MRI Utility in Patients with Non-Traumatic Metatarsalgia: a Tertiary Musculoskeletal Center Observational Study

The Egyptian Journal of Radiology and Nuclear Medicine (2015) 46, 1057–1064

Egyptian Society of Radiology and Nuclear Medicine The Egyptian Journal of Radiology and Nuclear Medicine

www.elsevier.com/locate/ejrnm www.sciencedirect.com

ORIGINAL ARTICLE MRI utility in patients with non-traumatic metatarsalgia: A tertiary musculoskeletal center observational study

Mohamed Ragab Nouh a,*,3, Ehab Ali Abd El-Gawad b,1,3, Samir Mahmoud Abdulsalam c,2,3 a Department of Radiology, Faculty of Medicine, Alexandria University, Alexandria, Egypt b Department of Radiology, Faculty of Medicine, Minia University, Minia, Egypt c Department of Orthopedics, Al-Razi Hospital, Sulibikhate, 13001, Kuwait

Received 3 January 2015; accepted 11 August 2015 Available online 1 September 2015

KEYWORDS Abstract Aim: To assess the utility of MRI of the forefoot in the workup of patients with non- Non-traumatic; traumatic metatarsalgia and inconclusive initial radiographs. Metatarsalgia; Patients and methods: The study included 125 patients (46 males and 79 female) with a mean age MRI; 38.8 years (age range 7–74 years) presented with forefoot pain. Patients with history of a clear recent Utility forefoot trauma, gross osteo-articular deformities and previous forefoot surgery were excluded. Radiographic evaluations of the fore-foot followed by MRI imaging were performed using 1.5-T scanner. We stratified our patients into 4 groups: (a) stress-related, (b) arthritic-related, (c) infection-related, and (d) neoplastic disorders. Results: The most common causes of fore-foot pain, in our series, were Morton neuroma in 20 cases (16%), metatarsophalangeal (MTP) instability syndromes in 15 cases (12%) and sesamoid pathologies in 9 cases (7.2%) of the stress-related group. In arthritic group, rheumatoid arthritis and osteo-arthritis were equally the commonest entities (9.6%). Foreign body invasion in 10 patients (8%) was the common cause of infection-related forefoot pain. In the neoplastic category plantar fibromas were the commonest lesion (5.6%) in our series. Conclusion: MR imaging depicted numerous forefoot soft-tissue and early osteo-articular processes in absence of gross fractures or other remarkable findings on radiographic screening. Ó 2015 The Authors. The Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).

* Corresponding author at: Department of Radiology, Al-Razi Hospital, Sulibikhate, 13001, Kuwait. Tel.: +20 1116590365; fax: +20 34869754. E-mail addresses: [email protected] (M.R. Nouh), [email protected] (E.A. Abd El-Gawad), [email protected] (S.M. Abdulsalam). 1 Tel.: +20 1067473970; fax: +20 862342505. 2 Tel.: +965 99458020; fax: +965 24844240. 3 All authors have approved the article and actively contributed in the work. Peer review under responsibility of Egyptian Society of Radiology and Nuclear Medicine. http://dx.doi.org/10.1016/j.ejrnm.2015.08.004 0378-603X Ó 2015 The Authors. The Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 1058 M.R. Nouh et al.

1. Introduction articular surfaces, metatarsophalangeal (MTP) and inter- phalangeal (IP) joints deformity and/or subluxation, presence Metatarsalgia is a descriptive clinical terminology for pain or absence of arthritic changes. involving the metatarsal region of the foot (1,2). It is a common clinical complaint among different age groups, often dis- 2.4. MR imaging protocol abling and can interfere with patient routine activities (2,3). Various traumatic and non-traumatic conditions are associ- All the MR imaging studies were performed on a 1.5-T scanner ated with metatarsalgia including stress fractures of the meta- (Signa HD; GE Medical Systems, Milwaukee, WI, USA) using tarsals, Freiberg infraction, sesamoid disorders, Morton a quadrature send-receive extremity coil with the patient com- neuroma, as well as a spectrum of foot tendinopathies, arthro- fortably positioned and the foot adequately immobilized. pathies, and infection (1). These conditions are difficult to dif- MR images acquisition usually starts with a localizer in the ferentiate on clinical bases only. Hence, imaging workup is three standard orthogonal planes. After that, a small field of essential for diagnosis and management (1,4). view (FOV) = 10–12 is used to prescribe fat-suppressed Initial assessment typically starts with plain radiographs proton-density (FS-PD) images [TR/TE = 2500/40 ms] in that may reveal fractures and/or bony lesions. However, it is sagittal plane. After that, T1W [TR/TE = 500/12 ms] and limited by insensitivity to subtle bony abnormalities and fast-spin echo (FSE) T2W [TR/TE = 4000/90 ms] short-axis soft-tissue disorders causing forefoot pain (1,2,5). (coronal) images of the fore-foot are acquired; from toe tips Magnetic resonance imaging (MRI) is a reproducible imag- to the level of talonavicular articulation, perpendicular to the ing modality with superior soft-tissue contrast resolution and long axes of metatarsal bones. Long-axis T1W images are multi-planar capability which makes it important in the early acquired to document bony changes. Additional fat- diagnosis of metatarsalgia when initial radiographic findings suppressed T2W, PD and/or STIR [TR/TE/ are inconclusive (1,2). TI = 4000/90/140 ms] images are acquired in best plane, visu- We sought to assess the utility of MRI of the forefoot in the alizing the observed pathology to depict associated soft-tissue workup of patients presented with metatarsalgia in whom and/or bony abnormalities of the foot. Section thickness was traumatic history is unclear and their initial radiographs are 3–5 mm without an inter-slice gap, and the image matrix was inconclusive. 256 Â 256. Intravenous contrast was only used in cases where inflammation and neoplasms are suspected. 2. Patients and methods 2.5. MR imaging evaluation 2.1. Study design and research ethics All MR studies were interpreted by all authors and a final Our ethical committee approved the current prospective study imaging diagnosis was concluded by consensus. Each MRI to evaluate patients presented with non-traumatic metatarsal- study was systematically scrutinized for the following: gia. The study was carried out over 12 month period starting on early August 2013, at Al-Razi Orthopedic and trauma Cen- The skeletal framework of the forefoot; including the hallux ter, Kuwait. Written informed consent was obtained from all sesamoids as well as any incidentally recognized fore-foot patients sharing in the study. accessory bones; for fracture lines, periosteal reaction, and bony lesions. 2.2. Study population, inclusion and exclusion criteria The small articulations of the fore-foot for the presence of joint effusions, synovial thickening, intra-articular loose bodies, articular surfaces erosions and osteophytes as well A total of 125 subjects presented to the outpatients’ foot clinic as juxta-articular abnormalities. over 12 month period were assessed for their clinical problems. The integrity of the long tendons of foot on both dorsal and Patients’ history, clinical examinations, and laboratory and plantar aspects as well as the small muscles of the foot. surgical data were recorded and used to assess utility of MR The plantar fat pad including the plantar plates of the MTP examinations in the evaluation of these patients’ symptoms. articulations for any structural or signal changes. Patients with clinical complaints and imaging findings The interdigital spaces for mass lesions and/or abnormal related to mid-foot, hind-foot and ankle were managed appro- fluid collections. priately with subsequent exclusion from our study popula- tions. Also, any patient with history of a clear recent (less than a week) forefoot traumatic event, clinically gross osteo- 3. Results articular deformities (e.g. hammertoes and digital deformities) and/or previous forefoot surgery was excluded from the current study population. Of the 1185 subjects interrogated over 12 month period to our foot outpatient clinic, clinical and radiographic evaluations 2.3. Radiographic screening and evaluation resulted in a cohort of 125 patients (46 males and 79 female with a mean age 38.8 years (age range 7–74 years) achieving the classic presentation of non-traumatic metatarsalgia. All Radiographic evaluation of the fore-foot; using the standard study population has both initial radiographs and MR evalu- weight-bearing AP, lateral and AP oblique views of the fore- ations of their foot problems while only 89 patients had one foot; was done for all study population. Radiographs were or more follow-up MR examinations. evaluated by the authors for integrity of the cortical bones, MRI utility in patients with non-traumatic metatarsalgia 1059

Table 1 The distribution of forefoot lesions detected on MRI evaluations of our study population. Radio-pathologic diagnosis No. of Percentage cases (%) Stress-related Stress fractures 7 5.60 Sesamoid pathology 9 7.20 MTPJ instability syndromes 15 12.00 Callus 2 1.60 Dorsal ganglia 5 4.00 Morton’s neuroma 20 16.00 Arthritis Juvenile arthritis 8 6.40 Rheumatoid arthritis 12 9.60 Gouty arthritis 2 1.60 Osteoarthritis 12 9.60 Infection Osteomyelitis 2 1.60 Foreign body reaction 10 8.00 Neoplastic Glomus tumor 1 0.80 Lipomatosis 3 2.40 Tendon sheath venous malformation 1 0.80 Plantar ﬁbroma 7 5.60 Deep ﬁbromatosis 2 1.60 Giant cell tumor of tendon sheath 1 0.80 (GCT-TS) Unremarkable Studies 6 4.80 Total 125 100.00

The duration of forefoot pain ranged from 1 week to 3 months. For simple clinical justification of MR examination of the forefoot, we stratified our patients according to the salient underlying etiopathologic processes (Table 1) into 4 groups: (a) Stress related disorders, (b) Arthritic-related disorders, (c) Infection-related disorders, and (d) Neoplastic disor- Fig. 1 Morton’s fibroma. Short-axis scans of the forefoot on ders. The most common cause of fore-foot disorders in T2W (a), T1W SE (b) and post-gadolinium fat-suppressed T1W stress-related category in our series was Morton neuroma in image (c) showing 3rd inter-metatarsal space soft-tissue fullness at 20 cases (16%) followed by MTP instability syndromes in 15 the level of M3 and M4 heads (arrows). The lesion shows low cases (12%) and sesamoidal pathologies in 9 cases (7.2%). signal intensity on both T1 and T2 weighted images with well- The size of Morton’s neuromas (Fig. 1) ranged between 7 depicted moderate enhancement on the fat-suppressed T1W and 19 mm on short-axis MR images. Eight of them were con- image. firmed surgically while twelve were diagnosed based on their classic imaging and clinical findings on both initial studies and follow-up. There were 7 cases with stress fractures; all of them had The 15 cases with MTP instability syndromes included unremarkable radiographs while their MRI showed marked cases with degenerated or torn plantar plates, variable degrees bone marrow edema of a metatarsus with low-signal fracture of flexor digitorum tendon medial translations, MTP collateral lines of variable extensions. All stress fractures were put in ligament disruptions and even MTP joint dislocations (Fig. 2). casts and followed-up (Fig. 4). There were 9 cases where the hallucal sesamoids showed The five dorsal ganglia cases showed fluid containing cysts variable degrees of reactive bone marrow edema. All of them over the dorsal surface of the metatarsus. All of them were were females and none of them gave a significant traumatic excised. The two cases of callus formation showed low-signal history. Eight of them showed good response on conservative intensity of the subcutaneous tissues under the tibial side of measures and diagnosed as sesamoiditis. However, one case their hallux associated with mild valgus deformity and were exhibited progressive cystic bony changes along with marked managed conservatively. peri-hallucal soft-tissues edema on her MRI (Fig. 3) with no In arthritic group, rheumatoid arthritis and osteo-arthritis response to conservative measurements that necessitated were equally the commonest entities diagnosed in our study sesamoidectomy. cohort constituted of 12 cases for each entity (9.6%). All the 1060 M.R. Nouh et al.

Fig. 2 Plantar plate degeneration of the second MTP joint with subsequent 2nd metatarsal ray dislocation syndrome. Lateral X-ray of the foot (a), sagittal T2W FS (b), short-axis T1W images (c) of the forefoot; as well as post-contrast serial short-axis T1W images (d and e); show non-visualized plantar plate of the second MTP (short-thick arrow) due to its chronic degeneration with dorsal subluxation of the proximal phalanx, marked arthritic changes of the MTP (long arrow on b) with small dorsal osteophyte, joint effusion and edematous enhanced synovium as well as peri-articular soft-tissues (arrow heads in d and e). twelve cases with rheumatoid arthritis in our series showed lumbar disk prolapses and four cases with history of long clinico-laboratory evidences of rheumatoid arthritis. Interest- standing controlled diabetes and their complaints were ingly, two of them showed the presence of (MTP) joint effu- explained by evolving diabetic neuropathy. sions on their feet MRI while X-ray evaluation of their hands was unremarkable. Also, a subset of eight patients; rep- 4. Discussion resenting (6.4%); with MTP joint effusions and elevated sero- logic inflammatory markers were clinically fit into the juvenile Non-traumatic forefoot pain or metatarsalgia is an increas- arthritic groups. Two patients (1.6%) with arthritic changes ingly recognized common reason for medical consultation. exclusive to their 1st MTP joints and high-normal values of Morton’s neuroma is the prototype of forefoot pain (5–8). their serum uric acid levels were consistent with the diagnosis However, a vast array of different pathologic conditions pro- of gout. duces forefoot pain and imaging may be required to disclose For the infection-related disorders, a common history of the etiology of unclear forefoot pain or when more than one foreign body invasion was clearly given in ten patients (8%), web space is affected (1). Moreover, conventional radiography and none of these cases showed radiopaque foreign bodies is limited in depiction of early subtle bone abnormalities and/ on radiography with variable degrees of soft-tissue inflamma- or soft-tissue disorders producing forefoot pain (1). tory response were found around the signal void foreign bodies The current study revealed that Morton’s neuroma is the on their MR evaluations (Fig. 5). Wooden splinters and glass commonest cause of metatarsalgia overall; and especially in shards were retrieved on surgery. In another two cases (1.6%) the group of the stress-related disorders. In our series, all neu- with type-I diabetes, forefoot pain was explained by metatarsal romas were located in the second and third intermetatarsal osteomyelitis with clinico-laboratory evidences of infection. spaces. These coincide with previous studies confirming the In the neoplastic category plantar fibromas (7 cases) (5.6%) high prevalence of Morton neuroma on US and MR studies were the commonest lesions in our series. Three cases (2.4%) (5–7) as well as cadaveric studies (8) with emphasis on their of forefoot lipomatosis were found. One localized lipoma predilection to the second and third inter-metatarsal spaces was surgically excised (Fig. 6) and two cases showed diffuse as well as female gender (5–8). lipomatous involvement of their forefeet as a part of diffuse MTP joint instability disorders can be presented in acute, body lipomatosis. Surgical confirmation was done in five of subacute and chronic forms (2,9). They represent a continuum the seven plantar fibromas, one case of giant cell tumor of of pathologic entities progressing from acute capsulitis to sub- the tendon sheath, one case of AV malformation of the tendon acute plantar plate rupture and chronic dislocation of the joint sheath, one case of digital glomus tumor; (0.8% for each); and (2,9). Biomechanical dysfunction, caused by failure of the two cases (1.6%) of deep fibromatosis/extra-abdominal des- plantar plate and collateral ligaments that stabilize the MTP moids (Fig. 7). joints, is the major etiologic pathology suspect (2,9,10). How- Six patients (4.8%) showed unremarkable radiographic and ever, they can occur in association with other entities as neuro- MR evaluations of their forefeet. These included 2 cases with muscular and arthritic disorders (2,10). MRI utility in patients with non-traumatic metatarsalgia 1061

Our series showed that MTP joint instability disorders form the second common group associated with traumatic metatarsalgia. Most of them were found at the 2nd MTP joint in agreement with the results of recent reports (11,12). Plantar plate injury is the main underlying cause of MTP joint instabil- ities due to its central location and multiple important attach- ments (9,11). Our study confirmed superb capabilities of MRI in the recognition of plantar plate injuries by MRI. This agreed with the results of previous reports (10,12,13). Hallux sesamoids pathologies are not uncommon conditions that can provoke forefoot pain and can be presented in both acute and chronic forms (1,2,14). MR is a well- recognized useful tool in depiction of hallux sesamoid pathology (14,15). Similarly, the current MRI study has successfully identified marrow edema associated with sesamoiditis. Previous reports emphasized the high sensitivity, accuracy and less invasiveness of MRI in the diagnosis of stress fractures earlier in the disease even with negative radiographs (16–18). Likewise in our series, MR identified seven stress fractures presented clinically by vague forefoot pain with unremarkable radiographic studies. Dorsal ganglia/synovial cysts are the most common soft- tissue masses of the foot (1). All ganglia detected on MR studies of our series were dorsal in location, clinically palpable and in female patients. The increased number of these lesions in our series; compared to previous studies (19); may be attribu- ted to our selectivity limited to the forefoot region. Our study revealed that inflammatory arthritis, osteoarthrosis and gout are the commonest arthritides target- Fig. 3 Sesamoiditis. A 46 years female with long history of ing the forefoot; in descending order of frequency. bilateral forefoot pain that worsen last months on the left side. Small joint effusions, synovitis and bone marrow edema are Sagittal FS-T2W (a), short axis FS-T2 (b) and T1W (c) images of salient MR imaging features of rheumatoid arthritis; com- her left foot showing marked edema of the left fibular sesamoid monly seen early in the disease. Likewise, these are the com- with cystic changes (arrows). Also noted, are the peri-sesamoid monest findings in juvenile inflammatory arthritis (JIA) (20). soft-tissue changes and osteoarthritic changes of the M1 head with In both age groups, the forefoot joints are the most common small marginal osteophyt. involved joints beside hand (20–22). Ostendorf et al. (23), found that MR detected involvement of forefoot joints and

Fig. 4 Stress fracture of the forefoot. Long-Axis PD fat-suppressed image (a) T1W image (b) and oblique AP radiograph of the foot (c). MR shows focal bone marrow edema with hair-like low signal intensity incomplete fracture line within the proximal M2 shaft (arrows). These were not apparent on radiography. These features were consistent with stress metatarsal fracture. Note the bipartite tibial sesamoid on (c). 1062 M.R. Nouh et al.

Fig. 5 Forefoot foreign-body granuloma. A 35 year old agricul- tural worker presented with 1 month history of forefoot pain with unclear traumatic history. PD fat saturated short-axis images (a and b) and sagittal image (c) showed a thin signal-void structure that is linear on sagittal image and rounded on short-axis images. Fig. 6 Forefoot localized lipomatosis. Short-axis scans of the It is surrounded by hyperintense halo and hyperintense signal of forefoot on T1W (a) and PD fat-suppressed image (b) showing the surrounding soft-tissues of the plantar aspect of 1st inter- fibular-sided subcutaneous multi-lobulated fatty lesions wrapping metatarsal space. A palm-thorn was retrieved on surgical around its both dorsal and plantar aspects. The lesion exhibited exploration. high-signal intensity on T1W images with no enhancement following IV gadolinium administration on post-contrast T1 marrow edema in patients with early rheumatoid arthritis sagittal image (c). The lesion gets annihilated on fat-suppressed (RhA); even before detection of hand and wrist affections. sequence (b). Note the fine low signal bands tethering the different This is comparable to our study where two patients with lobules consistent with localized lipomatosis. MTP joint effusions with raised inflammatory markers and clinical context of RhA were found. Also, the eight patients fit- ting in the juvenile arthritic group showed synovial effusions validity of MR of the forefeet in such group of patients (23,24) on their forefeet MR examinations. The early recognition of even when MR evaluation of hands is unremarkable (25). these imaging findings allows use of powerful and expensive In the current series, MR effectively diagnosed cases of fore- biological disease modifying anti-rheumatoid drugs foot osteomyelitis and foreign body invasions with concomitant (DMARDs) with subsequent improve in patient’s welfare inflammatory responses. MR detected bone marrow edema, sig- and abortion of a crippling disease (20,22). nal void foreign bodies and soft tissue edema and enhancement In our study, MR findings of MTP joints effusion, synovitis following intravenous gadolinium administration; in concor- and marrow edema confirmed the clinical suspicion of rheuma- dance with the previous literature reports (26,27). toid arthritis in two patients with vague articular symptoms, Tumors arising in the foot are relatively rare with higher non-specific laboratory markers and unremarkable hand radio- incidence for those of the soft-tissue origin, of benign nature graphs. This is comparable to previous reports stressing the and among female population (28,29). Tumors in the forefoot MRI utility in patients with non-traumatic metatarsalgia 1063

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