Measurement of Dorsal First Ray Mobility: A Topical Historical Review and Commentary

Medial arch instability/internal foot overload association with non-insertional Achilles tendinopathy and the 'Zone of Conflict Theory'

BACKGROUND

Non insertional Achilles tendinopathy [AT] is a degenerative condition that is prevalent in runners. 30% have no preceding history and many runners do not develop AT. Overuse, pronation, and compromised blood supply are hypothesised as causal. The exact precipitant is still unknown. The link between medial arch instability and AT has not been made. The purpose of this study was to investigate the association between spring ligament (SL) laxity and first ray (FRI) instability, and the presence of (AT).

METHODS

Ethical approval was obtained. Patients were identified from hospital databases for unilateral AT, allowing the opposite unaffected foot to be used as an internal control. SL laxity was measured using the lateral translation score and FRI was measured using a modified digital Klauemeter. Ultrasound was used to assess the tendoachilles [TA] in affected vs unaffected legs.

RESULTS

17 patients were recruited with a mean age of 55.6 and mean body mass index (BMI) of 33.3. The average symptom duration was 3.62 years. There were 12 left feet and 5 right feet. There was no statistical difference in dorsiflexion angles for the TA or the gastrocnemius. All Beighton scores < 5. Lateral translation scores, FRI scores and TA thickness was significantly greater in AT feet [p < 0.05]. More affected feet had Tibialis posterior tendon pain (TP) [p < 0.05].

CONCLUSIONS

Feet with AT exhibit higher lateral translation scores and greater FRI compared to healthy feet, and combined with previous literature evidence, suggests alteration of the subtalar axis alters force moments that may lead to an intrinsic overload of the TA, when the foot enters a "zone of conflict". Medial arch instability, in particular SL laxity and FRI, may contribute to the development of non-insertional AT and treatment of this with early arch support may prevent progressive degeneration.

Diagnostic accuracy of clinical, radiological and device-driven tests for the detection of First Ray Instability: A systematic review

INTRODUCTION

First Ray Instability (FRI) and especially hypermobility leads to the collapse of the medial longitudinal arch's structural framework, which reduces the foot's ability to become a rigid lever for propulsion, resulting in progressive foot deformities. Early detection of FRI with prompt intervention helps prevent degenerative foot deformities. Various manual, device-based and radiographic diagnostic tests for FRI quantification have been described in the literature. We aim to conduct an up-to-date, comprehensive, systematic review of the literature reporting on diagnostic tests to evaluate FRI.

METHODOLOGY

Electronic databases (Medline, Embase and PubMed) and bibliography lists were searched until May 2021 for studies evaluating diagnostic tests for FRI. MeSH terms were used to conduct the literature search. The authors screened all produced abstracts. Selected articles were further assessed in full based on inclusion and exclusion criteria. The relevant studies were qualitatively assessed and grouped into tables based on tests.

RESULTS

18,176 studies were identified. Thirty-two full-text articles were included for assessment. Ten articles were excluded based on evaluation criteria. 18 studies were included for qualitative assessment: two studies describing manual diagnostic tests, three evaluating device-driven tests, six image-guided studies and seven comparison studies assessing a new test versus an established one.

CONCLUSION

Gold standard tests in defining FRI need to be improved. Manual tests exhibit significant subjective variability. Radiographic tests, while accurate, are complex and cumbersome to perform and, therefore, are not widely applied. Dorsal rulers have demonstrated mixed results and shown variability when compared to instruments. The focus has been on assessing FRI in hallux valgus (HV). More studies are needed to investigate FRI in the absence of HV.

Evaluation of first ray instability using the double dorsiflexion test: A prospective observational case-controlled study

BACKGROUND

First-Ray (FR) stability allows for foot propulsion in-stance, taking 60% weight. First-ray instability (FRI) is associated with middle column overload, synovitis, deformity and osteoarthritis. Clinical detection can still be challenging. We propose to develop a clinical test that helps identify FRI using two simple manual manoeuvres.

METHODS

10 patients with unilateral FRI were recruited. Unaffected contralateral feet were used as controls. Stringent exclusion criteria were applied including hallux MTP pain, laxity, inflammatory arthropathy and collagen disorders. A Klauemeter directly measured the sagittal plane dorsal first metatarsal head translation of affected vs unaffected feet. Maximum passive proximal phalanx 1st MTP joint dorsiflexion was measured using a video capture and Tracker motion software analysis with and without applying a dorsal force at the 1st metatarsal head using a Newton meter. Proximal phalanx motion was compared in affected vs unaffected feet with and without dorsal metatarsal head force application and compared to direct measurements using the Klaumeter. P value of < 0.05 was considered significant.

RESULTS

FRI feet had dorsal translation greater than 8 mm (median, 11.94; interquartile range [IQR], 10.23-13.81) vs 1.77 for unaffected control feet was (median, 1.77; interquartile range [IQR], 1.23-2.96) using the Klauemeter. The percentage reduction in 1st MTP joint dorsiflexion ROM when applying the double dorsiflexion test FRI (mean reduction of 67.98%) when compared to control feet (mean reduction of 28.44%)(P < 0.01). Receiver operating characteristic (ROC) analysis showed that a 50% reduction in dorsiflexion ROM of 1st MTPJ when performing the double dorsiflexion test achieved a specificity of 100% and sensitivity of 90% (AUC =0.990, 95%CI [0.958-1.000], P > 0.0001).

CONCLUSION

The double dorsiflexion (DDF) is easy to perform with two relatively simple manual manoeuvres that avoids the need for complex instrumented and radiation-based assessment. Greater than 50% decrease in proximal phalanx motion has an over 90% sensitivity in identifying feet with FRI.

LEVEL OF EVIDENCE

This was a prospective case-controlled study of consecutive cases of a level II evidence.

The Role of First Tarsometatarsal Joint Morphology and Instability in the Etiology of Hallux Valgus: A Case-Control Study

BACKGROUND

The morphology of foot joints is widely accepted as a significant factor in the development of various foot disorders. Nevertheless, the role of the first tarsometatarsal joint (TMT1) morphology in hallux valgus (HV) remains unclear, and its impact on TMT1 instability has not been fully explored. This study aimed to investigate the TMT1 morphology and its potential correlation with HV and TMT1 instability.

METHODS

Weightbearing computed tomography (WBCT) scans of 82 consecutive feet with HV and 79 controls were reviewed in this case-control study. Three-dimensional (3D) models of TMT1 were constructed using Mimics software and WBCT scans. The height of the TMT1 facet (FH) and the superior, middle, and inferior facet width (SFW, MFW, and IFW) were measured on anteroposterior view of the first metatarsal base. On the lateral view, the inferior lateral facet height and angle (ILFH and ILFA) were measured. TMT1 instability was evaluated using the TMT1 angle.

RESULTS

Compared with the control group, the HV group had a significantly wider MFW (9.9 mm in HV, 8.7 mm in control), lower ILFH (1.7 mm in HV, 2.5 mm in control), smaller ILFA (16.3 degrees in HV, 24.5 degrees in control), and larger TMT1 angle (1.9 degrees in HV, 0.9 degrees in control) (all P < .05). No significant differences were found between the 2 groups in FH, SFW, and IFW (all P > .05). The study identified 4 types of TMT1 morphology: continuous-flat, separated-flat, continuous-protruded, and separated-protruded. The continuous-flat type possessed significantly larger HVA, IMA, and TMT1 angles compared with other types (all P < .001).

CONCLUSION

This study indicates a potential association between TMT1 morphology and the severity of HV and identifies 4 TMT1 types. Notably, the continuous-flat type is found to be associated with more severe HV and TMT1 instability.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

An Operational Definition of First Ray Hypermobility

BACKGROUND

The first ray (metatarsocuneiform) behaves as a load-bearing strut in supporting weight. Due to its functional importance, stress-testing techniques are used to assess the stability of the first ray and objectify evidence of hypermobility. The test and measurement of first ray hypermobility (FRH) is of interest to clinicians and researchers. The condition itself, however, has proven elusive to diagnose. This article defines FRH for the purpose of improving the consistency by which the diagnosis is made. Currently, the lack of a consensus definition prevents research from determining the incidence rates and prevalence of FRH, a commonly reported medical condition.

THE DEFINITION

Symptomatic FRH presents as dorsal displacement that measures greater than 8 mm, accompanied with signs and symptoms consistent with loading insufficiency of the first ray. The operational definition is objective and if adopted across health care professions, the criterion could become the standard for identifying FRH in patients and research participants.

LEVEL OF EVIDENCE

Level V, expert opinion.

Is the Planus Foot Type Associated With First Ray Hypermobility?

Background:

Many foot pathologies have been associated with foot type. However, the association of first ray hypermobility remains enigmatic. The purpose of this study was to investigate first ray hypermobility among participants with planus and rectus foot types and its influence on static measures of foot structure.

Methods:

Twenty asymptomatic participants with planus (n = 23 feet) and rectus (n = 17 feet) foot types were enrolled. Several parameters of static foot structure (arch height index, arch height flexibility, first metatarsophalangeal joint flexibility, and first ray mobility) were measured. Participants were further stratified into groups with nonhypermobile (n = 26 feet) and hypermobile (n = 14 feet) first rays. First ray mobility ≥8 mm was used to define “first ray hypermobility”. Generalized estimating equations, best-fit regression lines, and stepwise linear regression were used to identify significant differences and predictors between the study variables

Results:

Overall, 86% of subjects categorized with first ray hypermobility exhibited a planus foot type. Arch height flexibility, weightbearing first ray mobility, and first metatarsophalangeal joint flexibility showed no significant between-group differences. However, weightbearing ray mobility and first metatarsophalangeal joint laxity were associated with partial weightbearing first ray mobility, accounting for 38% of the model variance.

Conclusion:

The planus foot type was found to be associated with first ray hypermobility. Furthermore, weightbearing first ray mobility and first metatarsophalangeal joint laxity were predictive of partial weightbearing first ray mobility, demonstrating an interaction between the translation and rotational mechanics of the first ray.

Clinical Relevance:

Association of first ray hypermobility with foot type and first metatarsophalangeal joint flexibility may help understand the sequela to symptomatic pathologies of the foot.

Comparative Reliability of a Novel Electromechanical Device and Handheld Ruler for Measuring First Ray Mobility

BACKGROUND

Quantifying first ray mobility is crucial to understand aberrant foot biomechanics. A novel device (MAP1^st) that can perform measurements of first ray mobility in different weightbearing conditions, foot alignments, and normalization was tested. The reliability of these measurement techniques was assessed in comparison to a handheld ruler considered representative of the common clinical examination.

METHODS

The study included 25 participants (50 feet). Two independent raters performed baseline, test-retest, and remove-replace measurements of first ray mobility with MAP1^st and the handheld device. The effects of non-, partial, and full weightbearing in subtalar joint neutral and the resting calcaneal stance position were assessed. Measurement normalization relative to foot size was also investigated. Intra- and interclass correlation coefficients (ICCs) were calculated for each device between the 2 raters. In addition, Bland-Altman plots were constructed to determine if fixed biases or substantial outliers were present.

RESULTS

Similar intrarater ICC values were found for both devices (≥0.85). However, interrater ICC values were substantially improved by MAP1^st compared with the handheld device (0.58 vs 0.06). Bland-Altman plots demonstrated biases of 1.27 mm for the handheld ruler, and 2.88 to 0.05 mm and -1.16 to 0.00 for linear and normalized MAP1^st measurements, respectively. Improved reliability was achieved with MAP1^st for normalized assessments of first ray mobility while the foot was placed in partial- and full-weightbearing resting calcaneal stance positions.

CONCLUSION

MAP1^st provided reliable assessments of partial- and full-weightbearing first ray mobility. It should help investigators to explore the potential relationships between first ray function and aberrant foot biomechanics in future research.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Spring ligament insufficiency and hallux valgus as an independent risk factors for first ray instability

INTRODUCTION

First ray instability (FRI) arising from failed plantar/interosseous ligaments is strongly associated with planovalgus, leading to synovitis and deformity. Our hypothesis is that proximal spring ligament insufficiency (SLI) drives secondary FRI in the absence of hallux valgus (HV) and may be an independent risk factor.

METHODS

Patients with FRI, screened by Klaue's test, were recruited. Patients' normal contralateral feet with previous radiographs were included as controls. First ray dorsal translation was measured with a digital Klauemeter. Spring ligament integrity was assessed using lateral translation distance as an indirect measure of spring ligament strain. Intermetatarsal angle and hallux valgus angle were recorded to classify the severity of HV.

RESULTS

Seventy feet included, 54 had symptomatic FRI and 16 were asymptomatic contralateral feet included as control. Twenty-three feet had moderate/severe HV and 47 had mild/normal HV. Moderate/severe HV was associated with FRI (OR, 10.31; p = 0.029). Forty-five feet with SLI had a strong association with FRI (OR, 100.7; p < 0.0001). SLI without moderate/severe HV was the most prevalent group (31/54), followed by SLI with moderate/severe HV, 29.63% (16/54). Moderate/severe HV without SLI was prevalent in 11.1% (6/54) and 1.85% (1/54) had no SLI or moderate/severe HV. In a multivariate logistic regression analysis model, both SLI and severe/moderate HV were independent predictors of FRI.

CONCLUSION

This is the first study that links SLI and HV as independent risk factors to FRI. 98.15% of FRI can be attributed to SLI, HV or both. First ray instability may allude to the strong presence of spring ligament insufficiency in the absence of hallux valgus.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Descriptive Quantitative Analysis of First Metatarsal Sagittal Plane Motion

Evaluation of the sagittal plane motion of the first ray is a commonly accepted physical examination technique performed during the assessment and treatment of the hallux valgus deformity. Excessive or abnormal motion in this location, termed "hypermobility," has also traditionally been strongly associated with surgical decision-making and serves as a widely accepted indication for performance of the first metatarsal-medial cuneiform arthrodesis procedure. The objective of this investigation was to perform an analysis of first ray sagittal plane motion from a large population in order to determine the descriptive quantitative characteristics of the data set. First metatarsal sagittal plane motion was measured from a group of 149 subjects (298 feet) with a Klaue device. The mean total first metatarsal sagittal plane motion was 9.37 ± 2.39 mm (3.97-18.76). The data set was found to demonstrate many of the characteristics of a normally distributed population based on the histogram distribution, skewness (0.651), and kurtosis (0.761). No difference was observed between measurement of total sagittal plane motion between right and left feet (9.13 ± 2.37 mm vs 9.61 ± 2.40 mm; p = .081), nor between male and female subjects (9.29 ± 2.27 mm vs 9.58 ± 2.70 mm; p = .352). No substantial correlation was observed between total sagittal plane motion and subject age (Pearson correlation -0.053; p = .522). Results indicate that first ray sagittal plane motion might be best considered as a continuous variable as opposed to categorical variable, and might help objectify the difference between "normal" and "abnormal" motion.

Foot structure and lower limb function in individuals with midfoot osteoarthritis: a systematic review

OBJECTIVE

To determine how foot structure and lower limb function differ between individuals with and without midfoot osteoarthritis (OA).

DESIGN

Electronic databases were searched from inception until May 2020. To be eligible, studies needed to (1) include participants with radiographically confirmed midfoot OA, with or without midfoot symptoms, (2) include a control group of participants without radiographic midfoot OA or without midfoot symptoms, and (3) report outcomes of foot structure, alignment, range of motion or any measures of lower limb function during walking. Screening and data extraction were performed by two independent assessors, with disagreements resolved by a third independent assessor. The methodological quality of included studies was assessed using the National Institutes of Health Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies.

RESULTS

A total of 1,550 records were screened by title and abstract and 11 met the inclusion criteria. Quantitative synthesis indicated that individuals who had midfoot OA had a more pronated foot posture, greater first ray mobility, less range of motion in the subtalar joint and first metatarsophalangeal joints, longer central metatarsals and increased peak plantar pressures, pressure time integrals and contact times in the heel and midfoot during walking. Meta-analysis could not be performed as the data were not sufficiently homogenous.

CONCLUSIONS

There are several differences in foot structure and lower limb function between individuals with and without midfoot OA. Future research with more consistent case definitions and detailed biomechanical models would further our understanding of potential mechanisms underlying the development of midfoot OA.

Pes Planus Deformity and Its Association With Hallux Valgus Recurrence Following Scarf Osteotomy

BACKGROUND

Hallux valgus recurrence is an unsatisfactory complication, with many causes postulated. This study investigated the effect of pes planus on recurrence after scarf osteotomy.

METHODS

A total of 183 feet were retrospectively reviewed. All patients were treated with a scarf osteotomy and if required Akin osteotomy. We measured preoperative lateral talus first metatarsal angle (T1MA) to study pes planus; an angle of under -4 degrees was considered pes planus. We measured pre and postoperative hallux valgus angle (HVA), intermetatarsal angle (IMA), and sesamoid location. In total 164 feet were suitable for inclusion, with follow-up of at least 6 months (10 males and 154 females, mean age: 52 years).

RESULTS

Recurrence frequency (HVA greater than 15 degrees) was 27 feet (16%). Hallux valgus recurrence was not influenced by gender (P value = .66) or preoperative IMA (P value = .48). Preoperative HVA greater than 35 degrees was associated with increased frequency of recurrence (P value = .004). Those with T1MA less than -10 degrees demonstrated progression in HVA and deterioration in sesamoid location up to 6 months postoperatively (P value = .038). HVA did not progress beyond 6 months. The prevalence of recurrent hallux valgus with normal T1MA was 1%, in T1MA -4 to -10 degrees it was 29% and in T1MA less than -10 degrees it was 47% (P value <.001). Breaks in T1MA less than -4 degrees were found at the naviculocuneiform joint in 68% of feet in this series.

CONCLUSION

The prevalence of hallux valgus recurrence correlated with the severity of pes planus.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Hypermobility of the First Ray: the Cinderella of the measurements conventionally assessed for correction of Hallux Valgus

Background and aim of the work:

hypermobility of the first ray (FRH) began to be considered as a pathological entity from Morton’s studies and was associated as a primary cause of hallux valgus (HV). Currently, this relationship is in discussion, and various authors consider FRH as a consequence of the deformity. The purpose of this narrative review is to summarise the most influential publications relating to First Ray Mobility (FRM) to increase knowledge and promote its conventional assessment during clinical practice.

Methods:

papers of the last century were selected to obtain a homogeneous and up-to-date overview of I-MTCJ mobility and HV, as well as their relationship and management.

Results:

in recent years, FRH was studied from a biomechanical and pathophysiologic point of view. There is still not enough data regarding the aetiology of FRM. The higher rate of instability found in HV lacks an explanation of which is the cause and which is the effect. However, the Lapidus arthrodesis is still a valid method in cases of FRH and HV, even if is not rigorously indicated to treat both. When approaching FRH, radiographic or clinical findings are mandatory for the right diagnosis.

Conclusions:

FRM is an important factor that must be considered in routine clinical practice and prior and post HV surgery, as much as the conventional parameters assessed. Surgeons should consider performing I-MTCJ arthrodesis only if strictly necessary, also paying attention to soft tissue balancing. Improving the measurement of FRH could be useful to determine if it is a cause or effect of the HV deformity. (www.actabiomedica.it)

The Validity and Reliability of a New Simple Instrument for the Measurement of First Ray Mobility

Several methods have been described to quantify the first ray mobility. They all have certain disadvantages (great size, sophistication, or lack of validation). The objective of this work was to study the validity and reliability of a new instrument for the measurement of first ray mobility. Anterior-posterior radiographs were obtained from 25 normal feet and 24 hallux valgus feet, with the first ray in a neutral position, maximally dorsiflexed and maximally plantarflexed. The first ray mobility was radiographicaly measured in both groups, and was also manually examined with the new device. A cluster analysis determined whether normal and hallux valgus feet were correctly classified, and a graphic analysis of Bland-Altman was performed to compare the radiographic and manual measurement techniques. Based on the radiographs, the first ray mobility only showed significant differences in dorsiflexion between both groups (P = 0.015). First ray dorsiflexion, plantarflexion and total range of motion measured with the new device were different between both groups (P = 0.040, P = 0.011 and P = 0.006, respectively). The silhouette measure of the cohesion and separation coefficients from the cluster analysis was greater than 0.50 for the dorsiflexion, plantarflexion and total range of motion obtained from the radiographs and from the new device. The Bland-Altman graph suggested that 96% of the data presented agreement between both measurement methods. These results suggested that the new instrument was valid and reliable.