Morton neuroma: evaluated with ultrasonography and MR imaging

A Characteristic Magnetic Resonance Imaging Finding to Identify Morton Neuroma: The Slug Sign

Background

Morton neuroma is a common cause of forefoot pain and sensory disturbances, but it is difficult to identify on magnetic resonance imaging (MRI). The aim of this study was to verify the usefulness of a characteristic MRI finding (slug sign) for identifying Morton neuroma and to clarify the relationship between excised neuroma characteristics and preoperative MRI findings.

Methods

Twenty-two web spaces were retrospectively assessed from the second and third intermetatarsal spaces of 11 feet of 10 patients (7 women and 3 men, aged average 59.5 years) who underwent surgical excision of Morton neuroma between 2017 and 2022. Asymptomatic web spaces were used as control. Neuromas with 2 branches of the plantar digital nerves on axial T1-weighted MRI (MRI-T1WI) were considered the slug sign. We investigated the preoperative presence of the slug sign in Morton neuroma and asymptomatic control web spaces. We also investigated the relationship between the maximum transverse diameter of the excised specimen and that estimated on coronal MRI-T1WI.

Results

A total of 15 Morton neuromas were excised and assessed. The slug signs were present in 10 intermetatarsal spaces in 15 web spaces with Morton neuroma whereas the sign was found in 1 intermetatarsal space in 7 asymptomatic web spaces. The sensitivity and specificity for the slug sign to diagnose Morton neuroma was 66.7% and 85.7%, respectively. The positive and negative predictive values were 90.9% and 54.5%, respectively. The mean maximum transverse diameter of excised neuromas was 4.7 mm. The mean maximum transverse diameter of neuromas on coronal MRI-T1WI was 3.4 mm. A significant positive correlation was found between the maximum transverse diameters of excised specimens and diameters estimated on coronal MRI-T1WI (r = 0.799, P < .001).

Conclusion

The slug sign may be a useful indicator of Morton neuroma on MRI to confirm nerve involvement after bifurcation.

Level of Evidence

Level IV, retrospective series.

Comparing Clinical Examination and Radiological Evaluation in the Preoperative Diagnosis and Location of Symptomatic Interdigital (Morton's) Neuroma

This study investigates whether clinical examination is as sensitive as ultrasound and magnetic resonance imaging (MRI) in the diagnosis and localization of symptomatic interdigital neuroma. A retrospective cohort study was conducted at two tertiary centers on all consecutive patients who underwent excision by a single foot and ankle specialist surgeon for a presumed interdigital neuroma between January 2008 and December 2020. Investigators collected preoperative clinical findings, radiological investigations, and postoperative outcomes. Sensitivity and positive predictive values were calculated and Z-score for 2 populations proportions was performed. One hundred fourteen consecutive patients were operated on for 131 suspected interdigital neuroma. Thirteen patients were excluded due to lack of adequate clinical documentation. Of the remaining 101 patients with 118 suspected interdigital neuroma, 115 were confirmed histologically (97.5%). The sensitivity of clinical assessment to accurately diagnose and place an interdigital neuroma in the correct space was calculated as 96.5%. The most common preoperative clinical feature was pain (99.2%). The calculated sensitivity for ultrasound to accurately diagnose an interdigital neuroma was 83.6%, and to correctly locate neuroma was 79.5% respectively, which were both statistically different compared to clinical assessment (p value: <.001 and p value: <.001). The calculated sensitivity for MRI to accurately diagnose an interdigital neuroma was 93.6%, which was statistically different to clinical assessment (p value: .005). Preoperative clinical assessment has the highest sensitivity to accurately diagnose interdigital neuroma when compared to MRI and ultrasound. Preoperative clinical assessment has higher sensitivity to accurately locate interdigital neuroma when compared to ultrasound.

Differential Diagnosis of Metatarsalgia

Lesser (or central) metatarsalgia is defined as pain in the forefoot under or around the lesser metatarsals and their respective metatarsophalangeal joints. Two common causes of central metatarsalgia are Morton's neuroma (MN) and plantar plate (PP) injury. Because both clinical and imaging features overlap, establishing the correct differential diagnosis may be challenging. Imaging has a pivotal role in the detection and characterization of metatarsalgia. Different radiologic modalities are available to assess the common causes of forefoot pain, so the strengths and weakness of these imaging tools should be kept in mind. It is crucial to be aware of the pitfalls that can be encountered in daily clinical practice when dealing with these disorders. This review describes two main causes of lesser metatarsalgia, MN and PP injury, and their differential diagnoses.

Relationship Between Sensory Symptoms, Mulder's Sign, and Dynamic Ultrasonographic Findings in Morton's Neuroma

BACKGROUND

Morton's neuroma (MN) is often a diagnostic dilemma lacking a gold standard set of diagnostic criteria. Advanced imaging of MN is evolving including ultrasonography. The current study aimed to analyze the relationship between ultrasonographic findings and symptoms, clinical data, and operative findings in a subgroup of patients.

METHODS

We evaluated physical examination, ultrasonographic findings, symptoms, and in a subgroup, the operative findings for Morton's neuroma. We analyzed the symptoms, the findings on physical examination, and ultrasonography data and performed a statistical correlation between them. A total of 175 patients were seen for suspected Morton's neuroma during the last 7 years.

RESULTS

Neuropathic pain of the toes was reported in 63% of patients. Presence of ultrasonographic findings suggesting Morton's neuroma was observed in 77% of cases. A mild significant relationship between neuropathic pain and positive ultrasonographic findings was observed. We found a strong correlation between ultrasonographic and clinical evaluation, but more than half with clinical negative Morton's neuroma had positive findings at ultrasonography. In the subgroup of operatively treated patients (n = 44) surgery confirmed Morton's neuroma in all patients who had positive ultrasonography findings.

CONCLUSIONS

The current study suggests that the association of ultrasonographic evaluation and clinical evaluation can be very useful for the management of Morton's neuroma. Our study could help with the development of a multiperspective approach in the diagnosis of Morton's neuroma.

LEVEL OF EVIDENCE

Level II, prospective cohort survey study.

First webspace Morton's neuroma case report with literature review

Morton's neuromas are benign lesions of the inter-digital nerves within the foot. They are most commonly found in the second and third webspace. Morton's neuroma of the first webspace is very rare. A case of a 42-year-old female who presented complaining of long standing forefoot pain is presented. The patient was diagnosed with a soft tissue tumor in the 1st webspace. An excisional biopsy of the tumour confirmed a Morton's neuroma. Very few cases of Morton's neuroma in the first webspace have been reported in the literature.

Morton's neuroma: review of anatomy, pathomechanism, and imaging

Morton's neuroma is a commonly encountered cause of forefoot pain, which may limit weight-bearing activities and footwear choices. Although the aetiology and pathomechanism of this condition is controversial, the histological endpoint is well established as benign perineural fibrosis of a common plantar digital nerve, typically within the third intermetatarsal space. The diagnosis of Morton's neuroma is mainly based on characteristic symptoms and clinical findings, but may be confirmed by ultrasonography. Although ultrasound is a highly accurate diagnostic tool for Morton's neuroma, it is subject to interoperator variability due to differences in technique and level of experience. In this paper, the authors review the anatomy of the common plantar digital nerves and surrounding structures in the forefoot, which are deemed relevant to the understanding of Morton's neuroma, especially from a sonographic point of view. Several theories of the pathomechanism of Morton's neuroma are briefly discussed. The main purpose of this article is to illustrate the ultrasound techniques for evaluating Morton's neuroma and performing ultrasound-guided corticosteroid injections.

ACR Appropriateness Criteria® Chronic Foot Pain

Chronic foot pain is a frequent clinical complaint, which can significantly impact the quality of live in some individuals. These guidelines define best practices with regards to requisition of imaging studies based on specific clinical scenarios, which have been grouped into different variants. Each variant is accompanied by a brief description of the usefulness, advantages, and limitations of different imaging modalities. The present narrative is the result of an exhaustive assessment of the available literature and a thorough review process by a panel of experts on Musculoskeletal Imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Anatomic basis for a new ultrasound-guided, mini-invasive technique for release of the deep transverse metatarsal ligament

Introduction

Morton's neuroma is an entrapment neuropathy of the third common plantar digital nerve, caused by the deep transverse metatarsal ligament (DTML). Minimally invasive or percutaneous surgery is a very common procedure, but surgical effectivity of this technique remains controversial. The goal of our study was to prove the effectiveness and safety of a new ultrasound‐guided technique for DTML‐release in a cadaver model.

Materials, Methods, and Results

The DTML was visualized in 10 fresh frozen donated body to science‐feet (eight male and two females, five left and five right) using an US device (GE Logic R7; 13 MHz linear probe, Madrid, Spain). Consecutively, minimally invasive ultrasound‐guided surgery was performed. Exclusion criteria of the donated bodies to science were previous history of forefoot surgery and space occupying mass lesions. The complete release of the ligament was achieved in all specimens without damage of any important anatomical structures as proven by anatomical dissection.

Conclusions

The results of this study indicate that our novel approach of an ultrasound‐guided release of the DTML is safer and more effective compared to blind techniques. The DTML could reliably be visualized and securely cut through a dorsal, minimally invasive surgical incision of only 2 mm.

Interdigital Commissural Approach for Morton's Neuroma

BACKGROUND

Morton's neuroma is a frequent cause of metatarsalgia. Operative treatment is indicated if nonoperative management has failed. The objective of the present study was to describe a technique of Morton's neuroma excision by a minimally invasive commissural approach and evaluate the long-term outcome and complications.

METHODS

A retrospective study of 108 patients with Morton's neuroma treated surgically with a commissural approach between September 1990 and December 2010 was performed. The surgical technique is described. Clinical outcomes and complications were evaluated. The average follow-up was 121 months. Eleven patients were men and 97 women. The average age was 49.4 years; 56.8% neuromas were at the third space and 43.2% at the second space. Six patients presented 2 neuromas in the same foot, and 9 patients had bilateral neuroma.

RESULTS

The visual analog scale (VAS) average pain score was 5.4 points preoperatively and 0.2 points at the final follow-up. The author found a significant difference between the VAS scores preoperatively and postoperatively (P < .01). Excellent and good satisfaction outcomes were achieved in 93.6%. The postoperative complication incidence was 3%.

CONCLUSION

The author believes a minimally invasive commissural approach has advantages over a dorsal or plantar incision. It is a simple and reproducible technique, with satisfactory outcomes, low complication rates, and a quick return to usual activities.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Sex Correlation to the Prevalence of Pedal Neuromas in Various Interspaces: A Retrospective Study

BACKGROUND

Morton's neuromas are abnormalities of the common digital nerve branch located between the lesser metatarsal heads. Historically, interdigital (Morton's) neuromas have been characterized as being most common in the third interspace and in females. The principal investigator observed Morton's neuromas commonly in the second and third interspaces in both sexes. To our knowledge, no literature exists to evaluate Morton's neuroma location with a focus on each sex independently. The present study evaluates Morton's neuroma interspace location and whether there is a variation by sex.

METHODS

In this retrospective study, 582 deidentified magnetic resonance imaging reports with a diagnosis code for Morton's neuroma were evaluated for patients scanned from January 2, 2015, through April 19, 2016. Incomplete records and those with radiologist findings inconsistent with Morton's neuroma were eliminated. For the remaining 379 patients, data were collected on sex, laterality, history of trauma, plantar plate tear, age, and interspace location. Special focus was given to second and third interspace Morton's neuromas. Data were evaluated using the Pearson χ2 and independent-samples Mann-Whitney U tests, with P < .05 indicating statistical significance.

RESULTS

No statistically significant distribution between sex and second and third interspace Morton's neuromas was noted. Right vs left foot, age, and history of trauma did not vary statistically significantly between sexes. There was a statistically significant difference between the presence of plantar plate tears between sexes. Male patients with Morton's neuromas were found to have a higher rate of plantar plate tears (P = .01).

CONCLUSIONS

This study found that there were no statistically significant differences between sexes and Morton's neuromas location, laterality, or age.

MRI-Guided Interventions in Musculoskeletal System

Image-guided interventions in the musculoskeletal system require accurate detection and characterization of lesions involving bone and soft tissues. Magnetic resonance imaging (MRI) has superior soft tissue contrast resolution particularly in bone and soft tissues where computed tomography and ultrasonography have significant limitations. In addition, the multiplanar imaging capabilities of MRI facilitate targeting lesions and tracking interventional devices. Although conventional diagnostic MRI sequences suffer from motion sensitivity and prolonged imaging time, recently developed fast imaging sequences allow for rapid acquisition of high-quality images, rendering MRI more suitable for image-guided interventions. Although computed tomography and ultrasonography still dominate the spectrum of image-guided interventions in the musculoskeletal system, many MRI-guided procedures have been developed and are well established in routine clinical work. In addition, new techniques and novel MRI-guided applications are being developed to address complex clinical problems in a minimally invasive fashion.

Morton's interdigital neuroma of the foot: A literature review

Morton's neuroma is one of the most common causes of metatarsalgia. Despite this, it remains little studied, as the diagnosis is clinical with no reliable instrumental diagnostics, and each study may deal with incorrect diagnosis or inappropriate treatment, which are difficult to verify. The present literature review crosses all key points, from diagnosis to surgical and nonoperative treatment, and recurrences. Nonoperative treatment is successful in a limited percentage of cases, but it can be adequate in those who want to delay or avoid surgery. Dorsal or plantar approaches were described for surgical treatment, both with strengths and weaknesses that will be scanned. Failures are related to wrong diagnosis, wrong interspace, failure to divide the transverse metatarsal ligament, too distal resection of common plantar digital nerve, an association of tarsal tunnel syndrome and incomplete removal. A deep knowledge of the causes and presentation of failures is needed to surgically face recurrences.

Ultrasound-Guided Percutaneous Radiofrequency for the Treatment of Morton's Neuroma

PURPOSE

Morton's neuroma (MN) is a leading cause of disability. The purpose of this study was to investigate the effectiveness of radiofrequency (RF) in patients with chronic pain refractory to conservative therapies.

METHODS

Between September 2012 and December 2016, RF was performed on 52 patients. A sterile RF needle probe (22G, 5-cm needle with 10-mm electrode active tip) was inserted between the toes into the intermetatarsal space at the center of the lesion. Potential complications of the intervention and post-procedure care were examined. All patients provided written, informed consent. All percutaneous procedures were performed with the NeuroTherm^® NT1100 (Neurotherm Inc., M.) device and using ultrasound guidance (Philips IU22). Continuous RF was performed with one cycle of 90 s and with the probe tip maintaining a temperature of 85 °C (impedance 95-210 mΩ).

RESULTS

Mean VAS score before the procedures was 9.0 ± 0.6. A reduction of pain intensity was achieved after 1 week by RF (mean VAS scores 3.7 ± 0.9; p < 0.05), with a stabilization of the painful symptomatology in the following months and after 1 year of treatments (mean VAS scores 2.0 ± 0.4 after 12 months, p < 0.05). The FHSQ scores showed improved quality of life (QOL) in all patients at 6 months (p < 0.05) and 1 year (p < 0.05) of RF. No patients developed complications.

CONCLUSIONS

RF is a safe, efficient, and minimally invasive technique for the treatment of symptomatic MN.

Intraoperative Ultrasound for Peripheral Nerve Applications

Offering real-time, high-resolution images via intraoperative ultrasound is advantageous for a variety of peripheral nerve applications. To highlight the advantages of ultrasound, its extraoperative uses are reviewed. The current intraoperative uses, including nerve localization, real-time evaluation of peripheral nerve tumors, and implantation of leads for peripheral nerve stimulation, are reviewed. Although intraoperative peripheral nerve localization has been performed previously using guide wires and surgical dyes, the authors' approach using ultrasound-guided instrument clamps helps guide surgical dissection to the target nerve, which could lead to more timely operations and shorter incisions.

Corticosteroid Injection for the Treatment of Morton's Neuroma: A Prospective, Double-Blinded, Randomized, Placebo-Controlled Trial

BACKGROUND

The effectiveness of corticosteroid injection for the treatment of Morton's neuroma is unclear. In addition, most of the studies related to it are case-control or retrospective case series. The purpose of this study was to compare the effectiveness between corticosteroid injection associated with local anesthetic and local anesthetic alone (placebo control group) for the treatment of Morton's neuroma.

METHODS

Forty-one patients with a diagnosis of Morton's neuroma were randomized to receive 3 injections of either a corticosteroid plus a local anesthetic or a local anesthetic alone. The patients and the researcher who collected data were blinded to the treatment groups. The visual analog scale for pain and the American Orthopaedic Foot & Ankle Score (metatarsophalangeal/interphalangeal score) were obtained at baseline, after each injection, and at 3 and 6 months after the last injection.

RESULTS

There were no significant between-group differences in terms of pain and function improvement at 3 and 6 months after treatment completion in comparison with baseline values. At the end of the study, 17 (48.5%) patients requested surgical excision of the neuroma: 7 (44%) in the experimental group and 10 (53%) in the control group ( P = 1.0).

CONCLUSION

The injection of a corticosteroid plus a local anesthetic was not superior to a local anesthetic alone in terms of pain and function improvement in patients with Morton's neuroma.

LEVEL OF EVIDENCE

Level I, randomized controlled trial.

Sonography of Morton Neuromas: What Are We Really Looking At?

OBJECTIVES

To determine what accounts for the sonographic appearance of a Morton neuroma by correlating preoperative sonograms with the sonographic appearance of the resected surgical specimen, the surgical findings, and the pathologic examination.

METHODS

Ten Morton neuromas that had preoperative sonograms underwent postoperative specimen sonography and histologic evaluation. The appearance and size of the neuromas were compared between the preoperative and postoperative specimen images and were compared to the surgical and pathologic appearances.

RESULTS

Preoperative images showed a fibrillar echogenic nerve coursing into a heterogeneous hypoechoic mass measuring 14.3 mm in average length (range, 9.0-24.0 mm) that contained a round, mildly echogenic mass within it measuring 7.6 mm in average length (range, 4.5-12.0 mm). Surgically, the specimens showed scarred intermetatarsal bursas and tangled vessels surrounding the nerve. Specimen sonography showed echogenic focal enlargement of the nerve at the site of the neuroma, measuring 6.8 mm in average length (range, 3.5-11.0 mm). The size of the resected neuroma was smaller than the hypoechoic mass on the presurgical images (P < .001). Within the hypoechoic mass, the small echogenic focus showed no difference in size compared to the specimen (P = .40), but the shape of the echogenic specimen was fusiform, whereas the preoperative appearance was round. Histologically, the resected specimens showed sclerosis and mucoid degeneration of the nerve fascicles and fibrotic thickening of the perineurium.

CONCLUSIONS

The hypoechoic heterogeneous mass that is referred to as a Morton neuroma sonographically is really a "neuroma-bursal complex" that is much larger than the actual neuroma itself.

Sonography of Common Peripheral Nerve Disorders With Clinical Correlation

Sonography is now considered an effective method to evaluate peripheral nerves. Low cost, high resolution, the ability to image an entire limb in a short time, and dynamic assessment are several of the positive attributes of sonography. This article will review the normal appearance of peripheral nerves as shown with sonography. In addition, the most common applications for sonography of the peripheral nerves will be reviewed, which include entrapment neuropathies, intraneural ganglion cyst, nerve trauma, and peripheral nerve sheath tumors. Clinical information related to nerve disorders is also included, as it provides valuable information that can be obtained during sonographic examinations, increasing diagnostic accuracy.

Diagnostic Value of Elastography in the Diagnosis of Intermetatarsal Neuroma

The objective of the present study was to characterize the ultrasound and elastographic properties of intermetatarsal neuroma (interdigital neuroma) and their contribution to diagnosis. Eighteen patients with metatarsalgia, who had presented to an orthopedic clinic from April 2013 to February 2015, were diagnosed with 25 intermetatarsal neuromas (11 unilateral [61.11%], 7 bilateral [38.89%]). These patients underwent evaluation with ultrasonography and simultaneous ultrasound strain elastography to assess the elastographic properties of the tissues in the intermetatarsal space. The intermetatarsal neuroma diagnosis was confirmed by histopathologic inspection. The lesion contours, localization, dimensions, and vascularization were evaluated before surgical excision. The elasticity and strain ratio values were compared between the neuroma and adjacent healthy intermetatarsal space. Of the 25 intermetatarsal neuromas, 1 (4%) was not detected by ultrasonography (incidence of detection of 96%). The mean neuroma width was 6.35 (range 3.7 to 13) mm in the coronal plane, and the mean elasticity and strain ratio values were 3.44 (range 1.1 to 5.1) and 9.47 (range 2.3 to 19.3), respectively. The elasticity and strain ratio values were significantly greater in the presence of an interdigital neuroma than in the adjacent healthy intermetatarsal spaces (Z = -3.964, p = .0001 and Z = -3.927, p = .0001, respectively). The diagnostic cutoff values were calculated as 2.52 for elasticity and 6.1 for the strain ratio. Four neuromas (16%) were not demarcated, and the elasticity and strain ratio values for these were lower than those for neuromas with demarcated contours but were greater than those for healthy intermetatarsal spaces (p < .006 and p < .005, respectively). Patients with clinically suspected intermetatarsal neuromas that do not show demarcation and with smaller lesions might benefit from the use of ultrasound elastography for diagnosis.

Extracorporeal Shockwave Therapy in Patients with Morton's Neuroma A Randomized, Placebo-Controlled Trial

BACKGROUND

The aim of this study was to evaluate the efficacy of extracorporeal shockwave therapy (ESWT) for the treatment of Morton's neuroma by measuring changes in patient pain, function, and neuroma size.

METHODS

Patients with Morton's neuroma were randomly assigned to either the ESWT group or the sham stimulation group. Outcome measures, including visual analog scale (VAS) and American Orthopaedic Foot and Ankle Society lesser toes (AOFAS) scores, were assessed at baseline and 1 and 4 weeks after treatment. The Johnson satisfaction test was also performed 1 and 4 weeks after treatment. The neuroma diameter was measured using ultrasonography at baseline and 4 weeks after treatment.

RESULTS

Patients receiving ESWT exhibited significantly decreased VAS scores 1 and 4 weeks after treatment relative to baseline, and AOFAS scores were significantly improved 4 weeks after treatment relative to baseline. In the sham stimulation group, VAS and AOFAS scores showed no significant changes at any time after treatment. Neither group showed significant changes in Johnson satisfaction test results or neuroma diameter.

CONCLUSIONS

These results suggest that ESWT may reduce pain in patients with Morton's neuroma.

The accuracy of diagnostic ultrasound imaging for musculoskeletal soft tissue pathology of the extremities: a comprehensive review of the literature

Musculoskeletal diagnostic ultrasound imaging (MSK-DUSI) has been growing outside the traditional radiology speciality. Increased use of this technology has been reported in several healthcare settings, however an apparent gap in the knowledge of the accuracy of this diagnostic technology indicated a review was warranted. We undertook a structured review of the literature to assess the accuracy of MSK-DUSI for the diagnosis of musculoskeletal soft tissue pathology of the extremities. An electronic search of the National Library of Medicine’s PubMed database (1972 to mid-2014) was conducted. All relevant systematic reviews of diagnostic studies, all diagnostic studies published after the date of the latest systematic reviews and relevant diagnostic studies outside the scope the systematic reviews that directly compared the accuracy of MSK-DUSI (the index test) to an appropriate reference standard for the target condition were included. A fundamental appraisal of the methodological quality of studies was completed. The individual sensitivity, specificity and likelihood ratio data were extracted and entered into diagnostic accuracy tables. A total of 207 individual studies were included. The results show that MSK-DUSI has acceptable diagnostic accuracy for a wide spectrum of musculoskeletal conditions of the extremities. However, there is a lack of high quality prospective experimental studies in this area and as such clinicians should interpret the results with some caution due to the potential for overestimation of diagnostic accuracy.

The role of fasciae in Civinini-Morton's syndrome

This study evaluates the pathogenetic role of the perineural connective tissue and foot fasciae in Civinini-Morton's neuroma. Eleven feet (seven male, four female; mean age: 70.9 years) were dissected to analyse the anatomy of inter-metatarsal space, particularly the dorsal and plantar fasciae and metatarsal transverse ligament (DMTL). The macrosections were prepared for microscopic analysis. Ten Civinini-Morton neuromas obtained from surgery were also analysed. Magnetic resonance images (MRIs) from 40 patients and 29 controls were compared. Dissections showed that the width of the inter-metatarsal space is established by two fibrous structures: the dorsal foot fascia and the DMTL, which, together, connect the metatarsal bones and resist their splaying. Interosseous muscles spread out into the dorsal fascia of the foot, defining its basal tension. The common digital plantar nerve (CDPN) is encased in concentric layers of fibrous and loose connective tissue, continuous with the vascular sheath and deep foot fascia. Outside this sheath, fibroelastic septa, from DMTL to plantar fascia, and little fat lobules are present, further protecting the nerve against compressive stress. The MRI study revealed high inter-individual variability in the forefoot structures, although only the thickness of the dorsal fascia represented a statistically significant difference between cases and controls. It was hypothesized that alterations in foot support and altered biomechanics act on the interosseous muscles, increasing the stiffness of the dorsal fascia, particularly at the points where these muscles are inserted. Chronic rigidity of this fascia increases the stiffness of the inter-metatarsal space, leading to entrapment of the CDPN.

Ultrasound versus magnetic resonance imaging for Morton neuroma: systematic review and meta-analysis

OBJECTIVES

To compare ultrasound (US) and magnetic resonance imaging (MRI) in the diagnosis of Morton's neuroma.

METHODS

Studies that assessed the diagnostic accuracy of US and MRI for Morton's neuroma were retrieved from major medical libraries independently by two reviewers up to 1 April 2014. Predefined inclusion and exclusion criteria were adopted.

RESULTS

277 studies were initially found, and the meta-analysis was conducted on 14 studies. US sensitivity was studied in five studies, MRI sensitivity in three studies, and bothin six studies. All studies used surgery as the reference standard. A high sensitivity (SE) of diagnostic testing was observed for both US (SE (95 % CI) = 0.91 (0.83-0.96)) and MRI (SE (95 % CI) = 0.90 (0.82-0.96)) with no significant differences between the two modalities in diagnosis (Q test p = 0.88). For MRI, specificity of test was 1.00 with a pooled estimation of 1.00 (0.73-1.00), while the pooled specificity was 0.854 (95 % CI: 0.41-1.00) for US. No differences were observed between US and MRI in study design (p = 0.76).

CONCLUSION

This meta-analysis shows that the SE of US (0.91) is equal to (p = 0.88) that of MRI (0.90) for identification of Morton's neuroma.

KEY POINTS

• For Morton's neuroma, US sensitivity is equal to MRI. • US is as accurate as MRI in diagnosing Morton's neuroma. • US may be the most cost-effective imaging method for Morton's neuroma.

Role of MRI in detection of Morton's neuroma

BACKGROUND

Distinguishing between patients with a true Morton's neuroma and other forefoot pathology can be difficult. The aim of this study was to evaluate the diagnostic accuracy of routine magnetic resonance imaging (MRI) when compared to clinical examination for Morton's neuroma.

METHODS

We retrospectively identified 71 patients who underwent operative treatment due to the diagnosis of Morton's neuroma between 2007 and 2013. All patients had a MRI preoperative. Our study group comprised 58 female and 13 male patients with a mean age of 57 (range, 38-92) years. We compared the results of preoperative MRI and the patient's clinical assessment with postoperative histopathological results.

RESULTS

Typical clinical signs were found in 65 cases. Most common symptoms were plantar pain (92%) and increased pain on walking (89%). A Morton's neuroma was detected on MRI in 59 of 71 cases. Its sensitivity was 0.84 and its specificity was 0.33. The positive and negative predictive values were 0.97 and 0.08, respectively. For the presence of main clinical symptoms we found a sensitivity of 0.94 and a specificity of 0.33. The positive predictive value was 0.97 and the negative predictive value was 0.20.

CONCLUSION

MRI under routine conditions had a good detection rate for the evaluation of Morton's neuroma. However, its accuracy was not as high as the accuracy of clinical assessment.

LEVEL OF EVIDENCE

Level IV, retrospective series.

Contribution of a new electrophysiologic test to Morton's neuroma diagnosis

BACKGROUND

Morton's neuroma causes metatarsalgia due to the interdigital neuropathy. The small nerve diameter compromises their evaluation in image studies. To overcome this problem we propose a new electrophysiological test.

METHODS

We conducted a prospective case-control study performing a orthodromic electroneurography using subdermal electrodes in controls and patients to assess the validity. Additionally all patients were tested with magnetic resonance. Some patients required surgery and subsequent histological evaluation.

RESULTS

The new ENG procedure showed higher sensitivity and specificity. Methodological standardization was easy and the test was well tolerated by the subjects.

CONCLUSIONS

Our test demonstrated remarkable diagnostic efficiency, and also was able to identify symptomatic patients undetected by magnetic resonance, which underlines the lack of correlation between the size and intensity of the lesion. This new electrophysiological method appears to be a highly sensitivity, well-tolerated, simple and low-cost for Morton's neuroma diagnosis.

Treatment of Morton neuroma with botulinum toxin A: a pilot study

BACKGROUND AND OBJECTIVE

Morton neuroma is a common cause of metatarsalgia of neuropathic origin. Systematic reviews suggest that insufficient studies have been performed on the efficacy of the different treatments available. OnabotulinumtoxinA has shown a degree of usefulness in other conditions associated with neuropathic pain. The aim of this study was to investigate the therapeutic potential of onabotulinumtoxinA in Morton neuroma.

PATIENTS AND METHODS

We present an open-label, pilot study with 17 consecutive patients with Morton neuroma and pain of more than 3 months' duration that had not responded to conservative treatment with physical measures or corticosteroid injection. Patients received one onabotulinumtoxinA injection in the area of the neuroma. The main outcome measure was the variation in the pain on walking evaluated using a visual analogue scale (VAS) before treatment and at 1 and 3 months after treatment. The secondary outcome was the change in foot function, which was assessed using the Foot Health Status Questionnaire.

RESULTS

In the overall group, the mean initial VAS score on walking was 7. This mean score had fallen to 4.8 at 1 month after treatment and to 3.7 at 3 months. Twelve patients (70.6 %) reported an improvement in their pain and five patients (29.4 %) reported no change; exacerbation of the pain did not occur in any patient. Improvements were also observed in two of the dimensions of the Foot Health Status Questionnaire: foot pain, which improved from a mean of 38.88 before treatment to 57 at 3 months, and foot function, which improved from a mean of 42.27 before treatment to 59.9 at 3 months. Clinical variables including age, sex, site and size of the lesion, standing activity, weekly duration of walking, footwear, foot type and footprint had no influence on the outcome. No adverse effects were reported.

CONCLUSIONS

In this pilot study, injection with onabotulinumtoxinA was shown to be of possible usefulness to relieve the pain and improve function in Morton neuroma. This finding opens the door to further clinical research.

Imaging of the peripheral nervous system

This chapter summarizes progress in the evaluation of peripheral nerve (PN) lesions and disorders by imaging techniques encompassing magnetic resonance imaging (MRI) and nerve ultrasound (US). Due to the radiation exposure and limited sensitivity in soft tissue contrast, computed-tomography (CT) plays no significant role in the diagnostic work-up of PN disorders. MRI and US are complementary techniques for the evaluation of peripheral nerves, each having particular advantages and disadvantages. Nerve injury induces intrinsic MRI signal alterations on T2-weighted sequences in degenerating or demyelinating nerve segments as well as in corresponding muscle groups exhibiting denervation which can be exploited diagnostically. Nerve US is based on changes in the nerve echotexture due to tumor formation or focal enlargement caused by entrapment or inflammation. Both MRI and US provide morphological information on the precise site and extent of nerve injury. While US has the advantage of easy accessibility, providing images with superior spatial resolution at low cost, MRI shows better soft tissue contrast and better image quality for deep-lying nerve structures since imaging is not hindered by bone. Recent advances have remarkably increased spatial resolution of both MRI and US making imaging indispensible for the elucidation of causes of nerve compression, peripheral nerve tumors, and focal inflammatory conditions. Both MRI and US further guide neurosurgical exploration and can simplify treatment. Importantly, imaging can reveal treatable conditions even in the absence of gross electrophysiological alterations, illustrating its increasing role in clinical practice. In experimental settings, novel molecular and cellular MRI contrast agents allow in-vivo assessment of nerve regeneration as well as monitoring of neuroinflammation. Depending on further clinical development, contrast-enhanced MRI has the potential to follow cellular responses over time in vivo and to overcome the current limitations of histological assessment of nerve afflictions. Further advances in contrast-enhanced US has the potential for developing into a tool for the assessment of nerve blood perfusion, paving the way for better assessments of ischemic neuropathies.

Ultrasonography and magnetic resonance imaging in the diagnosis of Morton's neuroma

BACKGROUND

Magnetic resonance imaging (MRI) and ultrasonography are used widely for the diagnosis of Morton's neuroma. The aim of this study was to assess the accuracy of these two modalities as diagnostic tools in Morton's neuroma.

METHODS

Fifty feet of 47 consecutive patients (39 women and 8 men; mean age, 46 years; age range, 36-64 years) who presented between January 1, 2005, and June 30, 2008, were included in the study. Twenty-five feet were investigated with ultrasonography and 25 with MRI. Morton's neuroma was confirmed surgically and histologically in all of the patients. A Student unpaired t test was applied.

RESULTS

Twenty-two MRIs were diagnostic (sensitivity, 88%). Three patients with negative MRI findings underwent ultrasonography and were found to have a neuroma smaller than 5 mm. Twenty-four ultrasound scans demonstrated the neuroma (sensitivity, 96%), with five neuromas being smaller than 5 mm.

CONCLUSIONS

Ultrasonography has a slightly higher sensitivity in the diagnosis of Morton's neuroma, particularly of neuromas smaller than 5 mm, and should be the preferred imaging modality in suspected cases, and MRI should be reserved for cases with equivocal diagnosis.

Prevalence of interdigital nerve enlargements in an asymptomatic population

BACKGROUND

Morton's neuroma is a common primary diagnosis for referral to foot and ankle surgeons. On presentation, many patients have had an ultrasound reporting the presence of Morton's neuroma, which may not correlate with the clinical examination findings. The prevalence of such sonographic findings in the general population remains unknown.

METHODS

In this observational prospective study, patients with asymptomatic forefeet who were seen by two foot and ankle surgeons for unrelated mid- or hind foot pathology were examined clinically and sonographically for the presence of interdigital nerve thickening. Forty-eight volunteers participated in the study (96 feet). For the purpose of this study, asymptomatic thickenings greater than 5 mm in diameter were termed sonographic neuromas. Ultrasound examination was performed by two specialist musculoskeletal radiologists.

RESULTS

Fifty-four percent of the volunteers (26 of 48) had sonographic nerve thickening and in 17 cases (35.4%) enlarged nerves were found bilaterally. Differences for gender, original diagnosis or side of original pathology were not significant. Older subjects were more likely to have a sonographic neuroma (p = 0.018). Feet with a positive Mulder's click were more likely to have a sonographic neuroma (p = 0.015).

CONCLUSION

Ultrasound, even in highly skilled hands, has a high rate of incidental finding of an asymptomatic interdigital nerve enlargement, which can lead to a false diagnosis of a Morton's neuroma. Sonographic evidence of Morton's neuroma per se is unreliable unless it is correlated with an equivocal clinical examination. Clinical examination is still the gold standard for the diagnosis of a Morton's neuroma.

MRI and ultrasonography in Morton's neuroma: Diagnostic accuracy and correlation

BACKGROUND

The diagnosis of Morton's neuroma is based primarily on clinical findings. Ultrasonography (US) and magnetic resonance image (MRI) studies are considered complementary diagnostic techniques. The aim of this study was to establish the correlation and sensitivity of both techniques used to diagnose Morton's neuroma.

MATERIALS AND METHODS

Thirty seven patients (43 intermetatarsal spaces) with Morton's neuroma operated were retrospectively reviewed. In all cases MRI or ultrasound was performed to complement clinical diagnosis of Morton's neuroma. In all cases, a histopathological examination confirmed the diagnosis. Estimates of sensitivity were made and correlation (kappa statistics) was assessed for both techniques.

RESULTS

Twenty seven women and 10 men participated with a mean age of 60 years. Double lesions presented in six patients. The second intermetatarsal space was affected in 10 patients and the third in 33 patients. An MRI was performed in 41 cases and a US in 23 cases. In 21 patients, both an MRI and a US were performed. With regard to the 41 MRIs performed, 34 were positive for Morton's neuroma and 7 were negative. MRI sensitivity was 82.9% [95% confidence interval (CI): 0.679-0.929]. Thirteen out of 23 US performed were positive and 10 US were negative. US sensitivity was 56.5% (95% CI: 0.345-0.768). Relative to the 21 patients on whom both techniques were carried out, the agreement between both techniques was poor (kappa statistics 0.31).

CONCLUSION

Although ancillary studies may be required to confirm the clinical diagnosis in some cases, they are probably not necessary for the diagnosis of Morton's neuroma. MRI had a higher sensitivity than US and should be considered the technique of choice in those cases. However, a negative result does not exclude the diagnosis (false negative 17%).

Sonographic appearances of Morton's neuroma: differences from other interdigital soft tissue masses

The purpose of the study was to evaluate the ultrasonographic characteristics of Morton's neuroma (MNs) and the usefulness of the "ginkgo leaf sign" for differentiating MNs from other interdigital soft tissue masses. The inclusion criteria were 27 patients with the masses in the intertarsal region with surgical proof. Fourteen masses in the 10 patients (mean age, 46) were MNs and nine cases of nine patients were ganglion cysts, seven cases (seven patients) of epidermoid tumors and one case of fibroma were included. Ultrasonographic examinations were performed by a musculoskeletal radiologist using the HDI 5000 (Philips, Bothell, WA, USA) or the Logiq E9 (GE Medical Systems, Milwaukee, WI, USA) equipped with a linear 6-15 MHz probe, and the findings were interpreted in consensus by two musculoskeletal radiologists. The ultrasonographic findings such as margin, size, echogenicity and deepness of the MNs were compared with those for other interdigital soft tissue masses. The ginkgo leaf sign was defined as the appearance of a biconcave shape of the mass from compression by adjacent structures. The mean size of the MNs was 5.6 mm. There was a significant difference in incidence between males and females (female dominant, p = 0.003). There was no difference in incidence with regard to age (p = 0.259). All lesions were hypoechoic (100%, 14/14) and 10 cases exhibited the ginkgo leaf sign (71%, 10/14, p < 0.001). The lesions were either well marginated (43%, 6/14) or poorly marginated (57%, 8/14, p = 0.075). None of the lesions abutted adjacent bony structures (p < 0.001). Interdigital MNs are primarily found in middle-aged women and often demonstrate the ginkgo leaf sign. MNs are hypoechoic and do not abut adjacent bony structures. Based on our findings, we believe ultrasound of interdigital soft tissue masses may provide useful information with respect to their location to adjacent soft tissue structures. Detection of our Gingko leaf sign may be specific for Morton's neuromas and more studies are needed to confirm its value as a sonographic sign.

Morton neuroma: MR imaging after resection--postoperative MR and histologic findings in asymptomatic and symptomatic intermetatarsal spaces

PURPOSE

To evaluate the prevalence of postoperative magnetic resonance (MR) imaging findings in asymptomatic and symptomatic patients after resection of Morton neuroma.

MATERIALS AND METHODS

This study was approved by the institutional review board. Informed consent was obtained from each participant. Fifty-eight consecutive patients (46 women, 12 men) who had undergone resection of a painful Morton neuroma (90 Morton neuromas were removed in 66 feet), pre- and postoperative MR imaging, and clinical follow-up for a minimum of 2 years after surgery were identified. Two experienced musculoskeletal radiologists evaluated MR images with regard to the presence of presumed recurrent Morton neuroma, scar, or intermetatarsal bursitis. The prevalence of abnormalities in asymptomatic and symptomatic intermetatarsal spaces was determined. The results of the second radiologist were used only to determine interobserver reliability. The kappa statistics were obtained to assess interobserver agreement. Seven patients with presumed recurrent Morton neuroma underwent repeat surgery.

RESULTS

Clinically speaking, 68 intermetatarsal spaces (44 of 58 patients [76%], 47 feet) were asymptomatic at follow-up and 22 (14 of 58 patients [24%], 19 feet) were symptomatic. A presumed Morton neuroma was found in 18 (26%) of the asymptomatic spaces and 11 (50%) of the symptomatic spaces. A presumed scar was found in six (9%) of the asymptomatic spaces and two (9%) of the symptomatic spaces. A presumed intermetatarsal bursitis was found in six (9%) of the asymptomatic spaces and six (27%) of the symptomatic spaces. Interobserver agreement for presumed recurrent Morton neuroma was substantial (kappa = 0.64). Histologic examination of presumed recurrent Morton neuroma revealed fibrous tissue but no sign of peripheral neural tissue.

CONCLUSION

MR imaging after Morton neuroma resection commonly reveals Morton neuroma-like abnormalities in asymptomatic and symptomatic intermetatarsal spaces.

Musculoskeletal sonography of the normal foot

Traumatic, degenerative and rheumatological injuries of the foot are common and can be managed by an ever increasing number of treatments and surgical interventions. High-frequency sonography is inexpensive, portable and is unique in allowing true dynamic assessment of the ligamentous, muscular and tendinous structures. The ultrasound technique demonstrates a steep learning curve and requires detailed knowledge of the foot anatomy. Ultrasound assessment plays an important role in the diagnosis and management of injuries of these structures by guiding rehabilitation and surgical intervention without delay. However, intimate knowledge of the ultrasound appearances of the foot anatomy and normal variants is paramount to correctly identify pathological conditions. We describe the normal sonographic appearances of the foot musculoskeletal structures with MR correlation including joints and their ligaments, dorsal and plantar surfaces of the foot, and the arches of the foot and their supporting structures.

The outcome of Morton's neurectomy in the treatment of metatarsalgia

Morton's neuroma is a common cause of metatarsalgia caused by intermetarsal digital nerve thickening. This study reviews the pathology, presentation, symptoms and signs, and patient satisfaction with surgical treatment. Seventy-eight patients (82 feet) were treated for Morton's metatarsalgia by excision of the interdigital nerve. The patients were followed-up for a mean of 4.6 years (range 0.8-8.1 years) and scored using the Foot Functional Index and the American Orthopedic Foot Ankle Society scoring system. In 74 patients the Foot Functional Index was more than 85 (maximum score 100). Seventy-one patients scored more than 90 on the American Orthopedic Foot Ankle Society scoring system with two patients scoring 100 (maximum score). Postoperatively, 82% reported excellent or good results, 10% had a fair result with restriction of activities or pain and 8% had no improvement at all after surgery while 71% had restrictions with footwear.