83). There were significant improvements in sesamoid rotation angle (SRA) (26.4 ± 10.2 and 15.7 ± 10.2°, respectively; P = .03) and sesamoid position (1.4 ± 1.0 and 0.6 ± 0.6, respectively; P = .04) after a scarf osteotomy. There were significant improvements in all outcome scores after surgery. Poorer outcome scores correlated with greater postoperative MPA and alpha angles (r = .76 (P = .02) and .67 (P = .03), respectively).

CONCLUSION

A scarf osteotomy does not correct first metatarsal coronal rotation, and worse outcomes are linked to greater postoperative metatarsal rotation. Rotation of the metatarsal needs to be measured and considered when planning hallux valgus surgery. Further work was needed to compare postoperative outcomes with rotational osteotomies and modified Lapidus procedures when addressing rotation.Level of Evidence: 4.

Histopathological assessment of a two-stage reconstructive procedure of the infected Charcot foot

INTRODUCTION

Charcot neuropathic osteoarthropathy (CN) can be complicated by osteomyelitis (OM). Surgery is a standard procedure to treat OM including debridement and interposition of antibiotic-loaded cement (ABLC) spacer. The course of CN and OM was investigated on a histopathological level.

MATERIALS AND METHODS

Diabetic patients (n = 15) suffering from CN and midfoot OM underwent surgical debridement and interposition of ABLC was interposed. 6 weeks later, ABLC was removed and bone samples were taken again. Histopathological Charcot Score (HCS), Histopathological Osteomyelitis Evaluation Score (HOES) and microbiological assessment were used to evaluate osteomyelitic and neuroosteoarthropathic activity at both time points.

RESULTS

Interposition of ABLC leads to microbiological/histopathological eradication of OM in 73%/87% of patients. CN activity-measured by HCS-could be reduced from moderate to low activity by ABLC spacer and correlated with HOES.

CONCLUSIONS

CN activity could be reduced by surgery. It can be suggested that neuroosteoarthropathic activity measured by HCS is triggered by OM.

Sesamoid View Weightbearing Radiography vs Weightbearing Computed Tomography in the Measurement of Metatarsal Pronation Angle

BACKGROUND

First metatarsal pronation angle (MPA) is increasingly relevant in the management of hallux valgus and is assessed on weightbearing computed tomography (WBCT) and sesamoid-view weightbearing radiography (WBR). The purpose of this study is to compare MPA measured by WBCT against WBR to determine if any systematic discrepancy in MPA measurement exists between the 2 modalities.

METHODS

A total of 40 patients with 55 feet were included for study. MPA was measured in all patients by 2 independent readers on both WBCT and WBR with an appropriate washout period between measurement modalities. Mean MPA by WBCT and WBR were analyzed; interobserver reliability was calculated with an intraclass correlation coefficient (ICC) value.

RESULTS

Mean MPA as measured by WBCT was 3.7 ± 7.9 degrees (95% CI, 1.6-5.9; range -11.7 to 20.5). Mean MPA measured on WBR was 3.6 ± 8.4 degrees, (95% CI, 1.4-5.8; range -12.6 to 21.4). There was no difference in MPA as measured by WBCT compared to WBR (P = .529). Interobserver reliability was excellent with an ICC of 0.994 for WBCT and 0.986 for WBR.

CONCLUSION

Measurement of first MPA by WBCT and WBR was not significantly different. In our cohort of patients with and without forefoot pathology, we found that either sesamoid view weightbearing radiographs or weightbearing CT can be used reliably to measure first MPA and will generate similar values.

LEVEL OF EVIDENCE

Level IV, case series.

The Use of Advanced Semiautomated Bone Segmentation in Hallux Rigidus

Background:

Weightbearing computed tomography (WBCT) measurements allow evaluation of several anatomical points for a correct clinical-radiographic diagnosis of pathologies, such as hallux rigidus (HR). In addition, a new semiautomatic segmentation software obtains automated 3D measurements from WBCT scan data sets, minimizing errors in reading angular measurements. The study’s objective was (1) to evaluate the reliability of WBCT semiautomatic imaging measures in HR, (2) to evaluate correlation and agreement between manual and semiautomatic measures in the setting of HR, and (3) to compare semiautomatic measurements between pathologic (HR) and standard control groups.

Methods:

A retrospective study of HR patients was performed including 20 feet with HR. WBCT manual and semiautomatic 3D measurements were performed using the following parameters: (1) first metatarsal-proximal phalanx angle (1stMPP), (2) hallux valgus angle (HVA), (3) first to second intermetatarsal angle (IMA), (4) hallux interphalangeal angle (IPA), (5) first metatarsal length (1stML), (6) second metatarsal length (2ndML), (7) first metatarsal declination angle (1stMD), (8) second metatarsal declination angles (2ndMD), and (9) metatarsus primus elevatus (MPE). The differences between pathologic and control cases were assessed with a Wilcoxon test.

Results:

Interobserver and intraobserver agreement for manual vs semiautomatic WBCT measurements demonstrated excellent reliability. According to the Pearson coefficient, there was a strong positive linear correlation between both methods for the following parameters evaluated: HVA (ρ = 0.96), IMA (ρ = 0.86), IPA (ρ = 0.89), 1stML (ρ = 0.96), 2ndML (ρ = 0.91), 1stMD (ρ = 0.86), 2ndMD (ρ = 0.95), and MPE (ρ = 0.87). Comparison between the pathologic group with HR and the control (standard) group allowed for the differentiating of the pathologic (HR) from the non-pathologic conditions for MPE (p < 0.05).

Conclusion:

Semiautomatic measurements are reproducible and comparable to measurements performed manually, showing excellent interobserver and intraobserver agreement. The software used differentiated pathologic from nonpathologic conditions when submitted to semiautomatic MPE measurements.

Level of Evidence:

Level III, retrospective comparative study.

Weight-bearing cone-beam CT: the need for standardised acquisition protocols and measurements to fulfill high expectations-a review of the literature

Weight bearing CT (WBCT) of the lower extremity is gaining momentum in evaluation of the foot/ankle and knee. A growing number of international studies use WBCT, which is promising for improving our understanding of anatomy and biomechanics during natural loading of the lower extremity. However, we believe there is risk of excessive enthusiasm for WBCT leading to premature application of the technique, before sufficiently robust protocols are in place e.g. standardised limb positioning and imaging planes, choice of anatomical landmarks and image slices used for individual measurements. Lack of standardisation could limit benefits from introducing WBCT in research and clinical practice because useful imaging information could become obscured. Measurements of bones and joints on WBCT are influenced by joint positioning and magnitude of loading, factors that need to be considered within a 3-D coordinate system. A proportion of WBCT studies examine inter- and intraobserver reproducibility for different radiological measurements in the knee or foot with reproducibility generally reported to be high. However, investigations of test-retest reproducibility are still lacking. Thus, the current ability to evaluate, e.g. the effects of surgery or structural disease progression, is questionable. This paper presents an overview of the relevant literature on WBCT in the lower extremity with an emphasis on factors that may affect measurement reproducibility in the foot/ankle and knee. We discuss the caveats of performing WBCT without consensus on imaging procedures and measurements.

Impact of First Metatarsal Hyperpronation on First Ray Alignment: A Study in Cadavers

BACKGROUND

There is increased evidence of first metatarsal hyperpronation in patients with hallux valgus, but its impact on the stability of the first metatarsophalangeal and metatarsosesamoid joints is unknown. A previous biomechanical study showed that an increase in hallucal pronation might lead to medial soft tissue failure of the first metatarsophalangeal joint. Conversely, dynamic studies on hallux valgus have shown that the first tarsometatarsal joint moves in supination during weightbearing, and supination was associated with an increase in the intermetatarsal angle (IMA) and hallux valgus angle (HVA).

QUESTIONS/PURPOSES

(1) Does an increase in first metatarsal pronation cause an increase in hallucal pronation? (2) Can an intrinsic increase in first metatarsal pronation lead to first ray supination during weightbearing? (3) Can a combination of intrinsic first metatarsal hyperpronation and first metatarsophalangeal medial soft tissue failure increase supination of the first ray during weightbearing? (4) Is first ray supination during weightbearing associated with an increase in the IMA and HVA?

METHODS

Twelve transtibial, nonpaired cadaver specimens without deformities were used. Each specimen underwent six weightbearing CT scans under different conditions. The first three CT examinations were performed without any osteotomy of the first metatarsal. The first was a simulated nonweightbearing condition. The second was a simulated weightbearing condition. The third was a simulated weightbearing condition with medial soft tissue release. Subsequentially, a 30° pronation osteotomy of the first metatarsal was performed, and the same sequence of weightbearing CT images was obtained. On each weightbearing CT image, the HVA, IMA, sesamoid rotation angle, metatarsal pronation angle (MPA), metatarsosesamoid rotation angle, and hallucal pronation (HP) were measured. Motions were calculated based on the differential values of these angular measurements produced by the six different conditions (weightbearing, medial soft tissue release, 30° pronation osteotomy, and combinations of these conditions). We compared means using a t-test for normally distributed variables and the Mann-Whitney U test for nonnormally distributed variables. Correlations were assessed with Pearson product-moment correlation coefficients.

RESULTS

We found that 30° pronation osteotomy of the first metatarsal increased the MPA and HP by 28° ± 4° and 26° ± 6°, respectively, in the nonweightbearing condition. No differences between the increase in MPA and the increase in HP were noted (mean difference 2° [95% CI -1° to 5°]; p = 0.20). Therefore, an increase in first metatarsal pronation caused an increase in hallucal pronation. When a 30° pronation osteotomy of the first metatarsal was performed, the first ray motion during weightbearing went from pronation to supination (4° ± 2° in pronation without osteotomy versus 4° ± 2° in supination after the osteotomy, mean difference 8° [95% CI 6° to 9°]; p < 0.001). Therefore, an intrinsic increase in pronation of the first metatarsal led to a first ray supination motion during weightbearing. When a first metatarsophalangeal medial soft tissue release was performed in addition to the 30° osteotomy of the first metatarsal, the supination motion of the first ray increased (4° ± 2° without medial soft tissue release versus 11° ± 7° after the release, mean difference 8° [95% CI 3° to 12°]; p = 0.003). Therefore, a combination of intrinsic first metatarsal hyperpronation and first metatarsophalangeal medial soft tissue failure increased supination of the first ray during weightbearing. Regarding static angular measurements, the HVA and IMA were not correlated with the MPA (ρ = 0.20; p = 0.09 and ρ = 0.22; p = 0.07, respectively). Regarding motions, as the HVA and IMA increased from nonweightbearing to weightbearing the pronation decreased, with strong correlations (ρ = -0.82; p < 0.001 and ρ = -0.77; p < 0.001, respectively). Therefore, a first ray supination during weightbearing was associated with an increase in the HVA and IMA.

CONCLUSION

The combination of first metatarsal intrinsic hyperpronation and first metatarsophalangeal medial soft tissue failure led to a hallux valgus deformity in this cadaveric study. The static measurement of first metatarsal head pronation relative to the ground (MPA) did not reflect the real intrinsic pronation of the first ray, and foot and ankle specialists should be careful when interpreting these measurements. Hallux valgus is a dynamic condition, and the deformity could be more correlated with motions during weightbearing than with plain static measurements.

CLINICAL RELEVANCE

First ray supination compensating for first metatarsal intrinsic hyperpronation might be an important factor in the hallux valgus pathogenesis. Further in vivo studies involving nonweightbearing and weightbearing comparative assessments of hallux valgus and controls should be performed to confirm this pathomechanism.

Comparison between Weightbearing-CT semiautomatic and manual measurements in Hallux Valgus

BACKGROUND

Radiographic measurements are an essential tool to determine the appropriate surgical treatment and outcome for Hallux Valgus (HV). HV deformity is best evaluated by weight-bearing computed tomography (WBCT). The objective was (1) to assess the reliability of WBCT computer-assisted semi-automatic imaging measurements in HV, (2) to compare semi-automatic with manual measurements in the setting of an HV, and (3) to compare semi-automatic measurements between HV and control group.

METHODS

In this retrospective IRB (ID# 201904825) approved study, we assessed patients with hallux valgus deformity. The sample size calculation was based on the hallux valgus angle (HVA). Thus to obtain the 0.8 power, including 26 feet with HV in this study, was necessary. Our control group consisted of 19 feet from 19 patients without HV. Raw multiplanar data was evaluated using software CubeVue®. In the axial plane, hallux valgus angle (HVA), intermetatarsal angle (IMA), and interphalangeal angle (IPA) were measured. The semiautomatic 3D measurements were performed using the Bonelogic®Software. Inter-rater reliabilities were performed using ICC. Agreement between methods was tested using the Bland-Altman plots. The difference between Patologic and Control cases using semi-automatic measurements was assessed with the Wilcoxon signed-rank test. Alpha risk was set to 5% (α = 0.05). P ≤ 0.05 were considered significant.

RESULTS

Reliabilities utilizing ICC were over 0.80 for WBCT manual measurements and WBCT semi-automatic readings. Inter and intraobserver agreement for Manual and Semi-automatic WBCT measurements demonstrated excellent reliability.

CONCLUSIONS

Semi-automatic measurements are reproducible and comparable to measurements performed manually. The software differentiated pathological from non-pathological conditions when subjected to semi-automatic measurements. The development of advanced semi-automatic segmentation software with minimal user intervention is essential for the establishment of big data and can be integrated into clinical practice, facilitating decision-making.

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.

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.

Relationship Between Plantar Callosity and Foot Deformity in Hallux Valgus Using Weightbearing Computed Tomography

Plantar callosities under lesser metatarsals are often accompanied by the hallux valgus, and the cause of callosity is thought to be associated with the foot deformity, such as the metatarsal length discrepancy, the abnormal metatarsal head height, cavus, flat foot, and rheumatoid conditions. However, it is unclear which variable is most involved in the cause of callosity in hallux valgus deformity. To clarify the factors associated with the callosity with hallux valgus deformity, we conducted multiple image assessments based on weightbearing radiography and computed tomography. A retrospective review was performed based on the collection of clinical records from all patients with hallux valgus treated from 2010 to 2019 in our institution. We measured the hallux valgus angle, intermetatarsal angles, calcaneal pitch angles, talo-first metatarsal angles, metatarsal length, metatarsal head height, first metatarsal pronation angles, and sesamoid position with weightbearing radiography and computed tomography. We analyzed the relation between callosity formation and imaging assessments using univariate and multivariate logistic regression models. Fifty feet were retrospectively evaluated, and multiple logistic analyses by the stepwise method revealed that the first metatarsal-lateral-sesamoid distance was the only radiographical variable associated with callosity formation among all the tested variables (p < .001). As the grade of the callosity became more severe, the lateral shift of the lateral sesamoid increased. The position of the sesamoid bone appears to have a critical role in the assessment and choice of treatment protocols and further research needs to be conducted on the relationship with the position of sesamoid bone to elucidate the mechanism of callus formation.

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.

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.

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.

Correlations between weight-bearing 3D bone architecture and dynamic plantar pressure measurements in the diabetic foot

BACKGROUND

Measurements of plantar loading reveal foot-to-floor interaction during activity, but information on bone architecture cannot be derived. Recently, cone-beam computer tomography (CBCT) has given visual access to skeletal structures in weight-bearing. The combination of the two measures has the potential to improve clinical understanding and prevention of diabetic foot ulcers. This study explores the correlations between static 3D bone alignment and dynamic plantar loading.

METHODS

Sixteen patients with diabetes were enrolled (group ALL): 15 type 1 with (N, 7) and without (D, 8) diabetic neuropathy, and 1 with latent autoimmune diabetes. CBCT foot scans were taken in single-leg upright posture. 3D bone models were obtained by image segmentation and aligned in a foot anatomical reference frame. Absolute inclination and relative orientation angles and heights of the bones were calculated. Pressure patterns were also acquired during barefoot level walking at self-selected speed, from which regional peak pressure and absolute and normalised pressure-time integral were worked out at hallux and at first, central and fifth metatarsals (LOAD variables) as averaged over five trials. Correlations with 3D alignments were searched also with arch index, contact time, age, BMI, years of disease and a neuropathy-related variable.

RESULTS

Lateral and 3D angles showed the highest percentage of significant (p < 0.05) correlations with LOAD. These were weak-to-moderate in the ALL group, moderate-to-strong in N and D. LOAD under the central metatarsals showed moderate-to-strong correlation with plantarflexion of the 2nd and 3rd phalanxes in ALL and N. LOAD at the hallux increased with plantarflexion at the 3rd phalanx in ALL, at 1st phalanx in N and at 5th phalanx in D. Arch index correlated with 1st phalanx plantarflexion in ALL and D; contact time showed strong correlation with 2nd and 3rd metatarsals and with 4th phalanx dorsiflexion in D.

CONCLUSION

These preliminary original measures reveal that alteration of plantar dynamic loading patterns can be accounted for peculiar structural changes of foot bones. Load under the central metatarsal heads were correlated more with inclination of the corresponding phalanxes than metatarsals. Further analyses shall detect to which extent variables play a role in the many group-specific correlations.