Secondary Abutment Syndromes of the Wrist in Trauma: A Pictorial Essay

Traumatic lesions of the wrist occur frequently and may give rise to underdiagnosed secondary abutment syndromes. The latter are a common cause of incapacitating pain and limited range of motion, despite minimal or even absent alterations on radiographs. Moreover, the complex wrist anatomy often results in ignorance or underappreciation of these syndromes. This paper presents a pictorial review of frequent and rare secondary abutment syndromes at the wrist joint, which – in contrast to primary abutment syndromes – are not based on anatomical variants or congenital deformations. The merit of each imaging modality is briefly mentioned.

Intra-articular fractures of the radius may heal with a residual step-off [6], seen on radiographs, CT, and MRI ( Figure 1A-C). The radial deviation is limited. MRI illustrates the disappeared cartilage ( Figure 1A and B) or the surface disruption ( Figure 1C). In radial deviation ( Figure 1B), bumping of the scaphoid against the prominent radial fossa zone causes repetitive impaction, resulting in BMO.

Radiolunate abutment
Lunate bone impaction on its articular fossa may cause SAS. Parasagittal radial fractures ( Figure 1D) need careful follow-up by radiographs or CT [6] in order to detect displacements, possibly causing SAS (Figure 1E and F) and limiting the ulnar deviation ( Figure 1F).

Radioulnar abutment
Distal radioulnar joint (DRUJ) fractures are difficult to evaluate on radiographs, particularly coronal sigmoid notch fractures (Figure 2A and B). Bony incongruity is better evaluated by (cone beam-)CT and a cartilage step-off ( Figure 2C and D) by MRI. Pronation and supination may be hampered during the radial movement around the ulna [7]. Even minor deformities may cause severe dysfunction.

Ulnar impingement
A relative ulnar shortening may appear after trauma, causing a DRUJ impingement (Figure 2E and F). Excessive ulnar shortening or resection may cause secondary impingement [8]. The appearance is equal to a congenital short ulna.

Ulnar (intra)styloid abutment
Styloid process fractures may fail to heal, resulting into fragmentation and collision during ulnar deviation. MRI highlights neo-articulation and BMO (Figure 3A-C). The triangular fibrocartilage complex (TFCC) ulnar insertion (fovea and tip) in relation to these fragments is depicted ( Figure 3B). Basal fractures may lead to DRUJ instability [9,10]. Ultrasound or MRI performed in pronation and supination may confirm a dynamic extensor carpi ulnaris tendon dislocation (empty sulcus sign).

Stylo-triquetral abutment
Due to styloid process length increase, impaction with the triquetral bone may appear ( Figure 3D-G). As in the classical abutment, the Garcia-Elias index [11] may indicate the risk of SAS development. Surrounding synovitis is frequent (prestyloidal synovitis).

Ulnolunate and/or ulnotriquetral abutment
In secondary positive ulnar variance, the latter abuts the lunate and/or triquetral bone and eventually leads to ulnar head deformation (Figure 4A-B). It may be associated with a TFCC tear. A lengthening of more than 3 mm may be symptomatic (Hulten criteria) [12]. TFCC lesions and BMO typically at the proximal-ulnar corner of the lunate bone are revealed early by MRI (Figure 4C-E).

Ulnar translation with abutment
Extensive destruction of extrinsic ligaments leads to a proximal-ulnar carpal shift [13], creating a reversed status compared to ulnar abutment (ulna approaches carpus). The lateral widening of the radioscaphoid joint and the lunate position versus its corresponding articular fossa (less than 50% overlap in neutral position) are hallmarks on radiographs ( Figure 5A). MRI presents the cartilage destruction, BMO, and eventual TFCC lesions (Figure 5B and C).   Fractures appear most frequently at the scaphoid waist [14]. Radial deviation gives an impaction at a pseudarthrosis. Contact zone deformation (Figure 6A and B) and mobility between the fragments are illustrated on radiographs. BMO and extrinsic ligamentous lesions are delineated by MRI.

Lunar abutment
Avascular necrosis -probably due to chronic microtraumata -with deformation starts at the radial side [15]. Due to the height loss, the ulnar side approaches the ulna (reversed situation of ulnar abutment) (Figure 7A). The normal ulnar variance and the late appearance of sclerotic borders may be observed on radiographs. Early BMO and TFCC lesions call for MRI (Figure 7B and C).

Lunotriquetral abutment
MRI may also show this ligamentous tear ( Figure 8D) and the band-shaped BMO (Figure 8E). Eventual concurrent extrinsic ligamentous lesions should be looked for, as it is questionable if this solitary lesion results in abnormal  mobility [17]. Due to chronic impaction, massive deformation may appear on radiographs ( Figure 8F).

Hamatolunar abutment
Hamatolunar abutment is related to lunate bony variants (Viegas type II). However, a posttraumatic disturbance of the carpal row alignment (Gilula) [18] may induce SAS. Radiographs reveal the deformed area with abnormal contact during ulnar deviation (Figure 9A and B). The carpal line interruption and the pathologic bone motions are obvious on mobility radiographs.

Carpal boss with abutment
Quadrangular joint traumata may result in bony carpal boss [19]. Although the restricted motion, deformations induce juxtaarticular changes (Figure 10A-C). Due to superposition, radiographs are less useful and MRI may help to solve the clinical problem.

Conclusion
A large variety of pathologies may cause SAS. This underscores the need for a thorough posttraumatic joint evaluation. Follow-up radiographs and MRI are mandatory in  the presence of clinical symptoms. Concerns about the prognosis -certainly in expert or insurance-related files -should encourage detailed assessment, as even small lesions may be very functionally disabling.

Important teaching points
Posttraumatic SAS may interfere with a large variety of normal daily activities, as the wrist is a crucial structure in the three-dimensional positioning of the hand. Some are fairly unknown and, due the complex anatomy of the wrist, a SAS is also often ignored or underappreciated.