Imaging of Carpal Instabilities

The Safety of the Volar Intraarticular Extended Window (VIEW) Approach for Intra-articular Distal Radius Fractures

BACKGROUND

A novel volar approach to intra-articular distal radius fractures has been introduced for treatment of intra-articular distal radius fractures, in which volar extrinsic ligaments are released to create a volar window into the radiocarpal joint (Volar Intraarticular Extended Window [VIEW] approach). Our purpose was to evaluate the safety of VIEW approach for treatment of intra-articular distal radius fractures.

METHODS

A retrospective chart review was performed for 13 patients with intra-articular distal radius fractures treated operatively with the VIEW surgical technique using an intra-articular window in the volar capsule to aid in reduction and fixation. Postoperative radiographs were reviewed to assess for ulnocarpal translocation by assessing lunate uncovering and radial-carpal distance.

RESULTS

Thirteen patients were treated with the VIEW approach with mean follow-up of 28 weeks (range, 7-67 weeks; SD, 18 weeks). The mean postoperative lunate uncovering was 34.6% (SD, 7.7%) and mean radial-carpal distance was 4.6 mm (SD, 1.5 mm). Postoperatively, mean intra-articular step-off was 0.9 mm (SD, 1.2 mm) and mean intra-articular gap was 1.2 mm (SD, 1.0 mm). No patients reported clinical symptoms of wrist instability.

CONCLUSIONS

Using the VIEW approach during a volar approach to intra-articular distal radius fractures is safe and does not lead to carpal instability. Surgeons can consider using the approach when direct visualization of the articular surface may be beneficial for reduction or fixation.

LEVEL OF EVIDENCE

Therapeutic IV.

One-stop-shop CT arthrography of the wrist without subject repositioning by means of gantry-free cone-beam CT

Modern cone-beam CT systems are capable of ultra-high-resolution 3D imaging in addition to conventional radiography and fluoroscopy. The combination of various imaging functions in a multi-use setup is particularly appealing for musculoskeletal interventions, such as CBCT arthrography (CBCTA). With this study, we aimed to investigate the feasibility of CBCTA of the wrist in a “one-stop-shop” approach with a gantry-free twin robotic scanner that does not require repositioning of subjects. Additionally, the image quality of CBCTA was compared to subsequent arthrograms on a high-end multidetector CT (MDCTA). Fourteen cadaveric wrists received CBCTA with four acquisition protocols. Specimens were then transferred to the CT suite for additional MDCTA. Dose indices ranged between 14.3 mGy (120 kVp/100 effective mAs; full-dose) and 1.0 mGy (70 kVp/41 effective mAs; ultra-low-dose) for MDCTA and between 17.4 mGy (80 kVp/2.5 mAs per pulse; full-dose) and 1.2 mGy (60 kVp/0.5 mAs per pulse; ultra-low-dose) for CBCTA. Subjective image quality assessment for bone, cartilage and ligamentous tissue was performed by seven radiologists. The interrater reliability was assessed by calculation of the intraclass correlation coefficient (ICC) based on a two-way random effects model. Overall image quality of most CBCTA was deemed suitable for diagnostic use in contrast to a considerable amount of non-diagnostic MDCTA examinations (38.8%). The depiction of bone, cartilage and ligaments in MDCTA with any form of dose reduction was inferior to any CBCTA scan with at least 0.6 mAs per pulse (all p < 0.001). Full-dose MDCTA and low-dose CBCTA were of equal quality for bone tissue visualization (p = 0.326), whereas CBCTA allowed for better depiction of ligaments and cartilage (both p < 0.001), despite merely one third of radiation exposure (MDCTA–14.3 mGy vs. CBCTA–4.5 mGy). Moderate to good interrater reliability was ascertained for the assessment all tissues (ICC 0.689–0.756). Overall median examination time for CBCTA was 5.4 min (4.8–7.2 min). This work demonstrates that substantial dose reduction can be achieved in CT arthrography of the wrist while maintaining diagnostic image quality by employing the cone-beam CT mode of a twin robotic X-ray system. The ability of the multi-use X-ray system to switch between fluoroscopy mode and 3D imaging allows for “one-stop-shop” CBCTA in minimal examination time without the need for repositioning.

Extrinsic and Intrinsic Ligaments of the Wrist

Carpal stability depends on the integrity of both intra-articular and intracapsular carpal ligaments. In this review, the role of the radial-sided and ulnar-sided extrinsic and intrinsic ligaments is described, as well as their advanced imaging using magnetic resonance arthrography (MRA) and contrast-enhanced magnetic resonance imaging (MRI) with three-dimensional (3D) scapholunate complex sequences and thin slices. In the last decade, the new concept of a so-called "scapholunate complex" has emerged among hand surgeons, just as the triangular ligament became known as the triangular fibrocartilage complex (TFCC).The scapholunate ligament complex comprises the intrinsic scapholunate (SL), the extrinsic palmar radiocarpal: radioscaphocapitate (RSC), long radiolunate (LRL), short radiolunate (SRL) ligaments, the extrinsic dorsal radiocarpal (DRC) ligament, the dorsal intercarpal (DIC) ligament, as well as the dorsal capsular scapholunate septum (DCSS), a more recently described anatomical structure, and the intrinsic palmar midcarpal scaphotrapeziotrapezoid (STT) ligament complex. The scapholunate (SL) ligament complex is one of the most involved in wrist injuries. Its stability depends on primary (SL ligament) and secondary (RSC, DRC, DIC, STT ligaments) stabilizers.The gold standard for carpal ligament assessment is still diagnostic arthroscopy for many hand surgeons. To avoid surgery as a diagnostic procedure, advanced MRI is needed to detect associated lesions (sprains, midsubstance tears, avulsions and chronic fibrous infiltrations) of the extrinsic, midcarpal and intrinsic wrist ligaments, which are demonstrated in this article using 3D and two-dimensional sequences with thin slices (0.4 and 2 mm thick, respectively).

Carpal Instability: I. Pathoanatomy

The pathoanatomy of carpal instability is multifactorial and usually complex. A thorough medical history and clinical examination are essential, as well as profound knowledge of the specific instability patterns. The stability of the wrist is ensured by the carpal joint surfaces, by intact intra-articular (particularly the scapholunate interosseous ligament) and intracapsular ligaments, and by crossing extensor and flexor tendons, the latter making the proximal carpal row an "intercalated segment." An important classification feature is the distinction between dissociative and nondissociative forms of carpal instability. Among others, scapholunate dissociation, lunotriquetral dissociation, midcarpal instability, and ulnar translocation are the most common entities. Early forms of instability are considered dynamic. In the natural course, static instability of the wrist and osteoarthritis will develop. This review focuses on the pathoanatomical fundamentals of the various forms of carpal instability.