4 minute read
High-resolution ultrasound approach to quadrangular joint in carpal boss: Everything musculoskeletal sonographer should know
High-resolution ultrasound approach to quadrangular joint in carpal boss: Everything musculoskeletal sonographer should know
Reviewer: Andrew Grant | ASA SIG: Musculoskeletal
Authors: Corvino A, Ricci V, Cocco G, Delli Pizzi A, Tafuri D, Corvino F, Nevalainen MT, Chew FS, Mespreuve M & Catalano O
Why the review was performed
A carpal boss (CB) is a rare hypertrophied bony protuberance located on the dorsal aspect of the hand at the quadrangular joint (QAJ). Symptoms of CB may include pain, swelling and restriction of hand motion. Traditionally it is imaged with plain radiographs, computerised tomography (CT) or magnetic resonance imaging (MRI). Radiographs and CT may evaluate the osseous morphology of CB but may fail to adequately image the associated soft tissue changes. MRI is costly, timeconsuming, lacks dynamic imaging and may be contraindicated in a number of patients. Ultrasound has superior spatial resolution in the near field, is low cost, and allows real-time dynamic assessment as well as contralateral comparison and Doppler imaging.
The purpose of the review is to define the pathology spectrum around and within the QAJ in CB, highlighting the role of highresolution ultrasonography (HR-US) in its assessment, with emphasis placed on normal anatomy, a description of the examination technique and the pathological finding.
What the review described
The QAJ is the dorsal four-cornered articular space of the carpometacarpal (CMC) joints between the bases of the second and third metacarpals and the trapezoid and capitate. The QAJ has a close relationship with multiple soft tissue structures including the CMC ligaments, the insertions of extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) and the tendons of extensor indicis (EI) and extensor digitorum communis (EDC) to the index finger. An accessory ossicle called an os styloideum (OS) also occurs at the QAJ. The presence of OS in the QAJ region can alter the normal biomechanics of wrist joint motion, leading to the onset of degenerative osteoarthritis and the development of an overlying ganglion or bursitis.
CB may be classified as acquired (due to trauma and/or degenerative osteophytosis), congenital (due to the OS) or mixed (caused by a combination of trauma, osteophytes and OS). On examination, the CB appears as a firm, fixed prominence at the base of the second and/or third metacarpals. It is particularly noticeable when the wrist is flexed and is tender when local pressure is applied. Clinically, it is often difficult, if not impossible, to distinguish between CB and dorsal ganglia of the wrist.
A high frequency linear or small-footprint hockey stick probe is used. Copious amounts of gel used as a stand-off can minimise artefacts in the near field. Alternatively, a stand-off pad can be utilised.
Scanning over the palpable lump will demonstrate the presence of a cystic (ganglion) or bony (CB) abnormality. If the CB is congenital, the OS can be recognised, appearing as a distinct, tiny ossicle at the QAJ (Figure 1). If acquired, local osteophytes will present as spurs originating from the dorsal aspect of bones at QAJ. In the mixed type, HR-US shows a combination of both OS and local osteophytes.
Upon establishing the diagnosis of CB, HRUS can effectively detect any concomitant soft tissue pathology including effusion, synovial thickening, ganglion cyst or bursitis, tenosynovitis, or tendinopathy of ECRB, ECRL, or EPI/EDC. It is possible to observe a snapping phenomenon caused by EI and EDC of the index finger slipping/snapping over the CB when the wrist undergoes flexion extension and ulnar-radial deviation.
Relevance to clinical practice
Given that CB clinically presents with a lump on the dorsum of the wrist, US is frequently employed as the initial imaging modality, leading to a conclusive diagnosis in most cases. The differential diagnosis of CB must be considered when no dorsal wrist ganglion is identified. HR-US is crucial in assessing the QAJ in CB and should increasingly assume a primary role compared to invasive or costlier modalities such as radiography, CT and MRI, which should be considered as second-level methods and retained for patients with an unfavourable outcome following conservative management or when surgical treatment is considered.
US is crucial in assessing the QAJ in CB and should increasingly assume a primary role compared to invasive or costlier modalities such radiography, CT and MRI
