Sonography of Plantar Plates in Cadavers: Correlation with MRI and Histology

Texture differences of microchambers and macrochambers in heel pads between the elderly with and without diabetes

OBJECTIVE

This study aims to use the texture analysis of ultrasound images to distinguish the features of microchambers (a superficial thinner layer) and macrochambers (a deep thicker layer) in heel pads between the elderly with and without diabetes, so as to preliminarily explore whether texture analysis can identify the potential injury characteristics of deep tissue under the influence of diabetes before the obvious injury signs can be detected in clinical management.

METHODS

Ultrasound images were obtained from the right heel (dominant leg) of eleven elderly people with diabetes (DM group) and eleven elderly people without diabetes (Non-DM group). The TekScan system was used to measure the peak plantar pressure (PPP) of each participant. Six gray-level co-occurrence matrix (GLCM) features including contrast, correlation, dissimilarity, energy, entropy, homogeneity were used to quantify texture changes in microchambers and macrochambers of heel pads.

RESULTS

Significant differences in GLCM features (correlation, energy and entropy) of macrochambers were found between the two groups, while no significant differences in all GLCM features of microchambers were found between the two groups. No significant differences in PPP and tissue thickness in the heel region were observed between the two groups.

CONCLUSIONS

In the elderly with diabetes who showed no significant differences in PPP and plantar tissue thickness compared to those without diabetes, several texture features of ultrasound images were found to be significantly different. Our finding indicates that texture features (correlation, energy and entropy) of macrochambers could be used for early detection of soft tissue damage associated with diabetes.

Ultrasonography-Based Quantitative Evaluation of Second Metatarsophalangeal Joint Instability in Female Patients With Hallux Valgus

BACKGROUND

Patients with moderate to severe hallux valgus (HV) sometimes exhibit second metatarsophalangeal (MTP) joint dislocation. Second MTP joint instability due to plantar plate (PP) injury has been suggested as one of the causes. However, there have been no reports that quantitatively evaluate this instability. This study aimed to evaluate second MTP joint instability in patients with HV without dislocation via ultrasonography and investigate its relationship with the presence of PP injury or foot form.

METHODS

Between May 2018 and July 2023, symptomatic female patients with HV without any lesser toe deformity were included in this study. Second MTP joint instability was defined as the dorsal displacement ratio (DDR) of the passively subluxated proximal phalangeal articular surface on the metatarsal head articular surface. The presence of PP injury was assessed using ultrasonography. Foot "form" was determined by measuring standard foot bony angles on weight-bearing foot-ankle radiographs. The relationship between DDR or PP injury and radiographic measurements was investigated.

RESULTS

Sixty-four patients (100 feet) were included. The average DDR of the second MTP joint in patients with HV without dislocation was 35.7%. There was an increase in the probability of PP injury, above a cutoff DDR value r of 35.4% (area under the curve = 0.712). The sensitivity, specificity, positive predictive value, and negative predictive value for the presence of PP injury based on this cutoff level were 63.9%, 74.4%, 79.6%, and 56.9%, respectively. Metatarsalgia was reported in 21 feet (21.0%), of which 15 feet (71.4%) showed PP injury. An increase in DDR was weakly associated with increased metatarsus adductus angle and decreased second metatarsal height.

CONCLUSION

In female patients with HV without second MTP dislocation, we found ultrasonographic evidence of second MTP plantar plate injury and joint instability to be a relatively common finding with a high prevalence in those with localized metatarsalgia.

LEVEL OF EVIDENCE

Level II, development of diagnostic criteria based on consecutive patients.

Particularities on Anatomy and Normal Postsurgical Appearances of the Ankle and Foot

The anatomy of the ankle and foot is complex, allowing for a wide range of functionality. The movements of the joints represent a complex dynamic interaction. A solid understanding of the characteristics and actions of the anatomic elements helps explain the mechanisms and patterns of injury. This article reviews the anatomy, with special focus on concepts that are the object of recent study and the features that favor the development of symptoms. Good understanding of the surgical procedures helps in providing information to guarantee a favorable outcome. We review the commonly expected postsurgical appearances and the most common postsurgical complications.

Presurgical Perspective and Postsurgical Evaluation of Plantar Plate and Turf Toe

Capsuloligamentous injury of the first metatarsophalangeal (MTP) joint (eponymously called "turf toe") mostly occurs in athletes and involves acute trauma, whereas tears of the lesser MTP joint plantar plate typically are an attritional-degenerative condition. This article reviews the anatomy, pathophysiology, mechanism and patterns of injury, grading and classification of injury, imaging appearances (pre- and postoperative), and management of first MTP joint capsuloligamentous injuries and lesser MTP joint plantar plate tears. These two distinct pathologies are discussed in separate sections.

Normal and Diseased Imaging: Ultrasound/MRI

The lesser metatarsophalangeal joint plantar plate and calcaneonavicular (spring) ligament are highly specialized soft tissue structures within the foot, consisting partly of fibrocartilage and capable of withstanding high compressive and tensile loads. Preoperative advanced imaging, in the form of point-of-care ultrasound and MRI, has become indispensable for surgeons hoping to confirm, quantify, and better localize injuries to these structures before surgery. This article describes the technical considerations of ultrasound and MRI and provides examples of the normal and abnormal appearances of these structures. The pros and cons of each imaging modality are also discussed.

High-Resolution Ultrasound of the Forefoot and Common Pathologies

Forefoot pain is common in clinical practice. Careful history taking and routine physical examination are initially performed for diagnosis, but imaging can confirm the clinical suspicion and play a key role in management. Ultrasound (US) can provide a visualization of the fine anatomy of the forefoot and is a useful method for evaluating various lesions causing forefoot pain. In this review, we provide the detailed anatomical structures of the forefoot and their normal appearances on US. We also focus on the most common pathologies affecting the forefoot, including plantar plate tear, sesamoiditis, bone fracture, synovitis, tenosynovitis, bursitis, Morton’s neuromas, and foreign bodies.

Imaging of Turf Toe

Turf toe is a common injury of the hallux metatarsophalangeal (MTP) joint in athletes which is the result of hyperdorsiflexion injury. While the term turf toe has been used to describe a variety of first MTP joint injuries, the term is now typically used in imaging to describe tearing or injury to the plantar plate complex. This review article will cover normal anatomy of the first MTP joint, mechanism of injury, typical imaging findings in normal individuals on MRI and ultrasound, as well as the most common patterns of injury.

Ultrasound findings of plantar plate tears of the lesser metatarsophalangeal joints

Lesser metatarsophalangeal (MTP) joint plantar plate tears are a common and increasingly recognised cause of metatarsalgia, MTP joint instability and forefoot deformity. Increased interest in early accurate diagnosis of plantar plate tears follows recent surgical innovations allowing direct plantar plate repair. The purpose of this review is to describe the ultrasound features of normal lesser MTP joint plantar plates and to characterise and illustrate the direct and indirect ultrasound findings of plantar plate tears. Lesser MTP joint plantar plate tears are most commonly located at the 2nd MTP joint, involving the lateral distal plantar plate insertion with variable propagation medially and proximally. The most common ultrasound appearance of a plantar plate tear is a discrete partial or full thickness hypoechoic defect in the plate substance. Flattening and attenuation or non-visualisation of the plantar plate represent more extensive tears. Dynamic imaging with toe dorsiflexion improves visualisation of tears and augments MTP joint subluxation. A common indirect finding is pericapsular fibrosis along the MTP joint capsule adjacent to a plantar plate tear, which requires differentiation from Morton's neuroma, and key distinguishing features at ultrasound are described. Other indirect findings include the cartilage interface sign, flexor tendon subluxation onto the metatarsal head or medial to the midline, flexor tenosynovitis, proximal phalangeal enthesophytes or avulsion and MTP joint synovitis. Ultrasound offers several advantages over MR imaging but requires a meticulous ultrasound examination, and optimisation of scanning technique is described.

Presence of Neovascularization in Torn Plantar Plates of the Lesser Metatarsophalangeal Joints

BACKGROUND

Recent surgical techniques have focused on anatomic repair of lesser toe metatarsophalangeal (MTP) plantar plate tears, yet it remains unknown whether the plantar plate has the biological capacity to heal these repairs. Therefore, a better understanding of the plantar plate vasculature in response to injury may provide further insight into the potential for healing after anatomic plantar plate repair. Recently, a study demonstrated that the microvasculature of the normal plantar plate is densest at the proximal and distal attachments. The purpose of this study was to compare the intact plantar plate microvasculature network to the microvasculature network of plantar plates in the presence of toe deformity using similar perfusion and nano-computed tomographic (CT) imaging methods.

METHODS

Seven fresh-frozen human cadaveric lower extremities with lesser toe deformities including hammertoe or crossover toe were perfused using a barium solution. The soft tissues of each foot were counterstained with phosphomolybdic acid (PMA). Then using nano-CT imaging, the second through fourth toe metatarsophalangeal joints of 7 feet were imaged. These images were then reconstructed, plantar plate tears were identified, and 11 toes remained. The plantar plate microvasculature for these 11 toes was analyzed, and calculation of vascular density along the plantar plate was performed. Using analysis of variance (ANOVA), this experimental group was compared to a control group of 35 toes from cadaveric feet without deformity and the vascular density compared between quartiles of plantar plate length proximal to distal. A power analysis was performed, determining that 11 experimental toes and 35 control toes would be adequate to provide 80% power with an alpha of 0.05.

RESULTS

Significantly greater vascular density (vascular volume/tissue volume) was found along the entire length of the plantar plate for the torn plantar plates compared to intact plantar plates (ANOVA, P < .001). For the first quartile of length (proximal to distal), the vascular density for the torn plantar plates was 0.365 (SD 0.058) compared to 0.281 (SD 0.036) for intact plantar plates; in the second quartile it was 0.300 (SD 0.044) vs 0.175 (SD 0.025); third quartile it was 0.326 (SD 0.051) vs 0.117 (SD 0.015); and fourth (most distal) quartile was 0.600 (SD 0.183) vs 0.319 (SD 0.082).

CONCLUSION

Torn plantar plates showed increased vascular density throughout the length of the plantar plate with an increase in density most notable in the region at or just proximal to the attachment to the proximal phalanx. Our analysis revealed that torn plantar plates exhibit neovascularization around the site of a plantar plate tear that does not exist in normal plantar plates.

CLINICAL RELEVANCE

The clinical significance of the increased vascularity of torn plantar plates is unknown at this time. However, the increase in vasculature may suggest that the plantar plate is a structure that is attempting to heal.

Magnetic Resonance Imaging Investigation of Cervical-Spine Meniscoid Composition: A Validation Study

OBJECTIVE

The composition of cervical-spine meniscoids may have clinical significance in neck-pain conditions, but the accuracy of assessment of meniscoid composition in vivo using magnetic resonance imaging has not been established. The aim of this study was to compare cervical-spine meniscoid composition by magnetic resonance imaging with histologic composition.

METHODS

Four embalmed cadaveric cervical spines (mean [standard deviation] age, 79.5 [3.7] years; 1 female, 3 male) underwent magnetic resonance imaging, allowing radiologic classification of lateral atlantoaxial- and zygapophyseal-joint (C2-3 to C6-7) meniscoids as either mostly fatty, mixed tissue, or mostly connective tissue. Subsequently, each joint was dissected and disarticulated to allow excision of meniscoids for histologic processing. Each meniscoid was sectioned sagittally, stained with hematoxylin and eosin, examined using light microscopy, and classified as adipose, fibroadipose, or fibrous in composition. Data were analyzed using the kappa statistic with linear weighting.

RESULTS

From dissection, 62 meniscoids were identified, excised, and processed; 46 of these 62 were visualized with magnetic resonance imaging. For single-rater identifying structures, agreement between assessment of meniscoid composition by magnetic resonance imaging and by microscopy was fair (κ = 0.24; 95% confidence interval, 0.02-0.46; P = .02).

CONCLUSION

Findings suggest that the accuracy of this method of magnetic resonance imaging assessment of cervical-spine meniscoid composition may be limited. This should be considered when planning or interpreting research investigating meniscoid composition using magnetic resonance imaging.

Microvasculature of the Plantar Plate Using Nano-Computed Tomography

BACKGROUND:

Lesser toe plantar plate attenuation or disruption is being increasingly implicated in a variety of common clinical conditions. A multitude of surgical techniques and devices have been recently developed to facilitate surgical repair of the plantar plate. However, the microvascular anatomy, and therefore the healing potential in large part, has not been defined. We investigated the microvasculature of the plantar plate by employing a novel technique involving microvascular perfusion and nano-computed tomography (nano-CT) imaging.

METHODS:

Twelve human adult cadaveric lower extremities were amputated distal to the knee. The anterior and posterior tibial arteries were perfused with a barium solution. The soft tissues of each foot were then counterstained with phosphomolybdic acid (PMA). The second through fourth toe metatarsophalangeal (MTP) joints of 12 feet were imaged with nano-CT at 14-micron resolution. Images were then reconstructed for analysis of the plantar plate microvasculature and calculation of the vascular density along the length of the plantar plate.

RESULTS:

A microvascular network extends from the surrounding soft tissues at the attachments of the plantar plate on both the metatarsal and proximal phalanx. The midsubstance of the plantar plate appears to be relatively hypovascular. Analysis of the vascular density along the length of the plantar plate demonstrated a consistent trend with increased vascular density at approximately the proximal 29% and distal 22% of the plantar plate.

CONCLUSION:

There is a vascular network extending from the surrounding soft tissues into the proximal and distal attachments of the plantar plate.

CLINICAL RELEVANCE:

The hypovascular midportion of the plantar plate may play an important role in the underlying pathoanatomy and pathophysiology of this area. These findings may have significant clinical implications for the reparative potential of this region and the surgical procedures currently described to accomplish anatomic plantar plate repair.

Quantitative magnetic resonance imaging assessment of lateral atlantoaxial joint meniscoid composition: a validation study

PURPOSE

Lateral atlantoaxial (LAA) joint meniscoid composition may have clinical significance in patients following neck trauma. However, the existing method of radiologically assessing meniscoid composition has an inherent element of subjectivity, which could contribute to measurement variability. The present study sought to investigate the accuracy of two-point Dixon fat/water separation MRI as a quantitative assessment of LAA joint meniscoid composition.

METHODS

Sixteen LAA joint meniscoids were excised from four cadavers (mean [SD] age 79.5 [3.7] years; one female) following cervical spine MRI (two-point Dixon, T1-weighted VIBE and T2-weighted SPACE sequences). Composition of LAA joint meniscoids was undertaken by (1) histological examination by light microscopy, (2) calculation of fat fraction by Dixon MRI (both in-phase/opposed-phase and fat/water methods), and (3) the existing method of considering VIBE and SPACE signal intensities. Analysis was performed using the kappa statistic with linear weighting.

RESULTS

Microscopy revealed three, five, and eight meniscoids to be composed of adipose, fibroadipose, and fibrous tissues, respectively. Dixon sequence MRI classified 11 of these meniscoids correctly, with 'substantial' level of agreement (In-phase/Opp-phase kappa statistic = 0.78 [95% CI 0.38, 1.17]; fat/water kappa statistic = 0.72 [95% CI 0.32, 1.11]). Level of agreement between microscopy and the VIBE and SPACE method was 'slight' (kappa statistic = 0.02 [95% CI - 0.34, 0.38]).

CONCLUSIONS

Findings suggest that Dixon fat/water separation MRI may have superior utility in the assessment of LAA joint meniscoid composition than the existing method of considering VIBE and SPACE signal intensities. These slides can be retrieved under Electronic Supplementary Material.

Lesser Metatarsophalangeal Joint Instability: Advancements in Plantar Plate Reconstruction

The plantar plate and associated collateral ligaments are the main stabilizers of each of the lesser metatarsophalangeal joints. Although clinical examination and plain radiographs are usually sufficient to establish the diagnosis of a plantar plate tear, MRI or fluoroscopic arthrograms may help in specific cases. Recent results with a dorsal approach to plantar plate repair are promising with respect to pain relief and patient satisfaction.

Accuracy of Sonography in Plantar Plate Tears in Cadavers

OBJECTIVES

Sonography is often used in the evaluation of forefoot disorders, and its use has been suggested in the diagnosis of plantar plate tears. This study aimed to assess the accuracy of sonography in the diagnosis of plantar plate tears of the lesser digits using gross dissection as the reference standard.

METHODS

The second through fifth digits of 6 cadavers were examined with sonography to evaluate for plantar plate tears. The examination was performed by a single musculoskeletal radiologist in longitudinal and short axes, and plates were graded as torn or intact. The digits were then dissected by a single podiatrist blinded to the prior sonographic results to assess the integrity of the plates.

RESULTS

Ten plantar plates were graded as torn by sonography, all occurring in the distal plate near the phalangeal insertion. Seven of these plates were identified as torn on direct inspection. Fourteen plantar plates were found to be intact on sonography, 12 of which were intact on gross inspection. Overall, the accuracy, sensitivity, and specificity of sonography were 79.2%, 77.8%, and 80.0%, respectively. No correlation was seen between the accuracy of sonography and plate size, using plate number as a surrogate marker for plate size (P = .822).

CONCLUSIONS

Sonography is an appropriate modality in the setting of suspected plantar plate tears, with acceptable accuracy, sensitivity, and specificity. No decline in accuracy was seen with smaller plates. Thus, sonography may be especially useful when small anatomy or technical factors make magnetic resonance imaging challenging to perform and interpret.

Comparing Magnetic Resonance Imaging and High-Resolution Dynamic Ultrasonography for Diagnosis of Plantar Plate Pathology: A Case Series

Plantar plate pathology has gained noticeable attention in recent years as an etiology of lesser metatarsophalangeal joint pain. The heightened clinical awareness has led to the need for more effective diagnostic imaging accuracy. Numerous reports have established the accuracy of both magnetic resonance imaging and ultrasonography for the diagnosis of plantar plate pathology. However, no conclusions have been made regarding which is the superior imaging modality. The present study reports a case series directly comparing high-resolution dynamic ultrasonography and magnetic resonance imaging. A multicenter retrospective comparison of magnetic resonance imaging versus high-resolution dynamic ultrasonography to evaluate plantar plate pathology with surgical confirmation was conducted. The sensitivity, specificity, and positive and negative predictive values for magnetic resonance imaging were 60%, 100%, 100%, and 33%, respectively. The overall diagnostic accuracy compared with the intraoperative findings was 66%. The sensitivity, specificity, and positive and negative predictive values for high-resolution dynamic ultrasound imaging were 100%, 100%, 100%, and 100%, respectively. The overall diagnostic accuracy compared with the intraoperative findings was 100%. The p value using Fisher's exact test for magnetic resonance imaging and high-resolution dynamic ultrasonography was p = .45, a difference that was not statistically significant. High-resolution dynamic ultrasonography had greater accuracy than magnetic resonance imaging in diagnosing lesser metatarsophalangeal joint plantar plate pathology, although the difference was not statistically significant. The present case series suggests that high-resolution dynamic ultrasonography can be considered an equally accurate imaging modality for plantar plate pathology at a potential cost savings compared with magnetic resonance imaging. Therefore, high-resolution dynamic ultrasonography warrants further investigation in a prospective study.

Evaluation of lesser metatarsophalangeal joint plantar plate tears with contrast-enhanced and fat-suppressed MRI

OBJECTIVE

To present findings of plantar plate (PP) lesions from MRI with administration of gadolinium and to differentiate PP lesions from others causes of metatarsalgia.

MATERIALS AND METHODS

Two musculoskeletal radiologists reviewed 249 contrast-enhanced forefoot MRI scans from patients with metatarsalgia between June 2012 and June 2013. Evaluations focused on hyper-vascularized/fibrous tissue and other findings associated with PP tears.

RESULTS

Fifty-nine patients had PP tears, 59 % were female. Most of these patients, 48/59 (81.4 %), had a single metatarsophalangeal (MTP) PP lesion in one foot, although 7/59 patients had one lesion in each foot, 3/59 (5.1 %) had two in one foot, and 1/59 (1.7 %) had three lesions in one foot. The second MTP joint was the most common location for PP tears (n = 56), followed by the third (n = 12) and fourth (n = 3) MTP joints. Lateral (n = 33) and full thickness (n = 28) PP lesions were the most frequent, and central (n = 3) and lateral/central (n = 7) tears were less prevalent. Fifty (70.5 %) PP lesions showed pericapsular fibrosis in pre-contrast sequences, and 21 (29.5 %) were visible only after administration of gadolinium. All PP lesions had collateral ligament involvement. Others findings included interosseous tendon lesions (n = 29), interosseous tendon rupture (n = 29), synovitis (n = 49), flexor tenosynovitis (n = 28), crossover toe (n = 2), hammertoe (n = 1), intermetatarsal space (IS) neuromas (n = 11), and third IS neuromas (n = 12).

CONCLUSION

PP tears are a common cause of metatarsalgia, accounting for more than 20 % of cases in our sample. A substantial portion of the lesions (29.5 %) became visible only after the administration of gadolinium.

Can ultrasound of plantar plate have normal appearance with a positive drawer test?

OBJECTIVES

The aims of this study were (1) to evaluate the reliability of ultrasound (US) examination in the identification and measurement of the metatarsophalangeal plantar plate (MTP-PP) in asymptomatic subjects and (2) to establish the correlation of US findings with those of physical examination and magnetic resonance imaging (MRI), once it is an important tool in the evaluation of the instability syndrome of the second and third rays.

MATERIALS AND METHODS

US examinations of the second and third MTP-PPs were performed in eight asymptomatic volunteers, totaling 32 MTP joints, by three examiners with different levels of experience in musculoskeletal US. Plantar plate dimensions, integrity and echogenicity, the presence of ruptures, and confidence level in terms of structure identification were determined using conventional US. Vascular flow was assessed using power Doppler. US data were correlated with data from physical examination and MRI.

RESULTS

MTP-PPs were ultrasonographically identified in 100% of cases, always showing homogeneous hyperechoic features and no detectable vascular flow on power Doppler, with 100% certainty in identification for all examiners. There was excellent US inter-observer agreement for longitudinal measures of second and third toe MTP-PPs and for transverse measures of the second toe MTP-PP. The MTP drawer test was positive for grade 1 MTP instability in 34.4% of joints with normal US results. Transverse MTP-PP measures were significantly higher in individuals with positive MTP drawer test. US measures and characteristics of MPT-PPs were positively correlated with those of MRI.

CONCLUSIONS

US is efficient in identifying and measuring MPT-PPs and may complement physical examination. A grade 1 positive MTP drawer test may be found in asymptomatic individuals with normal MPT-PPs, as assessed by imaging.

Positive drawer test combined with radiographic deviation of the third metatarsophalangeal joint suggests high grade tear of the second metatarsophalangeal joint plantar plate

There is uncertainty regarding the most accurate and cost-effective method for diagnosing plantar plate injuries within the foot. The purpose of this study was to examine the combined value of using clinical and radiographic findings to diagnose high grade tears (> 50% disruption) within the second metatarsophalangeal (MTP) joint. Ninety-eight consecutive patients (117 feet) who underwent corrective surgery for plantar forefoot pain at a single foot and ankle specialty clinic were included in this retrospective analysis. All patients received a structured intraoperative assessment of the second MTP joint plantar plate by a single trained observer. Twenty-five clinical and plain film radiographic variables obtained prior to surgery were tested for their association with a high grade plantar plate tear using multiple logistic regression techniques. A positive drawer sign was the most informative individual test for differentiating high from low grade tears (odds ratio [OR] = 2.9; 95% confidence interval [CI], 0.92-9.5; sensitivity 91.5%; specificity 22%). Patients with longstanding forefoot symptoms (> 2 years) tended to be more likely to have low grade tears only (OR = 2.1; 95% CI, 0.98-4.5; sensitivity 61.7%; specificity 58.1%). Most radiographic measurements did little to distinguish high from low grade tears; however, the addition of ipsilateral third MTP joint transverse deviation angle showed a trend toward improving upon the diagnostic accuracy of strategies that used clinical findings alone (area under the curve [AUC] improved from 0.63 to 0.67; P = .11). A third MTP joint deviation angle greater than 15° in either direction combined with drawer testing and duration of symptoms achieved the highest specificities of any combination of variables examined in the study (specificities 82.4% [95% CI, 73.7%-91.1%] and 89.1 [95% CI, 82.1-96.3], respectively). The combination of a positive drawer test coupled with transverse deviation of the third MTP joint (> 15°) on plain films strongly suggests an underlying high grade plantar plate tear of the second MTP joint. However, this study highlights the need for using advanced imaging to distinguish between high and low grade tears in many instances (eg, positive drawer test and normal or near-normal alignment of the third MTP joint).

LEVEL OF EVIDENCE

Diagnostic, Level II.

MRI of lesser metatarsophalangeal joint plantar plate tears and associated adjacent interspace lesions

OBJECTIVE

To identify the variety of second and third intermetatarsal space (IS) lesions that may coexist with and without adjacent metatarsophalangeal joint (MTP) plantar plate (PP) tears.

MATERIALS AND METHODS

One hundred forefoot MRIs in 96 patients with metatarsalgia obtained between 30 September 2011 and 21 July 2012 using 1.5- or 3-T MRI were retrospectively reviewed in consensus by two MSK radiologists and one podiatrist (DPM). MRI was evaluated for second and third MTP PP tear and the presence/nature of second and third IS lesions. Second and third IS neuromas were measured in transverse (trans) dimension.

RESULTS

A total of 40 PP tears were identified: 36 at the second and 4 at the third MTP. Second MTP PP tear was identified in 33% of females and 40.5% of males. In the 63 female feet there were 21 second MTP PP tears, all of which also had second IS lesions: pericapsular fibrosis (16), bursitis (4), and ganglion (1). In the 37 male feet there were 15 second MTP PP tears, 14 of which had second IS lesions: pericapsular fibrosis (8), bursitis (5), and ganglion (1). There was no definite second IS neuroma adjacent to any second MTP PP tear. In females without PP tear, there were 24 second (3 mm trans average) and 43 third IS neuromas (4.1 mm trans average). In males without PP tear, there were 9 second (3.4 mm trans average) and 16 third IS neuromas (4.1 mm trans average).

CONCLUSIONS

MTP PP tears occurred in 40% of our cases, 90% of which occurred at the second MTP. Almost all coexisted with non-neuromatous second IS lesions.

Static Versus Dynamic Musculoskeletal Ultrasound for Detection of Plantar Plate Pathology

Musculoskeletal ultrasound (US) is a common modality used to examine plantar plate pathology. Comparison of the diagnostic accuracy of static versus dynamic ultrasound has not been previously published. The objective of this study was to prospectively compare the value of using preoperative static and dynamic ultrasound findings to diagnose plantar plate pathology using intraoperative inspection as the standard of reference. Patients attending a single foot and ankle specialty clinic from August 2012 to June 2013 with clinically suspected plantar plate pathology that was unresponsive to conservative care served as the study population. Static and dynamic ultrasound exams were performed by a single experienced rater and compared to intraoperative findings. The overall accuracy, sensitivity, specificity, positive predictive value and negative predictive value were determined for static and dynamic ultrasound exams. Thirty-six patients (45 lesser metatarsophalangeal joints) were included in this analysis. Of the 36 patients, 29 were females and 7 were males with average age of 57.9 ± 7.8 years (range, 38-73). There were 38 plantar plate tears (84.4%) noted on intraoperative examination. The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for the static US exam were 80.0%, 81.6%, 71.4%, 93.9%, and 41.7%, respectively. The same values for the dynamic US exam were 88.9%, 100%, 28.6%, 88.3%, and 100%, respectively. Static and dynamic ultrasound techniques are each highly sensitive methods for assessing plantar plate pathology. However, the sensitivity and accuracy of the exam is best when dynamic assessment of the plantar plate is employed. Caution should be used when relying solely on static images to diagnose subtle injuries in this area of the foot.

LEVELS OF EVIDENCE

Diagnostic Level II, Prospective.

Dorsal Approach for Plantar Plate Repair With Weil Osteotomy: Operative Technique

In recent years, the role of the plantar plate in lesser metatarsophalangeal joint stability has increasingly been recognized. Tearing or attenuation of the plantar plate often will result in crossover or hammertoe deformity with hyperextension of the MTP joint. Some patients are able to have resolution of painful symptoms with conservative treatment but for those that fail these measures, surgical fixation of the plantar plate is indicated. While, there have been some described techniques for direct repair of the plantar plate, we present a surgical technique through a dorsal approach with a Weil osteotomy which accomplishes great clinical correction of the plantar plate tear and associated toe deformity as well as relief of patient's pain. Additionally, we believe this technique is safe, efficient and reproducible.

LEVEL OF EVIDENCE

Level V, expert opinion.

The plantar plate of the first metatarsophalangeal joint: an anatomical study

The plantar plate of the first metatarsophalangeal (MP) joint is a critical structure of the forefoot that has been identified as a major stabilizer within the capsuloligamentous complex. Many studies have clarified and documented the anatomy of the lesser toe MP plantar plates, but few have looked closely at the anatomy of the first MP joint. Ten cadaveric specimens were examined to identify and document the objective anatomic relationship of the plantar plate, tibial sesamoid, and surrounding osseus structures. The average distance of the plantar plate distal insertion from the joint line into the proximal phalanx was 0.33 mm. The plantar plate was inserted into the metatarsal head on average 17.29 mm proximal from the joint line. The proximal aspect of the sesamoid was 18.55 mm proximal to the distal attachment of the plantar plate to the phalanx. The distal aspect of the sesamoid averaged 4.69 mm away from the distal attachment into the proximal phalanx. The footprint of the distal plate insertion was on average 6.33 mm in length in the sagittal plane. The authors hope that these objective data measures can aid in the understanding and subsequent surgical repair of this important forefoot structure.

Forefoot: a basic integrated imaging perspective for radiologists

Imaging of the forefoot is increasingly requested for patients with metatarsalgia. Awareness with specific anatomic arrangements exclusive for the forefoot and widely variable pathologic entities associated with metatarsalgia helps the radiologist to tailor a cost-effective imaging approach. This will enable reaching a specific diagnosis as much as possible with subsequent proper patient management. This pictorial review aims to provide basic understanding for the different imaging modalities used in studying the forefoot. After that, certain anatomic arrangements exclusive for the forefoot are discussed. The final section of this review describes the imaging findings of some common forefoot problems.

The rheumatoid forefoot

Rheumatoid arthritis (RA) manifests itself in a variety of ways, with its effect being seen in around 90 % of sufferers' feet. The foot has been found to be the most common reason for incapacity in patients with RA, with the forefoot the most common area. The foot is second, behind only the hand, as the most common place for manifestation of RA. Pain in the foot is commonly the most debilitating condition, which causes the patient to seek specialist help. As well as pain, foot deformities such as hallux valgus and claw toes are common complaints. These symptoms often arise as a result of continued walking on an unstable foot, leading to painful callosities and dislocation of the metatarsophalangeal joints. Other conditions, such as pannus formation and Morton's neuroma, can be related to RA. This review sets out what we believe to be a successful approach to the rheumatoid forefoot, which aims at the relief of pain and the preservation of ambulation. Key to a successful outcome is appropriate medical control with a multidisciplinary approach that enables close liaison between orthopaedic surgeons, orthotists, and rheumatologists. Combined clinics provide this multidisciplinary care. Those treating RA need to be aware of the high incidence of foot involvement and how early intervention may benefit the patient. The aim of this article is to present current evidence to enable people to develop a treatment algorithm for this condition.

Ultrasound imaging for diagnosis of plantar plate ruptures of the lesser metatarsophalangeal joints: a retrospective case series

Tears of the plantar plate can be a source of significant forefoot pain, leading to alterations of foot function and gait. The objective of the present retrospective study was to further determine the value of ultrasound imaging in diagnosing plantar plate tears after clinical evaluation through a comparison of the ultrasound and intraoperative examination findings. Eight patients were identified who had undergone surgical intervention for a painful lesser metatarsophalangeal joint after ultrasound examination to diagnose a plantar plate pathologic entity. The intraoperative examination findings were used to calculate the sensitivity, specificity, and positive and negative predictive values of ultrasound in the diagnosis of plantar plate tears. The sensitivity and specificity of the ultrasound examination was 1 and 0.6, respectively. The positive and negative predictive value was 0.6 and 1, respectively. An ultrasound examination in the diagnosis of lesser metatarsophalangeal joint plantar plate tears displayed comparable sensitivity in identifying the pathologic features when compared with magnetic resonance imaging, with considerably less financial cost for the examination.

Musculoskeletal ultrasound for preoperative imaging of the plantar plate: a prospective analysis

The purpose of this study was to prospectively compare preoperative findings on musculoskeletal ultrasound evaluation to observed intraoperative findings for patients undergoing surgical correction of plantar plate tears. Fifty consecutive patients with forefoot pain and a suspected unilateral plantar plate tear at the second metatarsophalangeal (MTP) joint were identified. The same examiner performed a 2-plane (longitudinal and transverse) musculoskeletal ultrasound on the painful second MTP joint. The contralateral second MTP joint was used for comparison. Longitudinal ultrasound images were graded as "torn" or "intact." Transverse ultrasound images were used to localize the suspected pathology. Results of the ultrasound were compared with observed intraoperative pathology. Forty-five plantar plate tears were identified intraoperatively. Longitudinal ultrasound images correctly identified 40 plantar plate tears. The longitudinal ultrasound had a sensitivity of 91.1%, a specificity of 25%, a positive predictive value of 91.1%, and a negative predictive value of 25%. Transverse ultrasound images identified 36 plantar plate tears correctly localizing only 19 tears. Musculoskeletal ultrasound has been widely used to identify and localize pathology in many soft tissue structures. Whereas the longitudinal ultrasound images were useful in identifying plantar plate tears, the same cannot be said about the ability to localize the tear on the transverse ultrasound images. Therefore, ultrasound may not be as good an imaging modality as magnetic resonance imaging for identification and localization of plantar plate pathology.

MRI evaluation of the MTP plantar plates compared with arthroscopic findings: a prospective study

BACKGROUND

Instability of the lesser metatarsophalangeal (MTP) joints has been widely reported and plantar plate insufficiency is a key part of this pathologic process. The diagnosis is made clinically but can be aided by imaging studies, particularly magnetic resonance imaging (MRI); however, the sensitivity and accuracy of this method compared to direct visualization of these lesions has not yet been established, nor has interobserver accuracy of MRI been assessed for evaluation of plantar plate pathology. In this study, our goals were to identify the accuracy of the MRI in describing plantar plate tears when compared to direct arthroscopic visualization using an anatomic grading system and to test the influence of an anatomic grading system in the accuracy of the MRI readings.

METHODS

We evaluated the clinical exam, MRI scans, and arthroscopic findings of 35 patients with lesser MTP instability.

RESULTS

Using an anatomic grading system, a distinct improvement in the radiological evaluation and interpretation occurred. Knowledge of the pattern of plantar plate tears by a radiologist enabled them to locate and describe the type of tears of the plantar plate on the MRI. The amount of training and the experience of the radiologist were also important factors in our study. The senior radiologists had much better levels of accuracy (Group A, 77.0%; Group B, 88.5%) than less experienced radiologists.

CONCLUSION

Prior knowledge of the pathophysiology and morphological types of lesions of the plantar plates was helpful for accurate identification and description of the tears by the radiologist.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Magnetic resonance imaging versus musculoskeletal ultrasound for identification and localization of plantar plate tears

PURPOSE

Plantar plate injuries have been identified as a cause of forefoot pain and deformity. Magnetic resonance imaging (MRI) and musculoskeletal ultrasound (US) have been suggested as appropriate imaging modalities for this pathology. A comparison of these two modalities utilizing intra-operatively pathology as the reference standard has not been published.

METHODOLOGY

51 feet of 42 consecutive patients presenting to clinic with forefoot pain and a suspected unilateral plantar plate tear at the 2nd metatarsophalangeal (MTP) joint were identified. A two plane (longitudinal and transverse) US was performed on the painful second MTP joint. Longitudinal ultrasound images were graded as 'torn' or 'intact'. Transverse ultrasound images were used to localize pathology. All ultrasound exams were performed by the same reconstructive foot & ankle fellow. A pre-operative MRI was performed on these patients and read by a Fellowship Trained Musculoskeletal Radiologist. The physicians reading US and the MRI were blinded to each other's findings.

RESULTS

All 51 feet were examined intra-operatively. 46 plantar plate tears were identified. The sensitivity, specificity, positive predictive value and negative value of MRI were 73.9%, 100%, 100%, 29.4% respectively while the same values for US were 91.5%, 25%, 91.5%, 25% respectively. MRI identified 4 collateral ligaments tears not identified on ultrasound. Discussion &

CONCLUSIONS

Both MRI and US are appropriate modalities for imaging of the plantar plate. While US is a highly sensitive exam, MRI is a more specific exam. Overall these results do not suggest that MR should be replaced by US in all cases.

LEVEL OF EVIDENCE

Diagnostic, Level I.

Role of collateral ligaments in metatarsophalangeal stability: a cadaver study

BACKGROUND

Lesser metatarsophalangeal joint (MTPJ) instability is a common complaint. The role each of the collateral structures play in maintaining joint stability is unknown.

METHODS

Twenty-six fresh-frozen cadaver lesser MTPJ's were tested for instability with the amount of force necessary to translate the joint 3 mm dorsally. Specimens were tested with 1) intact collateral ligaments, 2) transected accessory collateral or proper collateral ligaments (ACL or PCL), 3) repaired ACL or PCL, 4) transected ACL and PCL, 5) repaired ACL and PCL, and 6) transferred interosseous (IO) tendon. Student t-tests were performed to test for statistical significance (p value less than 0.05).

RESULTS

The mean force required for 3 mm of dorsal displacement was 25 ± 13 N (range, 11 to 52 N) in the 26 specimens. Transecting either the ACL alone or the ACL and PCL led to the most instability versus transecting the PCL alone. Repairing both ligaments improved stability. The IO tendon transfer was comparable to the direct repair of the PCL but was inferior to the direct repair of the ACL.

CONCLUSION

Both ACL and PCL have a stabilizing effect on the MTPJ. However, the ACL was more important since primary transection of the ACL led to more instability and additional transection of the PCL in an ACL deficient model did not lead to significantly more instability.

CLINICAL RELEVANCE

Direct repairs of both structures improved the stability of the joint but not back to normal. IO tendon transfer is a possible adjunct to collateral ligament repairs, but in itself is not sufficient to restore stability.

Diagnosis of plantar plate injury by magnetic resonance imaging with reference to intraoperative findings

The objective of the present study was to assess the utility of magnetic resonance imaging in evaluating injury to the plantar plate and to determine whether conventional low-field magnetic resonance imaging is a valid tool for diagnostic evaluation. Magnetic resonance imaging scans of 45 feet in 41 patients (38 females and 3 males, with an average age of 52.1 years) were prospectively evaluated to assess the integrity of the plantar plate ligament and compared with a reference standard of intraoperative findings. The concordance of tear severity observed on magnetic resonance imaging with the intraoperative findings was also assessed using a newly proposed grading scheme for plantar plate injuries. Intraoperatively, 41 plantar plate tears and 4 intact ligaments were found. The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value was 96%, 95%, 100%, 100%, and 67%, respectively. The clinical diagnosis of plantar plate injury was also highly accurate in our study population (41/45, 91%). Finally, we observed moderate concordance between the magnetic resonance imaging grade and surgical grade of plantar plate tear (28/45, 62%), with greater concordance occurring at higher grades. Our results have demonstrated that magnetic resonance imaging is an accurate and valid test for the diagnosing injuries of the plantar plate ligament. Given the high accuracy of the clinical findings, magnetic resonance imaging is most useful when the decision to operate will be sufficiently influenced by either a normal magnetic resonance imaging appearance of the plantar plate or the presence of a high-grade tear.

Lesser metatarsophalangeal joint instability: prospective evaluation and repair of plantar plate and capsular insufficiency

BACKGROUND

Anatomical dissection of the second metatarsophalangeal (MTP) joint suggests that the plantar plate is the major stabilizing structure of the joint due to its central location and multiple important attachments. Many surgical procedures have been recommended when conservative treatment has failed, but some have had limited clinical success. The aim of our prospective study was to show the results obtained in the treatment of a group of patients with plantar plate tears by direct repair through a dorsal approach combined with a Weil metatarsal osteotomy with a minimum followup of 12 months.

METHODS

We prospectively treated 28 patients (55 MTP joints) with lesser MTP joint instability, but only 22 patients (40 MTP joints) were treated by the direct repair of the plantar plate and were included in the study. All of them had initial complaints of acute forefoot pain with the subsequent development of deformity and instability of the MTP joints. All patients were evaluated clinically, radiographically, (plain radiographs and MRI exam), and by MTP joint arthroscopy. With this data, a direct correlation between the clinical staging and the anatomical grading for plantar plate dysfunction of each patient was determined

RESULTS

The plantar plate of the second MTP joint was the most commonly affected joint (63%), and Grade III type tear (transverse and/or longitudinal extension tear) was the most frequent type. With the surgical treatment, we were able to markedly improve the parameters studied (pain, medial or dorsomedial deviation of the toe, joint stability, muscle balance, and joint congruence) to acceptable levels, The AOFAS score improved substantially from an average of 52 points preoperatively to 92 points postoperatively.

CONCLUSION

The direct plantar plate repair combined with a Weil osteotomy and lateral soft tissue reefing can restore the normal alignment of the MTP joint. We have demonstrated that the anatomic repair of the plantar plate can correct the deviation of the affected toe (medial, dorsal, dorsomedial or dorsolateral), which lead to diminished pain with improved functional scores.

Relationship between plantar pressure and soft tissue strain under metatarsal heads with different heel heights

BACKGROUND

Metatarsalgia due to increased plantar pressure under the metatarsal head (MTH) is often seen with wearing high-heeled shoes. However, the concomitant soft tissue strain has not been well discussed. The objective of our study was to explore the standing plantar pressure and corresponding soft tissue strain under the metatarsal heads (MTHs) with different heel heights.

MATERIALS AND METHODS

Twenty-one healthy subjects (10 male and 11 female) participated. The plantar pressure and soft-tissue thicknesses were measured simultaneously with a load cell and a 10-MHz linear-array ultrasound (US) transducer respectively. The changes in plantar pressure and soft tissue strain under the MTHs were analyzed for different heel heights.

RESULTS

As hypothesized, plantar metatarsal pressure significantly increased and shifted to the first and second MTHs with increasing heel height from 2 cm to 4 cm (p < 0.05). However, the change in soft tissue strain under the medial forefoot became insignificant when the heel height was greater than 2 cm (p = 0.473 and 0.517).

CONCLUSIONS

Increased heel height resulted in increasing medial forefoot loading pressure; however, the soft tissue exhibited stationary compressibility when the heel height was greater than 2 cm.

CLINICAL RELEVANCE

Our finding provides an understanding of the biomechanical changes with wearing high-heeled shoes and suggests possible strategies to reducing discomfort and risk of injury, such as limiting heel height to no greater than 2 cm and using medial padding under MTHs.

Dynamic morphometric characterization of local connective tissue network structure in humans using ultrasound

Background

In humans, connective tissue forms a complex, interconnected network throughout the body that may have mechanosensory, regulatory and signaling functions. Understanding these potentially important phenomena requires non-invasive measurements of collagen network structure that can be performed in live animals or humans. The goal of this study was to show that ultrasound can be used to quantify dynamic changes in local connective tissue structure in vivo. We first performed combined ultrasound and histology examinations of the same tissue in two subjects undergoing surgery: in one subject, we examined the relationship of ultrasound to histological images in three dimensions; in the other, we examined the effect of a localized tissue perturbation using a previously developed robotic acupuncture needling technique. In ten additional non-surgical subjects, we quantified changes in tissue spatial organization over time during needle rotation vs. no rotation using ultrasound and semi-variogram analyses.

Results

3-D renditions of ultrasound images showed longitudinal echogenic sheets that matched with collagenous sheets seen in histological preparations. Rank correlations between serial 2-D ultrasound and corresponding histology images resulted in high positive correlations for semi-variogram ranges computed parallel (r = 0.79, p < 0.001) and perpendicular (r = 0.63, p < 0.001) to the surface of the skin, indicating concordance in spatial structure between the two data sets. Needle rotation caused tissue displacement in the area surrounding the needle that was mapped spatially with ultrasound elastography and corresponded to collagen bundles winding around the needle on histological sections. In semi-variograms computed for each ultrasound frame, there was a greater change in the area under the semi-variogram curve across successive frames during needle rotation compared with no rotation. The direction of this change was heterogeneous across subjects. The frame-to-frame variability was 10-fold (p < 0.001) greater with rotation than with no rotation indicating changes in tissue structure during rotation.

Conclusion

The combination of ultrasound and semi-variogram analyses allows quantitative assessment of dynamic changes in the structure of human connective tissue in vivo.

Sonographic and MRI evaluation of the plantar plate: a prospective study

The purpose of this study was to establish the accuracy of ultrasound in the examination of the plantar plate by comparing it with MRI, or if available, surgical findings. The lesser metatarsophalangeal joint plantar plates of 40 symptomatic and 40 asymptomatic feet (160 asymptomatic and 160 symptomatic plantar plates) were examined with ultrasound and MRI. Patients treated with surgery were chosen on a clinical basis and provided surgical correlation for the imaging techniques. Symptomatic patients with metatatarsalgia and suspected metatarsophalangeal joint instability were referred by an orthopedic foot specialist; asymptomatic feet were obtained either through examination of the contralateral foot of the symptomatic patients or volunteers. Ultrasound detected 75/160 and 139/160 plantar plates torn in the asymptomatic and symptomatic groups, respectively. MRI detected 56/160 and 142/160 tears in the symptomatic and asymptomatic groups, respectively. The sensitivity of MRI and ultrasound with surgical correlation was calculated to be 87 and 96%, respectively, with poor specificity. Ultrasound correlates moderately with MRI in the evaluation of the plantar plate. Surgical correlations, although limited (n = 10), indicate ultrasound is superior to MRI with more accurate detection of tears.