Dynamic high-resolution ultrasound (DHRUS) and MRI of plantar plate: role in diagnostic iter

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1 Dynamic high-resolution ultrasound (DHRUS) and MRI of plantar plate: role in diagnostic iter Poster No.: C-1003 Congress: ECR 2012 Type: Scientific Exhibit Authors: R. Saporiti, S. Migone, V. Prono, R. Piccazzo, D. Astengo, M Perinetti, A. Muda, G. Garlaschi ; Genoa/IT, Genova/IT Keywords: Musculoskeletal joint, Extremities, Ultrasound, MR, Diagnostic procedure, Trauma DOI: /ecr2012/C-1003 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 19

2 Purpose The purpose of our study is to describe the normal and the pathological aspect of plantar plate, using dynamic high-resolution ultrasound (D-HRUS). The study also aims to establish the role of this modality in diagnosis of degenerative lesions and rupture of the plantar plate. Methods and Materials Dynamic high-resolution ultrasound (D-HRUS) was used to evaluate 36 patients (age range: years, mean age 56 years, 24 females and 12 males) with a previous clinical diagnosis of metatarsophalangeal joint instability and suspect rupture of the plantar plate. In addition, a sonographic study was performed in 10 healthy volunteers to understand the correct scan techniques for the plantar plate and to determine the correct dynamic maneuvers which allow to identify the normal sonographic anatomy of this structure. Every examination was performed using an ultrasound system equipped with a wide band (17-12 MHz) linear transducer with a compound system and software for optimization of image resolution. The standard protocol of investigation consisted of two steps: Longitudinal and axial scans of each metatarsophalangeal joint (Fig. 1A); Dynamic evaluation in dorsiflexion of the toes to delineate the edge of the plantar plate and its possible disruption (Fig. 1B). All patients underwent a magnetic resonance examination too, before ultrasound examination. The MR evaluations were performed with a dedicated low-field (0.18T) MRI system, with sequences oriented on three orthogonal planes of space. Images for this section: Page 2 of 19

3 Fig. 1: Sonographic scans on longitudinal plane (A) and dynamic evaluation with dorsal flexion of fingers (B). Page 3 of 19

4 Results On longitudinal plane, the normal plantar plate is triangular structure with homogeneous echogenic aspect; it bends over the metatarsal head to fit into the proximal phalanx (Fig. 2) and can be easily evaluated by longitudinal plantar scanning at the metatarsophalangeal joint and by passive movements (flexion and extension of the toes). In particular, the dorsal flexion of the phalanx tightens the plantar fascia and its distal insertion at the plantar plate, making this structure from curve to straight. The dorsiflexion also improves the visualization of insertion of the plantar plate. It is difficult to differentiate the proximal edge of the plantar plate from surrounding soft tissues. The dynamic scanning allows to describe the relationships between the plantar plate, the fibrous sheath of the flexor tendons and the articular cartilage (Fig. 3, Fig 4). The evaluation of normal plantar plate in the axial plane reveals a structure curved above the metatarsal head, whose fibers appears sonographically discontinuous but homogeneous (Fig. 5). On sagittal magnetic resonance images, the normal plantar plate presents as a uniform hypointense triangular structure. The hypointense flexor tendon that covers the plantar plate is indistinguishable from it. On coronal plane the evaluation of the plantar plate reveals a band of low signal intensity, C-shaped, centrally located under the metatarsal head. On the plantar surface, a central groove contains the flexor tendon. In our study, the use of D-HRUS allowed to detect a laceration of plantar plate in 34 of 36 studied patients. We present a description of the observed lesion, according to location: In 24 patients a lesion of second toe metatarsophalangeal joint was detected; In 6 patients a lesion of third toe metatarsophalangeal joint was detected; In 4 patients lesions of both second and third toe metatarsophalangeal joints were detected. The rupture of plantar plate appears like a loss of homogeneity and sonographically the laceration appears like small hypoechoic defects in the distal insertional fibers, and can be divided into partial tears (Fig. 6, Fig. 7) and complete tears or full-thickness (Fig. 8): in our study we detected partial tears in 12 patients and full thickness tears in 22 patients. Most tears occur at the distal insertion on the proximal phalanx. In MRI, the features of plantar plate rupture correspond to replacement of the normal low signal intensity area with an area of high signal intensity. Sequences on sagittal plane (Fig. 6B) allow a better assessment of tear thickness, while sequences on coronal plane (Fig. 7B) allow a better assessment of tear position. In all patients, MR confirmed the diagnosis of plantar plate rupture, but in 16 cases it was not possible to confirm or differentiate a partial tear from a full-thickness rupture. Page 4 of 19

5 Images for this section: Fig. 2: Longitudinal sonographic evaluation of metatarsophalangeal joint. Page 5 of 19

6 Fig. 3: Normal ultrasound anatomy of MTPJ. Legend: B = proximal phalanx; P = plantar plate; T = flexor tendon; H = metatarsal head; C = articular cartilage. Page 6 of 19

7 Fig. 4: Normal ultrasound anatomy of MTPJ. Legend: PP = plantar plate; Ph = proximal phalanx; MThead = metatarsal head. Page 7 of 19

8 Fig. 5: Short axis sonographic evaluation of metatarsophalangeal joint. Page 8 of 19

9 Fig. 6: Partial plantar plate rupture at the distal inserction on the proximal phalanx: ultrasound (A) and MR imaging (B). Page 9 of 19

10 Fig. 7: Partial plantar plate rupture at the lateral side: ultrasound (A) and MR imaging (B). Fig. 8: Full-thickness plantar plate rupture the distal inserction on the proximal phalanx: comparison of ultrasound and MR imaging. Page 10 of 19

11 Conclusion Plantar plate is a fibrocartilaginous structure localized at the metatarsophalangeal joint; it presents a slack proximal insertion that fits into periosteum of metatarsal diaphysis, proximally to the metaphysis of metatarsal head, and a distal insertion, strong, that fits firmly and directly on the bone at the plantar face of proximal phalanx distally to the articular surface. The plantar plate has a solid but flexible structure with an articular side on his dorsal face. The metatarsophalangeal joint consists of a joint capsule reinforced on each side by collateral ligaments, dorsally by expansions of the extensor tendons and ventrally by the plantar plate (Fig. 9). The deep metatarsal transverse ligament is interposed between the metatarsal heads. The plantar plate is located centrally and presents multiple connections, including the collateral ligaments, the plantar fascia, intermetatarsal ligaments, interosseous tendons and fibrous sheath of the flexor tendons: these connections make it an important central stabilizer of metatarsophalangeal joint. It mostly occur on second metatarsal joint. In second to fifth metatarsals, plantar plate has an average length of 19mm, a width of 10mm and a thickness of 2-5mm. The central role of the plantar plate is not only anatomical but also biomechanical: this structure, together with the collateral ligaments and surrounding tendons structures, creates a box of passive stabilization, called "box complex" (Fig. 10). The stability of the metatarsophalangeal joint in a static condition is mainly supported by the plantar plate, while in dynamic conditions is due to intrinsic and extrinsic muscles of the foot. The ability of muscles to stabilize the articulation depends on the integrity of the plantar plate. With the rupture of the plantar plate the proximal phalanx assumes a dorsal position, being dorsally dislocated with respect to the metatarsal head, and the extensor tendons are unable to extend the proximal and distal interphalangeal joints. The instability of the MTPJ is clinically manifested as pain in the forefoot or as focal joint pain. Symptoms may include swelling, malalignment, neuritic symptoms and dysfunction of the normal joint biomechanics. MTPJ instability can also be associated with extraarticular disorders such as Morton's neuroma, synovial cysts or intraarticular pathologies such as arthritis or Freiberg's infraction. The term metatarsalgia is often used to describe pain in distal forefoot, but is not a specific diagnosis and does not lead to a particular therapeutic approach. Pain of the forefoot should be carefully analyzed to establish the correct diagnosis: it is therefore necessary to help the patient to determine the exact location of the pain. This may not be easy, since initially the pain can be referred to a large ill-defined area: over time, however, it is Page 11 of 19

12 usually possible to isolate a more limited area. Other factors to consider are the presence of deformity, soft tissue inflammation or pain on palpation of specific regions, as well as the association of neuritic symptoms. The presence of neuritic symptoms in the fingers can indicate an interdigital neuroma. In absence of such symptoms, metatarsophalangeal joint capsulitis or instability should be considered. Palpation of the painful areas may allow differential diagnosis between many of these diseases. For a better orientation in the differential diagnosis of metatarsalgia it is essential to provide a brief description of the main diseases which can occurr. Interdigital neuroma This common cause of ill-defined forefoot pain commonly occurs in the second or third intermetatarsal space, rarely in the first or fourth. It is extremely unusual to find two neuromas in the same foot.numbness or neuritic symptoms may occur in the distribution of the second or third common digital nerve. It is important to establish the state of the circulation in the foot, since vascular insufficiency is an occasional cause of pain in the forefoot. The presence of metatarsophalangeal joint instability, plantar callosities and deformities of the fingers are easily detectable. The intermetatarsal spaces should be investigated for compressive causes. Intractable Plantar Keratosis When a callus develops in one or more lateral metatarsal bones, it is called intractable plantar keratosis. Its appearance can vary from little well localized keratosis to a spread large callus. The latter often develops as the result of repeated abrasion associated with sporting activities. The pain often increases with the formation of a very thick callus. A smaller callus develops most frequently in a single metatarsal head and is associated with enlargement of the lateral condyle.it is important to determine the entity and duration of symptoms, to identify which activities exacerbate it. Instability of the metatarsophalangeal joint The diagnosis of metatarsophalangeal joint instability may be difficult, since the illdefined forefoot pain may also be associated with both extra-articular abnormalities, such as interdigital neuroma and synovial cysts, both intraarticular abnormalities, including inflammatory arthritis, degenerative arthritis and Freiberg's infraction. Page 12 of 19

13 It has been suggested that, in older women, the long-term use of high-heeled shoes could put the metatarsophalangeal joints in a position of chronic hyperextension, which can lead to thinning or rupture of plantar plate resulting in capsular instability. Instability was also observed in young athletes, associated with a repetitive mechanical stresses or excessive length of metatarsal bones. This event can also occur suddenly, but it is more common with an insidious course lasting several months. The radiological assessment may show a widening of the joint because of the metatarsophalangeal joint synovitis, effusion secondary to degenerative joint hyperextension or to metatarsophalangeal joint malalignment due to a medial or lateral capsular fracture. The key role of metatarsophalangeal joint alterations in the pathogenesis of metatarsalgia is relevant: different types of diseases can affect the forefoot causing pain, but the most significant are those that have as "primus movens" a lesion of the plantar plate. This is a direct consequence of the importance of this structure in the metatarsophalangeal joint: the plantar plate plays a biomechanical role of central stabilizer in the joint, and it is subjected to considerable compressive loads and tension forces, acting as a joint surface support for the metatarsal heads. Consequently, the importance of clinical classification of pain forefoot depends primarily on a correct differential diagnosis. In last years, imaging of the metatarsophalangeal joint and of the plantar plate in particular, became the protagonist of a constant evolution, with many modalities involved as the standard of reference. MRI has been considered as the gold standard during all the '90s, as demonstrated by a series of studies, often providing anatomic and histologic correlation with imaging findings. In last years literature started to promote the idea of applying ultrasound to the study of plantar plate, with studies that showed the skill to evaluate the anatomy as well as pathological changes of the joint. Our study fits into this trend, proposing the use of D-HRUS as an alternative modality to MR in the study of plantar plate. From results we have presented, it is clear that ultrasound is a viable, non-invasive and unexpensive option for the diagnosis of plantar plate rupture. The main limitations to our study are due to the fact that ultrasound requires a long learning curve, and that the examination should be performed with new generation equipment (not available everywhere) and by experienced musculoskeletal-dedicated radiologists to achieve the diagnostic accuracy of MR. When these conditions occur, it allows high anatomical detail in study and identification of the plantar plate and of its lesions. In particular, in our experience, the dynamic high-resolution ultrasound performed with rigorous and standardized approach could act as a first level of investigation, since it allows to differentiate the partial lesions from the complete ones. Page 13 of 19

14 We therefore believe that a correct clinical approach and a diagnostic iter in which dynamic ultrasound plays a central role, are essential to achieve a right diagnosis of metatarsophalangeal joint instability, often unrecognized and potential source of frustration for the surgeon. Images for this section: Page 14 of 19

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16 Fig. 9: Sagittal image at the metatarsophalangeal joint with focusing on the plantar plate. Fig. 10: Coronal section at the metatarsophalangeal joint. Page 16 of 19

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