Introduction: The trapeziometacarpal (TMC) joint is a complex joint, whose anatomy and function are different from the metacarpophalangeal joints of the long fingers. The stability of this joint is ensured at three levels by multiple structures: osteochondral, capsulo-ligamentous, and musculo-tendinous. The anatomical and biomechanical structures ensuring the stability of the TMC joint are perfectly evaluated on magnetic resonance imaging (MRI), with a high degree of confidence. All described ligaments are anatomically visible and perfectly assessed on MRI and ultrasound (US): the dorsoradial ligament, the posterior oblique ligament, the intermetacarpal ligament, the ulnar collateral ligament, the two bundles of the anterior oblique ligament (break ligament), as well as the superficial anterior oblique and deep anterior oblique ligaments. Methodology: This educational review assesses the TMC joint anatomy using high-field MRI and US compared with cadaveric specimens as well the biomechanics of this joint. In addition, it highlights pathological patterns of traumatic (sprain, dislocation, and fractures) and degenerative diseases. Results and conclusion: Knowledge of TMC joint anatomy is crucial to the radiologists' understanding and assessment of various traumatic and degenerative pathologies, and thus helps clinicians and surgeons choose the appropriate treatment.

Objectives: The aim of this study was to evaluate the diagnostic performance, image quality, and inter- and intra-observer agreement of the 3D T1 multi-echo fast field echo (mFFE) sequence in cervico-thoraco-lumbar vertebral fractures compared with conventional computed tomography (CT) as the gold standard. Methods: We conducted a prospective single-centre study including 29 patients who underwent spinal magnetic resonance imaging (MRI) at the surgeon’s request, in addition to CT for vertebral fracture assessment and classification. A 3D T1 mFFE sequence was added to the standard MRI protocol. Consecutively, two readers analyzed the 3D mFFE sequence alone, the 3D mFFE sequence with the entire MRI protocol, including the STIR and T1 sequences, and, finally, the CT images in random order and 1 month apart. A standardized assessment was performed to determine the presence or absence of a fracture, its location, its classification according to the Genant and AO classifications for traumatic and osteoporotic fractures, respectively, the loss of height of the anterior and posterior walls of the vertebral body, and the presence of concomitant disco-ligamentous lesions. Contingency tables, intraclass correlation coefficients, and Cohen’s kappa tests were used for statistical analysis. Results: A total of 25 fractures were recorded (48% cervical, 20% thoracic, and 32% lumbar), of which 52% were classified A, according to the AO classification system. The quality of the 3D mFFE image was good or excellent in 72% of cases. Inter-observer agreement was near perfect (0.81–1) for vertebral body height and for AO and Genant classifications for all modalities. Intra-observer agreement was strong-to-near perfect between CT and the 3D mFFE sequence. Regarding the diagnostic performance of the 3D mFFE sequence, the sensitivity was 0.9200 and 0.9600, the specificity was 0.9843 and 0.9895, and the accuracy was 0.9861 and 0.9769 for Readers 1 and 2, respectively. In addition, up to 40% of intervertebral disc lesions and 33% of ligamentous lesions were detected by the 3D mFFE sequence compared to CT, allowing four AO type A fractures to be reclassified as type B. Conclusions: The 3D mFFE sequence allows accurate diagnosis of vertebral fractures, with superiority over CT in detecting disco-ligamentous lesions and a more precise classification of fractures, which can prompt clinicians to adapt their management despite an image quality that still requires improvement in some cases. Key points: Vertebral fractures and disco-ligamentous lesions can be assessed using CT-like MRI sequences, with 3D T1 mFFE being superior to CT for the detection of disco-ligamentous lesions. CT-like images using the 3D T1 mFFE sequence improve the diagnostic accuracy of bone structures in MRI.

Hallux valgus (HV) is a complex triplanar deformity of the first ray that has traditionally been evaluated using weightbearing radiographs. However, these two-dimensional techniques are limited in their ability to assess the rotational and multiplanar components of the deformity. Weightbearing computed tomography (WBCT) now enables a three-dimensional assessment of the foot under physiological load, providing new insights into first ray pathology. Recent WBCT-based studies have shown that HV is part of a global malalignment of the first ray, characterized by first metatarsal pronation, medial column instability, and progressive sesamoid subluxation. These findings have refined the understanding of pathomechanical mechanisms and have influenced surgical decision-making, particularly regarding the correction of rotational deformities and instability of the tarsometatarsal joint. Emerging semi-automated tools and artificial intelligence–based methods further improve the reproducibility and efficiency of WBCT analysis. New quantitative techniques such as distance mapping and coverage mapping allow detailed assessment of articular relationships. Overall, WBCT represents a paradigm shift toward a more accurate, standardized, and comprehensive evaluation of HV.

The metacarpophalangeal joint (MCPJ) of the long fingers is essential for various hand functions. Joint kinematics are complex, involving flexion-extension, lateral movements, and axial rotation. During these motions, different joint stresses occur. The long finger MCPJ operates through a balance between mobility on one hand and stability and joint congruence on the other. Anatomical structures ensuring this balance through adaptive biomechanical mechanisms include the articular surfaces, which provide minimal stabilization except at the terminal degrees of flexion; the capsulo-ligamentous system, which acts as the primary stabilizer by maintaining constant joint tension; and the musculo-tendinous system, which ensures stability during movement. An anatomo-biomechanical and imaging approach facilitates the understanding of the physiological and pathological aspects of the long finger MCPJ and contributes to improved therapeutic strategies. The aim of this article is to provide a detailed description of the normal anatomy and biomechanics of the MCPJ of the long fingers, correlated with imaging, in order to improve the understanding of physiological and pathological aspects. This educational review presents the normal anatomy and biomechanics of the long finger MCPJ through imaging. The various components of the MCPJ of the long fingers are detailed, including articular surfaces, capsule, collateral ligaments, deep transverse metacarpal ligament, volar plate, dorsal triangular fibrocartilage, dorsal hood, extensor tendons, sagittal bands, and the interosseous and lumbrical muscles. In addition to standard radiography, several imaging modalities are used to evaluate the MCPJ of the long fingers. Dynamic conventional radiography assesses joint stability. Computed tomography (CT) or cone-beam CT (CBCT) can complement the assessment. High-resolution ultrasound (US) is well suited for dynamic studies. High-field 3T magnetic resonance imaging (MRI) provides excellent spatial resolution and contrast. A thorough knowledge of anatomy and biomechanics is essential for the imaging analysis of the MCPJ of the long fingers and forms the basis for exploring both normal and pathological aspects.

Hallux valgus (HV) is a common and complex three-dimensional deformity of the first ray, resulting from multifactorial interactions involving anatomical, biomechanical, ligamentous, muscular, and extrinsic factors. The absence of a single etiological mechanism explains the wide variety of proposed surgical techniques and highlights the need for individualized management. The therapeutic strategy is based on a structured radioclinical weight-bearing assessment integrating angular parameters, first-ray stability, sesamoid alignment, and joint status. Depending on the severity of the deformity and the presence of associated instability, surgical options include distal, diaphyseal, or proximal osteotomies, Lapidus tarsometatarsal arthrodesis, and metatarsophalangeal arthrodesis. Certain complex situations, particularly those associated with metatarsus adductus or juvenile HV, require specific morphological analysis because of an increased risk of recurrence and particular biomechanical constraints. Postoperative imaging plays a central role in the assessment of surgical outcomes. It allows evaluation of deformity correction, osteotomy healing, fixation stability, sesamoid repositioning, and restoration of first-ray alignment. Weight-bearing radiographs remain the reference examination, whereas WBCT enables a more precise three-dimensional analysis of rotational correction, first metatarsal pronation, and the sesamoid complex. Imaging is also essential for the detection of postoperative complications, including recurrence, malunion, nonunion, avascular necrosis, transfer metatarsalgia, infection, osteoarthritis, and nerve injury. WBCT currently represents a major complementary tool for the analysis of multiplanar corrections and their biomechanical consequences. Thorough knowledge of normal and pathological postoperative findings is essential to optimize the management of HV.

There are numerous pathologies of the intrinsic muscles of the hand (IMH). Muscle denervation syndromes of the hand are common in pathologies of the median nerve (MN) and ulnar nerve (UN). They occur following carpal tunnel syndrome, Guyon’s canal syndrome, traumatic, tumoral, inflammatory, or proximal nerve lesions due to upper cervical radiculopathy, or brachial plexus lesions. Myositis of the IMH occurs in various contexts. Traumatic muscle injuries of the hand are rare. Some are characteristic, such as lesions of the third interosseous muscle (IOM) or lesions of the lumbrical muscles (LM) in climbers. Saddle syndrome is due to adhesions of the lumbrical-interosseous intermuscular junctions. It is very often overlooked. In rheumatoid arthritis, tendon tenosynovitis of the IOM is frequently encountered. Enhancement of the LM may be an early imaging marker of the disease. Multiple tumor or pseudotumoral masses can develop within or around IMH. All of these pathologies can be accurately assessed using high-resolution dynamic ultrasound (US) and high-field 3T magnetic resonance imaging (MRI). This educational review presents the aspects of the various IMH pathologies on high-resolution US and high-field 3T MRI. There are numerous IMH pathologies. A radiologist’s knowledge and assessment of these various pathologies allows clinicians and surgeons to make an early and accurate diagnosis and choose the most appropriate treatment.